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   181篇
  免费   7篇
  国内免费   13篇
安全科学   29篇
废物处理   8篇
环保管理   40篇
综合类   39篇
基础理论   31篇
污染及防治   36篇
评价与监测   9篇
社会与环境   3篇
灾害及防治   6篇
  2024年   1篇
  2023年   1篇
  2022年   3篇
  2021年   1篇
  2020年   1篇
  2019年   2篇
  2018年   5篇
  2017年   2篇
  2016年   8篇
  2015年   8篇
  2014年   13篇
  2013年   15篇
  2012年   7篇
  2011年   9篇
  2010年   8篇
  2009年   11篇
  2008年   15篇
  2007年   12篇
  2006年   11篇
  2005年   8篇
  2004年   9篇
  2003年   9篇
  2002年   3篇
  2001年   5篇
  2000年   4篇
  1999年   1篇
  1998年   6篇
  1997年   2篇
  1996年   1篇
  1995年   2篇
  1994年   3篇
  1993年   2篇
  1992年   3篇
  1991年   2篇
  1990年   1篇
  1989年   1篇
  1988年   4篇
  1980年   1篇
  1972年   1篇
排序方式: 共有201条查询结果,搜索用时 15 毫秒
121.
Abstract:  International wildlife crime is burgeoning in this climate of global trade. We contend that the most effective way to contain this illegal trade is to determine where the wildlife is being removed. This allows authorities to direct law enforcement to poaching hot spots, potentially stops trade before the wildlife is actually killed, prevents countries from denying their poaching problems at home, and thwarts trade before it enters into an increasingly complex web of international criminal activity. Forensic tools have been limited in their ability to determine product origin because the information they can provide typically begins only at the point of shipment. DNA assignment analyses can determine product origin, but its use has been limited by the inability to assign samples to locations where reference samples do not exist. We applied new DNA assignment methods that can determine the geographic origin(s) of wildlife products from anywhere within its range. We used these methods to examine the geographic origin(s) of 2 strings of seizures involving large volumes of elephant ivory, 1 string seized in Singapore and Malawi and the other in Hong Kong and Cameroon. These ivory traffickers may comprise 2 of the largest poaching rings in Africa. In both cases all ivory seized in the string had common origins, which indicates that crime syndicates are targeting specific populations for intense exploitation. This result contradicts the dominant belief that dealers are using a decentralized plan of procuring ivory stocks as they became available across Africa. Large quantities of ivory were then moved, in multiple shipments, through an intermediate country prior to shipment to Asia, as a risk-reduction strategy that distances the dealer from the poaching locale. These smuggling strategies could not have been detected by forensic information, which typically begins only at the shipping source.  相似文献   
122.
Abstract: The probability and time of extinction of taxa is often inferred from statistical analyses of historical records. Many of these analyses require the exclusion of multiple records within a unit of time (i.e., a month or a year). Nevertheless, spatially explicit, temporally aggregated data may be useful for identifying clusters of sightings (i.e., sighting clusters) in space and time. Identification of sighting clusters highlights changes in the historical recording of endangered taxa. I used two methods to identify sighting clusters in historical records: the Ederer–Myers–Mantel (EMM) test and the space–time permutation scan (STPS). I applied these methods to the spatially explicit sighting records of three species of orchids that are listed as endangered in the Republic of Ireland under the Wildlife Act (1976): Cephalanthera longifolia, Hammarbya paludosa, and Pseudorchis albida. Results with the EMM test were strongly affected by the choice of the time interval, and thus the number of temporal samples, used to examine the records. For example, sightings of P. albida clustered when the records were partitioned into 20‐year temporal samples, but not when they were partitioned into 22‐year temporal samples. Because the statistical power of EMM was low, it will not be useful when data are sparse. Nevertheless, the STPS identified regions that contained sighting clusters because it uses a flexible scanning window (defined by cylinders of varying size that move over the study area and evaluate the likelihood of clustering) to detect them, and it identified regions with high and regions with low rates of orchid sightings. The STPS analyses can be used to detect sighting clusters of endangered species that may be related to regions of extirpation and may assist in the categorization of threat status.  相似文献   
123.
Abstract

In the last few years, marked progress has been made in the development of methods for evaluating the mutagenic and carcinogenic potential of pesticide chemicals. The correlation of genetic and related biological activity in short‐term tests with carcinogenic activity in whole animals allows the utilization of short‐term mutagenicity bioassays to prescreen chemicals for effects related to mutation induction and presumptive carcinogenicity. In addition, bioassays now available can measure directly the chemical transformation of normal cells in culture into cells capable of producing tumors when injected into animals.

This paper will review briefly the major types of relevant short‐term tests and will develop a rationale for a phased approach to the evaluation of the mutagenic and carcinogenic potential of environmental chemicals. This approach involves the sequential application of bioassays which are organized into a three‐level matrix emphasizing first detection, then confirmation, and finally hazard assessment. Chemicals demonstrating positive results in the short‐term detection systems and confirmatory bioassays are pursued in higher level whole animal tests. A core battery of tests is proposed to operationally define a negative result. The phased approach should facilitate a cost effective utilization of limited testing resources and provide protection for human health in proportion to the anticipated hazard.

