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   2364576篇
  免费   172764篇
  国内免费   3394篇
耳鼻咽喉   32175篇
儿科学   76395篇
妇产科学   63136篇
基础医学   350372篇
口腔科学   63885篇
临床医学   213132篇
内科学   460148篇
皮肤病学   52193篇
神经病学   186768篇
特种医学   88413篇
外国民族医学   489篇
外科学   355254篇
综合类   47628篇
现状与发展   12篇
一般理论   865篇
预防医学   184414篇
眼科学   54546篇
药学   176032篇
  11篇
中国医学   4603篇
肿瘤学   130263篇
  2021年   19692篇
  2019年   20126篇
  2018年   27712篇
  2017年   20855篇
  2016年   23297篇
  2015年   26214篇
  2014年   36788篇
  2013年   54860篇
  2012年   75958篇
  2011年   80696篇
  2010年   47710篇
  2009年   45135篇
  2008年   75492篇
  2007年   80348篇
  2006年   81039篇
  2005年   78487篇
  2004年   75033篇
  2003年   72280篇
  2002年   69863篇
  2001年   108821篇
  2000年   111515篇
  1999年   93570篇
  1998年   27085篇
  1997年   23724篇
  1996年   24107篇
  1995年   22765篇
  1994年   20940篇
  1993年   19752篇
  1992年   72025篇
  1991年   70102篇
  1990年   68428篇
  1989年   65681篇
  1988年   60316篇
  1987年   59146篇
  1986年   55230篇
  1985年   53025篇
  1984年   39332篇
  1983年   33409篇
  1982年   19869篇
  1979年   35871篇
  1978年   25669篇
  1977年   21239篇
  1976年   20340篇
  1975年   21818篇
  1974年   26155篇
  1973年   24810篇
  1972年   23203篇
  1971年   22044篇
  1970年   20248篇
  1969年   19317篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
M.A. Sabbahi  E.M. Sedgwick   《Brain research》1987,423(1-2):125-134
The H-reflex of 120 soleus motoneurons was recorded using fibre EMG. The recovery profile of these motoneurons was studied during monitoring surface H-reflex records in 28 adult subjects. The spectrum of motoneurons tested was homogeneous with two extremes of neurons having different characteristics. A motoneuron population (forming about 69% of our sample) had a high threshold level for electrical stimuli, short recovery time, and short recovery fringe time (called type A). A second population of motoneurons (forming about 20-30% of our sample) had a low threshold level for electrical stimuli, long recovery fringe time (called type B). During an isometric muscle contraction every motoneuron showed an early shift in recovery time (i.e. each had a shorter recovery time) with shortened recovery fringe time. These changes were larger for motoneurons type B than motoneurons type A. With paired identical electrical stimuli of varying interstimulus intervals a motoneuron may fire in response to the conditioning and test stimuli giving an H2, but not in response to both stimuli. This occurred for interstimulus intervals of 4-11 ms. A strong inhibition period was recorded with interstimulus intervals of 12-80 ms in which all motoneurons did not show any recovery. Most motoneurons recovered in orderly fashion between 80 and 300 ms of interstimulus interval, and this recovery coincided with the fast recovery recorded in surface H-reflex. All motoneurons were recovered by 3000 ms of interstimulus intervals. These findings emphasize the importance of eliciting the H-reflex every 3-5 s in H-reflex methodology in order to be assured that all excited motoneurons have been recovered.  相似文献   
992.
993.
Two hundred and thirty pregnancies were studied in 196 diabetic women. Seven women with babies found to have major malformations had a higher median first trimester haemoglobin A1 (12.9%) than the median HbA1 (10.8%) in those with normal babies (p = 0.06). No relationship was found between the occurrence of minor malformations and first trimester maternal haemoglobin A1. Two of the seven congenital malformations were diagnosed antenatally at a time when therapeutic abortion could be offered. Expert antenatal ultrasound scanning should be offered to all pregnant diabetic women as poor glycaemic control at the time of conception and organogenesis, as evidenced by raised first trimester HbA1, predisposes to congenital malformation.  相似文献   
994.
This paper gives the historical sketch necessary for an understanding of the current state of American psychiatry. It reviews some of the reasons why the rendering of good hospital care must be reconsidered, and describes some of the main features of the future public institution.  相似文献   
995.
During almost 12 years of development and clinical trials, diclofenac sodium has been shown to be both effective and safe as a new nonsteroidal antiinflammatory drug (NSAID) for the treatment of rheumatic diseases including ankylosing spondylitis (AS). We compared the safety and efficacy of 75, 100, or 125 mg/day of diclofenac with the same doses of indomethacin in a multicenter, randomized, parallel group trial in patients with AS. A single blind placebo washout period of 2 days to 2 weeks preceded the 13-week double blind treatment period. Both diclofenac and indomethacin produced significant (p less than 0.001) improvement from baseline for all 14 efficacy variables analyzed. There were no significant between treatment differences. Differences favored diclofenac in the frequency and the severity of adverse experiences reported and in the frequency of complaints affecting the central nervous system.  相似文献   
996.
Various cases are presented demonstrating the role of computed tomography (CT) in the assessment of serosal and bowel wall pathology. Reference is made to the morphology of the lesions. Illustrative examples of tumors, secondary malignant dissemination, irradiation injury to the gut, and intramural gas associated with ulcerative colitis, are all illustrated.  相似文献   
997.
998.
999.
1000.
The spontaneous quantal and nonquantal acetylcholine release was investigated at the temperature range from 10 to 35 degrees C in white mouse semidiaphragm. The quantal release was evaluated by calculation of miniature end-plate potentials frequency, while the nonquantal one--from the H-effect value. The spontaneous quantal release increased exponentially with the temperature growth. The temperature dependence of the nonquantal release showed two relative maxima: at 20 degrees and 35 degrees C. At 10 degrees C the nonquantal release was absent. The value of calculated effective energy of activation of the quantal release was 57.0 kJ/mol in the investigated temperature range. The effective energy of activation for the nonquantal release process in intervals 15-20 degrees C and 25-35 degrees C was 45.5 and 38.2 kJ/mol, relatively. It is suggested that the nonquantal release is rather due to active transport processes than to simple diffusion of acetylcholine molecules.  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