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   454篇
  免费   6篇
  国内免费   2篇
安全科学   5篇
废物处理   29篇
环保管理   63篇
综合类   66篇
基础理论   96篇
污染及防治   149篇
评价与监测   32篇
社会与环境   19篇
灾害及防治   3篇
  2023年   2篇
  2022年   10篇
  2021年   6篇
  2020年   7篇
  2019年   6篇
  2018年   22篇
  2017年   9篇
  2016年   19篇
  2015年   12篇
  2014年   24篇
  2013年   55篇
  2012年   11篇
  2011年   25篇
  2010年   28篇
  2009年   19篇
  2008年   25篇
  2007年   33篇
  2006年   23篇
  2005年   11篇
  2004年   17篇
  2003年   10篇
  2002年   18篇
  2001年   10篇
  2000年   5篇
  1999年   4篇
  1998年   3篇
  1997年   4篇
  1996年   5篇
  1995年   3篇
  1994年   4篇
  1993年   2篇
  1992年   3篇
  1991年   4篇
  1990年   2篇
  1988年   2篇
  1987年   1篇
  1986年   2篇
  1985年   1篇
  1984年   2篇
  1983年   2篇
  1982年   1篇
  1981年   1篇
  1979年   3篇
  1973年   1篇
  1970年   1篇
  1969年   1篇
  1967年   2篇
  1939年   1篇
排序方式: 共有462条查询结果,搜索用时 250 毫秒
211.
The influence of fetal gender on the level in the first trimester of the serological markers alpha-fetoprotein (AFP), pregnancy-associated plasma protein-A (PAPP-A) and free beta human chorionic gonadotropin (βhCG) and on nuchal translucency is described for 2637 singleton pregnancies with normal outcome. Mean log MoM values for pregnancies with female and male fetuses were calculated using regression of log marker values on gestational age expressed as crown rump length and on maternal weight. A pronounced gender impact was found for free βhCG, being 16% higher for female than for male fetuses. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   
212.
213.
The results of recent studies by our group have suggested that in social wasps of the genus Polistes the Dufour’s gland is involved in kin recognition. In fact, the same hydrocarbons occurring on the cuticle are found in the gland secretion, and in P. dominulus the composition of the glandular secretion is more similar in foundresses belonging to the same colonies than in heterocolonial foundresses. In this study, P. dominulus colonies were experimentally presented with previously treated dead conspecific females. These lures had been deprived of their epicuticular lipids and coated with epicuticular or Dufour’s gland secretion extracts from females hetero- or homocolonial with respect to the tested colonies. The behaviour of the colonies towards these lures indicates that, like the epicuticular lipids, the Dufour’s gland secretion is involved in nestmate recognition. Received: 14 August 1995/Accepted after revision: 5 November 1995  相似文献   
214.
In-air hearing in birds has been thoroughly investigated. Sound provides birds with auditory information for species and individual recognition from their complex vocalizations, as well as cues while foraging and for avoiding predators. Some 10% of existing species of birds obtain their food under the water surface. Whether some of these birds make use of acoustic cues while underwater is unknown. An interesting species in this respect is the great cormorant (Phalacrocorax carbo), being one of the most effective marine predators and relying on the aquatic environment for food year round. Here, its underwater hearing abilities were investigated using psychophysics, where the bird learned to detect the presence or absence of a tone while submerged. The greatest sensitivity was found at 2 kHz, with an underwater hearing threshold of 71 dB re 1 μPa rms. The great cormorant is better at hearing underwater than expected, and the hearing thresholds are comparable to seals and toothed whales in the frequency band 1–4 kHz. This opens up the possibility of cormorants and other aquatic birds having special adaptations for underwater hearing and making use of underwater acoustic cues from, e.g., conspecifics, their surroundings, as well as prey and predators.  相似文献   
215.
Ecosystem functioning is intimately linked to its physical environment by complex two-way interactions. These two-way interactions arise because vegetation both responds to the external environment and actively regulates its micro-environment. By altering stomatal aperture, and therefore the transpiration rate, plants modify soil moisture and atmospheric humidity and these same physical variables, in return, modify stomatal conductance. Relationships between biotic and abiotic components are particularly strong in closed, managed environments such as greenhouses and growth chambers, which are used extensively to investigate ecosystem responses to climatic drivers. Model-assisted designs that account for the physiological dynamics governing two-way interactions between biotic and abiotic components are absent from many ecological studies. Here, a general model of the vegetation-atmosphere system in closed environments is proposed. The model accounts for the linked carbon-water physiology, the turbulent transport processes, and the energy and radiative transfer within the vegetation. Leaf gas exchange is modeled using a carbon gain optimization approach that is coupled to leaf energy balance. The turbulent transport within the canopy is modeled in two-dimensions using first-order closure principles. The model is applied to the Lysimeter CO2 Gradient (LYCOG) facility, wherein a continuous gradient of atmospheric CO2 is maintained on grassland assemblages using an elongated chamber where the micro-climate is regulated by variation in air flow rates. The model is employed to investigate how species composition, climatic conditions, and the imposed air flow rate affect the CO2 concentration gradient within the LYCOG and the canopy micro-climate. The sensitivity of the model to key physiological and climatic parameters allows it to be used not only to manage current experiments, but also to formulate novel ecological hypotheses (e.g., by modeling climatic regimes not currently employed in LYCOG) and suggest alternative experimental designs and operational strategies for such facilities.  相似文献   
216.
Environmental Science and Pollution Research - In many countries, water supplies are limited and must be managed for different uses. Providing additional resources for irrigation can be an...  相似文献   
217.
218.
In order to meet a growing need to determine the condition of the nation's ecosystems and how their condition is changing, the U.S. Environmental Protection Agency (EPA) developed EMAP, the Environmental Monitoring and Assessment Program. A common survey design serves as the foundation on which to base monitoring of status and trends among diverse ecosystem types. In this paper, we describe the need for a statistically based survey design, briefly summarize the basic EMAP design, describe how that design is tailored for the selection of a probability sample of lakes on which to make measurements of lake condition, and illustrate the process for selecting a sample of lakes in the northeastern United States. Finally, we illustrate how measurements taken on the sample of lakes can be summarized, with known uncertainty, to describe the condition of a population of lakes.The U.S. Government right to retain a non-exclusive, royalty free licence in and to any copyright is acknowledged.  相似文献   
219.
A study of the use of car and public transport among residents in 30 residential areas in Greater Oslo indicates that urban planning variables have a significant influence on the energy use per capita for local transport. Residents in local communities with a high density and a short distance to downtown Oslo travel considerably shorter distances and use considerably less energy per capita than those who live in low-density, outer areas. This is true also when the effects of other variables are neutralized. The influence of urban planning variables on the modal split is lower than on energy use. The distribution between public and private transport is influenced most of all by car ownership.  相似文献   
220.

