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   56479篇
  免费   4720篇
  国内免费   48篇
  61247篇
  2023年   202篇
  2022年   585篇
  2021年   1009篇
  2020年   557篇
  2019年   747篇
  2018年   1143篇
  2017年   895篇
  2016年   1570篇
  2015年   2601篇
  2014年   2890篇
  2013年   3380篇
  2012年   4360篇
  2011年   4168篇
  2010年   2651篇
  2009年   2327篇
  2008年   3347篇
  2007年   3107篇
  2006年   2839篇
  2005年   2569篇
  2004年   2509篇
  2003年   2236篇
  2002年   1906篇
  2001年   1650篇
  2000年   1539篇
  1999年   1219篇
  1998年   532篇
  1997年   470篇
  1996年   402篇
  1995年   395篇
  1994年   306篇
  1993年   299篇
  1992年   642篇
  1991年   516篇
  1990年   476篇
  1989年   480篇
  1988年   406篇
  1987年   391篇
  1986年   318篇
  1985年   330篇
  1984年   270篇
  1983年   227篇
  1982年   192篇
  1981年   163篇
  1980年   160篇
  1979年   223篇
  1978年   197篇
  1977年   179篇
  1976年   173篇
  1974年   198篇
  1972年   158篇
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
81.
82.
83.
N.C. Lee 《CMAJ》1990,142(11):1176-1177
  相似文献   
84.
85.
The purpose of this review is to provide an overview of the effects of adenovirus and influenza virus infections on obesity in various experimental models. We reviewed studies that were conducted within the past 10 years and were related to virus infection and obesity prevalence. Here, we discuss a different causal relationship between adenovirus and influenza infections with obesity. Adenovirus infection can cause obesity, whereas obesity can be a risk factor for increasing influenza virus infection and increases the risk of morbidity and mortality. The prevalence of obesity due to adenovirus infections may be due to an increase in glucose uptake and reduction in lipolysis caused by an increase in corticosterone secretion. Adenovirus infections may lead to increases in appetite by decreasing norepinephrine and leptin levels and also cause immune dysfunction. The relationship between obesity and influenza virus infection could be summarized by the following features: decreases in memory T-cell functionality and interferon (IFN)-α, IFN-β, and IFN-γ mRNA expression, increases in viral titer and infiltration, and impaired dendritic cell function in obese individuals. Moreover, leptin resistance may play an important role in increasing influenza virus infections in obese individuals. In conclusion, prevention of adenovirus infections could be a good approach for reducing obesity prevalence, and prevention of obesity could reduce influenza virus infections from the point of view of viral infections and obesity.  相似文献   
86.
Focal animal sampling was used to determine the 24-h time budget of a takh harem stallion (Equus ferus przewalskii) during the 2 weeks prior to, and the two weeks following, reintroduction into the Hustain Nuruu Steppe Reserve, Mongolia. Both before and after release, the stallion spent approximately 47% of his time grazing, 6% standing, and 5% in recumbent rest. The biggest changes to the time budget after release were a 4-fold increase in the amount of time spent moving, and a 50% decrease in the amount of time spent resting in a standing position. During the middle of the day when the temperatures were hottest, the stallion exhibited less grazing and more standing resting behaviour than in the morning or evening hours. Recumbent rest invariably occurred in the hours before dawn.  相似文献   
87.
88.
89.
90.
Fluorescamine and trinitrobenzenesulfonate were used as chemical probes to differentially label amino phospholipids in liposomes. At low concentrations, fluorescamine reacts primarily with amino lipids on the external half of the bilayer. Further increase in fluorescamine concentration resulted in a linear increase of labeling indicating penetration and reaction with the internal half of the bilayer. Because of the pH requirements of the fluorescamine reaction, internal labeling was eliminated with a H+ gradient: inside acidic/outside alkaline. Differential labeling was also achieved with trinitrobenzenesulfonate, which is normally not permeable but which can be transported by valinomycin-K+ complex and react with internal amines. Thus, either half of the bilayer can be labeled with the same or different reagents. When liposomes were double-labeled, the fluorescence of fluorescamine was quenched by the trinitrobenzenesulfonate label. This quenching was reversed by solubilizing the liposomes with acidic ethanol. No quenching occurred when fluorescamine-labeled liposomes were mixed with trinitrobenzenesulfonate-reacted liposomes (or trinitrophenylated methylamine) suggesting close proximity of two labels is required for quenching. Conditions which promoted vesicular fusion promptly produced quenching. These differential labeling procedures can be usefully applied to quantitate aminolipids on internal and external vesicular surface, monitor vesicular fusion, and assess liposomal structure.  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