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   23428篇
  免费   2255篇
  国内免费   74篇
耳鼻咽喉   390篇
儿科学   715篇
妇产科学   638篇
基础医学   3121篇
口腔科学   716篇
临床医学   3129篇
内科学   4448篇
皮肤病学   437篇
神经病学   1822篇
特种医学   946篇
外国民族医学   2篇
外科学   3270篇
综合类   381篇
一般理论   13篇
预防医学   2210篇
眼科学   423篇
药学   1601篇
  4篇
中国医学   68篇
肿瘤学   1423篇
  2021年   264篇
  2020年   205篇
  2019年   293篇
  2018年   379篇
  2017年   285篇
  2016年   322篇
  2015年   382篇
  2014年   552篇
  2013年   781篇
  2012年   1062篇
  2011年   1173篇
  2010年   672篇
  2009年   594篇
  2008年   965篇
  2007年   1016篇
  2006年   1027篇
  2005年   946篇
  2004年   1038篇
  2003年   979篇
  2002年   840篇
  2001年   787篇
  2000年   712篇
  1999年   695篇
  1998年   348篇
  1997年   301篇
  1996年   262篇
  1995年   258篇
  1994年   222篇
  1993年   232篇
  1992年   538篇
  1991年   525篇
  1990年   459篇
  1989年   532篇
  1988年   498篇
  1987年   492篇
  1986年   460篇
  1985年   487篇
  1984年   326篇
  1983年   294篇
  1982年   205篇
  1981年   182篇
  1979年   258篇
  1978年   201篇
  1977年   173篇
  1976年   183篇
  1975年   156篇
  1974年   190篇
  1973年   203篇
  1972年   159篇
  1971年   162篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
The intrauterine position occupied by a rodent fetus influences the amount of testosterone to which it is exposed before birth. Animals that are gestated between two male fetuses (2M) are exposed to higher circulating levels of testosterone than are animals positioned between two female fetuses (2F) and there are reliable differences in the reproductive physiology and behavior of 2M and 2F animals when adult. To determine whether intrauterine position modifies development of the central nervous system, we examined the sexually dimorphic spinal nucleus of the bulbocavernosus (SNB) in male and female gerbils from known intrauterine positions. We found that adult 2M female gerbils had 16% more SNB motoneurons than did 2F females. 2M males did not differ from 2F males in SNB motoneuron number, but the bulbocavernosus muscle, which is innervated by SNB motoneurons, was approximately 50% larger in 2M than in 2F males. These data indicate that intrauterine position can influence the morphology of the sexually dimorphic SNB neuromuscular system.  相似文献   
32.
33.
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   
34.
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   
35.
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   
36.
37.
The time taken in hospital pharmacies to produce labels for individual patients' medication was measured, and factors affecting the labelling process investigated. Labelling time was measured by direct observation using a stopclock at randomly chosen semi-stratified time periods. Four combinations of major London hospitals and computer systems were studied. The time to produce 2,167 labels was measured and 59 operators were observed. There were significant differences in average labelling time between the studied hospitals/systems (16.6 to 39.3 seconds per label). Operators' experience with their system and the occurrence of interruptions were found to affect labelling significantly (P<0.0001 in both cases). There was an overall trend for labelling time to decrease with increasing experience (P<0.0001), and interruptions added 11 to 12 seconds on average. Operator experience also affected the rate and duration of interruptions, which subsequently affected labelling time. Fewer interruptions occurred with more experienced staff (P=0.0015) and when interrupted, they took less time than inexperienced staff to complete the labelling process. A performance indicator of person-days per 100,000 labels varied from 62.3 to 147.6. Pharmacy managers should be aware that there are significant differences in performance using different labelling systems and that staff training and systems of work may have a marked effect on labelling time.  相似文献   
38.
A newly developed microwell enzyme immunosorbent assay (EIA) system by Syva Company (Palo Alto, CA) can detect Chlamydia trachomatis in < 3 hr. It uses a polyclonal antibody to chlamydial lipopolysaccharide and end points are determined with a spectrophotometer. Three clinical trial sites (University of California Medical Center, San Francisco, CA; University of Washington, Seattle, WA; and Louisiana State University Medical Center, New Orleans, LA), compared this EIA with tissue culture (TC) for identifying Chlamydia in urogenital specimens. Overall prevalence by TC was 10.4% (136 of 1306). When tests were compared with TC (using vials or microtiter plates and a fluorescent antibody stain), we found an EIA sensitivity of 93.4% (127 of 136) and a specificity of 98.1% (1148 of 1170). This EIA has a performance profile that is, at the very least, comparable with other nonculture methods for diagnosing genital tract infections with C. trachomatis.  相似文献   
39.
Five studies were conducted to measure changes in the perception and production of selected speech targets, with training, in three prelingually deaf patients. The two adults and one adolescent were implanted with the Cochlear (Nucleus) multiple-electrode prosthesis. The studies were perception and production of nasal consonants; perception of syllable-final consonants; perception and production of alveolar consonants; auditory-visual perception of alveolar consonants; and perception and production of vowels. Perceptual data were collected in the audition (implant)-alone condition, except for the auditory-visual perception of alveolar consonants where the audition-alone, vision-alone, and auditory-visual conditions were used. Speech perception data in the audition-alone condition were also collected from four postlingually deaf adult implant patients, without training, to indicate differences between the two classes of patients. The three prelingually deaf patients generally showed some improvements in speech production. In perception, improvements were recorded only for individual patients in some studies. The performance of the adolescent was better than that of the two adults in all cases. The perceptual performance of the postlingually deaf patients was superior to that of the prelingually deaf patients in all cases.  相似文献   
40.
d,l-Norephedrine (phenylpropanolamine) which is both a demethylated analogue and a metabolite of d,l-ephedrine, is a reputed anorectic agent. In the present study the proposed most active isomer of this mixture, l-norephedrine has been assessed as a peripherally acting thermogenic agent in the isolated perfused rat hindlimb. l-Norephedrine produced a dose-dependent increase in oxygen uptake and perfusion pressure and increased lactate production. Whereas propranolol potentiated the increase in oxygen uptake and perfusion pressure produced by l-norephedrine, prazosin significantly and nitroprusside totally inhibited both of these changes. Nitroprusside also completely inhibited the increase in lactate production. We conclude that norephedrine has a hitherto unrecognized peripheral thermogenic activity in the perfused rat hindlimb resulting from its interaction with alpha 1 adrenergic receptors that control vasoconstriction in this tissue.  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