首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   510篇
  免费   15篇
  国内免费   21篇
安全科学   80篇
废物处理   22篇
环保管理   79篇
综合类   136篇
基础理论   145篇
环境理论   7篇
污染及防治   28篇
评价与监测   4篇
社会与环境   42篇
灾害及防治   3篇
  2024年   1篇
  2023年   12篇
  2022年   9篇
  2021年   19篇
  2020年   24篇
  2019年   18篇
  2018年   17篇
  2017年   42篇
  2016年   44篇
  2015年   34篇
  2014年   46篇
  2013年   93篇
  2012年   5篇
  2011年   13篇
  2010年   5篇
  2009年   5篇
  2008年   10篇
  2007年   13篇
  2006年   15篇
  2005年   16篇
  2004年   16篇
  2003年   14篇
  2002年   15篇
  2001年   9篇
  2000年   7篇
  1999年   2篇
  1998年   1篇
  1997年   1篇
  1996年   4篇
  1995年   10篇
  1994年   4篇
  1992年   1篇
  1989年   4篇
  1987年   4篇
  1986年   2篇
  1985年   3篇
  1983年   1篇
  1982年   1篇
  1981年   1篇
  1972年   3篇
  1971年   1篇
  1970年   1篇
排序方式: 共有546条查询结果,搜索用时 468 毫秒
331.
Conflict caused by wild herbivores damaging crops is an almost universal problem in conservation. We designed and implemented a game-theory-based system for supporting farmers whose crops were being heavily damaged by wild herbivores. In this community-operated system, farmers self-report their production, which is endorsed by neighboring farmers. The average deficit in production is compensated for by a payment that is directly proportional to the average deficit in production of the group and to the individual farmer's productivity. As a result, farmers are compensated for the average damage (support) and rewarded for individual productivity (reward) (i.e., support cum reward [SuR]). The design of the game is such that only honest reporting gives maximum returns. Farmers who underreport receive less payment because the SuR amount is proportionate to their self-reported productivity. The endorsing farmers, in their own self-interest, prevent overreporting. The system involves multiple game situations, the combined result of which is a stable strategy based on honesty and hard work. In 2 villages along the western boundary of Tadoba Andhari Tiger Reserve in central India, we tested the system with 75 farmers over 6 crop seasons. After a few initial attempts to cheat, honesty prevailed throughout the group. Average crop productivity increased 2.5-fold, in spite of damage, owing to increased effort by farmers. Apart from wildlife conflict resolution, the model offers a promising alternative to crop insurance and a potential behavioral green revolution in agriculture.  相似文献   
332.
Smith–Lemli–Opitz (RSH) syndrome (SLOS, OMIM 270400) is a relatively common, autosomal recessive disorder of cholesterol biosynthesis with a broad spectrum of phenotypic abnormalities caused by mutations of the 7-dehydrocholesterol reductase gene (DHCR7) on chromosome 11. Prenatal diagnosis can be established by detection of elevated 7-dehydrocholesterol or of SLOS-causing mutations in the DHCR7 gene. We report here our experience with molecular prenatal diagnosis of SLOS. Mutation analysis of the DHCR7 gene was performed in chorionic villus samples of 13 pregnancies of couples with a family history of SLOS and known SLOS genotypes. This approach is accurate and reliable. If facilities for biochemical analysis are not available, or in cases with ambiguous biochemical patterns, molecular prenatal diagnosis is an attractive, alternative option. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   
333.
We report a case of a twin pregnancy which was complicated by a twin–twin transfusion in which the recipient twin was noted to have an intra-abdominal echogenic mass. This twin died at two days of age of hepatic infarction. The donor twin was healthy at birth, at thirty weeks' gestation, and did not have any subsequent problems. Fetal intra-abdominal echogenicity may be a marker of hepatic infarction. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   
334.
The Jarcho–Levin syndrome is a specific form of spondylocostal/spondylothoracic dysostosis. There have been various classifications of this syndrome. We present the case of a severe prenatal Jarcho–Levin syndrome, diagnosed by ultrasound examination during the first trimester of pregnancy in a family with no previous medical history of an affected child. X-ray exploration, high-resolution spiral computed tomography and autopsy confirmed the diagnosis. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   
335.
