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   367篇
  免费   1篇
  国内免费   4篇
安全科学   3篇
废物处理   13篇
环保管理   11篇
综合类   127篇
基础理论   95篇
污染及防治   89篇
评价与监测   12篇
社会与环境   22篇
  2018年   7篇
  2017年   10篇
  2016年   9篇
  2015年   8篇
  2014年   10篇
  2013年   8篇
  2012年   7篇
  2011年   12篇
  2010年   14篇
  2009年   16篇
  2008年   13篇
  2007年   22篇
  2006年   19篇
  2005年   16篇
  2004年   6篇
  2003年   6篇
  2002年   4篇
  2001年   11篇
  2000年   6篇
  1999年   8篇
  1998年   3篇
  1997年   11篇
  1996年   4篇
  1995年   6篇
  1994年   9篇
  1993年   3篇
  1990年   5篇
  1989年   6篇
  1986年   7篇
  1983年   5篇
  1982年   4篇
  1978年   3篇
  1977年   6篇
  1976年   11篇
  1975年   4篇
  1974年   4篇
  1968年   2篇
  1966年   4篇
  1965年   3篇
  1963年   2篇
  1961年   4篇
  1960年   2篇
  1957年   3篇
  1955年   2篇
  1922年   3篇
  1920年   2篇
  1919年   3篇
  1918年   2篇
  1914年   2篇
  1913年   2篇
排序方式: 共有372条查询结果,搜索用时 31 毫秒
1.
Abstract

Objective: With the overall goal to harmonize prospective effectiveness assessment of active safety systems, the specific objective of this study is to identify and evaluate sources of variation in virtual precrash simulations and to suggest topics for harmonization resulting in increased comparability and thus trustworthiness of virtual simulation-based prospective effectiveness assessment.

Methods: A round-robin assessment of the effectiveness of advanced driver assistance systems was performed using an array of state-of-the-art virtual simulation tools on a set of standard test cases. The results were analyzed to examine reasons for deviations in order to identify and assess aspects that need to be harmonized and standardized. Deviations between results calculated by independent engineering teams using their own tools should be minimized if the research question is precisely formulated regarding input data, models, and postprocessing steps.

Results: Two groups of sources of variations were identified; one group (mostly related to the implementation of the system under test) can be eliminated by using a more accurately formulated research question, whereas the other group highlights further harmonization needs because it addresses specific differences in simulation tool setups. Time-to-collision calculations, vehicle dynamics, especially braking behavior, and hit-point position specification were found to be the main sources of variation.

Conclusions: The study identified variations that can arise from the use of different simulation setups in assessment of the effectiveness of active safety systems. The research presented is a first of its kind and provides significant input to the overall goal of harmonization by identifying specific items for standardization. Future activities aim at further specification of methods for prospective assessments of the effectiveness of active safety, which will enhance comparability and trustworthiness in this kind of studies and thus contribute to increased traffic safety.  相似文献   
2.
A site contaminated by mercury serves as an example for evaluating the environmental medicine aspects of mercury emissions on individuals living in the surroundings. Based on defined, conventional scenarios, estimations of internal exposure were made for seven different age groups and with regard to such contact media as soil, air and food. Using human monitoring methods, an attempt was made to compare the epidemiological results. The site-specific and pathway-specific estimation of exposure is based on a multitude of various samples as well as on measurements of concentrations in the compartments relevant for intake. As based upon rigid guideline values, both these calculations and the epidemiological investigations reveal a slight increase in the mercury exposure.  相似文献   
3.
4.
5.
6.
7.
8.
A high-precision seismic reflection method has been developed for investigating archeological objects which are hidden in a mud-layer of the Haddebyer Noor, a lake in front of the old Viking settlement Haithabu near Schleswig. Wooden and metallic objects larger than about 30 cm could be detected and mapped. Some of the mapped objects have been rescued by diving operations. Others, like wooden harbour constructions of unexpectedly large dimensions, and a large (second) shipwrack were left conserved in the mud. All finds provide a new picture of this old Viking settlement showing that its inhabitants had a far higher stage of development than hitherto suspected.  相似文献   
9.
Panorpa vulgaris   has become a model insect for testing theories of sexual selection. This contribution summarizes that which has been learned in recent years and presents new data that clearly show that the mating system of P. vulgaris is not simply a resource-defense polygyny, as has previously been thought. In P. vulgaris neither the pattern in food exploitation nor the ratio of variance in the lifetime reproductive success of the two sexes is in accordance with that expected in resource defense polygynous mating systems. Lifetime mating duration is the most important proximate determinant of male fitness. Males employing alternative mating tactics obtain copulations of varying duration in relation to the following sequence: saliva secretion  1  food offering  1  no gift. The number of salivary masses which males provide to females during their lifetime is significantly correlated with the lifetime condition index. The condition index depends on the fighting prowess of males and their ability to find food items. Thus saliva secretion of Panorpa is considered a Zahavian handicap, which can serve as an honest quality indicator used by mating females. Our results confirm four main predictions of the indicator model of the theory of sexual selection: (a) the indicator signals high ecological quality of its bearer, (b) the indicator value increases with phenotypic quality, (c) the indicator value is positively correlated with the genetic quality affecting offspring fitness in a natural selection context, and (d) the quality indicator is more costly for low- than for high-quality individuals. The evolutionary consequences of the mating pattern and the sperm competition mechanism in P. vulgaris are discussed in the context the way in which sexual selection creates and maintains sperm mixing and the evolution of a promiscuous mating system.  相似文献   
10.
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