首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   5453篇
  免费   416篇
  国内免费   28篇
耳鼻咽喉   29篇
儿科学   142篇
妇产科学   102篇
基础医学   676篇
口腔科学   47篇
临床医学   663篇
内科学   1000篇
皮肤病学   90篇
神经病学   858篇
特种医学   404篇
外科学   838篇
综合类   70篇
一般理论   1篇
预防医学   269篇
眼科学   93篇
药学   342篇
中国医学   4篇
肿瘤学   269篇
  2021年   53篇
  2020年   41篇
  2019年   57篇
  2018年   77篇
  2017年   66篇
  2016年   83篇
  2015年   96篇
  2014年   108篇
  2013年   137篇
  2012年   217篇
  2011年   200篇
  2010年   140篇
  2009年   158篇
  2008年   228篇
  2007年   261篇
  2006年   230篇
  2005年   258篇
  2004年   213篇
  2003年   239篇
  2002年   229篇
  2001年   218篇
  2000年   189篇
  1999年   159篇
  1998年   67篇
  1997年   58篇
  1996年   61篇
  1995年   73篇
  1994年   52篇
  1993年   61篇
  1992年   104篇
  1991年   105篇
  1990年   110篇
  1989年   120篇
  1988年   105篇
  1987年   106篇
  1986年   98篇
  1985年   129篇
  1984年   81篇
  1983年   67篇
  1982年   46篇
  1981年   47篇
  1980年   39篇
  1979年   77篇
  1978年   50篇
  1977年   59篇
  1976年   49篇
  1975年   37篇
  1974年   57篇
  1973年   49篇
  1972年   38篇
排序方式: 共有5897条查询结果,搜索用时 15 毫秒
81.
Serial dexamethasone suppression tests (DST), obtained during a course of electroconvulsive therapy in 43 severely depressed patients, did not exhibit relationships between the initial DST, final DST, or the change in DST with clinical outcome measures at the time of discharge. In 37 patients reviewed six months after discharge, no relationship with the continuation of improvement, rehospitalization, or suicide was found. We are unable to confirm a clinical application for the DST in the management of patients during a course of convulsive therapy.  相似文献   
82.
83.
AimRates of simultaneous liver and kidney transplantation (SLKT) have increased, but indications for SLKT remain poorly defined. Additional data are needed to determine which patients benefit from SLKT to best direct use of scarce donor kidneys.MethodsData were extracted from the Australia and New Zealand Dialysis and Transplant Registry (ANZDATA) database for all SLKT performed until the end of 2017. Patients were divided by pretransplant dialysis status into no dialysis before SLKT (preemptive kidney transplant) and any dialysis before SLKT (nonpreemptive). Baseline characteristics and outcomes were compared.ResultsBetween 1989 and 2017, inclusive, 84 SLKT procedures were performed in Australia, of which 24% were preemptive. Preemptive and nonpreemptive SLKT recipients did not significantly differ in age (P = .267), sex (P = .526), or ethnicity (P = .870). Over a median follow-up time of 4.5 years, preemptively transplanted patients had a statistically equivalent risk of kidney graft failure (hazard ratio (HR) 1.83, 95% confidence interval [CI]: 0.36-12.86, P = .474) and all-cause mortality (HR 1.69, 95% CI: 0.51-5.6, P = .226) compared to nonpreemptive patients. Overall, 1- and 5-year survival rates for all SLKTs were 92% (95% CI: 86-96) and 60% (95% CI: 45-75), respectively.ConclusionKidney graft and overall patient survival were similar between patients with preemptive kidney transplant and those who were dialysis dependent.  相似文献   
84.
Chaperone-mediated protein folding   总被引:44,自引:0,他引:44  
The folding of most newly synthesized proteins in the cell requires the interaction of a variety of protein cofactors known as molecular chaperones. These molecules recognize and bind to nascent polypeptide chains and partially folded intermediates of proteins, preventing their aggregation and misfolding. There are several families of chaperones; those most involved in protein folding are the 40-kDa heat shock protein (HSP40; DnaJ), 60-kDa heat shock protein (HSP60; GroEL), and 70-kDa heat shock protein (HSP70; DnaK) families. The availability of high-resolution structures has facilitated a more detailed understanding of the complex chaperone machinery and mechanisms, including the ATP-dependent reaction cycles of the GroEL and HSP70 chaperones. For both of these chaperones, the binding of ATP triggers a critical conformational change leading to release of the bound substrate protein. Whereas the main role of the HSP70/HSP40 chaperone system is to minimize aggregation of newly synthesized proteins, the HSP60 chaperones also facilitate the actual folding process by providing a secluded environment for individual folding molecules and may also promote the unfolding and refolding of misfolded intermediates.  相似文献   
85.
To date, the delineation of the human visual “motion area” still relies on functional paradigms originally devised to identify monkey area MT. Using fMRI, we have identified putative human area V5/MT+ in normals by modelling the BOLD responses to alternating radially moving and stationary dot patterns. Functional activations were compared with cytoarchitectonic probability maps of its putative correlate area hOc5, which was calculated based upon data from histological sections of ten human post-mortem brains. Bilateral visual cortex activations were seen in the single subject dynamic versus stationary contrasts and in the group random-effects analysis. Comparison of group data with area hOc5 revealed that 19.0%/39.5% of the right/left functional activation was assigned to the right/left hOc5. Conversely, 83.2%/53.5% of the right/left hOc5 was functionally activated. Comparison of functional probability maps (fPM) with area hOc5 showed that 28.6%/18.1% of the fPM was assigned to hOc5. In turn, 84.9%/41.5% of the area hOc5 was covered by the respective fPM. Thus, random-effects data and fPMs yielded similar results. The present study shows for the first time the correspondence between the functionally defined human V5/MT+ and the post-mortem cytoarchitectonic area hOc5.  相似文献   
86.
