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   82827篇
  免费   1058篇
  国内免费   698篇
电工技术   1511篇
综合类   60篇
化学工业   12820篇
金属工艺   3574篇
机械仪表   2744篇
建筑科学   2115篇
矿业工程   550篇
能源动力   2051篇
轻工业   7181篇
水利工程   948篇
石油天然气   2341篇
武器工业   41篇
无线电   7693篇
一般工业技术   17612篇
冶金工业   14500篇
原子能技术   2723篇
自动化技术   6119篇
  2022年   594篇
  2021年   1013篇
  2020年   789篇
  2019年   872篇
  2018年   1654篇
  2017年   1665篇
  2016年   1882篇
  2015年   1051篇
  2014年   1713篇
  2013年   3984篇
  2012年   2625篇
  2011年   3166篇
  2010年   2639篇
  2009年   2939篇
  2008年   2980篇
  2007年   2898篇
  2006年   2486篇
  2005年   2166篇
  2004年   2065篇
  2003年   2018篇
  2002年   1911篇
  2001年   1827篇
  2000年   1813篇
  1999年   1709篇
  1998年   3786篇
  1997年   2715篇
  1996年   2052篇
  1995年   1660篇
  1994年   1459篇
  1993年   1475篇
  1992年   1129篇
  1991年   1140篇
  1990年   1180篇
  1989年   1172篇
  1988年   1056篇
  1987年   989篇
  1986年   998篇
  1985年   1081篇
  1984年   912篇
  1983年   881篇
  1982年   806篇
  1981年   818篇
  1980年   751篇
  1979年   771篇
  1978年   740篇
  1977年   876篇
  1976年   1018篇
  1975年   667篇
  1974年   640篇
  1973年   641篇
排序方式: 共有10000条查询结果,搜索用时 601 毫秒
991.
Examined publishing practices of the American Psychological Association (APA) in the alcohol and drug area. Although the total number of articles published by APA increased only 7.6% between 1984 and 1990, the number of alcohol and drug articles more than doubled. Despite the disproportionate growth of alcohol and drug articles between 1984 and 1990, only 3.8% of 1,408 APA articles published in 1990 addressed alcohol and drug use issues. An earlier investigation by M. O. Howard and D. A. Howard (1992) reported that 541 articles published in 1984 in 12 alcohol and drug specialty journals received an average of 3.48 citations by the end of 1988. Alcohol and drug articles published by APA in 1984 received more than 4 times as many citations during this period. Also, alcohol and drug articles published by APA received significantly more citations between 1984 and 1988 than those published in specialty journals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
992.
This study focused on the self-representations of suicidal adolescent. Twenty-six Israeli suicidal inpatients, 24 nonsuicidal inpatients, and 24 control participants completed scales on suicidal tendencies, the hedonic value of self-representations, the complexity (differentiation, integration) of these self-representations, and the discrepancies among self domains (actual, ideal, ought). Suicidal adolescents showed more negative self-representations, a less differentiated and less integrated organization of self-attributes, and more discrepancies between the 3 assessed domains of the self than did control participants. In addition, compared with psychiatric nonsuicidal participants, suicidal adolescents showed a less complex organization of self-attributes and a higher discrepancy between ideal self and ought self. Results were discussed in terms of the vulnerable self of suicidal adolescents, characterized by uneven processing of positive and negative information, confusion, and simplicity.  相似文献   
993.
The solutions of the direct and inverse problems of electromagnetic diagnostics of laminated materials with the use of a rectangular waveguide as a radiator are presented. The direct problem, i.e., the problem of finding the coefficient of reflection of electromagnetic waves, is solved by using a method based on the computation of the energy flow through the aperture of a waveguide. The method of global minimization was applied to solve the inverse problem, i.e., to find the parameters of the material for given reflection coefficients measured at various frequencies.Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 30, No. 2, pp. 26–33, March–April, 1994.  相似文献   
994.
NADPH diaphorase histochemistry is commonly used to identify cells containing nitric oxide synthase (NOS), the enzyme catalyzing the production of nitric oxide from L-arginine. NADPH diaphorase activity and NOS immunostaining was demonstrated in different cells of the vertebrate retina; photoreceptors, horizontal cells, amacrine cells, ganglion cells, and Müller cells. However, the physiological role of nitric oxide (NO) in the retina has yet to be elucidated. In this study, we tested the assumption that NADPH diaphorase activity in the retinas of rabbits and rats depended on the state of visual adaptation. In the rabbit, light adaptation enhanced NADPH diaphorase activity in amacrine cells and practically eliminated it in horizontal cells. Dark adaptation induced the opposite effects; the NADPH diaphorase activity was reduced in amacrine cells and enhanced in horizontal cells. Retinas from eyes that were injected intravitreally with L-glutamate exhibited a pattern of NADPH diaphorase activity that was similar to that seen in dark-adapted retinas. In rats, the NADPH diaphorase activity of amacrine and horizontal cells exhibited adaptation dependency similar to that of the rabbit retina. But, the most pronounced effect of dark adaptation in the rat's retina was an enhancement of NADPH diaphorase activity in Müller cells, especially of the endfoot region. Assuming that NADPH diaphorase activity is a marker for NOS, these findings suggest that NO production in the mammalian retina is modulated by the level of ambient illumination and support the notion that NO plays a physiological role in the retina.  相似文献   
995.
Gokce  O. H.  Sears  J. T.  Sahin  T. 《Journal of Electronic Materials》1996,25(9):1531-1538
Journal of Electronic Materials - Low pressure chemical vapor deposition (LPCVD) of tungsten (W) by SiH4 reduction of WF6 on Si(100) surfaces was studied in a single-wafer, cold-wall reactor over a...  相似文献   
996.
997.
998.
999.
1000.
We describe the case of a patient who developed bilateral loss of hearing during intravenous treatment with erythromycin. Predisposing factors may have been reduced renal and hepatic function and treatment with diuretics and aminoglycosides. Recovery was late, but hearing was probably restored to almost pre-treatment level. Patients receiving high doses of erythromycin should, as a routine, be questioned about hearing loss and tinnitus.  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