全文获取类型
收费全文 | 95725篇 |
免费 | 1997篇 |
国内免费 | 929篇 |
专业分类
电工技术 | 1403篇 |
技术理论 | 1篇 |
综合类 | 3212篇 |
化学工业 | 13545篇 |
金属工艺 | 5533篇 |
机械仪表 | 3809篇 |
建筑科学 | 3234篇 |
矿业工程 | 940篇 |
能源动力 | 1393篇 |
轻工业 | 4425篇 |
水利工程 | 1497篇 |
石油天然气 | 1228篇 |
武器工业 | 184篇 |
无线电 | 10430篇 |
一般工业技术 | 17528篇 |
冶金工业 | 3170篇 |
原子能技术 | 398篇 |
自动化技术 | 26721篇 |
出版年
2024年 | 42篇 |
2023年 | 202篇 |
2022年 | 325篇 |
2021年 | 510篇 |
2020年 | 374篇 |
2019年 | 307篇 |
2018年 | 14718篇 |
2017年 | 13747篇 |
2016年 | 10281篇 |
2015年 | 1085篇 |
2014年 | 823篇 |
2013年 | 927篇 |
2012年 | 3898篇 |
2011年 | 10255篇 |
2010年 | 8947篇 |
2009年 | 6191篇 |
2008年 | 7370篇 |
2007年 | 8381篇 |
2006年 | 781篇 |
2005年 | 1800篇 |
2004年 | 1514篇 |
2003年 | 1547篇 |
2002年 | 875篇 |
2001年 | 450篇 |
2000年 | 517篇 |
1999年 | 410篇 |
1998年 | 385篇 |
1997年 | 257篇 |
1996年 | 251篇 |
1995年 | 223篇 |
1994年 | 172篇 |
1993年 | 107篇 |
1992年 | 105篇 |
1991年 | 81篇 |
1990年 | 37篇 |
1989年 | 40篇 |
1988年 | 47篇 |
1987年 | 27篇 |
1968年 | 43篇 |
1967年 | 33篇 |
1966年 | 42篇 |
1965年 | 44篇 |
1963年 | 28篇 |
1960年 | 30篇 |
1959年 | 37篇 |
1958年 | 37篇 |
1957年 | 36篇 |
1956年 | 34篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
Flocculation morphology is a new concept that investigates the morphological characteristics of colloidal particles and coagulants in water during the flocculation process, and the influence that these characteristics have on flocculation process efficiency. This paper is a summary of advances in research on this topic over several years. Morphological characteristics of colloids in natural waters and different kinds of hydrolysed coagulants are investigated, and their effect on colloid stability, flocculation kinetics and efficiency is analysed. It is confirmed that the traditional theory has some deviations in coagulation of nonspherical particles, and these deviations are revised by the flocculation morphology model. Flocculation morphology can not only promote research about flocculation theory, but also instruct the production, application and flocculation control. It can be foreseen that more progress will be made in research and application of flocculation morphology in the near future. 相似文献
104.
M. K. Bakhadyrkhanov O. É. Sattarov Kh. M. Iliev K. S. Ayupov Tuérdi Umaier 《Semiconductors》2005,39(7):789-791
It is experimentally ascertained that light stimulates the negative magnetoresistance observed in a high electric field in silicon doped with boron and manganese. The optimum conditions (the electric field, temperature, illumination, and resistivity of the material) for observation of the largest magnitude of negative magnetoresistance in (Si:B):Mn are determined. The dependence of the negative magnetoresistance on the concentration of compensating impurity is established. 相似文献
105.
This letter presents some further results on the local stability in equilibrium for Internet congestion control algorithm proposed by Low et al., (IEEE/ACM Transactions on Networking, 1999). The propagation delay d(t) is assumed to be time-varying and have maximum and minimum delay bounds (i.e., d/sub m//spl les/d(t)/spl les/d/sub M/), which is more general than the assumption (0相似文献
106.
The stress intensity factors for a short crack partially penetrating an inclusion of arbitrary shape
Some approximate solutions for predicting the stress intensity factor of a short crack penetrating an inclusion of arbitrary
shape have been developed under mode I and mode II loading conditions. The derivation of the fundamental formula is based
on the transformation toughening theory. The transformation strains in the inclusion are induced by the crack-tip field and
remotely applied stresses, and approximately evaluated by the Eshelby equivalent inclusion theory. As validated by detailed
finite element (FE) analyses, the developed solutions have good accuracy for different inclusion shape and for a wide range
of modulus ratio between inclusion and matrix material. 相似文献
107.
研究了用固体润滑石墨、碳化硅、二硫化钼等填料改性的聚苯硫醚 (PPS)涂层的耐磨性能。实验结果表明 ,聚苯硫醚复合涂层具有优良的耐磨性 ;加入适量 ( 3 0 % )的石墨、碳化硅等固体润滑剂 (石墨 :碳化硅 =2∶3 ) ,可以有效提高涂层的耐磨性能 ,而二硫化钼和三氧化二铬的减摩效果更佳 相似文献
108.
An overview of nondestructive evaluation methods 总被引:1,自引:0,他引:1
Marvin Trimm 《Journal of Failure Analysis and Prevention》2003,3(3):17-31
ondestructive evaluation is described as nondestructive testing (NDT), nondestructive inspection (NDI), and nondestructive
examination (NDE). The activities associated with the evaluation include testing, inspection, and examination and primarily
involve looking at (or through) and/or measuring some characteristic of an object. Frequently there is a desire to determine
some characteristic of the object or to determine whether the object contains irregularities, discontinuities, or flaws. These
examinations, inspections, or tests are used to determine the physical soundness of a material without impairing its usefulness.
Nondestructive evaluation is a powerful tool that can help assure safety, quality, and reliability; increase productivity;
decrease liability; protect the environment; and save money. In this article, nondestructive evaluation is represented by
the acronym NDE. 相似文献
109.
Nguyen An Tien I. Ya. Mittova O. V. Almjasheva S. A. Kirillova V. V. Gusarov 《Glass Physics and Chemistry》2008,34(6):756-761
Nanocrystalline LaFeO3 is prepared by the dehydration of coprecipitated lanthanum and iron(III) hydroxides. It is shown that the behavior of the samples during heating and the size distribution of LaFeO3 nanocrystals can be considerably different depending on the scheme used for coprecipitation of lanthanum and iron hydroxides; independently of the method employed for coprecipitation of the initial compounds, sintering of the samples at 950°C leads to the formation of lanthanum orthoferrite crystals up to 100 nm in size. 相似文献
110.
Vjacheslav V. Zuev 《Journal of Polymer Research》2008,15(5):351-356
Functionalized polyanilines containing biphenyl, terphenyl, carbazole, anthracene, and 4-n-hexylphenyl moieties were synthesized though the reaction of polyaniline in emeraldine base form with sodium salt of corresponding
vinylketoaromatics with quantitative yields. Polymers were characterized with Fourier transform infrared spectroscopy, proton
nuclear magnetic resonance spectroscopy, and thermogravimetry. The emission characteristics of these polymers in N-methyl-2-pyrrolidone solution were examined. The functionalized polyanilines exhibited an intense green emission. 相似文献