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   21313篇
  免费   2325篇
  国内免费   1357篇
电工技术   1722篇
技术理论   1篇
综合类   2424篇
化学工业   1258篇
金属工艺   1245篇
机械仪表   2037篇
建筑科学   2252篇
矿业工程   412篇
能源动力   697篇
轻工业   1742篇
水利工程   333篇
石油天然气   580篇
武器工业   313篇
无线电   1154篇
一般工业技术   2650篇
冶金工业   2042篇
原子能技术   132篇
自动化技术   4001篇
  2024年   153篇
  2023年   352篇
  2022年   607篇
  2021年   658篇
  2020年   724篇
  2019年   624篇
  2018年   655篇
  2017年   755篇
  2016年   846篇
  2015年   864篇
  2014年   1287篇
  2013年   1409篇
  2012年   1369篇
  2011年   1657篇
  2010年   1201篇
  2009年   1296篇
  2008年   1167篇
  2007年   1354篇
  2006年   1237篇
  2005年   1097篇
  2004年   975篇
  2003年   798篇
  2002年   717篇
  2001年   634篇
  2000年   470篇
  1999年   382篇
  1998年   305篇
  1997年   282篇
  1996年   239篇
  1995年   178篇
  1994年   148篇
  1993年   108篇
  1992年   64篇
  1991年   56篇
  1990年   47篇
  1989年   36篇
  1988年   30篇
  1987年   22篇
  1986年   19篇
  1985年   15篇
  1984年   14篇
  1983年   16篇
  1982年   11篇
  1980年   11篇
  1966年   10篇
  1965年   12篇
  1964年   11篇
  1963年   10篇
  1959年   9篇
  1957年   10篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Behaviors and emotions during specific visits may reveal the interpersonal processes of mother-daughter ties, yet most research uses global assessments of these ties. Forty-eight mother-daughter pairs participated in audiotaped conversations and completed surveys. All mothers were over age 70 and in good health. Daughters tended to take a central role in structuring the conversations. Conversations were characterized by high levels of felt and expressed positive emotions and behaviors for mothers and daughters. Nevertheless, mothers reported more positive and fewer negative emotions, whereas daughters expressed more positive behaviors than did mothers. Mothers' positive feelings and behaviors were associated with daughters'. Finally, mothers' and daughters' emotions and behaviors were associated with their destructive responses to being upset with each other, providing support for the ambivalence perspective of parent-offspring relationships. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
102.
The purpose of this study was to examine predictors and consequences of spouses' involvement in each others' strategies for pursuing important personal goals called life tasks. Husbands and wives within 39 short- and long-term marriages described five life tasks and provided appraisals of whether each was shared with their spouse. Participants later completed 14 consecutive diary entries recording daily life task pursuit strategies, the extent of spouse involvement in each, and measures of positive and negative affect. Results indicated that interdependence in life task appraisals prospectively predicted greater spouse involvement, and greater spouse involvement was associated with more positive affect for that day. Life task appraisals may provide avenues for understanding couples' strategies for dealing with goals or stressors and how those strategies affect mood. (PsycINFO Database Record (c) 2011 APA, all rights reserved)  相似文献   
103.
利用Glejser检验方法拟舍出刀具磨损过程残差模型,在此基础上,计算换刀时刻的过程能力指数,并且根据企业所要求的最低过程能力指数,计算刀具的质量寿命,提出将刀具的切削寿命和质量寿命结合起来进行换刀决策的方法。  相似文献   
104.
The environmental and socio‐economic impacts of biomass utilization by co‐firing with brown coal in an existing thermoelectric unit in Greece or through its pure combustion in a new plant were studied and evaluated in this work. The 125 MWe lignite‐fired power plant in Ptolemais Power Station (Western Macedonia) was used as reference system. The environmental benefits of the alternative biomass exploitation options were quantified based on the life cycle assessment methodology, as established by SETAC, while the BIOSEM technique was used to carry out socio‐economic calculations. The obtained results showed clear environmental benefits of both biomass utilization alternatives in comparison with the reference system. In addition, co‐firing biomass with lignite in an existing unit outperforms the combustion of biomass exclusively in a new plant, since it exhibits a better environmental performance and it is a low risk investment with immediate benefits. A biomass combustion unit requires a considerably higher capital investment and its benefits are more evident in the long run. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   
105.
