全文获取类型
收费全文 | 113610篇 |
免费 | 7110篇 |
国内免费 | 3375篇 |
专业分类
电工技术 | 4786篇 |
技术理论 | 11篇 |
综合类 | 5353篇 |
化学工业 | 16439篇 |
金属工艺 | 4319篇 |
机械仪表 | 5013篇 |
建筑科学 | 6542篇 |
矿业工程 | 2255篇 |
能源动力 | 2393篇 |
轻工业 | 7487篇 |
水利工程 | 1959篇 |
石油天然气 | 3874篇 |
武器工业 | 580篇 |
无线电 | 10293篇 |
一般工业技术 | 12117篇 |
冶金工业 | 24791篇 |
原子能技术 | 937篇 |
自动化技术 | 14946篇 |
出版年
2024年 | 309篇 |
2023年 | 1408篇 |
2022年 | 2303篇 |
2021年 | 3229篇 |
2020年 | 2396篇 |
2019年 | 1940篇 |
2018年 | 2565篇 |
2017年 | 2902篇 |
2016年 | 3167篇 |
2015年 | 3554篇 |
2014年 | 3916篇 |
2013年 | 4474篇 |
2012年 | 6630篇 |
2011年 | 7378篇 |
2010年 | 4736篇 |
2009年 | 4621篇 |
2008年 | 4440篇 |
2007年 | 4207篇 |
2006年 | 3994篇 |
2005年 | 6285篇 |
2004年 | 4768篇 |
2003年 | 3983篇 |
2002年 | 2645篇 |
2001年 | 2325篇 |
2000年 | 2037篇 |
1999年 | 2688篇 |
1998年 | 7885篇 |
1997年 | 5220篇 |
1996年 | 3884篇 |
1995年 | 2606篇 |
1994年 | 2077篇 |
1993年 | 1800篇 |
1992年 | 790篇 |
1991年 | 697篇 |
1990年 | 639篇 |
1989年 | 576篇 |
1988年 | 509篇 |
1987年 | 366篇 |
1986年 | 301篇 |
1985年 | 243篇 |
1984年 | 125篇 |
1983年 | 122篇 |
1982年 | 176篇 |
1981年 | 209篇 |
1980年 | 221篇 |
1979年 | 72篇 |
1978年 | 103篇 |
1977年 | 617篇 |
1976年 | 1331篇 |
1975年 | 100篇 |
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
91.
Presents an obituary and information about the life and accomplishments of Josef Maria Bro?ek. Born August 14, 1913, in the ancient town of Melnik, in central Bohemia, today the Czech Republic, Josef spent his childhood in Poland (Warsaw, 1913- 1915) and in Siberia (1915-1920). His education in Czechoslovakia culminated with a thesis on "Memory, Its Measurement and Structure" and a PhD awarded in June 1937. In the history of psychology, his lifetime project bore the title "Historiography of Psychology Around the World," and it covered about 20 geographical areas. Extensive attention was devoted to institutional and organizational developments as journals, academic settings, archives, museums, research groups, conferences, and institutes. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
92.
Chun-Tsen Lu Kun-Wei Lin Huey-Ing Chen Hung-Ming Chuang Chun-Yuan Chen Wen-Chau Liu 《Electron Device Letters, IEEE》2003,24(6):390-392
A new and interesting Pd-oxide-Al/sub 0.3/Ga/sub 0.7/As MOS hydrogen sensor has been fabricated and studied. The steady-state and transient responses with different hydrogen concentrations has been measured at various temperatures. Based on the large Schottky barrier height and presence of oxide layer, the studied device exhibits a high hydrogen detection sensitivity and wide temperature operating regime. The studied device exhibits the low-leakage current and obvious current changes when exposed to hydrogen-contained gas. Even at room temperature, a very high hydrogen detection sensitivity of 155.9 is obtained when a 9090 ppm H/sub 2//air gas is introduced. Furthermore, when exposed to hydrogen-contained gas at 95/spl deg/C, both the forward and reverse currents are substantially increased with increased hydrogen concentration. In other words, the studied device can be used as a hydrogen sensor under the applied bidirectional bias. Under the applied voltage of 0.35 V and 9090 ppm H/sub 2//air hydrogen ambient, a fast adsorption response time about 10 s is found. The transient and steady-state characteristics of hydrogen adsorption are also investigated. 相似文献
93.
基于模式理论光栅椭偏参数反演的数值模拟 总被引:5,自引:2,他引:3
将一种广泛用于求解系统优化问题的方法——正单纯形法,求解光栅的椭偏方程。首先,利用求解光栅的傅立叶模式理论对TE和TM波的复反射系数进行求解。然后计算出其相应的椭偏参数(△,Ψ),并在该值的基础上加入不同偏差的随机高斯噪声,将加入噪声后的值(△m,Ψm)作为模拟测量值。最后使用优化算法进行反演。通过对几种常用面形光栅椭偏参数的数值模拟,一方面表明傅立叶模式理论计算光栅的椭偏参数不仅精度高。而且速度快;另一方面表明利用正单纯形法得到的光栅参数值很接近于正演时假设的参数值,从而从理论上证明了利用椭偏法测量光栅各种光学参数的可行性。 相似文献
94.
95.
Whispering-gallery-like modes in square resonators 总被引:1,自引:0,他引:1
Wei-Hua Guo Yong-Zhen Huang Qiao-Yin Lu Li-Juan Yu 《Quantum Electronics, IEEE Journal of》2003,39(9):1106-1110
The mode frequencies and field distributions of whispering-gallery (WG)-like modes of square resonators are obtained analytically, which agree very well with the numerical results calculated by the FDTD technique and Pade approximation method. In the analysis, a perfect electric wall for the transverse magnetic mode or perfect magnetic wall for the transverse electric mode is assumed at the diagonals of the square resonators, which not only provides the transverse mode confinement, but also requires the longitudinal mode number to be an even integer. The WG-like modes of square resonators are nondegenerate modes with high-quality factors, which make them suitable for fabricating single-mode low-threshold semiconductor microcavity lasers. 相似文献
96.
The prohibitive - exponential in the number of users - computational complexity of the maximum-likelihood multiuser detector for direct-sequence code-division multiple-access communications has fueled an extensive research effort for the development of low-complexity multiuser detection alternatives. We show that we can efficiently and effectively approach the error rate performance of the optimum multiuser detector as follows. We utilize a multiuser zero-forcing or minimum mean-square error (MMSE) linear filter as a preprocessor and we establish that the output magnitudes, when properly scaled, provide a reliability measure for each user bit decision. Then, we prepare an ordered, reliability-based error search sequence of length linear in the number of users; it returns the most likely user bit vector among all visited options. Numerical and simulation studies for moderately loaded systems that permit exact implementation of the optimum detector indicate that the error rate performance of the optimum and the proposed detector are nearly indistinguishable over the whole predetection. signal-to-noise ratio range of practical interest. Similar studies for higher user loads (that prohibit comparisons with the optimum detector) demonstrate error rate performance gains of orders of magnitude in comparison with straight decorrelating or MMSE multiuser detection. 相似文献
97.
98.
99.
100.