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   530225篇
  免费   27663篇
  国内免费   496篇
耳鼻咽喉   6681篇
儿科学   16925篇
妇产科学   12537篇
基础医学   92658篇
口腔科学   12349篇
临床医学   48516篇
内科学   95499篇
皮肤病学   11874篇
神经病学   34025篇
特种医学   19765篇
外国民族医学   53篇
外科学   78080篇
综合类   7611篇
现状与发展   2篇
一般理论   107篇
预防医学   38553篇
眼科学   11939篇
药学   41420篇
  1篇
中国医学   1129篇
肿瘤学   28660篇
  2021年   3907篇
  2018年   5739篇
  2017年   4130篇
  2016年   4877篇
  2015年   5372篇
  2014年   7123篇
  2013年   10507篇
  2012年   15591篇
  2011年   17399篇
  2010年   9970篇
  2009年   8826篇
  2008年   15723篇
  2007年   17455篇
  2006年   16946篇
  2005年   16274篇
  2004年   15889篇
  2003年   15270篇
  2002年   14795篇
  2001年   22432篇
  2000年   22970篇
  1999年   18921篇
  1998年   5235篇
  1997年   4367篇
  1996年   4399篇
  1995年   4128篇
  1992年   14413篇
  1991年   15817篇
  1990年   15950篇
  1989年   15625篇
  1988年   14308篇
  1987年   14198篇
  1986年   13168篇
  1985年   12688篇
  1984年   9395篇
  1983年   8001篇
  1982年   4179篇
  1979年   8937篇
  1978年   6382篇
  1977年   5150篇
  1976年   5505篇
  1975年   6614篇
  1974年   7419篇
  1973年   7159篇
  1972年   6597篇
  1971年   6309篇
  1970年   5887篇
  1969年   5467篇
  1968年   5161篇
  1967年   4621篇
  1966年   3963篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
991.
The authors present the results of a transmission electron-microscopic study performed on a tissue sample obtained by an intraocular fine-needle aspiration biopsy in a case of retinoma. The ultrastructural study showed that the tumor was composed mainly of granular osmiophilic material which contained some tumor cells. These cells showed peculiar ultrastructural characteristics, which demonstrated their neural character, and appeared in different degenerative stages. Apparently, this is the first case in whom ultrastructural technique have been applied to study an intraocular tumor sample obtained by intraocular fine-needle aspiration biopsy, and the first case of retinoma studied by such a diagnostic approach.  相似文献   
992.
An eye protection program is needed in occupational medicine policies. Typical eye injuries and eye accidents, as they relate to occupational accidents, justify the management advocating such a program. A recommended model for a functional eye protection program is provided and defined.  相似文献   
993.
Central sensory and motor conduction in vitamin B12 deficiency.   总被引:7,自引:0,他引:7  
Four patients with subacute combined degeneration were studied through upper and lower limb SEPs recorded with a non-cephalic reference montage and through cortical and spinal magnetic stimulation. Clinical signs were confined to the lower limbs in 3 patients; the remaining patient presented only paraesthesiae in 4 limbs. Median nerve SEPs showed a normal cervical N13 response with a significant increase of central conduction time concerning exclusively the P9-P14 interpeak interval. Central motor conduction to upper and lower limb muscles was abnormal. Nerve conduction studies provided no evidence of peripheral nerve involvement. These electrophysiological findings suggest that in vitamin B12 deficiency the higher segments of the cervical cord are usually affected first and that central sensory and motor conduction studies are sensitive methods for detecting such damage.  相似文献   
994.
Disease processes in the peritoneum, omentum, and mesentery occasionally are not recognized at radiologic examination. The authors have used computed tomography (CT) to categorize the radiologic appearances of the more common abnormalities into three basic patterns: (a) solid but relatively well-defined masses, (b) cystic-appearing masses, and (c) ill-defined or infiltrative processes. The most common solid masses to affect these anatomic regions are secondary neoplasms, which are associated with enhancement of the peritoneum on contrast material-enhanced CT scans and, typically, ascites. The various cystic-appearing masses (including cystic lymphangioma, cystic mesothelioma, teratoma, and loculated ascites) and infiltrating masses (such as peritoneal mesothelioma, retractile mesenteritis, desmoid, and carcinoid) must be differentiated on the basis of clinical findings and additional imaging findings (eg, CT depiction of fat and calcium in teratomas and the radiating appearance of carcinoids). Although the CT appearances of some of the abnormalities overlap, classifying them by pattern is helpful in narrowing the range of the differential diagnosis.  相似文献   
995.
We describe the types of aggressive behaviour and determine their prevalence in a sample of hospitalized elderly psychiatric patients. Data were obtained by nurse ratings of aggressive behaviour using the recently developed Rating Scale for Aggressive Behaviour in the Elderly; 90 patients were rated over a 3-d period. Nearly half the sample were at least mildly aggressive; the frequencies of some specific types of aggressive behaviour were high. In contrast, the frequency of injuries and the use of restraints and medication for aggressive behaviour were low. Some correlates of the aggressive behaviour were also analysed.  相似文献   
996.
997.
998.
999.
1000.
The effects of various neurotransmitters on phosphoinositide hydrolysis, mobilization of Ca2+ and release of [3H]-norepinephrine ([3H]-NE) were studied in cultures of sympathetic neurons of chick embryos. [3H]-inositol-1,4,5-triphosphate ([3H]-IP3) was increased in sympathetic neurons by acetylcholine (ACh), muscarine and serotonin (5-HT). Dopamine and norepinephrine did not stimulate phosphoinositide hydrolysis. Intracellular concentration of free Ca2+ ([Ca2+]i) was measured in Indo-1-loaded sympathetic neurons at rest and after addition of test agents. Measurements were made in the cell body and growth cone regions since Ca2+ mobilization is known to be different in different regions of the sympathetic neurons. ACh (nicotinic component was blocked by hexamethonium) and 5-HT failed to increase the [Ca2+]i, in the cell body as well as in the growth cone. The spontaneous release of [3H]-NE was not affected by ACh and 5-HT. Caffeine increased the [Ca2+]i only in the cell body but not in the growth cone and had no effect on the release of [3H]-NE. These results suggest that an IP3-insensitive but caffeine-sensitive pool of Ca2+ is present only in the somatic region of sympathetic neurons and is not coupled to the transmitter release.  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