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   1009篇
  免费   4篇
化学工业   31篇
金属工艺   3篇
机械仪表   4篇
建筑科学   5篇
能源动力   1篇
轻工业   69篇
水利工程   2篇
无线电   7篇
一般工业技术   12篇
冶金工业   834篇
自动化技术   45篇
  2020年   3篇
  2016年   2篇
  2014年   4篇
  2013年   8篇
  2012年   2篇
  2011年   11篇
  2010年   5篇
  2009年   4篇
  2008年   10篇
  2007年   7篇
  2006年   2篇
  2005年   5篇
  2004年   6篇
  2003年   4篇
  2002年   2篇
  2001年   3篇
  2000年   6篇
  1999年   29篇
  1998年   225篇
  1997年   145篇
  1996年   93篇
  1995年   50篇
  1994年   56篇
  1993年   41篇
  1992年   10篇
  1991年   10篇
  1990年   12篇
  1989年   17篇
  1988年   16篇
  1987年   10篇
  1986年   16篇
  1985年   14篇
  1983年   5篇
  1982年   5篇
  1981年   5篇
  1980年   11篇
  1979年   3篇
  1977年   29篇
  1976年   64篇
  1975年   3篇
  1963年   4篇
  1962年   4篇
  1961年   2篇
  1960年   2篇
  1959年   13篇
  1958年   5篇
  1957年   8篇
  1956年   2篇
  1954年   4篇
  1948年   7篇
排序方式: 共有1013条查询结果,搜索用时 15 毫秒
1.
2.
3.
An adaptive control concept for supply chains is presented. Its background is a complex supply chain scenario originating from the machine building domain with a focus primarily on the development of an agentbased method concerning the adaptive coordination of customer orders along the supply chain. It aims at flexibly handling disturbances in relation to the re-allocation of alternative suppliers to ensure a timely and accurate fulfilment of customer orders. The researched and described building blocks and tools originate from artificial intelligence, decision theory and operations management, which have been implemented in an agentbased simulation framework.  相似文献   
4.
Results on the enzymatic monoacylation of glycerol by aid of phenylboronic acid in organic solvents are presented. The comparison of two alternative methods indicates that the ?2-step-method”? (synthesis in one batch unit without isolation of intermediates) is in total more favourable than the ?3-step-method”? (synthesis in two batch units including isolation of intermediates), although yields are somewhat lower. Probably this disadvantage originates from an enzyme inhibition caused by residual free phenylboronic acid in the reaction system. Several varying uncommon fatty acids like (S)-17-hydroxyoctadecanoic acid, 12-hydroxyoctadecanoic acid and 2-hydroxyhexadecanoic acid have been used as oleo-components. As far as no steric hindrance is caused by these substrates, product formation is about 80% (basis ?2-step-method”?). Investigations at the Langmuir film balance showed different film states with specific transition phases for the 1(3)-(17-hydroxy)-octadecanoyl and the 1(3)-(12-hydroxy)-octadecanoyl glycerol. The monoglyceride of the 2-hydroxyhexadecanoic acid proved to be a good emulsifier. Its qualities in this respect were confirmed by the data of the surface and interfacial tension versus n-hexadecane and also by the outcome of the emulsification tests. The enzymatic acylation of a diol like 1,3-propanediol led to the 1-(17-hydroxy)-octadecanoyl-3-propanol (yield: 50%). The film behaviour of this ester was similar to that of the corresponding monoglyceride.  相似文献   
5.
The paper presents an algorithm for material interface reconstruction for data sets where fractional material information is given as a percentage for each element of the underlying grid. The reconstruction problem is transformed to a problem that analyzes a dual grid, where each vertex in the dual grid has an associated barycentric coordinate tuple that represents the fraction of each material present. Material boundaries are constructed by analyzing the barycentric coordinate tuples of a tetrahedron in material space and calculating intersections with Voronoi cells that represent the regions where one material dominates. These intersections are used to calculate intersections in the Euclidean coordinates of the tetrahedron. By triangulating these intersection points, one creates the material boundary. The algorithm can treat data sets containing any number of materials. The algorithm can also create nonmanifold boundary surfaces if necessary. By clipping the generated material boundaries against the original cells, one can examine the error in the algorithm. Error analysis shows that the algorithm preserves volume fractions within an error range of 0.5 percent per material.  相似文献   
6.
7.
The effectiveness ofLeucaena leucocephala (Lam.) de Wit, prunings as N source for maize (Zea mays L.) was evaluated in field and pot trials at Ibadan, southern Nigeria. An N deficient, sandy Apomu soil (Psammentic Usthorthent) was used. The prunings significantly increased N uptake of seedlings and N percentage in ear leaves of maize. High maize gain yield was obtained with application of 10 tons fresh prunings or a combination of 5 tons fresh prunings and N at 50 kg ha–1. The prunings as N source, appeared to be more effective when incorporated in the soil than when applied as mulch. In the pot trial, prunings applied two weeks before planting was more effective than when applied at time of planting maize. Under screen house conditions, the apparent N recovery from prunings with early incorporation about equals that of fertilizer N.  相似文献   
8.
A new ferromagnetic shape memory thin film system, Fe–Pd–Cu, was developed using ab initio calculations, combinatorial fabrication and high-throughput experimentation methods. Reversible martensitic transformations are found in extended compositional regions, which have increased fcc–fct transformation temperatures in comparison to previously published results. High resolution transmission electron microscopy verified the existence of a homogeneous ternary phase without precipitates. Curie temperature, saturation polarization and orbital magnetism are only moderately decreased by alloying with nonmagnetic Cu. Compared to the binary system; enhanced Invar-type thermal expansion anomalies in terms of an increased volume magnetostriction are predicted. Complementary experiments on splat-fabricated bulk Fe–Pd–Cu samples showed an enhanced stability of the disordered transforming Fe70Pd30 phase against decomposition. From the comparison of bulk and thin film results, it can be inferred that, for ternary systems, the Fe content, rather than the valence electron concentration, should be regarded as the decisive factor determining the fcc–fct transformation temperature.  相似文献   
9.
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