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   4126篇
  免费   339篇
  国内免费   97篇
耳鼻咽喉   16篇
儿科学   16篇
妇产科学   23篇
基础医学   205篇
口腔科学   83篇
临床医学   205篇
内科学   199篇
皮肤病学   25篇
神经病学   87篇
特种医学   213篇
外科学   196篇
综合类   471篇
预防医学   434篇
眼科学   31篇
药学   1216篇
中国医学   1055篇
肿瘤学   87篇
  2023年   50篇
  2022年   95篇
  2021年   108篇
  2020年   116篇
  2019年   84篇
  2018年   98篇
  2017年   91篇
  2016年   127篇
  2015年   102篇
  2014年   259篇
  2013年   294篇
  2012年   319篇
  2011年   381篇
  2010年   258篇
  2009年   226篇
  2008年   244篇
  2007年   232篇
  2006年   172篇
  2005年   159篇
  2004年   123篇
  2003年   111篇
  2002年   86篇
  2001年   89篇
  2000年   58篇
  1999年   55篇
  1998年   51篇
  1997年   41篇
  1996年   38篇
  1995年   42篇
  1994年   42篇
  1993年   35篇
  1992年   30篇
  1991年   27篇
  1990年   11篇
  1989年   13篇
  1988年   11篇
  1987年   11篇
  1985年   21篇
  1984年   23篇
  1983年   23篇
  1982年   13篇
  1981年   16篇
  1980年   20篇
  1979年   22篇
  1978年   16篇
  1977年   18篇
  1976年   14篇
  1975年   11篇
  1974年   16篇
  1973年   15篇
排序方式: 共有4562条查询结果,搜索用时 31 毫秒
71.
《Substance use & misuse》2013,48(2):197-205
The contextual differentiation of beverage specific consumption is examined in a metropolitan area household survey of current drinkers. The findings indicate that beverage specific consumption is related to such structural proportions as presence/absence of food, drinking location, type of companion, and duration. Wine, for example, is frequently associated with mealtimes, at home, and with relatives.  相似文献   
72.
Bony fishes represent the largest vertebrate class and are a very diverse animal group. This chapter provides a thorough review of the available scientific literature on the thyroid system in these important vertebrate animals. The molecular components of the hypothalamic-pituitary-thyroid (HPT) axis in this group correspond closely to those of mammals. The thyroid tissue in the fishes is organized as diffuse follicles, with a few exceptions, rather than as an encapsulated gland as is found in most other vertebrate species. The features of this diffuse tissue in fishes are reviewed with an emphasis on feedback relationships within the HPT axis, the molecular biology of the thyroid system in fishes, and comparisons versus the thyroid systems of other vertebrate taxa. A review of the role of thyroid hormone in fish development and reproduction is included. Available information about the HPT axis in fishes is quite detailed for some species and rather limited or absent in others. This review focuses on species that have been intensively studied for their value as laboratory models in assays to investigate disruption in normal function of the thyroid system. In addition, in vitro and in vivo assay methods for screening chemicals for their potential to interfere with the thyroid system are reviewed. It is concluded that there are currently no in vitro or in vivo assays in fish species that are sufficiently developed to warrant recommendation for use to efficiently screen chemicals for thyroid disruption. Methods are available that can be used to measure thyroid hormones, although our ability to interpret the causes and implications of potential alterations in T4 or T3 levels in fishes is nonetheless limited without further research.  相似文献   
73.
Astrocytes are reported to have critical functions in ischemic brain injury including protective effects against ischemia-induced neuronal dysfunction. Na-K ATPase maintains ionic gradients in astrocytes and is suggested as an indicator of ischemic injury in glial cells. Here, we examined the role of the Na-K ATPase in the pathologic process of ischemic injury of primary cultured astrocytes. Chemical ischemia was induced by sodium azide and glucose deprivation. Lactate dehydrogenase assays showed that the cytotoxic effect of chemical ischemia on astrocytes began to appear at 2 h of ischemia. The expression of Na-K ATPase α1 subunit protein was increased at 2 h of chemical ischemia and was decreased at 6 h of ischemia, whereas the expression of α1 subunit mRNA was not changed by chemical ischemia. Na-K ATPase activity was time-dependently decreased at 1, 3, and 6 h of chemical ischemia, whereas the enzyme activity was temporarily recovered to the control value at 2 h of chemical ischemia. Cytotoxicity at 2 h of chemical ischemia was significantly blocked by reoxygenation for 24 h following ischemia. Reoxygenation following chemical ischemia for 1 h significantly increased the activity of the Na-K ATPase, while reoxygenation following ischemia for 2 h slightly decreased the enzyme activity. These results suggest that the critical time for ischemia-induced cytotoxicity of astrocytes might be 2 h after the initiation of ischemic insult and that the increase in the expression and activity of the Na-K ATPase might play a protective role during ischemic injury of astrocytes.  相似文献   
74.
