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   442092篇
  免费   39698篇
  国内免费   30780篇
耳鼻咽喉   4004篇
儿科学   4793篇
妇产科学   6036篇
基础医学   52644篇
口腔科学   7657篇
临床医学   60385篇
内科学   65619篇
皮肤病学   4492篇
神经病学   24159篇
特种医学   16695篇
外国民族医学   275篇
外科学   45845篇
综合类   72345篇
现状与发展   99篇
一般理论   29篇
预防医学   28633篇
眼科学   12503篇
药学   44930篇
  423篇
中国医学   24899篇
肿瘤学   36105篇
  2024年   1372篇
  2023年   6643篇
  2022年   17027篇
  2021年   21607篇
  2020年   16108篇
  2019年   14196篇
  2018年   14908篇
  2017年   13346篇
  2016年   12570篇
  2015年   19170篇
  2014年   23929篇
  2013年   21491篇
  2012年   31767篇
  2011年   35591篇
  2010年   22646篇
  2009年   17881篇
  2008年   23894篇
  2007年   23956篇
  2006年   23614篇
  2005年   23017篇
  2004年   14953篇
  2003年   13684篇
  2002年   11685篇
  2001年   10270篇
  2000年   11044篇
  1999年   11721篇
  1998年   7236篇
  1997年   7263篇
  1996年   5696篇
  1995年   5230篇
  1994年   4375篇
  1993年   2808篇
  1992年   3736篇
  1991年   3149篇
  1990年   2727篇
  1989年   2420篇
  1988年   2038篇
  1987年   1774篇
  1986年   1494篇
  1985年   1213篇
  1984年   676篇
  1983年   499篇
  1982年   326篇
  1981年   318篇
  1980年   245篇
  1979年   285篇
  1978年   92篇
  1977年   92篇
  1974年   107篇
  1973年   88篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
目的 探索对海洛因依赖重度药瘾较理想的戒毒治疗方法。  方法 采用美沙酮与丁丙诺啡联合用药方案 ,对海洛因依赖重度药瘾 41例行戒毒治疗 ,1 2天为一疗程 ,并与单用美沙酮组 2 0例进行比较。  结果 联合用药组控制症状较彻底 ,鸦片类药物戒断症状量表 (OWS)总分平稳下降 ,症状波动小 ,减药顺利 ,两药替换平稳 ,戒毒成功率 73 2 %。  结论 我们认为美沙酮联用丁丙诺啡是一种值得推荐的戒毒治疗方法。  相似文献   
82.
Miniaturized glucose biosensors, prepared by electrochemical deposition of iridium and glucose oxidase (GOx), are characterized. The iridium network offers good retention of GOx and efficient preferential electrocatalytic detection of the liberated hydrogen peroxide at potentials lower than those of common interfering substances (the ascorbic acid signal actually shifts to a higher potential). The remarkable selectivity thus achieved towards the detection of glucose is coupled to a very fast response. Unlike analogous preparations of noble metal carbon fiber biosensors, a two-step electrodeposition process is required for the fabrication of Ir/GOx microelectrodes. The dependence of the biosensor response upon electrodeposition parameters, such as amounts of GOx and iridium or plating time is examined and optimized. Scanning electron microscopy is used to characterized the growth patterns of the iridium and Ir/GOx layers. The high selectivity associated with electrodeposited iridium matrices makes them very attractive for localizing other hydrogen-peroxide-liberating oxidases.  相似文献   
83.
Rh血型不合新生儿溶血病检测方法及应用   总被引:3,自引:0,他引:3  
产前检测Rh,D因子及抗人球蛋白(coombs)试验是必要的。测定Rh,D因子及抗D滴度使用木瓜酶方法。通过对11261例孕妇常规检查Rh,D因子,发现D阴性74例。Rh,D阴性妇女占6.5‰。22例Rh,D阴性的孕妇所分娩的新生儿均为Rh,D阳性。其中2例孕妇血清抗D滴度为1∶32,病情严重,宫内输血无效,胎死宫内。初产妇13例,占59%。活产20例,存活率90%。Rh因子及抗人球蛋白试验方法简便、易行,一般医院均可进行。对有流产史、输血史的孕妇检查Rh因子是十分必要的。在有条件的医院,对Rh,D阴性的产妇分娩Rh,D阳性的新生儿之后,产妇应预防性注射抗D免疫球蛋白  相似文献   
84.
Five commercially available nitropolyclyclic aromatic hydrocarbons (nitro-PAH), namely, 4-nitrobiphenyl, 2-nitrofluorene, 9-nitroanthracene, 1-nitropyrene, and 2,7-dinitrofluorene, were exposed under restricted sunlight in the open air. The direct-acting mutagenicities of the samples after an exposure of 45 days were measured in order to compare them with those of the original samples in the Ames Salmonella typhimurium bioassay. It was found that the mutagenicities of some nitro-PAH do not change significantly while the mutagenicities of others increase or decrease after exposure. A preliminary study of nitro-PAH reaction products after exposure using GC, GC/MS, and FT-IR is also reported.  相似文献   
85.
