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   1669篇
  免费   8篇
  国内免费   8篇
安全科学   15篇
废物处理   73篇
环保管理   86篇
综合类   543篇
基础理论   397篇
污染及防治   378篇
评价与监测   110篇
社会与环境   73篇
灾害及防治   10篇
  2018年   13篇
  2017年   23篇
  2016年   24篇
  2015年   13篇
  2014年   24篇
  2013年   74篇
  2012年   25篇
  2011年   54篇
  2010年   48篇
  2009年   55篇
  2008年   69篇
  2007年   55篇
  2006年   49篇
  2005年   49篇
  2004年   43篇
  2003年   42篇
  2002年   50篇
  2001年   60篇
  2000年   55篇
  1999年   35篇
  1998年   22篇
  1997年   32篇
  1996年   30篇
  1995年   30篇
  1994年   29篇
  1993年   27篇
  1992年   19篇
  1991年   38篇
  1990年   51篇
  1989年   23篇
  1988年   28篇
  1987年   21篇
  1985年   23篇
  1984年   22篇
  1983年   16篇
  1982年   30篇
  1979年   21篇
  1978年   14篇
  1977年   15篇
  1976年   14篇
  1974年   17篇
  1972年   17篇
  1971年   13篇
  1967年   23篇
  1966年   20篇
  1965年   13篇
  1964年   13篇
  1962年   13篇
  1958年   14篇
  1957年   12篇
排序方式: 共有1685条查询结果,搜索用时 15 毫秒
101.
This study tests a model that uses organizational justice variables and the personality trait of negative affectivity to explain two forms of deviant employee behavior. Prior research suggests that deviance can be directed interpersonally or against organizations. We propose a model that links unfavorable perceptions of distributive, procedural, and interactional justice, as well as the dispositional trait of negative affectivity, to both types of deviant acts. To test the model, a survey was distributed to employees from a government agency and an international manufacturer of paper products. Responses to the survey were analysed using structural equation modeling to evaluate the fit of the theoretical model to the data. Results showed that the model fits the data well and that nearly all of the hypothesized relations among constructs were supported. Implications of the results for the prediction and control of deviant behavior are discussed and future research directions are offered. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   
102.
103.
为了研究不同经验驾驶人在高速公路特长隧道环境下的注视转移特性,在高速公路特长隧道中开展实车实验,利用 iView X HED型眼动仪采集了32名不同经验驾驶人的眼动数据。运用动态聚类方法,对驾驶人注视区域进行划分,分析了职业与非职业驾驶员在高速公路隧道不同段与普通路段的注视转移规律与注意力分配特性。结果表明:相较于非职业驾驶人,职业驾驶员具有较强的注视前瞻性,且在隧道的不同段主要注视的区域因行车环境不同变化较小;驾驶人对同一目标需要重复注视才能提取足够的信息,且当行车环境复杂度增加或驾驶员驾驶经验不足时,重复注视概率增加;驾驶人在不同路段行车时,主要通过注视中间区域获取信息;行车环境与驾驶经验对驾驶人在中间近处、左侧区域及内后视镜区域的注视平稳分布存在显著的交互作用。  相似文献   
104.
Asplenia associated with situs ambiguus, symmetric liver, bilateral trilobulated lungs, and a complex heart defect was diagnosed on autopsy in a 14-day-old infant. Furthermore, examination of the brain displayed agenesis of the corpus callosum (ACC) with pachygyria and hydrocephalus. The characteristic association of asplenia with visceroatrial heterotaxia is traditionally named after the Swedish pediatrician, Ivemark. Although exceptional, association of Ivemark syndrome with callosal agenesis has been reported recently. The concept of ‘developmental fields’ describes morphogenetically reactive units of the embryo determining and controlling the development of complex structures in a hierarchical manner. Lateralization defects such as situs inversus, asplenia or polysplenia due to defective left–right axis development, as well as decussation defects such as ACC, are considered as defects of the primary developmental field. Therefore, additional callosal agenesis in Ivemark syndrome may be a coherent and synchronic defect in the primary developmental field rather than a causally independent malformation. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   
105.
