全文获取类型
收费全文 | 273277篇 |
免费 | 4940篇 |
国内免费 | 1735篇 |
专业分类
电工技术 | 5972篇 |
技术理论 | 2篇 |
综合类 | 1557篇 |
化学工业 | 39497篇 |
金属工艺 | 10636篇 |
机械仪表 | 8898篇 |
建筑科学 | 7995篇 |
矿业工程 | 1622篇 |
能源动力 | 7794篇 |
轻工业 | 22280篇 |
水利工程 | 2544篇 |
石油天然气 | 4719篇 |
武器工业 | 136篇 |
无线电 | 36426篇 |
一般工业技术 | 52471篇 |
冶金工业 | 49548篇 |
原子能技术 | 5304篇 |
自动化技术 | 22551篇 |
出版年
2022年 | 1903篇 |
2021年 | 3021篇 |
2020年 | 2272篇 |
2019年 | 2512篇 |
2018年 | 3916篇 |
2017年 | 4036篇 |
2016年 | 4013篇 |
2015年 | 3025篇 |
2014年 | 5052篇 |
2013年 | 12665篇 |
2012年 | 7614篇 |
2011年 | 9990篇 |
2010年 | 8188篇 |
2009年 | 9032篇 |
2008年 | 9532篇 |
2007年 | 9386篇 |
2006年 | 8524篇 |
2005年 | 7594篇 |
2004年 | 6930篇 |
2003年 | 7115篇 |
2002年 | 6537篇 |
2001年 | 6988篇 |
2000年 | 6413篇 |
1999年 | 6968篇 |
1998年 | 16931篇 |
1997年 | 11792篇 |
1996年 | 9144篇 |
1995年 | 6913篇 |
1994年 | 6137篇 |
1993年 | 5981篇 |
1992年 | 4259篇 |
1991年 | 4131篇 |
1990年 | 3944篇 |
1989年 | 3717篇 |
1988年 | 3612篇 |
1987年 | 3045篇 |
1986年 | 2971篇 |
1985年 | 3216篇 |
1984年 | 2936篇 |
1983年 | 2833篇 |
1982年 | 2646篇 |
1981年 | 2546篇 |
1980年 | 2463篇 |
1979年 | 2308篇 |
1978年 | 2109篇 |
1977年 | 2604篇 |
1976年 | 3562篇 |
1975年 | 1764篇 |
1974年 | 1729篇 |
1973年 | 1665篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
Neural Computing and Applications - With an increase in online longitudinal users’ interactions, capturing users’ precise preferences and giving accurate recommendations have become an... 相似文献
102.
In this paper, permanent magnet synchronous motors (PMSMs) are investigated. According to the feature of PMSMs, a novel state equation of PMSMs is obtained by choosing suitable state variables. Based on the state equation, robust controllers are designed via interval matrix and PI control idea. In terms of bilinear matrix inequations, sufficient conditions for the existence of the robust controller are derived. In order to reduce the conservation and the dependence on parameter, the control inputs of PMSMs are divided into two parts, a feedforward control input and a feedback control input, and relevant sufficient conditions for the existence of the controller are obtained. Because of the suitable choice of state variables, the proposed control strategies can cope with the load uncertainty and have robustness for disturbance. Finally, simulations are carried out via Matlab/Simulink soft to verify the effectiveness of the proposed control strategies. The performance of the proposed control strategies are demonstrated by the simulation results. 相似文献
103.
Chuang Yu Yu Yang Ze-xiang Wu Ji-fang Jiang Rao-ping Liao Yong-feng Deng 《Geotextiles and Geomembranes》2021,49(2):413-419
Geosynthetic clay liners (GCLs), which have a very low permeability to water and a considerably high self-healing capacity, are widely used in liner systems of landfills. In this study, a series of experimental tests were carried out under complex conditions on typical commercial GCLs from China. In particular, the effects of pH values and lead ions (Pb2+) were tested in addition to other factors. The swelling properties of natural bentonite encapsulated between geotextile components in the GCLs were tested first. The swelling capacity was reduced rapidly at pH values < 3 and concentrations of Pb2+ >40 mM. Permeability tests on GCLs with different concentrations of lead ions were then performed by using the self-developed multi-link flexible wall permeameter, and data showed that increases in lead ion concentrations greatly improved the permeability. Finally, self-healing capacity tests were conducted on needle-punched GCLs under different levels of damage. Results showed that the GCLs have a good self-healing capacity with small diameter damage holes (2 mm, close to three times the original aperture), but with a damage aperture larger than 15% of the sample area, the self-healing capacity could not prevent leakage; hence, in certain situations it will be necessary to repair the damage to meet the anti-seepage requirement. 相似文献
104.
105.
Jonathan K. Dozier Mark D. Distefano 《International journal of molecular sciences》2015,16(10):25831-25864
The use of proteins as therapeutics has a long history and is becoming ever more common in modern medicine. While the number of protein-based drugs is growing every year, significant problems still remain with their use. Among these problems are rapid degradation and excretion from patients, thus requiring frequent dosing, which in turn increases the chances for an immunological response as well as increasing the cost of therapy. One of the main strategies to alleviate these problems is to link a polyethylene glycol (PEG) group to the protein of interest. This process, called PEGylation, has grown dramatically in recent years resulting in several approved drugs. Installing a single PEG chain at a defined site in a protein is challenging. Recently, there is has been considerable research into various methods for the site-specific PEGylation of proteins. This review seeks to summarize that work and provide background and context for how site-specific PEGylation is performed. After introducing the topic of site-specific PEGylation, recent developments using chemical methods are described. That is followed by a more extensive discussion of bioorthogonal reactions and enzymatic labeling. 相似文献
106.
107.
108.
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
109.
110.