全文获取类型
收费全文 | 1779篇 |
免费 | 18篇 |
国内免费 | 38篇 |
专业分类
电工技术 | 23篇 |
综合类 | 82篇 |
化学工业 | 278篇 |
金属工艺 | 62篇 |
机械仪表 | 96篇 |
建筑科学 | 189篇 |
矿业工程 | 37篇 |
能源动力 | 149篇 |
轻工业 | 69篇 |
水利工程 | 11篇 |
石油天然气 | 108篇 |
武器工业 | 3篇 |
无线电 | 159篇 |
一般工业技术 | 265篇 |
冶金工业 | 27篇 |
原子能技术 | 118篇 |
自动化技术 | 159篇 |
出版年
2024年 | 1篇 |
2023年 | 8篇 |
2022年 | 20篇 |
2021年 | 26篇 |
2020年 | 42篇 |
2019年 | 25篇 |
2018年 | 35篇 |
2017年 | 39篇 |
2016年 | 45篇 |
2015年 | 45篇 |
2014年 | 91篇 |
2013年 | 122篇 |
2012年 | 84篇 |
2011年 | 184篇 |
2010年 | 105篇 |
2009年 | 93篇 |
2008年 | 91篇 |
2007年 | 101篇 |
2006年 | 86篇 |
2005年 | 67篇 |
2004年 | 73篇 |
2003年 | 68篇 |
2002年 | 60篇 |
2001年 | 41篇 |
2000年 | 36篇 |
1999年 | 32篇 |
1998年 | 32篇 |
1997年 | 28篇 |
1996年 | 28篇 |
1995年 | 16篇 |
1994年 | 14篇 |
1993年 | 22篇 |
1992年 | 18篇 |
1991年 | 10篇 |
1990年 | 7篇 |
1989年 | 14篇 |
1988年 | 8篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1982年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有1835条查询结果,搜索用时 15 毫秒
51.
Determination of effective moisture diffusivity and assessment of quality attributes of banana slices during drying 总被引:2,自引:0,他引:2
The influence of drying temperatures on the moisture diffusivity and quality attributes of the dried banana slices in terms of volatile compound, shrinkage, color, texture and microstructure were studied. Bananas with peel color index of 5 corresponding to yellow color with green tip were sliced into 3 mm thickness, dipped into ascorbic acid solution and dried at four temperatures of 70, 80, 90 and 100 °C. Drying rate of banana slices can be divided into two sub-drying periods, first and second falling rate periods. The effective diffusivity estimated by the optimization technique was found to decrease sharply with moisture content in the first falling rate period and changed slightly in the second falling rate period. High-temperature drying seems to provide lower loss of volatile compounds in the dried sample. Moreover, the dried banana was very porous, resulting in remarkably lower hardness value than that obtained from the low-temperature drying whilst the crispiness was not significantly different amongst the samples obtained at various drying temperatures. Although the textural property could be improved at high temperature, the product color was brown as manifested by the low L- and hue values in particular at the drying temperature of 100 °C. 相似文献
52.
文章通过对煤炭矿山青工安全技能培训面临的困惑进行了一些理论与实际的探讨。提出了相应的解决途径,目的在于减少矿山的安全事故,促进企业的良性循环与发展。 相似文献
53.
在肯定了烟气抬升高度与整个烟云扩展层内环境平均风速成反比的基础上,对“国标公式”(指GB13223—91中的公式,以下同)进行了修正,推出了新的计算式,并用浙江某热电厂的实测资料进行了验证。经分析比较认为:利用修正后的公式进行计算,其计算的准确性优于“国标公式”。 相似文献
54.
Yanru Shen Yongqi Tong Yuhao Zhao Lin Zhang Shi Bu Weigang Xu Chenye Pan Hong Ding Zhengjun Yang 《Advanced Powder Technology》2021,32(6):1858-1868
Aiming at the problems of low collection efficiency of fine particulate matter and large area occupied by existing electrostatic precipitators (ESP), a new type of horizontal electrode ESP is proposed. It has the advantages of accelerating turbulent coalescence, increasing the effective dust collecting area and increasing the particle driving speed. The performance of the new type of ESP is systematic studied through simulation and experiment at the same time, and the results matches well. By comparing the dust removal effect of the horizontal electrode ESP and the conventional ESP, it can be concluded that the horizontal electrode ESP has a better dust removal efficiency, and can still maintain a better dust removal effect under high air velocity. The dust removal efficiency of new ESP can reach above 98% under the experimental conditions. 相似文献
55.
Ioana Veronica Ciuchi Cristina Stefania Olariu Liliana Mitoseriu 《Materials Science and Engineering: B》2013,178(19):1296-1302
Measurements by impedance spectroscopy and Bruggeman effective medium approximation model were employed in order to determine the mineral volume fraction of dry bone. This approach assumes that two or more phases are present into the composite: the matrix (environment) and the other ones are inclusion phases. A fragment of femur diaphysis dense bone from a young pig was investigated in its dehydrated state. Measuring the dielectric properties of bone and its main components (hydroxyapatite and collagen) and using the Bruggeman approach, the mineral volume filling factor was determined. The computed volume fraction of the mineral volume fraction was confirmed by a histogram test analysis based on the SEM microstructures. In spite of its simplicity, the method provides a good approximation for the bone mineral volume fraction. The method which uses impedance spectroscopy and EMA modeling can be further developed by considering the conductive components of the bone tissue as a non-invasive in situ impedance technique for bone composition evaluation and monitoring. 相似文献
56.
