全文获取类型
收费全文 | 41295篇 |
免费 | 3145篇 |
国内免费 | 2059篇 |
专业分类
电工技术 | 2097篇 |
技术理论 | 1篇 |
综合类 | 3072篇 |
化学工业 | 8036篇 |
金属工艺 | 3086篇 |
机械仪表 | 2551篇 |
建筑科学 | 4903篇 |
矿业工程 | 1974篇 |
能源动力 | 1670篇 |
轻工业 | 2533篇 |
水利工程 | 866篇 |
石油天然气 | 1284篇 |
武器工业 | 749篇 |
无线电 | 2319篇 |
一般工业技术 | 6857篇 |
冶金工业 | 2836篇 |
原子能技术 | 453篇 |
自动化技术 | 1212篇 |
出版年
2024年 | 174篇 |
2023年 | 467篇 |
2022年 | 1059篇 |
2021年 | 1289篇 |
2020年 | 1273篇 |
2019年 | 981篇 |
2018年 | 952篇 |
2017年 | 1268篇 |
2016年 | 1253篇 |
2015年 | 1216篇 |
2014年 | 2061篇 |
2013年 | 2032篇 |
2012年 | 2498篇 |
2011年 | 2771篇 |
2010年 | 2217篇 |
2009年 | 2482篇 |
2008年 | 2075篇 |
2007年 | 3091篇 |
2006年 | 2752篇 |
2005年 | 2498篇 |
2004年 | 2041篇 |
2003年 | 1906篇 |
2002年 | 1576篇 |
2001年 | 1299篇 |
2000年 | 1135篇 |
1999年 | 896篇 |
1998年 | 669篇 |
1997年 | 547篇 |
1996年 | 480篇 |
1995年 | 384篇 |
1994年 | 344篇 |
1993年 | 239篇 |
1992年 | 141篇 |
1991年 | 102篇 |
1990年 | 78篇 |
1989年 | 78篇 |
1988年 | 57篇 |
1987年 | 21篇 |
1986年 | 13篇 |
1985年 | 15篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1963年 | 3篇 |
1959年 | 4篇 |
1956年 | 3篇 |
1955年 | 4篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
W-Cu材料室温强度和组织均匀性的影响因素 总被引:1,自引:1,他引:0
用浸透法对孔隙度为12%~17%的烧结钨进行了渗铜试验 ,研究了影响低铜含量的W -Cu材料室温бb及渗铜组织均匀性的因素 ,研究结果表明 ,铜对钨骨架的强化和韧化机制对提高W -Cu材料的室温бb 有重要作用 ;钨骨架具有合适的孔隙度是W -Cu材料获取均匀一致的渗铜组织的重要条件。 相似文献
92.
93.
94.
M. M. Rashid 《International journal for numerical methods in engineering》2002,55(4):431-450
A computational procedure for remapping material state information from one finite element mesh to another is described. The procedure is useful in connection with evolving meshes for inelastic problems, as for example occur in the context of fracture simulation and adaptive mesh refinement. The proposed method is based on weak enforcement of equality between corresponding fields on the two meshes, where piecewise‐constant fields on both meshes are generalized from the quadrature‐point values. The essential algorithmic problem is that of calculating the volume partition of an arbitrary convex region with respect to a covering set of disjoint convex regions. Instead of geometrically resolving the associated intersections, the problem is herein approximated by a constrained optimization problem, which may be readily and efficiently solved computationally. This formulation is a main contribution of the paper. Computational examples are given that illustrate the effectiveness of the proposed procedure. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
95.
钢结构住宅的技术性探讨——以清华大学钢结构学生公寓为例 总被引:6,自引:0,他引:6
以清华大学钢结构学生公寓为实例,从结构选型、材料构成、构造技术几方面对钢结构住宅的技术性问题进行分析探讨,并提出需要进一步解决的问题。 相似文献
96.
纤维素经高能射线辐照,能产生一系列的化学和物理性质的变化。本文报道在不同剂量的~(60)Coγ射线辐照下,稻草中的水溶性糖、易水解糖、难水解糖,以及氨基酸、蛋白质等物质的化学变化;用辐射与加泡涨剂相结合的方法处理稻草,可以降低剂量、提高效应。 相似文献
97.
Lithium-ion batteries are becoming more and more important not only for portable electronic devices, but also in prevision of high power electric vehicles. In such an optic, deep studies regarding all the components of a secondary battery are in development. In this study, high voltage cathode materials have been selected. Crystals with spinel structure have a 3D vacancy pathway suitable for Li-ions transport. The material under study was LiNi0.5Mn1.5O4 doped with magnesium replacing the nickel. Various samples were synthesized via three different routes: a solid-state method, a modified sol–gel method and a xerogel method. The structure and morphology of the powders were analyzed with HRTEM and XRD. Electrochemical tests were also performed. A wide range of particle sizes (from micro to nanosize) was the result of the different synthesis routes. Unfortunately pure materials were not always obtained. The electrochemical tests showed improvement of the material's cyclability, by reducing the particle size. The electrochemical tests further confirmed the existence of a Li1+dMn2−dO4 impurity. The results are quite promising, however, further improvement of the purity of the electrode composition are needed. 相似文献
98.
计算机系统在钢卷库库区管理上的应用 总被引:1,自引:0,他引:1
主要介绍了钢卷库过程计算机系统(CYC)管理库区的方法,包括钢卷的堆放方式、库区管理的策略,以及平整生产等内容,并且简述了CYC系统的运行情况。 相似文献
99.
Paolo Feraboli Attilio Masini Luigi Taraborrelli Andrea Pivetti 《Composite Structures》2007,78(4):495-506
When modern saloon cars are re-engineered as convertibles (or roadsters) it is typical for them to lose 50% or more of the body’s torsional rigidity. Consequently the vehicles rarely handle quite as crisply, nor do they ride as well as the coupes from which they derived. This paper highlights the fundamental contributions of advanced composites in achieving the desired value of handling of the Murcièlago Roadster without penalizing the overall weight of the vehicle. To compensate for the absence of the roof structure, the vehicle was strongly redesigned by introducing new structural members and reinforcing existing critical components. A new all-carbon/epoxy composite sub-frame, which spans the entire engine bay, is comprised of elliptical tubular members, and it is the first of its kind in a production vehicle. Engineering of the sub-frame, from preliminary design to manufacturing decisions, is the focus of this paper, and is achieved through a Building Block approach that sets the program within the Integrated Product Development (IPD) strategy that the Advanced Composites Division of Automobili Lamborghini S.p.A. employs for its technology demonstrators. The strategy consists in a concurrent analytical and experimental development of the product, from the initial conceptual design and coupon testing, through the stages of element and subcomponent engineering, to final component manufacturing. 相似文献
100.
采用溶胶-凝胶法制备具有介孔结构的降硫基质材料,选择具有降硫选择性的活性元素对合成的基质材料进行改性处理,考察不同的改性方法对制得的催化裂化原位降硫助剂性能的影响,并对基质材料和降硫助剂的结构进行表征。采用美国进口的ACE-R小型催化裂化评价装置将降硫助剂与催化裂化催化剂匹配进行性能评价,在不改变原催化裂化产品分布和产品性质的同时,降低原料的总硫含量,总硫降低可达40%以上。 相似文献