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   128860篇
  免费   10882篇
  国内免费   8170篇
耳鼻咽喉   1041篇
儿科学   1606篇
妇产科学   2371篇
基础医学   15130篇
口腔科学   2180篇
临床医学   16769篇
内科学   21024篇
皮肤病学   1468篇
神经病学   7062篇
特种医学   4406篇
外国民族医学   70篇
外科学   13383篇
综合类   18969篇
现状与发展   24篇
一般理论   6篇
预防医学   8354篇
眼科学   3751篇
药学   12995篇
  115篇
中国医学   6053篇
肿瘤学   11135篇
  2024年   349篇
  2023年   1836篇
  2022年   4679篇
  2021年   5912篇
  2020年   4249篇
  2019年   4116篇
  2018年   4173篇
  2017年   3728篇
  2016年   3497篇
  2015年   5271篇
  2014年   6593篇
  2013年   6205篇
  2012年   9083篇
  2011年   9958篇
  2010年   6023篇
  2009年   4829篇
  2008年   6673篇
  2007年   6680篇
  2006年   6721篇
  2005年   6672篇
  2004年   4675篇
  2003年   4388篇
  2002年   3710篇
  2001年   3248篇
  2000年   3332篇
  1999年   3467篇
  1998年   2277篇
  1997年   2181篇
  1996年   1584篇
  1995年   1486篇
  1994年   1288篇
  1993年   838篇
  1992年   1249篇
  1991年   1085篇
  1990年   947篇
  1989年   842篇
  1988年   728篇
  1987年   687篇
  1986年   518篇
  1985年   478篇
  1984年   273篇
  1983年   201篇
  1982年   131篇
  1981年   128篇
  1980年   88篇
  1979年   137篇
  1978年   73篇
  1976年   68篇
  1975年   67篇
  1974年   79篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
Prolongation of the action potential duration of dorsal root ganglion (DRG) neurons by low (nM) concentrations of opioids occurs through activation of excitatory opioid receptors that are positively coupled via Gs regulatory protein to adenylate cyclase. Previous results suggested GM1 ganglioside to have an essential role in regulating this excitatory response, but not the inhibitory (APD-shortening) response to higher (μM) opioid concentrations. Furthermore, it was proposed that synthesis of GM1 is upregulated by prolonged activation of excitatory opioid receptor functions. To explore this possibility we have utilized cultures of hybrid F11 cells to carry out closely correlated electrophysiological and biochemical analyses of the effects of chronic opioid treatment on a homogeneous population of clonal cells which express many functions characteristic of DRG neurons. We show that chronic opioid exposure of F11 cells does, in fact, result in elevated levels of GM1 as well as cyclic adenosine monophosphate (AMP), concomitant with the onset of opioid excitatory supersensitivity as manifested by naloxone-evoked decreases in voltage-dependent membrane K+ currents. Such elevation of GM1 would be expected to enhance the efficacy of excitatory opioid receptor activation of the Gs/adenylate cyclase/cyclic AMP system, thereby providing a positive feedback mechanism that may account for the remarkable supersensitivity of chronic opioid-treated neurons to the excitatory effects of opioid agonists as well as antagonists. These in vitro findings may provide novel insights into the mechanisms underlying naloxone-precipitated withdrawal syndromes and opioid-induced hyperalgesia after chronic opiatf addiction in vivo. © 1995 Wiley-Liss, Inc.  相似文献   
24.
多发性肌炎的动物模型及雷公藤多甙对其疗效的研究   总被引:4,自引:0,他引:4  
目的 寻找一种多发性肌炎的良好动物模型及其有效的治疗药物。  方法 给动物注射同种大鼠的肌匀浆 ,观察其活动状态 ;通过肌肉组织染色及ELISA法 ,研究肌肉的病理学变化 ,同时给动物喂服雷公藤多甙观察药物疗效。  结果 部分动物表现肌无力和肌萎缩 ,大多数肌肉组织学检查示肌纤维炎性变 ;免疫组化检查可见肌膜、肌内膜和肌束膜中有IgG沉积。动物服雷公藤多甙后肌肉病变明显减轻 ,其疗效与强的松相似。  结论 用同种大鼠肌匀浆免疫动物可诱导出多发性肌炎的动物模型 ;雷公藤多甙能有效地治疗多发性肌炎。  相似文献   
25.
26.
