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   1263990篇
  免费   96636篇
  国内免费   1603篇
耳鼻咽喉   16378篇
儿科学   41005篇
妇产科学   34962篇
基础医学   189705篇
口腔科学   34788篇
临床医学   117824篇
内科学   248368篇
皮肤病学   27344篇
神经病学   102000篇
特种医学   46829篇
外国民族医学   265篇
外科学   178877篇
综合类   25767篇
现状与发展   3篇
一般理论   568篇
预防医学   104580篇
眼科学   28075篇
药学   92643篇
  6篇
中国医学   2020篇
肿瘤学   70222篇
  2018年   13588篇
  2017年   10427篇
  2016年   11388篇
  2015年   13142篇
  2014年   18070篇
  2013年   27570篇
  2012年   37685篇
  2011年   40131篇
  2010年   23117篇
  2009年   22307篇
  2008年   37872篇
  2007年   40511篇
  2006年   40086篇
  2005年   39230篇
  2004年   37677篇
  2003年   36107篇
  2002年   34981篇
  2001年   56146篇
  2000年   57168篇
  1999年   48194篇
  1998年   13423篇
  1997年   12248篇
  1996年   12666篇
  1995年   11930篇
  1994年   11118篇
  1993年   10411篇
  1992年   38249篇
  1991年   37718篇
  1990年   36504篇
  1989年   35308篇
  1988年   32736篇
  1987年   32071篇
  1986年   30557篇
  1985年   28828篇
  1984年   21964篇
  1983年   19211篇
  1982年   11370篇
  1981年   10327篇
  1979年   20960篇
  1978年   15401篇
  1977年   12798篇
  1976年   11854篇
  1975年   12819篇
  1974年   15596篇
  1973年   15371篇
  1972年   14526篇
  1971年   13562篇
  1970年   12798篇
  1969年   12070篇
  1968年   11243篇
排序方式: 共有10000条查询结果,搜索用时 718 毫秒
991.
992.
A human factors engineering analysis of a chemical containment laboratory was performed to develop appropriate standards for future laboratory design. In order to perform this evaluation, a state-of-the-art facility was studied in depth. Measurements and observations were made of key operating areas. In addition, technicians were observed and interviewed as they performed various tasks. Compiled data were compared to existing ergonomic standards. The occupational implications of instituting ergonomically developed laboratory design standards are as follows: increased worker health, safety and productivity, improved work quality and reduced stress.  相似文献   
993.
The ganglioside composition of human melanoma was analyzed in five sets of tumor specimens obtained directly from surgery, from the autologous tissue culture cell lines, and from the autologous cell lines grown in athymic nude mice. Total gangliosides of these 15 melanoma specimens were isolated and purified, and the amount of each component ganglioside was analyzed by thin-layer chromatography and a thin-layer chromatography scanner. The ganglioside composition of the five surgical melanoma specimens clearly exhibited different patterns from each other. Moreover, none of the autologous cultured melanomas possessed the same ganglioside composition as their original biopsied tumors. However, when these melanoma cell lines were transplanted into nude mice, the ganglioside composition was converted back to the same ganglioside pattern as in the original surgical specimens. The results support the view that changes in the ganglioside composition of melanoma during in vitro growth are caused by the culture environment rather than by selection of melanoma cells with a particular genotype. Reestablishment of the original ganglioside patterns after passage in nude mice provides clear evidence that in vivo expression of gangliosides is a conserved and stable function specified by the human melanoma cells.  相似文献   
994.
995.
Summary The authors report 165 cases of thoraco-lumbar lesions with neurological dysfunction. All the patient were operated. They analyze the neurological and mechanical results and indicate the use of different osteosynthesis apparatus according to the type and level of lesions.Harrington's rods seem to give more precise repositioning while Roy Camille's plates give more stability. When the posterior wall of the spinal canal is intact, Kempf's compression rods can be used.Thoraxic spine injuries seem to be an indication for Harrington's rods, while lumbar injuries seem to call for Camille's plates.  相似文献   
996.
997.
This study focuses on obtaining more information about the site of anastomosis, with three-dimensional examination using methylmethacrylate resin (Mercox) corrosion casts. Seventy microvascular anastomoses were performed in Wistar albino rats, divided into two groups before sacrifice. In Group 1 (35), Mercox was injected into the vessels, whereas in Group 2 (35), the tissues were prepared without injecting Mercox. Both groups were compared under the scanning electron microscope (SEM). The SEM preparation in Group 1 was simple, easy, and artifacts were significantly minimized. The anastomotic site could be well appreciated in three-dimensional views. Clear negative imprints of the endothelial surface were achieved without any breakage in the Mercox corrosion cast, and it can be reliably used in the evaluation of small vessel anastomosis.  相似文献   
998.
S E Bedell  D Pelle  P L Maher  P D Cleary 《JAMA》1986,256(2):233-237
We studied compliance with do-not-resuscitate (DNR) orders at a university hospital where a DNR protocol has existed since 1979. Documentation of DNR status in patient progress notes and chart orders increased through 1983. During a 12-month period (March 1983 through April 1984), we studied in detail the medical records of 521 patients who had a cardiopulmonary arrest in the hospital. Seventy-five percent (389 of 521) of these patients were designated DNR. Patients who were designated DNR were significantly more likely to be older, to have malignancy or an abnormal mental status, and to be less likely to have acute myocardial infarction, stroke, or chronic obstructive pulmonary disease than patients in whom resuscitation was attempted. Eighty-six percent of families, but only 22% of patients, were involved in the decision to designate a patient DNR. The decision to designate a patient DNR occurred late in the course of a patient's illness, often when the patient was in coma. For 28% of patients, some form of medical care was withdrawn or withheld after they were designated DNR. These data suggest that use of the DNR protocol requires changes if patients are to participate in the decision not to undergo cardiopulmonary resuscitation.  相似文献   
999.
The history and epidemiology of bovine tuberculosis in cattle herds in East Sussex are described. Since 1960, following the compulsory eradication scheme for tuberculosis, the incidence of herd infection has been low. The epidemiological features of herd infection have been sporadic incidents, with only small numbers of cattle becoming infected in the majority of incidents. There was no evidence of endemic Mycobacterium bovis infection in the cattle population in East Sussex in recent years, but a low risk of infection for cattle on the South Downs, from badgers, was apparent.  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