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   2497217篇
  免费   186533篇
  国内免费   3793篇
耳鼻咽喉   33774篇
儿科学   80011篇
妇产科学   65883篇
基础医学   367883篇
口腔科学   67158篇
临床医学   226131篇
内科学   487657篇
皮肤病学   53756篇
神经病学   200227篇
特种医学   92913篇
外国民族医学   502篇
外科学   377324篇
综合类   50199篇
现状与发展   14篇
一般理论   1087篇
预防医学   197513篇
眼科学   57569篇
药学   185729篇
  10篇
中国医学   4808篇
肿瘤学   137395篇
  2021年   21336篇
  2019年   21811篇
  2018年   29820篇
  2017年   22652篇
  2016年   25134篇
  2015年   28538篇
  2014年   40321篇
  2013年   60390篇
  2012年   83757篇
  2011年   89591篇
  2010年   52923篇
  2009年   49832篇
  2008年   84483篇
  2007年   89884篇
  2006年   90352篇
  2005年   88238篇
  2004年   84445篇
  2003年   81117篇
  2002年   78487篇
  2001年   110179篇
  2000年   112556篇
  1999年   95046篇
  1998年   29029篇
  1997年   25469篇
  1996年   25703篇
  1995年   24170篇
  1994年   22237篇
  1993年   20979篇
  1992年   72933篇
  1991年   70966篇
  1990年   69232篇
  1989年   66381篇
  1988年   61091篇
  1987年   59909篇
  1986年   56019篇
  1985年   53847篇
  1984年   40444篇
  1983年   34547篇
  1982年   21224篇
  1979年   36516篇
  1978年   26388篇
  1977年   21953篇
  1976年   21002篇
  1975年   22376篇
  1974年   26712篇
  1973年   25311篇
  1972年   23547篇
  1971年   22325篇
  1970年   20519篇
  1969年   19525篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
LUMBOVERTEBRAL SYNDROME AFTER EXTRADURAL BLOOD PATCH   总被引:2,自引:1,他引:1  
We describe a patient who developed an immobilizing lumbovertebralsyndrome after an extradural blood patch and who was hospitalizedwith a. suspected extradural abscess. An infectious aetiologyof the persistent backache could be excluded and the patientrecovered with analgesics and physiotherapy. The probable aetiologyis discussed.  相似文献   
992.
993.
Abstract: Establishment of mixed bone marrow chimerism in pig-to-primate transplantation, as a means of inducing specific immune tolerance, will require that both immune and nonimmune barriers be overcome. As a preliminary step in evaluating nonimmune barriers in this system, we have developed an in vitro model of engraftment in which long-term culture of porcine bone marrow-derived hematopoietic cells is supported on preformed primate bone marrow stromal layers. In the absence of cytokine supplementation, primate stromal cells were unable to support long-term porcine hematopoiesis in these cultures. Supplementation with porcine Steel Factor was required for long-term maintenance of hematopoietic progenitor cell content and total hematopoietic activity. Addition of porcine IL-3, in combination with porcine Steel Factor, increased long-term progenitor cell content and hematopoietic activity on primate stroma to levels comparable to that obtained in cultures on porcine stroma. The combination of porcine GM-CSF and Steel Factor increased progenitor cell content and hematopoietic activity early in the cultures, but had little effect in long-term cultures. The Steel Factor and IL-3 combination was species-specific in its action in these cultures, as the corresponding human cytokines were unable to effectively support long-term porcine hematopoiesis. Likewise, the combination of porcine cytokines had only minimal effects on long-term bone marrow culture of primate CD34+ cells I on primate stroma.  相似文献   
994.
To date, only 10 cases of distal penile gangrene in patients with chronic renal failure have been reported. This rare condition is believed to result from progressive vascular calcification due to secondary hyperparathyroidism in patients with chronic renal failure. We report an additional case of distal penile gangrene in a 41-year-old man who presented with chronic renal disease and pulmonary tuberculosis. Since some authors have emphasized that aggressive surgical treatment in such cases has a significant mortality rate, we took a more conservative approach to treatment.  相似文献   
995.
996.
Sensitivity of normotensive Wistar rats and NISAG rats (with hereditary arterial hypertension) to heat stress is compared at the organism and cell levels. High temperature sensitivity of NISAG rats correlates with a low content of the main heat shock protein HSP70. This relationship can serve as a biochemical marker of predisposition to arterial hypertension. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 124, No. 8, pp. 171–173, August, 1997  相似文献   
997.
998.
999.
Most attempts to tissue-engineer cartilage have involved seeding of cultured cells into a biological or synthetic scaffold. We have developed a novel two-step culture approach that makes possible the in vitro formation of cartilaginous-like tissue by mature adult bovine chondrocytes without the aid of a synthetic matrix. The first step consists of culturing chondrocytes under conditions that maintain their rounded shape and their molecular phenotype as assessed by type II collagen and aggrecan production. This step was accomplished by culturing the isolated chondrocytes in alginate beads until the cells have reestablished a proteoglycan-rich cell-associated matrix (CM). The second step consists of culturing the cells with their CM, after recovery from the beads, on a tissue culture insert with a porous membrane. In this study, young adult bovine articular chondrocytes were cultured in alginate beads in the presence of 10% or 20% fetal bovine serum (FBS). After 7 days of culture, the alginate beads were dissolved by incubating the beads for 20 min in sodium citrate buffer, a calcium chelator. Following a brief centrifugation, the cells with their CM were recovered, resuspended in medium containing 10% or 20% FBS and seeded onto a tissue culture insert. After 1 week of culture on the insert, the individual cells with their CM progressively became incorporated into a mass of cartilaginous tissue. Culture with 20% FBS resulted in the best formation of tissues. These tissues, easily recovered from the insert, were then subjected to biochemical and histological analyses. The biochemical results showed that the chondrocytes remain phenotypically stable in the tissues. The de novo tissue has a relatively high ratio of PG/collagen. Histological examination of the tissue revealed it contained a cartilage-like matrix strongly stained with toluidine blue. This scaffold-free system appears ideal to study, in vitro, the development of transplantable cartilaginous tissue.  相似文献   
1000.
A case-control study of squamous cell carcinoma of the upper aerodigestive tract conducted in Heidelberg and Giessen (FRG) provided information on occupational factors in 200 patients and 800 controls (adjusted to sex, age and area of living; 4:1 matched design). The number of subjects exposed to wood dusts, organic chemicals, coal products or to cement was significantly elevated in the tumour group. An increased risk for head and neck cancer was observed after exposition to wood dust (RR = 2,2), organic compounds (RR = 2,4), coal products (RR = 2,7) and especially to cement (RR = 4,4). The cancer risk due to cement exposition showed a positive correlation to the duration of exposition and remained significantly elevated after adjustment for alcohol and tobacco consumption.  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