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   2668131篇
  免费   215018篇
  国内免费   15880篇
耳鼻咽喉   38176篇
儿科学   79607篇
妇产科学   68613篇
基础医学   371955篇
口腔科学   74435篇
临床医学   247484篇
内科学   514095篇
皮肤病学   53492篇
神经病学   220520篇
特种医学   107997篇
外国民族医学   997篇
外科学   397815篇
综合类   86102篇
现状与发展   40篇
一般理论   1019篇
预防医学   208005篇
眼科学   63519篇
药学   204509篇
  193篇
中国医学   15437篇
肿瘤学   145019篇
  2021年   26535篇
  2019年   24243篇
  2018年   32647篇
  2017年   26318篇
  2016年   28379篇
  2015年   34314篇
  2014年   46418篇
  2013年   64036篇
  2012年   88185篇
  2011年   92516篇
  2010年   55245篇
  2009年   50702篇
  2008年   83696篇
  2007年   88059篇
  2006年   88644篇
  2005年   86949篇
  2004年   80789篇
  2003年   77915篇
  2002年   76098篇
  2001年   119167篇
  2000年   123543篇
  1999年   105099篇
  1998年   31020篇
  1997年   28592篇
  1996年   27799篇
  1995年   26799篇
  1994年   25094篇
  1993年   22841篇
  1992年   81920篇
  1991年   78777篇
  1990年   75758篇
  1989年   72867篇
  1988年   67684篇
  1987年   66478篇
  1986年   62819篇
  1985年   59804篇
  1984年   45176篇
  1983年   38445篇
  1982年   23392篇
  1979年   42344篇
  1978年   29735篇
  1977年   24965篇
  1976年   23398篇
  1975年   24748篇
  1974年   30471篇
  1973年   28803篇
  1972年   27004篇
  1971年   24886篇
  1970年   23424篇
  1969年   21700篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
Dosage form is a mean used for the delivery of drug to a living body. In order to get the desired effect the drug should be delivered to its site of action at such rate and concentration to achieve the maximum therapeutic effect and minimum adverse effect. Since oral route is still widely accepted route but having a common drawback of difficulty in swallowing of tablets and capsules. Therefore a lot of research has been done on novel drug delivery systems. This review is about oral dispersible tablets a novel approach in drug delivery systems that are now a day''s more focused in formulation world, and laid a new path that, helped the patients to build their compliance level with the therapy, also reduced the cost and ease the administration especially in case of pediatrics and geriatrics. Quick absorption, rapid onset of action and reduction in drug loss properties are the basic advantages of this dosage form.  相似文献   
43.
目的对比可弯曲胸腔镜和硬质胸腔镜在不明原因胸腔积液诊断中的准确性和安全性。方法采用前瞻性随机对照研究,连续筛选四川大学华西医院2012年3月至2014年3月期间不明原因胸腔积液住院患者,患者年龄18~75岁。经知情同意后,患者随机进入可弯曲胸腔镜组或硬质胸腔镜组进行检查。结果可弯曲胸腔镜组入组49例患者,硬质胸腔镜组入组48例患者。两组共有44例患者通过胸腔镜检查确诊为恶性疾病,48例确诊为良性疾病。两组诊断不明原因胸腔积液总体准确性分别为93.9%和95.8%,可弯曲胸腔镜组诊断肿瘤的敏感性为96.0%,硬质胸腔镜组诊断肿瘤的敏感性为95.2%,两组诊断肿瘤的特异性均为100.0%,两组之间差异无统计学意义。两种胸腔镜技术并发症多数轻微,患者均耐受良好。结论对于不明原因胸腔积液,可弯曲胸腔镜诊断的准确性与硬质胸腔镜相当。尽管可弯曲胸腔镜取材组织小,但是通过多点多次取材,所获得的组织标本能满足病理科医生进行包括免疫组织化学检测在内的疾病诊断。  相似文献   
44.
45.
46.
47.
Hepatic NADPH-cytochrome P450 oxidoreductase null (HRN?) mice exhibit normal hepatic and extrahepatic biotransformation enzyme activities when compared to wild-type (WT) mice, but express no functional hepatic cytochrome P450 activities. When incubated in vitro with [14C]-diclofenac, liver microsomes from WT mice exhibited extensive biotransformation to oxidative and glucuronide metabolites and covalent binding to proteins was also observed. In contrast, whereas glucuronide conjugates and a quinone-imine metabolite were formed when [14C]-diclofenac was incubated with HRN? mouse liver, only small quantities of P450-derived oxidative metabolites were produced in these samples and covalent binding to proteins was not observed. Livers from vehicle-treated HRN? mice exhibited enhanced lipid accumulation, bile duct proliferation, hepatocellular degeneration and necrosis and inflammatory cell infiltration, which were not present in livers from WT mice. Elevated liver-derived alanine aminotransferase, glutamate dehydrogenase and alkaline phosphatase activities were also observed in plasma from HRN? mice. When treated orally with diclofenac for 7 days, at 30 mg/kg/day, the severities of the abnormal liver histopathology and plasma liver enzyme findings in HRN? mice were reduced markedly. Oral diclofenac administration did not alter the liver histopathology or elevate plasma enzyme activities of WT mice. These findings indicate that HRN? mice are valuable for exploration of the role played by hepatic P450s in drug biotransformation, but poorly suited to investigations of drug-induced liver toxicity. Nevertheless, studies in HRN? mice could provide novel insights into the role played by inflammation in liver injury and may aid the evaluation of new strategies for its treatment.  相似文献   
48.
49.
Analyzing functional species’ characteristics (species traits) that represent physiological, life history and morphological characteristics of species help understanding the impacts of various stressors on aquatic communities at field conditions. This research aimed to study the combined effects of pesticides and other environmental factors (temperature, dissolved oxygen, dissolved organic carbon, floating macrophytes cover, phosphate, nitrite, and nitrate) on the trait modality distribution of aquatic macrofauna communities. To this purpose, a field inventory was performed in a flower bulb growing area of the Netherlands with significant variation in pesticides pressures. Macrofauna community composition, water chemistry parameters and pesticide concentrations in ditches next to flower bulb fields were determined. Trait modalities of nine traits (feeding mode, respiration mode, locomotion type, resistance form, reproduction mode, life stage, voltinism, saprobity, maximum body size) likely to indicate pesticides impacts were analyzed. According to a redundancy analysis, phosphate -and not pesticides- constituted the main factor structuring the trait modality distribution of aquatic macrofauna. The functional composition could be ascribed for 2–4 % to pesticides, and for 3–11 % to phosphate. The lack of trait responses to pesticides may indicate that species may have used alternative strategies to adapt to ambient pesticides stress. Biomass of animals exhibiting trait modalities related to feeding by predation and grazing, presence of diapause form or dormancy, reproduction by free clutches and ovoviviparity, life stage of larvae and pupa, was negatively correlated to the concentration of phosphate. Hence, despite the high pesticide pollution in the area, variation in nutrient-related stressors seems to be the dominant driver of the functional composition of aquatic macrofauna assembly in agricultural ditches.  相似文献   
50.
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