全文获取类型
收费全文 | 865848篇 |
免费 | 11837篇 |
国内免费 | 2231篇 |
专业分类
电工技术 | 15994篇 |
综合类 | 769篇 |
化学工业 | 134572篇 |
金属工艺 | 33946篇 |
机械仪表 | 26875篇 |
建筑科学 | 21334篇 |
矿业工程 | 4983篇 |
能源动力 | 22333篇 |
轻工业 | 75048篇 |
水利工程 | 9258篇 |
石油天然气 | 16386篇 |
武器工业 | 52篇 |
无线电 | 99077篇 |
一般工业技术 | 170329篇 |
冶金工业 | 154982篇 |
原子能技术 | 18473篇 |
自动化技术 | 75505篇 |
出版年
2021年 | 7311篇 |
2019年 | 6989篇 |
2018年 | 11871篇 |
2017年 | 12121篇 |
2016年 | 12810篇 |
2015年 | 8531篇 |
2014年 | 14190篇 |
2013年 | 40338篇 |
2012年 | 22693篇 |
2011年 | 31245篇 |
2010年 | 24889篇 |
2009年 | 27807篇 |
2008年 | 28787篇 |
2007年 | 28681篇 |
2006年 | 25195篇 |
2005年 | 22938篇 |
2004年 | 22174篇 |
2003年 | 21628篇 |
2002年 | 20909篇 |
2001年 | 20571篇 |
2000年 | 19429篇 |
1999年 | 19713篇 |
1998年 | 45598篇 |
1997年 | 33213篇 |
1996年 | 25985篇 |
1995年 | 20156篇 |
1994年 | 18119篇 |
1993年 | 17629篇 |
1992年 | 13518篇 |
1991年 | 12956篇 |
1990年 | 12727篇 |
1989年 | 12301篇 |
1988年 | 11810篇 |
1987年 | 10411篇 |
1986年 | 10170篇 |
1985年 | 11941篇 |
1984年 | 11025篇 |
1983年 | 10087篇 |
1982年 | 9259篇 |
1981年 | 9298篇 |
1980年 | 8883篇 |
1979年 | 8932篇 |
1978年 | 8628篇 |
1977年 | 9824篇 |
1976年 | 12703篇 |
1975年 | 7578篇 |
1974年 | 7249篇 |
1973年 | 7208篇 |
1972年 | 6116篇 |
1971年 | 5599篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
In this paper, we present an aero‐structural model of a tethered swept wing for airborne wind energy generation. The carbon composite wing has neither fuselage nor actuated aerodynamic control surfaces and is controlled entirely from the ground using three separate tethers. The computational model is efficient enough to be used for weight optimisation at the initial design stage. The main load‐bearing wing component is a nontypical “D”‐shaped wing‐box, which is represented as a slender carbon composite shell and further idealised as a stack of two‐dimensional cross section models arranged along an anisotropic one‐dimensional beam model. This reduced 2+1D finite element model is then combined with a nonlinear vortex step method that determines the aerodynamic load. A bridle model is utilised to calculate the individual forces as a function of the aerodynamic load in the bridle lines that connect the main tether to the wing. The entire computational model is used to explore the influence of the bride on the D‐box structure. Considering a reference D‐box design along with a reference aerodynamic load case, the structural response is analysed for typical bridle configurations. Subsequently, an optimisation of the internal geometry and laminate fibre orientations is carried out using the structural computation models, for a fixed aerodynamic and bridle configuration. Aiming at a minimal weight of the wing structure, we find that for the typical load case of the system, an overall weight savings of approximately 20% can be achieved compared with the initial reference design. 相似文献
92.
93.
94.
