全文获取类型
收费全文 | 33230篇 |
免费 | 1755篇 |
国内免费 | 148篇 |
专业分类
耳鼻咽喉 | 360篇 |
儿科学 | 736篇 |
妇产科学 | 582篇 |
基础医学 | 6295篇 |
口腔科学 | 743篇 |
临床医学 | 2631篇 |
内科学 | 6283篇 |
皮肤病学 | 855篇 |
神经病学 | 3441篇 |
特种医学 | 1424篇 |
外科学 | 4602篇 |
综合类 | 152篇 |
一般理论 | 14篇 |
预防医学 | 1670篇 |
眼科学 | 721篇 |
药学 | 2319篇 |
中国医学 | 21篇 |
肿瘤学 | 2284篇 |
出版年
2022年 | 161篇 |
2021年 | 347篇 |
2020年 | 295篇 |
2019年 | 493篇 |
2018年 | 574篇 |
2017年 | 439篇 |
2016年 | 566篇 |
2015年 | 653篇 |
2014年 | 784篇 |
2013年 | 1171篇 |
2012年 | 1643篇 |
2011年 | 1760篇 |
2010年 | 1185篇 |
2009年 | 1134篇 |
2008年 | 1891篇 |
2007年 | 1930篇 |
2006年 | 1798篇 |
2005年 | 1925篇 |
2004年 | 1804篇 |
2003年 | 1766篇 |
2002年 | 1845篇 |
2001年 | 349篇 |
2000年 | 273篇 |
1999年 | 393篇 |
1998年 | 503篇 |
1997年 | 414篇 |
1996年 | 369篇 |
1995年 | 338篇 |
1994年 | 291篇 |
1993年 | 258篇 |
1992年 | 213篇 |
1991年 | 206篇 |
1990年 | 170篇 |
1989年 | 165篇 |
1988年 | 170篇 |
1985年 | 161篇 |
1984年 | 181篇 |
1983年 | 161篇 |
1982年 | 198篇 |
1981年 | 169篇 |
1978年 | 135篇 |
1933年 | 170篇 |
1932年 | 180篇 |
1931年 | 167篇 |
1930年 | 169篇 |
1929年 | 147篇 |
1928年 | 163篇 |
1927年 | 144篇 |
1926年 | 158篇 |
1925年 | 139篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
201.
Widespread depletion of forebrain noradrenaline, produced by the intracerebral injection of 4 g of 6-hydroxydopamine into the fibres of the dorsal noradrenergic bundle, potentiated the catalepsy induced by 20 mg/kg of morphine and severely attenuated the catalepsy induced by two separate cholinergic agonists, arecoline and pilocarpine. It did not, however, affect haloperidol catalepsy at any of the four doses tested. These results suggest that cholinergic catalepsy may be critically dependent on an intact noradrenergic substrate, perhaps through cholinergic receptors located either presynaptically on noradrenergic terminals or on the cell bodies of origin in the locus coeruleus. Noradrenaline appears to play a modulatory role in morphine catalepsy, although other sites of action must also be involved. Ascending noradrenergic systems do not appear to influence haloperidol catalepsy. 相似文献
202.
Thomas L?ubli Carlo Thomas Urs Hinnen Wilhelm Hünting Hans Zeier Hans Mion 《Sozial- und Pr?ventivmedizin》1991,36(1):25-33
Zusammenfassung Der standardisierte Fragebogen zur Erfassung muskuloskeletaler Beschwerden des japanischen Komitees zum Studium arbeitsbedingter Gesundheitsstörungen im Hals-Arm-Gebiet wurde auf Deutsch übertragen und seine Reliabilität und Validität überprüft. Im Fragebogen wird anhand eines Körperschemas nach der Häufigkeit (nie/selten, gelegentlich, fast täglich) von Beschwerden (Schmerzen, Steifigkeit, Müdigkeit) in 12 Körperregionen gefragt. Der Fragebogen wurde gleichzeitig mit ärztlichen Palpationsuntersuchungen bei 644 Personen aus zwölf Berufsgruppen im Dienstleistungssektor eingesetzt. Auf Grund einer Faktoranalyse der Fragebogenresultate kann festgestellt werden, dass Beschwerden regional getrennt (nämlich im Nacken-Schultergebiet, dem Rücken und je der rechten und linken oberen Extremität) auftreten und für diese Regionen die Symptome zu Indizes zusammengefasst werden können. Diese Indizes sind reliabel (Cronbach 0.8). Mit zunehmenden Indexwerten nehmen schmerzhafte Palpationsbefunde stetig zu. Beschwerden korrelieren mit vermehrtem Medikamentenkonsum und Arztkonsultationen. Der Fragebogen stellt folglich ein valides Untersuchungsinstrument für muskuloskeletale Beschwerden am Arbeitsplatz dar.
