全文获取类型
收费全文 | 7465篇 |
免费 | 328篇 |
国内免费 | 52篇 |
专业分类
耳鼻咽喉 | 42篇 |
儿科学 | 186篇 |
妇产科学 | 29篇 |
基础医学 | 1263篇 |
口腔科学 | 93篇 |
临床医学 | 515篇 |
内科学 | 1548篇 |
皮肤病学 | 395篇 |
神经病学 | 719篇 |
特种医学 | 352篇 |
外科学 | 1003篇 |
综合类 | 31篇 |
一般理论 | 4篇 |
预防医学 | 302篇 |
眼科学 | 146篇 |
药学 | 599篇 |
中国医学 | 33篇 |
肿瘤学 | 585篇 |
出版年
2022年 | 36篇 |
2021年 | 50篇 |
2020年 | 46篇 |
2019年 | 76篇 |
2018年 | 100篇 |
2017年 | 81篇 |
2016年 | 93篇 |
2015年 | 130篇 |
2014年 | 174篇 |
2013年 | 245篇 |
2012年 | 364篇 |
2011年 | 387篇 |
2010年 | 233篇 |
2009年 | 262篇 |
2008年 | 439篇 |
2007年 | 532篇 |
2006年 | 490篇 |
2005年 | 497篇 |
2004年 | 454篇 |
2003年 | 487篇 |
2002年 | 454篇 |
2001年 | 95篇 |
2000年 | 87篇 |
1999年 | 131篇 |
1998年 | 130篇 |
1997年 | 127篇 |
1996年 | 127篇 |
1995年 | 81篇 |
1994年 | 91篇 |
1993年 | 83篇 |
1992年 | 60篇 |
1991年 | 48篇 |
1990年 | 48篇 |
1989年 | 38篇 |
1988年 | 53篇 |
1987年 | 42篇 |
1986年 | 28篇 |
1985年 | 26篇 |
1984年 | 46篇 |
1983年 | 38篇 |
1982年 | 54篇 |
1981年 | 37篇 |
1980年 | 39篇 |
1979年 | 32篇 |
1978年 | 33篇 |
1977年 | 29篇 |
1976年 | 35篇 |
1974年 | 32篇 |
1973年 | 26篇 |
1954年 | 28篇 |
排序方式: 共有7845条查询结果,搜索用时 15 毫秒
41.
Bernhard J. Connemann Heidrun Busche Jürgen Kreusch Helmut H. Wolff 《Skin research and technology》1996,2(1):40-48
Background/aims: Quantitative measurement of skin roughness has proved to be a valuable tool in the efficacy-control of external applications, but it suffers from not yielding easily comparable results. The most important sources of inter-observer variability are high-pass filters used to separate roughness and waviness, and low-pass filters which result from the finite resolution of the instrument or from the finite sampling interval of digital measurement. In the present study, the effects of high-pass filters and sampling intervals on the roughness measured were investigated. Methods: Dynamically focusing optical profilometry was used to measure the surfaces of negative replicas of healthy human skin. High-pass cut-off wavelengths and sampling intervals were varied systematically. Results/conclusions: Virtually unbiased estimates for the roughness parameters K, Sk, Rq, and Ra can be obtained using sampling intervals of 40 or even 80 μm. Regarding these roughness parameters, it is far better to do more scans than to shorten the sampling interval. The roughness parameters Rz, Rp, Rt, Rpm, Rmax, Pt, on the other hand are very sensitive to the influence of the sampling interval; to achieve satisfying estimates, the sampling interval should be no longer than 2 to 5 urn; as an important parameter’of the measurement, it is worthy of remark and should always be indicated. The way the mean square roughness Rq depends on the cut-off wavelength is not well described by the Sayles-Thomas-relation Rq~λc0.5. If the power-spectrum |h*(v)|2 approximates sufficiently to a power law, |h*(v)|2~vδ, a better estimate is given by Rq~λcγ with γ=-(δ+1)/2. In many cases, γ=1 or Rq~λc will suffice. 相似文献
42.
