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   260761篇
  免费   4539篇
  国内免费   1820篇
电工技术   5412篇
技术理论   5篇
综合类   1164篇
化学工业   42099篇
金属工艺   11025篇
机械仪表   7791篇
建筑科学   6598篇
矿业工程   1660篇
能源动力   5598篇
轻工业   25818篇
水利工程   2891篇
石油天然气   5998篇
武器工业   243篇
无线电   27796篇
一般工业技术   49229篇
冶金工业   47233篇
原子能技术   5617篇
自动化技术   20943篇
  2021年   2496篇
  2019年   2145篇
  2018年   3403篇
  2017年   3369篇
  2016年   3699篇
  2015年   2803篇
  2014年   4597篇
  2013年   11369篇
  2012年   7697篇
  2011年   10203篇
  2010年   8120篇
  2009年   8670篇
  2008年   9476篇
  2007年   9590篇
  2006年   8433篇
  2005年   7385篇
  2004年   6661篇
  2003年   6203篇
  2002年   6212篇
  2001年   6319篇
  2000年   5909篇
  1999年   5879篇
  1998年   12860篇
  1997年   9536篇
  1996年   7280篇
  1995年   5527篇
  1994年   5085篇
  1993年   4949篇
  1992年   3945篇
  1991年   3752篇
  1990年   3823篇
  1989年   3771篇
  1988年   3531篇
  1987年   3019篇
  1986年   3050篇
  1985年   3408篇
  1984年   3321篇
  1983年   3074篇
  1982年   2698篇
  1981年   2903篇
  1980年   2643篇
  1979年   2839篇
  1978年   2736篇
  1977年   2842篇
  1976年   3695篇
  1975年   2458篇
  1974年   2290篇
  1973年   2320篇
  1972年   1981篇
  1971年   1785篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
162.
163.
164.
Several different lines of evidence have demonstrated that inherited susceptibility to rheumatoid arthritis (RA) is associated with the DRB1 genes encoding the HLA-DR4 and HLA-DR1 molecules. A contrasting hypothesis has recently been proposed, suggesting that, in general, the DRB1 locus is associated with protection to RA and that the RA-associated DRB1 alleles are not responsible for the primary disease association but merely permissive for the susceptibility conferred by the HLA-DQ alleles with which they are in linkage disequilibrium. We have performed a critical review of the literature on the HLA association in RA with special emphasis on studies in which both an HLA-DR and -DQ association has been investigated. Our analyses provide strong evidence against the hypothesis that HLA-DQ molecules play a major role in the general susceptibility to RA. Thus, the strongest association in rheumatoid arthritis is with DRB1 genes rather than DQB1 genes.  相似文献   
165.
166.
The physical widths of reference features incorporated into electrical linewidth test structures patterned in films of monocrystalline silicon have been determined from Kelvin voltage measurements. The films in which the test structures are patterned are electrically insulated from the bulk-silicon substrate by a layer of silicon dioxide provided by SIMOX (Separation by the IMplantation of OXygen) processing. The motivation is to facilitate the development of linewidth reference materials for critical-dimension (CD) metrology-instrument calibration. The selection of the (110) orientation of the starting silicon and the orientation of the structures' features relative to the crystal lattice enable a lattice-plane-selective etch to generate reference-feature properties of rectangular cross section and atomically planar sidewalls. These properties are highly desirable for CD applications in which feature widths are certified with nanometer-level uncertainty for use by a diverse range of CD instruments. End applications include the development and calibration of new generations of CD instruments directed at controlling processes for manufacturing devices having sub-quarter-micrometer features  相似文献   
167.
A new commercially available diode model is described. This unified model is capable of simulating the widest range of diode technologies of any presently available. The emphasis of this paper is on describing the model's extensive features and flexibility in the different domains of operation and is of particular interest in power applications  相似文献   
168.
A preliminary report presenting the results of fibular strut grafting in the severely resorbed mandibular and maxillary region is presented. Thirteen patients were treated due to severe resorption of alveolar and basilar bone of 49 segments of the mandible and the maxilla. Two patients additionally had pathological fractures of the mandible. In 10 cases the strut graft was harvested by means of a new minimally invasive technique. After modelling the fibular bone it was fixed to the recipient site by miniscrews or implants. After a mean follow-up period of 20 months (max. 31, min. 11 months) a retrospective analysis of clinical and radiological findings was carried out. It showed that a mean augmentation of 16 mm was achieved. Compared to other studies the fibular strut graft was resorbed less, and due to the primary stability it could be used for the treatment of fractures of the mandible. No more than natural resorption was observed when the patients received their prostheses fixed to dental implants.  相似文献   
169.
The biased percolation model is proposed for investigating device degradation and failure associated with the generation of defects due to local Joule heating. The degradation processes of a thin conducting or semiconducting film is monitored by a set of relevant indicators, such as: the evolution of damage pattern, the current distribution, the film resistance and its fluctuations, the defect concentration, the film lifetime, etc. The conductor-insulator (CI) and conductor-superconductor (CS) like degradation processes are considered. The results can be used to propose non-destructive indicators to test the reliability of samples and to interpret the corresponding experiments.  相似文献   
170.
Uses a Markov process to model a real-time expert system architecture characterized by message passing and event-driven scheduling. The model is applied to the performance evaluation of rule grouping for real-time expert systems running on this architecture. An optimizing algorithm based on Kernighan-Lin heuristic graph partitioning for the real-time architecture is developed and a demonstration system based on the model and algorithm has been developed and tested on a portion of the advanced GPS receiver (AGR) and manned manoeuvring unit (MMU) knowledge bases  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