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   17075篇
  免费   337篇
  国内免费   26篇
电工技术   205篇
综合类   3篇
化学工业   2434篇
金属工艺   403篇
机械仪表   365篇
建筑科学   606篇
矿业工程   64篇
能源动力   332篇
轻工业   1427篇
水利工程   107篇
石油天然气   121篇
无线电   1642篇
一般工业技术   2662篇
冶金工业   5121篇
原子能技术   182篇
自动化技术   1764篇
  2022年   104篇
  2021年   141篇
  2020年   106篇
  2019年   138篇
  2018年   200篇
  2017年   154篇
  2016年   150篇
  2015年   149篇
  2014年   277篇
  2013年   687篇
  2012年   401篇
  2011年   537篇
  2010年   438篇
  2009年   416篇
  2008年   556篇
  2007年   537篇
  2006年   498篇
  2005年   462篇
  2004年   395篇
  2003年   419篇
  2002年   362篇
  2001年   358篇
  2000年   345篇
  1999年   410篇
  1998年   1369篇
  1997年   869篇
  1996年   637篇
  1995年   448篇
  1994年   409篇
  1993年   428篇
  1992年   301篇
  1991年   262篇
  1990年   280篇
  1989年   238篇
  1988年   234篇
  1987年   220篇
  1986年   208篇
  1985年   266篇
  1984年   228篇
  1983年   221篇
  1982年   222篇
  1981年   193篇
  1980年   204篇
  1979年   150篇
  1978年   141篇
  1977年   242篇
  1976年   321篇
  1975年   141篇
  1974年   128篇
  1973年   110篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
GD Ruth  S Smith  M Bronson  AT Davis  RM Wilcox 《Canadian Metallurgical Quarterly》2003,24(5):318-21; discussion 317
Nationally, approximately 10% of child abuse cases involve burning, and up to 20% of pediatric burn admissions involve abuse or neglect. Historically, these cases have been more difficult to prosecute than nonburn cases for multiple reasons. Between 1995 and 1999, there were 285 pediatric (under 18) patients admitted to the Spectrum Health Regional Burn Center. Of these cases, 18 of the alleged perpetrators were legally investigated for suspicion of child abuse, and 7 received punitive sentences. We found that men tended to be prosecuted and convicted more often than women and that cases involving multiple instances of injury tended to be prosecuted more frequently. Similarly, we found that cases involving more severe injuries tended to be prosecuted more successfully. There are many psychological and social factors involved in handling burn abuse cases. However, by successful prosecution of these crimes, victims tend to fare better both socially and psychologically.  相似文献   
82.
The rationale for utilizing filial therapy as a treatment intervention with child witnesses of domestic violence while residing with their mothers in a shelter facility is explored and the effectiveness of an intensive 12-session filial therapy parent training group, conducted within 2-3 weeks, is described (n=11; aged 4-10 yrs). Results of analysis of covariance revealed that child witnesses in the experimental group significantly reduced behavior problems prevalent in child witnesses and significantly increased their self-concept as compared to child witnesses in the non-treatment comparison group. In addition, t-test results showed that mothers who facilitated treatment of the experimental group scored significantly higher after training on both their attitudes of acceptance and their empathic behavior. Comparative analysis revealed that intensive filial therapy as facilitated by the children's mothers was as effective in reducing behavior problems as was intensive individual play therapy and intensive sibling group play therapy as facilitated by professionally trained therapists. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
83.
R.A. McMahon  M.P. Smith  K.A. Seffen  W. Anwand 《Vacuum》2007,81(10):1301-1305
Flash-lamp annealing (FLA) on a millisecond time scale has been shown to be a promising tool in the preparation of high-quality semiconducting materials. The process imposes time varying through-thickness temperature profiles on the substrates being processed, and consequently thermal stresses. A combined thermal and optical model has been developed to predict the substrate temperature distribution and this model has been linked to a structural model to compute stresses and deflections. The paper shows how these models can be used to explore process conditions in flash lamp annealing, with particular regard to the annealing of ion implants in silicon and the crystallization of amorphous silicon layers on glass substrates.  相似文献   
84.
