全文获取类型
收费全文 | 228012篇 |
免费 | 16214篇 |
国内免费 | 8867篇 |
专业分类
电工技术 | 12514篇 |
技术理论 | 13篇 |
综合类 | 19805篇 |
化学工业 | 26983篇 |
金属工艺 | 12541篇 |
机械仪表 | 19939篇 |
建筑科学 | 39656篇 |
矿业工程 | 7588篇 |
能源动力 | 5879篇 |
轻工业 | 14738篇 |
水利工程 | 6611篇 |
石油天然气 | 8410篇 |
武器工业 | 2209篇 |
无线电 | 13037篇 |
一般工业技术 | 21864篇 |
冶金工业 | 10051篇 |
原子能技术 | 1218篇 |
自动化技术 | 30037篇 |
出版年
2024年 | 956篇 |
2023年 | 2582篇 |
2022年 | 4538篇 |
2021年 | 5618篇 |
2020年 | 6258篇 |
2019年 | 4935篇 |
2018年 | 4633篇 |
2017年 | 5784篇 |
2016年 | 6613篇 |
2015年 | 7143篇 |
2014年 | 15172篇 |
2013年 | 13546篇 |
2012年 | 16241篇 |
2011年 | 17265篇 |
2010年 | 13749篇 |
2009年 | 14288篇 |
2008年 | 12840篇 |
2007年 | 15679篇 |
2006年 | 13786篇 |
2005年 | 12028篇 |
2004年 | 9907篇 |
2003年 | 8983篇 |
2002年 | 7465篇 |
2001年 | 6376篇 |
2000年 | 5223篇 |
1999年 | 4194篇 |
1998年 | 3397篇 |
1997年 | 2773篇 |
1996年 | 2405篇 |
1995年 | 1883篇 |
1994年 | 1569篇 |
1993年 | 1039篇 |
1992年 | 885篇 |
1991年 | 719篇 |
1990年 | 459篇 |
1989年 | 448篇 |
1988年 | 329篇 |
1987年 | 235篇 |
1986年 | 158篇 |
1985年 | 156篇 |
1984年 | 187篇 |
1983年 | 123篇 |
1982年 | 120篇 |
1981年 | 55篇 |
1980年 | 83篇 |
1979年 | 46篇 |
1978年 | 18篇 |
1977年 | 24篇 |
1959年 | 20篇 |
1951年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
A new approach to study ergodicity of filtering processes is presented. It is based on the vanishing discount approach to discounted functional of filtering process. We show that limit superior of the Cesaro averages of the functionals is the same for all initial conditions from which the uniqueness of invariant measures of filtering processes follows. The approach is based on certain assumption for which we provide a sufficient condition using concavity arguments. In addition we show the existence of solutions to the Poisson equation corresponding to filtering process with concave functional. The assumptions are then extended to the controlled case and using similar concave arguments we obtain the existence of solutions to the Bellman equation corresponding to partially observed average cost per unit time problem. 相似文献
92.
In this paper we present the results of a simulation study to explore the ability of Bayesian parametric and nonparametric models to provide an adequate fit to count data of the type that would routinely be analyzed parametrically either through fixed-effects or random-effects Poisson models. The context of the study is a randomized controlled trial with two groups (treatment and control). Our nonparametric approach uses several modeling formulations based on Dirichlet process priors. We find that the nonparametric models are able to flexibly adapt to the data, to offer rich posterior inference, and to provide, in a variety of settings, more accurate predictive inference than parametric models. 相似文献
93.
中国传统的思维方式深深地影响了中国传统陶瓷艺术设计,中国传统陶瓷艺术设计的历史脉络清晰,深入到设计思维系统的深层,才有助于我们对当前的陶瓷设计作出有效的转化。现代陶瓷设计的观念是对传统陶瓷文化的延续和发展,深入挖掘传统思维方式的源头活水,才是发展中国现代陶瓷设计的关键。 相似文献
94.
