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   237篇
  免费   3篇
电工技术   8篇
化学工业   37篇
金属工艺   2篇
建筑科学   3篇
能源动力   5篇
轻工业   11篇
水利工程   1篇
石油天然气   1篇
无线电   18篇
一般工业技术   37篇
冶金工业   85篇
原子能技术   3篇
自动化技术   29篇
  2022年   2篇
  2021年   4篇
  2019年   3篇
  2018年   6篇
  2016年   2篇
  2014年   3篇
  2013年   10篇
  2012年   12篇
  2011年   6篇
  2010年   8篇
  2009年   9篇
  2008年   6篇
  2007年   8篇
  2006年   8篇
  2005年   8篇
  2004年   4篇
  2003年   4篇
  2002年   4篇
  2001年   5篇
  2000年   4篇
  1999年   3篇
  1998年   6篇
  1996年   3篇
  1995年   3篇
  1994年   6篇
  1993年   4篇
  1992年   4篇
  1990年   3篇
  1987年   6篇
  1986年   5篇
  1985年   2篇
  1984年   3篇
  1983年   6篇
  1982年   11篇
  1980年   3篇
  1979年   6篇
  1978年   3篇
  1977年   4篇
  1976年   2篇
  1975年   6篇
  1974年   3篇
  1973年   7篇
  1969年   4篇
  1966年   1篇
  1964年   1篇
  1961年   1篇
  1960年   1篇
  1958年   2篇
  1957年   2篇
  1956年   1篇
排序方式: 共有240条查询结果,搜索用时 15 毫秒
1.
Loss of β-cell mass and function can lead to insufficient insulin levels and ultimately to hyperglycemia and diabetes mellitus. The mainstream treatment approach involves regulation of insulin levels; however, approaches intended to increase β-cell mass are less developed. Promoting β-cell proliferation with low-molecular-weight inhibitors of dual-specificity tyrosine-regulated kinase 1A (DYRK1A) offers the potential to treat diabetes with oral therapies by restoring β-cell mass, insulin content and glycemic control. GNF4877, a potent dual inhibitor of DYRK1A and glycogen synthase kinase 3β (GSK3β) was previously reported to induce primary human β-cell proliferation in vitro and in vivo. Herein, we describe the lead optimization that lead to the identification of GNF4877 from an aminopyrazine hit identified in a phenotypic high-throughput screening campaign measuring β-cell proliferation.  相似文献   
2.
Correlates of psychotic and psychoticlike symptoms were examined in 60 college students who scored deviantly high on the Perceptual Aberration Scale. High scorers on this scale who also scored high on both the Impulsive Nonconformity Scale and the Depression subscale of the General Behavior Inventory (GBI) showed the most deviant psychotic and psychoticlike symptoms. Moreover, performance on a task of referential communication, the Password Task, was significantly related to such symptoms. The Perceptual Aberration Scale, the Impulsive Nonconformity Scale, and the GBI Depression subscale are recommended for concurrent use in mass screening to select individuals likely to exhibit psychotic or psychoticlike symptoms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
3.
Security countermeasures help ensure the confidentiality, availability, and integrity of information systems by preventing or mitigating asset losses from Cybersecurity attacks. Due to uncertainty, the financial impact of threats attacking assets is often difficult to measure quantitatively, and thus it is difficult to prescribe which countermeasures to employ. In this research, we describe a decision support system for calculating the uncertain risk faced by an organization under cyber attack as a function of uncertain threat rates, countermeasure costs, and impacts on its assets. The system uses a genetic algorithm to search for the best combination of countermeasures, allowing the user to determine the preferred tradeoff between the cost of the portfolio and resulting risk. Data collected from manufacturing firms provide an example of results under realistic input conditions.  相似文献   
4.
5.
The use of experiments— particularly randomized controlled trials (RCTs) where subjects are randomly assigned to treatment and control conditions—has rarely been applied to the process of improving the design of energy efficiency programs and, more fundamentally, to determining the net savings from energy efficiency programs. This paper discusses the use of experimentation in the energy efficiency program field with the hope of explaining how these experiments can be used, and identifying the barriers to their use will cause more experimentation to occur. First, a brief overview of experimental methods is presented. This discussion describes the advantages and disadvantages of conducting experiments in the context of the development and evaluation of energy efficiency programs. It then discusses barriers to the use of experimental methods (including cost and equity issues) and suggests some ways of overcoming these barriers. Finally, recommendations are made for implementing key social experiments, discussing the types of energy efficiency programs and issues that can make use of experimentation and variables that one might use for selecting treatments.  相似文献   
6.
The kinetics of desulfurization of hydrogen sulfide, using metallic copper as desulfurizer, have been investigated over a range of temperatures and pressures of hydrogen sulfide. Our results indicate that there are two stages of reaction; activation energies for the first and second stages are 63 kJ/mol and 38 kJ/mol, respectively. Possible reaction mechanisms in which the initial rate is controlled by interface reaction and the later stage is controlled by diffusion through or in the Cu2S layer are consistent with the experimental data.  相似文献   
7.
博客和业内专家认为,电子邮件营销面临的最大挑战非常复杂,如收件箱传输能力或渲染。这是真的吗?一名博学的市场人员、设计师或程序员都可以轻易解决上述两个问题,而对于其他大多数人来说,问题就不是那么简单了。这才是真正的问题。大多数公司并不知道电子邮件营销的最佳实践,同时他们内部也缺少相关的专业资源。然而,却很少有公司意识到这个问题,因为即使是写得很糟糕的电子邮件似乎仍表现不错。未造成伤害,也没有犯错,不是吗?  相似文献   
8.
9.
The use of proliferation of nanotechnology in commercial applications is driving requirements for minimal chemical processing and simple processes in industry. Carbon nanofiber (CNF) products possess very high purity levels without the need of purification processing before use and are in growing demand for this quality. Polyetherimide (PEI) has excellent mechanical and thermal performance, but its high viscosity makes its nanocomposites processing very challenging. In this study, a facile melt‐mixing method was used to fabricate PEI nanocomposites with as received and physically treated CNFs. The dispersion of CNFs was characterized by scanning electron microscopy, transmitted optical microscopy, and electrometer with large‐area electrodes. The results showed that the facile and powerful melt‐mixing method is effective in homogeneously dispersing CNFs in the PEI matrix. The flexural and tribological characteristics were investigated and the formation of spatial networks of CNFs and weak interfacial bonding were considered as competitive factors to enhanced flexural properties. The composites with 1.0 wt% CNFs showed flexural strength and toughness increased by more than 50 and 550%, respectively, but showed very high wear rate comparable with that of pure PEI. The length of the CNFs also exerted great influences on both mechanical and tribological behaviors. POLYM. ENG. SCI., 50:1914–1922, 2010. © 2010 Society of Plastics Engineers  相似文献   
10.
A reactive-power compensator (RPC) is a type of static var compensator (SVC) that is used to dynamically correct power factor to prevent voltage variation (flicker) in ac power sources due to large dynamic loads. It also minimizes total source current. Thus the application of an RPC or SVC to a load may allow addition of substantial new load to existing feeders or substations. A reactive-power compensator suited to industrial ratings (1.0-25 MVA) is described. It utilizes a force-commutated current-source bridge to provide both leading and lagging reactive power. The ability to operate both leading and lagging can reduce by 2:1 the ratings of the RPC itself and the capacitors and magnetics associated with it. The characteristics of the power circuit, the means used to control it, and the resulting dynamic performance is described. Speed of response compares favorably to the thyristor-controlled reactors now in common use as SVC's at higher MVA ratings. This RPC is suited to compensate any balanced three-phase dynamic load.  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