全文获取类型
收费全文 | 106731篇 |
免费 | 9940篇 |
国内免费 | 5847篇 |
专业分类
电工技术 | 7345篇 |
技术理论 | 9篇 |
综合类 | 9548篇 |
化学工业 | 16496篇 |
金属工艺 | 6161篇 |
机械仪表 | 6778篇 |
建筑科学 | 8248篇 |
矿业工程 | 2894篇 |
能源动力 | 2973篇 |
轻工业 | 10789篇 |
水利工程 | 2149篇 |
石油天然气 | 5291篇 |
武器工业 | 1062篇 |
无线电 | 11370篇 |
一般工业技术 | 11149篇 |
冶金工业 | 3996篇 |
原子能技术 | 1151篇 |
自动化技术 | 15109篇 |
出版年
2024年 | 506篇 |
2023年 | 1783篇 |
2022年 | 3543篇 |
2021年 | 4566篇 |
2020年 | 3478篇 |
2019年 | 2735篇 |
2018年 | 2968篇 |
2017年 | 3490篇 |
2016年 | 3045篇 |
2015年 | 4498篇 |
2014年 | 5734篇 |
2013年 | 6568篇 |
2012年 | 7738篇 |
2011年 | 8451篇 |
2010年 | 7599篇 |
2009年 | 7170篇 |
2008年 | 7177篇 |
2007年 | 6696篇 |
2006年 | 6372篇 |
2005年 | 5060篇 |
2004年 | 3668篇 |
2003年 | 3171篇 |
2002年 | 3347篇 |
2001年 | 2799篇 |
2000年 | 2241篇 |
1999年 | 1881篇 |
1998年 | 1353篇 |
1997年 | 1033篇 |
1996年 | 921篇 |
1995年 | 687篇 |
1994年 | 559篇 |
1993年 | 386篇 |
1992年 | 328篇 |
1991年 | 245篇 |
1990年 | 164篇 |
1989年 | 145篇 |
1988年 | 92篇 |
1987年 | 77篇 |
1986年 | 59篇 |
1985年 | 30篇 |
1984年 | 18篇 |
1983年 | 24篇 |
1982年 | 24篇 |
1981年 | 24篇 |
1980年 | 32篇 |
1979年 | 9篇 |
1965年 | 2篇 |
1960年 | 2篇 |
1959年 | 8篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
镁钴铝类水滑石催化合成安息香甲醚 总被引:1,自引:0,他引:1
采用共沉淀法制备了镁钴铝类水滑石化合物(MgCoAl-HTLcs),并用 X 射线衍射、扫描电子显微镜、NH_3程序升温脱附等方法对 MgCoAl-HTLcs 进行了表征,并以 MgCoAl-HTLcs 为催化剂催化苯甲醛与甲醇反应合成安息香甲醚,研究了n(Mg):n(Co):n(Al)、催化剂用量、原料配比、反应温度、反应时间对合成反应的影响。表征结果显示,MgCoAl-HTLcs 的晶相完整,表面主要为弱酸、弱碱性。催化合成安息香甲醚的适宜条件为:MgCoAl-HTLcs 催化剂用量0.10 g(约为原料总质量的0.23%),n(Mg):n(Co):n(Al)=0.4:1.6:1.0,V(苯甲醛):V(甲醇)=3:50,反应温度50℃,反应时间150 min。在此条件下,苯甲醛的平衡转化率达77.49%,安息香甲醚选择性接近100%。为洁净合成安息香甲醚开辟了一条新的途径。 相似文献
43.
44.
Bingyong Yan Zuohua Tian Songjiao Shi 《International Journal of Electrical Power & Energy Systems》2008,30(5):343-360
In this paper, we propose a novel distributed robust fault detection and identification (RFDI) scheme for a class of nonlinear systems. Firstly, a detection and identification estimator—robust fault tracking approximator (RFTA) is designed for online health monitoring. A novel feature of the RFTA is that it can simultaneously detect and accurately identify the shape and magnitude of the fault and disturbance. Moreover, it takes less online training time compared with the traditional neural network based fault diagnosis schemes. For some distributed systems, a network of distributed estimators is constructed where the RFTA is embedded into each estimator. Then we use consensus filter to filter the outputs of each estimator. One of the most important merits of the consensus filter is that its outputs can dramatically improve the accuracy of fault detection and identification. Next, the stability of the distributed RFDI scheme is rigorously investigated. Finally, two numerical examples are given to illustrate the feasibility and effectiveness of the proposed approach. 相似文献
45.
46.
47.
Fixed point theorem-based iterative learning control for LTV systems with input singularity 总被引:1,自引:0,他引:1
In this paper, we address a challenging and open problem: how to design a suitable iterative learning control (ILC) system in the presence of input singularity, which is incurred by the singularities of the system direct feed-through term. Considering two typical types of input singularities, we first revise the ILC operators accordingly by adding a forgetting factor and incorporating a time-varying learning gain, in the sequel guarantee ILC operators to be contractible. Next, using the Banach fixed-point theorem, we demonstrate that the output sequence can either enter and remains ultimately in a designated neighborhood of the target trajectory, or is bounded by a class K function. Finally, an illustrative example is presented. 相似文献
48.
49.
50.
Summary Novel hyperbranched copolymers were successfully synthesized by the controlled charge transfer complex inimer and living radical copolymerization of p-(chloromethyl)styrene (PCMS) and acrylonitrile (AN). The resulting copolymers were characterized by SEC, NMR, FTIR, DSC and elemental analysis etc.. The influences of reaction conditions, such as the polymerization temperature, the catalyst (CuBr) concentration and the monomer ratio, on the resulting copolymers were investigated in detail. The monomer reactivity ratios were evaluated to be rPCMS=0.937 and rAN=0.088 respectively by the Fineman-Ross method. The higher are the polymerization temperature and the ratio of catalyst to monomer, the higher is the branching degree of the resulting copolymer. When the amount of monomer AN was used in excess than that of the monomer PCMS in the raw feed, the hyperbranched predominantly alternating copolymers HP[PCMS-co-AN] could be obtained. These hyperbranched copolymers were successfully used as functional macroinitiators to synthesize the star-shaped poly(PCMS-co-AN)/poly(MMA) block copolymers. 相似文献