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   20552篇
  免费   612篇
  国内免费   24篇
电工技术   214篇
综合类   17篇
化学工业   4259篇
金属工艺   492篇
机械仪表   363篇
建筑科学   923篇
矿业工程   88篇
能源动力   532篇
轻工业   1382篇
水利工程   260篇
石油天然气   195篇
武器工业   1篇
无线电   1405篇
一般工业技术   3356篇
冶金工业   4506篇
原子能技术   167篇
自动化技术   3028篇
  2021年   240篇
  2020年   198篇
  2019年   263篇
  2018年   296篇
  2017年   302篇
  2016年   365篇
  2015年   291篇
  2014年   456篇
  2013年   1236篇
  2012年   750篇
  2011年   943篇
  2010年   754篇
  2009年   760篇
  2008年   883篇
  2007年   951篇
  2006年   781篇
  2005年   738篇
  2004年   648篇
  2003年   606篇
  2002年   581篇
  2001年   363篇
  2000年   365篇
  1999年   359篇
  1998年   438篇
  1997年   380篇
  1996年   336篇
  1995年   345篇
  1994年   298篇
  1993年   343篇
  1992年   305篇
  1991年   216篇
  1990年   267篇
  1989年   274篇
  1988年   254篇
  1987年   246篇
  1986年   276篇
  1985年   296篇
  1984年   294篇
  1983年   289篇
  1982年   231篇
  1981年   256篇
  1980年   253篇
  1979年   251篇
  1978年   227篇
  1977年   229篇
  1976年   205篇
  1975年   195篇
  1974年   174篇
  1973年   179篇
  1972年   111篇
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
81.
This research produced evidence that an aspect of visual long-term memory—memory for lateral orientation of pictures—is constrained by a viewer-centered or egocentric reference frame. Subjects in Experiment 1 verbally encoded and then verbally recalled the locations of objects within scenic pictures. Recall of locations in terms of left-right directions (using a viewer-centered frame) exceeded recall of locations in terms of relative proximities to features of the room (using an environmental frame), even if the relative proximities had been verbalized at input. Subjects in Experiment 2 viewed half of a list of pictures directly and the remainder, reflected in a mirror. They then took a test in which they classified old pictures—all viewed directly— as "same-orientation" or "reversed." Performance was much better with a viewer-centered definition of same orientation (Does the picture appear the same way around?) than with an environmental definition (Is the picture the same way around on the screen?), even with forewarning of an environmental orientation test. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
82.
Methods for modeling and managing uncertainty in computer vision systems have received increased attention in recent years. Automatic target recognition is one application area of computer vision where the demands are particularly acute. In this article, fuzzy logic is proposed as a means of handling uncertainty in an expert system structure for automatic target recognition. A new technique for logical inference is described which is well-suited for this type of application. A prototype system has been developed and tested on multisensor and temporal images. the results are compared to a similar expert system which used a numeric uncertainty calculus.  相似文献   
83.
84.
Phospholamban (PLN) is an intrinsic membrane protein of 52 amino acids which regulates the Ca2+ pump of the sarcoplasmic reticulum of heart, slow-twitch and smooth muscle (SR): it is normally assumed to exist in the membrane as a homopentamer. A monomeric analogue of phospholamban PLN(C41F), in which Cys41 was replaced by a Phe, was synthesized and its conformation studied by 1H NMR spectroscopy in a 1:1 mixture of chloroform/methanol. Most of the resonances in the 1H NMR spectra were assigned. The work has shown that the C-terminal hydrophobic portion forms a very stable alpha-helix. The hydrophilic N-terminal part adopts an alpha-helix configuration which is much less stable except for the stretch containing the phosphorylation sites.  相似文献   
85.
86.
87.
The suitability of the semiconductor-device modeling program PC-1D for high-accuracy simulation of silicon photodiodes is discussed. A set of user interface programs optimized to support high-accuracy batch-mode operation of PC-1D for modeling the internal quantum efficiency of photodiodes is also described. The optimization includes correction for the dark current under reverse- and forward-bias conditions before calculating the quantum efficiency, and easy access to the highest numerical accuracy available from PC-1D, neither of which is conveniently available with PC-1D’s standard user interface.  相似文献   
88.
89.
Objectives: Examine the effectiveness of an intervention to increase fruits and vegetables (FV) consumption among smokers. Design: Cluster-randomized trial of 20 public housing developments; 10 randomly assigned to an FV intervention and 10 to a smoking cessation intervention. Main outcome measures: Usual (past 7 days) and past 30 days change in daily FV intake at 8 weeks and 6 months postbaseline. Results: Greater increases were seen in the FV group. At Week 8 and Month 6, the FV group had consumed 1.58 (p = .001) and 0.78 (p = .04), respectively, more daily FV servings in the past 7 days than the cessation group. At the same time points, the FV group had consumed 3.61 (p = .01) and 3.93 (p = .01), respectively, more FV servings in the past 30 days than the cessation group. Completing more motivational interviewing sessions (p = .02) and trying more recipes (p = .02) led to significantly greater increases at Month 6 among FV participants. Conclusions: Motivational interviewing counseling and lifestyle modification through trying out healthy recipes may be effective in helping a high-risk population increase their FV intake. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
90.
This study examined the relationship between alliance and retention in family therapy. Alliance was examined at the individual (parent and adolescent) and family levels (within-family differences). Participants were 34 families who received functional family therapy for the treatment of adolescent (aged 12-18 years) behavior problems. Families were classified as treatment dropouts (n=14) or completers (n=20). Videotapes of the first sessions were rated to identify parent and adolescent alliances with the therapist. Results demonstrated that individual parent and adolescent alliances did not predict retention. However, as hypothesized, dropout cases had significantly higher unbalanced alliances (parent minus adolescent) than did completer cases. These findings highlight the importance of alliances in functional family therapy and suggest that how the alliance operates in conjoint family therapy may be a function of systemic rather than of individual processes. (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