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   1057篇
  免费   15篇
  国内免费   6篇
电工技术   56篇
综合类   3篇
化学工业   197篇
金属工艺   34篇
机械仪表   24篇
建筑科学   24篇
能源动力   32篇
轻工业   48篇
水利工程   3篇
石油天然气   1篇
无线电   106篇
一般工业技术   136篇
冶金工业   274篇
原子能技术   59篇
自动化技术   81篇
  2022年   9篇
  2021年   19篇
  2020年   8篇
  2019年   5篇
  2018年   14篇
  2017年   10篇
  2016年   8篇
  2015年   6篇
  2014年   19篇
  2013年   32篇
  2012年   26篇
  2011年   41篇
  2010年   33篇
  2009年   46篇
  2008年   43篇
  2007年   29篇
  2006年   24篇
  2005年   29篇
  2004年   26篇
  2003年   26篇
  2002年   22篇
  2001年   28篇
  2000年   27篇
  1999年   28篇
  1998年   94篇
  1997年   62篇
  1996年   45篇
  1995年   45篇
  1994年   34篇
  1993年   26篇
  1992年   9篇
  1991年   10篇
  1990年   12篇
  1989年   12篇
  1988年   15篇
  1987年   16篇
  1986年   21篇
  1985年   10篇
  1984年   12篇
  1983年   9篇
  1982年   10篇
  1981年   15篇
  1980年   8篇
  1979年   10篇
  1978年   9篇
  1977年   4篇
  1976年   11篇
  1975年   6篇
  1973年   6篇
  1969年   4篇
排序方式: 共有1078条查询结果,搜索用时 0 毫秒
41.
SWAN – a Semantic Web Application in Neuromedicine – is a project to develop an effective, integrated scientific knowledge infrastructure for Alzheimer Disease (AD) researchers, enabled by Semantic Web technology and deployed on Alzforum (www.alzforum.org), a scientific web community for AD research. This infrastructure may later be deployed for research communities in other neuromedical disorders. SWAN incorporates the full biomedical research knowledge lifecycle in its ontological model, including support for personal data organization, hypothesis generation, experimentation, lab data organization, and digital pre-publication collaboration. Community, laboratory, and personal digital resources may all be organized and interconnected using SWAN's common semantic framework.  相似文献   
42.

This article investigates factors that influenced Japanese voters in the early 1996 in determining which political party to support. Proportional-odds model, a model which retains ordinal nature of political hues or ideologies of the Japanese political parties, is fitted to the data. Samples with answers “I do not know” to the questions are treated as missing. The EM algorithm enables us to incorporate the samples with missing-values. We found that determining which party to support is a purely political decision for Japanese voters based solely on their ideologies and attitude towards the current cabinet, not to be influenced by their geographical profiles nor financial situations. Missing-value problem were found not to be ignored in the sense that marginally significant or insignificant explanatory variables can easily turn otherwise when the same model is fitted only for the data with no missing-values.

  相似文献   
43.
The pyruvate dehydrogenase complex (PDC) plays a key role in the anaerobic mitochondrial metabolism of the parasitic nematode Ascaris suum. A cDNA coding for an A. suum pyruvate dehydrogenase kinase (APDK) has been cloned and sequenced from poly(A)+ RNA isolated from adult A. suum muscle.2 APDK exhibited significant sequence identity to mammalian PDKs. Nucleotide sequence analysis of the APDK cDNA revealed a 22-nucleotide spliced leader, characteristic of many nematode mRNAs, a 5'-UTR of 6 nucleotides, an open reading frame of 1197 nucleotides, and a 3'-UTR of 101 nucleotides that included a putative polyadenylation signal. The open reading frame predicted a protein of 399 amino acids with a molecular weight of 45,402 that included a putative 18-aminoacid leader peptide. Recombinant APDK (rAPDK) was functionally expressed in Escherichia coli with a his tag at its N-terminus and purified to apparent homogeneity on Ni-NTA-agarose. Recombinant APDK was a dimer and was not autophosphorylated and its activity was stimulated in the presence of APDK-deficient adult A. suum muscle PDC presumably by the binding of APDK to the dihydrolipoyl transacetylase (E2) core of the complex. After binding to the core, rAPDK activity was stimulated by elevated NADH/NAD+ and acetyl CoA/CoA ratios within the same ranges as observed for the native APDK. Immunoblotting suggested that native APDK focused as a series of 43-kDa spots (pI 6.1-6.8) on two-dimensional gels of the purified adult A. suum muscle PDC.  相似文献   
44.
45.
