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   63558篇
  免费   4958篇
  国内免费   186篇
耳鼻咽喉   861篇
儿科学   1971篇
妇产科学   1154篇
基础医学   7995篇
口腔科学   1195篇
临床医学   7209篇
内科学   13388篇
皮肤病学   1109篇
神经病学   5683篇
特种医学   2442篇
外国民族医学   2篇
外科学   10283篇
综合类   715篇
一般理论   94篇
预防医学   5247篇
眼科学   1565篇
药学   3674篇
  3篇
中国医学   98篇
肿瘤学   4014篇
  2023年   465篇
  2022年   807篇
  2021年   1811篇
  2020年   960篇
  2019年   1555篇
  2018年   1891篇
  2017年   1316篇
  2016年   1452篇
  2015年   1593篇
  2014年   2253篇
  2013年   2779篇
  2012年   4490篇
  2011年   4576篇
  2010年   2502篇
  2009年   2184篇
  2008年   3719篇
  2007年   3668篇
  2006年   3622篇
  2005年   3401篇
  2004年   3445篇
  2003年   2999篇
  2002年   2706篇
  2001年   1004篇
  2000年   867篇
  1999年   911篇
  1998年   633篇
  1997年   527篇
  1996年   437篇
  1995年   423篇
  1994年   350篇
  1993年   350篇
  1992年   634篇
  1991年   624篇
  1990年   526篇
  1989年   577篇
  1988年   526篇
  1987年   526篇
  1986年   502篇
  1985年   529篇
  1984年   388篇
  1983年   365篇
  1982年   297篇
  1981年   250篇
  1980年   177篇
  1979年   283篇
  1978年   228篇
  1977年   195篇
  1976年   198篇
  1974年   205篇
  1973年   222篇
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
91.
92.
93.
94.
Recent research suggests that, for some people with severe mental illness, supported employment could improve vocational outcomes for little additional expense. This study describes the costs and client outcomes in one mental health center that converted two rehabilitative day treatment programs to supported employment. Converting from day treatment to supported employment improved vocational outcomes significantly without increasing costs. Although total costs for community treatment were lower in both sites after implementing supported employment, differences appeared to be due to decreasing unit costs over the study period. Results illustrate the importance of testing the effects of cost estimation methods on findings.This study was supported by West Central Services, the New Hampshire Division of Mental Health and Developmental Services, and NIMH grant K02-MH-00839. The authors are grateful to Jesse Turner and Phil Wyzik for facilitating the research.  相似文献   
95.
96.
Left ventricular function often deteriorates after mitral valve replacement for mitral regurgitation. It has been postulated that disruption of the mitral valve apparatus at operation is a major mechanism of postoperative dysfunction. The hypothesis tested in this investigation was that chordal preservation results in more favorable left ventricular function. Sixty-nine patients with isolated mitral regurgitation who underwent mitral valve replacement were studied before and 6 months after operation by treadmill exercise testing, catheterization, echocardiography, and radionuclide angiography. Nine patients underwent mitral valve replacement with preservation of the entire mitral apparatus and five with preservation of the posterior leaflet and attached chordae. The remaining 55 had mitral valve replacement with complete excision of the native valve. Preoperatively, there were no differences among groups in age, gender, exercise capacity, cardiac index, rest or exercise ejection fraction, fractional shortening, or pulmonary artery pressures. There were four perioperative deaths (7%) and eight late deaths among the 55 patients with chordal resection but no early or late deaths of patients whose chordae were preserved (p = 0.05). In patients in whom the chordae were excised, exercise capacity, left ventricular systolic dimensions, and cardiac index did not improve after mitral valve replacement, and left ventricular function deteriorated, as evidenced by a reduction of both the resting and exercise ejection fractions (from 46% +/- 13% to 31% +/- 13%, p = 0.0001, and from 49% +/- 12% to 37% +/- 14%, p = 0.0007, respectively) and fractional shortening (from 34% +/- 10% to 26% +/- 14%, p = 0.0001). In contrast, exercise capacity improved after mitral valve replacement in patients in whom the entire apparatus was spared (by 4 +/- 3 minutes, p = 0.05), left ventricular systolic dimensions decreased (from 44 +/- 8 to 36 +/- 9 mm, p = 0.03), and left ventricular function was maintained or improved, as evidenced by preservation of the resting ejection fraction (preoperative, 50% +/- 14%; postoperative, 54% +/- 11%; p = no significant difference), exercise ejection fraction (46% +/- 16% versus 52% +/- 9%, p = no significant difference), fractional shortening (from 31% +/- 9% to 28% +/- 9%, p = no significant difference), and an increase in the cardiac index (from 2.0 +/- 0.3 to 2.7 +/- 0.5 L/min/m2, p = 0.05). No statistically significant differences between posterior chordal resection only and preservation of the entire apparatus were found.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
97.
98.
A series of mono-, di-, and trimethylated derivatives of 4-chloro- and 4-methoxybenzanilide was synthesized and evaluated for anticonvulsant activity. This series was prepared in the course of studies designed to examine the relationship between anticonvulsant effects and benzamide structure. The compounds were tested in mice against seizures induced by maximal electroshock (MES) and pentylenetetrazole (scMet), as well as with the rotorod assay for neurologic deficit. In mice dosed intraperitoneally, 4-methoxy-2, 6-dimethylbenzanilide (4) showed a median anticonvulsant potency (ED50) of 18.58 mg/kg in the MES test and a median toxicity (TD50) of 133.72 mg/kg in the rotorod toxicity assay, yielding a protective index (PI = TD50/ED50) of 7.2. In mice dosed orally with 4, the anti-MES ED50 was 27.40 mg/kg and the TD50 dose was determined to be 342.58 mg/kg, resulting in a protective index of 12.5.  相似文献   
99.
We have demonstrated that certain passive motions of the glenohumeral joint are reproducibly accompanied by translation of the head of the humerus on the glenoid. We investigated the relationship of these translations to the position of the glenohumeral joint and to applied torques and forces in seven isolated glenohumeral joints from fresh cadavera, using a six-degrees-of-freedom position sensor and a six-axis force and torque transducer. Reproducible and significant translation occurred in an anterior direction with glenohumeral flexion and in a posterior direction with extension. We also observed translation with cross-body movement. The translation occurring with flexion was obligate in that it could not be prevented by the application of an oppositely directed force of thirty to forty newtons. Operative tightening of the posterior portion of the capsule increased the anterior translation on flexion and cross-body movement and caused it to occur earlier in the arc of motion compared with the intact glenohumeral joint. Operative tightening of the posterior part of the capsule also resulted in significant superior translation with flexion of the glenohumeral joint.  相似文献   
100.
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