Yana Jorge Polizer-Rocha José M. Lorenzo Daniel Pompeu Isabela Rodrigues Juliana Cristina Baldin Manoela A. Pires Maria Teresa A. Freire Francisco Jose Barba Marco Antonio Trindade 《International Journal of Food Science & Technology》2020,55(3):1018-1024
This study aimed to evaluate the physicochemical characteristics and sensory attributes of beef burgers with the addition of pea fibre as a partial substitute of meat or fat. Three formulations were prepared: control (CON) – similar to the commercial formulation; fibre/less meat (FLM)—5% meat reduction and addition of 1% pea fibre; fibre/less fat (FLF)—7% fat reduction and addition of 1% pea fibre. Non-significant differences were obtained for pH, colour parameters (L* and b*), texture profile, cooking loss and size reduction among formulations. Moreover, sensory analysis with consumers of beef burgers did not indicate differences among the formulations for all the analysed attributes. Therefore, pea fibre is a promising partial replacer for meat and fat in beef burgers due to the preservation of technological parameters and sensory acceptance. 相似文献
95.
96.
Kobrakov K. I. Kurnetsov D. N. Ruchkina A. G. Sharpar N. M. 《Theoretical Foundations of Chemical Engineering》2020,54(5):1052-1056
Theoretical Foundations of Chemical Engineering - New research results, as well as those published earlier by the authors, on the synthesis of azo compounds based on nitroanilines obtained by the... 相似文献
97.
Zhongkai Zhao Yohanes A. Situmorang Ping An Nichaboon Chaihad Jing Wang Xiaogang Hao Guangwen Xu Abuliti Abudula Guoqing Guan 《化学工程与技术》2020,43(4):625-640
In the future, hydrogen will be an important energy carrier and industrial raw material. Catalytic steam reforming of bio-oils is a promising and economically viable technology for hydrogen production. However, during the reforming process, the catalysts are rapidly deactivated due to coke formation and sintering. Thus, maintaining the activity and stability of catalysts is the key issue in this process. Optimized operation conditions could extend the catalyst lifetime by affecting the coke morphology or promoting coke gasification. This article summarizes the recent developments in the field of catalytic steam reforming of bio-oils, focusing on the operation conditions, the properties of the catalysts, and the effects of the catalyst supports. The expected insights into the catalytic steam reforming of bio-oils will provide further guidance for hydrogen production from bio-oils. 相似文献
98.
Gomes A. C. S. A. Costa L. C. Brito D. C. Frana R. J. Marques Mnica R. C. 《Polymer Bulletin》2020,77(4):1969-1981
Polymer Bulletin - In this study, we synthesized a new ion-imprinted polymer (IIP) based on introduction of amidoxime groups in acrylonitrile, complexation with Cd2+ ions and polymerization with... 相似文献
99.
A. L. Rudenko V. V. Mishakin A. V. Gonchar K. V. Kurashkin A. E. Fomin 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2020,53(6):687-689
At the hydroelectric unit No. 11 of the Nizhnekamsk hydroelectric power plant, the filling wedges of a rotor were investigated by ultrasound in the free st 相似文献
100.
Michael A. Clegg Prof. Nicholas C. O. Tomkinson Dr. Rab K. Prinjha Dr. Philip G. Humphreys 《ChemMedChem》2019,14(4):362-385
The bromodomain and extra terminal (BET) family of bromodomain-containing proteins (BCPs) have been the subject of extensive research over the past decade, resulting in a plethora of high-quality chemical probes for their tandem bromodomains. In turn, these chemical probes have helped reveal the profound biological role of the BET bromodomains and their role in disease, ultimately leading to a number of molecules in active clinical development. However, the BET subfamily represents just 8/61 of the known human bromodomains, and attention has now expanded to the biological role of the remaining 53 non-BET bromodomains. Rapid growth of this research area has been accompanied by a greater understanding of the requirements for an effective bromodomain chemical probe and has led to a number of new non-BET bromodomain chemical probes being developed. Advances since December 2015 are discussed, highlighting the strengths/caveats of each molecule, and the value they add toward validating the non-BET bromodomains as tractable therapeutic targets. 相似文献