全文获取类型
收费全文 | 36304篇 |
免费 | 4029篇 |
国内免费 | 1163篇 |
专业分类
电工技术 | 7571篇 |
技术理论 | 1篇 |
综合类 | 2744篇 |
化学工业 | 3011篇 |
金属工艺 | 1232篇 |
机械仪表 | 3263篇 |
建筑科学 | 1477篇 |
矿业工程 | 1582篇 |
能源动力 | 1046篇 |
轻工业 | 2100篇 |
水利工程 | 464篇 |
石油天然气 | 1185篇 |
武器工业 | 695篇 |
无线电 | 5679篇 |
一般工业技术 | 2944篇 |
冶金工业 | 1048篇 |
原子能技术 | 351篇 |
自动化技术 | 5103篇 |
出版年
2025年 | 275篇 |
2024年 | 1036篇 |
2023年 | 868篇 |
2022年 | 1027篇 |
2021年 | 1239篇 |
2020年 | 1399篇 |
2019年 | 1089篇 |
2018年 | 910篇 |
2017年 | 1201篇 |
2016年 | 1368篇 |
2015年 | 1492篇 |
2014年 | 2291篇 |
2013年 | 1991篇 |
2012年 | 2576篇 |
2011年 | 2582篇 |
2010年 | 1932篇 |
2009年 | 1952篇 |
2008年 | 1734篇 |
2007年 | 2299篇 |
2006年 | 1984篇 |
2005年 | 1750篇 |
2004年 | 1436篇 |
2003年 | 1360篇 |
2002年 | 1071篇 |
2001年 | 928篇 |
2000年 | 802篇 |
1999年 | 631篇 |
1998年 | 472篇 |
1997年 | 367篇 |
1996年 | 327篇 |
1995年 | 240篇 |
1994年 | 204篇 |
1993年 | 153篇 |
1992年 | 147篇 |
1991年 | 89篇 |
1990年 | 69篇 |
1989年 | 55篇 |
1988年 | 45篇 |
1987年 | 20篇 |
1986年 | 16篇 |
1985年 | 15篇 |
1984年 | 10篇 |
1983年 | 11篇 |
1982年 | 9篇 |
1980年 | 4篇 |
1974年 | 2篇 |
1962年 | 2篇 |
1959年 | 3篇 |
1955年 | 3篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
介绍了有机EL在稳定性及寿命方面的最新研究动态,着重描述了器件功能层组合的相互接触、阴极、空穴传输层玻璃化温度和驱动条件等对有机EL稳定性和寿命的影响。 相似文献
2.
An effective system control method is presented for applying a three‐phase current‐source PWM converter with a deadbeat controller to active power filters (APFs). In the shunt‐type configuration, the APF is controlled such that the current drawn by the APF from the utility is equal to the current harmonics and reactive current required for the load. To attain the time‐optimal response of the APF supply current, a two‐dimensional deadbeat control scheme is applied to APF current control. Furthermore, in order to cancel both the delay in the two‐dimensional deadbeat control scheme and the delay in DSP control strategy, an Adaptive Line Enhancer (ALE) is introduced in order to predict the desired value three sampling periods ahead. ALE has another function of bringing robustness to the deadbeat control system. Due to the ALE, settling time is made short in a transient state. On the other hand, total harmonic distortion (THD) of source currents can be minimized compared to the case where ideal identification of the controlled system can be made. The experimental results obtained from the DSP‐based APF are also reported. The compensating ability of this APF is very high in accuracy and responsiveness although the modulation frequency is rather low. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(1): 50–61, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20014 相似文献
3.
Because of its high–temperature chemical stability, SiC ceramic is a promising material for high-temperature device applications such as thermoelectric energy converters. However, the electrical conductivity of SiC ceramic is too low for it to be used as a thermoelectric energy converter at the cold junction. Therefore, we propose a SiC-Si functionally gradient material (FGM) in order to improve the electrical conductivity of the SiC ceramic at the cold junction. An SiC rod was fired in a temperature gradient furnace. One end of the SiC rod was maintained at 2473 K and the other end was maintained at 1973 K for 30 min. After firing, the porous SiC edge fired at 1973 K was dipped into molten Si in order to infiltrate molten Si into the porous SiC. The microstructure of the FGM is classified into three regions: the SiC-Si composite material; the porous SiC ceramic; and the densified SiC ceramic. The electrical conductivity, the Seebeck coefficient and the thermal conductivity for each region of SiC-Si FGM was measured at 300 K; a figure of merit was calculated. The figure of merit of the SiC-Si FGM at the cold junction, at room temperature, was 108 times higher than that of a nongradient SiC ceramic. 相似文献
4.
