全文获取类型
收费全文 | 305707篇 |
免费 | 31927篇 |
国内免费 | 11190篇 |
专业分类
电工技术 | 16259篇 |
技术理论 | 11篇 |
综合类 | 15836篇 |
化学工业 | 57880篇 |
金属工艺 | 16063篇 |
机械仪表 | 17007篇 |
建筑科学 | 19431篇 |
矿业工程 | 6332篇 |
能源动力 | 7518篇 |
轻工业 | 23684篇 |
水利工程 | 5759篇 |
石油天然气 | 14089篇 |
武器工业 | 1874篇 |
无线电 | 36915篇 |
一般工业技术 | 48901篇 |
冶金工业 | 16722篇 |
原子能技术 | 6154篇 |
自动化技术 | 38389篇 |
出版年
2024年 | 1162篇 |
2023年 | 3840篇 |
2022年 | 7560篇 |
2021年 | 10553篇 |
2020年 | 8793篇 |
2019年 | 9131篇 |
2018年 | 10387篇 |
2017年 | 11702篇 |
2016年 | 11309篇 |
2015年 | 12944篇 |
2014年 | 15847篇 |
2013年 | 19567篇 |
2012年 | 18823篇 |
2011年 | 20128篇 |
2010年 | 17904篇 |
2009年 | 17358篇 |
2008年 | 16664篇 |
2007年 | 15826篇 |
2006年 | 14829篇 |
2005年 | 12351篇 |
2004年 | 9433篇 |
2003年 | 8896篇 |
2002年 | 9055篇 |
2001年 | 7951篇 |
2000年 | 6997篇 |
1999年 | 5973篇 |
1998年 | 4682篇 |
1997年 | 3953篇 |
1996年 | 3500篇 |
1995年 | 2998篇 |
1994年 | 2480篇 |
1993年 | 2082篇 |
1992年 | 1881篇 |
1991年 | 1588篇 |
1990年 | 1533篇 |
1989年 | 1339篇 |
1988年 | 1187篇 |
1987年 | 1033篇 |
1986年 | 934篇 |
1985年 | 859篇 |
1984年 | 811篇 |
1983年 | 729篇 |
1982年 | 734篇 |
1979年 | 776篇 |
1978年 | 811篇 |
1977年 | 775篇 |
1976年 | 810篇 |
1975年 | 729篇 |
1974年 | 738篇 |
1973年 | 745篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
131.
132.
Yu. A. Zolotukhin 《Coke and Chemistry》2008,51(8):291-296
The codification of coal in State Standard 25543-88 is compared with the international codification of coal of medium and high rank. The ranking of coking coal on the basis of State Standard GOST 25543-88 is evaluated. 相似文献
133.
A. E. Lapshin Yu. F. Shepelev Yu. I. Smolin E. A. Vasil’eva 《Glass Physics and Chemistry》2008,34(2):182-186
The distribution and structure of tellurium nanoclusters synthesized in crystal channels of the porous silica ZSM-11 are investigated
using the maximum-entropy method and the Rietveld analysis. It is shown that the intercalated tellurium atoms are arranged
in channels of the ZSM-11 zeolite not randomly but in the form of scraps of infinite chains similar to those observed in massive
tellurium. The distances between the nearest neighbor tellurium atoms vary in the range 2.53(4)–2.70(3) ?. The clusters Te4 are formed at the intersections of channels in the structure. These clusters have the form of distorted tetrahedra in which
the tellurium atoms are separated by distances of 2.53(4) and 2.90(4) ?.
Original Russian Text ? A.E. Lapshin, Yu.F. Shepelev, Yu.I. Smolin, E.A. Vasil’eva, 2008, published in Fizika i Khimiya Stekla. 相似文献
134.
135.
Tsang T.K.K. Kuan-Yu Lin El-Gamal M.N. 《Circuits and Systems II: Express Briefs, IEEE Transactions on》2008,55(3):214-218
This paper presents design techniques of CMOS ultra-wide-band (UWB) amplifiers for multistandard communications. The goal of this paper is to propose a compact, simple, and robust topology for UWB low-noise amplifiers, which yet consumes a relatively low power. To achieve this goal, a common-gate amplifier topology with a local feedback is employed. The first amplifier uses a simple inductive peaking technique for bandwidth extension, while the second design utilizes a two-stage approach with an added gain control feature. Both amplifiers achieve a flat bandwidth of more than 6 GHz and a gain of higher than 10 dB with supply voltages of 1.8-2.5 V. Designs with different metal thicknesses are compared. The advantage of using thick-metal inductors in UWB applications depends on the chosen topology. 相似文献
136.