75.
Ataluren is an aromatic acid derivative with a 1,2,4-oxodiazole moiety. Ataluren-O-1β-acyl glucuronide is a prominent circulatory metabolite in mice, rats, dogs, and humans following oral administration of ataluren. The objective of this paper was to evaluate the stability in vitro and in vivo of ataluren-O-1β-acyl glucuronide metabolite. Ultrahigh performance liquid chromatography-mass spectrometry methods were developed to separate and monitor ataluren-O-1β-acyl glucuronide and its possible migration isomers. In vitro stability was assessed in phosphate buffered saline as well as in control rat and human plasma. The disappearance of ataluren-O-1β-acyl glucuronide and the formation of migration isomers were monitored by the ultrahigh performance liquid chromatography-mass spectrometry methods. In vitro, ataluren-O-1β-acyl glucuronide underwent isomerization with an estimated half-life of approximately 1 h. However, ataluren-O-1β-acyl glucuronide was stable and was the only detectable acyl glucuronide following oral administration of ataluren in mice, rats, dogs, and humans using the same analytical methods. Ataluren acyl glucuronide in mouse, rat, dog, and human plasma could be hydrolyzed by β-glucuronidase, further confirming the structure of O-1β-acyl glucuronide. These results demonstrated that ataluren-O-1β-acyl glucuronide did not undergo migration in vivo. No clinical safety concern related to ataluren-O-1β-acyl glucuronide migration has been detected.  相似文献   
76.
77.
目的 观察脂肪乳对血液细胞分析结果的影响.方法 在体外将健康志愿者血液样本以及生理盐水与一定比例的脂肪乳混合,配制系列浓度的血液/脂肪乳混合液以及生理盐水/脂肪乳混合液,于血液细胞分析仪上进行测试,观察不同浓度脂肪乳对CBC参数、Diff分类参数的影响.结果 随着脂肪乳浓度的增高,血液/脂肪乳混合液的CBC参数测定值渐进升高,Diff分类参数中的淋巴细胞分类比例呈下降趋势而单核细胞比例逐渐增高;而生理盐水/脂肪乳混合液中白细胞、血红蛋白和PLT-O明显升高.结论 脂肪乳会对血液细胞分析仪多个参数的测定产生影响,可以通过测定结果的一些特征筛选可疑含脂肪乳标本.  相似文献   
78.
79.
The goal of public health is to promote the best possible health for the whole population. Public health issues are numerous and can be unbelievably complex in form, scope, and possible consequence. Most public health decisions involve assessing several different options, weighing the respective benefits and risks of those options, and making difficult decisions that hopefully provide the greatest benefit to the affected populations. Many risk management decisions involve a variety of societal factors which modify risk assessment choices. The purpose of this paper is to point out difficulties in making decisions that impact public health. The intent of such decisions is to improve public health, but as illustrated in the paper, there can be unintended adverse consequences. Such unplanned issues require continued attention and efforts for responsible officials in the protection of environmental public health. This article presents examples of such events, when in the past, it was necessary to assess and regulate a number of potentially hazardous chemicals commonly used as insecticides, gasoline additives, and wood preservatives.  相似文献   
80.
Photodynamic therapy (PDT) has been successfully employed in the treatment of oral cancer. Toluidine blue O (TBO) is a photosensitizer (PS) that has exhibited remarkable photocytotoxicity in a variety of tumour cells; however, its physicochemical properties, as well as the physicochemical properties of oral mucosa, prevent the drug from reaching the target site at a therapeutic concentration.The aim of this study was to evaluate the influence of Tween 80® (TW), which has shown potential as a penetration enhancer, on the mucosal retention of TBO for the PDT of oral cancer. 4% Chitosan-based mucoadhesive gels (CH gels) containing or not 5%TW were prepared (both containing 1%TBO), and their physicochemical properties (pH, rheology and mucoadhesion), TBO in vitro release profiles and TBO in vitro mucosal retention were evaluated. In vivo mucosal penetration studies of TBO followed by laser exposition were also carried out.The results showed that 4%CH gels containing 5%TW and 1%TBO have adequate mucoadhesive and rheological properties for oral mucosa use, although they present a slightly acid pH. TBO release studies showed that TW reduces TBO release, but it prolongs TBO release and increases TBO retention in the mucosa. In vivo studies showed that 4%CH gels containing 5%TW and 1%TBO cause an increase in the number of apoptotic cell, after laser exposition.In summary, 4%CH gels containing 5%TW may be a promising vehicle to optimize the penetration of TBO in oral mucosa and to improve the PDT response for the treatment of oral cancer.  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