首页 | 官方网站   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   410篇
  免费   4篇
工业技术   414篇
  2013年   5篇
  2012年   4篇
  2011年   5篇
  2010年   4篇
  2009年   4篇
  2008年   10篇
  2007年   8篇
  2006年   11篇
  2005年   6篇
  2004年   9篇
  2003年   8篇
  2002年   6篇
  2001年   5篇
  1999年   4篇
  1998年   37篇
  1997年   25篇
  1996年   13篇
  1995年   20篇
  1994年   13篇
  1993年   9篇
  1991年   3篇
  1990年   7篇
  1989年   10篇
  1988年   9篇
  1987年   8篇
  1986年   7篇
  1985年   7篇
  1984年   4篇
  1983年   7篇
  1982年   4篇
  1981年   7篇
  1980年   3篇
  1979年   6篇
  1978年   5篇
  1977年   13篇
  1976年   10篇
  1975年   6篇
  1974年   9篇
  1973年   8篇
  1972年   4篇
  1971年   5篇
  1970年   3篇
  1969年   3篇
  1968年   5篇
  1967年   4篇
  1963年   4篇
  1961年   4篇
  1958年   3篇
  1957年   3篇
  1956年   4篇
排序方式: 共有414条查询结果,搜索用时 109 毫秒
1.
112 children (aged 7-13 yrs) were randomly assigned to one of three treatments: problem-solving skills training (PSST), problem-solving skills training with in vivo practice (PSST-P), which included therapeutically planned activities to extend training to settings outside of treatment, or client-centered relationship therapy (RT). PSST and PSST-P children showed significantly greater reductions in antisocial behavior and overall behavior problems, and greater increases in prosocial behavior than RT children. These effects were evident on measures obtained immediately after treatment and at a 1-year follow-up, and on measures of child performance at home and at school. PSST-P children showed greater changes than PSST children on measures of functioning at school at posttreatment, but these differences were no longer evident at follow-up. Children in both PSST conditions showed significant reductions in deviant behavior and improvements in prosocial behavior from pretreatment to follow-up, whereas RT children tended to remain at their pretreatment level of functioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
2.
This paper develops a method for simultaneously designing the power stage and controller for a switching power supply. The method utilizes a numerical optimization procedure, which facilitates computer-aided design. It is found that better performance can be achieved than with a traditional two-step design process, where the power stage and controller are designed sequentially. Optimization and simulation results for a buck power converter are presented to illustrate the design process and benefits  相似文献   
3.
4.
A rate-equation-based model that describes the behavior of a passively Q-switched solid-state laser containing an intracavity optical parametric oscillator (OPO) is developed. In such a laser there is no output at the fundamental or pump wavelength. When the OPO signal field begins to build up, it acts as a loss for the pump and thus cavity dumps the pump resonator. The model developed explains this behavior and enables one to select OPO parameters which optimize the system's performance. Application of the model to a compact, lightweight, eye-safe, laser range finder operating at 1.54 μm is also described  相似文献   
5.
6.
7.
Properties of diode laser pumps for high-power solid-state lasers   总被引:1,自引:0,他引:1  
Diode lasers used to pump high average power solid-state lasers typically have broad spectral width so that most of the pump light is not at the peak of the gain medium's absorption feature. However, the long absorption length in these lasers enables even weakly absorbed light to pump efficiently. The result is that high absorption efficiency and improved pump distribution uniformity are possible when using realistic pump diodes. In addition, both quantities are nearly independent of the pump center wavelength.  相似文献   
8.
We report the implementation of a new, high brightness, high efficiency white-light source based on up-conversion phosphors. Up-conversion materials absorb near infrared light and re-emit in red, green, and blue. It is possible to combine these colors to create a white-light source. Such a source has the same appealing characteristics as those reported for up-conversion displays: very high brightness operation without damage to the emitters, long lifetimes, and efficiencies comparable to those of existing technologies. In addition, they offer simplicity of fabrication and a variety of operating modes. Here we demonstrate a 7-lm/W D65 white light emitter yielding 2 kcd/m/sup 2/ on a simple diffuser.  相似文献   
9.
The extensive use of the Unified Parkinson's Disease Rating Scale (UPDRS) has revealed low interrater reliability in some items and redundancy in others. In view of these shortcomings, we have structured a new scale that includes a zero-to three-point scale for each item in the evaluation of PD. The mental axis includes memory, thought disorders, and depression. Activities of daily living (ADL) includes eight items: speech, eating, feeding, dressing, hygiene, handwriting, walking, and turning in bed. The motor examination includes eight items: speech, tremor, rest and posture, rigidity, finger tapping, arising from chair, gait, and postural stability. Complications of therapy were also included: dyskinesias, dystonia, motor fluctuations, and freezing episodes, collected by history. In addition, a global scoring for motor fluctuations that should complement the Hoehn and Yahr Scale was incorporated. In this report, we present a statistical analysis of the ADL, motor evaluation, and complications of therapy sections. Concerning the interrater reliability mean, Kendall's W values were >0.9 for most of the items in the Short Parkinson's Evaluation Scale (SPES). Kendall's W <0.8 (motor evaluation) was found for two items of the SPES and nine items of the UPDRS. The mean interrater reliability for both scales across all seven centers (seven Kendall's W for seven centers) (Mann-Whitney test) showed no statistical differences between the scales. Spearman's correlations between items of both scales were significant. Factor analysis of the SPES and UPDRS data revealed a four-factor solution that explained approximately 60% of the data. All participating centers found the SPES easier to apply and quicker to complete, when compared with the UPDRS. The results obtained strongly favor the introduction of SPES for clinical practice.  相似文献   
10.
Abstract— Several rare‐earth‐doped fluoride crystals that are excited to emit visible light by sequential two‐photon absorption have been investigated as display‐medium candidates for static volumetric three‐dimensional displays. Dispersion of powders of these materials in a refractive‐index‐matched polymer is reported because such a medium may result in a scalable display. The scattering problem in such a medium is greatly reduced by index‐matching the polymer to the crystalline particles. An index‐matching condition that optimizes the performance is identified.  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-23

京公网安备 11010802026262号