Helmut Schulte und Gerd Assmann 《Sozial- und Pr?ventivmedizin》1988,33(1):32-36
Zusammenfassung Die «Prospektive Cardiovascular Münster» (PROCAM)-Studie wird seit 1979 bei Betriebsangehörigen im Raum Westfalen durchgeführt. Bis zum Ende der Rekrutierungsphase (Jahresende 1985) haben 20060 Personen beiderlei Geschlechts von 17 bis 65 Jahren an der Untersuchung teilgenommen. Die Untersuchung zu Beginn der Beobachtungszeit umfasst eine Anamnese nach standardisiertem Fragebogen, die Messung von Blutdruck und anthropometrischen Grössen, ein EKG sowie eine Blutentnahme nach zwölfstündiger Nahrungskarenz.Bei einer Längsschnittauswertung von Männern im Alter von 40 bis 65 Jahren, die zu Beginn noch keinen Herzinfarkt oder Schlaganfall erlitten hatten und einheitlich vier Jahre nachbeobachtet wurden, traten 73 Herzinfarkte oder koronare Todesfälle innerhalb des Beobachtungszeitraumes auf, während 2681 Probanden ohne Herzinfarkt oder Schlaganfall den Zeitraum überlebten.Durch eine Hyper/Dyslipoproteinämie (Cholesterin > = 300 mg/dl oder Cholesterin und/oder Triglyzeride > = 200 mg/dl und gleichzeitig HDL-Cholesterin unter 35 mg/dl) sowie einer multiplen logistischen Funktion unter Berücksichtigung der Parameter Alter, HDL-Cholesterin, Cholesterin, systolischer Blutdruck sowie der ja-nein Merkmale Zigarettenrauchen, Diabetes melliutus, Herzinfarkt in der Familie und Angina pectoris gelang es, jeweils ein Risikokollektiv abzugrenzen, das bei einer Prävalenz von unter 20% über zwei Drittel aller Inzidenzen umfasste. Als bester prädiktiver Einzelparameter erwies sich das HDL-Cholesterin.
Results of the Prospective Cardiovascular Münster (PROCAM) study
Summary In the Prospective Cardiovascular Münster(PROCAM) study since 1979 employees have been examined for cardiovascular risk factors and held under observation for the onset of clinically significant signs of atherosclerosis (myocardial infarction, stroke, coronary death). Until the end of recruitment (end of 1985) 20060 male and female employees aged 17–65 from 52 industrial companies in Westfalia have participated. The voluntary examination at the start of the observation period includes a standardised questionnaire, a physical examination, blood pressure measurements and an ECG. Blood samples are taken after an overnight fast.The data presented here describe the longitudinal evaluation of initially healthy men aged 40 to 65 who had suffered no myocardial infarction or stroke before the examination. In an uniform follow-up period of four years 73 myocardial infarctions and coronary deaths were observed while 2681 men had survived without myocardial infarction or stroke.By far the best single parameter for establishing a risk group was HDL cholesterol. Using the characteristic hyper/dyslipoproteinemia which means cholesterol > = 300mg/dl or HDL cholesterol < 35mg/dl combined with cholesterol > = 200mg/dl and/or triglyceride > = 200 mg/dl or a multiple logistic function including age. cholesterol, HDL cholesterol, systolic blood pressure, cigarette smoking, diabetes mellitus, angina pectoris and a family history of myocardial infarction patients at high risk for coronary heart disease could be identified. More than two thirds of new events happened in each of these high risk subgroups, which comprise less than 20 percent of men under consideration each.
