全文获取类型
收费全文 | 241879篇 |
免费 | 20654篇 |
国内免费 | 11124篇 |
专业分类
电工技术 | 14967篇 |
技术理论 | 23篇 |
综合类 | 15943篇 |
化学工业 | 39602篇 |
金属工艺 | 13133篇 |
机械仪表 | 14825篇 |
建筑科学 | 18742篇 |
矿业工程 | 7125篇 |
能源动力 | 7001篇 |
轻工业 | 17334篇 |
水利工程 | 4497篇 |
石油天然气 | 14014篇 |
武器工业 | 1892篇 |
无线电 | 28918篇 |
一般工业技术 | 28922篇 |
冶金工业 | 11941篇 |
原子能技术 | 2569篇 |
自动化技术 | 32209篇 |
出版年
2024年 | 1172篇 |
2023年 | 4382篇 |
2022年 | 8172篇 |
2021年 | 11012篇 |
2020年 | 8323篇 |
2019年 | 6581篇 |
2018年 | 7481篇 |
2017年 | 8265篇 |
2016年 | 7565篇 |
2015年 | 9952篇 |
2014年 | 12413篇 |
2013年 | 14751篇 |
2012年 | 16134篇 |
2011年 | 17180篇 |
2010年 | 14559篇 |
2009年 | 13780篇 |
2008年 | 13299篇 |
2007年 | 12320篇 |
2006年 | 12335篇 |
2005年 | 10624篇 |
2004年 | 7288篇 |
2003年 | 6211篇 |
2002年 | 5610篇 |
2001年 | 5067篇 |
2000年 | 5095篇 |
1999年 | 6048篇 |
1998年 | 5033篇 |
1997年 | 4234篇 |
1996年 | 4021篇 |
1995年 | 3297篇 |
1994年 | 2748篇 |
1993年 | 1943篇 |
1992年 | 1561篇 |
1991年 | 1158篇 |
1990年 | 896篇 |
1989年 | 764篇 |
1988年 | 576篇 |
1987年 | 397篇 |
1986年 | 314篇 |
1985年 | 208篇 |
1984年 | 174篇 |
1983年 | 126篇 |
1982年 | 132篇 |
1981年 | 100篇 |
1980年 | 95篇 |
1979年 | 42篇 |
1978年 | 31篇 |
1977年 | 32篇 |
1976年 | 39篇 |
1974年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
含H_2S井完井液对井下金属管串具有腐蚀性。采用锌基或铁基螯合物除硫剂及咪唑啉缓蚀剂可有效地防止这种腐蚀的发生。本文对H_2S的腐蚀、除硫剂和缓蚀剂产品及其对产层的损害作了介绍与探讨。 相似文献
62.
The effect of the atomic mobility on a film surface has been studied by using a three-dimensional atomistic thin-film deposition model which simulates three-dimensional thin-film images, surface profiles and cross-sectional area pictures. In addition, quantitative results of surface RMS roughness, average film thickness, atomic coordination number and its distribution, and solid fraction of the deposited thin films, were obtained from the simulations. When the film surface mobility increased from 0.3 to 3.0, RMS roughness decreased from 6.5 to 1.1, solid fraction increased from 0.27 to 0.56 and average film thickness decreased from 40 to 28, due to the reduction of the voids within the film. The full-width half magnitude of the atomic coordination distribution became narrower indicating the increased degree of crystallization. With increase in surface mobility crossing the boundary to 1.5, the film evolved from a porous or loose columnar structure with voids, to a densely packed fibrous grain structure which can be categorized by the zone structure models. 相似文献
63.
We propose a new service for digital mobile communication systems. The service enables two or more users to hold a secure conference. Two requirements must be considered: privacy and authentication. Privacy involves ensuring that an eavesdropper cannot intercept the conversations of the parties holding the conference. Authentication involves ensuring that service is not obtained fraudulently in order to avoid usage charges. We present two new conference key distribution schemes for digital mobile communication systems. In these schemes, a group of users can generate a common secret keg over a public channel so that they may hold a secure conference 相似文献
64.
65.
66.
用膨胀法对28Cr2Mo1VA钢测定了变速冷却过冷奥氏体转变动力学曲线,结果表明,先慢冷后快冷,珠光体、贝氏体转变滞后;反之,转变超前。并提出用图解计算法求转变点,结果与实验相符合。 相似文献
67.
Kuo-Kai Shyu Chiu-Keng Lai Yao-Wen Tsai Ding-I Yang 《Industrial Electronics, IEEE Transactions on》2002,49(3):558-565
A robust controller which is designed by employing variable-structure control and linear-quadratic method is presented for a permanent-magnet synchronous motor (PMSM) position control system. It is to achieve accurate control performance in the presence of plant parameter variation and load disturbance. In addition, it possesses the design flexibility of the conventional state feedback control. It is applied to the position control of a PMSM. Simulation and experimental results show that the proposed approach gives a better position response and is robust to parameter variations and load disturbance 相似文献
68.
69.
P. Kristiansson C. M. Nilsson H. Busk L. Malmqvist M. Elfman K. G. Malmqvist J. Pallon K. A. Sj land R. J. Utui C. Yang 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》1997,130(1-4):303-307
A technique for measuring optical dot gain, i.e. the relative difference between the actual screen dot and the optically perceived one, is presented. By combining measurements from the non-optical nuclear microprobe with data from image analyzing technique the optical dot gain can be determined. The procedure to reach pixel by pixel correlation on a micrometer scale is discussed. In the newsprint sample studied in this investigation a typical optical dot gain between 15 and 20% was deduced. The variation in the optical dot gain was correlated with other characteristic parameters of the print and newsprint and especially a positive correlation to the mass density of the newsprint was observed. 相似文献
70.
提出了一种新的铝液夹杂物快速检测方法。导出了该法的检测原理方程。分析并试验研究了影响检测重复性和分辨率的因素。试验选择了较好的检测参数,并获得了较好的检测结果。 相似文献