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   864篇
  免费   20篇
  国内免费   1篇
电工技术   20篇
化学工业   179篇
金属工艺   8篇
机械仪表   17篇
建筑科学   58篇
矿业工程   14篇
能源动力   33篇
轻工业   73篇
水利工程   5篇
石油天然气   4篇
无线电   49篇
一般工业技术   62篇
冶金工业   262篇
原子能技术   8篇
自动化技术   93篇
  2022年   12篇
  2021年   9篇
  2020年   9篇
  2019年   18篇
  2018年   9篇
  2017年   12篇
  2016年   11篇
  2015年   9篇
  2014年   23篇
  2013年   55篇
  2012年   26篇
  2011年   27篇
  2010年   25篇
  2009年   19篇
  2008年   30篇
  2007年   25篇
  2006年   21篇
  2005年   28篇
  2004年   13篇
  2003年   16篇
  2002年   18篇
  2001年   12篇
  2000年   16篇
  1999年   24篇
  1998年   15篇
  1997年   17篇
  1996年   13篇
  1995年   14篇
  1994年   13篇
  1993年   15篇
  1991年   13篇
  1990年   15篇
  1989年   9篇
  1987年   11篇
  1986年   13篇
  1985年   12篇
  1984年   11篇
  1982年   9篇
  1981年   14篇
  1980年   20篇
  1979年   17篇
  1978年   9篇
  1977年   10篇
  1976年   9篇
  1975年   14篇
  1974年   15篇
  1973年   8篇
  1964年   7篇
  1957年   9篇
  1956年   7篇
排序方式: 共有885条查询结果,搜索用时 15 毫秒
101.
Examined racial E effects in counseling-like interviews employing the verbal operant-conditioning paradigm. The general objective was to determine whether significant differences in the conditionability of 12 Black and 12 White female college students, as measured by their emission of positive and negative self-reference emotional affect statements, would obtain when the verbal reinforcement was provided by 2 Black and 2 White Es. A postexperimental inquiry assessed Ss' perceptions of the interviews and their level of awareness of the Es' to influence their verbal behavior. While no definitive conclusions were reached, this study demonstrates that the verbal operant-conditioning paradigm can be used to investigate racial effects on verbal behavior in the counseling interview. Through the use of multiple, biracial Es and Ss, this study goes a step further than other verbal operant-conditioning studies that have explored racial E effects. The absence of significant differences in the E-S racial interaction suggests that race, per se, may not be the most important variable in the E-S (or counselor-client) relationship. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
102.
103.
The feasibility of using a potassium ferioxalate actinometer as a photochemical pyranometer was studied. The preparation, exposure, and spectrophotometric analysis of the pyranometer cell are described. By calibrating it against a Yellot Mark IV solameter, linear correlations were obtained with respect to total insolation and time of exposure. The spectral response, the quantum yields at different wavelengths, the mechanism of photochemical reaction, and the conversion factor for converting the absorption reading into cal/cm2/min are discussed. The advantages of the new pyranometer are its low cost, simplicity of operation and calibration, high sensitivity, and high tolerance to field conditions. It is useful for mapping solar intensity distribution over a wide area.  相似文献   
104.
Demonstrated the importance of the direct hippocampo-anterior thalamic component of the postcommissural fornix in the control of general locomotion and active avoidance; 40 adult male Sprague-Dawley rats were Ss in 3 experiments. Transection of anterior thalamic afferents from the hippocampal formation (subicular cortex), at the point where they exit from the fornix posterior to the septum, enhanced bidirectional active avoidance acquisition and increased general activity. This transection may also interrupt fibers to or from other thalamic nuclei and the anterior septum. However, destruction of connections of the anterior septum with the hippocampus, habenula, and thalamus by transection in the coronal plane anterior to the descending fornix columns, without damage to the subiculothalamic fibers, increased general activity levels without affecting active avoidance behavior. The activity increase in this case resembled that seen after septal lesions rather than that seen after hippocampal lesions. Thus, destruction of a single fornix component contributing afferents to the anterior thalamic nuclei reproduces at least part of the hippocampal syndrome. This suggests that these fibers contribute significantly to the control of these behaviors and may mediate active avoidance changes resulting from hippocampal and fornix damage. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
105.
Responds to 3 issues in G. W. Albee's (see record 1977-29846-001) paper on hedonism in society: the relation between protestantism and economic development, the downfall of the Protestant ethic due to hedonistic consumers, and the rise of capitalism and the repression of sex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
106.
Ernest Rabinowicz 《Wear》1977,42(1):149-156
A number of recent papers report the formation of spherical wear particles during sliding. In this paper a model is developed in which wear particles formed by adhesive wear processes are trapped in cavities in the sliding surfaces and become smoothed by burnishing processes. It is shown that the reported spherical particle diameters and lengths of sliding are consistent with this model. According to the model, spherical particles are only to be anticipated in slow uniaxial sliding, in fretting and within cracks of a material being fatigued.  相似文献   
107.
The analytical electron microscope (AEM) was used to examine the microstructure of type 316LN stainless steel alloys which had been annealed for 50 to 300 hours in the temperature range 600 to 700 °C. The M23C6 carbide chemistry and distribution are described as a function of heat treatment.X-ray spectroscopy in the AEM revealed significant chromium depletion at grain boundaries in the vicinity of carbides for samples aged at 50 and 100 hours at 650 °C and 100 and 300 hours at 700 °C, with lower grain boundary chromium values observed at 650 °C than at 700 °C. The width of the chromium depleted zone normal to the grain boundaries increased with increasing annealing time and/or temperature. Measurements of chromium concentration along the grain boundaries away from a carbide were made after aging at 700 °C for 100 hours, and the chromium level rose steadily until the bulk value was reached at a distance of ~3μm from the carbide. The width of the chromium depleted zone normal to the boundaries in the same sample was an order of magnitude less. Some molybdenum depletion was also found at the grain boundaries, and the Mo-depletion profiles were in form and extent similar to the chromium results. Simple thermodynamic models were used to calculate the equilibrium value of chromium at the carbide-matrix interface, and the chromium distribution along and normal to the grain boundaries. The results of these models agreed well with the AEM results, and the agreement can be improved by considering the effect of electron probe configuration on the AEM measurements. The calculated thermodynamic data and the AEM results were related to the corrosion behavior of the alloys. The occurrence of severe asymmetries in some concentration profiles normal to the grain boundaries, which increased with increasing annealing temperature or time, was shown to be due to boundary movement during the discontinuous precipitation of M23C6 carbides.  相似文献   
108.
109.
The nature of the distinction between primary and secondary processes, as described by Freud, has relevancy for both a cognitive psycholoy and a psychology of motivation. Several issues arising from an examination of the 2 processes are examined. Possible empirical approaches to the basic problems are presented. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
110.
In this paper a number of new channel-routing algorithms are presented. the routing strategy is based on parallel bubble-sorting and river-routing techniques. an important concept introduced is the POTENTIAL function, which serves as a measure of the degree of difficulty of a particular channel-routing problem. Both non-Manhattan wires and overlapping wires are used. Although the methods are initially derived for two-layer routing with two-terminal nets only, extensions to multiterminal nets and three-layer routing have been made. Preliminary results indicate that in many instances the new algorithm outperforms the traditional approaches.  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