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   318815篇
  免费   18592篇
  国内免费   1206篇
耳鼻咽喉   3620篇
儿科学   10211篇
妇产科学   7091篇
基础医学   44560篇
口腔科学   12204篇
临床医学   26994篇
内科学   70699篇
皮肤病学   7592篇
神经病学   29186篇
特种医学   9238篇
外国民族医学   30篇
外科学   34935篇
综合类   2163篇
现状与发展   2篇
一般理论   144篇
预防医学   31938篇
眼科学   5529篇
药学   20910篇
中国医学   1166篇
肿瘤学   20401篇
  2023年   2253篇
  2022年   4788篇
  2021年   8540篇
  2020年   5521篇
  2019年   7774篇
  2018年   9697篇
  2017年   7294篇
  2016年   7497篇
  2015年   8511篇
  2014年   11386篇
  2013年   14722篇
  2012年   22540篇
  2011年   23377篇
  2010年   12357篇
  2009年   10993篇
  2008年   18457篇
  2007年   19071篇
  2006年   17509篇
  2005年   17397篇
  2004年   15997篇
  2003年   14578篇
  2002年   12063篇
  2001年   6185篇
  2000年   5979篇
  1999年   5535篇
  1998年   2739篇
  1997年   2281篇
  1996年   2055篇
  1995年   1751篇
  1994年   1715篇
  1993年   1497篇
  1992年   3306篇
  1991年   3090篇
  1990年   2833篇
  1989年   2807篇
  1988年   2546篇
  1987年   2334篇
  1986年   2216篇
  1985年   2088篇
  1984年   1563篇
  1983年   1308篇
  1982年   835篇
  1981年   725篇
  1980年   707篇
  1979年   1103篇
  1978年   750篇
  1977年   607篇
  1975年   652篇
  1974年   645篇
  1973年   638篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
982.
There is little evidence concerning the effects of caffeine in doses typical of one cup of tea. The present study investigated the effect of 60 mg caffeine, consumed in either tea or hot water, on performance on a subset of the CANTAB test battery. Eight males participated in a practice session and four test sessions. In each test session, the participant consumed a different hot beverage and then, over approximately 90 min, completed nine tests from the CANTAB battery. The four beverages were created by crossing beverage identity (tea or hot water) and caffeine dose (0 or 60 mg). Significant speeding of reaction time by caffeine consumption was found in pattern recognition, delayed match to sample, and match to sample visual search. The effect on reaction time of 60 mg caffeine can be detected, and may be evident within minutes of consumption. Received: 16 March 1998/Final version: 27 July 1998  相似文献   
983.
Dermatitis in bulb growers   总被引:2,自引:0,他引:2  
A damaged skin forms a health hazard in flower-bulb growers as it enables higher permeation rates For pesticides than normal skin. Therefore, an investigation was performed into the skin condition of 103 bulb growers and 49 controls. Contact dermatitis of the hands was of the same order (11 and 10%) in both groups. However, minor signs of dermatitis were seen more often in bulb growers (30 versus 8%, p <0.05). Most growers had contact with narcissus sap during the investigation. This irritant sap, as well as many other skin contacts with irritants such as hyacinth dust and pesticides, seemed to be responsible for many skin complaints. Contact serialization was suspected in 19 growers and 3 controls. Patch tests showed that contact sensitization existed to pesticides in probably 10, and to flower-bulb extracts in 4 growers. Reactions to propachlor were not regarded as very reliable as the test concentration seemed to be marginally irritant. There were only a few allergic reactions to narcissus (3) and tulip (2) and none to hyacinth. This investigation showed that minor irritant contact dermatitis was frequent in bulb growers, and indicated that contact sensitization to pesticides and bulbs seemed to be a less frequent but important cause of dermatitis.  相似文献   
984.
