全文获取类型
收费全文 | 20413篇 |
免费 | 1900篇 |
国内免费 | 1107篇 |
专业分类
电工技术 | 1430篇 |
综合类 | 1866篇 |
化学工业 | 3202篇 |
金属工艺 | 1077篇 |
机械仪表 | 1116篇 |
建筑科学 | 1671篇 |
矿业工程 | 597篇 |
能源动力 | 594篇 |
轻工业 | 1522篇 |
水利工程 | 486篇 |
石油天然气 | 964篇 |
武器工业 | 141篇 |
无线电 | 2243篇 |
一般工业技术 | 2332篇 |
冶金工业 | 864篇 |
原子能技术 | 249篇 |
自动化技术 | 3066篇 |
出版年
2024年 | 51篇 |
2023年 | 247篇 |
2022年 | 459篇 |
2021年 | 713篇 |
2020年 | 546篇 |
2019年 | 522篇 |
2018年 | 520篇 |
2017年 | 555篇 |
2016年 | 501篇 |
2015年 | 761篇 |
2014年 | 907篇 |
2013年 | 1035篇 |
2012年 | 1206篇 |
2011年 | 1201篇 |
2010年 | 1202篇 |
2009年 | 1059篇 |
2008年 | 1182篇 |
2007年 | 1138篇 |
2006年 | 989篇 |
2005年 | 809篇 |
2004年 | 768篇 |
2003年 | 1146篇 |
2002年 | 1589篇 |
2001年 | 1402篇 |
2000年 | 693篇 |
1999年 | 486篇 |
1998年 | 321篇 |
1997年 | 261篇 |
1996年 | 188篇 |
1995年 | 199篇 |
1994年 | 169篇 |
1993年 | 124篇 |
1992年 | 100篇 |
1991年 | 64篇 |
1990年 | 58篇 |
1989年 | 45篇 |
1988年 | 39篇 |
1987年 | 23篇 |
1986年 | 23篇 |
1985年 | 16篇 |
1984年 | 13篇 |
1983年 | 12篇 |
1982年 | 9篇 |
1981年 | 6篇 |
1980年 | 16篇 |
1979年 | 8篇 |
1977年 | 4篇 |
1976年 | 9篇 |
1975年 | 5篇 |
1972年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 859 毫秒
41.
QifengShu JiayunZhang 《北京科技大学学报(英文版)》2005,12(3):221-224
Based on recently published experimental data, the Riboud model was modified for viscosity estimation of the slags containing calcium fluoride. The estimated values were in good agreement with measured data. Reasonable estimation can be achieved using the modified Riboud model for mould fluxes and ESR (eletro slag remelting) slags. Especially for ESR slags, the modified Riboud model can provide much more precise values than the original Riboud model. 相似文献
42.
Waveband-switchable SOA ring laser constructed with a phase modulator loop mirror filter 总被引:1,自引:0,他引:1
M.P. Fok K.L. Lee C. Shu 《Photonics Technology Letters, IEEE》2005,17(7):1393-1395
An electrically tunable multiwavelength source has been developed using a birefringence-based optical comb filter in a semiconductor optical amplifier ring laser. The filter is constructed with an electrooptic phase modulator placed inside a fiber loop mirror. By controlling the birefringence of the modulator through the applied bias, the radio-frequency power, or the modulation frequency, we achieve a continuous shift of the spectral comb to access different interleaved wavebands. Electrical waveband switching has been successfully demonstrated for 21 wavelengths at 100-GHz grid spacing with an optical signal-to-noise ratio over 40 dB. 相似文献
43.
44.
The stress intensity factors for a short crack partially penetrating an inclusion of arbitrary shape
Some approximate solutions for predicting the stress intensity factor of a short crack penetrating an inclusion of arbitrary
shape have been developed under mode I and mode II loading conditions. The derivation of the fundamental formula is based
on the transformation toughening theory. The transformation strains in the inclusion are induced by the crack-tip field and
remotely applied stresses, and approximately evaluated by the Eshelby equivalent inclusion theory. As validated by detailed
finite element (FE) analyses, the developed solutions have good accuracy for different inclusion shape and for a wide range
of modulus ratio between inclusion and matrix material. 相似文献
45.
海底天然气管道投产案例分析 总被引:1,自引:0,他引:1
为防止形成天然气水合物,天然气管道在投产前必须彻底干燥。海底管道距离长,不能分段施工,多采用清管器组加干燥剂的作业方案,这就存在清管器组的运行控制、卡球和窜漏等问题,作业难度高、风险大。针对我国海底输气管道投产前干燥施工过程中出现的憋压、卡球、窜漏和清管器磨损等问题进行了分析,说明了发生问题的原因。对比研究了不同管道干燥方案的优缺点、清管器使用的合理性、干燥剂使用效果和干燥指标的制定与监测方法等问题。在此基础上, 提出了针对海底天然气管道的凝胶、干燥剂和多盘清管器的组合干燥方案。该方案能有效解决密封、卡球和凝胶滞留等问题,并能确保施工质量,对类似工程有借鉴意义。 相似文献
46.
对智能电动机控制器的情况作了介绍,结合工作实践提出了维护要点和建议,并对该控制器的参数设置进行了说明,这对使用该设备的工业企业有一定的指导意义。 相似文献
47.
48.
Shu‐Li Sun Jing Ma Nan Lv 《International Journal of Adaptive Control and Signal Processing》2008,22(10):932-948
Based on the optimal fusion estimation algorithm weighted by scalars in the linear minimum variance sense, a distributed optimal fusion Kalman filter weighted by scalars is presented for discrete‐time stochastic singular systems with multiple sensors and correlated noises. A cross‐covariance matrix of filtering errors between any two sensors is derived. When the noise statistical information is unknown, a distributed identification approach is presented based on correlation functions and the weighted average method. Further, a distributed self‐tuning fusion filter is given, which includes two stage fusions where the first‐stage fusion is used to identify the noise covariance and the second‐stage fusion is used to obtain the fusion state filter. A simulation verifies the effectiveness of the proposed algorithm. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
49.
Hung‐Yee Shu 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(3):273-280
Liquid–liquid two‐phase epoxidation from cyclohexene and cyclooctene in aqueous potassium peroxymonosulfate (commercially available as Oxone®) solution was studied as an application in pollution prevention. To avoid potential emissions of volatile organic compounds an aqueous solution was employed to replace the usual chlorinated solvents used in epoxide production. A droplet column reactor and stirred tank reactor were used to investigate two‐phase synthesis of epoxide. An aqueous Oxone® solution was used to oxidize a dispersion of alkene droplets and form epoxide. The study of aqueous epoxidation in both reactors showed that the epoxidation of alkenes can be represented as a first order reaction with respect to alkene. The salting out effect of Oxone® concentration was studied in both reactors and found to be very similar at optimal conditions. In comparing the two reactors, it was found that the droplet column reactor produces larger quantities of product per unit reactor volume for the same reaction time. The objective of this study is to provide an alternative reactor design and synthesis route that can meet pollution prevention goals. Copyright © 2004 Society of Chemical Industry 相似文献
50.
基于因特网的远程校准技术进展 总被引:3,自引:0,他引:3
远程校准是信息技术特别是计算机网络技术与传统的计量测试技术结合的必然产物。本文介绍与之有关的一些概念及国外开展相应项目的情况。结合我们自己的一个实验装置.对在我国开展远程校准工作的必要性和可行性提出一些看法。 相似文献