全文获取类型
收费全文 | 1654篇 |
免费 | 59篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 17篇 |
综合类 | 1篇 |
化学工业 | 471篇 |
金属工艺 | 32篇 |
机械仪表 | 9篇 |
建筑科学 | 63篇 |
矿业工程 | 2篇 |
能源动力 | 43篇 |
轻工业 | 164篇 |
水利工程 | 9篇 |
石油天然气 | 10篇 |
无线电 | 171篇 |
一般工业技术 | 307篇 |
冶金工业 | 188篇 |
原子能技术 | 13篇 |
自动化技术 | 223篇 |
出版年
2022年 | 8篇 |
2021年 | 20篇 |
2020年 | 11篇 |
2019年 | 13篇 |
2018年 | 20篇 |
2017年 | 25篇 |
2016年 | 26篇 |
2015年 | 28篇 |
2014年 | 42篇 |
2013年 | 89篇 |
2012年 | 58篇 |
2011年 | 103篇 |
2010年 | 68篇 |
2009年 | 78篇 |
2008年 | 94篇 |
2007年 | 67篇 |
2006年 | 76篇 |
2005年 | 50篇 |
2004年 | 63篇 |
2003年 | 52篇 |
2002年 | 71篇 |
2001年 | 35篇 |
2000年 | 34篇 |
1999年 | 33篇 |
1998年 | 46篇 |
1997年 | 26篇 |
1996年 | 28篇 |
1995年 | 24篇 |
1994年 | 29篇 |
1993年 | 26篇 |
1992年 | 23篇 |
1991年 | 16篇 |
1990年 | 17篇 |
1989年 | 23篇 |
1988年 | 19篇 |
1987年 | 15篇 |
1986年 | 15篇 |
1985年 | 29篇 |
1984年 | 13篇 |
1983年 | 22篇 |
1982年 | 15篇 |
1981年 | 13篇 |
1980年 | 20篇 |
1979年 | 18篇 |
1978年 | 15篇 |
1977年 | 8篇 |
1976年 | 20篇 |
1975年 | 20篇 |
1974年 | 10篇 |
1971年 | 8篇 |
排序方式: 共有1723条查询结果,搜索用时 15 毫秒
11.
Ferrari CP Padova C Faïn X Gauchard PA Dommergue A Aspmo K Berg T Cairns W Barbante C Cescon P Kaleschke L Richter A Wittrock F Boutron C 《The Science of the total environment》2008,397(1-3):167-177
A field campaign was conducted in Ny-Alesund (78 degrees 54'N, 11 degrees 53'E), Svalbard (Norway) during April and May 2005. An Atmospheric Mercury (Hg) Depletion Event (AMDE) was observed from the morning of April 24 until the evening of April 27. Transport of already Hg and ozone (O3) depleted air masses could explain this observed depletion. Due to a snowfall event during the AMDE, surface snow Hg concentrations increased two fold. Hg deposition took place over a short period of time corresponding to 3-4 days. More than 80% of the deposited Hg was estimated to be reemitted back to the atmosphere in the days following the event. During the campaign, we observed night and day variations in surface snow Hg concentrations, which may be the result of gaseous elemental mercury (GEM) oxidation to divalent Hg at the snow/air interface by daylight surface snow chemistry. Finally, a decrease in the reactive Hg (HgR) fraction of total Hg (HgT) in the surface snow was observed during spring. We postulate that the transformation of HgR to a more stable form may occur in Arctic snow during spring. 相似文献
12.
Lee K Hur SD Hou S Hong S Qin X Ren J Liu Y Rosman KJ Barbante C Boutron CF 《The Science of the total environment》2008,404(1):171-181
A series of 42 snow samples covering over a one-year period from the fall of 2004 to the summer of 2005 were collected from a 2.1-m snow pit at a high-altitude site on the northeastern slope of Mt. Everest. These samples were analyzed for Al, V, Cr, Mn, Co, Ni, Cu, Zn, As, Rb, Sr, Cd, Sb, Pb, and Bi in order to characterize the relative contributions from anthropogenic and natural sources to the fallout of these elements in central Himalayas. Our data were also considered in the context of monsoon versus non-monsoon seasons. The mean concentrations of the majority of the elements were determined to be at the pg g(-1) level with a strong variation in concentration with snow depth. While the mean concentrations of most of the elements were significantly higher during the non-monsoon season than during the monsoon season, considerable variability in the trace element inputs to the snow was observed during both periods. Cu, Zn, As, Cd, Sb, and Bi displayed high crustal enrichment factors (EF(c)) in most samples, while Cr, Ni, Rb, and Pb show high EF(c) values in some of the samples. Our data indicate that anthropogenic inputs are potentially important for these elements in the remote high-altitude atmosphere in the central Himalayas. The relationship between the EF(c) of each element and the Al concentration indicates that a dominant input of anthropogenic trace elements occurs during both the monsoon and non-monsoon seasons, when crustal contribution is relatively minor. Finally, a comparison of the trace element fallout fluxes calculated in our samples with those recently obtained at Mont Blanc, Greenland, and Antarctica provides direct evidence for a geographical gradient of the atmospheric pollution with trace elements on a global scale. 相似文献
13.
