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   2488篇
  免费   1篇
电工技术   5篇
化学工业   15篇
机械仪表   1篇
建筑科学   6篇
矿业工程   1篇
能源动力   1篇
轻工业   7篇
水利工程   1篇
石油天然气   2篇
无线电   8篇
一般工业技术   16篇
冶金工业   2415篇
原子能技术   1篇
自动化技术   10篇
  2021年   2篇
  2019年   3篇
  2018年   1篇
  2016年   1篇
  2015年   2篇
  2014年   1篇
  2013年   4篇
  2012年   2篇
  2011年   9篇
  2010年   2篇
  2009年   5篇
  2008年   4篇
  2007年   6篇
  2006年   8篇
  2005年   3篇
  2004年   1篇
  2003年   5篇
  2002年   7篇
  2001年   2篇
  2000年   3篇
  1999年   77篇
  1998年   704篇
  1997年   413篇
  1996年   250篇
  1995年   144篇
  1994年   147篇
  1993年   151篇
  1992年   32篇
  1991年   32篇
  1990年   41篇
  1989年   67篇
  1988年   40篇
  1987年   36篇
  1986年   26篇
  1985年   25篇
  1983年   5篇
  1982年   11篇
  1981年   14篇
  1980年   18篇
  1979年   2篇
  1978年   8篇
  1977年   54篇
  1976年   113篇
  1975年   3篇
  1967年   1篇
  1960年   2篇
  1955年   2篇
排序方式: 共有2489条查询结果,搜索用时 15 毫秒
991.
PURPOSE: Substantia nigra (SN) and locus coeruleus (LC) neurons are implicated in the propagation and suppression of amygdaloid seizures. Both structures are activated concomitant with amygdaloid seizure discharges. Their mechanisms of activation, however, remain to be elucidated. SN firing is not associated with the induction of Fos immunoreactivity (ir), a marker of excitatory neuronal activation. LC has not been studied. The purpose of this investigation was to determine if amygdala-kindled generalized seizures could induce Fos-ir in the LC. METHODS: Female Sprague-Dawley rats were killed after generalized seizures induced by amygdala electrical stimulation and stained by using Fos immunocytochemistry. The number of Fos-ir neurons was compared between 15 animals with generalized seizures and four implanted, unstimulated controls. RESULTS: LC-ir neurons were significantly (p < 0.05) more prevalent after seizures than in control animals. Their numbers correlated very highly with Fos-ir in the central nucleus of the amygdala (p < 0.0001). No Fos induction was observed in LC in controls or in the SN in either group. CONCLUSIONS: Amygdala-induced generalized seizures result in Fos-ir in the LC but not in the SN. This is consistent with different mechanisms of activation possibly involving disinhibition in the SN and direct excitation in the LC.  相似文献   
992.
993.
Achievement at school and performance on the Dominoes test, the Differential Aptitude Tests (DAT), and Griéger's Characterological Questionnaire of 45 monozygotic and 46 same-sex dizygotic pairs of twins were analyzed using a new linear model for familial corrrelation. For 14 of the 20 sets of data, the genotype's contribution to the total variance is estimated to be higher than 50%. The effect of common environment seems to be important only for achievement in Arts.  相似文献   
994.
The advantages of clinical and mechanical combination of observations for prediction are mutually reinforced by an application of Bayesian statistics. The technique is shown to be particularly advantageous in a situation which is characterized by a paucity of observations available to suppliment a prior expert judgment. The approach also presents a basis for evaluating relative expertise and tracing the learning experience of experts. Taking the community as the organizational level of analysis, data on the classification of aged persons in Durham County, North Carolina, and data on the changes in classification of these individuals within the population over time are gathered and studied. These data are combined with clinical judgments of changes as a demonstration of the merits of the technique developed in this paper.  相似文献   
995.
The Drug Exerience Registry is a system for the recording and filing of drug-related patient events in a readily retrievable form. The purpose of the registry is to accumulate information on adverse drug reactions, unusual therapeutic successes of failures, and other experiences that may be useful for education, research or promotion of rational drug therapy. Data are recorded on case report forms which are categorized by organ-disease system affected, the clinical event and involved drug(s). These are then filed in the clinical event file along with literature synopses that serve as guides in evaluating the incidents and determining proper therapy. A drug file serves as a cross index to the clinical event file and allows one to quickly locate clinical events involving a drug. Both files contain sufficient hospital data to allow later retrieval of additional information if needed.  相似文献   
996.
997.
Repetitive behaviors of six autistic children were observed under two conditions of background illumination. During two sessions, the room was illuminated by fluorescent light and during two other sessions, by equal intensity incandescent light. Subjects spent significantly more time engaged in repetitive behavior under fluorescent light. Previous research suggested that these findings were related to the flickering nature of fluorescent ilumination. Practical and theoretical implications were discussed. Further experimentation was suggested to assess relationships between flickering illumination and arousal.  相似文献   
998.
Silicone rubber is the most satisfactory material for cosmetic prostheses. It has a soft, lifelike texture, is easily worked and easily colored and is strong enough to withstand frequent application and removal. Examples of patients referred to the medical sculptor include those with congenital defects of one or both ears, loss of the nose or an eye and orbit due to cancer surgery, loss or absence of fingers or parts of the hand and those who have had radical breast surgery.  相似文献   
999.
1000.
Many previous studies evaluating various hormone levels in males with subnormal semen analyses were performed when the normal semen parameters were considerably higher than now. This study evaluated sera levels of follicle stimulating hormone (FSH), luteinizing hormone (LH), total testosterone (TET), free TET, and prolactin (PRL) in 60 males with oligospermia and decreased motility according to recent World Health Organization standards. Three separate groups were evaluated: group 1, motile density (MD) < 5 x 10(6)/mL (but not azoospermia); group 2, 5 < or = MD < 10 x 10(6)/mL; group 3, MD > 10 x 10(6)/mL, but % motility < 30%. There were no significant differences in mean FSH levels between groups. Overall FSH was increased in 47.1% of the cases. In contrast, mean LH levels were normal in all three groups. Only 17.3% of the entire group had elevated LH levels. The TET level was below normal in 32.3% of the entire group, with a fairly equal distribution between the three groups. Overall, only 7.8% had elevated PRL levels, with the highest percentage found in group 3 (22.2%). Only a small minority of patients with increased FSH had low TET levels compared to 48.0% of those with normal FSH. These data demonstrate that when using the lower semen parameters, the most common serum hormone abnormality is increased FSH; men with MD < 5 x 10(6)/mL do not have a higher incidence of elevated FSH than those with higher MDs.(ABSTRACT TRUNCATED AT 250 WORDS)  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