全文获取类型
收费全文 | 19211篇 |
免费 | 817篇 |
国内免费 | 20篇 |
专业分类
电工技术 | 222篇 |
综合类 | 21篇 |
化学工业 | 3960篇 |
金属工艺 | 348篇 |
机械仪表 | 428篇 |
建筑科学 | 1083篇 |
矿业工程 | 51篇 |
能源动力 | 519篇 |
轻工业 | 1781篇 |
水利工程 | 128篇 |
石油天然气 | 56篇 |
武器工业 | 1篇 |
无线电 | 1645篇 |
一般工业技术 | 3221篇 |
冶金工业 | 3472篇 |
原子能技术 | 197篇 |
自动化技术 | 2915篇 |
出版年
2023年 | 146篇 |
2022年 | 236篇 |
2021年 | 477篇 |
2020年 | 347篇 |
2019年 | 373篇 |
2018年 | 430篇 |
2017年 | 393篇 |
2016年 | 507篇 |
2015年 | 442篇 |
2014年 | 535篇 |
2013年 | 1112篇 |
2012年 | 886篇 |
2011年 | 1148篇 |
2010年 | 802篇 |
2009年 | 849篇 |
2008年 | 889篇 |
2007年 | 790篇 |
2006年 | 738篇 |
2005年 | 612篇 |
2004年 | 508篇 |
2003年 | 458篇 |
2002年 | 450篇 |
2001年 | 322篇 |
2000年 | 332篇 |
1999年 | 372篇 |
1998年 | 855篇 |
1997年 | 560篇 |
1996年 | 445篇 |
1995年 | 330篇 |
1994年 | 314篇 |
1993年 | 308篇 |
1992年 | 205篇 |
1991年 | 174篇 |
1990年 | 149篇 |
1989年 | 150篇 |
1988年 | 134篇 |
1987年 | 133篇 |
1986年 | 130篇 |
1985年 | 158篇 |
1984年 | 155篇 |
1983年 | 130篇 |
1982年 | 100篇 |
1981年 | 116篇 |
1980年 | 98篇 |
1979年 | 106篇 |
1978年 | 95篇 |
1977年 | 132篇 |
1976年 | 163篇 |
1975年 | 98篇 |
1974年 | 80篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
991.
There is currently an international drive to build new nuclear power plants, bringing about what is being termed a “nuclear renaissance”. However, the public perception of nuclear energy has historically been, and continues to be, a key issue, particularly in light of the Fukushima nuclear incident. This paper discusses the disparity between perceived and calculated risks based on the last four decades of research into risk perception. The leading psychological and sociological theories, Psychometric Paradigm and Cultural Theory, respectively, are critically reviewed. The authors then argue that a new nuclear-build policy that promotes a broader approach to design incorporating a wider range of stakeholder inputs, including that of the lay public, may provide a means for reducing the perceived risk of a nuclear plant. Further research towards such a new approach to design is proposed, based on integrating expert and lay stakeholder inputs and taking into account broader socio-cultural factors whilst maintaining the necessary emphasis on safety, technological development, economics and environmental sustainability. 相似文献
992.
Marisa Di Sabatino Mari Juel Lars Arnberg Martin Syvertsen Gabriella Tranell 《Transactions of the Indian Institute of Metals》2009,62(4-5):511-513
Two different cooling rates have been imposed during the early solidification of two multi-crystalline silicon ingots with 250mm diameter and 100mm height in a pilot scale directional solidification furnace. This has been done by opening a variable heat leak system below the crucible in order to achieve a high initial cooling rate in one of the ingots. The grain-structure and -orientation of these two ingots have been investigated by light microscopy (LM) and electron backscattered diffraction (EBSD), and their electrical properties by quasi-steady state photo-conductance (QSSPC) and surface photovoltage (SPV) method. The ingot with the high initial cooling rate shows predominantly grains which are significantly larger than what is usually found in mc-Si. The minority carrier diffusion lengths measured on the large grains in the ingot with high cooling rate show higher values than those measured on the ingot with smaller grains. These results indicate that principles of grain size and -orientation control in mc-Si ingots can be applied to a pilot scale furnace, and the potential for up-scaling to industrial ingots with improved electrical properties and, thus, higher solar cell conversion efficiency. 相似文献
993.
