全文获取类型
收费全文 | 2933篇 |
免费 | 78篇 |
国内免费 | 30篇 |
专业分类
安全科学 | 129篇 |
废物处理 | 120篇 |
环保管理 | 857篇 |
综合类 | 296篇 |
基础理论 | 699篇 |
环境理论 | 1篇 |
污染及防治 | 641篇 |
评价与监测 | 172篇 |
社会与环境 | 85篇 |
灾害及防治 | 41篇 |
出版年
2023年 | 15篇 |
2022年 | 21篇 |
2021年 | 29篇 |
2020年 | 25篇 |
2019年 | 36篇 |
2018年 | 52篇 |
2017年 | 49篇 |
2016年 | 70篇 |
2015年 | 56篇 |
2014年 | 56篇 |
2013年 | 315篇 |
2012年 | 117篇 |
2011年 | 153篇 |
2010年 | 117篇 |
2009年 | 131篇 |
2008年 | 179篇 |
2007年 | 164篇 |
2006年 | 144篇 |
2005年 | 103篇 |
2004年 | 82篇 |
2003年 | 113篇 |
2002年 | 95篇 |
2001年 | 67篇 |
2000年 | 53篇 |
1999年 | 29篇 |
1998年 | 45篇 |
1997年 | 30篇 |
1996年 | 40篇 |
1995年 | 50篇 |
1994年 | 31篇 |
1993年 | 44篇 |
1992年 | 38篇 |
1991年 | 19篇 |
1990年 | 26篇 |
1989年 | 18篇 |
1988年 | 25篇 |
1987年 | 17篇 |
1986年 | 20篇 |
1985年 | 30篇 |
1984年 | 25篇 |
1983年 | 27篇 |
1982年 | 34篇 |
1981年 | 34篇 |
1980年 | 32篇 |
1979年 | 22篇 |
1978年 | 23篇 |
1977年 | 12篇 |
1976年 | 11篇 |
1974年 | 9篇 |
1972年 | 9篇 |
排序方式: 共有3041条查询结果,搜索用时 15 毫秒
71.
Chandra Nath Shiv G. Kapoor Richard E. DeVor Anil K. Srivastava Jon Iverson 《Journal of Manufacturing Processes》2012,14(4):452-459
Tool life has been a vital issue in machining titanium alloys. Recently, an atomization-based cutting fluid (ACF) application has been found to be an effective approach for cooling and lubrication in micromachining operations. In this study, an ACF spray system is developed for macro-scale turning of Ti–6Al–4V. The spray system is designed to minimize interaction between the fluid droplets, and the gas nozzle to control the divergence of the fluid droplets. Experiments are conducted to study the effect of five specific ACF spray parameters including fluid flow rate, spray distance, impingement angle, and type and pressure level of the droplet carrier gas on cutting forces, tool life, and chip characteristics. It has been observed that the combination of lower pressure (150 psi) air-mixed CO2 with a higher flow rate (20 ml/min) and a larger spray distance (35 mm) produces a significantly longer tool life and broken chips. The results also reveal that the ACF spray system can extend tool life up to 40–50% over flood cooling. 相似文献
72.
Modeling and interpretation of fiber orientation-based failure mechanisms in machining of carbon fiber-reinforced polymer composites 总被引:1,自引:0,他引:1
Kevin A. Calzada Shiv G. Kapoor Richard E. DeVor Johnson Samuel Anil K. Srivastava 《Journal of Manufacturing Processes》2012,14(2):141-149
The development and implementation of a microstructure-based finite element model for the machining of carbon fiber-reinforced polymer composites is presented. A new approach to interfacial modeling is introduced where the material interface is modeled using continuum elements, allowing failure to take place in either tension or compression. The model is capable of describing the fiber failure mode occurring throughout the chip formation process. Characteristic fiber length in the chips, and machining forces for microstructures with fibers orientated at 0°, 45°, 90°, and 135° are examined. For model validation purposes, the model-based machining performance predictions are compared to the machining responses from a set of orthogonal machining experiments. A parametric study is presented that identifies a robust tool geometry, which minimizes the effects of fiber orientation and size on the machining forces. 相似文献
73.
