全文获取类型
收费全文 | 26070篇 |
免费 | 1983篇 |
国内免费 | 856篇 |
专业分类
电工技术 | 2479篇 |
综合类 | 2492篇 |
化学工业 | 2467篇 |
金属工艺 | 1034篇 |
机械仪表 | 1566篇 |
建筑科学 | 2512篇 |
矿业工程 | 1453篇 |
能源动力 | 801篇 |
轻工业 | 1625篇 |
水利工程 | 886篇 |
石油天然气 | 1947篇 |
武器工业 | 136篇 |
无线电 | 1841篇 |
一般工业技术 | 1588篇 |
冶金工业 | 1349篇 |
原子能技术 | 524篇 |
自动化技术 | 4209篇 |
出版年
2025年 | 128篇 |
2024年 | 388篇 |
2023年 | 404篇 |
2022年 | 701篇 |
2021年 | 761篇 |
2020年 | 794篇 |
2019年 | 729篇 |
2018年 | 674篇 |
2017年 | 737篇 |
2016年 | 819篇 |
2015年 | 891篇 |
2014年 | 1589篇 |
2013年 | 1644篇 |
2012年 | 1852篇 |
2011年 | 1764篇 |
2010年 | 1320篇 |
2009年 | 1338篇 |
2008年 | 1240篇 |
2007年 | 1502篇 |
2006年 | 1387篇 |
2005年 | 1148篇 |
2004年 | 1082篇 |
2003年 | 986篇 |
2002年 | 875篇 |
2001年 | 790篇 |
2000年 | 614篇 |
1999年 | 526篇 |
1998年 | 393篇 |
1997年 | 318篇 |
1996年 | 309篇 |
1995年 | 271篇 |
1994年 | 212篇 |
1993年 | 161篇 |
1992年 | 118篇 |
1991年 | 114篇 |
1990年 | 77篇 |
1989年 | 73篇 |
1988年 | 44篇 |
1987年 | 34篇 |
1986年 | 13篇 |
1985年 | 5篇 |
1984年 | 13篇 |
1983年 | 16篇 |
1982年 | 11篇 |
1981年 | 11篇 |
1980年 | 3篇 |
1979年 | 6篇 |
1977年 | 3篇 |
1959年 | 2篇 |
1955年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
本文运用一典型的人工神经网络模型─“反向传播”模型,对高氧化态(Ⅱ─Ⅳ)三核金属簇合物的构型分布进行了分析,得到了较好的分类、预报结果为化合物结构分析提供了新的工具。 相似文献
2.
This paper presents a highly stable steady-state torque control system with a feedback of a secondary current signal. The torque control system is constructed with a feedback of the secondary current (I2) signal using a quick response magnetic-field sensor constructed with an amorphous core multivibrator bridge, which can solve the secondary resistance change problem for temperature variation in the IM. Moreover, we added a state feedback to the system to improve the response speed for the unit step function of a torque order. The I2 sensor method has advantages especially at a low-speed range, in which conventional method using an integrator shows control errors. 相似文献
3.
William Kent 《Computer Standards & Interfaces》1991,13(1-3):201-206
OSQL is the object-oriented database language developed for the Iris object-oriented database management system at Hewlett-Packard Laboratories. Its three fundamental constructs are objects, types, and functions. This paper provides an overview of the underlying concepts and some important features of OSQL. 相似文献
4.
Akira Ishizaki Kazuhiko Takasaki Shoji Shimomura Kouichi Masaki Kanji Kitazawa 《Electrical Engineering in Japan》1996,116(5):128-137
Although brushless resolvers have been used widely as angular position transducers, they are expensive due to their intricate construction, involving a rotary transformer to supply the exciting coils wound on the rotor poles with the current. It is shown theoretically in this paper that the resolver without rotary transformer or brushes can be realized by simple construction, which consists of the stator core with both 4-poles exciting windings and 2-poles output ones and the rotor core carrying no windings. In this resolver the rotor core has minimum gap at one side and a maximum gap at another side of the diameter. It is characterized by an outer surface form that makes the fluctuation part of gap permeance very in proportion to cos θ, where θ represents the angular position of a point in the air gap with respect to the origin on the rotor, the point of minimum air gap. The method determining the rotor form to embody the aforementioned gap permeance variation is also shown. It has been confirmed not only by simulation but also experiment that the 2-phase output voltages of a model designed based on the theory have sinusoidal waveforms with very small harmonic contents. Moreover, the rotor position detected by processing the output voltages through the conventional resolver/digital converter was within acceptable engineering accuracy. 相似文献
5.
针对"网络信息安全"教材建设的现状进行分析,提出建设基于工作流导向的任务式实训模式教材的必要性,并从教材的指导思想、整体结构、内容结构及其特色等方面进行了阐述。实践证明,该新型教材的建设和使用能够激发学生学习网络安全知识的兴趣,提升动手能力,有效提高教学质量和效率。 相似文献
6.
Titanium in the rapidly cooled hypereutectic gray iron 总被引:4,自引:0,他引:4
Y. Lerner 《Journal of Materials Engineering and Performance》2003,12(2):141-146
The effect of titanium on the structure and properties of a rapidly cooled hypereutectic cast gray iron has been studied on
the example of permanent mold (PM) casting. A microstructure study showed that titanium is a relatively strong element in
controlling solidification structure by increasing undercooling and thus promoting type D graphite. The effectiveness of titanium
additions depends on the base iron carbon equivalent (CE) with more pronounced changes in iron with a lower CE. The undercooling
ability of the titanium decreases after exceeding a certain level. Increasing titanium from 0.09–0.12% slightly increases
undercooling in iron with lower CE, but this effect was reduced in a more strongly hypereutectic iron. Alloying with titanium
generally improves tensile strength, but the effectiveness of titanium additions also depends on the base iron CE range. Scanning
electron microscope (SEM) studies revealed that most of the titanium-containing compounds were located in the metallic matrix:
titanium carbides have been found in pearlite, while titanium nitrides and carbonitrides were located in ferrite. The presence
of large amounts of extremely hard titanium-containing compounds, which often appear with steadite in a relatively high phosphorous
content PM gray iron, amplifies the negative effect of titanium on machinability. This study suggests that for optimal combination
of tensile strength/microstructure with good machinability, the titanium content in PM gray iron should not exceed 0.075%. 相似文献
7.
谢树新 《数字社区&智能家居》2009,(17)
已有文献中的支持向量机SMO算法推导过程计算复杂,该文给出一个简洁推导。整个推导过程没有复杂的计算,除了误差函数外,不需引入其它中间变量。 相似文献
8.
本文针对计算机专业学生学习计算机算法语言存在的问题,引用互动式教学的理论,设计了互动式教学模式,即"建-仿-读-改-写",提出了互动式教学的环境要求,分析了互动式教学的教学效果,基本形成了一套完整的教学方案。对提高计算机专业教学效果具有一定的指导意义。 相似文献
9.
10.
基于积件思想,对五年制高职计算机课程项目式教学进行探索,以C语言程序设计为例研究分析,并组建C语言程序设计课程知识点积件库,编写高职C语言程序设计课程项目式校本教材,分析C语言程序设计课程教学项目“阶梯电价计费”.并借助开源平台Moodle实现了教学项目的应用. 相似文献