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   17302篇
  免费   1168篇
  国内免费   48篇
耳鼻咽喉   158篇
儿科学   520篇
妇产科学   533篇
基础医学   2585篇
口腔科学   354篇
临床医学   2077篇
内科学   3283篇
皮肤病学   493篇
神经病学   1675篇
特种医学   320篇
外科学   1537篇
综合类   107篇
一般理论   40篇
预防医学   1880篇
眼科学   261篇
药学   1249篇
中国医学   32篇
肿瘤学   1414篇
  2024年   16篇
  2023年   186篇
  2022年   442篇
  2021年   723篇
  2020年   359篇
  2019年   619篇
  2018年   643篇
  2017年   449篇
  2016年   539篇
  2015年   538篇
  2014年   744篇
  2013年   956篇
  2012年   1408篇
  2011年   1444篇
  2010年   786篇
  2009年   640篇
  2008年   1051篇
  2007年   1089篇
  2006年   1048篇
  2005年   959篇
  2004年   873篇
  2003年   744篇
  2002年   687篇
  2001年   131篇
  2000年   111篇
  1999年   99篇
  1998年   126篇
  1997年   88篇
  1996年   79篇
  1995年   64篇
  1994年   79篇
  1993年   58篇
  1992年   65篇
  1991年   57篇
  1990年   43篇
  1989年   48篇
  1988年   50篇
  1987年   32篇
  1986年   32篇
  1985年   38篇
  1984年   37篇
  1983年   34篇
  1982年   32篇
  1981年   39篇
  1980年   34篇
  1979年   19篇
  1978年   22篇
  1977年   25篇
  1976年   18篇
  1974年   22篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
The etiology of obesity is multifactorial and still unclear. Genetic factors play a significant role and include several gene candidates: polymorphisms of genes for ss(2)-adrenoreceptor, resistin, estrogen receptor-a and peroxisome proliferator-activated receptor-gamma. Moreover, peptides regulating hunger and satiety, e.g. leptin, galanin, cholecystokinin and neuropeptide Y, and altered nutritional patterns have been implicated. Also, factors associated with aging, e.g. decreased levels of growth hormone and dehydroepiandrosterone, and the activity of the sympathetic nervous system (resting metabolism and thermogenesis) cannot be disregarded. Participation of the sex steroids and inflammatory factors has also been postulated in the etiology of obesity. Three phenotypes of obesity are postulated; however, the visceral (abdominal) phenotype is typical of postmenopausal women and is characterized by several metabolic disorders with high risks of diabetes mellitus type 2 and cardiovascular disease. On the basis of personal experience and data from evidence-based medicine, diagnostic-therapeutic algorithms of climacteric obesity are presented.  相似文献   
3.
Organophosphate compounds are cholinesterase inhibitors widely used in agriculture, industry, household products, and even as chemical weapons. Their major mechanism of acute toxic action is the inhibition of acetylcholinesterase, which is responsible for the degradation of the neurotransmitter acetylcholine. An organophosphorus ester-induced chronic neurotoxicity (OPICN) syndrome has been proposed. The OPICN syndrome could result from both long-term exposure to subclinical doses of OPs and after acute poisoning. Development of animal models for the cognitive decline are required and could later help to elucidate the mechanisms involved in this long-term effect on the central nervous system. Previously, we have found performance decrements in a four-trial repeated acquisition spatial task in a water maze. The present study includes two experiments to extend the long-term behavioral effects observed. Rats were injected either once or twice with chlorpyrifos (CPF) and then tested months after in a two-trial repeated acquisition task in a water maze. Our results confirm and extend the long-term behavioral effects of subcutaneous administration of CPF. The two treatments used produced performance decrements that suggest functional central nervous system alterations.  相似文献   
4.
5.
Background: Both pain and the pharmacologic management of pain can cause the undesirable effect of sleep disruption. One goal of basic and clinical neuroscience is to facilitate rational drug development by identifying the brain regions and neurochemical modulators of sleep and pain. Adenosine is thought to be an endogenous sleep promoting substance and adenosinergic compounds can contribute to pain management. In the pontine brain stem adenosine promotes sleep but the effects of pontine adenosine on pain have not been studied. This study tested the hypothesis that an adenosine agonist would cause antinociception when microinjected into pontine reticular formation regions that regulate sleep.

Methods: The tail flick latency (TFL) test quantified the time in seconds for an animal to move its tail away from a thermal stimulus created by a beam of light. TFL measures were used to evaluate the antinociceptive effects of the adenosine A1 receptor agonist N6-p-sulfophenyladenosine (SPA). Pontine microinjection of SPA (0.1 [mu]g/0.25 [mu]l, 0.88 mm) was followed by TFL measures as a function of time after drug delivery and across the sleep-wake cycle.

Results: Compared with saline (control), pontine administration of the adenosine agonist significantly increased latency to tail withdrawal (P < 0.0001). The increase in antinociceptive behavior evoked by the adenosine agonist SPA was blocked by pretreatment with the adenosine A1 receptor antagonist 8-cyclopentyl-1, 3-dipropylxanthine (DPCPX, 0.75 ng/0.25 [mu]l, 10 [mu]m).  相似文献   

6.
While commercial surrogate parenting arrangements continue to flourish in the U.S., Britain has made it a criminal offense for third parties to benefit from surrogacy. Voluntary surrogacy, however is still within the law. Banning commercial surrogacy while leaving voluntary surrogacy lawful seems neither logical nor fair. A more equitable solution would be to license stringently and control both commercial and nonprofit agencies to provide these services.  相似文献   
7.
OBJECTIVE: To assess the impact of activity restriction (AR) on the incidence of preterm birth in women treated for preterm labor testing negative for fetal fibronectin (fFN). STUDY DESIGN: Women who were diagnosed with preterm labor and tocolyzed with magnesium sulfate were concurrently screened with fFN for the purpose of subsequent management. Included were consenting patients with negative fFN, gestational age 23 0/7-33 6/7 weeks, cervical dilation < or =3 cm, and minimal vaginal bleeding. Patients were randomized to AR or no AR. Primary study outcome was incidence of preterm delivery and interval from randomization to delivery. RESULTS: A total of 73 women with negative fFN were randomized (36 with AR, 37 without AR). The overall preterm birth rate was 40%, with 44.4% of patients with AR and 35.1% of patients without AR delivering preterm, p=0.478. CONCLUSION: Maternal AR did not impact pregnancy outcome. The incidence of preterm birth in symptomatic women testing fFN negative was higher than previously reported.  相似文献   
8.
9.
10.
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