全文获取类型
收费全文 | 193922篇 |
免费 | 20982篇 |
国内免费 | 9928篇 |
专业分类
电工技术 | 5084篇 |
技术理论 | 6篇 |
综合类 | 13920篇 |
化学工业 | 35654篇 |
金属工艺 | 36832篇 |
机械仪表 | 10145篇 |
建筑科学 | 30340篇 |
矿业工程 | 5962篇 |
能源动力 | 3145篇 |
轻工业 | 11919篇 |
水利工程 | 3673篇 |
石油天然气 | 5500篇 |
武器工业 | 1614篇 |
无线电 | 7252篇 |
一般工业技术 | 24994篇 |
冶金工业 | 20496篇 |
原子能技术 | 1258篇 |
自动化技术 | 7038篇 |
出版年
2024年 | 460篇 |
2023年 | 3170篇 |
2022年 | 6017篇 |
2021年 | 8824篇 |
2020年 | 6747篇 |
2019年 | 5823篇 |
2018年 | 5869篇 |
2017年 | 7636篇 |
2016年 | 8779篇 |
2015年 | 9617篇 |
2014年 | 12632篇 |
2013年 | 12628篇 |
2012年 | 13438篇 |
2011年 | 13523篇 |
2010年 | 10413篇 |
2009年 | 10747篇 |
2008年 | 9079篇 |
2007年 | 12286篇 |
2006年 | 11850篇 |
2005年 | 9796篇 |
2004年 | 7892篇 |
2003年 | 6803篇 |
2002年 | 5570篇 |
2001年 | 4605篇 |
2000年 | 3936篇 |
1999年 | 3087篇 |
1998年 | 2265篇 |
1997年 | 1988篇 |
1996年 | 1787篇 |
1995年 | 1385篇 |
1994年 | 1267篇 |
1993年 | 900篇 |
1992年 | 781篇 |
1991年 | 563篇 |
1990年 | 572篇 |
1989年 | 526篇 |
1988年 | 240篇 |
1987年 | 191篇 |
1986年 | 110篇 |
1985年 | 133篇 |
1984年 | 122篇 |
1983年 | 92篇 |
1982年 | 103篇 |
1981年 | 57篇 |
1980年 | 98篇 |
1979年 | 41篇 |
1966年 | 27篇 |
1964年 | 38篇 |
1962年 | 64篇 |
1959年 | 36篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
采用竖式炉流动法制备的碳纳米管经液相阳极氧化表面处理后增强ABS热塑性工程塑料。复合材料的力学性能研究显示:碳纳米管的加入有效提高了复合材料的拉伸性能,但材料的耐冲击性能下降。当碳纳米管含量为12 wt%时,复合材料的拉伸强度由45.00 MPa提高到69.96 MPa,杨氏模量由0.75 GPa提高到1.93 GPa。对碳纳米管/ABS复合材料的反射系数测定表明:复合材料在一定频率范围内有雷达波吸收性能。 相似文献
992.
993.
T.‐S. Kang B.S. Harrison M. Bouguettaya T.J. Foley J.M. Boncella K.S. Schanze J.R. Reynolds 《Advanced functional materials》2003,13(3):205-210
Near‐infrared‐emitting electroluminescent (EL) devices using blue‐light‐emitting polymers blended with the Yb complexes Yb(DBM)3phen (DBM = dibenzoylmethane), Yb(DNM)3phen (DNM = dinaphthoylmethane), and Yb(TPP)L(OEt) (L(OEt) = [(C5H5)Co{P(O)Et2}3]–) have been studied. EL devices composed of Yb(DNM)3phen blended with PPP‐OR11 showed enhanced near‐IR output at 977 nm when compared to those fabricated with Yb(DBM)3phen/PPP‐OR11 blends. The maximum near‐IR external efficiencies of the devices with Yb(DBM)3phen and Yb(DNM)3phen are, respectively, 7 × 10–5 (at 6 V and at 0.81 mA mm–2) and 4 × 10–4 (at 7 V, and 0.74 mA mm–2). The optimal blend composition for EL device performance consisted of PPP‐OR11 blended with 10–20 mol‐% Yb(DNM)3phen. A device fabricated using Yb‐(TPP)L(OEt)/PPP‐OR11 showed significantly enhanced near‐IR output efficiency, and future efforts will focus on devices fabricated using porphyrin‐based materials. 相似文献
994.
Evaluating Liquefaction Strength of Partially Saturated Sand 总被引:1,自引:0,他引:1
A method is presented for evaluating the liquefaction strength of partially saturated sand using the compression wave velocity (P-wave velocity), a new indicator of saturation. Based on laboratory test results, an empirical correlation that relates the liquefaction strength with the pore pressure coefficient B is firstly proposed. The strength is defined as the cyclic stress ratio required to cause liquefaction at a specified number of cycles. With the aid of a theoretical relation between B and the P-wave velocity, an explicit correlation of more interest is then established between the liquefaction strength of sand and its P-wave velocity. A comparison of the predictions using this explicit correlation with laboratory measurements shows a satisfactory agreement. The significance of this method lies in that it makes it possible to evaluate the liquefaction strength of sand as affected by saturation through the measurement of P-wave velocity, which can be made not only in the laboratory but particularly in the field. 相似文献
995.
996.
We look at the task of computing the time-evolution of a non-linear system for a long time, in our case under random external
influences. Our specific example is the fatigue evaluation of a wind turbine. To facilitate such a computation, we look at
a reduction of the computational effort by projecting everything on a low-dimensional basis. In this case we take the Karhunen-Loève
basis generated from running the model a little while under the random loading. It is important that the error which is caused
by this reduction process can be controlled. We estimate the error by dual or adjoint methods. This in turn allows the process
of model reduction to be performed adaptively.
Dedicated to the memory of Prof. Mike Crisfield, for his cheerfulness and cooperation as a colleague and friend over many
years. 相似文献
997.
结合化肥厂丁辛醇装置薄管板换热器的设计 ,着重分析薄管板的特点 ,应用合理的计算方法对薄管板进行强度校核 ,验证这一新型换热器的安全性和经济实用性 相似文献
998.
999.
The problem of recovery of three-dimensional microstructural parameters from two-dimensional images is addressed in its inverse form. Three-dimensional inhomogeneous solids with known microstructures are generated virtually and images of their cross-sections are analyzed. Three different types of randomly oriented microcracks and microcracks having preferential orientation with some scatter. Somewhat unexpected result is that, in all the cases considered, three-dimensional defect densities are very close to average values of corresponding two-dimensional parameters. 相似文献
1000.