In this paper two different approaches for predicting the heating-up of an acetylene cylinder involved in a fire and the afterward cooling with water are presented. In the simulations polynomial functions were used to describe the temperature dependency of the thermal properties of the cylinder interior, which is a complex system composed by a solid porous material, a solvent (typically acetone) and acetylene dissolved in it. Model equations covered heat conduction in the cylinder interior and at its walls. In the first approach the cylinder surroundings were simulated as a further domain constituted by CO2, during the fire exposure, and for water, during the cooling. In this domain the coupled heat transfer (convection and conduction) and the momentum equation (Navier–Stokes) were solved. In the second approach no further domain was considered but boundary conditions were set directly on the cylinder walls. Results of the calculations performed with both approaches are presented. This work could prove helpful in predicting to which extent the interior of an acetylene cylinder exposed to fire reaches temperatures capable of initiating the decomposition of acetylene and to determine how long a water cooling should be applied, so that the system is brought again under non-critical conditions.  相似文献   
106.
Background, aim, and scope Polycyclic aromatic hydrocarbons (PAH) result from incomplete combustion of almost every organic materials, e.?g. due to forest fires, residential heating, combustion engines, grilling, or smoking. PAH are predominantly distributed over the air-path. Their usage in products (e.?g. moth-balls) has been limited strictly or completely forbidden in the past. In the context of the EU Water Framework Directive (WFD), the single substances anthracene, fluoranthene and naphthalene, as well as PAHs as group of substances, are listed as “priority” substances. Background of this work is a first compilation of sources of PAH emissions, and in this context, the collection of all relevant data and information to calculate the total emissions into surface waters in Germany. Materials and methods Within the scope of diverse research projects, funded by the German Environmental Agency, the available data material concerning PAH input in surface waters has been analyzed by the Fraunhofer Institute for Systems and Innovation Research. On the basis of the collected data, a first evaluation of relevance of the different sources has been conducted using the model MONERIS. Results As a result of the atmospheric deposition, PAHs enter, to a large extent, surface waters directly or indirectly through surface runoff (e.?g. urban areas, wastewater treatment plants, erosion). Discussion Although there is still additional research need for some of the covered PAH sources, a noticeable distribution pattern of relevance emerges. Conclusions The scenarios, based on the currently known sources, show that the implementation or the neglect of emission reduction measures in the field of diffuse air-borne PAHs are crucial for the further development of the deposition of PAHs in surface waters. More far-reaching studies are necessary, e.?g. concerning emissions from inland navigation/motor boats, the inhomogeneous source “products”, or the path “erosion”. Recommendations and perspectives According to the EU-WFD, all depositions, emissions and losses of “priority hazardous” classified substances, such as the group of PAHs, have to be stopped or gradually finished in the long term. Until the year 2015, environmental quality standards (EQS) have to be met for all “priority substances”. Presently, the EQS often are not completely fulfilled for many substances of the PAH group, including benzo(a)pyrene. Reduction measures are necessary within diverse areas, especially concerning diffuse atmospheric emissions (e.?g. “residential heating”).  相似文献   
107.
本文主要研究了肯尼亚姆瓦彻湾(属于浅潮滩红树林湿地)泥沙交换的动力机制.该港湾属于半日潮,大、小潮的潮差分别为.2m和1.4m,大潮高水位的水面面积为17km2.  相似文献   
108.
Microorganisms (bacteria, fungi) are common residents of the roots, stems and leaves of higher plants. In order to explore the dependency of plant development on the presence of epiphytic microorganisms, the achenes (seeds) of sunflower (Helianthus annuus L.) were sterilized and germinated under aseptic conditions. The sterility of the seedlings was determined with the agar impression method. In seedlings from non-sterile seeds (control) that were likewise raised in a germ-free environment, all plant organs investigated (stem, cotyledons and primary leaves) were contaminated with bacteria. Hypocotyl elongation was not affected by epiphytic microorganisms. However, the growth rates of the cotyledons and primary leaves were higher in sterile seedlings compared with the control. The implications of this differential inhibition of organ development by epiphytic bacteria that are transmitted via the outer surface of the seed coat are discussed. We conclude that epiphytes in the above-ground phytosphere are not necessary for the development of the sunflower seedling.  相似文献   
109.
110.
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