全文获取类型
收费全文 | 667683篇 |
免费 | 103058篇 |
国内免费 | 66081篇 |
专业分类
电工技术 | 57664篇 |
技术理论 | 50篇 |
综合类 | 59317篇 |
化学工业 | 100025篇 |
金属工艺 | 50843篇 |
机械仪表 | 38316篇 |
建筑科学 | 49708篇 |
矿业工程 | 28677篇 |
能源动力 | 21154篇 |
轻工业 | 58115篇 |
水利工程 | 17601篇 |
石油天然气 | 39227篇 |
武器工业 | 8031篇 |
无线电 | 79890篇 |
一般工业技术 | 78889篇 |
冶金工业 | 29980篇 |
原子能技术 | 6872篇 |
自动化技术 | 112463篇 |
出版年
2024年 | 4537篇 |
2023年 | 11539篇 |
2022年 | 19253篇 |
2021年 | 25219篇 |
2020年 | 22847篇 |
2019年 | 27787篇 |
2018年 | 30685篇 |
2017年 | 33537篇 |
2016年 | 31992篇 |
2015年 | 37047篇 |
2014年 | 41476篇 |
2013年 | 45432篇 |
2012年 | 48720篇 |
2011年 | 48973篇 |
2010年 | 44100篇 |
2009年 | 39747篇 |
2008年 | 38038篇 |
2007年 | 36044篇 |
2006年 | 34274篇 |
2005年 | 29795篇 |
2004年 | 24426篇 |
2003年 | 20669篇 |
2002年 | 19687篇 |
2001年 | 17413篇 |
2000年 | 16048篇 |
1999年 | 14992篇 |
1998年 | 11653篇 |
1997年 | 10037篇 |
1996年 | 9445篇 |
1995年 | 8384篇 |
1994年 | 6806篇 |
1993年 | 5300篇 |
1992年 | 4673篇 |
1991年 | 3494篇 |
1990年 | 2725篇 |
1989年 | 2426篇 |
1988年 | 1899篇 |
1987年 | 867篇 |
1986年 | 709篇 |
1985年 | 470篇 |
1984年 | 334篇 |
1983年 | 271篇 |
1982年 | 276篇 |
1981年 | 234篇 |
1980年 | 216篇 |
1976年 | 255篇 |
1975年 | 209篇 |
1972年 | 243篇 |
1971年 | 134篇 |
1960年 | 209篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
This investigation focuses on the correlation between the crystallographic orientation of grains with respect to magnetic
properties in Co-Cr films. Based on a distribution measured for the (0002) crystallographic pole densities, modified formulae
describing the texture were used to calculate the coercivity Hc, the squareness ratio Rs (Mr⊥/TMs) and the anisotropy field
Ha for Co-Cr films. In general, calculated values for the coercive force He agreed well with the measured values. The calculated
Rs⊥. values were much larger than the measured ones, however, indicating that the influence of the demagnetizing field and
the magnetostriction on the orientation of the magnetization cannot be neglected.
On leave from Institute of Computing Technology, Academia Sinica, P.O.Box 2704-6, Beijing, P.R. China. 相似文献
22.
Code-division multiple-access (CDMA) implemented with direct-sequence spread spectrum (DS/SS) signaling is a promising multiplexing technique for cellular telecommunications services. The efficiency of a direct-sequence spread-spectrum code-division multiple-access (DS-CDMA) system depends heavily on the shape of the spectrum of the spread signal. Maximum efficiency is obtained with an ideal brick-wall bandpass spectrum. There are two approaches toward achieving such a spectrum. One is to use a simple spreader that produces a broad spectrum and then follow it with a precise, high order filter to band limit the spectrum. A second approach, which is the approach taken in this paper, is to use a spreader that produces a spectrum close to the ideal spectrum and then employ a simple filter to control the out-of-band power. The proposed spreader/despreader is based on a simple hybrid function and can be easily implemented. An analysis provides a compact expression for the signal-to-noise ratio (SNR) of a RAKE receiver. The expression includes the effects of baseband, intermediate frequency (IF) and RF filtering as well as the effects of the spectral densities of the spreading/despreading functions. The analysis shows that the proposed spreader/despreader yields superior performance over a conventional pseudo noise (PN) spreading/despreading mechanism 相似文献
23.
Network fault identification is an important network management function, which is closely related to fault management and has an impact on other network management functions such as configuration management, and performance management. This paper investigates fault surveillance and fault identification mechanisms for a transparent optical network in which data travels optically from the source node to the destination node without going through any optical-to-electrical (O/E) or electrical-to-optical (E/O) conversion. Mechanisms and algorithms are proposed to detect and isolate faults such as fiber cuts, laser, receiver, or router failures. These mechanisms allow nonintrusive device monitoring without requiring any prior knowledge of the actual protocols being used in the data transmission 相似文献
24.
This article deals with the kinetics of two-step anionic polymerization by way of a non-steady state method. Several molecular parameters can be evaluated using the formulae developed. A bimodal molecular weight distribution function for the resulting polymer is derived from the set of kinetic differential equations, which is in agreement with the experimental data reported. 相似文献
25.
26.
27.
本文介绍了Windows环境下基于消息的DDE和基于动态链接库的DDEML的区别,并详细叙述了如何使用DDEML编制Windows应用程序。 相似文献
28.
Different hierarchical models in pattern analysis and recognition are proposed, based on occurrence probability of patterns. As an important application of recognizing handprinted characters, three typical kinds of hierarchical models such asM
89-89,M
89-36 andM
36-36 have been presented, accompanied by the computer algorithms for computing recognition rates of pattern parts. Moreover, a comparative study of their recognition rates has been conducted theoretically; and numerical experiments have been carried out to verify the analytical conclusions made. Various hierarchical models deliberated in this paper can provide users more or better choices of pattern models in practical application, and lead to a uniform computational scheme (or code). The recognition rates of parts can be improved remarkably by a suitable hierarchical model. For the modelM
89-36 in which case some of the Canadian standard handprinted characters have multiple occurrence probabilities, the total mean recognition rates of the given sample may reach 120% of that by the model proposed by Li et al., and 156% of that obtained from the subjective experiments reported by Suen. 相似文献
29.
中国古典园林三维造型研究 总被引:1,自引:0,他引:1
论述了采用层次结构化及参数化三维造型方法,建立一个以造型函数库为核心,从而构造各类、各级园林景观构件表面模型的方法和过程。对于某些非建筑类的园林配景构件,采用了Fractal方法进行造型。 相似文献
30.
本文提出新型布线算法,集李氏迷宫法与线搜索法的长处为一体,以饱和带法进行动态排序,以线搜索法确定借孔位置,然后用李氏法进行单层布线,获得最佳路径,从而达到线型好,布通率高的效果。 相似文献