The double trade-off between adaptation and mitigation for sea level rise: an application of FUND 总被引:6,自引:2,他引:4
Richard S. J. Tol 《Mitigation and Adaptation Strategies for Global Change》2007,12(5):741-753
This paper studies the effects of adaptation and mitigation on the impacts of sea level rise. Without adaptation, the impact
of sea level rise would be substantial, almost wiping out entire countries by 2100, although the globally aggregate effect
is much smaller. Adaptation would reduce potential impacts by a factor 10–100. Adaptation would come at a minor cost compared
to the damage avoided. As adaptation depends on socio-economic status, the rank order of most vulnerable countries is different
than the rank order of most exposed countries. Because the momentum of sea level rise is so large, mitigation can reduce impacts
only to a limited extent. Stabilising carbon dioxide concentrations at 550 ppm would cut impacts in 2100 by about 10%. However,
the costs of emission reduction lower the avoided impacts by up to 25% (average 10%). This is partly due to the reduced availability
of resources for adaptation, and partly due to the increased sensitivity to wetland loss by adaptation.
相似文献
Richard S. J. TolEmail: |
74.
Lu Y Beeman RW Campbell JF Park Y Aikins MJ Mori K Akasaka K Tamogami S Phillips TW 《Die Naturwissenschaften》2011,98(9):755-761
We report that the abdominal epidermis and associated tissues are the predominant sources of male-produced pheromones in the
red flour beetle, Tribolium castaneum and, for the first time, describe the stereoisomeric composition of the natural blend of isomers of the aggregation pheromone
4,8-dimethyldecanal (DMD) in this important pest species. Quantitative analyses via gas chromatography–mass spectrometry showed
that the average amount of DMD released daily by single feeding males of T. castaneum was 878 ± 72 ng (SE). Analysis of different body parts identified the abdominal epidermis as the major source of aggregation
pheromone; the thorax was a minor source, while no DMD was detectable in the head. No internal organs or obvious male-specific
glands were associated with pheromone deposition. Complete separation of all four stereoisomers of DMD was achieved following
oxidation to the corresponding acid, derivatization with (1R, 2R)- and (1S, 2S)-2-(anthracene-2,3-dicarboximido)cyclohexanol to diastereomeric esters, and their separation on reversed-phase high-performance
liquid chromatography at −54°C. Analysis of the hexane eluate from Porapak-Q-collected volatiles from feeding males revealed
the presence of all four isomers (4R,8R)/(4R,8S)/(4S,8R)/(4S,8S) at a ratio of approximately 4:4:1:1. A walking orientation bioassay in a wind tunnel with various blends of the four synthetic
isomers further indicated that the attractive potency of the reconstituted natural blend of 4:4:1:1 was equivalent to that
of the natural pheromone and greater than that of the 1:1 blend of (4R,8R)/(4R,8S) used in commercial lures. 相似文献
75.