Summary The standardized illustrated questionnaire on musculoskeletal disorders of the Japanese Committee on Occupational Cervico-brachial Disorders was translated into German. This questionnaire, composed of 37 items about the occurrence (never/seldom, occasionally, almost daily) of symptoms (pain, stiffness, fatique) in twelve body regions, was used together with medical examinations (pressure points), and further information was gathered on the consumption of analgetics and medical visits prompted by musculoskeletal symptoms. The questionnaire's reliability and validity were tested in 644 persons from twelve occupational groups within the service sector. Factoranalyses showed that symptoms can be grouped into four distinct regions of occurrence: neck/shoulder/area, back/low back, and both left and right upper extremities. Indices based on these regions are consistent (Cronbach 0.8). Palpation findings steadily increase with increasing index values. The consumption of medicaments and medical visits positively correlate with the indices. Consequently the questionnaire is judged to be a valid instrument for studying musculoskeletal disorders at the workplace.
Résumé Le questionnaire illustré et standardisé sur les symptômes musculaires et osseux du comité japonais sur la cervico-brachialgie professionelle a été traduit en allemand et sa reliabilité et validité ont été testées. Le questionnaire est composé de 37 variables sur la fréquence (jamais/rarement, par occasion, presque toujours) des symptômes (douleur, raideur, fatigue) dans douze régions du corps. Il était distribué simultanément aux examens médicaux parmi 644 personnes de douze groupes d'employés dans le secteur de service. D'autres informations concernent la fréquence de la consommation des analgésiques et des visites médicales pour des douleurs musculaires. Une analyse factorielle a montré que les symptômes peuvent être groupés en quatre régions du corps: nuque/épaules, dos et les extrémités supérieurs. Les indices sur ces régions sont consistant (Cronbach 0.8). Les douleurs provoquées par la palpation augmentent avec la valeur de l'index. La consommation des analgésiques et les consultations sont correlées avec les indices. Par conséquent, le questionnaire illustré est un instrument valable pour étudier les problèmes musculaires sur les lieux de travail.相似文献
203.
Various N--hydroxyalkyl derivatives of N-acyl amino acids and di- and tripeptides were prepared by hydrolysis or aminolysis of N-acyl 5-oxazolidinones. The stability of these derivatives was studied in aqueous solution as a function of pH. The compounds were all degraded quantitatively to their parent N-acylated amino acid or peptide and aldehyde but with vastly different rates. At pH 7.4 and 37°C the half-lives of decomposition ranged from 4 min to 1500 hr. The structural factors influencing the stability included both steric and polar effects within the acyl and N--hydroxyalkyl moieties as well as within the amino acid attached to the N--hydroxyalkylated N-acyl amino acid. Whereas the N-benzyloxycarbonyl (Z) derivatives of the dipeptides Gly-L-Leu and Gly-L-Ala were readily hydrolyzed by carboxypeptidase A, the N-hydroxymethylated compounds, i.e., Z-Gly(CH2OH)-Leu and Z-Gly(CH2OH)-Ala, were resistant to cleavage by the enzyme as revealed by their similar rates of decomposition in the presence or absence of the enzyme at pH 7.4 and 37°C. The results suggest that N--hydroxyalkylation of a peptide bond protects not only this bond but also an adjacent peptide bond against proteolytic cleavage. Since the N--hydroxyalkyl derivatives are readily bioreversible, undergoing spontaneous hydrolysis at physiological pH, this prodrug approach promises to overcome the enzymatic barrier to absorption of various peptides. 相似文献
204.
