全文获取类型
收费全文 | 386254篇 |
免费 | 19979篇 |
国内免费 | 881篇 |
专业分类
耳鼻咽喉 | 4984篇 |
儿科学 | 12215篇 |
妇产科学 | 8032篇 |
基础医学 | 54363篇 |
口腔科学 | 11772篇 |
临床医学 | 29820篇 |
内科学 | 85186篇 |
皮肤病学 | 10130篇 |
神经病学 | 33631篇 |
特种医学 | 12241篇 |
外国民族医学 | 125篇 |
外科学 | 47761篇 |
综合类 | 2375篇 |
现状与发展 | 1篇 |
一般理论 | 118篇 |
预防医学 | 37117篇 |
眼科学 | 7589篇 |
药学 | 25772篇 |
2篇 | |
中国医学 | 1308篇 |
肿瘤学 | 22572篇 |
出版年
2023年 | 1978篇 |
2022年 | 2706篇 |
2021年 | 6724篇 |
2020年 | 4255篇 |
2019年 | 6915篇 |
2018年 | 11377篇 |
2017年 | 7974篇 |
2016年 | 7747篇 |
2015年 | 8791篇 |
2014年 | 10461篇 |
2013年 | 15186篇 |
2012年 | 24919篇 |
2011年 | 25186篇 |
2010年 | 12798篇 |
2009年 | 10541篇 |
2008年 | 20857篇 |
2007年 | 22418篇 |
2006年 | 20741篇 |
2005年 | 21028篇 |
2004年 | 19779篇 |
2003年 | 18109篇 |
2002年 | 15750篇 |
2001年 | 10725篇 |
2000年 | 10803篇 |
1999年 | 9601篇 |
1998年 | 2503篇 |
1997年 | 2142篇 |
1996年 | 2085篇 |
1995年 | 1808篇 |
1994年 | 1729篇 |
1993年 | 1559篇 |
1992年 | 5760篇 |
1991年 | 5369篇 |
1990年 | 5020篇 |
1989年 | 4775篇 |
1988年 | 4463篇 |
1987年 | 4104篇 |
1986年 | 3905篇 |
1985年 | 3615篇 |
1984年 | 2640篇 |
1983年 | 2182篇 |
1979年 | 2109篇 |
1978年 | 1432篇 |
1975年 | 1339篇 |
1974年 | 1526篇 |
1973年 | 1539篇 |
1972年 | 1391篇 |
1971年 | 1337篇 |
1970年 | 1328篇 |
1969年 | 1351篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
The ontogeny of type I and type II benzodiazepine binding sites was studied in mouse cerebellum by displacement of [3H]flunitrazepam binding by zolpidem, a ligand specific for the type I sites. Type I binding sites predominate throughout development and in the adult while type II sites account for 25% of total cerebellar benzodiazepine binding sites at birth and, during development, decrease to 10% or less in the adult. On a per cerebellum basis type II sites increase during the first postnatal week and then remain at a steady level while type I sites increase until adulthood. These results may indicate a specific localization of the type II sites (and of the corresponding alpha-protein subunits in the GABA/benzodiazepine receptor complex) in structures already present at birth and developing during a short early postnatal period. The affinity of zolpidem for its high affinity (type I) binding sites increases during cerebellar ontogeny, this increase possibly indicates an epigenetic (post-translational) 'maturation' process of the corresponding receptor molecule. Hill numbers indicate the existence of an additional binding site heterogeneity greater during development but still present in the adult; probably this is to be related to the simultaneous presence of different 'maturation' stages during development and with a certain variety of the final products. 相似文献
72.
M Lodén 《Acta pharmacologica et toxicologica》1986,58(5):382-389
The permeability of human skin to benzene, ethylene glycol, formaldehyde, and n-hexane was studied using excised skin in a flow-through diffusion cell. The rate of resorption was determined by measuring the amount of substance found in the receptor fluid beneath the skin at steady-state. The rates of resorption (microgram X cm-2 X hr-1) were: benzene 99. ethylene glycol 118, formaldehyde from a concentrated solution of formalin 319, formaldehyde from a solution of 10% formalin in phosphate buffer 16.7, and n-hexane 0.83. The amount of substance in the skin at steady-state and after 0.5 hr of exposure was also determined. For all substances, the sum of the amount in the receptor medium and in the skin at steady-state, were larger than the amount obtained by multiplying the resorption rate by the time of exposure. For benzene, ethylene glycol and n-hexane the amount absorbed during the first half-hour of exposure was considerable larger than the amount resorbed during a same unit of time at steady-state. These data call attention to the fact that the absorption rate is higher before steady state is attained. 相似文献
73.
