全文获取类型
收费全文 | 25892篇 |
免费 | 2406篇 |
国内免费 | 1229篇 |
专业分类
电工技术 | 670篇 |
综合类 | 2419篇 |
化学工业 | 2519篇 |
金属工艺 | 978篇 |
机械仪表 | 2554篇 |
建筑科学 | 1782篇 |
矿业工程 | 693篇 |
能源动力 | 7061篇 |
轻工业 | 170篇 |
水利工程 | 245篇 |
石油天然气 | 1975篇 |
武器工业 | 643篇 |
无线电 | 1668篇 |
一般工业技术 | 1502篇 |
冶金工业 | 421篇 |
原子能技术 | 71篇 |
自动化技术 | 4156篇 |
出版年
2024年 | 51篇 |
2023年 | 259篇 |
2022年 | 544篇 |
2021年 | 605篇 |
2020年 | 600篇 |
2019年 | 532篇 |
2018年 | 511篇 |
2017年 | 666篇 |
2016年 | 643篇 |
2015年 | 732篇 |
2014年 | 1387篇 |
2013年 | 1224篇 |
2012年 | 1864篇 |
2011年 | 2184篇 |
2010年 | 1575篇 |
2009年 | 1680篇 |
2008年 | 1431篇 |
2007年 | 1909篇 |
2006年 | 1728篇 |
2005年 | 1449篇 |
2004年 | 1296篇 |
2003年 | 1175篇 |
2002年 | 999篇 |
2001年 | 860篇 |
2000年 | 727篇 |
1999年 | 569篇 |
1998年 | 469篇 |
1997年 | 385篇 |
1996年 | 297篇 |
1995年 | 248篇 |
1994年 | 183篇 |
1993年 | 161篇 |
1992年 | 139篇 |
1991年 | 109篇 |
1990年 | 72篇 |
1989年 | 95篇 |
1988年 | 64篇 |
1987年 | 38篇 |
1986年 | 9篇 |
1985年 | 14篇 |
1984年 | 16篇 |
1983年 | 5篇 |
1982年 | 13篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Phase behavior in liquid crystallization was studied for a series of liquid crystalline (LC) diblock copolymers consisting of rubbery amorphous and side-chain liquid crystalline components, poly(n-butyl acrylate) (PBA) and poly[11-(4′-cyanophenyl-4″-phenoxy)undecyl acrylate] (PLC), respectively, using a time-resolved small-angle X-ray scattering (SAXS) techniques, DSC and polarized optical microscopy (POM). The block copolymers used had three kinds of copolymer compositions, 44, 20 and 15 wt% of PLC compositions (BLC44, BLC20 and BLC15, respectively). BLC44 showed a smectic liquid crystalline structure. In the process of liquid crystallization for BLC44, the SAXS peak due to the microphase separation structure existing before liquid crystallization was changed continuously to be at a smaller angular side, and at almost the same time, a new peak appeared at a further smaller angular side and developed. The former peak disappeared with the development of liquid crystallization. The behavior of these SAXS peaks suggests that the microphase separation structure was changed discretely at the transition from isotropic to smectic and that two phases coexist in the early stage of the liquid crystallization. The coexistence of two peaks in the early stage of the liquid crystallization corresponded to the POM observation. In the isotropization process, coexistence of two phases was not observed. For BLC20 exhibiting a cylindrical structure in both isotropic and liquid crystalline states, the liquid crystalline structure was not smectic but probably nematic, and the spacing was changed continuously in liquid crystallization. No liquid crystallization was observed in SAXS, POM and DSC for BLC15. The orientation of smectic layers within lamellar domains was investigated using 2D-SAXS images. The smectic layer was aligned perpendicularly to the lamellar interface. 相似文献
52.
秦家屯油田位于松辽盆地南部东南隆起区十屋断陷东北部,属于非均质断块层状油藏,通过示踪剂监测技术可以了解区块内井间连通情况,判断油井见水、来水方向及油层水驱动用程度,结合油藏静态资料研究,指导油田开发,改善开发效果,达到了稳产的目的。 相似文献
53.
54.
Seog Geun Kang 《ETRI Journal》2006,28(2):235-238
In this letter, a block code that minimizes the peak‐to‐average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signals is proposed. It is shown that peak envelope power is invariant to cyclic shift and codeword inversion. The systematic encoding rule for the proposed code is composed of searching for a seed codeword, shifting the register elements, and determining codeword inversion. This eliminates the look‐up table for one‐to‐one correspondence between the source and the coded data. Computer simulation confirms that OFDM systems with the proposed code always have the minimum PAPR. 相似文献
55.
Windows平台下的汉字输入法机制及应用 总被引:1,自引:0,他引:1
作者在Windows平台下,通过对E码汉字输入法系统实现的软件研发过程,本质地认识了Windows平台下的汉字输入法系统的实现原理及其基本方法;本文对Windows IME系统的两个主要组成部分:转换引擎和界面模块以及二者之间的交互关系进行了深入的分析,并揭示了Windows平台下整个汉字输入法系统的底层运转机制。 相似文献
56.
随着VLSI工艺技术的发展和芯片规模的不断增加,尤其是在SOC设计中,原有的那种供电压焊块只能位于芯片边缘的确定益的模式已经不能够满足整个电路性能的需要。在很多情况下,依靠在电源线的拓扑结构确定后的线宽优化,还是无法保证在有限的布线资源下为电路提供可靠的高性能的供电需求。由此,出现了在芯片边缘上浮动放置压焊块及在芯片的顶部放置供电压焊块阵列的方法。文中提出了一种用于SOC设计中新的基于树型结构的浮动压焊块的电源/地线网络优化算法,经过MCNC电路实例测试后得到明显的优化结果。 相似文献
57.
58.
59.
60.
The literature provides little information on high-speed, high-normal-load, plain linear bearings, although the case for two rigid surfaces in relative linear motion can readily be solved by assuming squeeze action resistance. A new genus of internal combustion engines based on the Stiller-Smith mechanism incorporates connecting rods constrained by linear bearings, with the central normal load on the rod restricted by an oil film. A general analysis takes into account the bending of the rod, when the distributed oil film pressure resists the distributed load on the elastic rod. Design charts result that yield the dimensionless velocity at which the rod sinks in the oil as a function of the dimensionless load and the bearing clearance, and predict the deflection of the beam. The rod clearance history simulations for the Stiller-Smith engine compare favourably with computations for the rigid beam, confirming the analysis technique. 相似文献