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   13927篇
  免费   361篇
  国内免费   21篇
电工技术   200篇
综合类   12篇
化学工业   3074篇
金属工艺   228篇
机械仪表   289篇
建筑科学   650篇
矿业工程   97篇
能源动力   382篇
轻工业   980篇
水利工程   130篇
石油天然气   162篇
武器工业   1篇
无线电   838篇
一般工业技术   2028篇
冶金工业   3417篇
原子能技术   139篇
自动化技术   1682篇
  2022年   118篇
  2021年   172篇
  2020年   145篇
  2019年   160篇
  2018年   180篇
  2017年   181篇
  2016年   205篇
  2015年   166篇
  2014年   227篇
  2013年   809篇
  2012年   446篇
  2011年   628篇
  2010年   414篇
  2009年   439篇
  2008年   572篇
  2007年   557篇
  2006年   546篇
  2005年   449篇
  2004年   364篇
  2003年   359篇
  2002年   377篇
  2001年   241篇
  2000年   231篇
  1999年   252篇
  1998年   245篇
  1997年   237篇
  1996年   253篇
  1995年   248篇
  1994年   251篇
  1993年   297篇
  1992年   249篇
  1991年   189篇
  1990年   201篇
  1989年   217篇
  1988年   171篇
  1987年   214篇
  1986年   204篇
  1985年   252篇
  1984年   228篇
  1983年   207篇
  1982年   186篇
  1981年   191篇
  1980年   164篇
  1979年   181篇
  1978年   181篇
  1977年   139篇
  1976年   147篇
  1975年   175篇
  1974年   137篇
  1973年   132篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
Amphetamine and cocaine dependence present significant public health concerns, yet no broadly effective pharmacotherapy for stimulant dependence has been developed. Two human laboratory studies are reviewed that tested the ability of aripiprazole, a novel antipsychotic with partial agonist activity at D2 dopamine receptors, to alter the behavioral effects of stimulants using d-amphetamine as a model agent. In each of these experiments, volunteers learned to discriminate 15 mg d-amphetamine (i.e., ≥80% drug-appropriate responding over 4 consecutive sessions). The effects of a range of doses of d-amphetamine (0, 2.5, 5, 10, and 15 mg) were then tested alone and following pretreatment with aripiprazole (20 mg in Experiment 1; 10 mg in Experiment 2). In Experiment 1, aripiprazole (20 mg) attenuated the discriminative stimulus and many of the subject-rated effects of amphetamine. Aripiprazole alone produced performance decrements. To determine whether a lower dose of aripiprazole would also attenuate the behavioral effects of d-amphetamine without impairing performance, Experiment 2 was conducted. Aripiprazole (10 mg) failed to alter the discriminative-stimulus effects but attenuated some of the subject-rated effects of d-amphetamine. This dose of aripiprazole did not impair performance. The results of these experiments indicate that aripiprazole may have clinical utility in treating stimulant dependence. Future human laboratory research should better model the clinical use of aripiprazole by examining the effects of chronic aripiprazole combined with either methamphetamine or cocaine in dependent individuals. A large-scale clinical trial is also needed to evaluate the efficacy of aripiprazole for the treatment of stimulant dependence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
4.
Selected aromatic amides were used to model the chemical reactivity of aromatic polyamides found in thin‐film composite reverse osmosis (RO) membranes. Chlorination and possible amide bond cleavage of aromatic amides upon exposure to aqueous chlorine, which can lead to membrane failure, were investigated. Correlations are made of the available chlorine concentration, pH, and exposure time with chemical changes in the model compounds. From the observed reactivity trends, insights are obtained into the mechanism of RO membrane performance loss upon chlorine exposure. Two chemical pathways for degradation are shown, one at constant pH and another that is pH‐history dependent. An alternative strategy is presented for the design of chlorine‐resistant RO membranes, and an initial performance study of RO membranes incorporating this strategy is reported. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1173–1184, 2003  相似文献   
5.
Removal of gold from basic solutions containing [Au(CN)2]? has been demonstrated using the inherently conducting polymer polypyrrole. Polymers containing sulfonated aromatic dopants have been found to display a significant ability to remove gold from such solutions. Experiments performed in solutions containing both gold and copper cyanide complexes indicate that the recovery process is not highly selective. However, the polypyrroles used display significantly faster rates of gold recovery than activated carbon. © 2003 Society of Chemical Industry  相似文献   
6.
很多低压降稳压器都带有一个使能输入脚,它可以用作一个廉价的电压监控IC。虽然使能脚通常是用于切断稳压器的输出以节省功耗,但增加几个分立元件就可以使稳压器输出控制相应输入电压下的通、断。因此,可以将此电路用作一个电压监控器或一个特性受控的线性稳压器。  相似文献   
7.
Scanning acoustic microscopy of SCS-6 silicon carbide fiber reveals large radial variations in acoustic reflectivity associated with the chemical composition and microstructure of a given fiber region. Rayleigh wave fringe patterns observed in each of five subregions are used to calculate the average Young modulus of that subregion. The Young modulus is found to increase monotonically from 40 GPa in the carbon core to a value of 413 GPa in the stoichiometric SiC region. The effective Young modulus of the fiber as a whole is estimated from the moduli of the individual regions and it is compared with mechanical measurements reported in the literature.  相似文献   
8.
Effective systems development techniques attract a lot of attention, but little has been done to effectively address systems maintenance. This article describes an effective, proven approach to resurrecting existing systems and Increasing their useful life, using a system that employs both software tools and a rigorous methodology.  相似文献   
9.
10.
A summary of points of agreement and disagreement among the preceding articles is presented. Attention is called to implicit assumptions which if openly acknowledged would improve dialogue on peer review issues. Pertinent events that have occurred since the Anaheim symposium are reviewed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  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