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   375篇
  免费   12篇
电工技术   5篇
化学工业   44篇
金属工艺   7篇
机械仪表   5篇
建筑科学   19篇
矿业工程   1篇
能源动力   12篇
轻工业   31篇
水利工程   2篇
石油天然气   1篇
无线电   22篇
一般工业技术   52篇
冶金工业   120篇
原子能技术   2篇
自动化技术   64篇
  2020年   6篇
  2017年   5篇
  2016年   9篇
  2015年   5篇
  2014年   5篇
  2013年   21篇
  2012年   9篇
  2011年   16篇
  2010年   13篇
  2009年   10篇
  2008年   10篇
  2007年   13篇
  2006年   8篇
  2005年   9篇
  2004年   11篇
  2003年   6篇
  2002年   15篇
  2001年   3篇
  2000年   4篇
  1999年   8篇
  1998年   12篇
  1997年   8篇
  1996年   4篇
  1995年   7篇
  1994年   9篇
  1993年   7篇
  1992年   5篇
  1991年   5篇
  1990年   3篇
  1989年   9篇
  1988年   3篇
  1987年   3篇
  1986年   6篇
  1985年   5篇
  1984年   6篇
  1983年   7篇
  1982年   5篇
  1981年   8篇
  1980年   4篇
  1979年   5篇
  1978年   6篇
  1977年   6篇
  1976年   6篇
  1975年   8篇
  1974年   3篇
  1971年   4篇
  1969年   3篇
  1967年   3篇
  1963年   3篇
  1960年   3篇
排序方式: 共有387条查询结果,搜索用时 31 毫秒
1.
We have isolated a mutant which exhibits partial constitutivity for a -specific gene expression in α cells. The wild-type gene was cloned and demonstrated to be allelic to the STE13 gene, which encodes the dipeptidyl aminopeptidase involved in processing of the α-factor prepropheromone. Thus, the mating defect of the ste13 mutations in α cells may result both from the production of incompletely processed α-factor and from the increased expression of a -specific genes. The STE13 open reading frame of 931 amino acids contains a putative membrane-spanning segment near its amino terminus and is 31% identical to a second yeast dipeptidyl aminopeptidase (DAP2). A null mutant of STE13 has been constructed: it is viable and sporulation-proficient. The sequence has been deposited in the GenBank data library under Accession Number L21944.  相似文献   
2.
3.
The synthetic growth promoter diethylstilboestrol (DES) administered orally to pigs can be detected by radioimmunoassay (RIA) analysis of kidney, liver, faeces, bile and urine from animals fed continuously to slaughter, but not in muscle, fat or plasma. If treated animals are fed on material not containing DES for 72 h prior to slaughter, then the levels of parent compound and metabolite in all products decrease to become not significantly greater than those in control animals. The gross metabolism of DES in pigs and bovines appears to be similar.  相似文献   
4.
A study of item bias in standard cognitive screening measures was conducted in a sample of Afro-American, Hispanic and non-Hispanic white elderly respondents who were part of a dementia case registry study. The methods of item-response theory were applied to identify biased items. Both cross-cultural and high and low education groups were examined to determine which items were biased. Out of 50 cognitive items examined from six widely used cognitive screening measures, 16 were identified as biased for either high and low education groups or ethnic/racial group membership.  相似文献   
5.
13C n.m.r. spectroscopy has been applied to investigate a number of coal tar and petroleum-derived carbon black feedstocks. Application of the J-modulated spin echo technique is especially rewarding, as this method renders the quaternary carbons directly detectable. Thus the quality of carbon black feedstocks can additionally be gauged on the basis of the contents of quaternary carbons, which is a direct indication of the carbon yield in the carbon black production process.  相似文献   
6.
The evaluation of unsupervised outlier detection algorithms is a constant challenge in data mining research. Little is known regarding the strengths and weaknesses of different standard outlier detection models, and the impact of parameter choices for these algorithms. The scarcity of appropriate benchmark datasets with ground truth annotation is a significant impediment to the evaluation of outlier methods. Even when labeled datasets are available, their suitability for the outlier detection task is typically unknown. Furthermore, the biases of commonly-used evaluation measures are not fully understood. It is thus difficult to ascertain the extent to which newly-proposed outlier detection methods improve over established methods. In this paper, we perform an extensive experimental study on the performance of a representative set of standard k nearest neighborhood-based methods for unsupervised outlier detection, across a wide variety of datasets prepared for this purpose. Based on the overall performance of the outlier detection methods, we provide a characterization of the datasets themselves, and discuss their suitability as outlier detection benchmark sets. We also examine the most commonly-used measures for comparing the performance of different methods, and suggest adaptations that are more suitable for the evaluation of outlier detection results.  相似文献   
7.
The importance of securing data against the threat of natural disasters i s something most MIS managers don't realize until it's too late. This column describes how two fires and an earthquake adversely affected several companies that were unprepared, or only partially prepared, for such disasters. It also discusses disaster recovery measures some MIS executives believe their companies should strengthen not only to protect the data center but to reduce their employees risk of losing valuable informa- tion from office files.  相似文献   
8.
9.
10.
The Quantum Finite-Difference Time-Domain (FDTD-Q) method is a numerical method for solving the time evolution of the Schrödinger equation. It can be applied to systems of interacting particles, allowing for realistic simulations of quantum mechanics of various experimental systems. One of the drawbacks of the method is that divergences in the numerical evolution occur rather easily in the presence of interactions, which necessitates a large number of evolution steps or imaginary time evolution. We present a generalized (GFDTD-Q) method for solving the time-dependent Schrödinger equation including interactions between the particles. The new scheme provides a more relaxed condition for stability when the finite difference approximations for spatial derivatives are employed, as compared with the original FDTD-Q scheme. We demonstrate our scheme by simulating the time evolution of a two-particle interaction Hamiltonian. Our results show that the generalized method allows for stable time evolutions, in contrast to the original FDTD-Q scheme which produces a divergent solution.  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