全文获取类型
收费全文 | 42077篇 |
免费 | 2989篇 |
国内免费 | 1227篇 |
专业分类
电工技术 | 1629篇 |
综合类 | 1941篇 |
化学工业 | 8112篇 |
金属工艺 | 1731篇 |
机械仪表 | 2101篇 |
建筑科学 | 3318篇 |
矿业工程 | 646篇 |
能源动力 | 1271篇 |
轻工业 | 2452篇 |
水利工程 | 546篇 |
石油天然气 | 1840篇 |
武器工业 | 210篇 |
无线电 | 4814篇 |
一般工业技术 | 6657篇 |
冶金工业 | 2754篇 |
原子能技术 | 513篇 |
自动化技术 | 5758篇 |
出版年
2024年 | 114篇 |
2023年 | 575篇 |
2022年 | 987篇 |
2021年 | 1514篇 |
2020年 | 1124篇 |
2019年 | 966篇 |
2018年 | 1092篇 |
2017年 | 1184篇 |
2016年 | 1201篇 |
2015年 | 1404篇 |
2014年 | 1880篇 |
2013年 | 2409篇 |
2012年 | 2507篇 |
2011年 | 2747篇 |
2010年 | 2204篇 |
2009年 | 2202篇 |
2008年 | 2176篇 |
2007年 | 2141篇 |
2006年 | 2096篇 |
2005年 | 1851篇 |
2004年 | 1322篇 |
2003年 | 1188篇 |
2002年 | 1169篇 |
2001年 | 952篇 |
2000年 | 1022篇 |
1999年 | 1096篇 |
1998年 | 1158篇 |
1997年 | 937篇 |
1996年 | 884篇 |
1995年 | 722篇 |
1994年 | 572篇 |
1993年 | 545篇 |
1992年 | 364篇 |
1991年 | 278篇 |
1990年 | 280篇 |
1989年 | 198篇 |
1988年 | 174篇 |
1987年 | 132篇 |
1986年 | 107篇 |
1985年 | 94篇 |
1984年 | 82篇 |
1983年 | 63篇 |
1982年 | 59篇 |
1981年 | 46篇 |
1980年 | 42篇 |
1979年 | 29篇 |
1978年 | 35篇 |
1977年 | 34篇 |
1976年 | 72篇 |
1975年 | 32篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
61.
Studies on the deactivations and initiations of gas phase polymerizations of 1,3‐butadiene have been achieved by Monte Carlo simulation. Initiation and deactivation control the reaction before and after the peak of the polymerization rate, respectively. The influence of polymerization temperature has been studied. Monte Carlo modeling of polymerization kinetics and mechanism was confirmed by the agreement of experimental data and simulation results of polymerizations run with a temporary evacuation of monomer. The balance of catalysts and active chains is established by both initiation and chain transfer reactions with cocatalyst, which causes a ‘pseudo‐stability’ stage. © 2003 Society of Chemical Industry 相似文献
62.
Shiao-Shien Chen Tung-Yang Chen Tien-Hao Tang Jin-Lian Su Tzer-Min Shen Jen-Kon Chen 《Electron Devices, IEEE Transactions on》2003,50(7):1683-1689
This paper proposes a novel low-leakage BiCMOS deep-trench (DT) diode in a 0.18-/spl mu/m silicon germanium (SiGe) BiCMOS process. By means of the DT and an n/sup +/ buried layer in the SiGe BiCMOS process, a parasitic vertical p-n-p bipolar transistor with an open-base configuration is formed in the BiCMOS DT diode. Based on the two-dimensional (2-D) simulation and measured results, the BiCMOS DT diode indeed has the lowest substrate leakage current as compared to the conventional p/sup +//n-well diode even at high temperature conditions, which mainly results from the existence of the parasitic open-base bipolar transistor. Considering the applications of the diode string in electrostatic discharge (ESD) protection circuit designs, the BiCMOS DT diode string also provides a good ESD performance. Owing to the characteristics of the low leakage current and high ESD robustness, it is very convenient for circuit designers to use the BiCMOS DT diode string in their IC designs. 相似文献
63.
Five studies examined whether spontaneous trait inferences uniquely reference the person who performed a trait-implying behavior. On each study trial in 5 studies, participants saw 2 faces and a behavioral sentence referring to one of them. Later, participants saw face-trait pairs and indicated whether they had seen the trait word in the sentence presented with the face. Participants falsely recognized implied traits more when these traits were paired with actors' faces than with control faces. This effect was replicated for a large set effaces (120), after a week delay between study and recognition test, when equal attention was paid to each face, and when the orientation of the face at recognition was different from the orientation at encoding. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
64.
以3D软件应用为中心的设计管理模式——PDS在配管设计中的应用 总被引:1,自引:0,他引:1
由PDS的特点入手,结合工程实践的应用情况,阐明了3D软件可以更广泛的应用于配管的设计中,强调了以3D模型为中心开展设计和管理的新模式. 相似文献
65.
A note on the Gauss-Jacobi quadrature formulae for singular integral equations of the second kind 总被引:1,自引:0,他引:1
A fast and efficient numerical method based on the Gauss-Jacobi quadrature is described that is suitable for solving Fredholm
singular integral equations of the second kind that are frequently encountered in fracture and contact mechanics. Here we
concentrate on the case when the unknown function is singular at both ends of the interval. Quadrature formulae involve fixed
nodal points and provide exact results for polynomials of degree 2n − 1, where n is the number of nodes. Finally, an application of the method to a plane problem involving complete contact is presented. 相似文献
66.
67.
68.
69.
70.
Vladimir Rozenshtein Alexander Berg Haim Levanon Uwe Krueger Dietmar Stehlik Yuri Kandrashkin Art Van Der Est 《Israel journal of chemistry》2003,43(3-4):373-381
Light-induced spin-polarized transient EPR spectra are reported for several water-soluble copper porphyrins. The spectra are assigned to the doublet ground state, with emissive spin polarization resulting from photoexcitation and subsequent electronic relaxation. In contrast to other systems for which polarization of a doublet ground state has been observed, the exchange interactions in the copper porphyrins are strong and the geometry is fixed. It is proposed that intersystem crossing from the photoexcited trip-doublet to the trip-quartet state can lead to net polarization of the spin system and that this polarization is maintained during electronic decay, possibly via charge-transfer and exciplex states. The intensity of the observed spin polarization is essentially independent of the molecular orientation in the external field, but is strongly dependent on the nature of the charged peripheral groups. Possible reasons for this behavior are discussed. 相似文献