全文获取类型
收费全文 | 27687篇 |
免费 | 1177篇 |
国内免费 | 856篇 |
专业分类
电工技术 | 1282篇 |
技术理论 | 1篇 |
综合类 | 716篇 |
化学工业 | 2981篇 |
金属工艺 | 949篇 |
机械仪表 | 2034篇 |
建筑科学 | 2327篇 |
矿业工程 | 632篇 |
能源动力 | 5691篇 |
轻工业 | 418篇 |
水利工程 | 173篇 |
石油天然气 | 401篇 |
武器工业 | 116篇 |
无线电 | 1914篇 |
一般工业技术 | 2069篇 |
冶金工业 | 1027篇 |
原子能技术 | 533篇 |
自动化技术 | 6456篇 |
出版年
2024年 | 46篇 |
2023年 | 399篇 |
2022年 | 602篇 |
2021年 | 790篇 |
2020年 | 703篇 |
2019年 | 629篇 |
2018年 | 661篇 |
2017年 | 795篇 |
2016年 | 941篇 |
2015年 | 1066篇 |
2014年 | 1675篇 |
2013年 | 1746篇 |
2012年 | 1556篇 |
2011年 | 2858篇 |
2010年 | 1896篇 |
2009年 | 1812篇 |
2008年 | 1628篇 |
2007年 | 1723篇 |
2006年 | 1326篇 |
2005年 | 1043篇 |
2004年 | 799篇 |
2003年 | 742篇 |
2002年 | 586篇 |
2001年 | 431篇 |
2000年 | 397篇 |
1999年 | 386篇 |
1998年 | 358篇 |
1997年 | 275篇 |
1996年 | 276篇 |
1995年 | 219篇 |
1994年 | 217篇 |
1993年 | 170篇 |
1992年 | 131篇 |
1991年 | 94篇 |
1990年 | 93篇 |
1989年 | 82篇 |
1988年 | 73篇 |
1987年 | 49篇 |
1986年 | 42篇 |
1985年 | 93篇 |
1984年 | 63篇 |
1983年 | 61篇 |
1982年 | 68篇 |
1981年 | 31篇 |
1980年 | 25篇 |
1979年 | 13篇 |
1978年 | 13篇 |
1977年 | 7篇 |
1975年 | 7篇 |
1974年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2003,510(3):248-261
The energy dependence of the energy and position resolutions of the electromagnetic calorimeter prototype made of lead tungstate crystals produced in Bogoroditsk (Russia) and Shanghai (China) is presented. These measurements were carried out at the Protvino accelerator using a 1–45 GeV electron beam. The crystals were coupled to photomultiplier tubes. The dependence of energy and position resolutions on different factors as well as the measured electromagnetic shower lateral profile are presented. 相似文献
2.
Analysis of non-stationary electrochemical oscillations emerges utilization of the techniques allowing an observation of time evolution of their parameters such as instantaneous frequency, amplitude or frequency band. An algorithm of extraction of these parameters can be based on one of linear or quadratic time-frequency representations of oscillations record. In this paper, the authors present representatives of such transformations (Choi-Williams and Cone-shaped) originating from one of the most popular joint time-frequency energy distribution—Wigner-Ville distribution. Short introduction to the mathematics of the topic discussed is provided, then the authors present an example of application in the analysis of current oscillations of copper dissolution process. 相似文献
3.
先说明市内接入网的单位用户和住家用户两大类使用通信和电视、交互型和分配型业务的要求不相同,相应地对光纤传输的应用须作不同的考虑,文中认为;光纤从市内交换局直连办公大楼是合乎现实需要的,而对于居民住家,宜选用光纤连至路边或光纤与同轴结合和适当利用无源光网络等方案,俟将来时机成熟才实行光纤连至每一家,文末有概括总结,说明接入网不同于长途网,接入网的光纤系统可以使用常规单模光纤,工作于波长1.3μm,而光放大器和波分多路系统不是普遍需要,但光电子集成在光端机中是必要的。 相似文献
4.