T. RONALD A. MAGEE CAROLE P.D. WILKINSON 《International Journal of Food Science & Technology》1992,27(5):541-549
Investigation of the effects of varying air velocity, slice thickness, and pre-treatment with sodium chloride solutions and surface active agents on drying potato slices indicated that the drying occurred entirely in the falling rate period and was controlled by the mechanism of liquid diffusion. The rate of drying, and therefore the diffusion coefficients, increased with the addition of sodium chloride and surface active agents. Diffusion coefficients were also influenced by air velocity and slice thickness, suggesting that the rate of drying of potato slices is controlled by a combination of internal and external resistances. 相似文献
5.
介绍了橡胶工业橡制品生产中胶坯制备的三种方法,其中详细介绍了精密预成型机制备胶坯。以上海德仁橡塑机械有限公司物精密预成型机为例,从结构,性能及工艺参数等方面进行了分析,说明精密预成型机是批量生产橡胶模型制品的一种得力辅助设备。 相似文献
6.
新型城镇化背景下欠发达地区传统文化保护的关键取决于其能否在保护文化资本和环境资本的基础上,实现经济资本的提升、文化价值观念及生活方式的转变.通过对张家口市下花园区段家堡村传统文化的调查研究,提出转变观念,主动保护、挖掘和丰富欠发达地区传统文化特色,提升旅游开发优势,带动地区经济发展,实现新型城镇化的同时更好地保护传统文化. 相似文献
7.
在目标检测与提取中,传统的蛇模型和基于活动轮廓的局部区域检测方法受到初始条件或者自身的收敛性约束的影响,不仅时间花费多,而且不具备鲁棒性。本文提出一种基于C V模型的变分水平集的目标检测与提取方法,通过大量实验验证,在花费时间和鲁棒性上得到了显著的改善。 相似文献
8.
Chengkun Xu Richard Killmeyer McMahan L. Gray Shahed U.M. Khan 《Applied catalysis. B, Environmental》2006,64(3-4):312-317
The present research focused on wet process synthesis of visible light active carbon-modified (CM)-n-TiO2 nanoparticles and their photocatalytic activity. The CM-n-TiO2 was synthesized by hydrolysis of TiCl4 in the presence of tetrabutylammonium hydroxide and also in the presence of glucose and sodium hydroxide. UV–vis spectra, X-ray diffraction (XRD), and FT-IR were used to characterize these photocatalysts. It was found that the CM-n-TiO2 nanoparticles synthesized by hydrolysis with tetrabutylammonium hydroxide or with sodium hydroxide and glucose when subjected to extended aging and subsequent calcinations absorb well into the visible to near infrared region up to 800 nm and exhibit enhanced visible light photocatalytic activity on degradation of 4-chlorophenol. CM-n-TiO2 synthesized using glucose as the carbon source generated 13-fold increase in the initial rate of photodegradation of 4-chlorophenol compared to those by regular n-TiO2, whereas, it increased only eight-fold when tetrabutylammonium hydroxide was used as the carbon source. 相似文献
9.
《国际计算机数学杂志》2012,89(17):2374-2384
In this paper, we derive the piecewise linear system (PLS) associated with the bilateral obstacle problem and illustrate the equivalence between the linear system and finite-dimensional complementary problem. The existence and the uniqueness of the solution to the PLS are also demonstrated. Based on the PLS, a Picard iterative algorithm is proposed. The convergence analysis is given and examples are presented to verify the effectiveness of the method. 相似文献
10.
金鸡滩2号机组在运行中出现了油压装置压油泵频繁打油,受油器下游侧端盖与挡油环、端盖与小轴相互碰刮的异常运行情况,文章对此异常情况进行了分析并介绍了故障的排查处理过程,对类似机组的相同故障处理有借鉴作用。 相似文献