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   408篇
  免费   14篇
电工技术   18篇
化学工业   125篇
金属工艺   15篇
机械仪表   17篇
建筑科学   16篇
矿业工程   1篇
能源动力   10篇
轻工业   57篇
水利工程   2篇
无线电   15篇
一般工业技术   65篇
冶金工业   13篇
原子能技术   28篇
自动化技术   40篇
  2024年   2篇
  2023年   2篇
  2022年   8篇
  2021年   10篇
  2020年   4篇
  2019年   15篇
  2018年   13篇
  2017年   15篇
  2016年   11篇
  2015年   5篇
  2014年   13篇
  2013年   35篇
  2012年   23篇
  2011年   36篇
  2010年   21篇
  2009年   23篇
  2008年   29篇
  2007年   23篇
  2006年   22篇
  2005年   13篇
  2004年   10篇
  2003年   12篇
  2002年   8篇
  2001年   5篇
  2000年   7篇
  1999年   7篇
  1998年   7篇
  1997年   3篇
  1996年   4篇
  1995年   1篇
  1994年   2篇
  1993年   7篇
  1992年   2篇
  1991年   2篇
  1990年   1篇
  1989年   1篇
  1988年   1篇
  1987年   2篇
  1986年   4篇
  1985年   2篇
  1983年   2篇
  1982年   2篇
  1979年   1篇
  1978年   3篇
  1977年   1篇
  1976年   1篇
  1974年   1篇
排序方式: 共有422条查询结果,搜索用时 15 毫秒
101.
Phase diagram calculations that were made previously for the ZrO2-MO m/2 (m = 2, 3, 4) systems and for the ZrO2-YO1.5-MO m/2 (M = transition metals) systems have been extended to the ZrO2-YO1.5-CeO2(-CeO1.5) system to make an attempt to explain (1) thermogravimetric (TG) results as a function of oxygen potential, (2) electronic conductivity as a function of oxygen potential, and (3) a miscibility gap observed in air. The interaction parameters for the CeO2-CeO1.5-YO1.5 system were obtained from the reported oxygen nonstoichiometry in CeO2−x and rate earth doped ceria, (Ce,RE)O2−δ . The interaction parameters for the ZrO2-CeO2 subsystem were obtained so as to reproduce the observed miscibility gap at 1273 K. Those thermodynamic properties can reproduce consistently the experimental behaviors of the electronic conductivity and the TG results in the (Zr1−x Ce x )0.8Y0.2O1.9 solid solutions; these indicate the enhancement of reduction of CeO2.  相似文献   
102.
103.
104.
There is a close relationship between diabetes mellitus and heart failure, and diabetes is an independent risk factor for heart failure. Diabetes and heart failure are linked by not only the complication of ischemic heart disease, but also by metabolic disorders such as glucose toxicity and lipotoxicity based on insulin resistance. Cardiac dysfunction in the absence of coronary artery disease, hypertension, and valvular disease is called diabetic cardiomyopathy. Diabetes-induced hyperglycemia and hyperinsulinemia lead to capillary damage, myocardial fibrosis, and myocardial hypertrophy with mitochondrial dysfunction. Lipotoxicity with extensive fat deposits or lipid droplets is observed on cardiomyocytes. Furthermore, increased oxidative stress and inflammation cause cardiac fibrosis and hypertrophy. Treatment with a sodium glucose cotransporter 2 (SGLT2) inhibitor is currently one of the most effective treatments for heart failure associated with diabetes. However, an effective treatment for lipotoxicity of the myocardium has not yet been established, and the establishment of an effective treatment is needed in the future. This review provides an overview of heart failure in diabetic patients for the clinical practice of clinicians.  相似文献   
105.
