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   1071篇
  免费   8篇
电工技术   14篇
化学工业   104篇
金属工艺   35篇
机械仪表   21篇
建筑科学   20篇
矿业工程   9篇
能源动力   20篇
轻工业   42篇
水利工程   12篇
石油天然气   3篇
无线电   74篇
一般工业技术   115篇
冶金工业   517篇
原子能技术   17篇
自动化技术   76篇
  2021年   10篇
  2020年   6篇
  2019年   6篇
  2018年   6篇
  2016年   8篇
  2014年   9篇
  2013年   30篇
  2012年   18篇
  2011年   24篇
  2010年   21篇
  2009年   20篇
  2008年   25篇
  2007年   28篇
  2006年   18篇
  2005年   31篇
  2004年   17篇
  2003年   9篇
  2002年   24篇
  2001年   20篇
  2000年   14篇
  1999年   18篇
  1998年   101篇
  1997年   67篇
  1996年   46篇
  1995年   38篇
  1994年   32篇
  1993年   32篇
  1992年   23篇
  1991年   11篇
  1990年   31篇
  1989年   29篇
  1988年   19篇
  1987年   22篇
  1986年   21篇
  1985年   24篇
  1984年   15篇
  1983年   14篇
  1982年   13篇
  1981年   12篇
  1980年   13篇
  1979年   8篇
  1978年   8篇
  1977年   15篇
  1976年   38篇
  1975年   10篇
  1974年   9篇
  1973年   8篇
  1972年   11篇
  1971年   5篇
  1970年   5篇
排序方式: 共有1079条查询结果,搜索用时 15 毫秒
1.
One promising strategy to combat antibiotic-resistant bacteria is to develop compounds that block bacterial defenses against antibacterial conditions produced by the innate immune system. Salmonella enterica, which causes food-borne gastroenteritis and typhoid fever, requires histidine kinases (HKs) to resist innate immune defenses such as cationic antimicrobial peptides (CAMPs). Herein, we report that 2-aminobenzothiazoles block histidine kinase-dependent phenotypes in Salmonella enterica serotype Typhimurium. We found that 2-aminobenzothiazoles inhibited growth under low Mg2+, a stressful condition that requires histidine kinase-mediated responses, and decreased expression of the virulence genes pagC and pagK. Furthermore, we discovered that 2-aminobenzothiazoles weaken Salmonella’s resistance to polymyxin B and polymyxin E, which are last-line antibiotics and models for host defense CAMPs. These findings raise the possibilities that 2-aminobenzothiazoles can block HK-mediated bacterial defenses and can be used in combination with polymyxins to treat infections caused by Salmonella.  相似文献   
2.
Earth Observation (EO) provides a promising approach towards deriving accurate spatiotemporal estimates of key parameters characterizing land surface interactions, such as latent (LE) and sensible (H) heat fluxes as well as soil moisture content. This paper proposes a very simple method to implement, yet reliable to calculate evapotranspiration fraction (EF) and surface moisture availability (Mo) from remotely sensed imagery of Normalized Difference Vegetation Index (NDVI) and surface radiometric temperature (Tir). The method is unique in that it derives all of its information solely from these two images. As such, it does not depend on knowing ancillary surface or atmospheric parameters, nor does it require the use of a land surface model. The procedure for computing spatiotemporal estimates of these important land surface parameters is outlined herein stepwise for practical application by the user. Moreover, as the newly developed scheme is not tied to any particular sensor, it can also be implemented with technologically advanced EO sensors launched recently or planned to be launched such as Landsat 8 and Sentinel 3. The latter offers a number of key advantages in terms of future implementation of the method and wider use for research and practical applications alike.  相似文献   
3.
4.
Hosted by the Distributed Management Task Force (DMTF) and collocated with the International Conference on Network and Service Management, SVM 2013 was the seventh International DMTF Academic Alliance Workshop on Systems and Virtualization Management (SVM). SVM 2013 was held in Zurich, Switzerland on October 18, 2013. Featuring seven presentations surrounding cloud, OpenSAF, open standards, and CIM, SVM 2013 also included a joint poster session with another workshop, an invited talk by a guest speaker, a keynote speech given by the DMTF President, Jeff Hilland, and closed with an informal interactive group discussion.  相似文献   
5.
6.
The response of a granular chain to impulse loading was investigated as a function of material properties. Using COMSOL Multiphysics, the elastic modulus and density of the grains were varied while the piston and force sensor properties remained fixed. The result of solitary wave propagation through the granular chain was recorded at the force sensor as a series of reaction force waves. It was found that wave velocity and amplitude increased with elastic modulus. Increasing density caused a decrease in wave velocity and an increase in amplitude. In addition, higher density granular chains exhibited a decrease in the number of waves in their respective reaction force wave trains. LS-DYNA was then used to explore the response of a variety of ceramic and metallic granular chains. Density, elastic modulus, and Poisson’s ratio were all set to representative values for the respective material. It was found that solitary wave development and decay occurred at different rates for different materials. In addition, the kinetic energy decay of the impactor was slower for glass compared with tungsten. Finally, it was shown that a single reaction force wave with no train could be produced by impacting a high density, high modulus chain such as tungsten with a glass piston, which has relatively low density and elastic modulus. Increasing impact velocity for this case resulted in a single high-amplitude wave with no train.  相似文献   
7.
8.
9.
Friction stir scribe technology, a derivative of friction stir welding, was applied for the dissimilar lap welding of an aluminium alloy and galvanised mild steel sheets. During the process, the rotating tool with a cobalt steel scribe first penetrated the top material – aluminium – and then the scribe cuts the bottom material – steel. The steel was displaced into the upper material to produce a characteristic hook feature. Lap welds were shear tested, and their fracture paths were studied. Welding parameters affected the welding features, including hook height, which turned out to be highly related to fracture position. Therefore, in this paper, the relationships among welding parameters, hook height, joint strength and fracture position are presented. In addition, the influence of zinc coating on joint strength was also studied.  相似文献   
10.
[Correction Notice: An erratum for this article was reported in Vol 30(4) of Health Psychology (see record 2011-13978-001). The letter was missing the doi. The correct doi is 10.1037/a0022737. The online version of this article has been corrected.] Responds to the comments by J. C. Coyne and C. Johansen (see record 2011-09497-016) on the current author's original article, "Influence of stressors on breast cancer incidence in the Women's Health Initiative" (see record 2009-03297-001). Coyne and Johansen (2011) took issue with the study conducted by the current authors' group (Michael et al., 2009), which analyzed the interaction between stressful life events and social support on breast cancer risk among 83,334 postmenopausal women enrolled in the Women’s Health Initiative (WHI). While the current authors agree with the Coyne and Johansen that too often null results are difficult to publish due to confirmatory bias that privileges results that support an alternative hypothesis, they strongly disagree with the assertion that their group selectively reported findings, inaccurately reported findings, or provided selective and uncritical reference to the existing literature. (PsycINFO Database Record (c) 2011 APA, all rights reserved)  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