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   1755382篇
  免费   137399篇
  国内免费   6720篇
耳鼻咽喉   22645篇
儿科学   56898篇
妇产科学   47390篇
基础医学   252386篇
口腔科学   48647篇
临床医学   157281篇
内科学   351658篇
皮肤病学   41730篇
神经病学   139397篇
特种医学   70271篇
外国民族医学   330篇
外科学   271907篇
综合类   38384篇
现状与发展   2篇
一般理论   516篇
预防医学   139325篇
眼科学   38300篇
药学   126991篇
  5篇
中国医学   3089篇
肿瘤学   92349篇
  2018年   17189篇
  2016年   15934篇
  2015年   17762篇
  2014年   24679篇
  2013年   37344篇
  2012年   46412篇
  2011年   50391篇
  2010年   31074篇
  2009年   30069篇
  2008年   47327篇
  2007年   50551篇
  2006年   51774篇
  2005年   49917篇
  2004年   47971篇
  2003年   46564篇
  2002年   44597篇
  2001年   84350篇
  2000年   87025篇
  1999年   72384篇
  1998年   21018篇
  1997年   18680篇
  1996年   19877篇
  1995年   19747篇
  1994年   18333篇
  1993年   17343篇
  1992年   59370篇
  1991年   58714篇
  1990年   56999篇
  1989年   54587篇
  1988年   50444篇
  1987年   49683篇
  1986年   46820篇
  1985年   45138篇
  1984年   34175篇
  1983年   28887篇
  1982年   17517篇
  1981年   15876篇
  1980年   14896篇
  1979年   31322篇
  1978年   22731篇
  1977年   19198篇
  1976年   17880篇
  1975年   19162篇
  1974年   22599篇
  1973年   21490篇
  1972年   20221篇
  1971年   18847篇
  1970年   17285篇
  1969年   16293篇
  1968年   15230篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A method, based on bedside determinations of blood glucose by nursing staff, was designed to control the administration of insulin to diabetic patients during and following open heart surgery. A computer-controlled intravenous infusion pump was used to deliver the insulin. Excellent control of the hyperglycaemia normally associated with open heart surgery was achieved, with 84 percent of measured blood glucose values falling within 2 mmol/litre of the target value of 6 mmol/litre. The method proved to be simple, effective, and safe.  相似文献   
992.
993.
Ileoanal reservoir for ulcerative colitis and familial polyposis   总被引:20,自引:0,他引:20  
Although total proctocolectomy with permanent ileostomy is regarded as the definitive therapy for ulcerative colitis and familial polyposis, psychologic and physical complications with this operation have stimulated the development of the operation of total abdominal colectomy, mucosal proctectomy, ileal reservoir, and ileoanal anastomosis as an alternative surgical procedure. Since 1980, 104 of these operative procedures have been completed with no operative mortality; experience has been gained with both the J- and S-type reservoirs. Despite an appreciable number of postoperative complications, satisfactory function of the reservoir has been achieved in 86 of 91 patients followed up for at least three months after closure of the ileostomy. The remaining five patients have required reinstitution of fecal diversion. Functional results have not differed between two-limbed and three-limbed reservoirs. This operation must be considered a viable alternative in patients with ulcerative colitis and familial polyposis.  相似文献   
994.
In rats fed a diet with 0.25 mg Se/kg the testis selenium content rose during maturation. The value in 4-mo-old animals (7.0 mg Se/kg dry mass; 0.9 mg Se/kg wet mass) was six times higher than that in 20-d-old weanling rats. By comparison, the selenium content in the main selenium pools, muscle and liver, remained unchanged and rose by half, respectively. Due to the increased selenium requirement of the testis during its pubertal maturation the amount of selenium taken up by the male gonads was 50% of the amount deposited in muscle and liver, whereas before and after that period it was about 10%. Feeding animals a low vitamin E diet had no effect on the rise in testis selenium. Glutathione peroxidase activity was twice as high in 4-mo-old animals as in weanling rats. Because only a small percentage of the element in the male gonads was bound to the enzyme, the rise in testis selenium must have been due to other selenium compounds. The selenium content of the spermatozoa was about 21 mg Se/kg dry mass, which by far exceeded the level of this element in other compartments of the rat. The increase in testis selenium content coincided with the beginning of spermatogenesis, and it may therefore ensure the supply of adequate amounts of the element for the spermatozoa.  相似文献   
995.
In order to make effective use of the statistical theory of design of clinical trials for chronic diseases such as periodontal disease, certain issues must be considered. Any clinical trial requires that the disease definition be well-specified; that patient eligibility be explicit; that the observation times be explicit; that the duration and endpoint of therapy be specified; that the duration of subsequent followup observation be specified; and that the unit of observation (e.g., tooth, set of teeth, patient) be defined. In a chronic disease, the potential biases that can readily be introduced by self-selection of patients who enter the trial and/or who return for subsequent observation become more important, because subjects are required to remain on treatment and/or observation for prolonged periods. Further, the cyclical nature of some chronic diseases may require special attention to baseline definitions of active disease and disease outcome. These issues are illustrated with examples from clinical trials of hypertension, breast cancer screening, and Polycythemia Vera. Implications for periodontal disease are discussed.  相似文献   
996.
HPLC analysis of the embryo-toxic fraction of human uterinefluid, collected between the 22nd and 25th days of the menstrualcycle, revealed the presence of cholic acid at high concentrations.It is suggested that cholic acid could be responsible for theembryo-toxicity of the uterine environment, which follows thereceptive period for implantation.  相似文献   
997.
It is still not known how T cells are activated, which T-cell surface structures transmit activation signals, and if antigen-presenting cells possess activation structures for T cells. We have studied whether the T-cell receptor (TcR) must be engaged for T-cell activation to occur. By using membrane-incorporated monoclonal antibodies, we artificially forced T cells to bind to antigen-presenting cells in a mixed lymphocyte reaction system and thereby bypassed the need for TcR engagement and also made it possible for any surface molecule on antigen-presenting cells to deliver a stimulatory signal to the T cells. Theoretically, T cells would become polyclonally activated by this procedure. However, we found that they did not, even though they were intimately bound to the antigen-presenting cell, thus demonstrating that the TcR must participate in antigen/MHC binding in order for the T cells to become activated. This study does not exclude the possibility that antigen-presenting cells possess structures that can activate T cells.  相似文献   
998.
The histological similarities and the common localization are the main causes of difficulties concerning the differential diagnosis between giant cell tumor of bone and chondroblastoma. The purpose of the present study was to detect whether histochemistry and/or immunohistochemistry could help to make the distinction between these two entities easier. The study was based on cases of chondroblastoma and giant cell tumor of bone from patients in the 2nd and 3rd decades of life. Histochemical detection of special intracellular and extracellular components (glycogen, glycosaminoglycans) as well as immunohistochemical investigation using various tumor markers (S-100, NSE, a-1-ACT, lysozyme, fibronectin) were performed on parallel paraffin sections. The presence of abundant intracytoplasmic glycogen granules and the immunoreactivity of the cells of chondroblastoma with S-100 and NSE, together with the presence of acidic sulfated glycosaminoglycans in the stroma, could help the differential diagnosis of this tumor from giant cell tumor of bone.  相似文献   
999.
The cytoskeleton is susceptible to oxidative stress and this occurs prior to membrane blebbing and cell lysis. Vimentin intermediary filaments in rheumatoid synoviocytes are more susceptible than in normal synoviocytes and this may have pathological significance. They are however no more susceptible to heat shock than other cell types.  相似文献   
1000.
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