全文获取类型
收费全文 | 91984篇 |
免费 | 16822篇 |
国内免费 | 11143篇 |
专业分类
电工技术 | 11318篇 |
技术理论 | 6篇 |
综合类 | 11491篇 |
化学工业 | 4902篇 |
金属工艺 | 2607篇 |
机械仪表 | 6338篇 |
建筑科学 | 2718篇 |
矿业工程 | 1676篇 |
能源动力 | 3850篇 |
轻工业 | 1565篇 |
水利工程 | 2139篇 |
石油天然气 | 2746篇 |
武器工业 | 1397篇 |
无线电 | 14819篇 |
一般工业技术 | 7083篇 |
冶金工业 | 1370篇 |
原子能技术 | 439篇 |
自动化技术 | 43485篇 |
出版年
2024年 | 717篇 |
2023年 | 2226篇 |
2022年 | 3778篇 |
2021年 | 3985篇 |
2020年 | 4313篇 |
2019年 | 3635篇 |
2018年 | 3501篇 |
2017年 | 3974篇 |
2016年 | 4277篇 |
2015年 | 4867篇 |
2014年 | 6306篇 |
2013年 | 6132篇 |
2012年 | 7661篇 |
2011年 | 7998篇 |
2010年 | 6315篇 |
2009年 | 6420篇 |
2008年 | 6603篇 |
2007年 | 7144篇 |
2006年 | 5830篇 |
2005年 | 4751篇 |
2004年 | 3824篇 |
2003年 | 3155篇 |
2002年 | 2418篇 |
2001年 | 1864篇 |
2000年 | 1655篇 |
1999年 | 1294篇 |
1998年 | 1049篇 |
1997年 | 833篇 |
1996年 | 684篇 |
1995年 | 487篇 |
1994年 | 450篇 |
1993年 | 309篇 |
1992年 | 299篇 |
1991年 | 189篇 |
1990年 | 194篇 |
1989年 | 159篇 |
1988年 | 114篇 |
1987年 | 65篇 |
1986年 | 73篇 |
1985年 | 65篇 |
1984年 | 42篇 |
1983年 | 40篇 |
1982年 | 52篇 |
1981年 | 28篇 |
1980年 | 26篇 |
1979年 | 19篇 |
1978年 | 14篇 |
1977年 | 15篇 |
1964年 | 11篇 |
1959年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
目前,基于因素空间理论的背景基提取算法计算过程复杂,初始化必须依赖各因素极值,基点数量提取冗余等原因,未能在应用中取得很好效果。为此,结合内点判别法和知识可继承、可扩展的思想,提出一种计算简单、初始化独立、基点数量小的改进的背景基提取算法。然后,利用改进的背景基提取算法构造出一种全新的数据分类算法-基点分类算法,基点分类算法以提取每一类样本的背景基为预测模型,再通过新定义的λ-背景基,优化预测模型。数值实验表明:基点分类算法原理简单、构造难度小、分类模型泛化能力强,预测能力准确率高,同时严格的模型限定区域又能为识别新类别提供新方法。 相似文献
93.
《International Journal of Hydrogen Energy》2021,46(75):37333-37339
Water electrolysis is an efficient approach for high-purity hydrogen production. However, the anodic sluggish oxygen evolution reaction (OER) always needs high overpotential and thus brings about superfluous electricity cost of water electrolysis. Therefore, exploiting highly efficient OER electrocatalysts with small overpotential especially at high current density will undoubtedly boost the development of industrial water electrolysis. Herein, we used a simple hydrothermal method to prepare a novel FeOOH–CoS nanocomposite on nickel foam (NF). The as-prepared FeOOH–CoS/NF catalyst displays an excellent OER performance with extremely low overpotentials of 306 and 329 mV at 500 and 1000 mA cm−2 in 1.0 M KOH, respectively. In addition, the FeOOH–CoS/NF catalyst can maintain excellent catalytic stability for more than 50 h, and the OER catalytic activity shows almost no attenuation no matter after 1000 repeated CV cycles or 50 h of stability test. The high catalytic activity and stability have exceeded most non-noble metal electrocatalysts reported in literature, which makes the FeOOH–CoS/NF composite catalyst have promising applications in the industrial water electrolysis. 相似文献
94.
