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   239篇
  免费   4篇
安全科学   21篇
废物处理   5篇
环保管理   27篇
综合类   46篇
基础理论   64篇
污染及防治   51篇
评价与监测   17篇
社会与环境   8篇
灾害及防治   4篇
  2024年   1篇
  2023年   5篇
  2022年   4篇
  2021年   14篇
  2020年   2篇
  2019年   4篇
  2018年   6篇
  2017年   11篇
  2016年   22篇
  2015年   10篇
  2014年   4篇
  2013年   20篇
  2012年   17篇
  2011年   13篇
  2010年   9篇
  2009年   9篇
  2008年   12篇
  2007年   15篇
  2006年   14篇
  2005年   1篇
  2004年   8篇
  2003年   7篇
  2002年   8篇
  2001年   2篇
  2000年   2篇
  1999年   2篇
  1998年   2篇
  1997年   1篇
  1996年   1篇
  1995年   1篇
  1994年   4篇
  1991年   1篇
  1990年   1篇
  1989年   2篇
  1988年   1篇
  1986年   2篇
  1984年   1篇
  1983年   1篇
  1982年   1篇
  1981年   1篇
  1973年   1篇
排序方式: 共有243条查询结果,搜索用时 15 毫秒
151.
Red sesbania is an invasive South American shrub that has rapidly expanded its range along California waterways, emphasizing the need to prioritize eradication sites at a regional scale. To accomplish this, we updated baseline location data in summer 2010 using field surveys throughout the state. We collected relevant GPS attribute data for GIS analysis and eradication prioritization modeling. The regional survey identified upstream and downstream extents for each watershed, as well as outliers in urban areas. We employed the Weed Heuristics: Invasive Population Prioritization for Eradication Tool (WHIPPET) to prioritize red sesbania sites for eradication, and revised the WHIPPET model to consider directional propagule flow of a riparian species. WHIPPET prioritized small populations isolated from larger infestations, as well as outliers in residential areas. When we compared five experts’ assessments of a stratified sample of the red sesbania populations to WHIPPET’s prioritization results, there was a positive, but nonsignificant, correlation. The combination of WHIPPET and independent expert opinion suggests that small, isolated populations and upstream source populations should be the primary targets for eradication. Particular attention should be paid to these small populations in watersheds where red sesbania is a new introduction. The use of this model in conjunction with evaluation by the land manager may help prevent the establishment of new seed sources and protect uninfested riparian corridors and their adjacent watersheds.  相似文献   
152.
153.
154.
155.
156.
The 350 nm UV-illuminated slurries of titanium dioxide were used to study the photocatalyzed degradation kinetics of dissolved organic carbon (DOC) as water contaminants. The initial rate data were well described by the Langmuir-Hinshelwood rate equation and the simplified Langmuir-Hinshelwood rate equation (i.e., ln(C0/C)=K′t). The latter will be more easily used for predicting the degradation of DOC concentration at various elapsed times. In different DOC initial concentrations the apparent first-order rate constant (K′) decreased and half-life increased when the initial DOC concentration decreased. The Langmuir-Hinshelwood rate form will be the most convenient to describe the oxidation rate of DOC in the drinking water resources, if it is as brief as v=kKC.  相似文献   
157.
The classic sonographic appearance of the kidneys in fetuses with autosomal recessive polycystic kidney disease (ARPKD) has been well described. We report a case of enlarged kidneys with pyramidal hyperechogenicity quite similar to medullary nephrocalcinosis found in a fetus at 34 weeks' gestation. At 39 weeks, a female neonate was delivered and died after 22 h due to pulmonary insufficiency secondary to severe oligohydramnios. On pathological analysis, the gross and microscopic findings were typical of ARPKD with diffuse dilatation of tubules throughout. The fetal renal lobulation was prominent and on section, the pyramids were delineated within each lobule, accounting for the clear image of the pyramids observed on sonography. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
158.
A rapid, sensitive, and cost-effective analytical method was developed for the analysis of selected semi-volatile organic compounds in water. The method used an automated online solid-phase extraction technique coupled with programmed-temperature vaporization large-volume injection gas chromatography/mass spectrometry. The water samples were extracted by using a fully automated mobile rack system based on x-y-z robotic techniques using syringes and disposable 96-well extraction plates. The method was validated for the analysis of 30 semivolatile analytes in drinking water, groundwater, and surface water. For a sample volume of 10 mL, the linear calibrations ranged from 0.01 or 0.05 to 2.5 ??g·L?1, and the method detection limits were less than 0.1 ??g·L?1. For the reagent water samples fortified at 1.0 ??g·L?1 and 2.0 ??g·L?1, the obtained mean absolute recoveries were 70%?C130% with relative standard deviations of less than 20% for most analytes. For the drinking water, groundwater, and surface water samples fortified at 1.0 ??g·L?1, the obtained mean absolute recoveries were 50%?C130% with relative standard deviations of less than 20% for most analytes. The new method demonstrated three advantages: 1) no manipulation except the fortification of surrogate standards prior to extraction; 2) significant cost reduction associated with sample collection, shipping, storage, and preparation; and 3) reduced exposure to hazardous solvents and other chemicals. As a result, this new automated method can be used as an effective approach for screening and/or compliance monitoring of selected semi-volatile organic compounds in water.  相似文献   
159.
Virgin plastic pellets and plastic fragments are reported as ubiquitous beach contaminants in the peer-reviewed literature. A surface density of 0.3 virgin plastic pellets and plastic fragments per square centimeter of the strandline area was registered on an urban beach of the northeast of Brazil. This beach is presently not affected by petrochemical facilities or pellet processing plants. The main source of fragments (96.7%) was attributed to the breaking down of larger plastic items deposited on the beach. In the case of virgin plastic pellets (3.3%), the main sources were the marine environment and possibly nearby port facilities. This category of plastic pollutant offers particular threats to the marine environment and to beach users.  相似文献   
160.
Many researchers have used the insider–outsider distinction when discussing employment relationships (e.g., Graen & Scandura, 1987; Pfeffer & Baron, 1988). However, there is no known empirical research directly assessing employees' perceptions of their status as organizational insiders. This article is intended as an initial step to theoretically and empirically explore the concept of perceived insider status (PIS). First, we build theoretical arguments describing how organizations may differentiate between insider and outsider employees, leading to differences in perceptions of insider status. We then hypothesize and show empirical evidence that contrasts, but relates, actual inclusion and perceived organizational support to PIS. We subsequently examine two types of discretionary employee behavior, altruism and production deviance, as potential consequences of PIS. Our results suggest that both actual inclusion, as well as perceived insider status, have implications for organizational functioning via discretionary employee behaviors. Copyright © 2002 John Wiley & Sons, Ltd.  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