全文获取类型
收费全文 | 744443篇 |
免费 | 9446篇 |
国内免费 | 1686篇 |
专业分类
电工技术 | 13993篇 |
综合类 | 625篇 |
化学工业 | 114447篇 |
金属工艺 | 29627篇 |
机械仪表 | 23468篇 |
建筑科学 | 17332篇 |
矿业工程 | 4815篇 |
能源动力 | 19718篇 |
轻工业 | 60411篇 |
水利工程 | 8415篇 |
石油天然气 | 16393篇 |
武器工业 | 49篇 |
无线电 | 84777篇 |
一般工业技术 | 150240篇 |
冶金工业 | 132714篇 |
原子能技术 | 17535篇 |
自动化技术 | 61016篇 |
出版年
2021年 | 6894篇 |
2020年 | 5092篇 |
2019年 | 6517篇 |
2018年 | 11176篇 |
2017年 | 11434篇 |
2016年 | 11913篇 |
2015年 | 7520篇 |
2014年 | 12824篇 |
2013年 | 34245篇 |
2012年 | 19937篇 |
2011年 | 27056篇 |
2010年 | 21771篇 |
2009年 | 24309篇 |
2008年 | 24874篇 |
2007年 | 24582篇 |
2006年 | 21420篇 |
2005年 | 19257篇 |
2004年 | 18428篇 |
2003年 | 18307篇 |
2002年 | 17516篇 |
2001年 | 17451篇 |
2000年 | 16494篇 |
1999年 | 16676篇 |
1998年 | 40141篇 |
1997年 | 28590篇 |
1996年 | 22254篇 |
1995年 | 16930篇 |
1994年 | 15270篇 |
1993年 | 15017篇 |
1992年 | 11278篇 |
1991年 | 10998篇 |
1990年 | 10773篇 |
1989年 | 10350篇 |
1988年 | 10016篇 |
1987年 | 8912篇 |
1986年 | 8685篇 |
1985年 | 9751篇 |
1984年 | 8809篇 |
1983年 | 8503篇 |
1982年 | 7701篇 |
1981年 | 7766篇 |
1980年 | 7481篇 |
1979年 | 7368篇 |
1978年 | 7135篇 |
1977年 | 8145篇 |
1976年 | 10478篇 |
1975年 | 6343篇 |
1974年 | 6140篇 |
1973年 | 6114篇 |
1972年 | 5303篇 |
排序方式: 共有10000条查询结果,搜索用时 571 毫秒
261.
An effective practical approach that allows not only a significant reduction in the scope of practical experiments in the course of studying suspension separation processes in hydrocyclones, but also makes it possible to assess the intensity of random components of the processes and define the interrelation between such components and hydrodynamics of flows in a hydrocyclone is presented. Within the frames of the developed probabilistic‐statistical model of suspension separation in hydrocyclones on the basis of statistical self‐similarity properties, a relationship was found between determined and random components of the processes. This allowed transitioning from three‐parameter probability density functions for suspension particles in hydrocyclones to two‐parameter functions; thus significantly improving the efficiency of practical application of the developed model. 相似文献
262.
Miroslav Kárný Marko Ruman 《International Journal of Adaptive Control and Signal Processing》2021,35(5):660-675
Any knowledge extraction relies (possibly implicitly) on a hypothesis about the modelled-data dependence. The extracted knowledge ultimately serves to a decision-making (DM). DM always faces uncertainty and this makes probabilistic modelling adequate. The inspected black-box modeling deals with “universal” approximators of the relevant probabilistic model. Finite mixtures with components in the exponential family are often exploited. Their attractiveness stems from their flexibility, the cluster interpretability of components and the existence of algorithms for processing high-dimensional data streams. They are even used in dynamic cases with mutually dependent data records while regression and auto-regression mixture components serve to the dependence modeling. These dynamic models, however, mostly assume data-independent component weights, that is, memoryless transitions between dynamic mixture components. Such mixtures are not universal approximators of dynamic probabilistic models. Formally, this follows from the fact that the set of finite probabilistic mixtures is not closed with respect to the conditioning, which is the key estimation and predictive operation. The paper overcomes this drawback by using ratios of finite mixtures as universally approximating dynamic parametric models. The paper motivates them, elaborates their approximate Bayesian recursive estimation and reveals their application potential. 相似文献
263.
Simutin A. N. Deineko A. V. Zertsalov M. G. 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2021,55(4):482-486
Power Technology and Engineering - The monitoring of hydraulic structures as high-risk facilities is discussed. Monitoring should ensure the reliability and functioning of a hydraulic structure... 相似文献
264.
Zinov’eva I. V. Fedorov A. Ya. Milevskii N. A. Zakhodyaeva Yu. A. Voshkin A. A. 《Theoretical Foundations of Chemical Engineering》2021,55(4):663-670
Theoretical Foundations of Chemical Engineering - A choline chloride–sulfosalicylic acid deep eutectic solvent (DES) is proposed for dissolving the oxides Co(II), Cu(II), Zn(II), Fe(III),... 相似文献
265.