Objective

This study aimed to assess the diagnostic yield of prenatal genetic testing using trio whole exome sequencing (WES) and trio whole genome sequencing (WGS) in pregnancies with fetal anomalies by comparing the results with conventional chromosomal microarray (CMA) analysis.

Methods

A total of 40 pregnancies with fetal anomalies or increased nuchal translucency (NT ≥ 5 mm) were included between the 12th and 21st week of gestation. Trio WES/WGS and CMA were performed in all cases.

Results

The trio WES/WGS analysis increased the diagnostic yield by 25% in cases with negative CMA results. Furthermore, all six chromosomal aberrations identified by CMA were independently detected by WES/WGS analysis. In total, 16 out of 40 cases obtained a genetic sequence variant, copy number variant, or aneuploidy explaining the phenotype, resulting in an overall WES/WGS diagnostic yield of 40%. WES analysis provided a more reliable identification of mosaic sequence variants than WGS because of its higher sequencing depth.

Conclusions

Prenatal WES/WGS proved to be powerful diagnostic tools for fetal anomalies, surpassing the diagnostic yield of CMA. They have the potential to serve as standalone methods for prenatal diagnosis. The study highlighted the limitations of WGS in accurately detecting mosaic variants, which is particularly relevant when analyzing chorionic villus samples.  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