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   90332篇
  免费   1360篇
  国内免费   455篇
电工技术   910篇
综合类   2342篇
化学工业   13080篇
金属工艺   4903篇
机械仪表   3223篇
建筑科学   2416篇
矿业工程   568篇
能源动力   1574篇
轻工业   4307篇
水利工程   1337篇
石油天然气   459篇
无线电   9861篇
一般工业技术   17344篇
冶金工业   2965篇
原子能技术   341篇
自动化技术   26517篇
  2023年   159篇
  2022年   303篇
  2021年   427篇
  2020年   315篇
  2019年   354篇
  2018年   14745篇
  2017年   13627篇
  2016年   10241篇
  2015年   846篇
  2014年   555篇
  2013年   867篇
  2012年   3488篇
  2011年   9837篇
  2010年   8580篇
  2009年   5851篇
  2008年   7043篇
  2007年   7958篇
  2006年   316篇
  2005年   1349篇
  2004年   1237篇
  2003年   1286篇
  2002年   634篇
  2001年   166篇
  2000年   256篇
  1999年   110篇
  1998年   135篇
  1997年   71篇
  1996年   96篇
  1995年   53篇
  1994年   55篇
  1993年   56篇
  1992年   47篇
  1991年   61篇
  1990年   32篇
  1988年   45篇
  1987年   31篇
  1984年   29篇
  1982年   27篇
  1968年   43篇
  1967年   35篇
  1966年   43篇
  1965年   44篇
  1963年   28篇
  1960年   30篇
  1959年   35篇
  1958年   39篇
  1957年   36篇
  1956年   34篇
  1955年   63篇
  1954年   68篇
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
11.
12.
The current study establishes the unprecedented involvement in the evolution and production of novel core–shell nanocomposites composed of nanosized titanium dioxide and aniline‐o‐phenylenediamine copolymer. TiO2@copoly(aniline and o‐phenylenediamine) (TiO2@PANI‐o‐PDA) core–shell nanocomposites were chemically synthesized in a molar ratio of 5:1 of the particular monomers and several weights of nano‐TiO2 via oxidative copolymerization. The construction of the TiO2@PANI‐o‐PDA core–shell nanocomposites was ascertained from Fourier transform IR spectroscopy, UV–visible spectroscopy and XRD. A reasonable thermal behavior for the original copolymer and the TiO2@PANI‐o‐PDA core–shell nanocomposites was investigated. The bare PANI‐o‐PDA copolymer was thermally less stable than the TiO2@PANI‐o‐PDA nanocomposites. The core–shell feature of the nanocomposites was found to have core and shell sizes of 17 nm and 19–26 nm, respectively. In addition, it was found that the addition of a high ratio of TiO2 nanoparticles increases the electrical conductivity and consequently lowers the electrical resistivity of the TiO2@PANI‐o‐PDA core–shell nanocomposites. The hybrid photocatalysts exhibit a dramatic photocatalytic efficacy of methylene blue degradation under solar light irradiation. A plausible interpretation of the photocatalytic degradation results of methylene blue is also demonstrated. Our setup introduces a facile, inexpensive, unique and efficient technique for developing new core–shell nanomaterials with various required functionalities and colloidal stabilities. © 2018 Society of Chemical Industry  相似文献   
13.
This paper presents an integrated passive damping approach in hybrid metal-CFRP parts for structural applications. In this concept a viscoelastic material is embedded in the joint zone of the hybrid component. To examine the connection strength single-lap-joint specimens were produced and tested and the influence of the used material combinations, different surface structures, and different process parameters i.e. the moment of cross-linking were evaluated. Afterwards, the metal-CFRP hybrids were tested in quasi-static tests to assess their connection strength and failure behaviour. Dynamic cyclic tensile tests with step-wise increased loading conditions were performed to determine the specimens damping behaviour and to estimate their fatigue performance. Finally, these results are compared to a state of the art metal-CFRP hybrid with rivets connecting both materials.  相似文献   
14.
Neural Computing and Applications - To obtain the optimal set of features in feature selection problems is the most challenging and prominent problem in machine learning. Very few human-related...  相似文献   
15.
In this paper, we consider the classical finite mixture model, which is an effective tool for modeling lifetime distributions for random samples from heterogeneous populations. We discuss new results on stochastic comparison for two finite mixtures when each of them is drawn from one of the following semiparametric families, i.e., proportional hazards, accelerated lifetime and proportional reversed hazards.  相似文献   
16.
17.
18.
Variations of Incomplete Open Cubes is the major project by the twentieth-century conceptual artist Sol LeWitt. In this paper we interpret the enumerative component of the project as embeddings of graphs. This formulation permits use of an algorithm to check the completeness of the list of the structures produced by the artist. Our conclusion is that the artist found the correct number of structures (that is, 122), but that his list contains a mistake in the presentation of a pair of incomplete cubes, a discovery that appears not to have been noted before.  相似文献   
19.
This work demonstrates the efficiency of almond gum polysaccharides (AGPs) as bioactive compounds. AGPs were first extracted using H2O2, in the presence of NaOH, at different times and temperatures. The optimal extraction conditions were 4% H2O2 and 2 N NaOH, for 7 h at 50 °C, leading to an extraction yield of 58.2% (w/w). After a purification step, the retained AGPs were characterised using high‐performance liquid chromatography showing a molecular weight of 99.3 kDa. The monosaccharide composition of AGPs were assessed using gas chromatography–mass spectrometry. AGPs were found to be a complex heteropolysaccharide with a repeating unit mainly composed of galactose, arabinose, xylose, mannose, rhamnose, and glucuronic acid with the respective ratios: 45:26:7:10:1:11. The acidic nature of the polysaccharide is due to the presence of glucuronic acid. Total antioxidant activity, free radical‐scavenging activity and reducing power assay of AGPs were investigated. The obtained results showed high antioxidant activities of AGPs. Furthermore, beyond 60 mg mL?1, AGPs exhibited bacterial growth inhibition for five pathogenic strains: Escherichia coli, Staphylococcus aureus, Enterococcus feacalis, Pseudomonas aeruginosa and Salmonella typhimurium.  相似文献   
20.
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