四叠体池蛛网膜囊肿   总被引:2,自引:0,他引:2  
目的:探讨四叠体池蛛网膜囊肿的临床特征和治疗方法。方法:对11例四叠体池蛛网膜囊肿进行了回顾性总结分析。所采用的手术方法有:①脑室分流手术;②囊肿-腹腔分流术;③囊肿切除;④囊肿切除加囊肿-脑池分流术,或囊肿部分切除(即囊肿开窗术),或囊肿切除加脑室-脑池分流术。结果:其主要临床表现以颅内压增高症和中线综合征为主。上述方法中单纯囊肿壁切除只能使部分病人的病情缓解,脑室分流或囊肿切除加脑室分流手术的疗效较好。结论:四叠体区蛛网膜囊肿常合并梗阻性脑积水,单纯囊肿切除不能解除多数病人的梗阻性脑积水。作者根据囊肿是否与蛛网膜下腔相通提出:对交通性蛛网膜囊肿采用单纯性脑室分流术,对非交通性者采用囊肿切除加脑室分流手术的治疗方法。  相似文献   
27.
Objective: To examine the relationship between ambient lead levels and blood lead levels and to explore the modifiers of the relationship between ambient lead and blood lead. Method: A cross-sectional study was conducted in two lead battery factories. Blood lead level and ambient lead concentration were measured for each participant concurrently. A structured questionnaire was administered to collect sociodemographic characteristics and occupational history. Design: Biological and personal environmental measurements of 219 lead-exposed workers were analyzed by both simple and multiple linear regression. A regression model was selected for interpretation. Results: A high correlation (r=0.62) between ambient lead (PbA) and blood lead (PbB) was observed. In addition, numerous factors, including age, sex, alcohol consumption, personal hygiene practice and type of lead exposure, were also found to influence blood lead levels. Although PbB was highly correlated with PbA, blood lead level may not be effectively lowered by reducing ambient lead level. Based on the regression coefficients, improvement of hygienic practice was more effective at lowering PbB than reducing ambient lead level. Good hygienic practice may be the preferential way to reduce lead exposure in current conditions. Conclusion: Education of correct work practice may be more important than engineering control in the developing countries to lower blood lead levels in lead battery factories. Received: 28 May 1996/Accepted: 30 August 1996  相似文献   
28.
The hereditary characteristics of enzyme deficiency and dermatoglyphics in congenital color blindness (CCB) were studied. We propose that there is a linkage between the two loci on the X-chromosome determining CCB and glucose-6-phosphate dehydrogenase (G6PD), based on our study of a high incidence of G6PD deficiency in 156 male cases with CCB. The CCB gene is closely linked with that of G6PD deficiency from our pedigree investigations. The rise in the frequency of eight or more whorls, the low value of atd angle and the presenting rate of real palmar patterns of the thenar, hypothenar and I, areas presented the hereditary traits of congenital color blindness.  相似文献   
29.
The visual pursuit test is a method that collects and analyzes the characteristics of pursuit eye movements and examines the function of the eye movement system. This paper analyzes the model parameters of the smooth pursuit eye movement system in order to explore a method for improving the analysis. The input-output relationship of the smooth pursuit system can be expressed by a quasilinear model. We compute the model parameters (gain, phase, spectral purity, cross covariance) by digital signal processing. Eye movement is recorded by electrooculogram. Both eyes are tested individually. The visual target moves at frequencies of 0.2, 0.4, 0.8, 1.2, and 1.6 Hz. Ranges are gain, 1.01 to 0.70; phase, -0.1 ° to -66 °; spectral purity, 0.97 to 0.70; and cross covariance, 0.99 to 0.26. We tested 40 normal subjects as well as patients with ataxia (8), vertigo (18), and ophthalmoplegia (9). The oculomotor system of normal subjects functions as a linear system in the performance of this test at 0.2 to 0.8 Hz. The spectral purity dropped to about 0.70 at 1.6 Hz. The variability of all measures increases greatly at 1.6 Hz, which indicates that this target motion exceeds the tracking ability of many normal subjects and that the oculomotor system of normal subjects functions as a nonlinear system in this condition. Statistical tests show no significant differences between sex, age, and the two eyes. The model parameters tentatively proved effective in clinical application.  相似文献   
30.
本文在分析黑龙江省妇幼保健机构设置现状的基础上,论述了在社会主义市场经济新形势下,妇幼保健机构发展的指导思想、模式与对策。  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