全文获取类型
收费全文 | 10017篇 |
免费 | 397篇 |
国内免费 | 14篇 |
专业分类
电工技术 | 140篇 |
综合类 | 35篇 |
化学工业 | 2530篇 |
金属工艺 | 211篇 |
机械仪表 | 168篇 |
建筑科学 | 535篇 |
矿业工程 | 27篇 |
能源动力 | 187篇 |
轻工业 | 941篇 |
水利工程 | 65篇 |
石油天然气 | 8篇 |
武器工业 | 1篇 |
无线电 | 688篇 |
一般工业技术 | 1972篇 |
冶金工业 | 1639篇 |
原子能技术 | 97篇 |
自动化技术 | 1184篇 |
出版年
2023年 | 59篇 |
2022年 | 89篇 |
2021年 | 149篇 |
2020年 | 119篇 |
2019年 | 117篇 |
2018年 | 154篇 |
2017年 | 172篇 |
2016年 | 240篇 |
2015年 | 199篇 |
2014年 | 273篇 |
2013年 | 406篇 |
2012年 | 379篇 |
2011年 | 507篇 |
2010年 | 419篇 |
2009年 | 397篇 |
2008年 | 420篇 |
2007年 | 381篇 |
2006年 | 389篇 |
2005年 | 311篇 |
2004年 | 289篇 |
2003年 | 260篇 |
2002年 | 219篇 |
2001年 | 211篇 |
2000年 | 200篇 |
1999年 | 224篇 |
1998年 | 474篇 |
1997年 | 335篇 |
1996年 | 265篇 |
1995年 | 168篇 |
1994年 | 163篇 |
1993年 | 169篇 |
1992年 | 131篇 |
1991年 | 105篇 |
1990年 | 122篇 |
1989年 | 111篇 |
1988年 | 95篇 |
1987年 | 97篇 |
1986年 | 93篇 |
1985年 | 78篇 |
1984年 | 91篇 |
1983年 | 79篇 |
1982年 | 92篇 |
1981年 | 87篇 |
1980年 | 70篇 |
1979年 | 74篇 |
1978年 | 73篇 |
1977年 | 111篇 |
1976年 | 127篇 |
1975年 | 72篇 |
1973年 | 52篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
This DFG-funded research project aimed to gain a better understanding of the mechanisms of the W-Cl repair principle within the framework of fundamental investigations, to contribute to the creation of the necessary basis for a broader application of the repair principle in practice. The focus was on the development of a model to describe the chloride redistribution after the application of a system sealing surface protective coating. On the basis of Fick's second law of diffusion, a mathematical model with a self-contained analytical solution was developed, with the help of which the chloride redistribution after application of a system sealing surface protective coating can be calculated under the idealized assumption of complete water saturation of the concrete. Furthermore, the influence of the dehydration of the concrete, expected as a result of the application of the repair principle W-Cl, on the chloride redistribution was investigated. On the basis of laboratory tests and numerical simulations, material-specific reduction functions were developed to quantify the relationship between the chloride diffusion coefficient and the ambient humidity. 相似文献
4.
High‐intensity sweeteners in espresso coffee: ideal and equivalent sweetness and time–intensity analysis 下载免费PDF全文
Bruna M. Azevedo Flávio L. Schmidt Helena M. A. Bolini 《International Journal of Food Science & Technology》2015,50(6):1374-1381
The efficient substitution of sucrose by a sweetener in beverages requires the application of some sensory techniques. First, one must determine the concentrations of the sweeteners under study, equivalent in sweetness to the ideal sucrose concentration. In addition, it is fundamental to determine which is most similar to sucrose. The objectives of this study were to determine the ideal sweetness for espresso coffee and the equivalent concentrations in sweetness of different sweeteners, as well as characterise the time–intensity profile of each sweetener in relation to sweetness. The sweeteners evaluated were sucralose, aspartame, neotame, a cyclamate/saccharin mixture (2:1) and stevia. The sucrose concentration considered ideal by consumers was 12.5% (w/v), and the equivalent concentrations of the sweeteners were 0.0159% for sucralose, 0.0549% for aspartame, 0.0016% for neotame, 0.0359% for the cyclamate/saccharin mixture and 0.0998% for stevia. The time–intensity analysis indicated that possibly the sweeteners neotame, aspartame and sucralose would be the best substitutes for sucrose. 相似文献
5.
A heavy crude oil has been treated with deuterated alkylating reagents (CD3I and C2D5I) and directly analyzed without any prior fractionation and chromatographic separation by high-field Orbitrap Fourier Transform Mass Spectrometry (FTMS) and Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS) using electrospray ionization (ESI). The reaction of a polycyclic aromatic sulfur heterocycles (PASHs) dibenzothiophene (DBT), in the presence of silver tetrafluoroborate (AgBF4) with ethyl iodide (C2H5I) in anhydrous dichloroethane (DCE) was optimized as a sample reaction to study heavy crude oil mixtures, and the reaction yield was monitored and determined by proton nuclear magnetic resonance spectroscopy (1H-NMR). The obtained conditions were then applied to a mixture of standard aromatic CH-, N-, O- and S-containing compounds and then a heavy crude oil, and only sulfur-containing compounds were selectively alkylated. The deuterium labeled alkylating reagents, iodomethane-d3 (CD3I) and iodoethane-d5 (C2D5I), were employed to the alkylation of heavy crude oil to selectively differentiate the tagged sulfur species from the original crude oil. 相似文献
6.
7.
Freddy A. Bernal Dr. Marcel Kaiser Prof. Dr. Bernhard Wünsch Prof. Dr. Thomas J. Schmidt 《ChemMedChem》2020,15(1):68-78
Protozoal infections are still a global health problem, threatening the lives of millions of people around the world, mainly in impoverished tropical and sub-tropical regions. Thus, in view of the lack of efficient therapies and increasing resistances against existing drugs, this study describes the antiprotozoal potential of synthetic cinnamate ester analogues and their structure-activity relationships. In general, Leishmania donovani and Trypanosoma brucei were quite susceptible to the compounds in a structure-dependent manner. Detailed analysis revealed a key role of the substitution pattern on the aromatic ring and a marked effect of the side chain on the activity against these two parasites. The high antileishmanial potency and remarkable selectivity of the nitro-aromatic derivatives suggested them as promising candidates for further studies. On the other hand, the high in vitro potency of catechol-type compounds against T. brucei could not be extrapolated to an in vivo mouse model. 相似文献
8.
9.
B. Pantchev P. Danesh K. Antonova B. Schmidt D. Grambole J. Baran 《Journal of Materials Science: Materials in Electronics》2003,14(10-12):751-752
The hydrogen content, its depth distribution, and its bonding configuration have been studied in hydrogenated amorphous silicon prepared by plasma-enhanced chemical vapor deposition with hydrogen-diluted silane. Nuclear reaction analysis and infrared spectroscopy were used to determine the total amount of hydrogen and its bonded component, respectively. It has been established that the total concentration of hydrogen does not depend on the film thickness, and has a uniform depth profile. The concentration of bonded hydrogen changes with the film thickness within the measurement accuracy. The data obtained suggest the presence of molecular (non-bonded) hydrogen, uniformly distributed in concentration across the film thickness. 相似文献
10.
Wolfgang Wendler 《电子产品世界》2006,(17):129-130
与美国同行争分夺秒抢占市场先机不同,欧洲测量仪器厂商Rohde&Schwarz公司的产品策略则相对稳健,他们的产品更专注于功能的多样化 相似文献