The plant Tanacetum coccineum (painted daisy) is closely related to Tanacetum cinerariifolium (pyrethrum daisy). However, T. cinerariifolium produces large amounts of pyrethrins, a class of natural insecticides, whereas T. coccineum produces much smaller amounts of these compounds. Thus, comparative genomic analysis is expected to contribute a great deal to investigating the differences in biological defense systems, including pyrethrin biosynthesis. Here, we elucidated the 9.4 Gb draft genome of T. coccineum, consisting of 2,836,647 scaffolds and 103,680 genes. Comparative analyses of the draft genome of T. coccineum and that of T. cinerariifolium, generated in our previous study, revealed distinct features of T. coccineum genes. While the T. coccineum genome contains more numerous ribosome-inactivating protein (RIP)-encoding genes, the number of higher-toxicity type-II RIP-encoding genes is larger in T. cinerariifolium. Furthermore, the number of histidine kinases encoded by the T. coccineum genome is smaller than that of T. cinerariifolium, suggesting a biological correlation with pyrethrin biosynthesis. Moreover, the flanking regions of pyrethrin biosynthesis-related genes are also distinct between these two plants. These results provide clues to the elucidation of species-specific biodefense systems, including the regulatory mechanisms underlying pyrethrin production.  相似文献   
106.
Propagation of weak pressure waves against two parallel subsonic streams   总被引:2,自引:0,他引:2  
In this paper, the characteristics of a pressure wave propagating against two parallel subsonic streams in a constant-area straight duct are investigated by one-dimensional analysis, two-dimensional numerical simulation, and experiments. Computations have been carried out by the two-dimensional Euler Equations using the Chakravarthy-Osher-type TVD scheme. Optical observations by the schlieren method as well as wall pressure measurements have been performed to clarify both the structure and the propagation velocity of pressure waves. The results show that the pressure wave propagating against the streams changes into a bifurcated pressure wave and the bifurcation occurs in the low speed streams. It is also found that the propagation velocity of the pressure wave obtained by the analysis and computation agrees well with the present experimental data.  相似文献   
107.
Callosobruchus analis (Coleoptera: Chrysomelidae: Bruchinae), found throughout tropical Asia and Africa, is a pest of stored legumes. Previous work has shown that females of this species produce a contact sex pheromone that elicits copulatory behavior in males. Comparisons of copulatory activity between any two of four congeneric species suggest that the contact sex pheromones are species specific. In laboratory bioassays, male C. analis exhibited copulatory behavior to a female dummy to which a crude extract of virgin females was applied. The extract had been collected by a filter paper method and was purified by acid–base partition and chromatographic techniques. Gas chromatography-mass spectrometry (GC-MS) analyses of active fractions revealed that the active compounds were 2,6-dimethyloctane-1,8-dioic acid (1) and callosobruchusic acid, (E)-3,7-dimethyl-2-octene-1,8-dioic acid (2), previously identified as contact sex pheromones of Callosobruchus maculatus (F.) and C. chinensis (L.), respectively. The stereoisomeric and chemical compositions were determined by the 2D-HPLC-Ohrui-Akasaka method as (2S,6R)-1:(S)-2 = 1.8:1, which meant that both compounds in C. analis were stereochemically pure, unlike the case of C. maculatus and C. chinensis. An examination of the influence of synthetic pheromone compounds on male copulatory activity revealed that (2S,6R)-1 is the main component, and that (S)-2 has an additive effect. In the examination of the stereochemistry-activity relationship, no copulatory behavior was elicited by (2R,6S)-1, and, furthermore, the enantiomer significantly masked the pheromonal activity of (2S,6R)-1. Glass rod dummy assays also suggested the presence of synergists. These results could elucidate the specificity of mate recognition in C. analis.  相似文献   
108.
Assembly errors can occur in a robotic assembly system. In this paper, a method that predicts an assembly error is proposed. It considers that assembly errors occur under the condition that the geometric trajectory of a mated part and the relational position and orientation of a base part are outside the allowable tolerance. A certain point, which is determined by using a physical light reflectance model of a mated part, is followed with two high-speed cameras. A statistical pattern recognition method in which explanatory variables are tracked points in a three-dimensional space is then employed to predict an assembly error. The proposed method is applied to a peg-in-a-hole assembly by a selective compliance assembly robot arm (SCARA)-type robot and its potential value is discussed.  相似文献   
109.
对位于黄泛平原的山东省鄄城县糖牛楼村能源资源量与消费现状进行了调查,分析了该村能源的构成和消费特征,并进行了节能和开发新能源的实验,提高了生物质能利用率。  相似文献   
110.
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