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   20207篇
  免费   1833篇
  国内免费   23篇
耳鼻咽喉   104篇
儿科学   616篇
妇产科学   553篇
基础医学   2954篇
口腔科学   287篇
临床医学   2619篇
内科学   3906篇
皮肤病学   454篇
神经病学   1978篇
特种医学   758篇
外科学   2577篇
综合类   610篇
一般理论   15篇
预防医学   1714篇
眼科学   267篇
药学   1321篇
中国医学   16篇
肿瘤学   1314篇
  2021年   333篇
  2020年   234篇
  2019年   345篇
  2018年   412篇
  2017年   316篇
  2016年   305篇
  2015年   317篇
  2014年   471篇
  2013年   694篇
  2012年   989篇
  2011年   945篇
  2010年   538篇
  2009年   512篇
  2008年   901篇
  2007年   920篇
  2006年   932篇
  2005年   828篇
  2004年   856篇
  2003年   800篇
  2002年   688篇
  2001年   681篇
  2000年   717篇
  1999年   624篇
  1998年   224篇
  1997年   190篇
  1996年   198篇
  1995年   185篇
  1994年   177篇
  1993年   169篇
  1992年   467篇
  1991年   449篇
  1990年   416篇
  1989年   369篇
  1988年   353篇
  1987年   396篇
  1986年   363篇
  1985年   366篇
  1984年   290篇
  1983年   251篇
  1982年   160篇
  1981年   159篇
  1980年   132篇
  1979年   241篇
  1978年   198篇
  1977年   137篇
  1975年   116篇
  1974年   166篇
  1973年   162篇
  1972年   152篇
  1971年   133篇
排序方式: 共有10000条查询结果,搜索用时 859 毫秒
31.
AIM: Although research has demonstrated the efficacy of pelvic floor exercises (PFXs) for the prevention and treatment of female urinary incontinence (FUI), adherence to PFX regimens is commonly poor. There is some evidence that this finding is in part due to a lack of knowledge about how to perform PFXs correctly and misconceptions about the required frequency and duration of PFX regimens. METHODS: By using a sample of 720 postpartum women, this study investigates women's PFX regimens both before and during pregnancy and postpartum. RESULTS: Findings demonstrated that most women were aware of the required frequency for PFXs (at least every second day): just over half had done them this often during pregnancy and 91% intended to do so postpartum. However, few had done them at this level before pregnancy and less than half knew that PFXs should be carried out indefinitely throughout the lifetime. Moreover, only two thirds were confident that they were doing PFXs correctly. CONCLUSION: The findings suggest that, despite good knowledge of the required frequency of PFXs, few women practise them regularly over their lifetime, many apparently perceiving PFXs as relevant only to the childbirth years. Implications for health professionals in addressing these gaps in women's knowledge and practises are discussed.  相似文献   
32.
BACKGROUND: A subgroup of children with obsessive-compulsive and tic disorders are proposed to have an infectious trigger. The purpose of this study was to investigate the relationship between group A streptococcal titers and symptom fluctuations in children with a clinical course resembling that described for pediatric autoimmune neuropsychiatric disorders associated with streptococcus. METHODS: Twenty-five children with obsessive-compulsive disorder and/or tic disorder were evaluated for neuropsychiatric severity and group A streptococcal antibody titers (streptolysin O, deoxyribonuclease B, and carbohydrate A) at 6-week intervals for > or = six consecutive evaluations (total visits=277). RESULTS: Children with large symptom fluctuations (n=15) were compared with children without dramatic fluctuations (n=10). Co-movements of obsessive-compulsive/tic severity and group A streptococcal antibodies were assessed. In subjects with large symptom changes, positive correlations were found between streptococcal titers and obsessive-compulsive severity rating changes (p=.0130). These subjects were also more likely to have elevated group A streptococcal titers during the majority of observations (p=.001). Tic symptom exacerbations occurred more often in the fall/winter months than spring/summer months (p=.03). CONCLUSIONS: Patients with marked obsessive-compulsive/tic symptom changes may be characterized by streptococcal titer elevations and exhibit evidence of seasonal tic exacerbations.  相似文献   
33.
Unidirectional fluxes of 45Ca, 36Cl, and of [3H]mannitol from blood into the sciatic nerve and cerebral cortex were determined from 5- and 15-min uptakes of these tracers after an intravenous (i.v.) bolus injection in awake rats. Rats were fed diets for 8 wk, that had either a low (0.01% wt/wt), normal (0.67%), or high (3%) Ca content. Plasma [Ca] was 32% less and 11% more in rats fed low (LOCA) and high Ca diets (HICA), respectively, than in rats fed a normal Ca diet (CONT). The mean permeability-surface area product (PA) of 45Ca at the blood-nerve barrier was about eightfold higher than at the blood-brain barrier in the same animals and did not differ significantly between groups (greater than 0.05). Mean PA ratios of 45Ca/36Cl for the blood-nerve and blood-brain barriers in CONT rats, 0.52 +/- 0.04 and 0.40 +/- 0.02, respectively, were not significantly different from corresponding ratios in LOCA and HICA groups, and corresponded to the aqueous limiting diffusion ratio (0.45). Our results show no evidence for concentration-dependent transport of Ca over a plasma [Ca] range of 0.8-1.4 mmol/liter at the blood-nerve barrier of the rat peripheral nerve, and suggest that Ca and Cl exchange slowly between nerve and blood via paracellular pathways.  相似文献   
34.
35.
Thyrotropin releasing hormone (TRH) was administered intravenously to ten patients with Alzheimer's Disease (AD) in a high-dose paradigm, thought to maximize central nervous system effects and potentially produce facilitation of cholinergic function, a known property of the neuropeptide. Acute effects of TRH on behavioral, cognitive and physiologic measures were assessed after patients received 0.1 mg/kg TRH, 0.3 mg/kg TRH and placebo, the higher TRH dose and placebo being given in a randomized, double-blind fashion. Patients showed statistically significant increases in arousal and improvement in affect, as well as a modest improvement in semantic memory, all after receiving the higher TRH dose. Both TRH doses produced transient rises in systolic blood pressure, with no effect on diastolic blood pressure, heart rate or temperature. This study suggests that high-dose TRH can be safely administered to AD patients and is neurobehaviorally active; further studies are needed to determine the extent and mechanism of the cognitive and psychobiological properties of this peptide in AD and other neuropsychiatric disorders.  相似文献   
36.
Thromboxane, a prostanoid derivative, is a central mediator of the progressive dermal ischemia seen in the distal dying flap. Prostacyclin; a vasoactive prostanoid derivative, has been found to enhance ischemic flap survival. This study examines the effects of prostacyclin and UK 38485 (specific thromboxane synthetase inhibitor), separately and combined, in axial flap survival in the pig. Each increased flap survival over control flaps; their combined use demonstrated an even greater flap survival (p less than 0.005).  相似文献   
37.
38.
The effect of long-term (3-week) administration of various antidepressant drugs on the steady-state concentrations of G protein alpha subunits, Gs alpha, Gi alpha, and Go alpha, has been investigated in rat brain using an enzyme-linked immunosorbent assay. Tricyclic antidepressants and clorgyline decreased Gs alpha and, to a lesser extent, Gi alpha in several brain regions, while Go alpha was increased by tricyclics but not clorgyline. We conclude that long-term treatment with antidepressant drugs exerts differential effects on G protein alpha subunits, and that antidepressant efficacy may potentially be based on functional modifications of signal transduction.  相似文献   
39.
40.
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