全文获取类型
收费全文 | 32446篇 |
免费 | 3486篇 |
国内免费 | 2056篇 |
专业分类
电工技术 | 13257篇 |
综合类 | 2293篇 |
化学工业 | 2576篇 |
金属工艺 | 2973篇 |
机械仪表 | 1612篇 |
建筑科学 | 1031篇 |
矿业工程 | 707篇 |
能源动力 | 1178篇 |
轻工业 | 411篇 |
水利工程 | 693篇 |
石油天然气 | 446篇 |
武器工业 | 201篇 |
无线电 | 4307篇 |
一般工业技术 | 3004篇 |
冶金工业 | 1142篇 |
原子能技术 | 549篇 |
自动化技术 | 1608篇 |
出版年
2024年 | 127篇 |
2023年 | 423篇 |
2022年 | 658篇 |
2021年 | 902篇 |
2020年 | 954篇 |
2019年 | 797篇 |
2018年 | 784篇 |
2017年 | 1159篇 |
2016年 | 1196篇 |
2015年 | 1356篇 |
2014年 | 2022篇 |
2013年 | 1866篇 |
2012年 | 2326篇 |
2011年 | 2753篇 |
2010年 | 2039篇 |
2009年 | 2274篇 |
2008年 | 2077篇 |
2007年 | 2532篇 |
2006年 | 2155篇 |
2005年 | 1688篇 |
2004年 | 1391篇 |
2003年 | 1131篇 |
2002年 | 889篇 |
2001年 | 829篇 |
2000年 | 749篇 |
1999年 | 589篇 |
1998年 | 450篇 |
1997年 | 364篇 |
1996年 | 317篇 |
1995年 | 277篇 |
1994年 | 207篇 |
1993年 | 157篇 |
1992年 | 132篇 |
1991年 | 96篇 |
1990年 | 75篇 |
1989年 | 66篇 |
1988年 | 40篇 |
1987年 | 37篇 |
1986年 | 20篇 |
1985年 | 15篇 |
1984年 | 21篇 |
1983年 | 13篇 |
1982年 | 10篇 |
1981年 | 11篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1965年 | 1篇 |
1962年 | 1篇 |
1959年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 542 毫秒
41.
Incorporation of silicon species from an alloy substrate into anodic titania is shown to stabilise the structure of the film, facilitating investigation of the ionic transport processes in amorphous titania grown at high efficiency. Thus, an amorphous anodic film developed on a sputtering-deposited Ti-6 at.%Si alloy formed to 100 V in phosphoric acid electrolyte in contrast to a partially crystalline film developed on relatively pure titanium at <20 V. Silicon species, which are immobile and act as marker species in the growing film, are present in the inner 58% of the film thickness. Evidently, the film material forms simultaneously at the film/electrolyte and alloy/film interfaces by co-operative transport of cations and anions, as is usual in amorphous anodic oxides. The phosphate anions incorporated from the electrolyte migrate inward at 0.34 times the rate of O2− ions and hence are present in the outer 62% of the film thickness. 相似文献
42.
43.
M. Polák M. Majoro F. Hanic J. Pitel M. Kedrová P. Kottman J. Talapa L. Vencel 《Journal of Superconductivity》1989,2(2):219-233
A method for contactless measurement of the shielding critical current density and its dependence on the external magnetic field is described and analyzed. The obtained values are compared with those measured resistively on two different samples. It is shown that the shielding critical current densityJ
cs
and the intergranular transport current densityJ
cr
are identical if the measurement conditions are similar. A degradation ofJ
cs
measured in the external field with AC ripple has been observed. 相似文献
44.
针对一种新型的难加工钛合金材料β21s,进行了刀具磨损试验和铣削力的测量试验,对材料的切削加工性进行评价,并且给出优选结果,为实际生产提供参考。 相似文献
45.
46.
采用现代高频功率变换技术的有源功率因数校正(Power Factor Corrector,PFC)技术是解决高频开关变换器谐波污染的有效手段。与传统的PFC电路相比,有源PFC电路的输入电流接近正弦波且与输与电压同相位,能有效抑制电流波形畸变和谐波,因此避免了对同一电网设施的干扰。在PFC电路中,Boost变换器是研究和应用得最多的一种变换器。本文着重分析了Boost电路在不连续导电模式状态下,PFC电路的临界条件,对实际电路结构的设计有很好的指导意义。 相似文献
47.
48.
49.
I.H. Song 《Thin solid films》2007,515(19):7598-7602
This paper is a report on the effect of a single perpendicular grain boundary on the hot-carrier and high current stability in high performance polycrystalline silicon (poly-Si) thin film transistors (TFTs). Under a hot carrier stress condition (Vg = Vth + 1 V, Vd = 12 V), the poly-Si TFT with a single grain boundary is superior to the poly-Si without any grain boundary because of the smaller free carriers available for electric conduction. The shift of transconductance in poly-Si TFT with a single grain boundary is less than 5% after hot carrier stress during a period of 1000 s. The shift of transconductance is about 25% in the case of the poly-Si TFTs without a grain boundary in the channel. On high current stress, the poly-Si TFT without the grain boundary is less degraded than the poly-Si TFT with the grain boundary because the concentrated electric field near the drain junction is lower. 相似文献
50.
D.J. Bekers S.J.L. van Eijndhoven A.A.F. van de Ven 《Journal of Engineering Mathematics》2004,49(4):373-390
A long thin conducting stripline embedded in a dielectric and centered between two large conducting plates, i.e., the stripline environment, is considered. The stripline is modeled as infinitely long, infinitely thin, and perfectly conducting by first considering a stripline of finite length, thickness, and conductivity in a dielectric layer. Starting from Maxwell's equations and assuming that the current on the stripline is a propagating wave in length direction, asymptotic expressions for the fields inside and in the neighbourhood of the stripline are deduced. These expressions are used to model the stripline in the stripline environment, which leads to a boundary-value problem for the electric potential. This problem is solved by two different approaches, leading to integral equations for the current and for an auxiliary function describing the electric potential. A relation between the current and the auxiliary function is deduced, which is used to obtain asymptotic expressions for current and impedance. Results are compared with a numerical solution of the integral equation for the current and with results in literature. 相似文献