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   1264667篇
  免费   96733篇
  国内免费   1573篇
耳鼻咽喉   16320篇
儿科学   41118篇
妇产科学   34996篇
基础医学   189698篇
口腔科学   34809篇
临床医学   117949篇
内科学   248392篇
皮肤病学   27331篇
神经病学   102177篇
特种医学   47078篇
外国民族医学   266篇
外科学   178899篇
综合类   25797篇
现状与发展   3篇
一般理论   569篇
预防医学   104760篇
眼科学   28051篇
药学   92637篇
  6篇
中国医学   2019篇
肿瘤学   70098篇
  2018年   13565篇
  2017年   10426篇
  2016年   11356篇
  2015年   13115篇
  2014年   18060篇
  2013年   27551篇
  2012年   37707篇
  2011年   40091篇
  2010年   23148篇
  2009年   22314篇
  2008年   37887篇
  2007年   40552篇
  2006年   40090篇
  2005年   39225篇
  2004年   37684篇
  2003年   36085篇
  2002年   34982篇
  2001年   56123篇
  2000年   57162篇
  1999年   48186篇
  1998年   13428篇
  1997年   12260篇
  1996年   12665篇
  1995年   11946篇
  1994年   11137篇
  1993年   10433篇
  1992年   38276篇
  1991年   37757篇
  1990年   36517篇
  1989年   35336篇
  1988年   32763篇
  1987年   32111篇
  1986年   30590篇
  1985年   28853篇
  1984年   21994篇
  1983年   19243篇
  1982年   11400篇
  1981年   10354篇
  1979年   20999篇
  1978年   15446篇
  1977年   12829篇
  1976年   11872篇
  1975年   12840篇
  1974年   15637篇
  1973年   15398篇
  1972年   14537篇
  1971年   13590篇
  1970年   12826篇
  1969年   12099篇
  1968年   11260篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
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   
992.
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   
993.
994.
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   
995.
996.
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   
997.
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   
998.
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   
999.
1000.
Since the aminoglycoside antibiotic apramycin was licensed for veterinary use in 1980, all isolates of Escherichia coli and salmonellas received at the Central Veterinary Laboratory have been monitored for resistance to apramycin and the related antibiotic gentamicin. During the period 1982-4, the incidence of resistance in E. coli to apramycin increased from 0.6% in 1982 to 2.6% in 1984. In salmonellas the incidence of resistance to apramycin increased from 0.1% in 1982 to 1.4% in 1984. Resistance to both apramycin and gentamicin was detected in six different salmonella serotypes, although an isolate of Salmonella thompson from poultry was resistant to gentamicin but not apramycin. Most of the cultures were isolated from pigs, although the incidence of apramycin resistance in S. typhimurium (DT 204C) from calves has shown a recent dramatic increase. All the isolates with one exception produced the enzyme aminoglycoside 3-N-acetyltransferase IV (ACC(3)IV). The resistance was transferable by conjugation in most of the strains examined, and the plasmids specifying the resistance have been found to belong to a number of different incompatibility groups. Plasmids from three E. coli strains were compatible with all the reference plasmids and belonged to a previously undescribed group which was investigated further. It is suggested that bacteria from humans should be examined for resistance to apramycin and gentamicin to determine the possibility of the antibiotic-resistance bacteria, and their genes, spreading from animals to humans.  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