S J Graafsma L J van Tits P van Heijst J Reyenga J F Rodrigues de Miranda T Thien 《Journal of cardiovascular pharmacology》1989,14(4):598-602
The effect of handgrip (HG) isometric exercise on plasma catecholamines, alpha 2-adrenoceptors on platelets and beta 2-adrenoceptors on lymphocytes was studied in normotensive subjects (NT) and essential hypertensive subjects (HT). Whereas systolic blood pressure (SBP) increases were similar in NT and HT subjects, diastolic blood pressure (DBP) and heart rate (HR) increased more in the former group. Baseline values and changes in plasma epinephrine (E) and norepinephrine (NE) did not differ between both groups. No differences were apparent in alpha 2-adrenoceptor density and affinity between NT and HT subjects before or after the test. HG isometric exercise induced a similar increase in beta 2-adrenoceptors on lymphocytes of 22 +/- 7 and 13 +/- 5% in NT and HT subjects, respectively. Affinity to the beta 2-adrenoceptors under baseline conditions was somewhat lower in HT (8.1 +/- 0.4 pM) than in NT subjects (6.5 +/- 0.5 pM), and this difference persisted during the test. Our results indicate that there are no differences in alpha 2- and beta 2-adrenoceptor densities either at baseline conditions or after HG isometric exercise between NT and HT subjects. Small differences noted in affinity to the beta 2-adrenoceptors require further investigation. 相似文献
74.
M. D. Taylor M. L. de Ceballos S. Rose P. N. Chong P. Jenner C. D. Marsden 《Journal of neural transmission (Vienna, Austria : 1996)》1991,3(2):99-108
Summary Aged common marmosets were treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP; 0.5–2.0 mg/kg/week i.p.) for 16 or 24 weeks, observed for a total of 30 weeks and then killed for measurement of biochemical pramaters in basal ganglia. The MPTP treatment induced a marked depletion in dopamine, 3,4-dihydroxyphenylacetic acid and homovanillic acid levels in the caudate nucleus and putamen. In contrast, the concentrations of five neuropeptides: [Met5]-enkephalin, [Leu5]-enkephalin, cholecystokinin, substance P and neurotensin as measured by a combined HPLC/RIA method, remained unaltered in all basal ganglia regions examined. Enkephalin precursor levels, as reflected by cryptic [Met5]-enkephalin content, were increased in the putamen, but not in the caudate nucleus, as a consequence of MPTP administration. Cryptic [Leu5]-enkephalin content remained unchanged in the striatum of MPTP treated marmosets. Overall, these results suggest an increase in striatal [Met5]-enkephalin release following chronic MPTP treatment of aged marmosets. However, the chronic treatment of aged marmosets with MPTP does not reproduce the neuropeptide alterations characteristic of Parkinson's disease. 相似文献
75.
P A Rittenhouse E A Bakkum L D Van de Kar 《The Journal of pharmacology and experimental therapeutics》1991,259(1):58-65
DOI [(+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane HCI] is a serotonin (5-HT1C/5-HT2) agonist, with potent cardiovascular effects. The purpose of the present studies was to determine the identity and location of the 5-HT receptor subtype(s) mediating the renin and blood pressure responses to DOI. Injection (i.p.) of DOI to conscious male rats elevated plasma renin activity in a dose-dependent manner. The 5-HT1C/5-HT2 antagonist ritanserin completely blocked the DOI-induced increase in plasma renin activity. In order to distinguish the 5-HT2- from the 5-HT1C- mediated effect of DOI, spiperone was administered before DOI. Low doses of spiperone (0.01 and 0.1 mg/kg, s.c.) significantly reduced the renin response to DOI. Because spiperone has a higher affinity for 5-HT2 than 5-HT1C receptors, these data suggest that DOI stimulates renin secretion through 5-HT2 receptors. To separate central from peripheral 5-HT receptors, we injected DOI into rats pretreated with saline or xylamidine, a 5-HT2 antagonist which does not cross the blood-brain barrier. Xylamidine produced a shift to the right and suppression of the maximal effect of DOI on plasma renin activity, suggesting a role for peripheral 5-HT2 receptors in the effect of DOI. On the other hand, i.c.v. administration of DOI, using doses lower than the peripherally effective doses, caused a significant elevation of plasma renin activity at 200 micrograms/kg. These experiments suggest that DOI's elevation of plasma renin activity has both peripheral and central sites of action.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
76.
