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   1553242篇
  免费   27312篇
  国内免费   7923篇
电工技术   35730篇
技术理论   5篇
综合类   7431篇
化学工业   275034篇
金属工艺   65587篇
机械仪表   44483篇
建筑科学   47805篇
矿业工程   11963篇
能源动力   50469篇
轻工业   119708篇
水利工程   15818篇
石油天然气   38542篇
武器工业   379篇
无线电   199035篇
一般工业技术   291629篇
冶金工业   178451篇
原子能技术   34150篇
自动化技术   172258篇
  2021年   16122篇
  2020年   12194篇
  2019年   14924篇
  2018年   16771篇
  2017年   16222篇
  2016年   22115篇
  2015年   18023篇
  2014年   29294篇
  2013年   88805篇
  2012年   37650篇
  2011年   51020篇
  2010年   44526篇
  2009年   52610篇
  2008年   47403篇
  2007年   45110篇
  2006年   46709篇
  2005年   41368篇
  2004年   42667篇
  2003年   42375篇
  2002年   41411篇
  2001年   38277篇
  2000年   36632篇
  1999年   35701篇
  1998年   49304篇
  1997年   41935篇
  1996年   37148篇
  1995年   31848篇
  1994年   29700篇
  1993年   29510篇
  1992年   26579篇
  1991年   23680篇
  1990年   23942篇
  1989年   23093篇
  1988年   21581篇
  1987年   19772篇
  1986年   19195篇
  1985年   22527篇
  1984年   22573篇
  1983年   20502篇
  1982年   19403篇
  1981年   19541篇
  1980年   18179篇
  1979年   18700篇
  1978年   17887篇
  1977年   17874篇
  1976年   19290篇
  1975年   16116篇
  1974年   15613篇
  1973年   15696篇
  1972年   13172篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
A study of the noise performance of gate overlapped polycrystalline silicon thin-film transistors (TFTs) is presented. Low-frequency noise measurements were carried out on n- and p-type samples fabricated by excimer laser crystallization. It is shown that the carrier number fluctuation model applies not only to n-type but also to p-type devices. The density of oxide traps was extracted from the noise measurements and was of the order of 1018-1019 eV-1 cm-3  相似文献   
992.
We prove that the entropy is a supermodular and subadditive function on the lattice of all n-dimensional probability distributions, ordered according to the partial order relation defined by majorization among vectors  相似文献   
993.
994.
Identification of Lophius budegassa(black‐bellied angler) and L. piscatorius(angler) (Lophiiformes) was carried out on the amplification of a 486 bp tRNAGlu/cytochrome b segment using the polymerase chain reaction (PCR). Direct DNA sequencing of 6 PCR products was carried out. Six restriction endonucleases (AluI, CfoI, HaeIII, HinfI, Mae, and ScrFI) with different species‐specific restriction fragment length polymorphism (RFLP) were selected. Digestions of PCR products from 30 individuals showed no intraspecific polymorphism. Double digestions (CfoI and HinfI, and HaeIII and ScrFI) were simpler and more rapid than single digestions. This technique is suitable for distinguishing tails of both Lophius species.  相似文献   
995.
Accuracy of approximations in MOSFET charge models   总被引:2,自引:0,他引:2  
This paper analyzes the results of common approximations made in MOSFET charge modeling. The basis for the comparison is a charge-sheet model that is valid in all regions of operation. We show that proper modeling of surface potential as a function of position along the channel is more important for capacitance coefficient modeling accuracy than partitioning of inversion charge between source and drain. In addition, we show that there is a numerical error in previous charge-sheet formulations, and provide a solution for this problem  相似文献   
996.
In this paper, a physics-based mismatch model is presented. It is demonstrated on a 0.18-/spl mu/m technology that a simple mismatch model can still be used to characterize deep-submicron technologies. The accuracy of the model is examined and found to be within 20% in the strong inversion region. Bulk bias dependence is modeled in a physical way. To extract the mismatch parameters, a weighted fit is introduced. It is shown that the width and length dependence of the mismatch parameters is given by the Pelgrom model.  相似文献   
997.
A PAC-Bayesian margin bound for linear classifiers   总被引:3,自引:0,他引:3  
We present a bound on the generalization error of linear classifiers in terms of a refined margin quantity on the training sample. The result is obtained in a probably approximately correct (PAC)-Bayesian framework and is based on geometrical arguments in the space of linear classifiers. The new bound constitutes an exponential improvement of the so far tightest margin bound, which was developed in the luckiness framework, and scales logarithmically in the inverse margin. Even in the case of less training examples than input dimensions sufficiently large margins lead to nontrivial bound values and-for maximum margins-to a vanishing complexity term. In contrast to previous results, however, the new bound does depend on the dimensionality of feature space. The analysis shows that the classical margin is too coarse a measure for the essential quantity that controls the generalization error: the fraction of hypothesis space consistent with the training sample. The practical relevance of the result lies in the fact that the well-known support vector machine is optimal with respect to the new bound only if the feature vectors in the training sample are all of the same length. As a consequence, we recommend to use support vector machines (SVMs) on normalized feature vectors only. Numerical simulations support this recommendation and demonstrate that the new error bound can be used for the purpose of model selection.  相似文献   
998.
The early history of the IEEE Microwave Theory and Techniques Society (IEEE MTT-S) is summarized since its founding in 1952, and all administrative committee members and presidents are listed. Some of the more recent changes resulting from growth and multinational participation are described. Publications are discussed with editors listed for this Transactions, the IEEE Microwave and Wireless Components Letters, the IEEE Microwave Newsletter, and IEEE Microwave Magazine. The chronological evolution of the IEEE MTT-S's awards is presented, including a listing of all award winners. Distinguished lecturers and microwave symposia sites and chairpersons are also discussed. Early technology trends are described  相似文献   
999.
1000.
There are many factors to consider in carrying out a hyperspectral data classification. Perhaps chief among them are class training sample size, dimensionality, and distribution separability. The intent of this study is to design a classification procedure that is robust and maximally effective, but which provides the analyst with significant assists, thus simplifying the analyst's task. The result is a quadratic mixture classifier based on Mixed-LOOC2 regularized discriminant analysis and nonparametric weighted feature extraction. This procedure has the advantage of providing improved classification accuracy compared to typical previous methods but requires minimal need to consider the factors mentioned above. Experimental results demonstrating these properties are presented.  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