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   7227篇
  免费   686篇
  国内免费   67篇
  2023年   51篇
  2022年   48篇
  2021年   175篇
  2020年   132篇
  2019年   183篇
  2018年   193篇
  2017年   201篇
  2016年   249篇
  2015年   423篇
  2014年   406篇
  2013年   532篇
  2012年   625篇
  2011年   571篇
  2010年   406篇
  2009年   367篇
  2008年   446篇
  2007年   378篇
  2006年   350篇
  2005年   298篇
  2004年   317篇
  2003年   236篇
  2002年   241篇
  2001年   86篇
  2000年   63篇
  1999年   56篇
  1998年   50篇
  1997年   53篇
  1996年   39篇
  1995年   44篇
  1994年   44篇
  1993年   46篇
  1992年   39篇
  1991年   43篇
  1990年   45篇
  1989年   46篇
  1988年   25篇
  1987年   28篇
  1986年   33篇
  1985年   37篇
  1984年   31篇
  1983年   24篇
  1982年   30篇
  1981年   23篇
  1980年   21篇
  1979年   20篇
  1978年   18篇
  1977年   15篇
  1976年   16篇
  1975年   18篇
  1973年   15篇
排序方式: 共有7980条查询结果,搜索用时 31 毫秒
1.
2.
BackgroundSeveral prior studies have found an association between statin use and reduced risk of colorectal cancer. We hypothesized that these findings may be due to systematic bias and examined the independent association of colorectal cancer risk with statin use, serum cholesterol, and change in cholesterol concentration.ConclusionsAlthough the risk of colorectal cancer was lower in statin users versus nonusers, no difference was observed among those who continued versus discontinued statin therapy, suggesting the potential for indication bias. The association between decreased serum cholesterol and colorectal cancer risk suggests a cholesterol-lowering effect of undiagnosed malignancy. Clinical judgment should be used when considering causes of cholesterol reduction in patients, including those on statin therapy.  相似文献   
3.
4.
A finite element model of cell deformation during magnetic bead twisting.   总被引:2,自引:0,他引:2  
Magnetic twisting cytometry probes mechanical properties of an adherent cell by applying a torque to a magnetic bead that is tightly bound to the cell surface. Here we have used a three-dimensional finite element model of cell deformation to compute the relationships between the applied torque and resulting bead rotation and lateral bead translation. From the analysis, we computed two coefficients that allow the cell elastic modulus to be estimated from measurements of either bead rotation or lateral bead translation, respectively, if the degree of bead embedding and the cell height are known. Although computed strains in proximity of the bead can be large, the relationships between applied torque and bead rotation or translation remain virtually linear up to bead rotations of 15 degrees, above which geometrical nonlinearities become significant. This appreciable linear range stands in contrast to the intrinsically nonlinear force-displacement relationship that is observed when cells are indented during atomic force microscopy. Finally, these computations support the idea that adhesive forces are sufficient to keep the bead firmly attached to the cell surface throughout the range of working torques.  相似文献   
5.
BackgroundOut-of-hospital cardiac arrest (OHCA) remains a major public health issue and research has shown that large regional variation in outcomes exists. Of the interventions associated with survival, the provision of bystander CPR is one of the most important modifiable factors. The aim of this study is to identify census areas with high incidence of OHCA and low rates of bystander CPR in Victoria, AustraliaMethodsWe conducted an observational study using prospectively collected population-based OHCA data from the state of Victoria in Australia. Using ArcGIS (ArcMap 10.0), we linked the location of the arrest using the dispatch coordinates (longitude and latitude) to Victorian Local Government Areas (LGAs). We used Bayesian hierarchical models with random effects on each LGA to provide shrunken estimates of the rates of bystander CPR and the incidence rates.ResultsOver the study period there were 31,019 adult OHCA attended, of which 21,436 (69.1%) cases were of presumed cardiac etiology. Significant variation in the incidence of OHCA among LGAs was observed. There was a 3 fold difference in the incidence rate between the lowest and highest LGAs, ranging from 38.5 to 115.1 cases per 100,000 person-years. The overall rate of bystander CPR for bystander witnessed OHCAs was 62.4%, with the rate increasing from 56.4% in 2008–2010 to 68.6% in 2010–2013. There was a 25.1% absolute difference in bystander CPR rates between the highest and lowest LGAs.ConclusionSignificant regional variation in OHCA incidence and bystander CPR rates exists throughout Victoria. Regions with high incidence and low bystander CPR participation can be identified and would make suitable targets for interventions to improve CPR participation rates.  相似文献   
6.
7.
8.
9.
10.
A maize acetyl-coenzyme A carboxylase cDNA sequence.   总被引:5,自引:0,他引:5       下载免费PDF全文
  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