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   1655篇
  免费   38篇
  国内免费   2篇
电工技术   114篇
化学工业   310篇
金属工艺   23篇
机械仪表   23篇
建筑科学   11篇
能源动力   73篇
轻工业   148篇
水利工程   1篇
无线电   163篇
一般工业技术   312篇
冶金工业   373篇
原子能技术   39篇
自动化技术   105篇
  2023年   7篇
  2022年   11篇
  2021年   16篇
  2020年   10篇
  2019年   21篇
  2018年   12篇
  2017年   19篇
  2016年   30篇
  2015年   14篇
  2014年   28篇
  2013年   63篇
  2012年   60篇
  2011年   69篇
  2010年   54篇
  2009年   50篇
  2008年   62篇
  2007年   62篇
  2006年   54篇
  2005年   42篇
  2004年   41篇
  2003年   52篇
  2002年   44篇
  2001年   44篇
  2000年   33篇
  1999年   29篇
  1998年   144篇
  1997年   80篇
  1996年   76篇
  1995年   49篇
  1994年   49篇
  1993年   50篇
  1992年   29篇
  1991年   28篇
  1990年   24篇
  1989年   18篇
  1988年   22篇
  1987年   15篇
  1986年   23篇
  1985年   24篇
  1984年   16篇
  1983年   17篇
  1982年   16篇
  1981年   15篇
  1980年   8篇
  1979年   5篇
  1978年   12篇
  1977年   16篇
  1976年   16篇
  1974年   5篇
  1972年   3篇
排序方式: 共有1695条查询结果,搜索用时 31 毫秒
1.
Hexokinases catalyze glucose phosphorylation at the first step in glycolysis in eukaryotes. In the budding yeast Saccharomyces cerevisiae , three enzymes for glucose phosphorylation have long been known: Hxk1, Hxk2, and Glk1. In this study, we focus on Emi2, a previously uncharacterized hexokinase-like protein of S. cerevisiae . Our data show that the recombinant Emi2 protein (rEmi2), expressed in Escherichia coli , possesses glucose-phosphorylating activity in the presence of ATP and Mg 2+ . It was also found that rEmi2 phosphorylates not only glucose but also fructose, mannose and glucosamine in vitro . In addition, we examined changes in the level of endogenous Emi2 protein in S. cerevisiae in the presence or absence of glucose and a non-fermentable carbon source. We found that the expression of Emi2 protein is tightly suppressed during proliferation in high glucose, while it is strongly upregulated in response to glucose limitation and the presence of a non-fermentable carbon source. Our data suggest that the expression of the endogenous Emi2 protein in S. cerevisiae is regulated under the control of Hxk2 in response to glucose availability in the environment.  相似文献   
2.
Abstract— We studied the influence of annealing in air on doped europium in BaMgAl10O17 by performing x‐ray absorption fine‐structure measurements. We determined the oxidation of doped divalent europium by annealing in air at over 500°C. The interatomic distance between the europium and the surrounding oxygen atoms was compressed by oxidation. It also appears that the oxidation process of europium is determined by the diffusion of oxygen into BaMgAl10O17.  相似文献   
3.
4.
Lanthanide-based oxysulfides and sulfide, LnTaO3.5S0.5, Ln10OS14 (Ln = La, Pr, Nd, Sm) and La4In5S13, were successively synthesized by sulfurization in a flowing H2S. The sulfurization decreased the band-gap energies from >4 eV to <3eV, because of the formation of occupied S3p orbitals on the top of valence band. In accordance with the small band gap, the H2 evolution from a 0.01 M Na2S and 0.01 M Na2SO3 solution system was observed under irradiation of light up to >500 nm. The rate of H2 evolution under light irradiation of >500 nm increased in the order of Ni/LaTaO3.5S0.5 < Ru/La10OS14 < Pt/La4In5S13.  相似文献   
5.
A 16 Mb embedded DRAM macro in a fully CMOS logic compatible 90 nm process with a low noise core architecture and a high-accuracy post-fabrication tuning scheme has been developed. Based on the proposed techniques, 61% improvement of the sensing accuracy is realized. Even with the smallest 5 fF/cell capacitance, a 322 MHz random-cycle access while 32 ms data retention time which contributes to save the data retention power down to 60 /spl mu/W are achieved.  相似文献   
6.
Automated camerawork for capturing desktop presentations   总被引:1,自引:0,他引:1  
A novel automated camera control method for capturing desktop presentations is introduced. Typical features and the camerawork of shots that appear frequently in TV programs are discussed. To realise those features in this automated video capturing system, the purpose of camerawork is classified from two points of view: target and aspect-of-target. Then, the correspondence between the classification and typical shots and camerawork is considered. A virtual-frame control algorithm based on this idea is proposed, and its implementation in a video production system. Results are shown that verify this method through two kinds of experiments, virtual video capturing using CG animations and real video capturing of real presentations.  相似文献   
7.
8.
This paper analyzes a multi-product production / inventory system where demands for each item arrive according to a Poisson process and the production time for each product has an Erlang distribution. The paper proposes an optimality condition that specifies whether each product should be produced make-to-stock or make-to-order. In the event a product should be produced make-to-stock, an approach for computing the optimal base-stock level is proposed. Numerical examples are given for illustrative purpose.  相似文献   
9.
Speed estimation methods for sensorless induction motor drives can be divided into two groups. One is based on information about fundamental components of stator currents and voltages. The other is based on high-frequency components injection in stator voltages or currents. The latter may operate stably under zero frequency, which occurs in regenerating mode at low speeds. It, however, causes loss increasing and torque ripple. The former is difficult to operate under zero frequency. The authors propose a stable method categorized in the former group even in regenerating mode at low speeds. The proposed method is based on an adaptive flux observer. First, a new observer gain design is shown. Next, a method avoiding zero-frequency operation with controlling a rotor flux level is proposed.  相似文献   
10.
The virtual path concept has several valuable features to construct an economical and efficient asynchronous transfer mode (ATM) network. One of them is bandwidth control which affords transmission efficiency improvement through statistical sharing of capacity. An effective bandwidth control algorithm and its calculated performance are described. Network performance with the algorithm is evaluated, and the bandwidth control is shown to successfully improve network transmission efficiency with only a slight increase in processing load compared to the fixed bandwidth scheme. A method is also proposed to equalize call loss probability for each virtual path. The effectiveness of the method is demonstrated by analysis  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