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   697篇
  免费   17篇
  国内免费   7篇
安全科学   29篇
废物处理   34篇
环保管理   123篇
综合类   93篇
基础理论   173篇
环境理论   1篇
污染及防治   158篇
评价与监测   45篇
社会与环境   48篇
灾害及防治   17篇
  2023年   13篇
  2022年   8篇
  2021年   15篇
  2020年   22篇
  2019年   12篇
  2018年   33篇
  2017年   18篇
  2016年   26篇
  2015年   23篇
  2014年   14篇
  2013年   56篇
  2012年   33篇
  2011年   44篇
  2010年   28篇
  2009年   34篇
  2008年   23篇
  2007年   28篇
  2006年   26篇
  2005年   25篇
  2004年   18篇
  2003年   24篇
  2002年   30篇
  2001年   7篇
  2000年   8篇
  1999年   9篇
  1998年   4篇
  1997年   8篇
  1996年   6篇
  1995年   7篇
  1994年   4篇
  1993年   5篇
  1992年   7篇
  1991年   4篇
  1990年   8篇
  1989年   14篇
  1988年   6篇
  1987年   3篇
  1986年   13篇
  1985年   5篇
  1984年   4篇
  1983年   4篇
  1982年   4篇
  1981年   4篇
  1980年   4篇
  1979年   3篇
  1978年   2篇
  1972年   2篇
  1966年   2篇
  1965年   2篇
  1931年   2篇
排序方式: 共有721条查询结果,搜索用时 17 毫秒
391.
The aim of this in vitro study was to examine the secretion activity, markers of proliferation and apoptosis in porcine ovarian granulosa cells (GCs) after deoxynivalenol (DON) addition. Ovarian granulosa cells were incubated with DON for 24h: 10, 100 and 1000 ng/mL, while the control group received no DON. The secretion of insulin-like growth factor I (IGF-I) and progesterone was determined by radioimmunoassay (RIA) and expression of cyclin B1, PCNA and caspase-3 by immunocytochemistry. IGF-I release by GCs was inhibited by DON, while progesterone release and the expression of cyclin B1 was stimulated by DON (at 1000 ng/mL but not at 10 and 100 ng/mL). PCNA expression was stimulated by DON (at 100 and 1000 ng/mL but not at 10 ng/mL). Caspase-3 expression was not influenced by DON treatment (at all doses). In conclusion, our results indicate, (1) a direct effect of DON on secretion of growth factor IGF-I and steroid hormone progesterone, (2) expression of markers of proliferation (cyclin B1 and PCNA) but not on the (3) expression of marker of apoptosis (caspase-3) in porcine ovarian granulosa cells. This in vitro study suggests the dose-dependent association of DON on porcine ovarian functions.  相似文献   
392.
Based on requirements under the Clean Air Act Amendments of 1990, most state vehicle inspection and maintenance (I/M) programs have, since 2002, replaced the tailpipe emission testing with the on-board diagnostic (OBD) II testing for 1996 model and newer vehicles. This test relies on the OBD II system to give the pass or fail result, depending on certain conditions that might cause the vehicle to emit pollution 1.5 times higher than the regulated standard. The OBD II system is a computer and sensors installed in the vehicle to monitor the emission control units and signal if there is any malfunction. As a vehicle ages, its engine, pollution control units, and OBD II system deteriorate. Because the OBD II system's durability directly influences the test outcome, it is important to examine the fleetwide trend in the OBD II test results in comparison with an alternative measure of identifying high emitting vehicles. This study investigates whether the validity and reliability of the OBD II test is related to the age of the OBD II system installed in the fleet. Using Atlanta's I/M testing records and remote sensing device (RSD) data collected during 2002-2005, this research establishes the convergent validity and interobserver reliability criteria for the OBD II test based on on-road emissions measured by RSDs. The study results show that older vehicles exhibit significantly lower RSD-OBD II outcome agreement than newer vehicles. This suggests that the validity and reliability of the OBD II test may decline in the older vehicle fleets. Explanations and possible confounding factors for these findings are discussed.  相似文献   
393.
394.
Orlov A  Klinowski J 《Chemosphere》2009,74(2):344-348
Catalytic combustion of volatile organic compounds, such as propene, has been studied on manganese modified mesoporous molecular sieves. Powder X-ray diffraction, (29)Si nuclear magnetic resonance, nitrogen sorption and transmission electron microscopy show that the SBA-15 mesoporous silica molecular sieve can be modified with manganese using Mn(2)(CO)(10) or Mn(O(2)CMe)(2) without significant distortion of the host structure. The two products were catalytically active in propene oxidation, with SBA-15 modified with Mn(2)(CO)(10) showing significantly higher activity, possibly due to higher Mn content, than SBA-15 modified with Mn(O(2)CMe)(2).  相似文献   
395.

