全文获取类型
收费全文 | 76172篇 |
免费 | 883篇 |
国内免费 | 696篇 |
专业分类
电工技术 | 1453篇 |
综合类 | 49篇 |
化学工业 | 11496篇 |
金属工艺 | 3477篇 |
机械仪表 | 2675篇 |
建筑科学 | 1674篇 |
矿业工程 | 505篇 |
能源动力 | 1951篇 |
轻工业 | 6523篇 |
水利工程 | 856篇 |
石油天然气 | 2338篇 |
武器工业 | 41篇 |
无线电 | 7375篇 |
一般工业技术 | 16756篇 |
冶金工业 | 12478篇 |
原子能技术 | 2637篇 |
自动化技术 | 5467篇 |
出版年
2022年 | 643篇 |
2021年 | 1000篇 |
2020年 | 762篇 |
2019年 | 831篇 |
2018年 | 1632篇 |
2017年 | 1638篇 |
2016年 | 1836篇 |
2015年 | 984篇 |
2014年 | 1616篇 |
2013年 | 3686篇 |
2012年 | 2449篇 |
2011年 | 2923篇 |
2010年 | 2429篇 |
2009年 | 2713篇 |
2008年 | 2673篇 |
2007年 | 2622篇 |
2006年 | 2230篇 |
2005年 | 1947篇 |
2004年 | 1866篇 |
2003年 | 1814篇 |
2002年 | 1717篇 |
2001年 | 1682篇 |
2000年 | 1682篇 |
1999年 | 1573篇 |
1998年 | 3673篇 |
1997年 | 2612篇 |
1996年 | 1943篇 |
1995年 | 1536篇 |
1994年 | 1335篇 |
1993年 | 1362篇 |
1992年 | 1003篇 |
1991年 | 1061篇 |
1990年 | 1077篇 |
1989年 | 1058篇 |
1988年 | 946篇 |
1987年 | 880篇 |
1986年 | 882篇 |
1985年 | 941篇 |
1984年 | 783篇 |
1983年 | 773篇 |
1982年 | 679篇 |
1981年 | 697篇 |
1980年 | 663篇 |
1979年 | 646篇 |
1978年 | 620篇 |
1977年 | 776篇 |
1976年 | 931篇 |
1975年 | 580篇 |
1974年 | 552篇 |
1973年 | 544篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
A. I. Nikolaev F. D. Larichkin O. A. Nikolaeva 《Theoretical Foundations of Chemical Engineering》2008,42(5):675-679
The main rules and principles which govern the choice of new variants for chemical technology of combined processing of titanium-rare-metal raw materials are considered. The existing variants of the technology are characterized from the viewpoint of their technological, economical, and ecological efficiency and social importance for a given region. A realistic choice of a technology from a large number of available variants should take into account the entire combination of their advantages and disadvantages The implementation of a rational technological scheme will result in the creation of economically profitable and efficient domestic production satisfying the demands of Russian industry in rare-metal and titanium materials. Directions are noted in which it is expedient to continue studies on designing a rational technology of loparite concentrate or some other concentrate. 相似文献
132.
Cross-linking additions of silicon carbide and waste material from ferroalloy production make it possible to increase the
heat-resistance index for mullite-containing refractories. For briquette specimens based on a charge containing aluminum powder
it reaches 45 thermal cycles (1300°C – water).
Translated from Novye Ogneupory, No. 11, pp. 44–46, November 2008. 相似文献
133.
K. O. Boltar I. D. Burlakov A. M. Filachev E. A. Klimanov V. P. Ponomarenko V. N. Solyakov V. I. Stafeev 《Optical Memory & Neural Networks》2007,16(4):234-247
The recent researches and technological developments of middle and long wavelength infrared HgCdTe photovoltaic detectors
are presented. Structure, topology, design and performance of HgCdTe photodiodes, silicon readout electronics, Focal Plane
Arrays both staring and time delay and integration types, thermal imagers are discussed. Negative differential conductance,
bistability and high frequency oscillations under background infrared radiation in HgCdTe photodiodes are reported. 相似文献
134.
A method is considered to solve a conditional optimization problem with a linear-fractional objective function over permutations.
The performance of sub algorithms to solve this problem is evaluated. The practical efficiency of the algorithm is analyzed
by conducting numerical experiments.
__________
Translated from Kibernetika i Sistemnyi Analiz, No. 4, pp. 133–146, July–August 2007. 相似文献
135.
