全文获取类型
收费全文 | 60619篇 |
免费 | 3434篇 |
国内免费 | 165篇 |
专业分类
电工技术 | 597篇 |
综合类 | 349篇 |
化学工业 | 12460篇 |
金属工艺 | 1250篇 |
机械仪表 | 1238篇 |
建筑科学 | 2006篇 |
矿业工程 | 171篇 |
能源动力 | 1811篇 |
轻工业 | 10378篇 |
水利工程 | 569篇 |
石油天然气 | 364篇 |
武器工业 | 8篇 |
无线电 | 3659篇 |
一般工业技术 | 9161篇 |
冶金工业 | 11654篇 |
原子能技术 | 381篇 |
自动化技术 | 8162篇 |
出版年
2024年 | 98篇 |
2023年 | 429篇 |
2022年 | 979篇 |
2021年 | 1871篇 |
2020年 | 1308篇 |
2019年 | 1463篇 |
2018年 | 1982篇 |
2017年 | 2023篇 |
2016年 | 2070篇 |
2015年 | 1556篇 |
2014年 | 2168篇 |
2013年 | 4083篇 |
2012年 | 3425篇 |
2011年 | 3748篇 |
2010年 | 2863篇 |
2009年 | 2733篇 |
2008年 | 2525篇 |
2007年 | 2220篇 |
2006年 | 1743篇 |
2005年 | 1623篇 |
2004年 | 1586篇 |
2003年 | 1518篇 |
2002年 | 1351篇 |
2001年 | 1152篇 |
2000年 | 907篇 |
1999年 | 941篇 |
1998年 | 3962篇 |
1997年 | 2579篇 |
1996年 | 1733篇 |
1995年 | 1057篇 |
1994年 | 835篇 |
1993年 | 881篇 |
1992年 | 353篇 |
1991年 | 377篇 |
1990年 | 306篇 |
1989年 | 276篇 |
1988年 | 308篇 |
1987年 | 259篇 |
1986年 | 239篇 |
1985年 | 258篇 |
1984年 | 207篇 |
1983年 | 138篇 |
1982年 | 164篇 |
1981年 | 194篇 |
1980年 | 187篇 |
1979年 | 126篇 |
1978年 | 110篇 |
1977年 | 255篇 |
1976年 | 449篇 |
1975年 | 120篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
94.
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
95.
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
96.
J Comas I Rodríguez-Roda M Poch K V Gernaey C Rosen U Jeppsson 《Water science and technology》2006,53(4-5):303-311
Wastewater treatment plant operators encounter complex operational problems related to the activated sludge process and usually respond to these by applying their own intuition and by taking advantage of what they have learnt from past experiences of similar problems. However, previous process experiences are not easy to integrate in numerical control, and new tools must be developed to enable re-use of plant operating experience. The aim of this paper is to investigate the usefulness of a case-based reasoning (CBR) approach to apply learning and re-use of knowledge gained during past incidents to confront actual complex problems through the IWA/COST Benchmark protocol. A case study shows that the proposed CBR system achieves a significant improvement of the benchmark plant performance when facing a high-flow event disturbance. 相似文献
97.
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
98.
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
99.
Recently, preemption techniques have attracted considerable attention as a means to provide differentiated quality of service
in optical burst switching (OBS) networks. This paper is focused on the analysis of preemption probabilities for bursts within
the same priority class. As proposed by Vokkarane and Jue ((2003)* IEEE J Select Areas Commun 21(7): 1198–1209) an incoming
burst will preempt the burst in service, within the same priority class, if the residual length of the burst in service is
smaller than the incoming burst length. For a general case with wavelength conversion, the preemption probability of contending
bursts with a generic service distribution, not necessarily exponential, is analyzed. First, we show that the size distribution
for the preempting bursts is shifted to larger values, in comparison to the original burst size distribution. Second, we obtain
an upper and lower bound for the preemption probability. Finally, the asymptotic behavior of the OBS switch is analyzed showing
that preemption will always occur for a very large number of wavelengths. 相似文献
100.
Walter K. Sakamoto Darcy H. F. Kanda Francisco de Assis Andrade D. K. Das-Gupta 《Journal of Materials Science》2003,38(7):1465-1470
Vegetable-based polyurethane (PU) was prepared in the thin film form by spin coating. This polymer is synthesised from castor oil, which can be extracted from the seeds of a native plant in Brazil called mamona. This polymer is biocompatible and is being used as material for artificial bone. The PU was characterised by dielectric spectroscopy in a wide range of frequency (10–5 Hz to 105 Hz) and by thermally stimulated discharge current (TSDC) measurements. The glass transition temperature (T
g = 39°C) was determined and using the initial rise method the activation energy was found to be 1.58 eV. 相似文献