全文获取类型
收费全文 | 1726篇 |
免费 | 75篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 24篇 |
综合类 | 2篇 |
化学工业 | 501篇 |
金属工艺 | 68篇 |
机械仪表 | 66篇 |
建筑科学 | 68篇 |
矿业工程 | 3篇 |
能源动力 | 95篇 |
轻工业 | 127篇 |
水利工程 | 24篇 |
石油天然气 | 29篇 |
无线电 | 205篇 |
一般工业技术 | 283篇 |
冶金工业 | 135篇 |
原子能技术 | 9篇 |
自动化技术 | 173篇 |
出版年
2023年 | 19篇 |
2022年 | 42篇 |
2021年 | 55篇 |
2020年 | 52篇 |
2019年 | 80篇 |
2018年 | 68篇 |
2017年 | 40篇 |
2016年 | 52篇 |
2015年 | 44篇 |
2014年 | 63篇 |
2013年 | 135篇 |
2012年 | 77篇 |
2011年 | 99篇 |
2010年 | 68篇 |
2009年 | 70篇 |
2008年 | 65篇 |
2007年 | 63篇 |
2006年 | 60篇 |
2005年 | 38篇 |
2004年 | 32篇 |
2003年 | 36篇 |
2002年 | 35篇 |
2001年 | 28篇 |
2000年 | 18篇 |
1999年 | 24篇 |
1998年 | 30篇 |
1997年 | 26篇 |
1996年 | 19篇 |
1995年 | 26篇 |
1994年 | 16篇 |
1993年 | 19篇 |
1992年 | 27篇 |
1991年 | 28篇 |
1990年 | 20篇 |
1989年 | 14篇 |
1988年 | 15篇 |
1987年 | 15篇 |
1986年 | 11篇 |
1985年 | 20篇 |
1984年 | 21篇 |
1983年 | 21篇 |
1982年 | 14篇 |
1981年 | 9篇 |
1980年 | 17篇 |
1979年 | 7篇 |
1976年 | 9篇 |
1973年 | 7篇 |
1971年 | 10篇 |
1970年 | 8篇 |
1966年 | 6篇 |
排序方式: 共有1812条查询结果,搜索用时 15 毫秒
1.
2.
Silicon - Thin film nanocomposites of sodium silicate (80 SiO2 –20 Na2O)/ tartrazine dye (E102) prepared using sol gel process in acidic system. The change in the physicochemical properties... 相似文献
3.
Goel S. Elgamel M.A. Bayoumi M.A. Hanafy Y. 《IEEE transactions on circuits and systems. I, Regular papers》2006,53(4):867-878
Scaling down to deep submicrometer (DSM) technology has made noise a metric of equal importance as compared to power, speed, and area. Smaller feature size, lower supply voltage, and higher frequency are some of the characteristics for DSM circuits that make them more vulnerable to noise. New designs and circuit techniques are required in order to achieve robustness in presence of noise. Novel methodologies for designing energy-efficient noise-tolerant exclusive-OR-exclusive- NOR circuits that can operate at low-supply voltages with good signal integrity and driving capability are proposed. The circuits designed, after applying the proposed methodologies, are characterized and compared with previously published circuits for reliability, speed and energy efficiency. To test the driving capability of the proposed circuits, they are embedded in an existing 5-2 compressor design. The average noise threshold energy (ANTE) is used for quantifying the noise immunity of the proposed circuits. Simulation results show that, compared with the best available circuit in literature, the proposed circuits exhibit better noise-immunity, lower power-delay product (PDP) and good driving capability. All of the proposed circuits prove to be faster and successfully work at all ranges of supply voltage starting from 3.3 V down to 0.6 V. The savings in the PDP range from 94% to 21% for the given supply voltage range respectively and the average improvement in the ANTE is 2.67X. 相似文献
4.
Due to the demand for real time wavelet processors in applications such as video compression [1], Internet communications compression [2], object recognition [3], and numerical analysis, many architectures for the Discrete Wavelet Transform (DWT) systems have been proposed. This paper surveys the different approaches to designing DWT architectures. The types of architectures depend on whether the application is 1-D, 2-D, or 3-D, as well as the style of architecture: systolic, semi-systolic, folded, digit-serial, etc. This paper presents an overview and evaluation of the architectures based on the criteria of latency, control, area, memory, and number of multipliers and adders. This paper will give the reader an indication of the advantages and disadvantages of each design. 相似文献
5.
