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   25905篇
  免费   2316篇
  国内免费   1075篇
电工技术   1618篇
综合类   3420篇
化学工业   3642篇
金属工艺   880篇
机械仪表   1062篇
建筑科学   2812篇
矿业工程   1003篇
能源动力   730篇
轻工业   1492篇
水利工程   910篇
石油天然气   1072篇
武器工业   361篇
无线电   2200篇
一般工业技术   1509篇
冶金工业   2105篇
原子能技术   192篇
自动化技术   4288篇
  2024年   62篇
  2023年   235篇
  2022年   395篇
  2021年   536篇
  2020年   585篇
  2019年   517篇
  2018年   519篇
  2017年   713篇
  2016年   933篇
  2015年   943篇
  2014年   1553篇
  2013年   1326篇
  2012年   1656篇
  2011年   1966篇
  2010年   1562篇
  2009年   1570篇
  2008年   1463篇
  2007年   1733篇
  2006年   1621篇
  2005年   1367篇
  2004年   1143篇
  2003年   1087篇
  2002年   905篇
  2001年   786篇
  2000年   582篇
  1999年   448篇
  1998年   306篇
  1997年   242篇
  1996年   196篇
  1995年   179篇
  1994年   149篇
  1993年   95篇
  1992年   96篇
  1991年   64篇
  1990年   78篇
  1989年   38篇
  1988年   43篇
  1987年   43篇
  1986年   28篇
  1985年   141篇
  1984年   242篇
  1983年   281篇
  1982年   200篇
  1981年   308篇
  1980年   115篇
  1979年   37篇
  1978年   38篇
  1977年   13篇
  1975年   22篇
  1974年   22篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Presents the citation, biography, and selected bibliography for Bruce E. Wampold, the 2007 recipient of the American Psychological Association's Award for Distinguished Professional Contributions to Applied Research. Also presented is an article based on the author's award address delivered at the APA's 115th annual meeting, held August 17-20, 2007, in San Francisco, California. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
62.
This study examined whether social phobics differed from nonanxious controls in occupational adjustment. Results indicated that generalized and nongeneralized social phobics, in contrast to controls, were underemployed and believed that their supervisor would rate them as less dependable. Nongeneralized social phobics and controls believed their supervisor would rate them higher in work role conformance and likelihood of advancement than did generalized social phobics. Generalized socially phobic women, in contrast to nongeneralized and control group women, were more likely to be employed in noninterpersonally oriented jobs. Generalized social phobics were more anxious than controls when starting their current job but did not differ in job satisfaction. Results are discussed relative to the nature of social phobia, subtype differences, and counseling services. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
63.
The authors conducted a meta-analysis of published studies to (a) evaluate the premise that a history of major depression is associated with failure to quit smoking and (b) identify factors that moderate the relationship between history of depression and cessation outcome. Fifteen studies met the selection requirements and were coded for various study methodology and treatment characteristics. DSTAT was used to calculate individual study effect sizes, determine the mean effect size across studies. and test for moderator effects. No differences in either short-term (≤ 3 months) or long-term abstinence rates (≥ 6 months) were observed between smokers positive versus negative for history of depression. Lifetime history of major depression does not appear to be an independent risk factor for cessation failure in smoking cessation treatment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
64.
陈志华 《电力学报》2004,19(3):253-255
每个国定的经济能不能持续发展 ;能不能在激烈的国际竞争中始终不衰 ;关键在于这个国家能不能开发人力资源 ;占领人力资源、用好人力资源。  相似文献   
65.
从能力培养的角度较全面、系统地阐述了教师组织课堂教学的基本方法和手段。并针对职业教育的培养要求及学生的心理特点,在有效整合学校各种教学资源、努力实现学生知识结构与能力培养和谐统一方面进行了一些有益探索和实践。  相似文献   
66.
The price of SO2 permits and the volume of trading under the US Acid Rain Program have been lower than expected. This can be explained by the creation and distribution of more permits than were initially authorized, by the sale of permits by high cost abaters who are subject to more stringent local emission constraints or who have irreversibly invested in high cost abatement technologies and by the deregulation of the natural gas and railroad industries which, in combination with incentives for cost-cutting under the new market approach to SO2 control, has lowered marginal costs of abatement curves and made them more uniform across powerplants. The low price of permits and low trading volume are evidence that market approaches to pollution control can be more cost-effective than command and control regulations. The effect of public policies and technological changes on the allowance market are usefully examined in the context of an ideal market, in which the equilibrium price of allowances equals the marginal cost of abatement of individual powerplants. Using recent data from Coggins and Swinton (1996), we are able to explain the current price of permits with some accuracy.  相似文献   
67.
A 1% Pd catalyst (38% dispersion) was prepared by impregnating a γ-alumina with palladium acetylacetonate dissolved in acetone. The behaviour of this catalyst in oxidation and steam reforming (SR) of propane was investigated. Temperature-programmed reactions of C3H8 with O2 or with O2 + H2O were carried out with different stoichiometric ratios S(S =[O2]/5[C3H8]). The conversion profiles of C3H8 for the reaction carried out in substoichiometry of O2 (S < 1) showed two discrete domains of conversion: oxidation at temperatures below 350°C and SR at temperatures above 350°C. The presence of steam in the inlet gases is not necessary for SR to occur: there is sufficient water produced in the oxidation to form H2 and carbon oxides by this reaction. Contrary to what was observed with Pt, an apparent deactivation between 310 and 385°C could be observed with Pd in oxidation. This is due to a reduction of PdOx into Pd0, which is much less active than the oxide in propane oxidation. Steam added to the reactants inhibits oxidation while it prevents the reduction of PdOx into Pd0. Compared to Pt and to Rh, Pd has a higher thermal resistance: no deactivation occurred after treatment up to 700°C and limited deactivation after treatment up to 900°C, provided that the catalyst is maintained in an oxygen-rich atmosphere during the cooling.  相似文献   
68.
电工实践教学改革与实践   总被引:1,自引:1,他引:0  
电工实践教学是培养大学生电类工程能力的重要环节,本文介绍我们以培养人才为中心在电工实习基地建设;实践教学内容,方法和手段等方面进行的改革与实践。  相似文献   
69.
由进口电性能仪配上自制的高温系统,计算机自动采集数据,配置成一套高低温电性参数测定装置,该装置的特点是,升温快,炉体小巧,炉芯可更换盛液氮装置,屏蔽良好,等温区长,温工及参数测量精确可靠。  相似文献   
70.
张家桂 《控制与决策》1994,9(6):459-463
本文提出励磁电流可自动控制的他励式双高调速系统设计方案。系统在提升特别是在下放重物时,具有较硬的机械性;在负载10-100%的变化范围内,可实现最大偏差Δnmax/nmin100%≤10%,调速范围D≥10;在满载运行条件下,可节约电能80%以上。  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