Résultats de l'étude prospective de Münster (PROCAM)
Résumé Dans cette étude, les employés de différentes entreprises de Westphalie ont été examinés: environ 20000 personnes des deux sexes, âgées de 17 à 65 ans ont été recrutées pour cette étude (jusqu'à la fin de 1985). L'observation porte sur une anamnèse standardisée, sur la mesure de la pression sanguine et de différentes valeurs anthropométriques, un ECG et un examen sanguin suivant 12 heures de jeûne. Les données présentées ici concernent l'évaluation de la cohorte des hommes en bonne santé, âgés de 40 à 65 ans, qui n'avaient eu aucun accident cardiovasculaire avant le premier examen. Durant une période de suivi uniforme de 4 ans, 73 infarctus ou décès ont été observés, alors que 2681 hommes ont survécu. Le meilleur paramètre prédicteur pour établir un groupe à risque est, de loin, le cholestérol HDL. En utilisant les caractéristiques de l'hyper/ dyslipoprotéinémie (cholestérol > 300 mg/dl ou cholestérol HDL < 35 mg/dl, combiné avec un cholestérol > 200 mg/dl ou/et des triglycérides > 200 mg/dl) et une fonction de régression logistique multiple prenant en compte l'âge, le cholestérol HDL, le cholestérol, la pression systolique, le tabagisme, le diabète sucré, l'anamnèse familiale de coronaropathies, il est possible de caractériser un groupe à risque élevé: deux tiers des événements cardiovasculaires surviennent dans ce groupe, alors qu'ils ne concernent que 20% de la population masculine observés.相似文献
43.
Enhanced metabolic activation of chemical hepatocarcinogens in woodchucks infected with hepatitis B virus 总被引:2,自引:0,他引:2
De Flora Silvio; Heitanen Eino; Bartsch Helmut; Camoirano Anna; Izzotti Alberto; Bagnazco Maria; Millman Irving 《Carcinogenesis》1989,10(6):1099-1106
The metabolism of chemical carcinogens was investigated in liverpreparations from 28 captive woodchucks (Marmotamonax). Of these,23 were naturally infected with the wood-chuck hepatitis virus(WHV), and eight also had primary hepatocellular carcinoma (PHC).Twenty-nine parameters were investigated in liver subcelhilarfractions, including cross-reactivity with HBsAg, and biochemicalparameters, such as -glutamyl transpeptidase, cytochrome P-450and mirosomal monooxygenases (aryl hydrocarbon hydroxylase,ethodycoumarin and ethoxyresorufin deethylases, amino-pyrineand dimethylnitrosamine demethylases, and testosterone 7-and16ß- and 6ß-hydroxylases), uridine 5'-diphos-phoglucuronosyltransferase, GSH and related enzymes (peroxidase, reductaseand S-transferase), as well as other cytosolic enzyme activities(glucose 6-phosphate and 6-phosphogluconate dehydrogenases,NADPH- and NADH-dependent diaphorases, and DT diaphorase). Inaddition, liver preparations were used in order to quantifythe metabolic activation into bacterial mutagens of five procarcinogens(aflatoxin B1, the pyrolysis products Trp-P-2 and MelQ, 2-aminofluoreneand dimethylnitrosamine) and the decrease of potency of threedirect-acting mutagens (sodium di-chromate, ICR 191 and 4-nitroquinoline1-oxide). WHV infection produced a significant stimulation ofcarcinogen metabolism, as shown by the simultaneous change indetoxification parameters (GSH depletion) and activation indices(enhancement of microsomal monooxygenases and of pro-carcinogenactivation into mutagenic metabolites). There were no significantdifferences between WHV-positive samples from animals, withoutPHC and the noncancerous tissue of PHC-bearing animals, whereasa decrease of both activation and detoxification indices wasrecorded in the turmorous tissue. There was a considerable interindividualvariability among WHV carriers, which was tentatively ascribedto genetic factors. Pregnancy was the only known factor influencingthe results in WHV carriers. However, even by excluding pregnantanimals, the effects on carcinogen metabolism produced by WHVinfection were still statistically significant. These results,together with previous data obtained in humans, revealed thatmetabolic factors may play a role in the synergism between viralhepatitis and chemical hepato-carcinogens in the etiopathogenesisof PHC. 相似文献
44.