Jantana Tangaromsuk Abhijeet P. Borole Maleeya Kruatrachue Prayad Pokethitiyook 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(10):1375-1380
BACKGROUND: A single‐stage reactor, in which the growth of bacterial culture, induction of desulfurizing enzymes, and desulfurization reaction are carried out in a single step, was adopted to investigate desulfurization of dibenzothiophene (DBT) at high cell densities. Rhodococcus erythropolis, IGTS8 was used as the biocatalyst. Optimal conditions for bacterial growth and DBT desulfurization were investigated. RESULTS: Optimization of fermentation conditions was necessary to obtain high cell densities including controlling accumulation of acetate. Under optimal operating conditions, the maximum optical density at 600 nm (OD600) was measured to be 26.6 at 118 h of cultivation. When biodesulfurization of DBT in model oil with a high cell density culture of IGTS8 was investigated, accumulation of sulfate was found to limit the extent of desulfurization. A sulfate removal step was added to obtain a single‐stage integrated biodesulfurization process. Sulfate removal was achieved via an aqueous bleed stream and use of a separation unit to recycle the organic phase. CONCLUSION: A proof of principle of a complete system capable of biocatalyst growth, induction, desulfurization and by‐product separation was demonstrated. This system enables simplification of the biodesulfurization process and has potential to lower the operating cost of the bioprocess. Copyright © 2008 Society of Chemical Industry 相似文献
95.
Basem Abdullah & Rula Al-Najdawi 《International Journal of Food Science & Technology》2005,40(5):537-543
Samples of chicken meat from spent laying hens were obtained by four different methods: (1) manual deboning of whole carcasses; (2) manual deboning of skinned carcasses; (3) mechanical deboning of whole carcasses; and (4) mechanical deboning of skinned carcasses. The meat was packaged, frozen and stored at ?18 °C for up to 3 months. Functional properties studied were pH, emulsifying capacity (EC) and water‐holding capacity (WHC) and, in addition, pigment concentration was investigated. Sensory properties included aroma, colour, texture and overall acceptability, as judged by a trained panel using a nine‐point hedonic scale. Removal of the skin prior to deboning by either method gave significantly higher values (P < 0.05) for EC, while WHC values were not significantly different among the experimental treatments, despite higher pH values for mechanically‐deboned meat, with and without skin. Pigment concentrations were highest in meat from Treatment 4 and lowest for Treatment 1, but values for both methods of deboning were affected by the presence of skin. There were no significant differences between treatments for any of the sensory properties studied. Changes occurring in the meat during frozen storage are described. 相似文献
96.
97.
David Lloyd Suzie Morrell Helle N. Carlsen Hans Degn Phillip E. James Christopher C. Rowlands 《Yeast (Chichester, England)》1993,9(8):825-833
Saccharomyces cerevisiae HSc was grown with ethanol at concentrations up to 10% (v/v). The immediate effects of additions of externally added ethanol on CO2 production and O2 consumption of washed organisms were studied by stopped-flow membrane inlet quadrupole mass spectrometry. Fermentative activities of organisms grown with ethanol (0–5% v/v) showed similar sensitivities to inhibition by ethanol, whereas those grown with 10% (v/v) ethanol had become protected and were markedly less sensitive. The fluidity of subcellular membrane fractions was measured by determination of the temperature dependence of the rotational order parameter of the spin label 5-doxyl stearic acid (free radical) by electron spin resonance. Mitochondria prepared from yeasts grown with 0, 7 and 9% (v/v) ethanol showed similar overall fluidity, although differences in temperature-dependent behaviour indicate altered lipid composition or lateral phase separations. On the other hand the microsomal fraction from organisms grown with 9% ethanol showed a remarkable increase in fluidity. These data suggest that the protective effects of growth with ethanol near the limit of tolerance on fermentative activities may arise from altered plasma membrane fluidity properties. 相似文献
98.
99.
根据我国专利法的原则,在对我国催化重整和芳烃生产专利检索过程和结果进行分析的基础上,阐述了对目前我国催化重整工艺专利市场的几点看法并提出对策。 相似文献
100.
本文研究了浸胶工艺对Nomex蜂窝性能的影响,分析探讨了提高Nomex蜂窝性能及外观质量的途径。研究结果表明:采取新的浸胶工艺制作的Nomex蜂窝,各项性能全面达到法国宇航材料标准。 相似文献