全文获取类型
收费全文 | 19944篇 |
免费 | 3275篇 |
国内免费 | 1761篇 |
专业分类
电工技术 | 943篇 |
技术理论 | 2篇 |
综合类 | 1990篇 |
化学工业 | 5223篇 |
金属工艺 | 1650篇 |
机械仪表 | 1091篇 |
建筑科学 | 1683篇 |
矿业工程 | 357篇 |
能源动力 | 346篇 |
轻工业 | 760篇 |
水利工程 | 437篇 |
石油天然气 | 304篇 |
武器工业 | 158篇 |
无线电 | 2029篇 |
一般工业技术 | 2808篇 |
冶金工业 | 573篇 |
原子能技术 | 125篇 |
自动化技术 | 4501篇 |
出版年
2024年 | 77篇 |
2023年 | 368篇 |
2022年 | 488篇 |
2021年 | 781篇 |
2020年 | 764篇 |
2019年 | 746篇 |
2018年 | 769篇 |
2017年 | 928篇 |
2016年 | 950篇 |
2015年 | 1047篇 |
2014年 | 1362篇 |
2013年 | 1506篇 |
2012年 | 1545篇 |
2011年 | 1581篇 |
2010年 | 1273篇 |
2009年 | 1258篇 |
2008年 | 1159篇 |
2007年 | 1304篇 |
2006年 | 1154篇 |
2005年 | 927篇 |
2004年 | 830篇 |
2003年 | 683篇 |
2002年 | 597篇 |
2001年 | 444篇 |
2000年 | 371篇 |
1999年 | 344篇 |
1998年 | 279篇 |
1997年 | 264篇 |
1996年 | 167篇 |
1995年 | 165篇 |
1994年 | 130篇 |
1993年 | 115篇 |
1992年 | 125篇 |
1991年 | 87篇 |
1990年 | 68篇 |
1989年 | 58篇 |
1988年 | 38篇 |
1987年 | 35篇 |
1986年 | 25篇 |
1985年 | 38篇 |
1984年 | 31篇 |
1983年 | 23篇 |
1982年 | 42篇 |
1981年 | 10篇 |
1980年 | 4篇 |
1979年 | 8篇 |
1978年 | 2篇 |
1975年 | 5篇 |
1956年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
循环风与瓦斯浓度的关系 总被引:1,自引:0,他引:1
通过循环风时对瓦斯污染数学模型的建立 ,详细阐述了在各种情况下 ,瓦斯浓度的变化情况及治理措施。 相似文献
42.
43.
Ching-Liang Su 《Journal of Intelligent and Robotic Systems》2006,45(1):1-14
This research uses the object extracting technique to extract the index, middle and ring fingers from the hand images. The algorithm developed in this research can find the precise locations of the different fingers' fingertips and the finger-to-finger-valleys. After finding the positions of the fingertips and finger-valleys, the index, middle and ring fingers can be extracted from the hand images by using morphological technique. The extracted index, middle and ring fingers contain many useful geometry features. One can use these features to do the person's identification. The orientations of the index, middle and ring fingers are found in this research. Image rotating, image shifting, and image interpolating techniques are used to align different persons' index, middle and ring fingers. Image subtraction is used to exam the difference of two index, middle and ring finger images. In this research so far only use the index, middle and the ring fingers as the features to identify different persons.
★This work was supported by National Science Council under grant NSC 93-2213-E-212-011. 相似文献
44.
45.
聚合物-金属界面相形貌的研究 总被引:1,自引:0,他引:1
环氧树脂在 Al 合金表面生成纤维状的界面相结构,其形成、发展和特征与树脂的体系、交联反应条件以及 Al 合金的表面状态有关。环氧树脂的基础相为颗粒状的超结构组织。聚合物界面相的力学破坏表现为纤维体的拉伸、变形和断裂,而基础相在纯剪切受力时出现在45°方向的裂纹,并发展导致连接层的破坏。 相似文献
46.
煤矿局部通风的设计与应用技术 总被引:3,自引:0,他引:3
分析了现有煤矿局部通风工程中普遍存在的问题,采用符合矿井实际的设计和施工技术,就能在使用过程中获得显著效果,可大大减少漏风,提高有效风量,满足安全生产的需要,从而解决长距离独头掘进通风的难题。 相似文献
47.
Abstract. Locally stationary processes are non‐stationary stochastic processes the second‐order structure of which varies smoothly over time. In this paper, we develop a method to bootstrap the local periodogram of a locally stationary process. Our method generates pseudo local periodogram ordinates by combining a parametric time and non‐parametric frequency domain bootstrap approach. We first fit locally a time varying autoregressive model so as to capture the essential characteristics of the underlying process. A locally calculated non‐parametric correction in the frequency domain is then used so as to improve upon the locally parametric autoregressive fit. As an application, we investigate theoretically the asymptotic properties of the bootstrap method proposed applied to the class of local spectral means, local ratio statistics and local spectral density estimators. Some simulations demonstrate the ability of our method to give accurate estimates of the quantities of interest in finite sample situations and an application to a real‐life data‐set is presented. 相似文献
48.
J. L. Barron R. E. Mercer X. Chen P. Joe 《International journal of imaging systems and technology》2005,15(3):189-198
We present local least squares and regularization frameworks for computing 3D velocity (3D optical flow) from 3D radial velocity measured by a Doppler radar. We demonstrate the performance of our algorithms quantitatively on synthetic radial velocity data and qualitatively on real radial velocity data, obtained from the Doppler radar at Kurnell Radar station, Botany Bay, New South Wales, Australia. Radial velocity can be used to predict the future positions of storms in sequences of Doppler radar datasets.© 2005 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 15, 189–198, 2005 相似文献
49.
火焰图像特征在火灾数字图像识别中的运用 总被引:1,自引:0,他引:1
火焰尖角数目和圆形度是早期火灾火焰的主要特征,本文主要论述了如何在数学形态学基础上,利用火灾火焰的两个特点判断和识别早期火情。实验中,对火焰的二值图像进行开运算,即先腐蚀,再膨胀,目的是为了对火焰图像进行形态学滤波,去噪。从实验结果可以看出,该算法可以很好的识别火焰和干扰源。 相似文献
50.
M Isabel Sánchez de Rojas Julián Rivera Moisés Frías Félix Marín 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(3):209-217
Copper slag is a by‐product generated during smelting to extract copper metal from the ore. The copper slag obtained may exhibit pozzolanic activity and may therefore be used in the manufacture of addition‐containing cements. In this paper the effect of the incorporation of the copper slag in cement is measured. Blends of copper slag with Portland cement generally possess properties equivalent to Portland cement containing fly ash, but very different to the silica fume incorporation. Copper slag and fly ash reduce the heat of hydration more effectively than silica fume in mortars. The replacement of 30% cement by copper slag reduces the flexural and compressive strength in a similar way to fly ash; however, after 28 days, the reduction is less than the percentage of substitution. Hydrated calcium aluminate phases were analysed using scanning electron microscopy (SEM) and X‐ray diffraction (XRD) techniques. The pozzolanic activity of copper slag is similar to that of fly ash and higher than silica fume. In the presence of low water/cement ratios, certain pozzolanic materials produce a very compact cement paste that limits the space available for hydration products, a determining factor in the formation of hydrated calcium aluminates. SEM was found to be a useful analytical technique when aluminates are formed and can be clearly detected by XRD. Copyright © 2008 Society of Chemical Industry 相似文献