全文获取类型
收费全文 | 156901篇 |
免费 | 12012篇 |
国内免费 | 6575篇 |
专业分类
电工技术 | 8878篇 |
技术理论 | 9篇 |
综合类 | 9924篇 |
化学工业 | 25261篇 |
金属工艺 | 9076篇 |
机械仪表 | 9344篇 |
建筑科学 | 12282篇 |
矿业工程 | 3857篇 |
能源动力 | 4061篇 |
轻工业 | 9611篇 |
水利工程 | 2747篇 |
石油天然气 | 7758篇 |
武器工业 | 1157篇 |
无线电 | 16999篇 |
一般工业技术 | 18080篇 |
冶金工业 | 6907篇 |
原子能技术 | 1874篇 |
自动化技术 | 27663篇 |
出版年
2024年 | 582篇 |
2023年 | 2315篇 |
2022年 | 4014篇 |
2021年 | 5608篇 |
2020年 | 4240篇 |
2019年 | 3631篇 |
2018年 | 4063篇 |
2017年 | 4614篇 |
2016年 | 4197篇 |
2015年 | 5617篇 |
2014年 | 7205篇 |
2013年 | 8716篇 |
2012年 | 10050篇 |
2011年 | 13096篇 |
2010年 | 9919篇 |
2009年 | 9382篇 |
2008年 | 8884篇 |
2007年 | 8326篇 |
2006年 | 8486篇 |
2005年 | 7659篇 |
2004年 | 5439篇 |
2003年 | 5023篇 |
2002年 | 4783篇 |
2001年 | 3890篇 |
2000年 | 3780篇 |
1999年 | 3963篇 |
1998年 | 3292篇 |
1997年 | 2648篇 |
1996年 | 2580篇 |
1995年 | 2145篇 |
1994年 | 1783篇 |
1993年 | 1294篇 |
1992年 | 1023篇 |
1991年 | 804篇 |
1990年 | 589篇 |
1989年 | 483篇 |
1988年 | 396篇 |
1987年 | 263篇 |
1986年 | 191篇 |
1985年 | 135篇 |
1984年 | 111篇 |
1983年 | 62篇 |
1982年 | 66篇 |
1981年 | 59篇 |
1980年 | 39篇 |
1979年 | 14篇 |
1976年 | 8篇 |
1975年 | 7篇 |
1959年 | 4篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
Hogari K. Tetsutani S. Jian Zhou Yamamoto F. Sato K. 《Lightwave Technology, Journal of》2003,21(2):540-545
Many cables containing 1.3-/spl mu/m zero-dispersion single-mode (SM) optical fibers are installed in trunk and access networks. Recently, there have been a number of studies on wavelength-division-multiplexing (WDM) systems designed to increase transmission capacity and flexibility. If we can construct WDM systems using SM optical-fiber cable networks designed to transmit using wavelengths in the 1.3-/spl mu/m window (O-band), this will prove very effective in reducing construction costs. It is therefore important to examine the wavelength dependence of the transmission characteristics of SM optical-fiber cables and networks that have already been installed and in which several optical fibers are joined. In this paper, we describe the measured optical characteristics of SM optical-fiber cables and installed optical-fiber cable networks at various wavelengths. The optical characteristics were stable in the 1.46 to 1.625-/spl mu/m wavelength range and we confirmed that the installed SM optical-fiber cable networks could be used for WDM system applications. 相似文献
3.
