全文获取类型
收费全文 | 328381篇 |
免费 | 22020篇 |
国内免费 | 11635篇 |
学科分类
工业技术 | 362036篇 |
出版年
2024年 | 1228篇 |
2023年 | 4737篇 |
2022年 | 8118篇 |
2021年 | 11741篇 |
2020年 | 8768篇 |
2019年 | 7595篇 |
2018年 | 8752篇 |
2017年 | 9806篇 |
2016年 | 8681篇 |
2015年 | 11638篇 |
2014年 | 14472篇 |
2013年 | 18585篇 |
2012年 | 18967篇 |
2011年 | 21047篇 |
2010年 | 18061篇 |
2009年 | 17462篇 |
2008年 | 16878篇 |
2007年 | 16646篇 |
2006年 | 17216篇 |
2005年 | 15255篇 |
2004年 | 10104篇 |
2003年 | 8885篇 |
2002年 | 8274篇 |
2001年 | 7512篇 |
2000年 | 7974篇 |
1999年 | 9420篇 |
1998年 | 8843篇 |
1997年 | 7354篇 |
1996年 | 6796篇 |
1995年 | 5424篇 |
1994年 | 4462篇 |
1993年 | 3369篇 |
1992年 | 2702篇 |
1991年 | 2151篇 |
1990年 | 1681篇 |
1989年 | 1400篇 |
1988年 | 1113篇 |
1987年 | 919篇 |
1986年 | 747篇 |
1985年 | 640篇 |
1984年 | 483篇 |
1983年 | 419篇 |
1982年 | 429篇 |
1981年 | 381篇 |
1980年 | 415篇 |
1979年 | 365篇 |
1977年 | 415篇 |
1976年 | 629篇 |
1975年 | 308篇 |
1973年 | 311篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
Catastrophic convolutional codes (CC) cause an infinite number of decoded data bit errors when decoding a finite number of code symbols. A CC displays a catastrophic error propagation if the generating polynomials have a common factor. An efficient algorithm for polynomial factorization in GF(2m) is used for detecting catastrophic CC for any rate n/m and constraint length k. A general formula is derived to calculate the number of catastrophic codes in any (m, n, k) CC. 相似文献
103.
The effect of a novel flavonoid, venoruton (a mixture of mono-, di-, tri- and tetrahydroxyethylrutosides) has been investigated in healthy rat lenses and compared with diabetic cataract modelled in vitro. One mM venoruton was added to medium simulating healthy and diabetic conditions for the incubated lenses; damage was followed by either stereoscopic photography of the lenses under a Cooperative Cataract Research Group operating microscope or with our recently developed method: the leakage of lactate dehydrogenase (LDH) into the lens culture media. The increased LDH activity in the medium and observable development of the opacity were correlated with cell damage, which has been found to be associated with globular degeneration and cataract formation. The extent of opacification and LDH release is reduced if 1 mM venoruton is included in the medium. The protective effect may be related to antioxidant activity against reactive oxygen species: decreased luminol luminescence was shown after venoruton addition to either superoxide-generating hypoxanthine plus xanthine oxidase, or hydrogen peroxide. 相似文献
104.
105.
106.
One of the frequently discussed applications of artificial intelligence in motion control is the replacement of a standard proportional plus integral (PI) speed controller with a fuzzy logic (FL) speed controller. Regardless of all the work, it appears that a thorough comparison of the drive behavior under PI and FL speed control is still missing. This paper attempts to fill in this gap, by providing an in-depth comparison of operation of a vector-controlled permanent-magnet synchronous motor, using at first an experimental rig. Speed responses, obtained under PI and FL speed control, are recorded and compared for a variety of operating conditions. The transients studied include response to a large step speed command from standstill with nominal inertia and an increased inertia, response to small step speed reference change, and response to step load torque application. The transient behavior is examined for various initial speed settings, so that a thorough comparison is enabled. Experimental results are further supplemented with a set of simulation results, obtained using a different permanent-magnet machine and a different FL controller. Better generalization of the results is enabled in this way. It is shown that superiority of the FL speed control is less pronounced than it is often portrayed in the literature on the basis of limited comparisons. Indeed, in a number of cases, PI speed control provides a superior speed response. 相似文献
107.
108.
Two‐dimensional arrangements of molecules can show remarkable cooperative electronic effects. Such effects can serve to achieve direct electronic sensing of chemical and physical processes via electrostatic effects, i.e., without transfer of charge or matter between the locus of sensing and that of detection. 相似文献
109.
110.
晋城市煤炭加工利用现状、存在问题及发展建议 总被引:1,自引:0,他引:1
阐述了晋城市煤加工利用的现状 ,分析了煤炭加工利用存在的问题 ,提出了今后的发展建议 相似文献