全文获取类型
收费全文 | 8762篇 |
免费 | 603篇 |
国内免费 | 215篇 |
专业分类
电工技术 | 444篇 |
技术理论 | 1篇 |
综合类 | 495篇 |
化学工业 | 1596篇 |
金属工艺 | 304篇 |
机械仪表 | 404篇 |
建筑科学 | 541篇 |
矿业工程 | 210篇 |
能源动力 | 246篇 |
轻工业 | 856篇 |
水利工程 | 140篇 |
石油天然气 | 451篇 |
武器工业 | 52篇 |
无线电 | 765篇 |
一般工业技术 | 1037篇 |
冶金工业 | 845篇 |
原子能技术 | 59篇 |
自动化技术 | 1134篇 |
出版年
2024年 | 32篇 |
2023年 | 117篇 |
2022年 | 204篇 |
2021年 | 290篇 |
2020年 | 215篇 |
2019年 | 194篇 |
2018年 | 252篇 |
2017年 | 263篇 |
2016年 | 244篇 |
2015年 | 289篇 |
2014年 | 412篇 |
2013年 | 530篇 |
2012年 | 524篇 |
2011年 | 583篇 |
2010年 | 479篇 |
2009年 | 462篇 |
2008年 | 472篇 |
2007年 | 453篇 |
2006年 | 445篇 |
2005年 | 348篇 |
2004年 | 263篇 |
2003年 | 246篇 |
2002年 | 219篇 |
2001年 | 227篇 |
2000年 | 192篇 |
1999年 | 206篇 |
1998年 | 294篇 |
1997年 | 210篇 |
1996年 | 159篇 |
1995年 | 134篇 |
1994年 | 103篇 |
1993年 | 84篇 |
1992年 | 52篇 |
1991年 | 39篇 |
1990年 | 32篇 |
1989年 | 34篇 |
1988年 | 35篇 |
1987年 | 22篇 |
1986年 | 29篇 |
1985年 | 17篇 |
1984年 | 16篇 |
1983年 | 20篇 |
1982年 | 16篇 |
1981年 | 13篇 |
1980年 | 7篇 |
1979年 | 15篇 |
1978年 | 11篇 |
1977年 | 15篇 |
1976年 | 15篇 |
1975年 | 8篇 |
排序方式: 共有9580条查询结果,搜索用时 12 毫秒
171.
Eymard L. Tabary L. Gerard E. Boukabara S. Le Cornec A. 《Geoscience and Remote Sensing, IEEE Transactions on》1996,34(2):291-303
For pt.I see ibid., vol.31, no.6, p.1186-98 (1993). The ERS-1 microwave radiometer was designed to correct the satellite altimeter data for the excess path delay due to tropospheric humidity. The brightness temperature calibration was tested using two radiative transfer models, applied to the same coincident meteorological profiles over ocean. Differences were analyzed by similarly comparing calculated brightness temperatures with SSM/I data, for the same meteorological data set, extracted from ECMWF (European Center for Medium range Weather Forecasting) analyses. The calibration of the two channels of the ERS-1 microwave radiometer required correction of a few Kelvin. The final water vapor and altimeter path delay validation was performed by comparing routine radiosonde measurements with the retrieved water vapor and altimeter path corrections over a one-year period 相似文献
172.
用解析的方法模拟了T=300K和77K时,fT和fmax与集电极电流密度Jc的关系,在大电流下考虑了异质结势垒效应的影响。模拟结果和用数值方法以及实验所得到的结果一致。同时,还建立了与之相应的Si/SiGeeb异质结和SiGe/Sibc异质结电容模型。 相似文献
173.
本文介绍了用准波导耦合m线技术测量聚合物薄膜厚度的方法。测量结果表明,薄膜样品厚度的误差为3.62×10^-2μm。并对测量精度作了分析和讨论。 相似文献
174.
GaAs MESFET欧姆接触可靠性研究进展 总被引:1,自引:0,他引:1
报道了n型GaAs上欧姆接触的制备及其可靠性,以及基于欧姆接触退经的GaAsMESPET的失效分析,结果表明,n型GaAs上欧姆接触的制备已日趋成熟,接触电阻有所减小,表面形貌及热稳定性方面都得到了很大程度的提高,接触材料也日趋丰富GaAsMESFET的失效分析方法也有明显改进。 相似文献
175.
介绍一种使用傅里叶全息滤波器的光电图像形态学处理系统,其中关于图像结构元的扩张,侵蚀及开和闭等基本运算于傅里叶全息光学方法产生的图像与结构元的卷积结果,其迭代过程使用了计算机控制的电寻址空间光调制器,该系统具有结构简单、能反复迭代、易于根据图像设计、更换及使用计算机制全息图产生结构元等优点。 相似文献
176.
针对电力变压器设计、选型中有关无功补偿配置、额定电压选择、经济运行条件及动稳定问题进行了探讨,并就如何优化变压器参数配置,提高变压器的运行性能提出了相应的技术措施。 相似文献
177.
178.
Gerard M O'Brien Christopher C Wheatley Carlos Iglesias Nigel H Poulter 《Journal of the science of food and agriculture》1994,65(4):391-399
Two rapid semi-quantitative assays for total cyanogens in cassava were evaluated. These were the well-known rapid picrate paper test, and a recently proposed rapid paper test involving the reagent tetra base (TB, 4,4′- methylenebis-(N, N-dimethylaniline)). A precise colorimetric assay was used as a control in the evaluative work. After primary evaluation, both assay methods underwent some modification regarding the interpretation of sample scores. As a result, the reliability of the picrate assay was greatly improved. The TB assay was modified in the interests of safety. Evaluation of this assay over a range of temperatures between 20 and 35°C showed no significant temperature effects upon performance when the new scoring interpretation system was used. The level of endogenous linamarase activity in the sample was found to be an influential factor in rapid assay performance. In a series of comparative trials in three distinct ecosystems, the newly modified picrate assay produced correct results in 68% of cases. This compared with 66% of results correct in the TB assay. It was observed that the TB assay performed more reliably with low cyanogen samples, whilst the picrate assay was more reliable with intermediate cyanogen samples. 相似文献
179.
霍尔传感器在小型内燃机电控系统中的应用 总被引:1,自引:0,他引:1
本文介绍了霍尔传感器的原理及其目前在汽车发动机上的一些应用,并对其在摩托车发动机上作为油门位置传感器进行了实验研究。 相似文献
180.
Functionalized carbon nanomaterials, as significant options for renewable energy systems, are widely utilized in diversified electrochemical reactions in virtue of property advantages. The inevitable defect sites in architectures greatly affect physicochemical properties of carbon nanomaterials, thus defect engineering has recently become a vital research orientation of carbon‐based electrocatalysts. The intentionally introduced intrinsic carbon defect sites in the frameworks can directly serve as the potential active sites owing to the altered surface charge state, modulated adsorption free energy of key intermediates, as well as diminished bandgap. Furthermore, the synergistic sites between intrinsic defects and heteroatom dopants/captured atomic metal species can further optimize the electronic structure and adsorption/desorption behavior, making carbon‐based catalysts comparable to commercial precious metal catalysts in electrocatalysis. With pressing research demands, the common configurations, construction strategies, structure–activity relationships, and characterization methods for intrinsic carbon defect‐involved catalytic centers are systematically summarized. Such theoretical and experimental evidences of intrinsic defect‐induced activity can reveal the active centers and relevant catalytic mechanism, thereby providing necessary guidance for the design and construction of highly efficient carbon‐based electrocatalysts and promoting their commercial applications. 相似文献