6.
7.
The corrosion behaviour of tin in different concentrations of citric acid solutions (0.3–1.0 M, pH=1.8) was studied at 30 °C by potentiodynamic technique. The E/I profiles exhibit an active passive behaviour. The active dissolution involves one anodic peak A associated with a dissolution of the metals as Sn(II) species. The passivity is due to the formation of thin film of SnO2 and or Sn(OH)4 on the anode surface. The cathodic sweep shows a small peak C related to the reduction of the passive film. The peak current density Ip of peak A increases with increasing both acid concentration and sweep rate.
The effects of adding increasing concentrations of Na2CrO4, NaMoO4, NaNO3 and NaNO2 on the corrosion of tin in 0.5 M citric acid at 30 °C were investigated. Both CrO42− and MoO42− ions inhibit the corrosion of tin and the extent of inhibition enhances with their concentrations. Addition of either NO3− or NO2− accelerates the corrosion of tin. NO3− ions are more aggressive than NO2− ions. 相似文献
8.
A two-dimensional cross-section finite difference model is presented to simulate density dependent leachate migration in leaky aquifers. Unlike existing models, a new approach is adopted to couple the groundwater-flow equation and the hydrodynamic dispersion equation with the elimination of the intermediate step of calculating velocities. The concept of the reference density is employed, permitting increased accuracy (over pressure-based models) in the representation of the transport process. The model is then used to study the effect of several hydraulic and transport parameters on the flow pattern and plume migration which are found to be very sensitive to most of these parameters. Equiconcentration and equipotential lines are overlapped to provide a better understanding of the coupling effect. 相似文献
9.
John D. Fitzsimons Bill Williston Georgina Williston Lisa Brown Abdel El-Shaarawi Lenore Vandenbyllaardt Dale Honeyfeld Don Tillitt Martha Wolgamood Scott B. Brown 《Journal of Great Lakes research》2007,33(1):93-103
Alewives (Alosa pseudoharengus), the major prey fish for Lake Ontario, contain thiaminase. They are associated with development of a thiamine deficiency in salmonines which greatly increases the potential for developing an early mortality syndrome (EMS). To assess the possible effects of thiamine deficiency on salmonine reproduction we measured egg thiamine concentrations for five species of Lake Ontario salmonines. From this we estimated the proportion of families susceptible to EMS based on whether they were below the ED20, the egg thiamine concentration associated with 20% mortality due to EMS. The ED20s were 1.52, 2.63, and 2.99 nmol/g egg for Chinook salmon (Oncorhynchus tshawytscha), lake trout (Salvelinus namaycush), and coho salmon (Oncorhynchus kisutch), respectively. Based on the proportion of fish having egg thiamine concentrations falling below the ED20, the risk of developing EMS in Lake Ontario was highest for lake trout, followed by coho (O. kisutch), and Chinook salmon, with the least risk for rainbow trout (O. mykiss). For lake trout from western Lake Ontario, mean egg thiamine concentration showed significant annual variability during 1994 to 2003, when the proportion of lake trout at risk of developing EMS based on ED20 ranged between 77 and 100%. Variation in the annual mean egg thiamine concentration for western Lake Ontario lake trout was positively related (p < 0.001, r2 = 0.94) with indices of annual adult alewife biomass. While suggesting the possible involvement of density-dependent changes in alewives, the changes are small relative to egg thiamine concentrations when alewife are not part of the diet and are of insufficient magnitude to allow for natural reproduction by lake trout. 相似文献
10.
Nonionic organic contaminants such as phenol, benzene, and toluene from contaminated wastewater on laboratory scale can be effectively sorbed by cellulosic wood pulp sheet incorporated with three polar functional groups. The synthesis was carried out by graft copolymerization reaction of N,N‐dimethylaminoethylmethacrylate with methacrylic acid onto wood pulp. The preparation conditions at which the grafting process proceeds homogeneously are determined. Characterization and some selected properties of the original and grafted wood pulp were evaluated using FTIR and scanning electron microscope, also, the removal of phenol, benzene, and toluene on laboratory scale was investigated by using gas chromatography. It was found that phenol shows the highest removal percent than that of benzene and toluene. The efficiency of removal of the nonionic contaminants is found to be 97%, which shows a great promise for its applicability in the removal of organic contaminates from wastewater. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3589–3595, 2006 相似文献