Joamin Gonzalez-Gutierrez Martin G. Scanlon 《Journal of the American Oil Chemists' Society》2013,90(9):1319-1326
Many soft food materials, including vegetable shortening, exhibit complex rheological behavior. For shortening, a precise determination of rheological behavior is necessary to understand its functionality as a food ingredient. Commercial vegetable shortening was subjected to monotonic and cyclic uniaxial compression tests at a wide range of loading rates. The elastic modulus determined from unloading was a function of strain, varying between 740 kPa in the shortening’s strain hardening region to 220 kPa at large strain where perfect plasticity had developed. Visual analysis of shortening specimens during the compression process showed that a rate-dependent stress overshoot was attributable to the development of a shear band following strain hardening. An elastoviscoplastic constitutive model was developed to define the complex rate-dependent compression response of vegetable shortening. Using the fundamental parameters obtained from the different types of compression tests, the proposed model accurately predicted the uniaxial compression response of vegetable shortening over a wide range (three decades) of compression rates. A model with predictive capabilities of large strain properties is desirable because shortening is subject to large strain in essentially all applications. 相似文献
994.
995.
Encarnacin Raymundo‐Piero Martin Cadek Franois Bguin 《Advanced functional materials》2009,19(7):1032-1039
The sea provides a large variety of seaweeds that, because of their chemical composition, are fantastic precursors of nanotextured carbons. The carbons are obtained by the simple pyrolysis of the seaweeds under a nitrogen atmosphere between 600 and 900 °C, followed by rinsing the product in slightly acidic water. Depending on the origin of the seaweed and on the pyrolysis conditions, the synthesis may be oriented to give an oxygen‐enriched carbon or to give a tuned micro/mesoporous carbon. The samples with a rich oxygenated surface functionality are excellent as supercapacitor electrodes in an aqueous medium whereas the perfectly tuned porous carbons are directly applicable for organic media. In both cases, the specific surface area of the attained carbons does not exceed 1300 m2 g−1, which results in high‐density materials. As a consequence, the volumetric capacitance is very high, making these materials more interesting than activated carbons from the point of view of developing small and compact electric power sources. Such versatile carbons, obtained by a simple, ecological, and cheap process, could be well used for environment remediation such as water and air treatment. 相似文献
996.
Kubzansky Laura D.; Martin Laurie T.; Buka Stephen L. 《Canadian Metallurgical Quarterly》2009,28(3):364
Objective: The aim of this study is to investigate whether individual personality or temperamental qualities that emerge early and persist over the life course, predict adult midlife health. Specific childhood personality attributes considered include distress proneness, behavioral inhibition, and ability to stay focused on a task. Design: Prospective data are from 569 individuals followed from birth into adulthood. Main Outcome Measures: Outcomes include two different measures of adult health: self-rated general health, and number of illnesses in adulthood. Results: Childhood personality attributes related to attention and distress were significantly associated with adult health, with stronger effects evident among women. Children with high attention reported better self-rated health (b = 0.12, p 相似文献
997.
998.
999.
Ultrasonic velocities of compressional and shear waves in frozen sand, silty-sand and silt were measured at subfreezing temperature and the relationship between acoustic and physical-mechanical properties examined. Ultrasonic measurements revealed that the influence of temperature on ultrasonic velocities is due to the phase transition from water to ice. Different methods were proposed to determine the amount of unfrozen water in frozen soils. The unfrozen water content was measured directly by time domain reflectometry and compared to predicted values using different theoretical approaches. The prediction models showed good agreements with measured values at low temperatures. However, the shape of the curves obtained did not completely satisfying as the estimated unfrozen water fraction near 0 °C was significantly greater than the measured values. Finally, based on the elastic wave theory and measured acoustic velocities the elastic constants of the frozen soils were calculated. The changes in elastic constants were found to be related to the increase in ice content, ice stiffness by ice cementation and a decrease in unfrozen water content. 相似文献
1000.
Joachim Mittendorf Prof. Dr. Stefan Weigand Dr. Cristina Alonso‐Alija Dr. Erwin Bischoff Dr. Achim Feurer Dr. Michael Gerisch Dr. Armin Kern Dr. Andreas Knorr Dr. Dieter Lang Dr. Klaus Muenter Dr. Martin Radtke Dr. Hartmut Schirok Dr. Karl‐Heinz Schlemmer Dr. Elke Stahl Dr. Alexander Straub Dr. Frank Wunder Dr. Johannes‐Peter Stasch Dr. 《ChemMedChem》2009,4(5):693-693