Background: The passage of proteins across the glomerular filtration barrier is mainly determined by the size of the protein. In nephrotic syndrome (NS) the glomerular permselectivity is affected, causing proteinuria. Some authors suggest the existence of a generalized basement membrane defect. The permeability characteristics of the peritoneal basement membrane in children with NS are not known. Methods: The transperitoneal transport of proteins with a different molecular weight ({beta}2-microglobulin MW 11 800 D, albumin MW 69 000 D, IgG MW 160 000 D, and &agr;2-macroglobulin MW 820 000 D) was studied in a study group (group A) consisting of six stable nephrotic children (three with glomerulosclerosis and three with congenital nephrotic syndrome, one of them with mesangial sclerosis) and compared to a control group (group B) consisting of eight stable children on peritoneal dialysis. After a dwell of 6 h with Dianeal 1.36% dialysate and serum samples were collected. For each patient the dialysate to plasma (D/P) ratio of the four proteins were calculated. The D/P ratios of the nephrotic patients in group A were compared to the D/P ratios of the patients in the control group B. Data were expressed as mean ±SD. Results: The values for the D/P ratios (in percentage) of {beta}2-microglobulin, albumin, IgG and &agr;2-macroglobulin in group A were 19.6±9.9, 2.7±1.7, 1.6±0.9, and 0.5±0.4, compared to 24.9±10.2, 4.0±2.3, 2.2±1.2, and 0.7±0.3 in the control group B. The ratios were plotted against MW on a double logarithmic scale. In all patients a linear relationship between molecular weight and D/P ratio of the proteins was obtained. The D/P ratios of the study group did no differ significantly from the control group. Conclusion: We conclude that the size selectivity of the capillary permeability is not affected in the peritoneal membrane in children with NS due to glomerulosclerosis and congenital nephrotic syndrome.  相似文献   
985.
ABSTRACT: Nigeria generally has overlooked the health needs of its adolescents. To determine student perceptions of their health-related needs, some 600 students in Uyo, the capital of Akwa Ibom State, were surveyed, and they identified several concerns. Their responses provided the basis to offer five recommendations for action: improve the quality of school health service facilities and personnel available in the secondary schools; implement a comprehensive national program of drug education and control; provide a healthful school environment; assess the quality and quantity of food provided to students, especially in boarding schools; and implement a comprehensive school health education program in Nigerian schools.  相似文献   
986.
987.
Objective To assess the maternal and neonatal effects of upright compared with recumbent positions during delivery, in terms of defined outcome variables.
Design A randomised controlled trial.
Setting St Monica's Nursing Home, a midwife based maternity unit in Cape Town, South Africa.
Participants Five hundred and seventeen women of low obstetrical risk assigned to deliver at the nursing home.
Results The trial showed that women who adopted the upright posture for delivery experienced less pain, perineal trauma and fewer episiotomies than those who delivered in the supine position.
Conclusion The data suggest that in women of low obstetrical risk, choice of posture during delivery may be encouraged.  相似文献   
988.
989.
The presence of functional dopamine receptors on differentiated cells of the mammalian immune system is still under discussion. This study has utilized (-)-[3H]sulpride as a ligand to detect the presence of recognition sites of the dopamine D2 receptor family on human T- and B-lymphocytes. The (-)-[3H]sulpiride binding was of high affinity (Kd 0.9 nM ± 0.2 nM, specific, saturable (Bmax 10.2 ± 1.4 fmol/106 cells) and reversible. The pharmacological characterization of the recognition site suggests, similarities mainly with the D2 and D4 rather than D3 subtype of dopamine receptor. Furthermore, dopamine treatment was able to reduce the intracellular cAMP levels of lymphocytes stimulated with forskolin, thus suggesting a potential functional significance of this dopamine receptor in mediating neural-immune interactions.  相似文献   
990.
Summary We report two cases of Creutzfeld-Jakob disease with clusters of giant collagen fibers. To our knowledge, these abnormally large collagen fibers have never been described in patients with degenerative diseases of the central nervous system. The significance of the formation of such plaque-like large collagen fibers has as yet not been elucidated. It is felt that these represent a product of the degenerative process.Presented in part at the 68th Annual Meeting of the American Association of Neuropathologists, St. Louis, Missouri, June 18–21, 1992  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