全文获取类型
收费全文 | 20522篇 |
免费 | 2209篇 |
国内免费 | 1361篇 |
专业分类
电工技术 | 779篇 |
综合类 | 926篇 |
化学工业 | 6078篇 |
金属工艺 | 3016篇 |
机械仪表 | 589篇 |
建筑科学 | 641篇 |
矿业工程 | 266篇 |
能源动力 | 2815篇 |
轻工业 | 865篇 |
水利工程 | 88篇 |
石油天然气 | 1587篇 |
武器工业 | 138篇 |
无线电 | 1468篇 |
一般工业技术 | 2965篇 |
冶金工业 | 1126篇 |
原子能技术 | 466篇 |
自动化技术 | 279篇 |
出版年
2024年 | 100篇 |
2023年 | 754篇 |
2022年 | 986篇 |
2021年 | 930篇 |
2020年 | 880篇 |
2019年 | 793篇 |
2018年 | 634篇 |
2017年 | 718篇 |
2016年 | 711篇 |
2015年 | 655篇 |
2014年 | 1078篇 |
2013年 | 1352篇 |
2012年 | 1296篇 |
2011年 | 1356篇 |
2010年 | 1065篇 |
2009年 | 1105篇 |
2008年 | 916篇 |
2007年 | 1219篇 |
2006年 | 1178篇 |
2005年 | 965篇 |
2004年 | 895篇 |
2003年 | 720篇 |
2002年 | 656篇 |
2001年 | 565篇 |
2000年 | 450篇 |
1999年 | 356篇 |
1998年 | 291篇 |
1997年 | 223篇 |
1996年 | 216篇 |
1995年 | 191篇 |
1994年 | 160篇 |
1993年 | 120篇 |
1992年 | 93篇 |
1991年 | 87篇 |
1990年 | 90篇 |
1989年 | 68篇 |
1988年 | 49篇 |
1987年 | 35篇 |
1986年 | 16篇 |
1985年 | 24篇 |
1984年 | 32篇 |
1983年 | 17篇 |
1982年 | 15篇 |
1981年 | 6篇 |
1979年 | 6篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1974年 | 2篇 |
1959年 | 2篇 |
1951年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
在浸泡、阴极极化、阴极极化同时迭加拉伸变形、添加As2O3毒化剂等常见致氢条件下,通过慢应变速率拉伸试验研究了SiCp/2024复合材料的力学性能,考察了断口形貌.测定了该材料在按几种常用充氢条件充氢后的氢含量.发现虽然强烈阴极极化使材料力学性能下降,但其原因在于阴极极化引起的碱性腐蚀,与氢脆无关.获得了不同于前人研究的新结论:在本文试验条件下SiCp/2024材料不发生氢脆,也不发生不可逆氢损伤,其原因与该材料难以充入氢有关. 相似文献
82.
83.
金属-橡胶硫化粘接过程中分子取向行为的间接证据 总被引:2,自引:1,他引:1
对金属-橡胶热硫化粘接复合体的剥离行为进行了研究,同一粘接试样的双向180°剥离试验显示出了巨大的差异。本文分析了弹性材料在硫化过程中的分子行为,并提出了相应的新假设,认为这是由于金属-橡胶在硫化粘接过程中分子取向交联行为所致。这种双向180°剥离破坏现象可被看作是金属-橡胶硫化粘接过程中分子取向行为的间接证据。 相似文献
84.
Hydrogen is the lightest element in nature, and so, its detection and quantitative analysis is difficult by the conventional
methods utilized for other elements. In the recent years the technique of elastic recoil detection analysis (ERD) using 1–2
MeV He+ beam has been developed to quantitatively and simultaneously analyze hydrogen and its isotopes in solids. Such a facility
has been set up using the 2 MeV Van-de-Graaff accelerator at IIT Kanpur. It facilitates H and D analysis in a material up
to a depth of ∼ 1μm with a detection sensitivity of 0·1 at.% and depth resolution of about 300 ?. The application potential of this setup is
illustrated by presenting the results of measurements performed on Al:H:D systems prepared by plasma source ion implantation
and highT
c YBCO pellets exposed to humid atmosphere. 相似文献
85.
86.
The effect of transverse stitching on the stresses in the adhesive is investigated using an adhesive sandwich model with nonlinear adhesive properties and a transverse stitching model for adhesive bonded composite single-lap and double-lap joints. Numerical results indicate that, among all stitching parameters, thread pretension and stitch density have significant effect on the peel stresses in the adhesive; increase in the thread pretension and the stitch density leads to a decrease in peel stress in the adhesive, while an increase in other parameters generally results in a negligible reduction in peel stress. The effect of stitching was found to be negligible on the shear stresses in the adhesive. Thus it is concluded that stitching is effective for the joints where peel stresses are critical and ineffective for those where shear stresses are critical. 相似文献
87.
Xiang Lu S. Sundar Kumar Iyer Jin Lee Brian Doyle Zhineng Fan Paul K. Chu Chenming Hu Nathan W. Cheung 《Journal of Electronic Materials》1998,27(9):1059-1066
We have demonstrated feasibility to form silicon-on-insulator (SOI) substrates using plasma immersion ion implantation (PIII)
for both separation by implantation of oxygen and ion-cut. This high throughput technique can substantially lower the high
cost of SOI substrates due to the simpler implanter design as well as ease of maintenance. For separation by plasma implantation
of oxygen wafers, secondary ion mass spectrometry analysis and cross-sectional transmission electron micrographs show continuous
buried oxide formation under a single-crystal silicon overlayer with sharp Si/SiO2 interfaces after oxygen plasma implantation and high-temperature (1300°C) annealing. Ion-cut SOI wafer fabrication technique
is implemented for the first time using PIII. The hydrogen plasma can be optimized so that only one ion species is dominant
in concentration and there are minimal effects by other residual ions on the ion-cut process. The physical mechanism of hydrogen
induced silicon surface layer cleavage has been investigated. An ideal gas law model of the microcavity internal pressure
combined with a two-dimensional finite element fracture mechanics model is used to approximate the fracture driving force
which is sufficient to overcome the silicon fracture resistance. 相似文献
88.
Thin-layer carbon supported Nafion-H catalysts were found to be active and highly selective (S>98%) for the partial oxidation of C1-C3 alkanes, in a three phase catalytic membrane reactor (3PCMR), under mild conditions and in the presence of H2O2. The influences of the catalyst teflon loading and H2O2 concentration on the reaction rate have been evaluated. A reaction pathway, based on the electrophilic hydroxylation of the C-H bond of alkanes with protonated hydrogen peroxide (H3O
2
+
), is discussed. 相似文献
89.
M. Saaoudi E. Chassaing M. Cherkaoui M. Ebntouhami 《Journal of Applied Electrochemistry》2002,32(12):1331-1336
Electroless NiP films, with 12 to 16 wt % P, were deposited from a moderately acid solution. Thermogravimetric analysis indicates the presence of occluded hydrogen in the layers, which desorbs upon heating. The amount of incorporated hydrogen decreases when the pH of the solution or the nickel sulfate concentration is increased; by contrast it increases with hypophosphite concentration. Cyclic voltammetry, using an electrochemical quartz crystal microbalance, confirms the existence of parasitic reactions, namely the reduction of protons of the solvent during the cathodic process and oxidation of hydrogen during the dissolution of the layers. This behaviour is in qualitative agreement with the proposed reaction scheme. 相似文献
90.
本文简要介绍了国外在开发超酸性气体过程中遇到的材料选择、腐蚀监测、水化物堵塞、超酸性气的处理和加工等问题所采取的措施和办法。 相似文献