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   396篇
  免费   22篇
化学工业   111篇
金属工艺   3篇
机械仪表   3篇
建筑科学   30篇
能源动力   8篇
轻工业   68篇
水利工程   1篇
无线电   9篇
一般工业技术   56篇
冶金工业   59篇
自动化技术   70篇
  2023年   3篇
  2022年   9篇
  2021年   20篇
  2020年   10篇
  2019年   10篇
  2018年   8篇
  2017年   10篇
  2016年   11篇
  2015年   9篇
  2014年   20篇
  2013年   28篇
  2012年   19篇
  2011年   33篇
  2010年   16篇
  2009年   22篇
  2008年   18篇
  2007年   19篇
  2006年   15篇
  2005年   12篇
  2004年   9篇
  2003年   15篇
  2002年   6篇
  2001年   6篇
  2000年   7篇
  1999年   7篇
  1998年   7篇
  1997年   3篇
  1996年   5篇
  1995年   5篇
  1994年   4篇
  1993年   4篇
  1992年   5篇
  1990年   3篇
  1989年   2篇
  1988年   5篇
  1985年   5篇
  1982年   2篇
  1981年   1篇
  1980年   2篇
  1979年   3篇
  1978年   1篇
  1977年   3篇
  1976年   3篇
  1974年   1篇
  1970年   1篇
  1965年   2篇
  1964年   1篇
  1962年   1篇
  1960年   1篇
  1957年   1篇
排序方式: 共有418条查询结果,搜索用时 31 毫秒
31.
The 5-HTTLPR is an insertion/deletion polymorphism in the promoter region of the serotonin transporter gene. Prior research has revealed associations between the short-allele variant of this polymorphism, enhanced self-reported negative emotionality, and hypersensitivity of fear relevant neural circuits. In a sample of 50 healthy women we examined the role of 5-HTTLPR for cognitive-affective processing of phylogenetical fear-relevant stimuli (spiders) in a dot probe task. In contrast to homozygote long-allele carriers (ll), participants carrying at least 1 short allele (ss and sl) selectively shifted attention toward pictures of spiders, when these were presented for a duration of 2,000 ms. These results argue for an involvement of 5-HTTLPR in cognitive processing of threatening stimuli and thus, underpin its general role for individual differences in negative affect. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
32.
33.
Fiber scaffolds of bioactive polysialic acid have been prepared via electrospinning for peripheral nerve regeneration. The diameter, morphology and alignment of fibers in scaffolds were adjusted by variation of electrospinning parameters, which are decisive for the cell-scaffold interaction. Due to the high water solubility of polysialic acid (poly-α-2,8-N-acetylneuraminic acid) a photoactive derivative (poly-α-2,8-N-pentenoylneuraminic acid) was used to obtain stable fiber scaffolds in water by photochemical crosslinking. At the optimized fiber scaffolds good cell viability and directed cell proliferation along the fibers was achieved by cell tests with immortalized Schwann cells.  相似文献   
34.
35.
In recent years competitive pressure in mobile markets has increased remarkably. New business models and thus new actors have entered the market. This contribution analyzes the reconfiguration of value structures and strategies in mobile markets. For this purpose, mobile network operators?? service portfolio is analyzed on the basis of a worldwide survey, and the relevant current and future value creation activities are identified with consideration of additional actors and influence factors. On that basis, roles are developed, linked with regard to value flows and combined to a reference model for the mobile market value net. Subsequently, scenario planning is used to develop a set of criteria for the construction of corresponding future scenarios and the application of the reference model is demonstrated with such a scenario.  相似文献   
36.
37.
•  This article develops a conceptual framework to assist in determining the value to be gained from long-term international assignments.  相似文献   
38.
Automobile crashes are the leading cause of death in children aged 1–14 years. Many children, however, are not properly restrained in safety seats that reduce serious injury and death. This study used a discrete choice conjoint experiment to study factors influencing the decision to use booster seats. Parents of 1714 children aged 4–9 years from nine Canadian provinces completed choice tasks presenting experimentally varied combinations of 15 4-level booster seat promotion attributes. Latent class analysis yielded three segments of parents. The choices of the Benefit Sensitive segment (50%) were most sensitive to the injury prevention benefits of booster seats. The choices of parents in the Context Sensitive segment (33.5%) were more likely to be influenced by installation complexity, oppositional behavior, and the prospect that their child may be teased for riding in booster seats. Parents in the High Risk segment (16.5%) were younger, less educated, and less knowledgeable about vehicle safety legislation. They anticipated fewer benefits, expected more barriers and were less likely to use booster seats. Simulations suggest that consistent enforcement coupled with advertising focusing on injury prevention and the use of booster seats by other parents would increase adoption.  相似文献   
39.
40.
A series of woven fabric laminar composite plates and narrow strips were fabricated from a variety of pitch-based pristine and bromine intercalated graphite fibers in an attempt to determine the influence of the weave on the electrical and thermal conduction. It was found generally that these materials can be treated as if they are homogeneous plates. The rule of mixtures describes the resistivity of the composite fairly well if it is realized that only the component of the fibers normal to the equipotential surface will conduct current. When the composite is narrow with respect to the fiber weave, however, there is a marked angular dependence of the resistance which was well modeled by assuming that the current follows only along the fibers (and not across them in a transverse direction), and that the contact resistance among the fibers in the composite is negligible. The thermal conductivity of composites made from less conductive fibers more closely followed the rule of mixtures than that of the high conductivity fibers, though this is thought to be an artifact of the measurement technique. Electrical and thermal anisotropy could be induced in a particular region of the structure by weaving together high and low conductivity fibers in different directions, though this must be done throughout all of the layers of the structure as interlaminar conduction precludes having only the top layer carry the anisotropy. The anisotropy in the thermal conductivity is considerably less than either that predicted by the rule of mixtures or the electrical resistivity.  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