Leona Bohdalkova Martin Novak Frantisek Buzek Jakub Kreisinger Richard Bindler Katerina Pazderu Petra Pacherova 《Mitigation and Adaptation Strategies for Global Change》2014,19(7):997-1010
There are fears that global warming will lead to degradation of peatlands, higher emissions of greenhouse gases from peat, and accelerated warming. Anaerobic decomposition of organic soils produces methane (CH4), a potent greenhouse gas. Two peat bogs differing in mean annual temperature, Velke Darko (VD, Czech Republic, 7.2 °C), and Stor Åmyran (SA, Sweden, 4.0 °C), were selected for a comparative study of how organic soils in different climatic zones will respond to warmer and drier conditions. Twenty peat cores from each bog were incubated in growth chambers. Under present-day summer conditions, VD produced 14 times more CH4 than SA. Two different warming scenarios were used. Peat-core replicates were kept at temperatures of 11 versus 16 °C, and 11 versus 22 °C. From 11 to 16 °C, the CH4 production slightly decreased at SA, and slightly increased at VD. From 11 to 22 °C, the CH4 production increased 9 times at SA, but slightly decreased at VD. After an 8-month incubation, peat cores under drying conditions (water table at ?14 cm) were compared to samples with original water table (?2 cm). Drying conditions led to a steeper reduction in CH4 production at VD, compared to SA. The CH4 production decreased more than 100 times at VD. Then, the combined effect of simultaneous warming and drying at 11 and 22 °C was studied. We did not find any significant effect of interactions between increasing temperature and decreasing water table level. Overall, the warmer site VD responded more strongly to the simulated climate change than the colder site SA. 相似文献
76.
77.
78.
David Sinclair Richard J. Countess Benjamin Y. H. Liu David Y. H. Pui 《Journal of the Air & Waste Management Association (1995)》2013,63(7):661-663
The diffusion battery, an assembly of circular tubes or rectangular channels, is one of the best devices available for measuring the size and size distribution of submicron aerosols in the diameter range 0.002 to 0.2 µ m. The performance of these batteries is known from molecular diffusion theory, but until now has not been checked experimentally in this size range because of the lack of the necessary monodisperse aerosols. Experimental measurements on singly charged monodisperse aerosols from 0.01 µm to 0.1 µ m are described using a General Electric and a Pollak condensation nucleus counter to measure the aerosol penetration through the stages of a set of portable diffusion batteries in series. Particle sizes in the range tested could be selected at will by adjusting the voltage of an electric mobility classifier. The fraction of aerosol of a given size passing through each battery stage was found to agree closely with the penetration calculated from molecular diffusion theory for that size. This shows that the theory is correct and confirms that the aerosol produced by the electric mobility classifier was monodisperse. In addition, it was found that the difference in penetration between a charged versus a neutralized aerosol was insignificant except for the smallest aerosols used. 相似文献
79.
Richard D. Siegel John R. Ehrenfeld Paul Morgenstern 《Journal of the Air & Waste Management Association (1995)》2013,63(3):256-259
Initial implementation plans provided for particulate reduction largely through the imposition of emission limitations on industrial processes, large steam generators, and solid waste disposal, requiring, in turn, application of control equipment for compliance. In many urban areas, this approach is not adequate to achieve the secondary air quality standards so that a more general strategy must be employed. Such strategy may include restrictions on fuel burning, combustion equipment, maintenance programs, utility steam distribution, etc. The potential abatement achievable through such strategies is described using Boston as a case study. Cost and technical factors associated with each strategy are discussed. 相似文献
80.
Daniel W. Franks Graeme D. Ruxton Richard James 《Behavioral ecology and sociobiology》2010,64(3):493-503
Ecologists increasingly use network theory to examine animal association patterns. The gambit of the group (GoG) is a simple
and useful assumption for accumulating the data necessary for a network analysis. The gambit of the group implies that each
animal in a group is associating with every other individual in that group. Sampling is an important issue for networks in
wild populations collected assuming GoG. Due to time, effort, and resource constraints and the difficulty of tracking animals,
sampled data are usually a subset of the actual network. Ecologists often use association indexes to calculate the frequency
of associations between individuals. These indexes are often transformed by applying a filter to produce a binary network.
We explore GoG sampling using model networks. We examine assortment at the level of the group by a single dichotomous trait,
along with many other network measures, to examine the effect of different sampling regimes, and choice of filter on the accuracy
and precision with which measures are estimated. We find strong support for the use of weighted, rather than filtered, network
measures and show that different filters have different effects depending on the nature of the sampling. We make several practical
recommendations for ecologists planning GoG sampling. 相似文献