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   2691篇
  免费   189篇
  国内免费   5篇
电工技术   24篇
化学工业   773篇
金属工艺   25篇
机械仪表   54篇
建筑科学   99篇
矿业工程   1篇
能源动力   75篇
轻工业   452篇
水利工程   33篇
石油天然气   5篇
无线电   189篇
一般工业技术   463篇
冶金工业   214篇
原子能技术   24篇
自动化技术   454篇
  2024年   5篇
  2023年   25篇
  2022年   96篇
  2021年   198篇
  2020年   96篇
  2019年   92篇
  2018年   97篇
  2017年   81篇
  2016年   115篇
  2015年   96篇
  2014年   112篇
  2013年   193篇
  2012年   162篇
  2011年   206篇
  2010年   148篇
  2009年   161篇
  2008年   156篇
  2007年   127篇
  2006年   93篇
  2005年   76篇
  2004年   73篇
  2003年   49篇
  2002年   41篇
  2001年   40篇
  2000年   25篇
  1999年   31篇
  1998年   43篇
  1997年   35篇
  1996年   22篇
  1995年   12篇
  1994年   13篇
  1993年   18篇
  1992年   17篇
  1991年   8篇
  1990年   9篇
  1989年   10篇
  1988年   9篇
  1987年   10篇
  1986年   10篇
  1985年   12篇
  1984年   5篇
  1983年   8篇
  1982年   7篇
  1981年   11篇
  1980年   8篇
  1979年   6篇
  1977年   7篇
  1976年   4篇
  1975年   2篇
  1955年   1篇
排序方式: 共有2885条查询结果,搜索用时 281 毫秒
1.
Software and Systems Modeling - Mobile robots operate in various environments (e.g. aquatic, aerial, or terrestrial), they come in many diverse shapes and they are increasingly becoming parts of...  相似文献   
2.
3.
4.
5.
6.
The fission yeast Schizosaccharomyces pombe is an important model organism for the study of fundamental questions in eukaryotic cell and molecular biology. A plethora of cellular processes are membrane associated and/or dependent on the proper functioning of cellular membranes. Phospholipids are not only the basic building blocks of cellular membranes; they also serve as precursors to numerous signaling molecules. In this review, we describe the biosynthetic pathways leading to major S. pombe phospholipids, how these pathways are regulated, and what is known about degradation and turnover of fission yeast phospholipids. This review also addresses the synthesis, regulation and the role of water-soluble phospholipid precursors. The last chapter of the review is devoted to the use of S. pombe for the biotechnological production of value-added lipid molecules.  相似文献   
7.
The size effects on the mean values of the mechanical properties of condensed matter and on the related variances are analysed by means of a unified approach based on the multiscale character of energy dissipation. In particular, the scaling law for fragmentation energy density is obtained taking into account the self-similarity of fragments. It is based on a generalization of the three classical comminution laws that has been performed to evaluate the energy dissipation, computing volume and surface area of the particles for one- two- and three-dimensional fragmented objects. The result is general and can be applied to different fractal energy dissipation mechanisms, e.g., plasticity. Based on this approach, the scaling laws for mean and standard deviation values of the main mechanical properties of materials can be derived, like Young's and shear elastic moduli, ultimate normal and shear stresses and strains, fracture energy and toughness.  相似文献   
8.
Non-pinched, minimum energy solutions are important class of distillation designs that offer the potential advantage of a better trade-off between capital investment and operating costs. In this paper, two important tasks associated with non-pinched distillation designs are studied. Thus the novel contributions of this work to the literature are
(1) A comprehensive methodology for finding non-pinched minimum energy designs.
(2) Understanding of the reasons for the existence of non-pinched distillation designs.
It is shown that the recent shortest stripping line distance approach of Lucia et al. [Lucia, A., Amale, A. and Taylor, R., 2007, Distillation pinch points and more. Comput Chem Eng, available on-line] is capable of systematically and reliably finding non-pinched, minimum energy distillation designs. In addition, we provide an understanding of the reasons behind the existence of non-pinched designs, which include trajectories that follow unstable branches of a pinch point curve in azeotropic systems, the inherent looping structure of trajectories in hydrocarbon separations, and the presence of ancillary constraints in multi-unit processes like extraction/distillation. Several distillation examples are studied and many numerical results and geometric illustrations are presented that show the shortest stripping line distance methodology is indeed a powerful and systematic tool for computing non-pinched, minimum energy designs and that support the underlying reason we provide for the existence of non-pinched designs.  相似文献   
9.
In this paper, the material constant sensitivity boundary integral equation is presented, and its numerical solution proposed, based on boundary element techniques. The formulation deals with plane problems with general rectilinear anisotropy. Expressions for the computation of sensitivities for displacements, tractions, strains and stresses are derived, both for boundary and interior points. The sensitivities can be computed with respect to the bulk material properties or to the properties of part of the domain (inclusions, coatings, etc.). To assess the accuracy of the proposed approach, the computed results are compared to analytical ones derived from exact solutions obtained by complex potential theory, when possible, or finite difference derivatives otherwise. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   
10.
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