The application of electron paramagnetic resonance imaging (EPRI) to obtain information from biological samples has been limited by the lack of ideal single line radical labels. The commonly used nitroxides exhibit multiple lines causing either hyperfine-based limitations in the maximum obtainable image resolution or hyperfine-based artifacts in the reconstructed image. The use of a novel single-line triarylmethyl paramagnetic label that enables marked enhancement in image quality and resolution is reported. This label exhibits a single line EPR spectrum that is sharp (linewidth ~60 mG in the absence of oxygen) and relatively stable in tissues. The potential of this label in enabling high resolution EPR imaging of biological samples was demonstrated in a series of phantoms and isolated biological organs such as the rat kidney. The images demonstrate that resolutions better than 100 μm could be obtained at L-band on samples of up to 20 mm in size.  相似文献   
86.
中老年人前列腺体积增长的城乡差异   总被引:27,自引:1,他引:26  
为了解国人中年以后前列腺的生长情况及其可能的影响因素,对北京、河北、湖北等地四个社区的城乡居民前列腺体积进行了经腹B超测量。结果表明城区居民的前列腺体积明显大于相应年龄段的农村居民,城区居民的前列腺增长速率比农村居民高二倍。生活环境和饮食习惯的不同可能为其原因之一。  相似文献   
87.
88.
The potential cytoprotective actions of a novel nicotinic agent 2,4-dimethoxybenzilidene anabaseine (DMXB) were investigated in differentiated PC12 cells and transected rat septal cholinergic neurons in vivo. In NGF-differentiated PC12 cells, removal of both NGF and serum led to cell loss, a reduced % of cells expressing neurites, the release of lactate dehydrogenase, and a decrease in total cellular protein. Cell loss was apparent within 24 h, and remained constant between 4–8 days post-NGF removal. NGF alone (100 ng/ml), DMXB (10 μM), but not nicotine (10 μM), prevented these cell and neurite losses. DMXB-induced cytoprotection was blocked by 1 μM mecamylamine. DMXB (1 mg/kg, ip) injected twice but not once per day protected cholinesterase-staining septal neurons from retrograde degeneration following unilateral fimbrial transections. The twice per day DMXB injection-protocol also decreased cell roundness among cholinesterase-staining cells in the lesioned septal hemisphere compared to saline-injected animals. These studies suggest that DMXB may exert cytoprotective activity in NGF-sensitive neuronal populations. © 1994 Wiley-Liss, Inc.  相似文献   
89.
This study examined the effect of acute and chronic administration of the selective 5-HT3 receptor antagonist BRL 46470A, an analog of granisetron, on the number of spontaneously active dopamine (DA) cells in the substantia nigra pars compacta (A9 or SNC) and the ventral tegmental area (A10 or VTA) in the rat. In the A10 area, the acute administration of BRL 46470A decreased the number of spontaneously active DA cells at a dose of 0.1 mg/kg (0.28 μmol/kg) ip, yet increased the number of spontaneously active DA cells at a dose of 0.3 mg/kg (0.84 μmol/kg). The chronic administration (21 days) of BRL 46470A appeared to produce a multiphasic dose-response curve. Thus, the chronic treatment with BRL 46470A increased the number of spontaneously active A10 DA cells at 0.03 (0.084 μmol) and 0.3 mg/kg, but decreased the number of spontaneously active A10 DA cells at a dose of 0.1 mg/kg. In contrast, BRL 46470A did not decrease the number of spontaneously active A9 DA cells after either acute or chronic administration (0.01-0.3 mg/kg). However, BRL 46470A did increase the number of spontaneously active A9 DA cells at acute and chronic doses similar to those that were effective in A10. The iv administration of (+)-apomorphine (APO) not only failed to reverse the decrease produced by chronic administration of BRL 46470A at 0.1 mg/kg, but further decreased the number of spontaneously active A10 DA cells. Similar to the results obtained with granisetron, the pretreatment of naive rats with either 0.01 or 0.1 mg/kg iv of BRL 46470A significantly potentiated (2-fold) the suppressant action of APO on the basal firing rate of A10, but not A9 DA cells. Overall, our results indicate that similar to granisetron, chronic BRL 46470A at 0.1 mg/kg selectively decreases the number of spontaneously active A10 DA cells, via a mechanism not related to depolarization inactivation. Presently, it is not clear what factors may contribute to the multiphasic dose-response curve of BRL 46470A. © 1994 Wiley-Liss, Inc.  相似文献   
90.
Study Objective . To compare digoxin tablets and liquid-filled capsules with respect to excretion of the drug and its metabolites in urine and feces at steady state. Design . A randomized, crossover trial, each period lasting 3 weeks, with no washout period. Setting . A university hospital. Patients . Six patients, five of whom were elderly, with histories of gastrointestinal disorders, such as hypochlorhydria, intestinal bacterial overgrowth, and inflammatory bowel disease. Interventions . The patients received digoxin once/day in either tablet or capsule form for 3 weeks, and then were switched to the other formulation. Total urinary and fecal excretion from the last 3 days of each regimen were analyzed for the drug and metabolites. Measurements and Main Results . No statistically significant differences were found between tablets and capsules in recovery of digoxin or its metabolites in urine or feces (p=0.05). One subject had a 4-fold increase in urinary drug excretion and 50% decrease in fecal excretion after taking the capsules compared with tablets. Intersubject variability in extent and type of metabolite excretion was greater than intrasubject variability. Conclusions . Fecal analyses may be an accurate way to classify patients as formers of digoxin reduction products.  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