全文获取类型
收费全文 | 2700篇 |
免费 | 252篇 |
国内免费 | 134篇 |
专业分类
电工技术 | 133篇 |
综合类 | 323篇 |
化学工业 | 270篇 |
金属工艺 | 69篇 |
机械仪表 | 163篇 |
建筑科学 | 594篇 |
矿业工程 | 87篇 |
能源动力 | 107篇 |
轻工业 | 75篇 |
水利工程 | 104篇 |
石油天然气 | 138篇 |
武器工业 | 46篇 |
无线电 | 395篇 |
一般工业技术 | 322篇 |
冶金工业 | 74篇 |
原子能技术 | 35篇 |
自动化技术 | 151篇 |
出版年
2024年 | 10篇 |
2023年 | 59篇 |
2022年 | 68篇 |
2021年 | 59篇 |
2020年 | 94篇 |
2019年 | 69篇 |
2018年 | 53篇 |
2017年 | 74篇 |
2016年 | 68篇 |
2015年 | 87篇 |
2014年 | 182篇 |
2013年 | 163篇 |
2012年 | 242篇 |
2011年 | 220篇 |
2010年 | 173篇 |
2009年 | 169篇 |
2008年 | 156篇 |
2007年 | 169篇 |
2006年 | 165篇 |
2005年 | 119篇 |
2004年 | 111篇 |
2003年 | 114篇 |
2002年 | 65篇 |
2001年 | 67篇 |
2000年 | 59篇 |
1999年 | 41篇 |
1998年 | 48篇 |
1997年 | 42篇 |
1996年 | 27篇 |
1995年 | 26篇 |
1994年 | 19篇 |
1993年 | 22篇 |
1992年 | 13篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 9篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1976年 | 1篇 |
1965年 | 1篇 |
1960年 | 1篇 |
排序方式: 共有3086条查询结果,搜索用时 281 毫秒
1.
2.
通过对地杂波O.94μm激光后向反射率的测试,获取不同入射角的多背景后向反射率测试数据。通过对测试数据的分析处理提供特征信息,为激光探浏器设计提供依据。 相似文献
3.
An experimental arrangement has been developed for measuring the transient temperature responses and the thermal diffusivities of foil materials in the range of 10 to 300K by using the optical reflectivity technique. The cryogenic system with optical windows is designed to provide temperatures from 10 to 300 K. The front surface of a foil specimen is heated by a pulsed Nd:YAG laser. In situ measurement of the reflectivity of a continuous-wave He–Ne laser at the rear surface is conducted on the microsecond time scale. Using the temperature dependence of reflectivity, the transient temperature response is deduced. The thermal diffusivity is obtained by fitting Parker's formulae to the experimental data on temperature rise. Stainless-steel foils are chosen as samples and are studied in the region from 10 to 300 K. The accuracy is examined by comparing the present results with the theoretical temperature responses and thermal diffusivity data from the literature. Good agreement is observed. 相似文献
4.
反应器和钢烟囱整体吊装的难点和对策 总被引:1,自引:0,他引:1
介绍了在金陵石化炼油厂200万t/a柴油加氢装置建设中,将质量为237t的反应器和高60m的钢烟囱成功进行整体吊装过程中的关键技术.通过此项工程实践得出以下结论象钢烟囱这样细长重物的整体吊装,由两台吊车抬立起后,再由主吊车独立吊装就位的施工方法简单易行,安全可靠,应用范围广;结构复杂细长杆的吊装强度和挠度计算比较复杂,在计算过程中可以忽略部分次要件的质量,分别以两吊点为支点计算上下吊点所受的力,然后再按比例放余量,使两吊点受力之和等于细长杆的重力,计算挠度时,可以适当地把问题夸大化,从而建立近似的力学模型;高压厚壁重型容器的吊装,宜直接设置专门吊盖与大法兰用螺栓把紧起吊;施工现场地基坚实是保证吊车站位和吊装施工的前提条件. 相似文献
5.
Dario Pasini Luigi Garlaschelli Elza Bontempi Laura E. Depero 《Fullerenes, Nanotubes and Carbon Nanostructures》2007,15(5):367-378
The synthesis of a series of polymers and cyclopolymers bearing crown ethers of differing structure and affinities towards primary ammonium ions is discussed. These polymers have been tested in their efficiency to form structurally homogeneous thin films when blended with an amphiphilic C60 compound containing a primary ammonium ion functional group. The X-ray reflectivity characterization of the films revealed that the polymer bearing the crown ether with the least affinity for primary ammonium ions, but having the highest degree of polymerization, is the most effective in forming structurally homogeneous thin films. 相似文献
6.
M. J. Vissenberg P. W. de Bont E. M. van Oers R. A. de Haan E. Boellaard A. M. van der Kraan V. H. J. de Beer R. A. van Santen 《Catalysis Letters》1996,40(1-2):25-29
Ion exchanged CoNaY was sulfided at 473 and 673 K and subsequently heated in He at 673 and 773 K. The resulting samples were characterized by means of overall sulfur analysis, temperature programmed Ar treatment and Fourier transform infrared spectroscopy. It was shown that during He flushing at sufficiently high temperature a protolysis reaction occurs resulting in the decomposition of Co sulfide into Co2+ ions and H2S. 相似文献
7.
This two-part paper presents a closed-form procedure for evaluation of estimates of local thermomechanical stress fields in two-phase fibrous composites and laminates. The first part is concerned with a unidirectional elastic laminate subjected to uniform mechanical loads and to uniform changes in temperature. Both phases are assumed to be elastic, with temperature-dependent moduli and expansion coefficients; the solution reflects the influence of thermomechanical interactions. Exact solutions are not possible for any real system, because the local geometry is not known in detail. Instead, estimates of the fields are found from a modified Mori-Tanaka approximation. Examples are presented for two SiC/Ti---Al---Nb composites. Local stresses of interest are found after cooling from fabrication to room temperature. The presence of local yielding, and the influence of coupling terms on the local stress magnitudes are examined. Extension of the results to laminated plates is presented in Part II (Dvorak, G.J., Chen, T. & Teply, J., Composites Science and Technology, 43 (1992) 359–368, this issue). 相似文献
8.
9.
10.