A model for building integrated photovoltaic systems has been developed and implemented in a dynamic simulation tool. This tool takes into account the thermal interactions between the PV collector and the building. The influence of the type of integration upon the PV collector efficiency has been evaluated and hybrid PV/air collectors have been studied. An overall efficiency is defined, including the production of electricity and heat. A case study has been performed on two different typical buildings. In the case of a multi-crystalline silicon PV collector integrated on the roof of a single family house located in Paris, the efficiency of unventilated PV modules fixed on the roof is 14%. If the PV collector is used to preheat the ventilation air, the efficiency reaches 20%. A proper building integration also improves the environmental balance of PV technologies over their life cycle.  相似文献   
106.
让住户满意的物业管理职能研究   总被引:1,自引:0,他引:1  
从使住户满意的角度研究了物业管理中的计划、组织、领导、控制和创新五项职能,以指导物业管理企业提高管理水平和服务质量.  相似文献   
107.
In this paper, we employ a nonlinear adaptive mechanism to globally stabilize nth-order reactions.  相似文献   
108.
A series of polyesters was prepared to evaluate hydrolytic stability as a function of cyclohexyl dibasic acid content. The three cyclohexyl dibasic acids: 1,2; 1,3; and 1,4 were formulated into polyesters with two glycols. The proportion of cis and trans isomers was evaluated via 1H NMR. The hydrolytic stability of short chain polyesters was evaluated in an acetone/water mixture which solubilized the polyesters to mimic oligoester behavior within a thermosetting polyester coating environment. The rate of hydrolysis was monitored by acid titration and corroborated by GPC. Surprisingly, 1,2-cylohexyl diacid-based polyesters were robust, and 1,3-cyclohexyl diacid-based polyesters were the most susceptible to hydrolysis. Evidently, a 1,2-anchimeric effect for cyclohexyl dibasic acid polyesters was not an important consideration, while the 1,3-cyclohexyl ester interaction was. Consequently, an anomeric effect was proposed. Presented at the 81st Annual Meeting of the Federation of Societies for Coatings Technology, November 12–14, 2003, in Philadelphia, PA.  相似文献   
109.
The fatigue behaviour of bolts under axial load has always been considered from the component point of view for which fatigue limit is usually taken equal to 50 MPa, and few results are available to designers for limited lifetimes. Here, we take up this problem from a material point of view using a local approach. For each case of fatigue testing, using finite‐element (FE) model of the bolt, we determine the stabilized local stress at the root of the first thread in contact with the nut. To characterize bolt behaviour with these numerical results, we use Dang Van multiaxial fatigue criterion for which we extend application to the medium fatigue life. These results can be correlated with the experimental numbers of cycles to failure to determine material parameters of the generalized criterion. Using statistical Gauss method, we can make lifetime predictions for any level of risk of failure. In addition, we propose an analytical model to rapidly determine the local stress condition from nominal loading data (mean stress and alternating stress). This model dispenses us from a new modelling if the bolt is stressed in the same manner as the bolts used for behaviour characterization. Using this model and the generalized criterion, it is extremely easy to make lifetime predictions whatever the risk considered.  相似文献   
110.
Does forgiveness predict later conflict resolution in married couples? Twelve-month follow-up data on conflict resolution were collected from the couples studied by F. D. Fincham, S. R. Beach, and J. Davila (see record 2004-11293-007), who had provided earlier reports of forgiveness and conflict resolution. For wives, the positive dimension of forgiveness or benevolence predicted husbands' later reports of better conflict resolution controlling for initial levels of conflict resolution. This finding was independent of wives' marital satisfaction and the degree of hurt engendered by husbands' transgressions. For husbands, the only predictor of wives' reports of later conflict resolution was initial level of conflict resolution. The findings are discussed in terms of the direction of effect between forgiveness and conflict resolution and of the mechanisms that might link them. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  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