95.
An effective coding approach for multiobjective integrated resource selection and operation sequences problem 总被引:3,自引:1,他引:2
In this paper, we consider an integrated Resource Selection and Operation Sequences (iRS/OS) problem in Intelligent Manufacturing
System (IMS). Several kinds of objectives are taken into account, in which the makespan for orders should be minimized; workloads
among machine tools should be balanced; the total transition times between machines in a local plant should also be minimized.
To solve this multiobjective iRS/OS model, a new two vectors-based coding approach has been proposed to improve the efficiency
by designing a chromosome containing two kinds of information, i.e., operation sequences and machine selection. Using such
kind of chromosome, we adapt multistage operation-based Genetic Algorithm (moGA) to find the Pareto optimal solutions. Moreover
a special technique called left-shift hillclimber has been used as one kind of local search to improve the efficiency of our
algorithm. Finally, the experimental results of several iRS/OS problems indicate that our proposed approach can obtain best
solutions. Further more comparing with previous approaches, moGA performs better for finding Pareto solutions.
Received: May 2005/Accepted: December 2005 相似文献
96.
We extend the definition of the classical Jacobi polynomials withindexes α, β>−1 to allow α and/or β to be negative integers. We show that the generalized Jacobi polynomials, with indexes corresponding to the number of boundary conditions in a given partial differential equation, are the natural basis functions for the spectral approximation of this partial differential equation. Moreover, the use of generalized Jacobi polynomials leads to much simplified analysis, more precise error estimates and well conditioned algorithms.Mathematics subject classification 1991. 65N35, 65N22, 65F05, 35J05 相似文献
97.
Feng Juanni Guo Xuefeng Xu Chunjie Zhang Zhongming 《中国稀土学报(英文版)》2006,24(1):120-120
As-east mierostruetures and their distribution of Mg-Zn-Y ternary alloy with high magnesium, low zinc and yttrium were examined using Nikon Epiphot optical microscopy (OM), RigakuD/max-3C X- ray diffraetion (XRD), and JEOL JSM-6700F scanning electron microscopy (SEM) equipped with an energydispersive X-ray spectroscopy (EDS). In the as-east mierostructures, Yttrium and zinc tend to segregate at grain boundaries, 相似文献
98.
马钢二烧结配料计算机控制系统 总被引:1,自引:0,他引:1
阐明了马钢二烧结配科计算机控制系统的目的、控制形式、控制原理;根据烧结配料控制对象的特点对信号采样和控制算法进行了探讨;提供了系统的主要硬件结构,软件功能和程序框图。 相似文献
99.
Namyong Kim 《ETRI Journal》2006,28(2):155-161
In this paper, we introduce an escalator (ESC) algorithm based on the least squares (LS) criterion. The proposed algorithm is relatively insensitive to the eigenvalue spread ratio (ESR) of an input signal and has a faster convergence speed than the conventional ESC algorithms. This algorithm exploits the fast adaptation ability of least squares methods and the orthogonalization property of the ESC structure. From the simulation results, the proposed algorithm shows superior convergence performance. 相似文献
100.
文章介绍了一种新型的短波跳频通信技术——差分跳频,分析了差分跳频技术区别于常规跳频技术的主要特点。针对按序列检测的信号接收方法,对差分跳频通信系统在AWGN信道下的性能进行了理论分析,同时做出相应的计算机仿真,证实了差分跳频通信技术和按序列检测方法的结合,使通信系统在AWGN信道下的性能得到了比较显著的提升。 相似文献