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   38266篇
  免费   3587篇
  国内免费   2660篇
  2023年   417篇
  2022年   405篇
  2021年   1414篇
  2020年   1151篇
  2019年   1396篇
  2018年   1354篇
  2017年   970篇
  2016年   1447篇
  2015年   2348篇
  2014年   2644篇
  2013年   2893篇
  2012年   3485篇
  2011年   3228篇
  2010年   1931篇
  2009年   1712篇
  2008年   2085篇
  2007年   1862篇
  2006年   1663篇
  2005年   1360篇
  2004年   1280篇
  2003年   1097篇
  2002年   995篇
  2001年   812篇
  2000年   741篇
  1999年   670篇
  1998年   369篇
  1997年   365篇
  1996年   322篇
  1995年   296篇
  1994年   317篇
  1993年   232篇
  1992年   385篇
  1991年   343篇
  1990年   278篇
  1989年   258篇
  1988年   219篇
  1987年   172篇
  1986年   160篇
  1985年   172篇
  1984年   154篇
  1983年   114篇
  1982年   100篇
  1981年   63篇
  1980年   66篇
  1979年   92篇
  1978年   77篇
  1977年   63篇
  1976年   74篇
  1975年   68篇
  1974年   77篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
Brucella cell surface protein (BCSP31) is potentially useful for diagnosing brucellosis. We aimed to establish a monoclonal antibody (MAb) against Brucella melitensis BCSP31 and to investigate its distribution in diagnosis. Soluble recombinant BCSP31 was successfully expressed and purified. Two MAbs (1F1 and 1E5) against B. melitensis BCSP31, effective in detecting both recombinant and cellular proteins, were obtained and characterized. The MAbs did not react with Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Mycobacterium tuberculosis, or Bacillus aeruginosus, but strongly reacted with BCSP31 and B. melitensis by ELISA and Western blot analysis. We also tested different Brucella species and brucellosis using the prepared anti-BCSP31 MAbs. BCSP31 and anti-BCSP31 MAbs may play important roles in future research in diagnosing brucellosis.  相似文献   
13.
Prior studies of upper gastrointestinal bleeding (UGIB) and acute myocardial infarction (AMI) are small, and long-term effects of UGIB on AMI have not been delineated. We investigated whether UGIB in patients diagnosed with coronary artery disease (CAD) increased their risk of subsequent AMI. This was a population-based, nested case-control study using Taiwan’s National Health Insurance Research Database. After propensity-score matching for age, gender, comorbidities, CAD date, and follow-up duration, we identified 1,677 new-onset CAD patients with AMI (AMI[+]) between 2001 and 2006 as the case group and 10,062 new-onset CAD patients without (AMI[−]) as the control group. Conditional logistic regression was used to examine the association between UGIB and AMI. Compared with UGIB[−] patients, UGIB[+] patients had twice the risk for subsequent AMI (adjusted odds ratio [AOR] = 2.08; 95% confidence interval [CI], 1.72–2.50). In the subgroup analysis for gender and age, UGIB[+] women (AOR = 2.70; 95% CI, 2.03–3.57) and patients < 65 years old (AOR = 2.23; 95% CI, 1.56–3.18) had higher odds of an AMI. UGIB[+] AMI[+] patients used nonsignificantly less aspirin than did UGIB[−] AMI[+] patients (27.69% vs. 35.61%, respectively). UGIB increased the risk of subsequent AMI in CAD patients, especially in women and patients < 65. This suggests that physicians need to use earlier and more aggressive intervention to detect UGIB and prevent AMI in CAD patients.  相似文献   
14.
15.
16.
17.
For the development of “medical foods” and/or botanical drugs as defined USA FDA, clear and systemic characterizations of the taxonomy, index phytochemical components, and the functional or medicinal bioactivities of the reputed or candidate medicinal plant are needed. In this study, we used an integrative approach, including macroscopic and microscopic examination, marker gene analysis, and chemical fingerprinting, to authenticate and validate various species/varieties of Wedelia, a reputed medicinal plant that grows naturally and commonly used in Asian countries. The anti-inflammatory bioactivities of Wedelia extracts were then evaluated in a DSS-induced murine colitis model. Different species/varieties of Wedelia exhibited distinguishable morphology and histological structures. Analysis of the ribosomal DNA internal transcribed spacer (ITS) region revealed significant differences among these plants. Chemical profiling of test Wedelia species demonstrated candidate index compounds and distinguishable secondary metabolites, such as caffeic acid derivatives, which may serve as phytochemical markers or index for quality control and identification of specific Wedelia species. In assessing their effect on treating DSS induced-murine colitis, we observed that only the phytoextract from W. chinensis species exhibited significant anti-inflammatory bioactivity on DSS-induced murine colitis among the various Wedelia species commonly found in Taiwan. Our results provide a translational research approach that may serve as a useful reference platform for biotechnological applications of traditional phytomedicines. Our findings indicate that specific Wedelia species warrant further investigation for potential treatment of human inflammatory bowel disease.  相似文献   
18.
19.
20.
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