Philippe Béhé Katrin Sandmeier Hans Meves 《Pflügers Archiv : European journal of physiology》1992,422(2):120-128
The M current, I
M, a voltage-dependent non-inactivating K+ current, was recorded in NG108-15 neuroblastoma × glioma hybrid cells, using the whole-cell mode of the patch-clamp technique. We studied the effect of arachidonic acid, other fatty acids and inhibitors of the arachidonic acid metabolism. In relatively high concentrations (25–50 M) arachidonic acid first increased and later decreased the current, I
h, which holds the membrane potential at –30 mV and mainly flows through open M channels. It shifted the midpoint potential, V
o, of the relation between M conductance, g
M, and membrane potential, V, to more negative values and decreased the maximum conductance ¯g
M and the time constant
M. In smaller concentrations (5–10 M) arachidonic acid merely decreased I
h and ¯g
M with little effect on V
o and
M. Eicosatetraynoic acid and docosa-hexaenoic acid acted similarly to arachidonic acid whereas stearic acid had no effect. Of the three enzyme inhibitors studied, nordihydroguaiaretic acid acted similarly to arachidonic acid. i. e. caused a biphasic change in I
h. Indomethacin and quinacrine caused, respectively, a pure increase and a pure decrease of I
h and ¯g
M. Possible explanations are build-up of internally produced arachidonic acid, depletion of eicosanoid products or an inhibitory effect unrelated to arachidonic acid metabolism. 相似文献
205.
Hans Christian Blossey Hans Helge Bartsch Dietrich Kanne Johannes Koebberling Gerhard Arno Nagel 《Cancer chemotherapy and pharmacology》1982,8(1):77-81
Summary Oral MPA 1.5 g/day leads to plasma concentrations between 1 and 12 g/ml, with a broad intra-and interindividual variance. The plateau state is reached in between 4 and 16 days. Plasma concentrations in the plateau state are very sensitive to dose modifications. After cessation of administration, the decline in plasma levels seems to proceed in two phases, with half-times of about 20 h and 4 days. Extraction procedures reveal no benefit in discriminating between MPA and its metabolites. 相似文献
206.
Addition of [3H]-benzo(a)pyrene to the perfusion medium of isolated rat livers results in irreversible binding of radioactivity to DNA, RNA and protein. Binding to DNA accounted for about 0.1% of the total radioactivity which was bound in livers from animals treated with oil or saline and was increased by a factor of 3–5 after pretreatment of the animals with -naphthoflavone or with phenobarbital. When the inhibitiors of monooygenase activity, -naphthoflavone or metyrapone, were present in the perfusion medium, irreversible binding was reduced in livers from both -naphthoflavone- and phenobarbital-pretreated animals, irrespective of the inhibitor used.In livers from animals treated with oil or saline protein and a RNA fraction containing tightly associated protein were able to bind [3H]-benzo(a)pyrene metabolites to about the same extent but after induction by pretreatment with -naphthoflavone binding to the RNA fraction was enhanced to a much higher extent than binding to the protein fraction. Pretreatment with phenobarbital did not result in an increased irreversible binding to RNA and protein.A considerable amount of 15–25% of the total radioactivity added to the perfusion medium was excreted into the bile after treatment of the animals with the tested inducers of monooxygenase activity compared to an excretion of 3% in animals treated with oil or saline.The results indicate that nucleic acid and protein adduct formation in the liver is controlled by the action of the cytochrome P-450-dependent monooxygenases.In part subject of the doctoral thesis of Erik Klaus, Fachbereich Biologie, University of Mainz 相似文献
207.
