全文获取类型
收费全文 | 45649篇 |
免费 | 3570篇 |
国内免费 | 2466篇 |
专业分类
电工技术 | 1266篇 |
综合类 | 2907篇 |
化学工业 | 8091篇 |
金属工艺 | 3263篇 |
机械仪表 | 2083篇 |
建筑科学 | 2799篇 |
矿业工程 | 1445篇 |
能源动力 | 2066篇 |
轻工业 | 6713篇 |
水利工程 | 745篇 |
石油天然气 | 2600篇 |
武器工业 | 240篇 |
无线电 | 6417篇 |
一般工业技术 | 6919篇 |
冶金工业 | 1471篇 |
原子能技术 | 437篇 |
自动化技术 | 2223篇 |
出版年
2024年 | 184篇 |
2023年 | 574篇 |
2022年 | 915篇 |
2021年 | 1260篇 |
2020年 | 1376篇 |
2019年 | 1236篇 |
2018年 | 1218篇 |
2017年 | 1577篇 |
2016年 | 1654篇 |
2015年 | 1650篇 |
2014年 | 2532篇 |
2013年 | 3127篇 |
2012年 | 3335篇 |
2011年 | 3598篇 |
2010年 | 2489篇 |
2009年 | 2536篇 |
2008年 | 2351篇 |
2007年 | 2859篇 |
2006年 | 2704篇 |
2005年 | 2191篇 |
2004年 | 1851篇 |
2003年 | 1643篇 |
2002年 | 1447篇 |
2001年 | 1249篇 |
2000年 | 1141篇 |
1999年 | 877篇 |
1998年 | 751篇 |
1997年 | 609篇 |
1996年 | 503篇 |
1995年 | 453篇 |
1994年 | 328篇 |
1993年 | 330篇 |
1992年 | 253篇 |
1991年 | 187篇 |
1990年 | 135篇 |
1989年 | 107篇 |
1988年 | 75篇 |
1987年 | 65篇 |
1986年 | 50篇 |
1985年 | 48篇 |
1984年 | 46篇 |
1983年 | 33篇 |
1982年 | 27篇 |
1981年 | 26篇 |
1980年 | 16篇 |
1979年 | 15篇 |
1978年 | 9篇 |
1976年 | 10篇 |
1974年 | 8篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
孙秋冬 《计算机应用与软件》2001,18(8):48-50
本文借助软件系统分层设计的思想,提出了虚拟层的概念,并给出了一个实时信息系统虚拟分层设计方案,这为实际应用中各种规模的系列系统提供了一个组态灵活的开发方法。实践证明,这个方案取得了很好的效果,并具有很强的灵活性。 相似文献
42.
Md. Abdus Sattar 《国际能源研究杂志》1993,17(1):1-7
An analytical study is made of the free and forced convection boundary layer flow past a porous medium bounded by a semi-infinite vertical porous plate. Locally similar solutions are then obtained by a perturbation method for large suction. Solutions for the velocity and temperature distributions are shown graphically for various suction velocities and values of the driving parameter Gr/R, where Gr is the Grashof number and Re is the Reynolds number. The corresponding values of the skin friction coefficient and the Nusselt number are finally shown in tabular form. 相似文献
43.
用循环伏安法对半导体Cdse_xTe_(1-x)薄膜电池的光溶解性能进行了研究。在1mol/L KCl溶液中测量光溶解产物的阴极还原特性,考察了在多硫化钠,多硫化钾及铁氰化钾溶液中的光腐蚀行为。用此方法还研究了薄膜电极表面的光刻蚀过程和pH的影响,并用X射线光电子能谱分析光刻进行不同时间后,电极表面发生的变化。 相似文献
44.