Problem

Whole-body vibration (WBV) is an occupational issue of concern due to adverse health effects or simple discomfort and annoyance. Unlike in Europe, WBV is an emerging topic in the U.S. safety and health (S&H) professional community. We hypothesized that at least one-half of the U.S. occupational S&H professionals knew little or nothing about WBV.

Method

We conducted a cross-sectional study (survey) of WBV knowledge among members of the American Society of Safety Engineers. A Likert scale (1-none to 5-expert) was used to determine WBV topic knowledge levels (KL1-5).

Results

Analysis of 2,764 responses revealed that 69.5% of the participants self-reported a less than basic WBV understanding. The WBV KL1-5 mean for all participants was 1.94 ± 1.00, corresponding to an awareness of WBV without a depth of understanding.

Summary

Many at-risk U.S. workers may not be supported by occupational S&H professionals with adequate WBV knowledge.

Impact on Industry

A significant number of U.S. workers may be exposed to unhealthy levels of whole-body vibration. However, the U.S. occupational safety and health community is generally unprepared to anticipate, monitor, and control the whole-body vibration hazard.  相似文献   
396.
397.
398.
Since the United Nations Conference on Environment and Development in 1992 in Rio de Janeiro, sustainable development became an important issue. Sustainable development often focuses on a single sector or parameter such as tourism, energy supply, water management, different aspects of nature conservation, or economy. In this paper, we provide a comprehensive picture of the development of a region since the Middle Ages and discuss whether this development can be evaluated as socially, economically and ecologically sustainable. We carried out a combined qualitative–quantitative assessment where we use quantitative data and indicators when available, as well as literature sources and expert knowledge from the region for a qualitative assessment. We judge that generally a sustainable development in the Allgäu region can be found, although also some critical points and contentious issues exist. An overall good economic and income situation for most people, the good ecological conditions and rich biodiversity, the relatively well-established social structure, as well as the identity of the people with the region and comparatively low social discrepancy, can be positively stated. In contrast, different actual and future threats exist such as new or planned infrastructure, increasing traffic or tourism activities in certain areas that degrade habitats and reduce species richness, intensification of agriculture in certain areas, but also abandonment of agriculture in other areas, loss of traditions and customs, and declining numbers of smallholders. The objective for the region would be to minimise these negative impacts and reinforce positive trends to assure the sustainable development of the Allgäu.  相似文献   
399.
Megacities are not only important drivers for socio-economic development but also sources of environmental challenges. Many megacities and large urban agglomerations are located in the coastal zone where land, atmosphere, and ocean meet, posing multiple environmental challenges which we consider here. The atmospheric flow around megacities is complicated by urban heat island effects and topographic flows and sea breezes and influences air pollution and human health. The outflow of polluted air over the ocean perturbs biogeochemical processes. Contaminant inputs can damage downstream coastal zone ecosystem function and resources including fisheries, induce harmful algal blooms and feedback to the atmosphere via marine emissions. The scale of influence of megacities in the coastal zone is hundreds to thousands of kilometers in the atmosphere and tens to hundreds of kilometers in the ocean. We list research needs to further our understanding of coastal megacities with the ultimate aim to improve their environmental management.  相似文献   
400.
This article reviews interactions and health impacts of physical, chemical, and biological weather. Interactions and synergistic effects between the three types of weather call for integrated assessment, forecasting, and communication of air quality. Today’s air quality legislation falls short of addressing air quality degradation by biological weather, despite increasing evidence for the feasibility of both mitigation and adaptation policy options. In comparison with the existing capabilities for physical and chemical weather, the monitoring of biological weather is lacking stable operational agreements and resources. Furthermore, integrated effects of physical, chemical, and biological weather suggest a critical review of air quality management practices. Additional research is required to improve the coupled modeling of physical, chemical, and biological weather as well as the assessment and communication of integrated air quality. Findings from several recent COST Actions underline the importance of an increased dialog between scientists from the fields of meteorology, air quality, aerobiology, health, and policy makers.  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