全文获取类型
收费全文 | 37805篇 |
免费 | 422篇 |
国内免费 | 530篇 |
专业分类
安全科学 | 1191篇 |
废物处理 | 1751篇 |
环保管理 | 4712篇 |
综合类 | 6113篇 |
基础理论 | 9930篇 |
环境理论 | 19篇 |
污染及防治 | 10000篇 |
评价与监测 | 2562篇 |
社会与环境 | 2251篇 |
灾害及防治 | 228篇 |
出版年
2023年 | 172篇 |
2022年 | 400篇 |
2021年 | 369篇 |
2020年 | 291篇 |
2019年 | 329篇 |
2018年 | 594篇 |
2017年 | 580篇 |
2016年 | 901篇 |
2015年 | 688篇 |
2014年 | 1055篇 |
2013年 | 3013篇 |
2012年 | 1266篇 |
2011年 | 1759篇 |
2010年 | 1416篇 |
2009年 | 1465篇 |
2008年 | 1760篇 |
2007年 | 1815篇 |
2006年 | 1558篇 |
2005年 | 1353篇 |
2004年 | 1238篇 |
2003年 | 1334篇 |
2002年 | 1185篇 |
2001年 | 1572篇 |
2000年 | 1098篇 |
1999年 | 666篇 |
1998年 | 455篇 |
1997年 | 459篇 |
1996年 | 468篇 |
1995年 | 550篇 |
1994年 | 541篇 |
1993年 | 427篇 |
1992年 | 464篇 |
1991年 | 433篇 |
1990年 | 485篇 |
1989年 | 438篇 |
1988年 | 369篇 |
1987年 | 342篇 |
1986年 | 271篇 |
1985年 | 315篇 |
1984年 | 338篇 |
1983年 | 327篇 |
1982年 | 308篇 |
1981年 | 282篇 |
1980年 | 231篇 |
1979年 | 256篇 |
1978年 | 216篇 |
1977年 | 164篇 |
1975年 | 181篇 |
1972年 | 160篇 |
1971年 | 159篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
981.
982.
983.
984.
S. Hul R.R. Tan J. Auresenia T. Fuchino D.C.Y. Foo 《Process Safety and Environmental Protection》2007,85(6):507-514
Different techniques for the synthesis of industrial water reuse/recycle networks have been developed in recent process integration research. These tools range from graphical pinch analysis approaches to mathematical programming models. The latter have the advantage of being flexible enough to incorporate various water network constraints, but in many cases these are often non-linear, thus making the identification of global optima difficult. Recent work has demonstrated the effectiveness of metaheuristic algorithms such as particle swarm optimization (PSO), for finding good solutions these problems. This work describes the use of a modified PSO for solving mixed integer non-linear programming (MINLP) models for water network synthesis. By incorporating a mutation operator for the binary variables in the model, the algorithm is able to escape sub-optimal network topologies and proceed towards better solutions than can be found with ordinary PSO. Two case studies involving water recycle/reuse are used to demonstrate the new design methodology. 相似文献
985.
S.M. Frolov V.Ya. Basevich V.A. Smetanyuk A.A. Belyaev H.J. Pasman 《Journal of Loss Prevention in the Process Industries》2007,20(4-6):562-569
The objective of the study reported herein is to simulate various physical and chemical phenomena accompanying fuel-rich n-butane–oxygen mixture preparation, ignition, preflame oxidation, and combustion in the standard 20-l explosion vessel, by applying mathematical models. Based on the computational fluid dynamics (CFD) simulations of the mixing process and natural convection of the ignition kernel, as well as on the analysis of the detailed reaction mechanism of n-butane oxidation, laminar flame propagation, and self-ignition, possible explanations for the phenomena observed experimentally have been suggested. The results of the study indicate that seemingly inflammable mixtures can become hazardous depending on the mixture preparation procedure and forced ignition timing. 相似文献
986.
987.
The growth of was significantly inhibited by Cd2+ concentrations greater than 0.02 ppm (μg/ml) and completely inhibited at 0.06 ppm (Day 12). Cadmium had no significant effect upon the lag phase of growth or the culture doubling time, but caused the retardation phase to arrive sooner. One ppm Cd2+ significantly inhibited the rates of both photosynthesis and acetylene reduction, by . , with complete inhibition at 4 and 20 ppm respectively. Cell sensitivity increased directly with exposure time. Cadmium caused some cell lysis of . and induced an increase in filament length, heterocyst frequency, and a loss of cellular contents from filament apical cells. The cellular abnormalities observed and the fact that toxicity increased with longer exposure times, suggested that metal toxicity resulted from effects of Cd2+ taken up by cells rather than Cd2+ at the cell surface. 相似文献
988.
989.
Stuhlbacher A Bradley MC Naylor C Calow P 《Environmental pollution (Barking, Essex : 1987)》1993,80(2):153-158
The extent to which responses to toxicants can be modified by the environment and genotype of Daphnia magna is important for interpreting the results from ecotoxicity tests. Variation in the development of cadmium resistance and its relevance for survivorship has been investigated in two genetically distinct clones of D. magna. Cadmium resistance was induced by pre-exposing daphnids to a sublethal concentration of a Cd/Zn mixture and thereafter cadmium tolerance was assessed in standard acute tests. The results showed that the ability to develop cadmium resistance is affected by temperature, but there is no consistent pattern for maternal nutrition. The age of the daphnids had no apparent effect on the development of cadmium resistance. Differences in the induction of cadmium resistance between clones were seen only under resource depression. 相似文献
990.
Lemna trisulca was grown, using aseptic culture techniques in a filter-sterilized medium, a portion of which was replaced regularly during experiments. L. trisulca responded to the addition of 0.64 microM Cd with a reduction in multiplication rate (MR) 2 +/- 1 days after exposure. The internal Cd content reached 1000 +/- 140 microg Cd/g (dry wt) within 2 days exposure to 0.64 microM Cd. The final yield was reduced by an average of c.8% for each day of exposure to 0.64 microM Cd in a 14 day experiment. This implies that an equilibration period should be used for short-term bioassay tests before the effect of a toxicant is determined. Pretreating L. trisulca with 0.08 or 0.32 microM Cd for 6 weeks had no significant effect on MR or Cd uptake when plants were subsequently exposed to a range of Cd concentrations or grown in a control medium. This suggests that L. trisulca does not become acclimated to elevated Cd concentrations. The MR of L. trisulca fluctuated over a period of almost 600 days and the doubling time ranged from 1.6 to 2.4 days. This produced more than a fivefold difference in final yield in experiments of 14 days duration. The reduction in MR in response to 0.32 microM Cd during this same 600 days period averaged 24% with a coefficient of variation of 38%, and varied with the MR of control cultures. Fluctuations in the intrinsic growth rate and the effect of a toxicant on L. trisulca could potentially confound the assessment of toxicity and must be carefully considered when designing test protocols for aquatic plants. 相似文献