Dana M. Hartl Stéphane Hans Jacqueline Vaissière Daniel F. Brasnu 《European archives of oto-rhino-laryngology》2003,260(4):175-182
This study was designed to determine which objective acoustic or aerodynamic parameters allowed a homogeneous group of patients with unilateral vocal fold paralysis (UVFP) to be distinguished from an age-matched and smoking-matched control group and to search for linear correlations between the objective parameters and the subjective breathiness ratings. Eight patients with recent-onset UVFP and 12 controls were prospectively studied. The acoustic parameters measured for the vowel /a/ at a comfortable frequency and intensity were: jitter, shimmer, harmonics-to-noise ratio, cepstral peak prominence, the difference between the levels of the first two harmonics and the relative energy above 6 kHz. Aerodynamic parameters included the mean flow rate during a sustained /a/ and intraoral pressure during the production of the phoneme /pi/. The long-term average spectrum was calculated for 40 s of text, and the relative average energies in four frequency bands were compared. Six judges rated a mid-/a/ sample using a five-parameter scale with four levels of severity. Nonparametric statistical analysis revealed significant differences ( P<.05) between the UVFP group and the control group for 14 of the 19 parameters studied. Correlations between the objective parameters and perceived breathiness differed in the two groups. Correlations were not always as expected as based on previous literature reports. These measurements provided an objective qualification of voice in patients with UVFP and successfully distinguished them from the normal controls. The objective acoustic and aerodynamic measurements had generally low linear correlations with breathiness ratings in the control group. Higher correlations were seen in the UVFP group, in which breathiness was best correlated with airflow measurements. 相似文献
208.
Yves Claustre Danielle De Peretti Philippe Brun Christiane Gueudet Nathalie Allouard Richard Alonso Jo?lle Lourdelet André Oblin Gabrielle Damoiseau Dominique Fran?on Marie-Fran?oise Suaud-Chagny Régis Steinberg Mireille Sevrin Hans Schoemaker Pascal George Philippe Soubrié Bernard Scatton 《Neuropsychopharmacology》2003,28(12):2064-2076
SSR181507 ((3-exo)-8-benzoyl-N-[[(2S)7-chloro-2,3-dihydro-1,4-benzodioxin-1-yl]methyl]-8-azabicyclo[3.2.1]octane-3-methanamine monohydrochloride) is a novel tropanemethanamine benzodioxane derivative that possesses high and selective affinities for D2-like and 5-HT(1A) receptors (K(I)=0.8, 0.2, and 0.2 nM for human D(2), D(3), and 5-HT(1A), respectively). In vivo, SSR181507 inhibited [(3)H]raclopride binding to D(2) receptors in the rat (ID(50)=0.9 and 1 mg/kg, i.p. in limbic system and striatum, respectively). It displayed D(2) antagonist and 5-HT(1A) agonist properties in the same concentration range in vitro (IC(50)=5.3 nM and EC(50)=2.3 nM, respectively, in the GTPgammaS model) and in the same dose range in vivo (ED(50)=1.6 and 0.7 mg/kg, i.p. on striatal DA and 5-HT synthesis, respectively, and 0.03-0.3 mg/kg, i.v. on dorsal raphe nucleus firing rate). It selectively enhanced Fos immunoreactivity in mesocorticolimbic areas as compared to the striatum. This regional selectivity was confirmed in electrophysiological studies where SSR181507, given acutely (0.1-3 mg/kg, i.p.) or chronically (3 mg/kg, i.p., o.d., 22 days), increased or decreased, respectively, the number of spontaneous active DA cells in the ventral tegmental area, but not in the substantia nigra. Moreover, SSR181507 increased both basal and phasic DA efflux (as assessed by microdialysis and electrochemistry) in the medial prefrontal cortex and nucleus accumbens, but not in the striatum. This study shows that the combination of D(2) receptor antagonism and 5-HT(1A) agonism, in the same dose range, confers on SSR181507 a unique neurochemical and electrophysiological profile and suggests the potential of this compound for the treatment of the main dimensions of schizophrenia. 相似文献
209.
