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   2393篇
  免费   133篇
  国内免费   1篇
  2023年   24篇
  2022年   38篇
  2021年   73篇
  2020年   40篇
  2019年   42篇
  2018年   56篇
  2017年   46篇
  2016年   67篇
  2015年   106篇
  2014年   131篇
  2013年   145篇
  2012年   208篇
  2011年   180篇
  2010年   108篇
  2009年   76篇
  2008年   120篇
  2007年   108篇
  2006年   105篇
  2005年   101篇
  2004年   94篇
  2003年   90篇
  2002年   77篇
  2001年   31篇
  2000年   33篇
  1999年   22篇
  1998年   15篇
  1997年   18篇
  1996年   17篇
  1995年   14篇
  1994年   9篇
  1993年   13篇
  1992年   25篇
  1991年   26篇
  1990年   29篇
  1989年   13篇
  1988年   14篇
  1987年   10篇
  1986年   12篇
  1985年   17篇
  1984年   12篇
  1983年   12篇
  1982年   8篇
  1981年   12篇
  1980年   13篇
  1979年   17篇
  1978年   11篇
  1975年   9篇
  1974年   17篇
  1973年   9篇
  1971年   7篇
排序方式: 共有2527条查询结果,搜索用时 15 毫秒
1.
Studies of HIV prevention interventions such as pre-exposure prophylaxis (PREP) and circumcision in India are limited. The present study sought to investigate Indian truck-drivers initial commitment to PREP and circumcision utilizing the AIDS Risk Reduction Model. Ninety truck-drivers completed an in-depth qualitative interview and provided a blood sample for HIV and HSV-2 testing. Truck-drivers exhibited low levels of initial commitment towards PREP and even lower for circumcision. However, potential leverage points for increasing commitment were realized in fear of infecting family rather than self, self-perceptions of risk, and for PREP focusing on cultural beliefs towards medication and physicians. Cost was a major barrier to both HIV prevention interventions. Despite these barriers, our findings suggest that the ARRM may be useful in identifying several leverage points that may be used by peers, health care providers and public health field workers to enhance initial commitment to novel HIV prevention interventions in India.  相似文献   
2.
3.
4.
Epidemiological studies have shown an increased obesity-related risk of asthma. In support, obese mice develop airway hyperresponsiveness (AHR). However, it remains unclear whether the increased risk is a consequence of obesity, adipogenic diet, or the metabolic syndrome (MetS). Altered L-arginine and nitric oxide (NO) metabolism is a common feature between asthma and metabolic syndrome that appears independent of body mass. Increased asthma risk resulting from such metabolic changes would have important consequences in global health. Since high-sugar diets can induce MetS, without necessarily causing obesity, studies of their effect on arginine/NO metabolism and airway function could clarify this aspect. We investigated whether normal-weight mice with MetS, due to high-fructose diet, had dysfunctional arginine/NO metabolism and features of asthma. Mice were fed chow-diet, high-fat-diet, or high-fructose-diet for 18 weeks. Only the high-fat-diet group developed obesity or adiposity. Hyperinsulinemia, hyperglycaemia, and hyperlipidaemia were common to both high-fat-diet and high-fructose-diet groups and the high-fructose-diet group additionally developed hypertension. At 18 weeks, airway hyperresponsiveness (AHR) could be seen in obese high-fat-diet mice as well as non-obese high-fructose-diet mice, when compared to standard chow-diet mice. No inflammatory cell infiltrate or goblet cell metaplasia was seen in either high-fat-diet or high-fructose-diet mice. Exhaled NO was reduced in both these groups. This reduction in exhaled NO correlated with reduced arginine bioavailability in lungs. In summary, mice with normal weight but metabolic obesity show reduced arginine bioavailability, reduced NO production, and asthma-like features. Reduced NO related bronchodilation and increased oxo-nitrosative stress may contribute to the pathogenesis.  相似文献   
5.
6.
This report demonstrates the stability of NBT substrate after multiple exposures to alkaline phosphatase. Perhaps more important than the ability to reuse substrates, the report provides some insight into the mechanisms by which tetrazoliums are reduced and evidence for the formation of an intermediary product, i.e., a half-formazan that is reduced more rapidly. (J Histochem Cytochem 49:1189-1190, 2001)  相似文献   
7.
R Kaul  M J Duncan  J Guest  W M Wenman 《Gene》1990,87(1):97-103
The major outer membrane protein (MOMP)-encoding gene (omp1) of Chlamydia trachomatis has been cloned into Escherichia coli and partially sequenced. This recombinant gene expresses a full-length 40-kDa product, which is recognized by a monoclonal antibody directed against the species-specific epitope of MOMP. The recombinant omp1 is expressed in either insertion orientation, indicating that it utilizes its own promoter system. The endogenous omp1 promoter possesses a relatively low activity despite the high level of MOMP expression. Deletion of a 520-bp fragment at the 3' end encoding 39 amino acids (aa) at the C terminus and the remainder of the noncoding region leads to a significant decrease in mRNA stability and loss of protein synthesis. When the MOMP-encoding plasmid was introduced into E. coli minicells, it expressed 40- and 43-kDa proteins; however, inhibition of post-translational processing by ethanol revealed only a 43-kDa protein. These data indicate that the unprocessed omp1 gene product contains a 22-aa leader sequence which is cleaved during translocation to the outer membrane, to yield a processed 40-kDa protein. The recombinant MOMP was localized to the outer membrane E. coli fraction, comparable to the location of the native C. trachomatis protein.  相似文献   
8.
Summary In the absence of an organic solvent, a buffer to enzyme weight ratio of 1 gives maximum selectivity to interesterification over hydrolysis in a lipase-catalyzed mixture of triacetin and tributyrin. Addition of hexane enhances interesterification as does a reversed micelle configuration.  相似文献   
9.
10.
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