全文获取类型
收费全文 | 440931篇 |
免费 | 7677篇 |
国内免费 | 1429篇 |
专业分类
电工技术 | 7989篇 |
综合类 | 369篇 |
化学工业 | 67354篇 |
金属工艺 | 14867篇 |
机械仪表 | 12458篇 |
建筑科学 | 13357篇 |
矿业工程 | 974篇 |
能源动力 | 12038篇 |
轻工业 | 46018篇 |
水利工程 | 3613篇 |
石油天然气 | 1932篇 |
武器工业 | 18篇 |
无线电 | 57308篇 |
一般工业技术 | 81372篇 |
冶金工业 | 80146篇 |
原子能技术 | 5770篇 |
自动化技术 | 44454篇 |
出版年
2021年 | 3204篇 |
2020年 | 2162篇 |
2019年 | 2950篇 |
2018年 | 4488篇 |
2017年 | 4497篇 |
2016年 | 4826篇 |
2015年 | 4047篇 |
2014年 | 6559篇 |
2013年 | 21297篇 |
2012年 | 11521篇 |
2011年 | 16354篇 |
2010年 | 12636篇 |
2009年 | 14172篇 |
2008年 | 15303篇 |
2007年 | 15702篇 |
2006年 | 14047篇 |
2005年 | 13105篇 |
2004年 | 12515篇 |
2003年 | 12185篇 |
2002年 | 11748篇 |
2001年 | 11710篇 |
2000年 | 10718篇 |
1999年 | 11226篇 |
1998年 | 24466篇 |
1997年 | 18041篇 |
1996年 | 14329篇 |
1995年 | 11417篇 |
1994年 | 10191篇 |
1993年 | 9764篇 |
1992年 | 7528篇 |
1991年 | 7023篇 |
1990年 | 6720篇 |
1989年 | 6407篇 |
1988年 | 6110篇 |
1987年 | 5185篇 |
1986年 | 5084篇 |
1985年 | 6308篇 |
1984年 | 5951篇 |
1983年 | 5074篇 |
1982年 | 4729篇 |
1981年 | 4679篇 |
1980年 | 4426篇 |
1979年 | 4306篇 |
1978年 | 3979篇 |
1977年 | 4732篇 |
1976年 | 6260篇 |
1975年 | 3276篇 |
1974年 | 3156篇 |
1973年 | 3029篇 |
1972年 | 2416篇 |
排序方式: 共有10000条查询结果,搜索用时 303 毫秒
111.
112.
113.
114.
Joo H. Kang Eujin Um Alexander Diaz Harry Driscoll Melissa J. Rodas Karel Domansky Alexander L. Watters Michael Super Howard A. Stone Donald E. Ingber 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(42):5657-5666
Magnetic nanoparticles have been employed to capture pathogens for many biological applications; however, optimal particle sizes have been determined empirically in specific capturing protocols. Here, a theoretical model that simulates capture of bacteria is described and used to calculate bacterial collision frequencies and magnetophoretic properties for a range of particle sizes. The model predicts that particles with a diameter of 460 nm should produce optimal separation of bacteria in buffer flowing at 1 L h−1. Validating the predictive power of the model, Staphylococcus aureus is separated from buffer and blood flowing through magnetic capture devices using six different sizes of magnetic particles. Experimental magnetic separation in buffer conditions confirms that particles with a diameter closest to the predicted optimal particle size provide the most effective capture. Modeling the capturing process in plasma and blood by introducing empirical constants (ce), which integrate the interfering effects of biological components on the binding kinetics of magnetic beads to bacteria, smaller beads with 50 nm diameters are predicted that exhibit maximum magnetic separation of bacteria from blood and experimentally validated this trend. The predictive power of the model suggests its utility for the future design of magnetic separation for diagnostic and therapeutic applications. 相似文献
115.
J. Grune K. Sempert M. Kuznetsov T. Jordan 《International Journal of Hydrogen Energy》2021,46(23):12487-12496
This paper presents results of experimental investigations on spherical and cylindrical flame propagation in pre-mixed H2/air-mixtures in unconfined and semi-confined geometries. The experiments were performed in a facility consisting of two transparent solid walls with 1 m2 area and four weak side walls made from thin plastic film. The gap size between the solid walls was varied stepwise from thin layer geometry (6 mm) to cube geometry (1 m). A wide range of H2/air-mixtures with volumetric hydrogen concentrations from 10% to 45% H2 was ignited between the transparent solid walls. The propagating flame front and its structure was observed with a large scale high speed shadow system. Results of spherical and cylindrical flame propagation up to a radius of 0.5 m were analyzed. The presented spherical burning velocity model is used to discuss the self-acceleration phenomena in unconfined and unobstructed pre-mixed H2/air flames. 相似文献
116.
117.
118.
119.
120.
Chunliang Li Theo Veldhuis Bart Reuvers Rafaël J Sablong Cor E Koning 《Polymer International》2020,69(1):24-30
Limonene‐derived polycarbonate‐based alkyd resins (ARs) have been prepared by copolymerization of limonene dioxide with CO2, catalysed by a β‐diiminate zinc–bis(trimethylsilyl)amido complex, and subsequent chemical modification with soybean oil fatty acids using triphenylethylphosphonium bromide as the catalyst. This quantitative partial modification was realized via epoxy–carboxylic acid chemistry, affording ARs with higher oil lengths, lower polydispersities and higher glass transition temperatures (Tg) in comparison to a conventional polyester AR based on phthalic acid, multifunctional polyol pentaerythritol and soybean fatty acid. The novel limonene polycarbonate AR and the conventional polyester AR were evaluated as coatings and both the physical drying (without the presence of the oxidative drying accelerator Borchi® Oxy Coat) and chemical curing (with Borchi® Oxy Coat) processes of these coatings were monitored by measuring the König hardness and complex modulus development with time. A better performance was obtained for the alkyd paint containing polycarbonates modified with fatty acids (FA‐PCs), which showed a faster chemical drying, a higher König hardness and a higher Tg in coating evaluation, demonstrating that the fully renewable FA‐PCs are promising resins for alkyd paint applications. © 2019 Society of Chemical Industry 相似文献