Absorption/metabolism of sulforaphane and quercetin, and regulation of phase II enzymes, in human jejunum in vivo. 总被引:2,自引:0,他引:2
Niclas Petri Christer Tannergren Birgit Holst Fred A Mellon Yongping Bao Geoff W Plumb Jim Bacon Karen A O'Leary Paul A Kroon Lars Knutson Patrik Forsell Thomas Eriksson Hans Lennernas Gary Williamson 《Drug metabolism and disposition》2003,31(6):805-813
For the first time the human intestinal effective permeability, estimated from the luminal disappearance and intestinal metabolism of phytochemicals, sulforaphane and quercetin-3,4'-glucoside, as well as the simultaneous changes in gene expression in vivo in enterocytes, has been studied in the human jejunum in vivo (Loc-I-Gut). Both compounds as components of an onion and broccoli extract could readily permeate the enterocytes in the perfused jejunal segment. At the physiologically relevant, dietary concentration tested, the average effective jejunal permeability (Peff) and percentage absorbed (+/- S.D.) were 18.7 +/- 12.6 x 10-4 cm/s and 74 +/- 29% for sulforaphane and 8.9 +/- 7.1 x 10-4 cm/s and 60 +/- 31% for quercetin-3,4'-diglucoside, respectively. Furthermore, a proportion of each compound was conjugated and excreted back into the lumen as sulforaphane-glutathione and quercetin-3'-glucuronide. The capacity of the isolated segment to deconjugate quercetin from quercetin-3,4'-diglucoside during the perfusion was much higher than the beta-glucosidase activity of the preperfusion jejunal contents, indicating that the majority (79-100%) of the beta-glucosidase capacity derives from the enterocytes in situ. Simultaneously, we determined short-term changes in gene expression in exfoliated enterocytes, which showed 2.0 +/- 0.4-fold induction of glutathione transferase A1 (GSTA1) mRNA (p < 0.002) and 2.4 +/- 1.2-fold induction of UDP-glucuronosyl transferase 1A1 (UGT1A1) mRNA (p < 0.02). The changes in gene expression were also seen in differentiated Caco-2 cells, where sulforaphane was responsible for induction of GSTA1 and quercetin for induction of UGT1A1. These results show that food components have the potential to modify drug metabolism in the human enterocyte in vivo very rapidly. 相似文献
210.
Multivariate Analysis of Risk Factors for Postoperative Complications in Benign Goiter Surgery: Prospective Multicenter Study in Germany 总被引:12,自引:5,他引:7
Thomusch O Machens A Sekulla C Ukkat J Lippert H Gastinger I Dralle H 《World journal of surgery》2000,24(11):1335-1341
Risk factors for postoperative complications of benign goiter surgery have not been investigated systematically. To this
end, a prospective multicenter study (January 1 through December 31, 1998) was conducted involving 7266 patients with surgery
for benign goiter from 45 East German hospitals. High-volume providers (>150 operations per year) performed 69% (5042/7266),
intermediate-volume providers 27% (50–150), and low-volume providers 4% (258/7266) of operations. Among the hospital groups,
the pattern of thyroid disease did not vary significantly, but there was a trend that small-volume providers tended to perform
more operations for uninodular goiter and high-volume providers treated more patients with Graves' disease and recurrent goiter.
Extent of resection (p < 0.0001) and remnant size (multinodular goiter and recurrent goiter, p < 0.001), differed significantly, with total thyroidectomy being performed more often in hospitals with more than 150 operations
compared to hospitals with an operative volume of less than 150 procedures per year. Despite the larger extent of resection
and smaller remnant size, rates of recurrent laryngeal nerve (RLN) palsy or hypoparathyroidism were not increased. When the
logistic regression analyses were fitted to evaluate the impact of risk factors on transient and permanent RLN palsy and hypoparathyroidism,
larger extent of resection [relative risk (RR) 1.5–2.1] and recurrent goiter (RR 1.8–3.4) consistently evolved as independent
risk factors. With hypoparathyroidism, additional significant factors included patient gender (RR 2.1–2.4), hospital operative
volume (RR 0.8–1.5), and Graves' disease (RR 2.8). Unlike parathyroid gland identification during hypoparathyroidism, RLN
identification (RR 1.6) significantly (p= 0.01) reduced permanent RLN palsy rates. The multivariate analyses clearly confirmed the pivotal role of routine RLN identification,
independent of the extent of the thyroid resection. These findings might help hospitals with lower operative volumes to identify
patients at increased risk whom they might consider for specialist care. 相似文献