Localization of SNARE proteins and secretory organelle proteins in astrocytes in vitro and in situ 总被引:1,自引:0,他引:1
Wilhelm A Volknandt W Langer D Nolte C Kettenmann H Zimmermann H 《Neuroscience research》2004,48(3):249-257
Astrocytes are capable of regulated release of messenger molecules. Astrocytes cultured from new born rodent brain express a variety of classical presynaptic proteins. We investigated the question whether the capability to express synaptic proteins in culture was a feature only of immature astrocytes, and whether these proteins were also expressed by astrocytes in situ. Experiments were performed with transgenic mice expressing the enhanced green fluorescent protein under the control of the human glial fibrillary acidic protein promoter. Using double fluorescence and astrocytes cultured from 1 to 16 day-old animals we show that the astrocytic expression of synaptic proteins in culture is invariant of the age of donor animals. Culturing can induce the astrocytic expression of specific synaptic proteins such as SV2, synaptophysin and SNAP-25. Astrocytes in brain sections of 1-16 day-old animals revealed a punctuate immunofluorescence for secretory carrier membrane protein (SCAMP), SNAP-23, synaptobrevin II, and cellubrevin, to a minor extent for SNAP-25 and synaptophysin, and none for SV2. Our results demonstrate that cultured astrocytes express synaptic proteins not present in situ. Nevertheless, astrocytic organelles in situ are equipped with molecules that could be involved in regulated exocytosis of messenger substances. 相似文献
45.
Ghannadan M Wimazal F Simonitsch I Sperr WR Mayerhofer M Sillaber C Hauswirth AW Gadner H Chott A Horny HP Lechner K Valent P 《American journal of clinical pathology》2003,119(5):663-671
We studied vascular endothelial growth factor (VEGF) expression in bone marrow sections obtained from 3 healthy donors and 41 patients with acute myeloid leukemia (AML) of various French-American-British (FAB) subtypes by immunohistochemical analysis using an anti-VEGF antibody. In normal bone marrow, the anti-VEGF antibody reacted with myeloid progenitor cells and megakaryocytes but not with erythroid cells or mature granulocytic cells. High levels of VEGF were found in the bone marrow in patients with AML-M1, -M2, -M3, -M4, -M4Eo, and -M5. In these leukemias, the vast majority of myeloblasts (> 90%) expressed VEGF. By contrast, in AML-M0, the percentage of VEGF-positive blasts was lower in most cases (median, 42%), and if at all detectable, these blast cells contained only trace amounts of VEGF. In AML-M3 and -M4Eo, maturing granulocytes failed to express VEGF similar to granulocytes in normal bone marrow. In AML-M6, myeloblasts exhibited VEGF, whereas erythroid cells did not. In AML-M7, blast cells and megakaryocytes were identified as major sources of VEGF. In summary, VEGF expression in the bone marrow is restricted to certain stages of differentiation and maturation of myeloid cells and correlates with the FAB category. 相似文献
46.
Helmut Hinghofer-Szalkay Thomas Kenner Willibald Estelberger 《Pflügers Archiv : European journal of physiology》1976,364(2):157-160
Summary The spontaneous contractions of segments of rat portal veins have been examined in vitro under isotonic and isometric conditions. The power density spectra of recorded time series lasting 10–60 min were calculated. The spectra usually consist of harmonic frequency components. Only during shorter periods of analysis (10 min time series) we sometimes found additional non-harmonic components. All frequency components are proportionally shifted by changes of the bath temperature according to an average Q10 of 2.0. Increase of the load decreases the frequency of the contractions.The results of the spectral analysis, indicating a preponderance of a single source of periodicity, were supported by direct evidence of a pacemaker region. By recording contractions after systematic dissections of the portal vein segment, we found that spontaneous activity is generated at the central end of the segment.This work was supported by the Austrian Research Fund 相似文献
47.