Today, economic experiments are well accepted in mainstream economics. They are also widely applied in ecological economics, often focusing on institutions. Yet, many empirical studies in this field lack a sound theoretical foundation of institutions and institutional change. In this paper, I show that in a structure–agency framework three theoretical viewpoints on institutions can be distinguished. They can be viewed as (1) structures that shape incentives, (2) cognitive media, embedded in beliefs and cognition of agents, or (3) evolving from a process of agents’ choices and structural aspects. Using examples from the empirical experimental literature, I argue that all three viewpoints are mirrored in experimental practice, and that these can be organized into an institutional typology of economic experiments. Placing special emphasis on experiments with endogenous institutional choice and their relationship to evolutionary economic theory, I discuss under which conditions experiments are a useful method for the analysis of social–ecological systems, concluding that methodological and methodical innovations are an important prerequisite for challenging the dominant paradigm of neoclassical economics.  相似文献   
336.
337.
As one of the most ambitious national energy transition initiatives worldwide, the German Energiewende is attracting a huge amount of attention globally in both policy and research circles. The paper explores the implementation of Germany's energy transition through the lens of organisation and ownership in urban and regional contexts. Following a summary of the principal institutional challenges of the Energiewende at local and regional levels the paper develops a novel way of conceptualising the institutional to urban and regional energy transitions in terms of agency and power, ideas and discourse, and commons and ownership. This analytical heuristic is applied to a two-tier empirical study of the Berlin–Brandenburg region. The first tier involves a survey of the organisational landscape of energy infrastructures and services in cities, towns and villages in Brandenburg. The second tier comprises a case study of current, competing initiatives for (re-)gaining ownership of the power grid and utility in Berlin. The paper draws conclusions on the diverse and dynamic organisational responses to the Energiewende at the local level, what these tell us about urban and regional energy governance and how they are inspired by – or in opposition to – new forms of collective ownership resonant of recent debates on reclaiming the commons. It concludes with observations on how relational approaches to institutional research and the notion of the commons can guide and inspire future research on socio-technical transitions in general, and urban energy transitions in particular.  相似文献   
338.
Electrohydraulic forming (EHF) is a high energy rate forming process in which the strain rate in the sheet metal can vary from 5 × 102 to 105 s−1 depending on various factors. Several mechanisms have been reported to cause an improvement in formability in EHF such as material deformation mechanisms, inertial effects and the dynamic impact of the sheet against the die. EHF is a complex high speed forming process and experimental work alone is not sufficient to properly understand this process. To understand the variation of some influential variables in EHF, electrohydraulic die-forming (EHDF) and free-forming (EHFF) of DP590 dual phase steel were simulated in ABAQUS/Explicit by considering the fluid/structure interactions. Three-dimensional finite element simulations were conducted by modelling the water with Eulerian elements with a view to investigating the effect of released energy on the sheet deformation profile history, strain distribution, loading path and damage accumulation type. The Johnson–Cook constitutive material model was used to predict the sheet behaviour and the parameters in this model were calibrated based on experimental test results available for DP590 at various strain rates. The Johnson–Cook phenomenological damage model was also used to predict the ductile failure (damage accumulation) in both EHDF and EHFF. Predicted final strain values and damage accumulation type showed good agreement with the experimental observations.  相似文献   
339.
340.
The knowledge of the vapor–liquid two-phase diethyl ether (DEE)/air mixtures (mist) on the explosion parameters was an important basis of accident prevention. Two sets of vapor–liquid two-phase DEE/air mixtures of various concentrations were obtained with Sauter mean diameters of 12.89 and 22.90 μm. Experiments were conducted on vapor–liquid two-phase DEE/air mixtures of various concentrations at an ignition energy of 40.32 J and at an initial room temperature and pressure of 21 °C and 0.10 MPa, respectively. The effects of the concentration and particle size of DEE on the explosion pressure, the explosion temperature, and the lower and upper flammability limits were analyzed. Finally, a series of experiments was conducted on vapor–liquid two-phase DEE/air mixtures of various concentrations at various ignition energies. The minimum ignition energies were determined, and the results were discussed. The results were also compared against our previous work on the explosion characteristics of vapor–liquid two-phase n-hexane/air mixtures.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号