Devez A Gomez E Gilbin R Elbaz-Poulichet F Persin F Andrieux P Casellas C 《The Science of the total environment》2005,348(1-3):82-92
The aim of this study was to assess the toxicity of runoff waters in an agricultural multipollution context through an in-depth assessment of copper bioavailability and toxicity. Runoff waters were screened for major ions, metals and diuron. The potential environmental impact of these runoff waters was evaluated using the conventional 72-h growth inhibition test with the green alga Pseudokirchneriella subcapitata. The results suggested that the toxicity detected in the calcareous vineyard field was due to the presence of diuron, whereas the non-calcareous runoff waters were non-toxic. Chemical speciation modelling by MINEQL revealed that most of the copper present in the non-toxic natural runoff waters was complexed by organic matter. These samples were spiked with copper, and then the toxicity and the electrochemically bioavailable copper fraction were measured. Differential pulse anodic stripping voltammetry (DPASV) was used to detect labile complexes and free copper. This combined approach highlighted the presence of some labile copper complexes in samples reaching the EC10-these could have contributed to the copper toxicity. 相似文献
14.
A Novel Technology for Natural Gas Conversion by Means of Integrated Oxidative Coupling and Dry Reforming of Methane 下载免费PDF全文
Dr. Joris W. Thybaut Prof. Guy B. Marin Dr. Claude Mirodatos Dr. Yves Schuurman Dr. Andre C. van Veen Prof. Vladislav A. Sadykov Dr. Helmut Pennemann Dr. Rainer Bellinghausen Prof. Leslaw Mleczko 《化学,工程师,技术》2014,86(11):1855-1870
A novel process concept for the oxidative coupling of methane followed by the oligomerization to liquids has been developed within the frame of the EU integrated project OCMOL. This technology is based on process intensification principles via cutting‐edge structured microreactor technology. It is also a fully integrated industrial process through the re‐use and the recycling of by‐products, in particular CO2, at every process stage. The focus of this contribution is on the reaction engineering aspects of the core steps, i.e., catalysts, kinetics and reactor design for the methane coupling and reforming. 相似文献
15.
Mgboawaji Claude UJILE Samuel Jonah ABBEY 《Frontiers of Structural and Civil Engineering》2022,16(7):803
Construction and demolition waste (CDW) are the largest waste products in the world today and competes as a viable recycled additive material in place of natural aggregates. Due to the increase in compressive strength of different mix proportions of CDW, it is also considered for reuse in concrete and subbase construction. This study shows the effect of CDW in expansive soil stabilization. The chemical and mechanical properties of these materials have shown that they are capable of developing compressive strength properties for replacement of cement with significant reduction in carbon emission. The inherent compositional properties of recycled CDW compared in this review suggests that CDW have good filler properties in highly expansive soils. Mixtures of crushed brick and recycled aggregates characterised based on chemical properties of different replacement ratios suggests that CDW of good-quality aggregates reduces swell potential of expansive soils and increased mechanical strength in pavement construction. 相似文献
16.
17.
Claude Cookman 《History of Photography》2013,37(2):199-207
Abstract When news of the assassination of Mohandas Gandhi circulated through New Delhi on 30 January 1948, Margaret Bourke-White, one of Life magazine's premier photographers, and Henri Cartier-Bresson, then a comparatively unknown French photojournalist, raced to Birla House, where the event occurred. Both understood the journalistic imperative of photographing Gandhi's body. Because of their different philosophical and technical approaches to photography, they responded to the challenge in different ways and produced very different results. This study compares their ideas, approaches, and results. It also offers a case study of one of Cartier-Bresson' s most important news reportages.1 相似文献
18.
Nicolas Bulidon Valérie Deydier Frederic Bumbieler Claude Duret-Thual Christophe Mendibide Didier Crusset 《工业材料与腐蚀》2021,72(1-2):154-165
Since 2014, the concept developed for the disposal of high-level radioactive waste in the French deep geological repository project Cigéo includes a cement-based grout material. This cement-based grout material will be injected between the casing and the claystone to neutralize the potential acidity resulting from the claystone oxidation induced by the drilling process of the disposal cell. In these conditions of pH (around 10.5) and temperature (90°C, maximum expected during the disposal), the metallic materials could be sensitive to stress corrosion cracking (SCC). In this project, different environments (aerated or deaerated, at room temperature or at 90°C) and synthetic solutions are considered to reproduce the different periods expected during the long life repository. The project is based on electrochemical measurements (polarization curves to define the SCC critical domain of potentials), slow strain rate tensile tests, and long-term immersion for crack initiation and propagation tests. 相似文献
19.