全文获取类型
收费全文 | 63654篇 |
免费 | 10484篇 |
国内免费 | 6607篇 |
专业分类
电工技术 | 6137篇 |
技术理论 | 2篇 |
综合类 | 5887篇 |
化学工业 | 2137篇 |
金属工艺 | 1373篇 |
机械仪表 | 4939篇 |
建筑科学 | 2392篇 |
矿业工程 | 1172篇 |
能源动力 | 757篇 |
轻工业 | 4480篇 |
水利工程 | 512篇 |
石油天然气 | 1558篇 |
武器工业 | 1056篇 |
无线电 | 16369篇 |
一般工业技术 | 5312篇 |
冶金工业 | 881篇 |
原子能技术 | 675篇 |
自动化技术 | 25106篇 |
出版年
2024年 | 618篇 |
2023年 | 1695篇 |
2022年 | 2720篇 |
2021年 | 3007篇 |
2020年 | 2981篇 |
2019年 | 2364篇 |
2018年 | 2051篇 |
2017年 | 2680篇 |
2016年 | 2876篇 |
2015年 | 3258篇 |
2014年 | 4998篇 |
2013年 | 4372篇 |
2012年 | 5336篇 |
2011年 | 5592篇 |
2010年 | 4238篇 |
2009年 | 4245篇 |
2008年 | 4175篇 |
2007年 | 4655篇 |
2006年 | 3847篇 |
2005年 | 3175篇 |
2004年 | 2415篇 |
2003年 | 2098篇 |
2002年 | 1519篇 |
2001年 | 1130篇 |
2000年 | 926篇 |
1999年 | 716篇 |
1998年 | 561篇 |
1997年 | 484篇 |
1996年 | 396篇 |
1995年 | 340篇 |
1994年 | 211篇 |
1993年 | 200篇 |
1992年 | 163篇 |
1991年 | 144篇 |
1990年 | 118篇 |
1989年 | 72篇 |
1988年 | 72篇 |
1987年 | 38篇 |
1986年 | 41篇 |
1985年 | 31篇 |
1984年 | 32篇 |
1983年 | 30篇 |
1982年 | 25篇 |
1981年 | 21篇 |
1980年 | 19篇 |
1979年 | 8篇 |
1978年 | 8篇 |
1975年 | 5篇 |
1959年 | 5篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
形态学边缘检测的新算法及其应用 总被引:3,自引:0,他引:3
刘岚岚 《红外与毫米波学报》1998,17(5):386-390
提出了一种基于数学形态学的边缘检测的所算法,该算法具有简便和灵活可编程控制等优点,比原来主算法更国完善,在实际应用中有着很好的前景,并给出了实验结果。 相似文献
92.
Takumi Haruna 《Corrosion Science》2003,45(9):2093-2104
We have investigated the electrochemical noise behavior of carbon steel in fully deaerated aqueous bicarbonate solutions, and discussed the optimum conditions of the noise analysis for estimating corrosion rate of the steel. Noise of the potential difference and of the short-circuit current between two identical steel coupons were successfully measured. The time-series noise patterns were transformed into frequency domain by fast Fourier transformation, and then their power spectrum densities (PSDs) at a frequency were determined to be compared with the corrosion rate. The PSDs of the potential and of the current varied with changing environmental factors of bicarbonate concentration, pH, and immersion time. The factors also controlled the corrosion rate of the steel. The PSDs were associated with the corrosion rate, and then it was found that the PSDs of the potential and of the current showed linear correlation with the corrosion rate in log-log scale. There was also linear relationship between the corrosion rate and a spectral noise resistance obtained from the PSDs of the potential and the current. The linearities of the three correlations were better at a lower analyzed frequency. Furthermore, the PSDs of the current and the noise resistance indicated more linear correlation with the corrosion rate than that of the potential. As the simplicity of the measurement system is additionally considered, it is concluded that the PSD of the current noise at an analyzed frequency of 3 mHz is the optimum conditions for estimating the corrosion rate from 10−2 to 100 A m−2 in this study. 相似文献
93.
陈明志 《数字社区&智能家居》2006,1(12):159-160
本文对数字图像中几种具有代表性的边缘检测算子进行了理论分析,并通过VC编程实验,对各种算法进行实现,通过比较得出了各自的优缺点和适用范围。 相似文献
94.
陈希武 《中国计量学院学报》1992,(1)
本文提出并研制成补偿式光纤F-P干涉仪信号处理系统,提出了用来测量微小位移信号的三种方法及电路,即透射峰时间间隔测量法、光脉冲基波幅度测量法(精密整流法)、鉴相法。测试结果表明:时间间隔测量法,它的最大灵敏度达到0.26纳米/微秒;精密整流法,最大灵敏度为2.38纳米/伏特。 相似文献
95.
We present a new background-subtraction technique fusing contours from thermal and visible imagery for persistent object detection in urban settings. Statistical background-subtraction in the thermal domain is used to identify the initial regions-of-interest. Color and intensity information are used within these areas to obtain the corresponding regions-of-interest in the visible domain. Within each region, input and background gradient information are combined to form a Contour Saliency Map. The binary contour fragments, obtained from corresponding Contour Saliency Maps, are then fused into a single image. An A* path-constrained search along watershed boundaries of the regions-of-interest is used to complete and close any broken segments in the fused contour image. Lastly, the contour image is flood-filled to produce silhouettes. Results of our approach are evaluated quantitatively and compared with other low- and high-level fusion techniques using manually segmented data. 相似文献
96.
Based on a polynomial operator approach, a new sparse controller structure is derived, which is actually an improved version of the recently proposed structure [Li, G. (2004). A polynomial-operator-based DFIIt structure for IIR filters. IEEE Transactions on Circuits and Systems II, 51, 147-151]. The performance of the proposed structure is analyzed by deriving the corresponding expression of roundoff noise gain and the problem of finding optimized sparse structures is solved efficiently with a genetic algorithm (GA). A numerical example is given, which shows that the newly developed structure can achieve much better performance than some well-known structures and particularly outperforms the traditional optimal fully parametrized realization greatly in terms of reducing roundoff noise and implementation complexity. 相似文献
97.
98.
99.
A fast digital Radon transform based on recursively defined digital straight lines is described, which has the sequential complexity of N2 log N additions for an N × N image. This transform can be used to evaluate the Hough transform to detect straight lines in a digital image. Whilst a parallel implementation of the Hough transform algorithm is difficult because of global memory access requirements, the fast digital Radon transform is vectorizable and therefore well suited for parallel computation. The structure of the fast algorithm is shown to be quite similar to the FFT algorithm for decimation in frequency. It is demonstrated that even for sequential computation the fast Radon transform is an attractive alternative to the classical Hough transform algorithm. 相似文献
100.