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   75535篇
  免费   15010篇
  国内免费   90篇
电工技术   2402篇
综合类   440篇
化学工业   28422篇
金属工艺   1031篇
机械仪表   1525篇
建筑科学   3871篇
矿业工程   324篇
能源动力   1570篇
轻工业   10722篇
水利工程   576篇
石油天然气   170篇
武器工业   1篇
无线电   8467篇
一般工业技术   17593篇
冶金工业   3452篇
原子能技术   161篇
自动化技术   9908篇
  2023年   754篇
  2022年   602篇
  2021年   1353篇
  2020年   2324篇
  2019年   3962篇
  2018年   3916篇
  2017年   4095篇
  2016年   4735篇
  2015年   4898篇
  2014年   5018篇
  2013年   7456篇
  2012年   4057篇
  2011年   3993篇
  2010年   4102篇
  2009年   4036篇
  2008年   3489篇
  2007年   3120篇
  2006年   2785篇
  2005年   2439篇
  2004年   2281篇
  2003年   2160篇
  2002年   1992篇
  2001年   1577篇
  2000年   1483篇
  1999年   933篇
  1998年   630篇
  1997年   534篇
  1996年   546篇
  1995年   479篇
  1994年   471篇
  1993年   522篇
  1992年   414篇
  1991年   345篇
  1990年   357篇
  1989年   405篇
  1988年   322篇
  1987年   343篇
  1986年   364篇
  1985年   406篇
  1984年   383篇
  1983年   361篇
  1982年   326篇
  1981年   402篇
  1980年   298篇
  1979年   317篇
  1977年   276篇
  1976年   289篇
  1975年   324篇
  1974年   289篇
  1973年   449篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
Ob Betriebsvereinbarungen im Sinne des § 4 Abs. 1 BDSG eine „andere Rechtsvorschrift” sind und damit die Regelungen des BDSG einschr?nken dürfen, geh?rt zu den Standardfragen des praktischen Arbeitnehmerdatenschutzes. Die Autoren befürworten eine weite betriebliche Regelungskompetenz, beschr?nken diese aber zum Schutz der Arbeitnehmer durch eine Reihe datenschutzrechtlicher Mindestanforderungen, die Betriebsvereinbarungen einzuhalten haben.  相似文献   
33.
Flame structure and NO emission characteristics in counterflow diffusion flame of blended fuel of H2/CO2/Ar have been numerically simulated with detailed chemistry. The combination of H2, CO2 and Ar as fuel is selected to clearly display the contribution of hydrocarbon products to flame structure and NO emission characteristics due to the breakdown of CO2. A radiative heat loss term is involved to correctly describe the flame dynamics especially at low strain rates. The detailed chemistry adopts the reaction mechanism of GRI 2.11, which consists of 49 species and 279 elementary reactions. All mechanisms including thermal, NO2, N2O and Fenimore are taken into account to separately evaluate the effects of CO2 addition on NO emission characteristics. The increase of added CO2 quantity causes flame temperature to fall since at high strain rates a diluent effect is prevailing and at low strain rates the breakdown of CO2 produces relatively populous hydrocarbon products and thus the existence of hydrocarbon products inhibits chain branching. It is also found that the contribution of NO production by N2O and NO2 mechanisms are negligible and that thermal mechanism is concentrated on only the reaction zone. As strain rate and CO2 quantity increase, NO production is remarkably augmented. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   
34.
35.
Determined the specific type of sexual functioning deficits and the relationship between global sexual satisfaction and adjustment in 2 related life areas (marital relationship and body image) for 2 groups of cancer patients at high risk for sexual difficulties. The 2 groups included 16 27–67 yr old females with Stage 2 breast cancer and 16 31–65 yr old females with gynecologic cancer. These Ss were compared to 16 healthy female outpatients (controls). Measures included the Sexual Activities scale from the Derogatis Sexual Functioning Inventory, a modified version of the Dyadic Assessment Scale (marital adjustment), a global sexual evaluation, and a body-image scale. Analyses revealed that the aspects of sexual functioning for breast-cancer and gynecologic-cancer Ss that differed from those of controls were the frequency of sexual behaviors and the level of sexual arousal. Whereas Ss' evaluations of their current sexual life had no relationship to their marital-adjustment ratings, analyses suggested that body-image disruption may be a prevalent problem for gynecologic cancer patients. Data suggest that cancer diagnosis and treatment are instrumental in producing reductions in sexual activity and arousability. (34 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
36.
37.
38.
Tracking targets of interest is one of the major research areas in radar surveillance systems. We formulate the problem as incomplete data estimation and apply EM to the MAP estimate. The resulting filter has a recursive structure analogous to the Kalman filter. The advantage is that the measurement‐update deals with multiple measurements in parallel and the parameter‐update estimates the system parameters on the fly. Experiments tracking separate targets in parallel show that tracking maintenance ratio of the proposed system is better than that of NNF and RMS position error is smaller than that of PDAF. Also, the system parameters are correctly obtained even from incorrect initial values. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   
39.
40.
A new efficient method for synthesising nitriles, important organic reagents, is reported in this paper. In an environmentally benign solvent‐free system, aryl carboxylic acids were converted into the corresponding nitriles via one‐pot reactions, by amidation with ethyl carbamate followed by dehydration with thionyl chloride, in excellent yields. The results showed that the method has the advantages of lower cost, higher yield, less pollution and greater ease of work‐up. Copyright © 2008 Society of Chemical Industry  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