Comparison of broth microdilution,E Test,and agar dilution methods for antibiotic susceptibility testing of Campylobacter jejuni and Campylobacter coli
下载免费PDF全文
![点击此处可从《Journal of clinical microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A standardized broth microdilution method was compared to the E test and an agar dilution method for the antimicrobial susceptibility testing of Campylobacter jejuni and C. coli isolates. A group of 47 human clinical isolates, 37 isolates from retail poultry, and 29 isolates from living turkeys (total, 113 isolates) was included in the study. These encompassed 92 C. jejuni and 21 C. coli strains. The MICs of six antimicrobial agents were determined by the broth microdilution and E test methods, and the strains of human origin were additionally tested by the agar dilution method. In general, broth microdilution MICs agreed within 1 log(2) MIC increment with 90.0% of E test results and 78.7% of agar dilution test results. The agar dilution method gave much lower gentamicin MICs than the broth microdilution method, but the data were significantly (P < 0.01) correlated and there was 100% agreement in the sensitivities and specificities in the comparison of the tests. The broth microdilution method had the highest sensitivity for analysis of the susceptibilities of Campylobacter to nalidixic acid and trimethoprim-sulfamethoxazole. The MICs of ciprofloxacin and erythromycin complied numerically by all three methods. The classification of the results and the correlation of the data demonstrated a high degree of agreement. All methods were equally suitable for the testing of the sensitivity of Campylobacter to tetracycline. Thus, the broth microdilution method appears to be an easy and reliable method for determination of the MICs of antibiotics for C. jejuni and C. coli, and it may offer an interesting alternative to MIC determination by the agar dilution technique or the E test. 相似文献
48.
How many lymph nodes are necessary to stage early and advanced adenocarcinoma of the sigmoid colon and upper rectum? 总被引:5,自引:0,他引:5
Leibl S Tsybrovskyy O Denk H 《Virchows Archiv : an international journal of pathology》2003,443(2):133-138
The lymph-node yields in specimens resected for colorectal adenocarcinoma show considerable variations, raising the question whether the minimum lymph-node number recommended by the UICC (International Union Against Cancer) for pN0 classification represents an appropriate quality standard for specimen work-up. The number of pericolic lymph nodes recovered from 568 archival surgical colorectal carcinoma specimens located in the sigmoid or upper rectum showed a highly statistically significant correlation with both the pT category and the presence of metastases (P<0.0005). The median lymph-node yield in standardized (i.e., resembling in size surgically removed cancer specimens) tumor-free specimens obtained during autopsies was 13 lymph nodes, compared with 20.5 when diverticula were present and more than 30 in specimens with chronic inflammation or from patients with systemic infections. In 48 pT2 and pT3 carcinoma specimens prospectively dissected in the same way, median numbers of 18 (pT2) and 23 (pT3) lymph nodes were detected (range between 8 and 39 nodes). The lymph-node numbers recommended in previous studies and by the UICC often seem to be too low to declare a specimen free of metastases. Although the great variation in lymph-node counts requires the recovery of all lymph nodes for pN0 classification, recommendations considering the pT status and additional factors like diverticula and inflammatory changes can be useful as a quality standard for specimen work up. 相似文献
49.
50.
Decreased virulence of a pneumolysin-deficient strain of Streptococcus pneumoniae in murine meningitis 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《Infection and immunity》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Wellmer A Zysk G Gerber J Kunst T Von Mering M Bunkowski S Eiffert H Nau R 《Infection and immunity》2002,70(11):6504-6508
Pneumolysin, neuraminidases A and B, and hyaluronidase are virulence factors of Streptococcus pneumoniae that appear to be involved in the pathogenesis of meningitis. In a murine model of meningitis after intracerebral infection using mutants of S. pneumoniae D39, only mice infected with a pneumolysin-deficient strain were healthier at 32 and 36 h, had lower bacterial titers in blood at 36 h, and survived longer than the D39 parent strain. Cerebellar and spleen bacterial titers, meningeal inflammation, and neuronal damage scores remained uninfluenced by the lack of any of the virulence factors. 相似文献