85.
Electrical resistance, thermal expansion, lattice constants of the intermediate valence materials, α-Ce and CeBe13, were measured at high pressure. It is found that the Grttneisen parameters of Kondo temperature TK are 13 and 42 for α-Ce and CeBe13, respectively, and it decreases with increasing pressure. The magnetoresistance of α-Ce shows H^2 dependence and its coefficient increases with pressure below 1 GPa, but becomes nearly constant above 1 GPa. The results indicate that the intermediate valence states are enhanced at high pressure indicating the enhancement of hybridization between the 4f electron and conduction band.  相似文献   
86.
For longitudinally uniform stretches of waterways there is a mixing center for the across-channel location of a steady point source in steady flow, such that complete mixing is achieved as soon as possible and there is no concentration overshoot at either of the two shorelines. A mathematical definition of the mixing center is the zero of the first oscillatory cross-channel diffusion mode. With the shorelines plus four interior data points across the channel, the starting estimate for the mixing center suffices to keep peak shoreline concentrations to within 6% of optimal. For comparison, a source at mid flow gives 18% shoreline concentration overshoot in the test case. Should very high precision be required, the Appendix gives an iterative construction that converges to the first oscillatory diffusion mode.  相似文献   
87.
High-performance p/sup +//n GaAs solar cells were grown and processed on compositionally graded Ge-Si/sub 1-x/Ge/sub x/-Si (SiGe) substrates. Total area efficiencies of 18.1% under the AM1.5-G spectrum were measured for 0.0444 cm/sup 2/ solar cells. This high efficiency is attributed to the very high open-circuit voltages (980 mV (AM0) and 973 mV (AM1.5-G)) that were achieved by the reduction in threading dislocation density enabled by the SiGe buffers, and thus reduced carrier recombination losses. This is the highest independently confirmed efficiency and open-circuit voltage for a GaAs solar cell grown on a Si-based substrate to date. Larger area solar cells were also studied in order to examine the impact of device area on GaAs-on-SiGe solar cell performance; we found that an increase in device area from 0.36 to 4.0 cm/sup 2/ did not degrade the measured performance characteristics for cells processed on identical substrates. Moreover, the device performance uniformity for large area heteroepitaxial cells is consistent with that of homoepitaxial cells; thus, device growth and processing on SiGe substrates did not introduce added performance variations. These results demonstrate that using SiGe interlayers to produce "virtual" Ge substrates may provide a robust method for scaleable integration of high performance III-V photovoltaics devices with large area Si wafers.  相似文献   
88.
89.
PURPOSE: To use a controlled, randomized design to assess the effect on patient satisfaction of an intensive psychosocial training program for residents. METHOD: Twenty-six first-year residents, in two internal medicine and family practice community-based programs affiliated with the Michigan State University College of Human Medicine, were randomly assigned during 1991 and 1992 to a control group or a one-month intensive training program. Experiential teaching focused on many psychosocial skills required in primary care. A 29-item questionnaire administered before and after the residents' training evaluated their patients' satisfaction regarding patient disclosure, physician empathy, confidence in physician, general satisfaction, and comparison of the physician with other physicians. Analyses of covariance with groups and gender as factors and pre-training patient satisfaction scores as the covariate evaluated the effect of the training. RESULTS: The patients of the trained residents expressed more confidence in their physicians (p = .01) and more general satisfaction (p = .02) than did the patients of controls. The effect of training on patient satisfaction with patient disclosure (p < .01) and physician empathy (p < .05) was greater for female than for male residents. CONCLUSION: The intensive psychosocial training program for residents improved their patients' satisfaction.  相似文献   
90.
Don C. Smith 《Refocus》2003,4(6):62-63
In addition to having one of the top environmental law programs in the United States, the University of Denver College of Law now has a building that demonstrates the institution ‘practices what it preaches’ when it comes to concern for the environment. Built on the front range of the Colorado Rocky Mountains, the 181,000 square foot, $63 million facility which opened in August will be the first certified “green” law school in the country. Don C. Smith, U.S. Correspondent explains the attributes that distinguish the building from conventional ones.  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