E. P. Velikhov N. N. Ponomarev-Stepnoi V. G. Volkov G. G. Gorodetskii Yu. A. Zverkov O. P. Ivanov S. M. Koltyshev V. D. Muzrukova S. G. Semenov V. E. Stepanov A. V. Chesnokov A. D. Shisha 《Atomic Energy》2007,102(5):375-381
This article is devoted to work done in 2002–2006 as part of the unified project Reabilitatsiya to rehabilitate radiation
hazardous objects and sections of the radioactively contaminated territory of the Russian Science Center Kurchatov Institute.
The main objects of the rehabilitation work were old storage sites built for radioactive wastes on the territory of the Institute
when military and civilian nuclear technologies were under development. The structural features of the storage sites, including
the volumes and characteristics of the wastes stored, are presented. The salient aspects of the disposal sites, taken into
account during the rehabilitation work, are discussed. The organization of the rehabilitation operations and the sequence
in which they are performed, the special features of the technical design solutions used, the technological methods, and ways
for conducting the work are described.
__________
Translated from Atomnaya énergiya, Vol. 102, No. 5, pp. 300–306, May, 2007. 相似文献
136.
The results of the analysis of variations in the radiative recombination coefficient with varying doping level and concentration of excess electron-hole pairs are reported. It is shown that, along with the effect of narrowing of the band gap calculated in the many-electron approximation, the effect of screening of the Coulomb interaction responsible for the decrease in the excition binding energy should be taken into account. Both effects produce similar trends and decrease the radiative recombination coefficient with increasing levels of doping or injection. The contributions of excitonic radiative recombination and band-to-band radiative recombination to the total radiative recombination coefficient are separated from each other. It is shown that, in the region of room temperature, both contributions are comparable, while at liquid-nitrogen temperature, the excitonic component dominates over the band-to-band component. The results obtained by refined calculations of the limiting value of the internal quantum yield of electroluminescence for the silicon diodes and p-i-n structures are presented. It is shown that the internal quantum yield of electroluminescence can be as high as 14%. However, this values sharply decreases with increasing surface recombination rate and decreasing lifetime of excess charge carriers in the bulk. 相似文献
137.
We propose a new framework in wavelet video coding to improve the compression rate by exploiting the spatiotemporal regularity of the data. A sequence of images creates a spatiotemporal volume. This volume is said to be regular along the directions in which the pixels vary the least, hence the entropy is the lowest. The wavelet decomposition of regularized data results in a fewer number of significant coefficients, thus yielding a higher compression rate. The directions of regularity of an image sequence depend on both its motion content and spatial structure. We propose the representation of these directions by a 3-D vector field, which we refer to as the spatiotemporal regularity flow (SPREF). SPREF uses splines to approximate the directions of regularity. The compactness of the spline representation results in a low storage overhead for SPREF, which is a desired property in compression applications. Once SPREF directions are known, they can be converted into actual paths along which the data is regular. Directional decomposition of the data along these paths can be further improved by using a special class of wavelet basis called the 3-D orthonormal bandelet basis. SPREF -based video compression not only removes the temporal redundancy, but it also compensates for the spatial redundancy. Our experiments on several standard video sequences demonstrate that the proposed method results in higher compression rates as compared to the standard wavelet based compression. 相似文献
138.
139.
Rajoo R. Lim S.S. Wong E.H. Hnin W.Y. Seah S.K.W. Tay A.A.O. Iyer M. Tummala R.R. 《Advanced Packaging, IEEE Transactions on》2008,31(2):377-385
A wafer level packaging technique has been developed with an inherent advantage of good solder joint co-planarity suitable for wafer level testing. A suitable weak metallization scheme has also been established for the detachment process. During the fabrication process, the compliancy of the solder joint is enhanced through stretching to achieve a small shape factor. Thermal cycling reliability of these hourglass-shaped, stretch solder interconnections has been found to be considerably better than that of the conventional spherical-shaped solder bumps. 相似文献
140.
Porous carbon nanofibers are synthesized by CVD method from acetylene with use of iron-containing catalysts. Activation of the nanofibers in melted potassium hydroxide results in increasing surface area from initial 300–400 m2 g−1 to 1700 m2 g−1. As follows from XRD data, activated nanofibers do not contain regular packages of graphene layers, but retain high electric conductivity. Deposition of copper improves electrochemical hydrogen storing characteristics of carbon nanofibers. Carbon nanomaterials obtained can be used as hydrogen storing materials in batteries instead of hydride forming metals. 相似文献