Steensgaard J. Zhiqing Zhang Wenhuan Yu Sarhegyi A. Lucchese L. Dae-Ik Kim Temes G.C. 《IEEE transactions on circuits and systems. I, Regular papers》2008,55(5):1289-1296
Incremental data converters (IDCs) are useful in instrumentation and measurement applications, where low-frequency analog signals need to be converted into digital form with high accuracy and low power dissipation. They are particularly well suited for applications where a single analog-digital converter is multiplexed between many channels. This paper proposes an exact design methodology for IDCs, which optimizes the signal-to-noise ratio of the converter under practical design constraints. The process also allows the designer to apportion the noise budget in an arbitrary manner between thermal and quantization noise. The design process is illustrated by an example which describes the optimization of a third-order multiplexed IDC. 相似文献
137.
Eng Leong Tan Ding Yu Heh 《Microwave and Wireless Components Letters, IEEE》2008,18(5):296-298
This letter presents an unconditionally stable alternating direction implicit finite-difference time-domain (ADI-FDTD) method with fourth order accuracy in time. Analytical proof of unconditional stability and detailed analysis of numerical dispersion are presented. Compared to second order ADI-FDTD and six-steps SS-FDTD, the fourth order ADI-FDTD generally achieves lower phase velocity error for sufficiently fine mesh. Using finer mesh gridding also reduces the phase velocity error floor, which dictates the accuracy limit due to spatial discretization errors when the time step size is reduced further. 相似文献
138.
Yun‐Seok Cho Bheong‐Uk Lee Kye‐Heon Oh 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(9):1211-1217
BACKGROUND: Environmental contamination by nitroaromatic compounds such as 2,4,6‐trinitrotoluene (TNT), hexahydro‐1,3,5‐trinitro‐1,3,5‐s‐triazine (RDX), atrazine, and/or simazine (TRAS) generated as waste from military and agricultural activities is a serious worldwide problem. Microbiological treatment of these compounds is an attractive method because many explosives and herbicides are biodegradable and the process can be made cost‐effective. We explored the feasibility of using cultures of Pseudomonas putida HK‐6 for simultaneous degradation of TRAS with the aim of microbial application in wastewater treatment in bench‐scale bioreactors. RESULTS: Experiments were conducted to study the effects of supplemental carbons, nitrogens, and Tween‐80 on the degradation of Ps. putida HK‐6 in media containing TRAS as target substrate(s). The most effective TRAS degradation was shown in the presence of molasses. Addition of nitrogen sources produced a delayed effect for the target substrate(s). Tween‐80 enhanced the degradation of target substrate(s). Simultaneous degradation of these compounds proceeded to completion within the given period. CONCLUSIONS: Ps. putida HK‐6 was capable of growth with TRAS, and the effects of supplements on TRAS degradation and simultaneous TRAS degradation were evaluated in bench‐scale bioreactors. The results of this study have practical applications in the processes of industrial waste stream treatment where the disposal of TRAS may be problematic. Copyright © 2008 Society of Chemical Industry 相似文献
139.
Yu. V. Larichev D. A. Shlyapin P. G. Tsyrul’nikov V. I. Bukhtiyarov 《Catalysis Letters》2008,120(3-4):204-209
Sibunit-supported Ru-catalysts promoted with cesium or rubidium compounds have been comparatively studied with XPS. The cesium promoter interacts both with support and with active component. The absence of the promoter–support interaction in the case of rubidium provides a stronger interaction between promoter and active component compared to the cesium-based catalysts. These differences in the promoter–support and promoter–metal interactions are exhibited when a sequence of ruthenium and alkali introduction are changed. 相似文献
140.
A. V. Lyutetskii N. A. Pikhtin S. O. Slipchenko N. V. Fetisova A. Yu. Leshko E. G. Golikova Yu. A. Ryaboshtan I. S. Tarasov 《Technical Physics Letters》2003,29(4):290-293
Separate confinement InGaAsP/InP laser heterostructures were grown by metalorganic-hydride vapor-phase epitaxy. High-power single-mode laser diodes of mesastripe design based on these heterostructures operate in a wavelength interval of 1.7–1.8 μm with a maximum continuous room temperature output power of 150 mW. The single-mode lasing regime is maintained up to an output power level of 100 mW. 相似文献