Results obtained in evaluating a series of thirty‐eight pesticide chemicals according to the phased approach are discussed in detail.  相似文献   
124.
通过试验分析确定了原子荧光光谱法测定水样中砷的检测条件,并在优化试验条件下与现行砷的国家标准分析方法GB 7485-87进行了样品分析比对实验,试验表明,该方法操作简单方便,历时短,可大大提高检测效率,完全可以代替分析操作复杂繁琐的现行国家标准分析方法。  相似文献   
125.
ABSTRACT: The interesting developments in non-parainetric testing and estimation methods presented in the upcoming sequence of nine papers are evaluated, compared, and put into proper perspective. Because a deterioration in water quality constitutes a direct threat to human health, it is of utmost importance to have flexible non-parametric methods available for detecting and describing trends in water quality time series. A distinct advantage of nonparametric tests is that they are usually very effective when applied to “messy” environmental data which may, for example, contain many missing observations and not be normally distributed. By applying their enhanced approaches for nonparametric methods to water quality time series, as well as employing well designed simulation experiments, the authors of the papers clearly demonstrate the efficacy of utilizing nonparametric tests in environmental impact assessment.  相似文献   
126.
阐述了温度试验在军工产品研制生产中的重要地位和用途,温度环境对装备的主要影响和典型故障模式;介绍了GJB 150/150A、HB 6167/6167A、GB/T 2423等我国主要军用、民用环境试验系列标准中包括的各种典型温度试验程序及其用途和模拟的环境;说明了各种典型试验程序规定或要求的温度试验各种特点和剪裁方法,并汇总列于一个表格中,以便于查阅,列出了温度试验标准中对温度试验箱和测试仪器仪表的要求,最后讨论了受试产品温度稳定、温度试验箱的选用,确保受试产品经受正确的温度条件、受试产品温度响应测量和温度试验中断处理等技术。本文分为四大部分:第一部分阐述温度对装备的影响、故障机理和温度试验的重要性;第二部分阐述了GJB150/150A、HB 6167/6167A和GB/T 2423等主要环境试验标准中的典型温度试验程序;第三部分详细说明了各种温度试验的试验温度和试验持续时间及其区别和剪裁方法;第四部分介绍了各种标准对温度试验设备的要求,温度试验设定点,确保试验温度准确施加和试验中断处理等温度试验技术。本文为其中第一部分。  相似文献   
127.
The goal of theoretical research is to establish parameters, which have to be given in standards for percussive tests of products. Those parameters are essential for each user to be able to construct identical (equivalent) testing equipment. This would ensure identical results for identical products.

The paper presents a detailed analysis of the distribution and the value of the forces generated during percussive collisions of two bodies. Elastic, plastic, and elastoplastic collisions are considered. Parameters determining the coefficient of restitution, the courses of energy, momenta, and the values of the forces in colliding elements are determined. The dynamic force acting on a product during a percussive test was studied.  相似文献   
128.
Limitation of forces can be a simple measure to safeguard crushing points at doors, machines, and vehicles. In this connection different standards define a threshold force value of 150 N. This widely accepted value refers to static forces only. The dynamic forces that arise from impact on a person are frequently ignored, although they are generally higher than the static forces.

The article describes an instrument for the measurement of static and dynamic crushing forces. This instrument has a stiffness that approximates the average stiffness of human fingers as one of the most at-risk parts of the human body with regard to crushing injuries. Sensory tests were carried out to define dynamic forces considered admissible at crushing points.  相似文献   
129.
异噻唑啉酮的灭藻效应及其生物毒性试验   总被引:4,自引:0,他引:4  
研究了异噻唑啉酮在海水中的灭藻效应,确定了其对于代表性藻类的浓度-反应关系,并且对其进行了生物毒性试验。根据试验结果采用概率单位法进行数据处理,得出异噻唑啉酮对卤虫无节幼体96 h的半致死浓度(LC50)为10.4 mg/L,并对剂量反应方程进行x2检验,结果表明符合精度要求,计算出的96h-LC50真实可靠。该杀生剂在低浓度下对海洋单细胞藻类有较高的杀灭效应,而且生物毒性较小,是比较适合化学法处理船舶压载水的杀生剂。  相似文献   
130.
The focus of environmental regulations has changed significantly since the introduction of the bioassay as a standard means of assessing environmental impact. Prominent in this change is an increasing emphasis on protecting the integrity of natural ecosystems, which incorporate community- and system-level properties as well as organismal and population processes. Consequently, support for the use of multispecies testing has widened to include not only ecologists in academia but environmental scientists in the regulatory and industrial sector as well. The reason for this trend is clear: the additional environmental realism gained from tests utilizing communities of organisms allows for greater insight into the potential hazard of chemicals and other forms of human activity to natural ecosystems that cannot be obtained from single species tests alone. Many of the problems cited for multispecies testing early in their evolution as a hazard assessment tool have been refuted or overcome. In particular, the u  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