全文获取类型
收费全文 | 7623篇 |
免费 | 94篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 40篇 |
综合类 | 2篇 |
化学工业 | 693篇 |
金属工艺 | 64篇 |
机械仪表 | 67篇 |
建筑科学 | 144篇 |
矿业工程 | 23篇 |
能源动力 | 76篇 |
轻工业 | 261篇 |
水利工程 | 24篇 |
石油天然气 | 14篇 |
无线电 | 345篇 |
一般工业技术 | 601篇 |
冶金工业 | 4888篇 |
原子能技术 | 37篇 |
自动化技术 | 444篇 |
出版年
2022年 | 31篇 |
2021年 | 60篇 |
2020年 | 44篇 |
2019年 | 32篇 |
2018年 | 40篇 |
2017年 | 39篇 |
2016年 | 63篇 |
2015年 | 42篇 |
2014年 | 61篇 |
2013年 | 201篇 |
2012年 | 97篇 |
2011年 | 148篇 |
2010年 | 103篇 |
2009年 | 124篇 |
2008年 | 114篇 |
2007年 | 106篇 |
2006年 | 103篇 |
2005年 | 109篇 |
2004年 | 113篇 |
2003年 | 90篇 |
2002年 | 73篇 |
2001年 | 51篇 |
2000年 | 57篇 |
1999年 | 208篇 |
1998年 | 1511篇 |
1997年 | 864篇 |
1996年 | 550篇 |
1995年 | 338篇 |
1994年 | 295篇 |
1993年 | 309篇 |
1992年 | 92篇 |
1991年 | 107篇 |
1990年 | 81篇 |
1989年 | 97篇 |
1988年 | 101篇 |
1987年 | 91篇 |
1986年 | 88篇 |
1985年 | 102篇 |
1984年 | 59篇 |
1983年 | 45篇 |
1982年 | 49篇 |
1981年 | 71篇 |
1980年 | 66篇 |
1979年 | 39篇 |
1978年 | 46篇 |
1977年 | 127篇 |
1976年 | 189篇 |
1975年 | 26篇 |
1974年 | 28篇 |
1973年 | 22篇 |
排序方式: 共有7723条查询结果,搜索用时 0 毫秒
1.
2.
3.
A simple method was developed for the determination of dietary fiber in multicomponent foods. The method involves dispersing the sample into pH 7.4 phosphate buffer and adding bile and pancreatic enzyme as described. Results were comparable to AOAC methods with correlation coefficients of 86% for multicomponent dinners and 89% for breakfast foods. Coefficients of variation ranged from 7.4 to 20.0% for multicomponent foods and 1.0 to 3.6% for single component foods. In addition, blind duplicate samples had a correlation of 0.99. The described method required less time, labor, and manipulation than AOAC methods. 相似文献
4.
5.
Henry Krasemann 《Datenschutz und Datensicherheit - DuD》2006,30(4):211-214
Von eBay bis Xbox Live — wer im Internet unterwegs ist, nutzt viele (Teil-) Identit?ten. Um Waren zu verkaufen oder Dienste
anzubieten, tritt man anders auf, als wenn man einfach nur online spielen m?chte. Pseudonyme helfen die Privatsph?re zu wahren.
Doch nicht immer ist die Modifikation von Identit?tsmerkmalen zul?ssig. 相似文献
6.
Comments on the article by J. Macnamara and G. Austin (see record 1994-05070-001) suggesting that Piaget seriously misinterpreted the significance of children's documented difficulties in correctly responding to tasks involving conservation of quantity. It is shown that Macnamara and Austin make some basic errors in their analysis of the Piagetian position and that their alternative theory of how children learn to conserve is both inconsistent with empirical evidence and epistemologically untenable. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
7.
Add-drop filters are demonstrated using silica-on-silicon optical waveguide technology. This device consists of a full directional coupler subdivided by Mach-Zehnder sections. Tapering of the coupling coefficients is experimentally shown to dramatically reduce the filters' sidelobes. Only one photolithographic step is required using the silica planar waveguide technology, yielding accurate wavelength control of the filters. Excellent agreement between measurement and design was achieved 相似文献
8.
F Neukirch I Pin J Knani C Henry C Pison R Liard S Romazzini J Bousquet 《Canadian Metallurgical Quarterly》1995,89(10):685-692
BACKGROUND: This study is part of the European Community Respiratory Health Survey (ECRHS), which uses a common methodology in different areas throughout the world. This paper describes the prevalences of reported asthma, asthma-like symptoms and nasal allergies, their relationships to age group and sex, and the relationships of asthma-like symptoms to current asthma, in the general population aged 20-44 years of three French urban areas. METHODS: The study population of 2804 subjects in Grenoble, 3774 in Montpellier and 3152 in Paris (18th district), randomly selected from electoral rolls, answered a postal questionnaire (stage I of ECRHS). The response rates were 77.8%, 68.6% and 74.4%, respectively. RESULTS: The prevalences were approximately 14% for wheezing, 16% for chest tightness and 4.5% for nocturnal shortness of breath in the three areas. Asthma attacks in the last 12 months were reported by 2.7% of subjects in Grenoble, 3.5% of subjects in Montpellier and 4.0% of subjects in Paris (P = 0.02). For nasal allergies, the prevalences were 28.0%, 34.3% and 30.8%, respectively (P < 0.001). Asthma was inversely correlated to age (higher prevalence in the youngest) but was not related to sex. Neither age distribution nor sex ratio explained the differences between areas. Among the asthma-like symptoms, wheezing and nocturnal shortness of breath correlated strongly with asthma, chest tightness correlated moderately and nocturnal coughing correlated poorly. CONCLUSION: The prevalences observed were higher than expected from previous comparable French studies in young adults. These results are consistent with the hypothesis of a recent increase of asthma and allergies. 相似文献
9.
beta2-Integrin adhesion molecules play crucial roles in monocyte transmigration and adherence to the inflamed extracellular matrix. While integrin engagement contributes to inflammatory cell activation, little is known about the precise signaling pathways that are important to integrin-dependent monocyte activation. We examined the role of tyrosine phosphorylation and extracellular-signal regulated kinase (ERK) activity in beta2-integrin signaling in monocytes. Cross-linking of the LFA-1 (CD11a/CD18) and MAC-1 (CD11b/CD18) integrins on the surface of THP-1 monocytic cells induced the accumulation of tyrosine phosphoproteins. As part of this signal both ERK-1 and ERK-2 are tyrosine phosphorylated. In vitro kinase assays documented an increase in ERK-2 activity following both LFA-1 and MAC-1 cross-linking. beta2-Integrin cross-linking also led to a marked increase in 4-h procoagulant activity (PCA) in THP-1 cells and purified human monocytes. Inhibition of tyrosine phosphorylation by genistein (10 microg/ml), or selective ERK inhibition with PD98059 (10 microM), was able to block the integrin-dependent induction of PCA in both THP-1 cells and human monocytes. Thus, beta2 integrin signaling in monocytic cells can flow through the tyrosine phosphorylation and activation of the ERK mitogen activated protein kinases, which is essential for the subsequent expression of tissue factor. These results suggest that the ERK proteins likely function to integrate various adhesion-dependent signals during the process of monocyte transmigration. 相似文献
10.
Considering the critical contribution of your rectifier to the safe, effective, and reliable operation of your electrocoating process, the selection and maintenance of the optimum unit for your operation is time well spent. 相似文献