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   8758篇
  免费   700篇
  国内免费   11篇
耳鼻咽喉   71篇
儿科学   150篇
妇产科学   280篇
基础医学   1006篇
口腔科学   110篇
临床医学   896篇
内科学   2152篇
皮肤病学   196篇
神经病学   889篇
特种医学   240篇
外科学   1238篇
综合类   131篇
一般理论   2篇
预防医学   751篇
眼科学   359篇
药学   552篇
中国医学   2篇
肿瘤学   444篇
  2021年   134篇
  2020年   67篇
  2019年   155篇
  2018年   166篇
  2017年   86篇
  2016年   112篇
  2015年   114篇
  2014年   216篇
  2013年   301篇
  2012年   413篇
  2011年   451篇
  2010年   257篇
  2009年   201篇
  2008年   331篇
  2007年   437篇
  2006年   375篇
  2005年   375篇
  2004年   363篇
  2003年   337篇
  2002年   323篇
  2001年   296篇
  2000年   319篇
  1999年   253篇
  1998年   84篇
  1997年   61篇
  1996年   61篇
  1995年   61篇
  1994年   67篇
  1992年   160篇
  1991年   156篇
  1990年   209篇
  1989年   158篇
  1988年   179篇
  1987年   159篇
  1986年   181篇
  1985年   154篇
  1984年   102篇
  1983年   102篇
  1982年   68篇
  1980年   72篇
  1979年   138篇
  1978年   90篇
  1977年   79篇
  1976年   75篇
  1975年   66篇
  1974年   64篇
  1973年   69篇
  1972年   75篇
  1971年   66篇
  1968年   62篇
排序方式: 共有9469条查询结果,搜索用时 31 毫秒
1.
2.
3.
There is conflicting clinical evidence whether administration of coenzyme Q10 (CoQ10) improves function following coronary artery bypass graft surgery (CABG). Using a swine model of hibernating myocardium, we tested whether daily CoQ10 would improve contractile function by MRI at 4-week post-CABG. Twelve pigs underwent a thoracotomy and had a constrictor placed on the left anterior descending (LAD). At 12 weeks, they underwent off-pump bypass and received daily dietary supplements of either CoQ10 (10 mg/kg/day) or placebo. At 4-week post-CABG, circumferential strain measurements in the hibernating LAD region from placebo and CoQ10 groups were not different and increased to a similar extent with dobutamine (?14.7?±?0.6 versus ?14.8?±?0.1, respectively (NS)). Post-sacrifice, oxidant stress markers were obtained in the mitochondrial isolates and protein carbonyl in the placebo, and CoQ10 groups were 6.14?±?0.36 and 5.05?±?0.32 nmol/mg, respectively (NS). In summary, CoQ10 did not improve contractile reserve or reduce oxidant stress at 4-week post-CABG.  相似文献   
4.
The Lyme disease spirochete, Borrelia burgdorferi, expresses RevA and numerous outer surface lipoproteins during mammalian infection. As an adhesin that promotes bacterial interaction with fibronectin, RevA is poised to interact with the extracellular matrix of the host. To further define the role(s) of RevA during mammalian infection, we created a mutant that is unable to produce RevA. The mutant was still infectious to mice, although it was significantly less well able to infect cardiac tissues. Complementation of the mutant with a wild-type revA gene restored heart infectivity to wild-type levels. Additionally, revA mutants led to increased evidence of arthritis, with increased fibrotic collagen deposition in tibiotarsal joints. The mutants also induced increased levels of the chemokine CCL2, a monocyte chemoattractant, in serum, and this increase was abolished in the complemented strain. Therefore, while revA is not absolutely essential for infection, deletion of revA had distinct effects on dissemination, arthritis severity, and host response.  相似文献   
5.
6.
Interval breast cancers (those diagnosed between recommended mammography screens) generally have poorer outcomes and are more common among women with dense breasts. We aimed to develop a risk model for interval breast cancer. We conducted a nested case–control study within the Melbourne Collaborative Cohort Study involving 168 interval breast cancer patients and 498 matched control subjects. We measured breast density using the CUMULUS software. We recorded first-degree family history by questionnaire, measured body mass index (BMI) and calculated age-adjusted breast tissue aging, a novel measure of exposure to estrogen and progesterone based on the Pike model. We fitted conditional logistic regression to estimate odds ratio (OR) or odds ratio per adjusted standard deviation (OPERA) and calculated the area under the receiver operating characteristic curve (AUC). The stronger risk associations were for unadjusted percent breast density (OPERA = 1.99; AUC = 0.66), more so after adjusting for age and BMI (OPERA = 2.26; AUC = 0.70), and for family history (OR = 2.70; AUC = 0.56). When the latter two factors and their multiplicative interactions with age-adjusted breast tissue aging (p = 0.01 and 0.02, respectively) were fitted, the AUC was 0.73 (95% CI 0.69–0.77), equivalent to a ninefold interquartile risk ratio. In summary, compared with using dense breasts alone, risk discrimination for interval breast cancers could be doubled by instead using breast density, BMI, family history and hormonal exposure. This would also give women with dense breasts, and their physicians, more information about the major consequence of having dense breasts—an increased risk of developing an interval breast cancer.  相似文献   
7.
8.
There is growing evidence indicating that a lack of perceived containment, or youth's beliefs about whether adults can control their behavior, is associated with problem behavior. However, little research has examined factors that may contribute to perceived containment, which would be helpful in further tailoring prevention and intervention efforts for problem behavior. The current study evaluated associations between callous-unemotional (C/U) traits, peer delinquency, neighborhood problems, and perceived containment. Associations were examined using a sample of detained youth. Findings indicated that while all three factors were correlated with perceived containment, only C/U traits (particularly the callousness and uncaring subscales) and peer delinquency were uniquely associated with perceived containment. Further, C/U traits did not moderate the links between peer delinquency or neighborhood problems and perceived containment. This study supports the influence of both individual and contextual factors on perceived containment, suggesting multiple factors to target for prevention and intervention.  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