全文获取类型
收费全文 | 59641篇 |
免费 | 5448篇 |
国内免费 | 3091篇 |
专业分类
电工技术 | 4218篇 |
技术理论 | 5篇 |
综合类 | 4185篇 |
化学工业 | 9199篇 |
金属工艺 | 3537篇 |
机械仪表 | 3486篇 |
建筑科学 | 5207篇 |
矿业工程 | 1532篇 |
能源动力 | 1769篇 |
轻工业 | 3744篇 |
水利工程 | 1063篇 |
石油天然气 | 3303篇 |
武器工业 | 502篇 |
无线电 | 7320篇 |
一般工业技术 | 7332篇 |
冶金工业 | 2553篇 |
原子能技术 | 768篇 |
自动化技术 | 8457篇 |
出版年
2024年 | 312篇 |
2023年 | 1091篇 |
2022年 | 1770篇 |
2021年 | 2587篇 |
2020年 | 1843篇 |
2019年 | 1531篇 |
2018年 | 1727篇 |
2017年 | 1934篇 |
2016年 | 1718篇 |
2015年 | 2340篇 |
2014年 | 2845篇 |
2013年 | 3480篇 |
2012年 | 3758篇 |
2011年 | 4016篇 |
2010年 | 3616篇 |
2009年 | 3345篇 |
2008年 | 3480篇 |
2007年 | 3321篇 |
2006年 | 3339篇 |
2005年 | 2822篇 |
2004年 | 1999篇 |
2003年 | 1816篇 |
2002年 | 1907篇 |
2001年 | 1691篇 |
2000年 | 1471篇 |
1999年 | 1568篇 |
1998年 | 1159篇 |
1997年 | 1022篇 |
1996年 | 1002篇 |
1995年 | 813篇 |
1994年 | 670篇 |
1993年 | 494篇 |
1992年 | 439篇 |
1991年 | 323篇 |
1990年 | 216篇 |
1989年 | 186篇 |
1988年 | 161篇 |
1987年 | 101篇 |
1986年 | 66篇 |
1985年 | 56篇 |
1984年 | 34篇 |
1983年 | 23篇 |
1982年 | 32篇 |
1981年 | 18篇 |
1980年 | 20篇 |
1979年 | 8篇 |
1978年 | 2篇 |
1959年 | 2篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
1.
2.
Xue‐Yong Liu Xiao‐Bin Ding Zhao‐Hui Zheng Yu‐Xing Peng Albert S
C Chan C
W Yip Xin‐Ping Long 《Polymer International》2003,52(2):235-240
Amphiphilic magnetic microspheres ranging in diameter from 5 to 100 µm were prepared by dispersion copolymerization of styrene and poly(ethylene oxide) vinylbenzyl (PEO‐VB) macromonomer (MPEO) in the presence of Fe3O4 magnetic fluid. The effects of various polymerization parameters on the average particle size were systematically investigated. The average particle size was found to increase with increasing styrene concentration and initiator concentration. It also increased with decreasing stabilizer concentration and molecular weight of MPEO. The content of the hydroxyl groups localized in the microspheres ranged from 0.01 to 0.2 mmol g?1. © 2003 Society of Chemical Industry 相似文献
3.
In the present study, attempts are made to extend the application of the mechanical model for the fatigue crack initiation (FCI) and the FCI life formula of metallic notched elements in laboratory air to those in the corrosive environment. The test results and analysis of the corrosion FCI (CFCI) life of aluminum alloys and Ti---6A1---4V show that the expression of the CFCI life obtained by modifying the FCI life formula in laboratory air can give a good fit to the test results of the CFCI life. The salt water (3.5% NaCl) environment has no effects on the CFCI resistant coefficient compared with the FCI resistant coefficient in laboratory air. However, 3.5% NaCl environment greatly decreases the CFCI threshold of aluminum alloy, but has little effect on the CFCI threshold of Ti---6A1---4V. The loading frequency ranging from 1 Hz to 10 Hz has no appreciable effect on the CFCI life, and thus, the CFCI threshold of aluminum alloys investigated. Hence, the expression for the CFCI life of metallic notched elements proposed in this study is a better one, which reveals a correlation between the CFCI life and the governing parameters, such as, the geometry of the notched elements, the nominal stress range, the stress ratio, the tensile properties and the CFCI threshold. However, this new expression of the CFCI life needs to be verified by more test results. 相似文献
4.
5.
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
6.
7.
在第一部分综合讨论的基础上对甘三酯立体专一分析方法作了初步探讨。以液体油(菜油)及固体脂(猪脂)为基质,系统地研究了这一分析方法,取得了经验并补充了一些具体验证方法。分析液体油的结果与文献数据相一致,分析猪脂的结果欠佳,还存在一些问题需待进一步研究。 相似文献
8.
Generalized difference control of parallel streams temperatures 总被引:1,自引:0,他引:1
A furnace with multiple parallel passes and multiple burners is commonly seen in petroleum refineries. In order to maintain the furnace running in a safe, stable, and high-efficiency state it is necessary to control the outlet temperatures of the multiple passes to be the same. Due to the fact that the process of the oil heating in such furnace is nonlinear, multivariable, time varying, has serious coupling among passes, has frequent dynamic changes and a large time delay, traditional control methods have trouble in controlling these temperatures, and some advanced control methods, including predictive control, adaptive control, and robust control, are usually too complex for convenient use. In this paper, a control technique, called differences control technique (DsCT), is proposed to distribute the stream flowrates such that the stream temperatures are as identical as possible. The principle of the proposed technique is explained and demonstrated, and the results of its application to a real-life petroleum refinery furnace are also reported. The DsCT technique has the following advantages: it does not need complicated design procedures, the controller structure is simple, it is easy to apply, and it can be canonically applied to furnaces with different number of passes. 相似文献
9.
In this article, a new algorithm based on an artificial potential field and hierarchical cell decomposition technique is developed to solve the find-path problem for a mobile robot. The complete map of the workspace including obstacle locations is assumed to be known a priori. The basic cell structure used for decomposition is a hexagon. The artificial potential field is based on an attractive force from the goal position and repelling forces from the obstacles. Computer simulations of the algorithm for various obstacle scenarios are also presented. © 1994 John Wiley & Sons, Inc. 相似文献
10.
在各糖厂现用连续离心机原有生产实践基础上,对其机械吸震、加温、布温、机索结构、物料密封、机座等部件做了进一步改进,并取得可观的实效。 相似文献