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   1507560篇
  免费   124180篇
  国内免费   9843篇
耳鼻咽喉   19147篇
儿科学   48194篇
妇产科学   42010篇
基础医学   209014篇
口腔科学   39552篇
临床医学   139735篇
内科学   295121篇
皮肤病学   34332篇
神经病学   119979篇
特种医学   57248篇
外国民族医学   500篇
外科学   216856篇
综合类   55200篇
现状与发展   36篇
一般理论   488篇
预防医学   119922篇
眼科学   34199篇
药学   110540篇
  188篇
中国医学   12095篇
肿瘤学   87227篇
  2021年   16237篇
  2020年   11426篇
  2019年   14826篇
  2018年   19768篇
  2017年   16424篇
  2016年   17243篇
  2015年   20929篇
  2014年   28638篇
  2013年   39935篇
  2012年   54537篇
  2011年   57657篇
  2010年   35342篇
  2009年   32929篇
  2008年   50657篇
  2007年   52692篇
  2006年   52776篇
  2005年   50034篇
  2004年   46544篇
  2003年   44275篇
  2002年   42120篇
  2001年   74553篇
  2000年   75702篇
  1999年   62375篇
  1998年   17416篇
  1997年   15841篇
  1996年   15875篇
  1995年   15080篇
  1994年   13611篇
  1993年   12679篇
  1992年   45920篇
  1991年   43549篇
  1990年   41560篇
  1989年   39593篇
  1988年   36233篇
  1987年   35386篇
  1986年   32880篇
  1985年   31287篇
  1984年   23831篇
  1983年   20024篇
  1982年   12211篇
  1979年   20707篇
  1978年   14579篇
  1977年   12089篇
  1976年   11366篇
  1975年   11620篇
  1974年   13991篇
  1973年   13533篇
  1972年   12636篇
  1971年   11469篇
  1970年   10915篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Three children with malignant primary CNS tumors treated with craniospinal radiotherapy developed intraparenchymal hemorrhages a median of 5 years following therapy in sites distant from the primary tumor. Radical surgical procedures disclosed fresh and old hematoma, gliosis, and necrosis in all 3 patients and an aggregation of abnormal microscopic blood vessels in two. No tumor was found. All 3 patients remain in long-term (greater than 10 years) continuous remission.  相似文献   
992.
Recently we have reported that injections of d-amphetamine into the nucleus accumbens enhanced the number of switches to cue-directed behaviours without an effect on the number of switches to non-cue-directed behaviours in a swimming test. In the present study we investigated to what extent this effect is mediated via the dopaminergic system in the nucleus accumbens. For that purpose drugs selective for D1- and D2-receptors were studied in this swimming test. It was found that the selective D2-agonist LY 171 555 (50 ng/0.5 microliters) enhanced the number of different cue-directed behaviours. The selective D2-antagonist raclopride (50 ng/0.5 microliters) decreased it. Furthermore an ineffective dose of raclopride attenuated the effect of LY 171 555. Both the selective D1-antagonist SCH 23390 (400 ng/0.5 microliters) and the selective D1-agonist SKF 38393 (50-400 ng/0.5 microliters) decreased the number of different cue-directed behaviours. The effect induced by SCH 23390 could not be blocked by SKF 38393. Similarly the effect induced by SKF could not be attenuated by SCH 23390. These data point to a role for dopamine D2-receptors in the ability to switch to cue-directed behaviours. The present findings do not yet allow the conclusion that D1-receptors are involved.  相似文献   
993.
Eighty-eight of 143 hospitals in New York State providing psychiatric inpatient treatment responded to a mailed questionnaire designed to determine the size of three subgroups of chemical abusers--alcohol abusers, drug abusers, and polychemical abusers--among inpatients with psychiatric diagnoses, as well as the availability of services for these patients. Data for New York City and its metropolitan area were analyzed separately. In 1987 almost one-third of psychiatric admissions both in and outside the metropolitan area had comorbid chemical abuse disorders. Seventy-five percent of patients in the metropolitan area with comorbid chemical abuse had a drug abuse disorder; in rural areas 88 percent of patients with chemical abuse disorders abused alcohol. Both hospital- and community-based aftercare services, especially in the metropolitan area, were less available to psychiatric patients with chemical abuse than to patients without these disorders.  相似文献   
994.
This paper is a quantitative analysis of the relationship between the chemical structure and the Salmonella mutagenicity of a number of chlorofluorocarbons (CFC). The molecules were characterized by both molecular orbital and physical chemical parameters. The results of the analysis indicated that the CFC mutagenicity is correlated with two parameters: the free energy of binding to biological receptors, and the energy of the highest occupied molecular orbital (HOMO). Since these are the same factors that would favor the cytochrome P-450-catalyzed metabolism, it would appear that the CFC mutagenicity is determined more by the rate of initial activation than by the rate of DNA attack.  相似文献   
995.
Pattern visual evoked potentials were obtained from 46 patients with definite relapsing/remitting multiple sclerosis, using both a conventional 5-channel occipital array and a 3-D recording technique consisting of three bipolar derivations approximating the three dimensions of space. These three orthogonal wave forms were displayed as a 3-D Lissajous trajectory for each subject. Two of the 15 patients with completely normal conventional pattern VEPs had abnormalities of the orientation of the B-C curvilinear segment of the 3-D pattern VEPs. Delays in the first major occipital positive component (P100) were evident using both techniques; the correlation between P100 latency and the latency of the corresponding trajectory apex was r = 0.99 (P less than 0.01). Post-chiasmal MRI abnormalities were associated with 3-D VEP orientation abnormalities. Three-dimensional pattern VEPs are moderately more sensitive than conventional pattern VEPs at detecting dysfunction posterior to the optic chiasm in demyelinating disease and do not require the use of eccentric fixation to do so.  相似文献   
996.
We report the clinical, neurophysiological (comprehending electromyography, nerve conduction velocities, and multimodal evoked potentials), histological study of the nerve and muscle and the effect of vitamin E supplement in a 32-year-old case with chronic vitamin E deficiency subsequent to acquired intestinal malabsorption. An early diagnosis for an early treatment is essential in preventing severe neurological deterioration.  相似文献   
997.
Forgotten few     
C Sadler 《Nursing times》1991,87(30):20-21
  相似文献   
998.
Gonadotrophin-releasing hormone agonists (GnRHAs) were investigated as contraceptive agents from the late 1970's to the mid-1980's. They were abandoned as they appeared to offer no advantage over conventional combination-type oral contraceptives (COCs). This conclusion appears to be incorrect. We propose here a contraceptive regimen of a depot formulation of a GnRHA plus add-back estrogen and intermittent progestogen. The dose of add-back sex-steroids is substantially less than that in COCs; this reduction in sex-steroids should lead to a major reduction in lifetime breast cancer occurrence.  相似文献   
999.
Following an encephalopathic illness, a 13-year-old Chinese boy had a partial form of Klüver-Bucy syndrome with emotional disturbance, recent memory loss, hypersexuality, and polyphagia. Other unusual features included narcolepsy, polydipsia, and polyuria. Virologic studies failed to incriminate the etiologic agent, including herpes simplex virus. Brain biopsy of the frontal lobe demonstrated Alzheimer type II astrocytosis.  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