Small-scale pool fire tests of ethanol-water mixtures are described in this paper. The main goal of the tests was to obtain data on the heat release rate per unit area, the total heat release per unit area, and the effective heat of combustion of such mixtures with ethanol percentage of 20 vol% or more. The results can be utilised in the interpolation and extrapolation of these quantities for different ethanol percentages and irradiance levels. In addition, the results give information on the heat release of possible pool fires of alcoholic beverages in a retail store in the case of a fully developed fire. It was concluded that significant fire load is not formed until the ethanol percentage of the alcoholic beverage is ca. 20 vol% or more. The data reported can also be used as an input to simulations of ethanol-water mixture pool fires in the performance-based fire safety design. 相似文献
57.
Franz B. Spingler Adam Phillips Tobias Schuler Michael C. Tucker Adam Z. Weber 《International Journal of Hydrogen Energy》2017,42(19):13960-13969
Reducing mass-transport losses in polymer-electrolyte fuel cells (PEFCs) is essential to increase their power density and reduce overall stack cost. At the same time, cost also motivates the reduction in expensive precious-metal catalysts, which results in higher local transport losses in the catalyst layers. In this paper, we use a hydrogen-pump limiting-current setup to explore the gas-phase transport losses through PEFC catalyst layers and various gas-diffusion and microporous layers. It is shown that the effective diffusivity in the gas-diffusion layers is a strong function of liquid saturation. In addition, it is shown how the catalyst layer unexpectedly contributes significantly to the overall measured transport resistance. This is especially true for low catalyst loadings. It is also shown how the various losses can be separated into different mechanisms including diffusional processes and mass-dependent and independent ones, where the data suggests that a large part of the transport resistance in catalyst layers cannot be attributed to a gas-phase diffusional process. The technique is promising for deconvoluting transport losses in PEFCs. 相似文献
58.
As a typical multi-functional single crystal material, lithium tantalate (LiTaO3 or LT) exhibits its excellent electro-optical, piezoelectric properties and has now been widely applied into many applications, such as electro-optical modulators, pyroelectric detectors, optical waveguide, piezoelectric transducers and SAW (surface acoustic wave) substrates. LT is known as a very important functional material, however the details of its machinability are not readily available yet. The content in this study is firstly focuses on the physical properties of LT like piezoelectric and pyroelectric effects and their influence on grinding performance. The obtained results are analyzed and discussed to understand its physical properties which have significant influences on their machinability in the grinding process. The crack initiation is possible to be dominated by internal stress which originated from self-polarization of the material itself. Hence, in order to suppress the physical effects induced by polarization during grinding of LT, control the temperature of coolant and increase the electrical conductivity of coolant are purposely tried in this study. The grinding results suggest that control of coolant temperature and use of electrolyte solution can effectively suppress the increasing rate of grinding torque and surface roughness, which in turn enhance the performance of LT wafer grinding. The LT wafers are eventually able to be thinned less than 100 μm. 相似文献
59.
Three human test series were conducted to evaluate the uniformity of the thermal environments in a stratum‐ventilated chamber with dimensions of 8.8 m (L) × 5.1 m (W) × 2.4 m (H). In all, nineteen conditions were generated by adjusting the room temperature, supply airflow rate, and supply terminal type. An air diffuser performance index (ADPI) of at least 80% was achieved for most cases. This result shows that the air velocity and temperature in the occupied zone are reasonably uniform. Subjective assessments using the ASHRAE 7‐point scale indicate that the thermal sensations of the subjects in stratum ventilation are also uniform. This study examines the applicability of the predicted mean vote (PMV) model for evaluating stratum ventilation. When compared to the actual mean thermal sensation votes (ATS), the PMV values are acceptable. The PMV results at a height of 1.1 m above the floor show better agreement with the ATS than at a height of 0.1 m. 相似文献
60.
The rigorous analytical approach to the conductivity homogenization problem for spheroidal particle composite with imperfect interfaces has been developed. The complete multipole series solution for a single inclusion with imperfect interface constitutes mathematical background of the work and provides a basic building block for the Maxwell and Rayleigh homogenization schemes. The low- and highly conducting spheroidal interface are considered in a unified way. The developed theory enables an analysis of composites of periodic and random micro structure with imperfect interfaces. Numerical study shows quite a significant combined effect of micro structure and imperfect interfaces on the macroscopic conductivity of composite. The obtained accurate solution serves as a benchmark for the known approximate theories. Their error due to neglecting the interaction effects and simplified treating the imperfect interfaces is estimated. 相似文献