全文获取类型
收费全文 | 8914篇 |
免费 | 752篇 |
国内免费 | 395篇 |
专业分类
电工技术 | 522篇 |
综合类 | 511篇 |
化学工业 | 1511篇 |
金属工艺 | 468篇 |
机械仪表 | 486篇 |
建筑科学 | 721篇 |
矿业工程 | 245篇 |
能源动力 | 345篇 |
轻工业 | 848篇 |
水利工程 | 212篇 |
石油天然气 | 411篇 |
武器工业 | 47篇 |
无线电 | 950篇 |
一般工业技术 | 1150篇 |
冶金工业 | 473篇 |
原子能技术 | 98篇 |
自动化技术 | 1063篇 |
出版年
2024年 | 37篇 |
2023年 | 128篇 |
2022年 | 244篇 |
2021年 | 361篇 |
2020年 | 288篇 |
2019年 | 235篇 |
2018年 | 259篇 |
2017年 | 272篇 |
2016年 | 277篇 |
2015年 | 338篇 |
2014年 | 416篇 |
2013年 | 548篇 |
2012年 | 575篇 |
2011年 | 637篇 |
2010年 | 555篇 |
2009年 | 535篇 |
2008年 | 506篇 |
2007年 | 531篇 |
2006年 | 476篇 |
2005年 | 394篇 |
2004年 | 296篇 |
2003年 | 246篇 |
2002年 | 230篇 |
2001年 | 176篇 |
2000年 | 204篇 |
1999年 | 223篇 |
1998年 | 199篇 |
1997年 | 159篇 |
1996年 | 141篇 |
1995年 | 112篇 |
1994年 | 92篇 |
1993年 | 86篇 |
1992年 | 63篇 |
1991年 | 51篇 |
1990年 | 32篇 |
1989年 | 38篇 |
1988年 | 25篇 |
1987年 | 17篇 |
1986年 | 13篇 |
1985年 | 14篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1978年 | 4篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
The moisture effect on the indentation force deflection (IFD) of flexible polyurethane foam was examined through the curing of the foam with different moisture contents. The employed foam was cured at 30, 40, 50, 60, 70, and 80% relative humidity, and the corresponding curing temperature was constant at 23°C. The experiments showed that the measured IFD and support factor of the flexible polyurethane foam decreased, and the hysteresis increased with the curing moisture. A statistical conversion formula was generated experimentally to correct the measured IFD of the flexible polyurethane foam to eliminate the deviation caused by the moisture effect. The measured IFD was inversely exponentially proportional to the curing moisture. The accuracy of the correction formula was verified by the conditioning of the foam again with different moisture contents. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1679–1682, 2007 相似文献
952.
Material Growth and Device Fabrication of GaAs Based 1.3μm GaInNAs Quantum Well Laser Diodes 总被引:3,自引:3,他引:0
Niu Zhichuan Han Qin Ni Haiqiao Yang Xiaohong Xu Yingqiang Du Yun Zhang Shiyong Peng Hongling Zhao Huan Wu Donghai Li Sh 《半导体学报》2005,26(9):1860-1864
Material growth and device fabrication of the first 1.3μm quantum well (QW) edge emitting laser diodes in China are reported.Through the optimization of the molecular beam epitaxy (MBE) growth conditions and the tuning of the indium and nitrogen composition of the GaInNAs QWs,the emission wavelengths of the QWs can be tuned to 1.3μm.Ridge geometry waveguide laser diodes are fabricated.The lasing wavelength is 1.3μm under continuous current injection at room temperature with threshold current of 1kA/cm2 for the laser diode structures with the cleaved facet mirrors.The output light power over 30mW is obtained. 相似文献
953.
车用内燃机试验台架高弹性联轴器的设计 总被引:1,自引:0,他引:1
介绍了内燃机试验台架用内燃机与测功器联轴器的种类,分析了这些联轴器的性能及使用状况,对试验中架用高弹性联轴器进行匹配设计。 相似文献
954.
高浓度恒定固液两相流运动机理探析:Ⅱ.应用 总被引:5,自引:2,他引:3
低浓度和高浓度固液两相流运动可以通过微观动理论加以描述[1].本文在文献[1]的基础上,探讨固液两相流在低浓度和高浓度情形下的应用方法,以颗粒浓度垂线分布为例进行分析,获得了满意的结果,也揭示了高浓度固液两相流的一些特点. 相似文献
955.
956.
The effect of low temperature blanching on firmness of eight vegetables was studied. Preheating vegetables at low temperatures prior to a conventional blanch resulted in firmer products. Temperature and time had significant effects on texture, with temperature the most influential. Under optimal conditions, firmness improvements in preheated vegetables as compared to blanched controls were: Bok choy—3.0 × (65 °C, 45 min); Chinese cabbage—1.8 × (55 °C, 45 min); cabbage—1.6 × (65 °C, 15 min); green bell peppers—1.36 × (70 °C, 15 min); sugar snap peas—1.7 × (65 °C, 30 min); carrots—2.1 × (60 °C, 15 min) and broccoli—2.9 × (60 °C, 15 min). Thermal stability and optimal temperature for pectin methylesterase in homogenates from these vegetables were also analyzed. The relationship between optimum preheating conditions for textural integrity and pectin methylesterase activity is discussed. 相似文献
957.
The effect of the coherence time of light sources on the performance of an incoherent temporal-spreading optical-code-division multiple-access (OCDMA) system is studied in this paper. Broadband noise-like light sources, such as amplified spontaneous emission (ASE) sources, are used by the transmitters. Three different kinds of receiver structures are examined and compared. Results show the impact of the nonideal light sources on the system performances relative to the ideal case. Analysis shows that to achieve the best performance when the available optical bandwidth and data rate are fixed, there is an optimal range for the spreading code length. 相似文献
958.
959.
Design of hexagonal filter with source-load coupling 总被引:1,自引:0,他引:1
A method for synthesising a novel hexagonal filter with source-load coupling is presented. The equivalent circuit of the lowpass prototype of a general lossless coupled resonator filter is proposed, and the corresponding transfer function t(s) is derived. A novel quasi-elliptic function microstrip hexagonal filter is designed and fabricated. Simulated and measured results are presented. Compared with the conventional cross-coupling filter, the proposed hexagonal filter acquires more than 27.5% size reduction and provides improved selectivity by a relatively small bandwidth 相似文献
960.
高压水射流凿岩过程的理论研究 总被引:1,自引:0,他引:1
基于高压水射流凿岩试验结果、岩石内孔隙流体的运动规律以及水射流凿岩过程中能量分布变化趋势的分析,对高压水射流凿岩过程进行了系统的研究。研究结果表明,在水射流凿岩过程中射流和岩石的相互作用以界面耦合为主,水射流的冲击载荷在岩石内产生的应力波和射流准静态压力的共同作用使得岩石破碎,其中应力波的作用占主导地位。高压水射流凿岩过程可分为两个阶段,初期以应力波作用为主,形成岩石损伤破坏的主体;后期主要是射流的准静态压力使得岩石内已有的微孔隙、微裂纹等损伤继续扩展,并汇聚形成宏观破坏,从而使岩石孔眼的直径扩大。 相似文献