87.
Sexual harassment is not new to the health care industry. What is new is that recent media attention has heightened awareness that sexual harassment is illegal. This fact, coupled with the substantial liability that employers may incur if they fail to control sexual harassment, mandates the need for outlining the major issues relative to sexual harassment in today's health care setting. This article gives particular emphasis to the fact that sexual harassment can be prevented by taking a proactive stance.  相似文献   
88.
Summary Rat brain cortex slices and synaptosomes preincubated with [3H]noradrenaline were used to investigate whether the NMDA-evoked noradrenaline release is modulated by agonists or antagonists at presynaptic 2-adrenoceptors.In experiments on slices, noradrenaline and the preferential 2-adrenoceptor agonists talipexole (former B-HT 920) and clonidine inhibited the NMDA evoked tritium overflow whereas the selective 1-adrenoceptor agonists cirazoline and methoxamine were ineffective. The 2-adrenoceptor antagonists rauwolscine and idazoxan facilitated the NMDA-evoked tritium overflow whereas the preferential 1-adrenoceptor antagonist prazosin was ineffective. The concentration-response curve of talipexole for its inhibitory effect on NMDA-evoked overflow was shifted to the right by idazoxan (apparent pA2 = 7.5). The EC50 of NMDA (97 mol/l) for its stimulating effect on tritium overflow was not substantially changed by blockade of 2-autoreceptors with 1 mol/l rauwolscine (EC50 of NMDA in the presence of the 2-adrenoceptor antagonist, 155 mol/l), but the maximal overflow of tritium was increased 2.5 fold by this rauwolscine concentration. In experiments on synaptosomes, talipexole and noradrenaline inhibited the NMDA-evoked tritium overflow. The inhibitory effect of talipexole was abolished by idazoxan which, given alone, was ineffective, as was prazosin. Talipexole did also not produce an inhibition when tritium overflow was evoked by NMDA in the presence of -conotoxin GVIA 0.1 mol/l; the latter, by itself, decreased the response to NMDA by about 55%. It is concluded that the NMDA-evoked noradrenaline release in the cerebral cortex is modulated via presynaptic 2-adrenoceptors on the noradrenergic neurones. Stimulation of these autoreceptors in slices by endogenous noradrenaline does not result in a decreased potency of NMDA, but in a decreased maximum effect, in stimulating noradrenaline release. The inhibitory effect of 2-adrenoceptor agonists on the NMDA-evoked release is at least partially due to a functional interaction between the NMDA receptors and 2-autoreceptors at the level of the same varicosities. The results obtained with -conotoxin GVIA suggest that Ca2+ influx via the N-type voltage-sensitive calcium channel (VSCC) occurs in response to NMDA receptor stimulation and contributes substantially to the induction of NMDA-evoked noradrenaline release. The inhibitory effect of 2-adrenoceptor stimulation on this release appears to be ultimately due to an inhibition of the influx of Ca2+ via the N-type VSCC. Correspondence to: M. Göthert at the above address  相似文献   
89.
Summary Rat brain cortex slices or synaptosomes preincubated with 3H-serotonin were superfused with physiological salt solution (which, in the case of slices, contained citalopram, an inhibitor of serotonin uptake), and the effects of histamine and related drugs on the evoked tritium overflow were studied.The electrically (3 Hz) evoked tritium overflow from slices was inhibited by histamine and the H3 receptor agonists R-(–)--methylhistamine and N-methylhistamine (pIC12.5 values: 6.41, 7.28 and 6.12, respectively), but not affected by the H1 receptor agonist 2-(2-thiazolyl)ethylamine and the H2 receptor agonist dimaprit (each at 10 mol/l). The concentration-response curve for histamine was shifted to the right by the H3 receptor antagonists impromidine, burimamide and thioperamide (apparent pA2 values: 7.45, 5.97 and 7.88, respectively); the concentration-response curve of serotonin for its inhibitory effect on the electrically evoked overflow was not affected by the three drugs (apparent pA2 values: < 5.5, < 5.5 and < 6.5). Given alone, impromidine, thioperamide and a low concentration of burimamide facilitated the electrically evoked overflow. In slices superfused with K+-rich, Ca2+-free solution containing tetrodotoxin throughout and in synaptosomes superfused with Ca2+-free solution, histamine inhibited the overflow evoked by introduction of Ca2+ (in synaptosomes, simultaneously with an increased amount of K+). In either tissue, the effect of histamine was counteracted by thioperamide.The results provide evidence that exogenous and probably also endogenous histamine inhibits serotonin release in the rat brain cortex via presynaptic histamine H3 receptors.Send offprint requests to E. Schlicker at the above address  相似文献   
90.
The present study was designed to examine possible interactions between exogenous CCK and the 5-HT1A receptor subtype mediated serotonergic effects on feeding in rats. The somatodendritic 5-HT1A receptor agonist 8-OH-DPAT (0.32 mg/kg sc) evoked feeding in freely feeding rats. This effect was attenuated by treatment with CCK-8 (1, 5 and 25 g/kg ip). In food deprived rats, CCK-8 (40 g/kg ip) significantly reduced the size of a test meal. Treatment with the 5-HT1A receptor antagonist WAY-100135 (10 mg/kg ip) antagonized this anorectic effect of CCK-8. WAY-100135 on its own did not affect food intake. These results suggest the involvement of the 5-HT1A receptor subtype in mediating 5-HT-CCK interactions in the control of food intake in rats.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号