全文获取类型
收费全文 | 16698篇 |
免费 | 591篇 |
国内免费 | 25篇 |
专业分类
电工技术 | 225篇 |
综合类 | 13篇 |
化学工业 | 3918篇 |
金属工艺 | 300篇 |
机械仪表 | 394篇 |
建筑科学 | 740篇 |
矿业工程 | 103篇 |
能源动力 | 450篇 |
轻工业 | 1543篇 |
水利工程 | 161篇 |
石油天然气 | 185篇 |
武器工业 | 1篇 |
无线电 | 1038篇 |
一般工业技术 | 2537篇 |
冶金工业 | 3575篇 |
原子能技术 | 162篇 |
自动化技术 | 1969篇 |
出版年
2022年 | 238篇 |
2021年 | 334篇 |
2020年 | 248篇 |
2019年 | 273篇 |
2018年 | 322篇 |
2017年 | 335篇 |
2016年 | 356篇 |
2015年 | 284篇 |
2014年 | 357篇 |
2013年 | 1043篇 |
2012年 | 638篇 |
2011年 | 804篇 |
2010年 | 556篇 |
2009年 | 575篇 |
2008年 | 685篇 |
2007年 | 646篇 |
2006年 | 624篇 |
2005年 | 520篇 |
2004年 | 421篇 |
2003年 | 407篇 |
2002年 | 428篇 |
2001年 | 278篇 |
2000年 | 262篇 |
1999年 | 285篇 |
1998年 | 315篇 |
1997年 | 298篇 |
1996年 | 293篇 |
1995年 | 285篇 |
1994年 | 270篇 |
1993年 | 313篇 |
1992年 | 252篇 |
1991年 | 198篇 |
1990年 | 211篇 |
1989年 | 225篇 |
1988年 | 173篇 |
1987年 | 218篇 |
1986年 | 213篇 |
1985年 | 253篇 |
1984年 | 227篇 |
1983年 | 203篇 |
1982年 | 182篇 |
1981年 | 194篇 |
1980年 | 163篇 |
1979年 | 179篇 |
1978年 | 183篇 |
1977年 | 141篇 |
1976年 | 154篇 |
1975年 | 173篇 |
1974年 | 134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.
4.
5.
6.
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
7.
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
8.
Shamachary Sathish John H. Cantrell William T. Yost 《Journal of the American Ceramic Society》1996,79(1):209-212
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
9.
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
10.