Effect of oxygen withdrawal on active and passive electrical properties of arterially perfused rabbit ventricular muscle 总被引:1,自引:0,他引:1
Oxygen withdrawal from myocardial cells leads to changes of the transmembrane action potential (mainly action potential shortening), to cellular uncoupling, and to changes of vascular permeability. This study was aimed at the simultaneous measurement of electrical activity and passive electrical properties (extracellular and intracellular longitudinal resistance) in arterially perfused rabbit papillary muscles under different conditions of changed oxygen supply. These included 1) complete anoxia (erythrocyte-free perfusate), 2) hypoxia (PO2 between 23-28 mm Hg, erythrocytes present) in the presence and absence of glucose, and 3) normoxia with erythrocyte-free perfusate. Similarly to myocardial ischemia, rapid cellular uncoupling occurred only after an initial stable period of approximately 17 minutes, and it required complete anoxia. The marked shortening of the action potential developed before cellular uncoupling. In six out of eight experiments, the fibers were inexcitable when uncoupling started. In severe hypoxia, no significant change of internal longitudinal resistance was observed over 35-40 minutes. The time course of the extracellular longitudinal resistance was different from the change in intracellular resistance: A marked decrease occurred almost immediately after the onset of oxygen withdrawal. This decrease was followed by a small increase in conduction velocity, which was most likely due to a change in the interstitial compartment (edema). It was observed during anoxic as well as during hypoxic perfusion. We conclude that 1) cellular uncoupling in arterially perfused tissue requires almost complete oxygen lack and occurs with a delay of more than 10 minutes, 2) marked action potential shortening precedes uncoupling, and therefore can not simply be attributed to an increase in free, intracellular calcium, and 3) vascular endothelial function is more sensitive to oxygen withdrawal than the myocyte. 相似文献
77.
C de Costa 《The Medical journal of Australia》1986,144(13):721-722
78.
é. Cavro elodiecavro@hotmail.fr C. Bungener Catherine.Bungener@univ-paris.fr A. Bioy antoine.bioy@bct.aphp.fr 《Revue Francophone de Psycho-Oncologie》2005,4(2):74-79
Résumé: La rémission du cancer peut être l’occasion pour certains patients d’une réelle détresse émotionnelle ainsi que d’une désadaptation psychologique appelées: syndrome de Lazare. Nous émettons trois hypothèses explicatives quant à la survenue de tels troubles. La première confronte l’issue du cancer aux concepts psychanalytiques de dette et de masochisme. La deuxième envisage les symptômes sous l’angle d’une réaction de sevrage. Et la dernière évoque le contrecoup traumatique des traitements.Dossier: «Cliniques du cancer» 相似文献
79.
80.
The study of the cognitive abilities of hearing-impaired children is important for both practical (e.g. to determine appropriate teaching strategies) and theoretical reasons (e.g. to examine the role of language in thought processes). The aim of this paper is to examine the cognitive function of hearing-impaired children from a review of the literature. If most studies show that deaf children are similar to normal children in virtually all aspects of cognitive function, many studies also emphasize pronounced differences in their academic achievement. Besides the degree of hearing loss and the age at onset of deafness, environmental factors (such as parental support and educational methods) seem to play an important role in the cognitive development and academic success of these children. This underlines the importance of the measures adopted for the deaf children as they may have a positive or negative impact on their development. 相似文献