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   7319篇
  免费   424篇
  国内免费   32篇
耳鼻咽喉   79篇
儿科学   280篇
妇产科学   160篇
基础医学   687篇
口腔科学   177篇
临床医学   569篇
内科学   1647篇
皮肤病学   172篇
神经病学   487篇
特种医学   184篇
外科学   1541篇
综合类   117篇
一般理论   2篇
预防医学   273篇
眼科学   220篇
药学   617篇
中国医学   34篇
肿瘤学   529篇
  2024年   4篇
  2023年   69篇
  2022年   140篇
  2021年   379篇
  2020年   210篇
  2019年   258篇
  2018年   359篇
  2017年   230篇
  2016年   284篇
  2015年   256篇
  2014年   405篇
  2013年   451篇
  2012年   735篇
  2011年   689篇
  2010年   385篇
  2009年   350篇
  2008年   414篇
  2007年   439篇
  2006年   373篇
  2005年   318篇
  2004年   233篇
  2003年   183篇
  2002年   140篇
  2001年   36篇
  2000年   36篇
  1999年   33篇
  1998年   25篇
  1997年   25篇
  1996年   21篇
  1995年   17篇
  1994年   13篇
  1993年   15篇
  1992年   39篇
  1991年   31篇
  1990年   17篇
  1989年   16篇
  1988年   14篇
  1987年   20篇
  1986年   15篇
  1985年   22篇
  1984年   11篇
  1983年   9篇
  1982年   5篇
  1981年   8篇
  1980年   4篇
  1979年   9篇
  1978年   4篇
  1977年   10篇
  1976年   4篇
  1974年   3篇
排序方式: 共有7775条查询结果,搜索用时 15 毫秒
81.
82.
A 61‐year‐old man presented with unstable angina 16 years after undergoing coronary artery bypass grafting with a left internal mammary artery graft to the left anterior descending coronary artery and a sequential saphenous vein graft (SVG) to the right coronary artery and an obtuse marginal branch. Transthoracic echocardiography (TTE) with a Philips iE33 machine and an S5 transducer revealed a 5.3 cm × 4.6 cm mass with a central echolucent area, surrounded by a peripheral zone of increased echodensity adjacent to, and partially compressing, the right atrium. Contrast echocardiography following an intravenous bolus injection of Definity revealed late appearance of contrast within the mass consistent with a giant SVG aneurysm. Coronary artery bypass graft angiography revealed a giant aneurysm in the SVG proximal to the RCA anastomosis; the distal limb of the graft to the obtuse marginal branch was occluded. Under intravascular ultrasound guidance, a 7‐mm spider filter was placed in the distal graft; then, a 6 mm × 10 cm Viabahn self‐expanding nitinol polyethylene terephthalate‐covered stent was deployed in the SVG with good seal zones proximally and distally. A follow‐up contrast‐enhanced transthoracic echocardiogram 1 day postprocedure revealed partial thrombosis of the aneurysm cavity. Ultrasound contrast did not appear in the aneurysm following intravenous injection, consistent with complete exclusion from the systemic circulation. This is the first report demonstrating feasibility of contrast‐enhanced transthoracic echocardiography for the diagnosis of SVG aneurysm and confirming procedural success by documenting exclusion from the systemic circulation following intervention.  相似文献   
83.
84.

Background

Recent trends have identified increasing number of young individuals with rectal and colon cancers. These individuals, who are younger than 50 years old, in most instances would not meet screening guidelines. We aimed to report the characteristics and trend of the rising proportion of young individuals being diagnosed with rectal and colon cancers at our institutions.

Patients and Methods

This study included 3381 rectal and colon cancer patients from the Mayo Clinic cancer registry from 1972 to 2017 who were diagnosed with rectal or colon cancer and who were < 50 years old. Patient and cancer characteristics are described. The Cochran-Armitage trend test was used to see if the change in percentage diagnosed at age < 50 years had a significant trend over the years. A linear regression model was fit to estimate the percentage change per year when the trend was approximately linear.

Results

The percentage of patients diagnosed with rectal or colon cancer in different age categories over the years showed a rising trend for individuals aged < 50. Most of these tumors were distal (rectum, left-sided colon, and right-sided colon were 49.8%, 28.8%, and 21.4%, respectively). This was more so for patients < 50 diagnosed with rectal cancer, which showed a linear increase at a rate of 0.26% per year (P < .001).

Conclusion

Our study affirms the rising proportion of colorectal cancers found in young individuals, with a linear ongoing rise of rectal cancers in particular. This may have implications for the current screening recommendations for colorectal cancers, which are already being revised.  相似文献   
85.
Available urban health metrics focus primarily on large area rankings. Less has been done to develop an index that provides information about level of health and health disparities for small geographic areas. Adopting a method used by the Human Development Index, we standardized indicators for small area units on a (0, 1) interval and combined them using their geometric mean to form an Urban Health Index (UHI). Disparities were assessed using the ratio of the highest to lowest decile and measurement of the slope of the eight middle deciles (middle; 80 %) of the data. We examined the sensitivity of the measure to weighting, to changes in the method, to correlation among indicators, and to substitution of indicators. Using seven health determinants and applying these methods to the 128 census tracts in the city of Atlanta, USA, we found a disparity ratio of 5.92 and a disparity slope of 0.54, suggesting substantial inequality and heterogeneity of risk. The component indicators were highly correlated; their systematic removal had a small effect on the results. Except in extreme cases, weighting had a little effect on the rankings. A map of Atlanta census tracts exposed a swath of high disparity. UHI rankings, ratio, and slope were resistant to alteration in composition and to non-extreme weighting schemes. This empirical evaluation was limited to a single realization, but suggests that a flexible tool, whose method rather than content is standardized, may be of use for local evaluation, for decision making, and for area comparison.  相似文献   
86.
87.
88.
89.
90.
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