一种具有带孔补偿过滤器的γ剂量计的能响补偿计算 总被引:1,自引:0,他引:1
对在低能区有过高响应的γ辐射剂量计可采用带孔补偿过滤器进行能响补偿。本文介绍了对这类补偿过滤器选择最佳补偿参数(材料厚度和孔隙率)的近似求解方法;并对 CaSO:Tm 热释光剂量计用此方法作了实例计算。文中还计算了自制带有鼠笼结构的这类补偿过滤器的 CaSO:,Tm热释光剂量计对照射量的能量响应,与实测结果比较,各能量点响应的最大相差为10%。 相似文献
5.
用仿真工具优化车辆动力系统(一) 总被引:1,自引:0,他引:1
在本文的第一部分,介绍了一种理想的车辆动力系统的计算机辅助开发过程。它显示了现代仿真技术在产品持续发展过程中的作用,该技术采用硬件回路作非在线的仿真,并通过现代化的试验手段对车辆进行匹配。特别重要的是提供了将电控变速器和发动机控制单元综合的可能性。接着是在线仿真在诸如发动机和变速器模式方面的应用和发展,它是上述开发过程的基础。根据上述的方法论,本文论述了仿真技术已取得的成绩和将来的应用可能性。 相似文献
6.
Organic conductor is a kind of organic compound which has special electronic and magnetic properties. The research of the organic compounds has received considerable attention because of their potential applications in many areas. The molecular conductive units are theoretically investigated as well as their energy gap and charge distribution. The relationship of conductivity and micro-mechanism is discussed. 相似文献
7.
2005年11月份邯郸钢铁厂8万煤气柜外送煤气加压机采用高压变频技术改造。其原因是该加压机外送量波动较大,采用普通阀门调节打回流,将会浪费大量电能,采用变频技术改造后,节能效果非常明显。 相似文献
8.
9.
The influence of raw material characteristics on the industrial pelletizing process and pellet quality 总被引:1,自引:0,他引:1
Mehrdad Arshadi Rolf Gref Paul Geladi Sten-Axel Dahlqvist Torbjörn Lestander 《Fuel Processing Technology》2008
Industrial pelletizing of sawdust was carried out as a designed experiment in the factors: sawdust moisture content, fractions of fresh pine, stored pine and spruce. The process parameters and response variables were energy consumption, pellet flow rate, pellet bulk density, durability and moisture content. The final data consisted of twelve industrial scale runs. Because of the many response variables, data evaluation was by principal component analysis of a 12 × 9 data matrix. The two principal component model showed a clustering of samples, with a good reproducibility of the center points. It also showed a positive correlation of energy consumption, bulk density and durability all negatively correlated to flow rate and moisture content. The stored pine was more related to high durability and bulk density. The role of the spruce fraction was unclear. The design matrix, augmented with the process parameters was a 12 × 6 matrix. Partial least squares regression showed excellent results for pellet moisture content and bulk density. The model for durability was promising. A 12 × 21 data matrix of fatty- and resin acid concentrations measured by GC–MS showed the differences between fresh and stored pine very clearly. The influence of the spruce fraction was less clear. However, the influence of the fatty- and resin acids on the pelletizing process could not be confirmed, indicating that other differences between fresh and stored pine sawdust have to be investigated. This work shows that it is possible to design the pelletizing process for moderate energy consumption and high pellet quality. 相似文献
10.
A new spreadsheet-cell-object-oriented algorithm for the first-order reliability method is proposed and illustrated for cases with correlated nonnormals and explicit and implicit performance functions. The new approach differs from the writers earlier algorithm by obviating the need for computations of equivalent normal means and equivalent normal standard deviations. It obtains the solution faster and is more efficient, robust, and succinct. Other advantages include ease of initialization prior to constrained optimization, ease of randomization of initial values for checking robustness, and fewer required optimization constraints during spreadsheet-automated search for the design point. Two cases with implicit performance functions, namely an asymmetrically loaded beam on Winkler medium and a strut with complex supports are analyzed using the new approach and discussed. Comparisons are also made between the proposed approach and that based on Rosenblatt transformation. 相似文献