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   2558篇
  免费   37篇
  国内免费   4篇
电工技术   19篇
化学工业   458篇
金属工艺   52篇
机械仪表   36篇
建筑科学   93篇
矿业工程   5篇
能源动力   45篇
轻工业   200篇
水利工程   8篇
石油天然气   28篇
无线电   120篇
一般工业技术   345篇
冶金工业   833篇
原子能技术   31篇
自动化技术   326篇
  2021年   17篇
  2020年   16篇
  2019年   15篇
  2018年   22篇
  2017年   23篇
  2016年   33篇
  2014年   25篇
  2013年   164篇
  2012年   48篇
  2011年   73篇
  2010年   66篇
  2009年   71篇
  2008年   66篇
  2007年   79篇
  2006年   79篇
  2005年   76篇
  2004年   62篇
  2003年   53篇
  2002年   66篇
  2001年   60篇
  2000年   50篇
  1999年   40篇
  1998年   81篇
  1997年   80篇
  1996年   68篇
  1995年   55篇
  1994年   43篇
  1993年   57篇
  1992年   47篇
  1991年   31篇
  1990年   46篇
  1989年   43篇
  1988年   36篇
  1987年   36篇
  1986年   48篇
  1985年   49篇
  1984年   35篇
  1983年   48篇
  1982年   47篇
  1981年   30篇
  1980年   24篇
  1979年   50篇
  1978年   46篇
  1977年   45篇
  1976年   54篇
  1975年   19篇
  1974年   30篇
  1973年   36篇
  1972年   30篇
  1969年   19篇
排序方式: 共有2599条查询结果,搜索用时 373 毫秒
21.
Under oxygen-rich conditions in H2 + NO + O2 mixtures, Pd/V2O5/Al2O3 catalysts are active and highly selective (~80%) for NOx reduction to N2. In situ DRIFT spectroscopy and reactor data show that the system operates via formation of NHx species on the highly dispersed V2O5 component. Both NH3 and NH4 + are formed, with the latter dominant. The role of the palladium component is also discussed.  相似文献   
22.
Study of fluorescence emission from flexible PVC‐based formulations, colored by exposure to road asphalt or degraded thermally or by UV aging, shows that fluorescent species are formed during the interaction of PVC with road asphalt. For the conditions found in exterior automotive applications, no other known degradation causes development of fluorescence. Flexible PVC‐based formulations discolored by asphalt staining or degraded thermally at moderate temperatures bleach completely under conditions of natural or artificial weathering. A simple technique, using visually observed photoluminescence and photobleaching, can thus identify photoactive groups formed during the interaction of PVC with road asphalt. Application of this test method will allow selective improvement of failed asphalt resistance without treating the “overall” stability of a compound.  相似文献   
23.
Changes in maladaptive cognitions may constitute therapeutic processes of multidisciplinary pain programs. A cross-lagged panel design was used to determine whether (a) early-treatment cognitive change predicted late-treatment outcome index change, but not vice versa; and (b) these effects remained significant with depression change controlled. Ninety chronic pain patients, in a 4-week multidisciplinary program, completed measures of catastrophizing, pain helplessness, depression, pain, interference, and activity level at pre-, mid-, and posttreatment. With depression changes controlled, early-treatment catastrophizing and pain helplessness changes predicted late-treatment outcome index changes, but not vice versa; early-treatment depression changes predicted late-treatment activity changes, but not vice versa. Findings advance understanding of pain treatment process and suggest that negative cognition changes may indeed affect improvements in treatment outcome. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
24.
Investigated the relationship between Type A (coronary prone) behavior, aerobic fitness, and cardiovascular recovery from stress in 56 male undergraduates. Ss were tested for actual aerobic power and Type A behavior on the Jenkins Activity Survey—Form T before performing the Stroop Color–Word Interference Test. Type A behavior was related to speed of recovery following the test, with Type As being slower to return to baseline heart rate levels than Type B (noncoronary prone) Ss. Physiological and cognitive variables affecting speed of recovery from stress are examined, and the lack of effect of fitness on recovery is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
25.
26.
27.
Expected value judgments of 5-, 6-, 8-, and 10-yr-olds were studied by using an information integration approach. Children saw roulette-type games with prizes of crayons. They made judgments in a continuous scale of how happy a puppet playing the game would be. In one task, probability and value of a single winning outcome were varied factorially. All ages took both cues into account. Young children used an additive integration rule, whereas children 8 yrs and older used the multiplying rule as predicted by mathematical theory. A 2nd task contained games with both 1 and 2 alternative prizes. At all ages, data patterns were similar to the normative predictions. Even young children showed some understanding of probability dependence. A serial version of the addition strategy may contribute to advanced performance in the 2-prize task. These results are consistent with conceptual understanding of expected value. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
28.
Banaji and Crowder (see record 1990-00387-001) contend "that the movement to develop an ecologically valid psychology of memory has proven itself largely bankrupt" (p. 1185). The authors have two primary concerns. First, they believe that it is rare for studies of real-world cognition to support conclusions that generalize broadly. Second, they are concerned that such studies may be inherently incapable of making significant theoretical or methodological contributions. The research program outlined here can be viewed as a response (in the form of a case study) to the Banaji and Crowder position. Specifically, this project has adopted both theoretical and methodology perspectives from the study of real-world memory to address a long-standing issue in the mainstream memory literature. The project itself was designed to characterize the strategies used to estimate event frequency and the conditions that foster the use of these strategies. A valid model of the estimation process is necessary in order to understand the encoding and representation of event frequency. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
29.
The exact distributions associated with the current compendial test requirements are generated by resorting to the well known Computer Intensive Algorithm method to establish the exact percentage point (limit) for RSD, corresponding to each selected cut-off probability level (confidence level) for each of the four possible experimental outcomes based on the USP-NF test requirements. A table is constructed to present the two-dimensional power function. The similarities between these tabular values and the current compendial RSD limits for 10 and 30 dosage units are extremely remarkable.

Minor differences exist, however. It is suggested that both the theoretical as well as the numerical approaches should be carried out to arrive at a comprehensive solution.  相似文献   
30.
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