Shi-Jin Ding Hang Hu Lim H.F. Kim S.J. Yu X.F. Chunxiang Zhu Li M.F. Byung Jin Cho Chan D.S.H. Rustagi S.C. Yu M.B. Chin A. Dim-Lee Kwong 《Electron Device Letters, IEEE》2003,24(12):730-732
For the first time, we successfully fabricated and demonstrated high performance metal-insulator-metal (MIM) capacitors with HfO/sub 2/-Al/sub 2/O/sub 3/ laminate dielectric using atomic layer deposition (ALD) technique. Our data indicates that the laminate MIM capacitor can provide high capacitance density of 12.8 fF//spl mu/m/sup 2/ from 10 kHz up to 20 GHz, very low leakage current of 3.2 /spl times/ 10/sup -8/ A/cm/sup 2/ at 3.3 V, small linear voltage coefficient of capacitance of 240 ppm/V together with quadratic one of 1830 ppm/V/sup 2/, temperature coefficient of capacitance of 182 ppm//spl deg/C, and high breakdown field of /spl sim/6 MV/cm as well as promising reliability. As a result, the HfO/sub 2/-Al/sub 2/O/sub 3/ laminate is a very promising candidate for next generation MIM capacitor for radio frequency and mixed signal integrated circuit applications. 相似文献
4.
通过对相变增韧陶瓷及一种可切削玻璃-陶瓷动态疲劳(恒应力速率)试验中高应力速率区断裂应力下降现象的理论分析,发现这种现象与材料的阻力特性(R-curve)密切相关。确立的σ_f-σ理论关系能够很好地描述整个应力速率区间内的动态疲劳试验结果。高应力速率区σ_f-σ在双对数坐标下为负斜率直线,直线斜率为(m为阻力曲线KR=k(△a)~m的指数),断裂主要由材料阻力行为控制;低应力速率区,σ_f-σ在双对数坐标下为正斜率直线,直线斜率为 (n为应力腐蚀指数),断裂主要由材料应力腐蚀行为控制。建立了测定材料阻力特性的一种新方法,分别用这种方法及压痕/弯曲方法对一种可切削玻璃-陶瓷的阻力特性进行了实验测定,两种方法所得结果有很好的一致性。 相似文献
5.
本文提出新型布线算法,集李氏迷宫法与线搜索法的长处为一体,以饱和带法进行动态排序,以线搜索法确定借孔位置,然后用李氏法进行单层布线,获得最佳路径,从而达到线型好,布通率高的效果。 相似文献
7.
The cooling and solidification of melted drops during their movement in an immiscible cooling medium is widely employed for granulation in the chemical industry, and a study of these processes to provides a basis for the design of the granulation tower height and the temperature of the cooling medium is reported. A physical model of the cooling and solidification of the drop is established and the numerical calculation is performed. The influences of the key factors in the solidification, i.e., Bi number, drop diameter, temperature of the cooling medium, etc. are presented. The cooling and solidification during wax granulation in a water‐cooling tower and during urea granulation in an air‐cooling tower (spraying tower) are described in detail. Characteristics of the solidification and temperature distribution within the particle at different times are shown. The model and calculations can be used for structure design of the granulation tower and optimization of the operation parameters. 相似文献
8.
Biodegradable multiblock poloxamers (BMPs) with gel duration of 8 h to several weeks were prepared by varying their molecular weights from 4000 to 40 000 g mol?1. The molecular weight of the BMP was controlled by changing the poloxamer to coupling agent ratio. Assuming a micelle packing model of the BMP gel, as in the case of a poloxamer gel, the micelle properties and critical gel concentration of BMPs were investigated on the basis of the scaling concept. The findings suggest that the control of molecular weight by hydrolyzable groups can be a facile approach to optimize the gel properties for biomedical applications. Copyright © 2005 Society of Chemical Industry 相似文献
9.
The RPE (recursive prediction error) method in state-space form is developed in the nonlinear systems and extended to include the exact form of a nonlinearity, thus enabling structure preservation for certain classes of nonlinear systems. Both the discrete and the continuous-discrete versions of the algorithm in an innovations model are investigated, and a nonlinear simulation example shows a quite convincing performance of the filter as combined parameter and state estimator 相似文献
10.
利用引进的制造技术和设备,制作出了 APT(STLRI)—1.78型系列化光纤连接器。 相似文献