全文获取类型
收费全文 | 107892篇 |
免费 | 7552篇 |
国内免费 | 3215篇 |
专业分类
电工技术 | 4598篇 |
技术理论 | 4篇 |
综合类 | 4380篇 |
化学工业 | 19837篇 |
金属工艺 | 5460篇 |
机械仪表 | 7129篇 |
建筑科学 | 5622篇 |
矿业工程 | 1337篇 |
能源动力 | 3750篇 |
轻工业 | 8048篇 |
水利工程 | 1459篇 |
石油天然气 | 2728篇 |
武器工业 | 486篇 |
无线电 | 15101篇 |
一般工业技术 | 17862篇 |
冶金工业 | 6350篇 |
原子能技术 | 1410篇 |
自动化技术 | 13098篇 |
出版年
2024年 | 283篇 |
2023年 | 1392篇 |
2022年 | 2497篇 |
2021年 | 3731篇 |
2020年 | 2705篇 |
2019年 | 2619篇 |
2018年 | 2976篇 |
2017年 | 3129篇 |
2016年 | 3489篇 |
2015年 | 3652篇 |
2014年 | 4939篇 |
2013年 | 6530篇 |
2012年 | 6990篇 |
2011年 | 8035篇 |
2010年 | 6565篇 |
2009年 | 6363篇 |
2008年 | 6253篇 |
2007年 | 5427篇 |
2006年 | 5261篇 |
2005年 | 4511篇 |
2004年 | 3634篇 |
2003年 | 3474篇 |
2002年 | 3588篇 |
2001年 | 3018篇 |
2000年 | 2523篇 |
1999年 | 2250篇 |
1998年 | 2622篇 |
1997年 | 1853篇 |
1996年 | 1600篇 |
1995年 | 1255篇 |
1994年 | 1053篇 |
1993年 | 848篇 |
1992年 | 620篇 |
1991年 | 537篇 |
1990年 | 453篇 |
1989年 | 396篇 |
1988年 | 336篇 |
1987年 | 243篇 |
1986年 | 180篇 |
1985年 | 151篇 |
1984年 | 121篇 |
1983年 | 77篇 |
1982年 | 60篇 |
1981年 | 61篇 |
1980年 | 46篇 |
1979年 | 39篇 |
1978年 | 31篇 |
1977年 | 40篇 |
1976年 | 72篇 |
1975年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Arthroscopic reduction and fixation of bony avulsion of the posterior cruciate ligament of the tibia
Bony avulsion fractures of the posterior cruciate ligament of the tibia have commonly been treated by open reduction and internal fixation using the posterior approach. However, this approach, using the prone position, makes it difficult to investigate and treat other combined injuries of the knee joint. We report a case of posterior cruciate ligament avulsion of the tibia that was arthroscopically reduced and firmly fixed with two cannulated screws. The posterior sag was absent after the operation and the result was excellent. By arthroscopy, we got rigid fixation of the avulsed fragment for early rehabilitation, and detection of a concomitant injury was also possible. 相似文献
32.
Ki Hyun Kim Yong Hoon Kang Byoungho Lee 《Photonics Technology Letters, IEEE》1997,9(12):1610-1612
A photorefractive volume hologram was recorded and probed using light diffracted from a tapered optical fiber as a reference beam. A single-mode fiber (SMF) was chemically etched and tapered to give a complicated beam pattern, and it is shown that the tapered optical fiber can be utilized to increase the storage density of the volume hologram. Spatial selectivity of the volume hologram with this method was increased by two times compared to the normal SMF referencing, which is due to the fact that the complicated beam pattern has little correlation with its shifted version 相似文献
33.
制作压力传感器时,在二氧化硅层上淀积多晶硅膜,既可利用优良的机械特性,又可保证压敏电阻与衬底间具有良好的绝缘性,由此可大大提高器件的温度特性。介绍了一种多晶硅压力传感器的原理和设计。实验结果表明,这类传感器具有灵敏度好,精度高等特点,电路工作范围为0-250℃,且具有良好的温度稳定性。 相似文献
34.
Weight smoothing to improve network generalization 总被引:2,自引:0,他引:2
A weight smoothing algorithm is proposed in this paper to improve a neural network's generalization capability. The algorithm can be used when the data patterns to be classified are presented on an n-dimensional grid (n>/=1) and there exists some correlations among neighboring data points within a pattern. For a fully-interconnected feedforward net, no such correlation information is embedded into the architecture. Consequently, the correlations can only be extracted through sufficient amount of network training. With the proposed algorithm, a smoothing constraint is incorporated into the objective function of backpropagation to reflect the neighborhood correlations and to seek those solutions that have smooth connection weights. Experiments were performed on problems of waveform classification, multifont alphanumeric character recognition, and handwritten numeral recognition. The results indicate that (1) networks trained with the algorithm do have smooth connection weights, and (2) they generalize better. 相似文献
35.
36.
经济利润率是评价一个实际热力装置的主要指标之一。将有限时间热力学,非平衡量子统计理论和yong经济学相结合,导出了量子斯特林制冷机的最大利润率以及对应的性能界限,其结果与实际斯特林制冷机的优化设计和模型评估提供了一个最佳的预选方案。 相似文献
37.
38.
A new hybrid active power filter (APF) topology 总被引:12,自引:0,他引:12
In this paper, a new hybrid active power filter topology is presented. A higher-voltage, low-switching frequency insulated gate bipolar transistor (IGBT) inverter and a lower-voltage high-switching frequency metal oxide semiconductor field effect transistor (MOSFET) inverter are used in combination to achieve harmonic current compensation. The function of the IGBT inverter is to support utility fundamental voltage and to compensate for the fundamental reactive power. The MOSFET inverter fulfills the function of harmonic current compensation. To further reduce cost and to simplify control, the IGBT and MOSFET inverters share the same DC-link via a split capacitor bank. With this approach harmonics can be cancelled over a wide frequency range. Compared to the conventional APF topology, the proposed approach employs lower dc-link voltage and generates less noise. Simulation and experimental results show that the proposed active power filter topology is capable of compensating for the load harmonics 相似文献
39.
Moss C.D. Teixeira F.L. Yang Y.E. Jin Au Kong 《Geoscience and Remote Sensing, IEEE Transactions on》2002,40(1):178-186
A three-dimensional (3D) finite-difference time-domain (FDTD) scheme is introduced to model the scattering from objects in continuous random media. FDTD techniques have been previously applied to scattering from random rough surfaces and randomly placed objects in a homogeneous background, but little has been done to simulate continuous random media with embedded objects where volumetric scattering effects are important. In this work, Monte Carlo analysis is used in conjunction with FDTD to study the scattering from perfectly electrically conducting (PEC) objects embedded in continuous random media. The random medium models under consideration are chosen to be inhomogeneous soils with a spatially fluctuating random permittivities and prescribed correlation functions. The ability of frequency averaging techniques to discriminate objects in this scenarion is also briefly investigated. The simulation scheme described in this work can be adapted and used to help in interpreting the scattered field data from targets in random environments such as geophysical media, biological media, or atmospheric turbulence 相似文献
40.