Velocity and propagation loss of surface shear waves are measured on free-space and metallised surfaces of LiNbO3 crystals along the x-axis of rotated Y-cut plates as a function of rotation about the x-axis between 35° and 70°. The coupling factor obtained from the velocities is 0.20 for a 35° rotated Y-cut plate and 0.09 for a 70° plate. The coupling factor changes linearly with the rotation angle. The propagation losses over the whole range measured here are less than 5 dB/cm on both free-space and on metallised surfaces. These losses are fairly low and very favourable for fabricating s.a.w. filters.  相似文献   
46.
47.
K. Kinoshita  J. Bett 《Carbon》1973,11(3):237-247
The electrochemical oxidation of a high surface area carbon black (1000 m2/g) was investigated in 96% H3PO4 at 135°C. The total anodic current, the amount of CO2 evolved and the oxygen content of the carbon were all measured as a function of time and potential. Two anodic processes occurred: the formation of a surface oxide and the evolution of CO2. Both decreased with time but at different rates so that CO2 evolution eventually became the major reaction. Various mechanisms to define the corrosion processes are discussed.  相似文献   
48.
Yanagita T  Ikeda I  Wang YM  Nakagiri H 《Lipids》2004,39(9):827-832
It has been reported that, compared with TAG, DAG suppresses postprandial hypertriacylglycerolemia and reduces visceral fat levels in experimental animals and humans. To clarify the mechanism responsible for these beneficial effects, we compared the lymphatic transport of 1,3-DAG, a major isomer of DAG, and TAG in rats. Male SD rats, after insertion of a cannula into the thoracic duct, were given 1,3-di[1-14C]oleoylglycerol or tri[1-14C]oleoylglycerol via a stomach tube. The 24-h receovery of the radioactivity from 1,3-di[14C]oleoylglycerol in the lymph was slightly but significantly lower than that from tri[14C]oleoylglycerol (81.3±1.0 vs. 86.5±1.2%, respectively). However, in the first 1-h interval after administration, the recovery of radioactivity from 1,3-dioleoylglycerol was almost half of that from trioleoylglycerol (17.5±2.0 vs. 31.1±1.4%). The amount of TAG and phospholipids secreted into the lymph was significantly lower 1 h after the administration of 1,3-dioleoylglycerol compared with that after the administration of trioleoylglycerol. More than 90% of the radioactivity recovered in the lymph in the first 3 h was distributed in the TAG fraction for both 1,3-dioleoylglycerol and trioleoylglycerol. These results suggest that slower lymphatic transport of 1,3-DAG compared with TAG could be a factor in the suppression of postprandial hypertriacylglycerolemia. The possibility that the slower lymphatic transport of DAG contributes to the antiobesity action observed in the feeding of 1,3-DAG cannot be excluded.  相似文献   
49.
A comprehensive econometric model was developed to evaluate potential impacts of recombinant bovine somatotropin (rbST) approval in Japan. Three novel features of the analyses include 1) investigation of impact of rbST on herd-size structure, 2) determination of economic feasibilities of rbST adoption by herd size, and 3) evaluation of policies to mitigate negative effects of rbST approval. Simulation analysis was conducted over a 10-yr projected period assuming rbST was approved in Japan in 2001. Nine hypothetical scenarios were simulated to examine sensitivity of simulation results. Simulation results indicate that rbST approval would accelerate structural change in Japan's dairy industry toward fewer, larger farms. Negative effects of rbST on farm income are projected to be more severe for smaller farms, because of higher costs, lower profit-earning ability, lower milk yields, and lower adoption rates of rbST. Larger farms benefit from rbST adoption if milk demand is maintained. However, if concerns about rbST induce significant milk demand decreases, even the largest farms' income and cow numbers will decrease. Thus, Japan's dairy industry could be caught in a double downward spiral of declining milk prices and production. Assuming rbST is approved, small farms would benefit by using the technology, but they fare best if rbST is not approved. Two policies could be effective in mitigating possible farm income losses. First, lost farm income can be offset if dairy cooperatives can exercise greater market power to control fluid milk marketings. Second, because generic milk advertising has positive effects on both milk demand and farm income, increasing check-off rates to fund more advertising could ease farm income losses.  相似文献   
50.
The probabilistic neural network (PNN) is one of the most promising neural networks, and is now applied to some real-world applications. In order to speed up the PNN calculation considerably, we have developed a PNN hardware system for video image recognition. The performance of the PNN hardware cannot be evaluated precisely until the evaluation system is completed. In this study, we developed a performance evaluation system for the PNN hardware and demonstrated it using the developed evaluation system.This work was presented, in part, at the 8th International Symposium on Artificial Life and Robotics, Oita, Japan, January 24–26, 2003  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