A comprehensive survey has been carried out to establish which sun-screen agents are used by the cosmetics industry in Holland. During 1978, some 200 cosmetic sun preparations, composed of forty-eight brands, were purchased and analysed to determine which u.v. absorbing compounds were present. Most of those found were identified and quantified by means of thin layer chromatography and u.v. spectrometry. A basis for this work was the proposal by the European Cosmetic Manufacturers to produce a positive list of u.v. absorbers. It was felt that by carrying out this survey, some priority could be placed on the most popular materials used by the industry. When comparing those found with the European list of u.v. absorbers 1978, only twenty-four of the sixty compounds listed could be identified in the samples. The six most frequently used were found to be:
- 1 2-Ethylhexyl.p.methoxycinnamate (nineteen brands).
- 2 2-Phenylbenzimidazole.5-sulphonic acid (eleven brands).
- 3 2-Ethoxyethyl.p.methoxycinnamate (nine brands).
- 4 3 (4′Methylbenzylidene)D,D,L-camphor (seven brands).
- 5 3-Benzylidene.D,L-camphor (six brands).
- 6 2-Hydroxy.4-methoxy.benzophenone (six brands).
45.
The nanoindenting method is based on the automatic measurement and recording of the force acting on the indenter (10−2-5 N) and the depth of indentation (10−2-200 μm). The scratch hardness or nanoscratching method is based on the continuous recording of resistance forces to movement
of the indenter impressed into the surface.
__________
Translated from Problemy Prochnosti, No. 4, pp. 132–139, July–August, 2006. 相似文献
46.
Zinc telluride thin films have been grown at room temperature and higher temperature substrates by thermal evaporation technique
in a vacuum of 10-6 torr. A main peak in the photocurrent is observed at 781 nm (1.58 eV) with two lower amplitude peaks on the lower wavelength
side and one on higher wavelength side. The evaluated thermal activation energy is found to correspond well with the main
spectral peak. From these studies it can be inferred that temperatures up to 453 K is still in the extrinsic conductivity
region of the studied ZnTe thin films.
The paper was presented at the 6th Asian Thermophysical Properties Conference (6th ATPC), held at Gauhati University, during
8–11 October 2001. 相似文献
47.
48.
Sang-Hoon Shin Sung-Dae Kim Jong-Ha Moon Jin-Hyeok Kim 《Journal of Electroceramics》2006,17(2-4):1097-1101
Er3+/Pr3+ co-doped soda-lime glass thin films have been fabricated using RF magnetron sputtering method and their structural and optical
properties have been studied. Deposition rate, crystallinity, and composition of glass thin films were investigated by scanning
electron microscopy, transmission electron microscopy, and electron probe micro area analysis. Refractive index, birefringence
and binding characteristics have been investigated using a prism coupler and X-ray photoelectron spectroscopy. Er3+/Pr3+ co-doped soda lime glass thin films were prepared by changing substrate temperature (room temp. ∼550∘C), RF power (90 W–130 W), and Ar/O2 gas flow ratio at processing pressure of 4 mTorr. Glass thin films could be obtained at the optimized processing condition
at 350∘C, RF power of 130 W, and gas flow of Ar:O2 = 40:0 with maximum deposition rate of 1.6 μm/h. Refractive index and birefringence increased from 1.5614 to 1.5838 and from
0.000154 to 0.000552, respectively, as the content of Pr3+ increased. Binding energy of Pr3d also increased as the content of Pr3+ increased. 相似文献
49.
Compared with the single sulphurating treatment, the duplex treatment of nitrocarburizing-sulphurating can more effectively improve the properties of steel such as friction-reducing, wear resistance and anti-scuffing. Under the same processing parameters, the sulphide layers were fabricated on the surface of CrMoCu alloy cast iron by single ion-sulphurating treatment and nitrocarburizing-sulphurating duplex treatment, respectively. Through the analysis of the sulphide, the effect of the nitrocarburizing on the fabrication of the sulphide layer was investigated. And the result shows that the fabrication of sulphide layer is promoted by the nitrocarburizing treatment. 相似文献
50.