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   16917篇
  免费   564篇
  国内免费   27篇
电工技术   209篇
综合类   14篇
化学工业   3584篇
金属工艺   323篇
机械仪表   360篇
建筑科学   703篇
矿业工程   98篇
能源动力   458篇
轻工业   1204篇
水利工程   194篇
石油天然气   120篇
无线电   1023篇
一般工业技术   2853篇
冶金工业   3476篇
原子能技术   147篇
自动化技术   2742篇
  2023年   96篇
  2022年   150篇
  2021年   257篇
  2020年   203篇
  2019年   209篇
  2018年   300篇
  2017年   278篇
  2016年   317篇
  2015年   300篇
  2014年   435篇
  2013年   1124篇
  2012年   718篇
  2011年   894篇
  2010年   655篇
  2009年   657篇
  2008年   804篇
  2007年   749篇
  2006年   689篇
  2005年   610篇
  2004年   544篇
  2003年   465篇
  2002年   471篇
  2001年   313篇
  2000年   278篇
  1999年   301篇
  1998年   346篇
  1997年   314篇
  1996年   294篇
  1995年   248篇
  1994年   270篇
  1993年   236篇
  1992年   242篇
  1991年   164篇
  1990年   211篇
  1989年   221篇
  1988年   173篇
  1987年   208篇
  1986年   179篇
  1985年   207篇
  1984年   218篇
  1983年   181篇
  1982年   177篇
  1981年   142篇
  1980年   134篇
  1979年   144篇
  1978年   119篇
  1977年   145篇
  1976年   126篇
  1975年   120篇
  1974年   109篇
排序方式: 共有10000条查询结果,搜索用时 663 毫秒
141.
142.
This study adopted a systemic approach to studying intervention efforts with delinquent youth, examining the association between several youth corrections programs and adult criminal outcomes. Two studies were designed to use juvenile and adult court records to evaluate the effectiveness of treatment programs provided to delinquent youth in state custody. The results of Study 1 suggested that court-recorded delinquent charges can be used to estimate delinquency severity. The results of Study 2 presented a discouraging but not entirely unexpected illustration of the effectiveness of intervention efforts among delinquent youth. It was found that time spent in juvenile detention facilities, work programs, and group homes was associated with negative adult criminal outcomes. No links between time spent in youth corrections programs and positive outcomes were identified. Implications for future program evaluation efforts are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
143.
目前的第一代无线局域网(WLAN)仅仅用来简单地取代有线,即只是用来消除主要家庭娱乐系统或办公设备部署采用过多线缆所引起的混乱.而实际上,无线通信的优势远远不止这一点.摆脱线缆的束缚之后,设备间可能的连接方式将大量增加.  相似文献   
144.
Elemental depth profiles of PZT films prepared by two sol–gel formulations, differing in the zirconium precursor stabilization, were investigated by SIMS analysis. Early decomposition of the zirconium precursor yielded opposing gradients of zirconium and titanium, while simultaneous late decomposition of zirconium and titanium precursors provided profile uniformity. The gradients formed during initial crystallization are irreversible. Both types of films showed excellent hysteresis; however, uniform films exhibited a much higher dielectric constant, indicating superior piezoelectric properties. Non-uniform films displayed a complex CV pattern, consistent with an inhomogeneous structure. Finally, thermal decomposition of the individual metal precursors is crucial for controlling film uniformity.  相似文献   
145.
146.
Mixed tocopherols (MT) containing a predominance of γ‐tocopherol were evaluated for antioxidant (AO) performance in polybutadiene‐ and polyisoprene‐based styrenic block copolymers (SBS and SIS, respectively) by using oxidative induction time as a measure of AO performance. A conventional hindered phenolic AO and α‐tocopherol (vitamin E) were evaluated in comparison. MT exhibited significantly higher performance than the controls in both SIS and SBS polymers. J. VINYL ADDIT. TECHNOL., 12:73–77, 2006. © 2006 Society of Plastics Engineers  相似文献   
147.
148.
The weighted essentially non-oscillatory (WENO) method is an excellent spatial discretization for hyperbolic partial differential equations with discontinuous solutions. However, the time-step restriction associated with explicit methods may pose severe limitations on their use in applications requiring large scale computations. An efficient implicit WENO method is necessary. In this paper, we propose a prototype flux-implicit WENO (iWENO) method. Numerical tests on classical scalar equations show that this is a viable and stable method, which requires appropriate time-stepping methods. Future study will include the examination of such methods as well as extension of iWENO to systems and higher dimensional problems.Sigal Gottlieb - The work of this author supported by NSF grant DMS-0106743.Steven J. Ruuth - The work of this author was partially supported by a grant from NSERC Canada.  相似文献   
149.
150.
Predicted that high self-esteem Ss (HSEs) would rationalize an esteem-threatening decision less than low self-esteem Ss (LSEs), because HSEs presumably had more favorable self-concepts with which to affirm, and thus repair, their overall sense of self-integrity. This prediction was supported in 2 experiments within the "free-choice" dissonance paradigm: one that manipulated self-esteem through personality feedback and the other that varied it through selection of HSEs and LSEs, but only when Ss were made to focus on their self-concepts. A 3rd experiment countered an alternative explanation of the results in terms of mood effects that may have accompanied the experimental manipulations. Results were discussed in terms of the following: (1) their support for a resources theory of individual differences in resilience to self-image threats—an extension of self-affirmation theory, (2) their implications for self-esteem functioning, and (3) their implications for the continuing debate over self-enhancement vs self-consistency motivation. (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