全文获取类型
收费全文 | 52359篇 |
免费 | 2972篇 |
国内免费 | 167篇 |
专业分类
电工技术 | 729篇 |
综合类 | 308篇 |
化学工业 | 12165篇 |
金属工艺 | 1053篇 |
机械仪表 | 1221篇 |
建筑科学 | 1842篇 |
矿业工程 | 147篇 |
能源动力 | 1806篇 |
轻工业 | 8590篇 |
水利工程 | 536篇 |
石油天然气 | 264篇 |
武器工业 | 8篇 |
无线电 | 3544篇 |
一般工业技术 | 7741篇 |
冶金工业 | 8107篇 |
原子能技术 | 371篇 |
自动化技术 | 7066篇 |
出版年
2024年 | 95篇 |
2023年 | 341篇 |
2022年 | 1173篇 |
2021年 | 2144篇 |
2020年 | 1203篇 |
2019年 | 1341篇 |
2018年 | 1559篇 |
2017年 | 1663篇 |
2016年 | 1705篇 |
2015年 | 1304篇 |
2014年 | 1863篇 |
2013年 | 3135篇 |
2012年 | 2851篇 |
2011年 | 3430篇 |
2010年 | 2454篇 |
2009年 | 2545篇 |
2008年 | 2297篇 |
2007年 | 2100篇 |
2006年 | 1631篇 |
2005年 | 1577篇 |
2004年 | 1554篇 |
2003年 | 1473篇 |
2002年 | 1348篇 |
2001年 | 1112篇 |
2000年 | 825篇 |
1999年 | 828篇 |
1998年 | 2581篇 |
1997年 | 1736篇 |
1996年 | 1238篇 |
1995年 | 819篇 |
1994年 | 647篇 |
1993年 | 709篇 |
1992年 | 337篇 |
1991年 | 372篇 |
1990年 | 322篇 |
1989年 | 273篇 |
1988年 | 299篇 |
1987年 | 218篇 |
1986年 | 239篇 |
1985年 | 247篇 |
1984年 | 183篇 |
1983年 | 136篇 |
1982年 | 145篇 |
1981年 | 154篇 |
1980年 | 155篇 |
1979年 | 124篇 |
1978年 | 102篇 |
1977年 | 173篇 |
1976年 | 273篇 |
1975年 | 104篇 |
排序方式: 共有10000条查询结果,搜索用时 640 毫秒
101.
102.
103.
Igboamalu Frank Nonso Ndjiongue Alain Richard Ferreira Hendrik Christoffel 《Telecommunication Systems》2020,73(4):521-530
Telecommunication Systems - Signals from indoor access points in a wireless fidelity suffer from high attenuation as a result of the thick walls and metal structures in the multilevel-storey... 相似文献
104.
105.
Kinetic,thermodynamic parameters and in vitro digestion of tannase from Aspergillus tamarii URM 7115
Amanda Reges de Sena Tonny Cley Campos Leite Talita Camila Evaristo da Silva Nascimento Anna Carolina da Silva Catiane S. Souza Antônio Fernando de Mello Vaz 《Chemical Engineering Communications》2018,205(10):1415-1431
Tannase is an enzyme used in various industries and produced by a large number of microorganisms. The aim of this study was to evaluate tannase production to determine the biochemical, kinetic, and thermodynamic properties and to simulate tannase in vitro digestion. The tannase-producing fungal strain was isolated from “jamun” leaves and identified as Aspergillus tamarii. Temperature at 26°C for 67?h was the best combination for maximum tannase activity (6.35-fold; initial activity in Plackett–Burman design—15.53?U/mL and average final activity in Doehlert design—98.68?U/mL). The crude extract of tannase was optimally active at 40°C, pH 5.5 and 6.5. Moreover, tannase was stimulated by Na+, Ca2+, Mg2+, and Mn2+. The half-life at 40°C lasted 247.55?min. The free energy of Gibbs, enthalpy, and entropy, at 40°C, was 81.47, 16.85, and ?0.21?kJ/mol?·?K, respectively. After total digestion, 123.95% of the original activity was retained. Results suggested that tannase from A. tamarii URM 7115 is an enzyme of interest for industrial applications, such as gallic acid production, additive for feed industry, and for beverage manufacturing, due to its catalytic and thermodynamic properties. 相似文献
106.
Meza-Espinoza Libier de los Ángeles Vivar-Vera María de Lourdes García-Magaña María Sáyago-Ayerdi Sonia G. Chacón-López Alejandra Becerrea-Verdín Eduardo M. Montalvo-González Efigenia 《Food science and biotechnology》2018,27(2):509-517
Food Science and Biotechnology - The enzymatic activity and partial characterization of proteases from Bromelia karatas fruits were evaluated and compared with Bromelia pinguin proteases. The... 相似文献
107.
讨论了在VMI管理思想下对具有随机需求特性的多客户库存分配问题 ,重点论述了有效近似算法的设计过程 ,最后基于一组模拟数据给出了一个算例。 相似文献
108.
de Oliveira J.C. Hosseini M. Shirmohammadi S. Malric F. Nourian S. El Saddik A. Georganas N.D. 《Multimedia, IEEE》2003,10(3):18-29
Using Java-based tools in multimedia collaborative environments accessed over the Internet can increase an application's client base. Most operating systems support Java, and its "compile once-run everywhere" architecture is easy to maintain and update. The Java-based tools presented here let users share Internet resources, including resources originally designed for single use. 相似文献
109.
Piedade M. Sousa L. A. de Almeida T. M. Germano J. da Costa B. A. Lemos J. M. Freitas P. P. Ferreira H. A. Cardoso F. A. 《IEEE transactions on circuits and systems. I, Regular papers》2006,53(11):2384-2395
This paper presents a hand-held microsystem based on new fully integrated magnetoresistive biochips for biomolecular recognition (DNA hybridization, antibody antigen interaction, etc.). Magnetoresistive chip surfaces are chemically treated, enabling the immobilization of probe biomolecules such as DNA or antibodies. Fluid handling is also integrated in the biochip. The proposed microsystem not only integrates the biochip, which is an array of 16times16 magnetoresistive sensors, but it also provides all the electronic circuitry for addressing and reading out each transducer. The proposed architecture and circuits were specifically designed for achieving a compact, programmable and portable microsystem. The microsystem also integrates a hand-held analyzer connected through a wireless channel. A prototype of the system was already developed and detection of magnetic nanoparticles was obtained. This indicates that the system may be used for magnetic label based bioassays 相似文献
110.