Chertkov Yu. B. Anikin M. N. Lebedev I. I. Naimushin A. G. Smol’nikov N. V. 《Atomic Energy》2021,131(1):42-45
Atomic Energy - The results of calculations and experimental determination of the neutronics characteristics of the IRT-T research reactor are presented. The IRT-T reactor is a pool reactor with... 相似文献
266.
Manika Chaudhary Milan Singh Ashwani Kumar Yogendra K. Gautam Anil K. Malik Yogesh Kumar Beer Pal Singh 《Ceramics International》2021,47(2):2094-2106
The current research work presents a facile and cost–effective co-precipitation method to prepare doped (Co & Fe) CuO and undoped CuO nanostructures without usage of any type of surfactant or capping agents. The structural analysis reveals monoclinic crystal structure of synthesized pure CuO and doped-CuO nanostructures. The effect of different morphologies on the performance of supercapacitors has been found in CV (cyclic voltammetry) and GCD (galvanic charge discharge) investigations. The specific capacitances have been obtained 156 (±5) Fg?1, 168(±5) Fg?1 and 186 (±5) Fg?1 for CuO, Co-doped CuO and Fe-doped CuO electrodes, respectively at scan rate of 5 mVs?1, while it is found to be 114 (±5) Fg?1, 136 (±5) Fg?1 and 170 (±5) Fg?1 for CuO, Co–CuO and Fe–CuO, respectively at 0.5 Ag-1 as calculated from the GCD. The super capacitive performance of the Fe–CuO nanorods is mainly attributed to the synergism that evolves between CuO and Fe metal ion. The Fe-doped CuO with its nanorods like morphology provides superior specific capacitance value and excellent cyclic stability among all studied nanostructured electrodes. Consequently, it motivates to the use of Fe-doped CuO nanostructures as electrode material in the next generation energy storage devices. 相似文献
267.
Spiridonova E. A. Rotko V. O. Samonin V. V. Podvyaznikov M. L. 《Protection of Metals and Physical Chemistry of Surfaces》2021,57(1):45-51
Protection of Metals and Physical Chemistry of Surfaces - In this work, a universal sorbent has been obtained that works according to the mechanisms of chemisorption and adsorption by impregnating... 相似文献
268.
Zakharov A. V. Rozenko S. A. 《Journal of Communications Technology and Electronics》2019,64(4):430-438
Journal of Communications Technology and Electronics - Microstrip band-pass filters (BPFs) containing quarter-wavelength resonators and a Π-shaped half-wavelength resonator placed next to each... 相似文献
269.
Dr. Alejandra A. Carriles Alberto Mills Dr. María-José Muñoz-Alonso Dr. Dolores Gutiérrez Dr. Juan M. Domínguez Prof. Dr. Juan A. Hermoso Prof. Dr. Federico Gago 《Chembiochem : a European journal of chemical biology》2021,22(2):374-391
Spontaneous mutations in the EEF1A2 gene cause epilepsy and severe neurological disabilities in children. The crystal structure of eEF1A2 protein purified from rabbit skeletal muscle reveals a post-translationally modified dimer that provides information about the sites of interaction with numerous binding partners, including itself, and maps these mutations onto the dimer and tetramer interfaces. The spatial locations of the side chain carboxylates of Glu301 and Glu374, to which phosphatidylethanolamine is uniquely attached via an amide bond, define the anchoring points of eEF1A2 to cellular membranes and interorganellar membrane contact sites. Additional bioinformatic and molecular modeling results provide novel structural insight into the demonstrated binding of eEF1A2 to SH3 domains, the common MAPK docking groove, filamentous actin, and phosphatidylinositol-4 kinase IIIβ. In this new light, the role of eEF1A2 as an ancient, multifaceted, and articulated G protein at the crossroads of autophagy, oncogenesis and viral replication appears very distant from the “canonical” one of delivering aminoacyl-tRNAs to the ribosome that has dominated the scene and much of the thinking for many decades. 相似文献
270.
Environmental concerns continue to pose the challenge to replace petroleum-based products with renewable ones completely or at least partially while maintaining comparable properties. Herein, rigid polyurethane (PU) foams were prepared using soy-based polyol for structural and thermal insulation applications. Cell size, density, thermal resistivity, and compression force deflection (CFD) values were evaluated and compared with that of petroleum-based PU foam Baydur 683. The roles of different additives, that is, catalyst, blowing agent, surfactants, and different functionalities of polyol on the properties of fabricated foam were also investigated. For this study, dibutyltin dilaurate was employed as catalyst and water as environment friendly blowing agent. Their competitive effect on density and cell size of the PU foams were evaluated. Five different silicone-based surfactants were employed to study the effect of surface tension on cell size of foam. It was also found that 5 g of surfactant per 100 g of polyol produced a foam with minimum surface tension and highest thermal resistivity (R value: 26.11 m2·K/W). However, CFD values were compromised for higher surfactant loading. Additionally, blending of 5 g of higher functionality soy-based polyol improved the CFD values to 328.19 kPa, which was comparable to that of petroleum-based foam Baydur 683. 相似文献