全文获取类型
收费全文 | 23092篇 |
免费 | 117篇 |
国内免费 | 100篇 |
专业分类
安全科学 | 389篇 |
废物处理 | 1277篇 |
环保管理 | 3049篇 |
综合类 | 3207篇 |
基础理论 | 6679篇 |
环境理论 | 7篇 |
污染及防治 | 4769篇 |
评价与监测 | 1788篇 |
社会与环境 | 2056篇 |
灾害及防治 | 88篇 |
出版年
2023年 | 68篇 |
2022年 | 104篇 |
2021年 | 109篇 |
2020年 | 91篇 |
2019年 | 100篇 |
2018年 | 1722篇 |
2017年 | 1606篇 |
2016年 | 1481篇 |
2015年 | 332篇 |
2014年 | 298篇 |
2013年 | 928篇 |
2012年 | 857篇 |
2011年 | 1959篇 |
2010年 | 1219篇 |
2009年 | 1167篇 |
2008年 | 1537篇 |
2007年 | 1933篇 |
2006年 | 479篇 |
2005年 | 539篇 |
2004年 | 411篇 |
2003年 | 521篇 |
2002年 | 547篇 |
2001年 | 506篇 |
2000年 | 377篇 |
1999年 | 220篇 |
1998年 | 159篇 |
1997年 | 162篇 |
1996年 | 172篇 |
1995年 | 201篇 |
1994年 | 201篇 |
1993年 | 165篇 |
1992年 | 141篇 |
1991年 | 175篇 |
1990年 | 167篇 |
1989年 | 158篇 |
1988年 | 123篇 |
1987年 | 118篇 |
1986年 | 121篇 |
1985年 | 94篇 |
1984年 | 128篇 |
1983年 | 124篇 |
1982年 | 123篇 |
1981年 | 117篇 |
1980年 | 102篇 |
1979年 | 114篇 |
1978年 | 74篇 |
1977年 | 78篇 |
1975年 | 76篇 |
1973年 | 73篇 |
1967年 | 66篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
992.
993.
Intrauterine fetal growth restriction (IUGR) is an important pregnancy complication associated with significant adverse clinical outcome, stillbirth, perinatal morbidity and cerebral palsy. To date, no uniformly accepted management protocol of Doppler surveillance that reduces mortality and cognitive morbidity has emerged. Aortic isthmus (AoI) evaluation has been proposed as a potential monitoring tool for IUGR fetuses. In this review, the current knowledge of the relationship between AoI Doppler velocimetry and preterm fetal growth restriction is reviewed. Relevant technical aspects and reproducibility data are reviewed as we discuss AoI Doppler and its place within the existing repertoire of Doppler assessments in placental insufficiency. The AoI is a link between the right and left ventricles which perfuse the lower and upper body, respectively. The clinical use of AoI waveforms for monitoring fetal deterioration in IUGR has been limited, but preliminary work suggests that abnormal AoI impedance indices are an intermediate step between placental insufficiency-hypoxemia and cardiac decompensation. Further prospective studies correlating AoI indices with arterial and venous Doppler indices and perinatal outcome are required before encorporating this index into clinical practice. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
994.
995.
Helvi Heinonen-Tanski Mariëlle SNEL Christine van Wijk-Sijbesma Avizit Reaz Quazi Kochurani Mathew Induka Werellagama Mujibur Rahman S.M.A. Rashid Palitha Jayaweera Helen Judith 《Environment, Development and Sustainability》2007,9(4):355-368
Environmental quality for environmental health has been examined visually by describing general conditions and drinking water
supply, sanitation and solid waste treatment conditions and practices in six South-East Asian villages with a dense population.
The environmental review was supplemented by discussions with local people and political and administrative decision makers.
Some drinking water analyses were done in order to show the water quality to the local people. The quality of the general
conditions and the conditions and practices of drinking water supply, excreta disposal and solid waste treatment practices
have been graded with the grading system presented below. The grading could be done in 1 or 2 days in each area by two persons,
of which one was an environmental scientist and the other a social scientist, who also knew the local culture and worked as
a translator. 相似文献
996.
997.
S. A. Poulet A. Cueff T. Wichard J. Marchetti C. Dancie G. Pohnert 《Marine Biology》2007,152(2):415-428
Observations of gonads and oocyte development stages (OS) have been achieved in Calanus helgolandicus females fed different algal diets and starved in filtered sea water under laboratory conditions during 8 days. The effects
of 20 diets on egg production rates (EPR), hatching success (HS) and proportion of abnormal larvae (AL, development stages
N1-2) were examined. With the control diet Prorocentrum minimum EPR and HS values were high, while AL was very low, coinciding with intact cell structures in oogonia (OO) and normal OS
(OS1-OS4). With the other diets, oocyte maturation, EPR, HS and AL patterns were partially or totally impaired. Decrease of
EPR coincided with the arrest of OS3 maturation and oocyte degradations, characterised by cell fragmentation, presence of
apoptotic bodies in the OS3, degradation of cytoplasm in OS3 and OS4 and consequently the arrest of OS4 formation. These degradations
were reversible when females were fed a favourable diet. Results reflect the presence of two distinct inhibitory mechanisms.
Inhibition mechanism (1) impairs egg production. It was induced by starvation or by several species belonging to Bacillariophyceae
(Chaetoceros calcitrans, Guinardia delicatula, Guinardia
striata, Odontella regia, Rhizosolenia setigera, Stephanopyxis turris, Thalassiosira pseudonana) and mixed-diatom assemblages (collected in the field) and to the prymnesiophyte Pavlova lutherii. Remarkably other diatoms like Navicula sp., Nitzschia sp., Skeletonema costatum and Thalassiosira rotula did not induce mechanism (1) Inhibitory mechanism (2) affected exclusively HS and AL and was triggered by species independent
of the production of polyunsaturated aldehydes (PUA), which are supposed to have adverse impacts on HS and larval development. 相似文献
998.
A. P. Galanina 《Russian Journal of Ecology》2008,39(6):418-424
The population density and relative abundance of some bird species reach the highest values in the communities of habitats with a high degree of anthropogenic transformation. The species diversity of birds shows an inverse correlation with the index of anthropogenic impact (in grades) calculated with regard to a number of parameters. Relevant correlations change periodically, with the correlation coefficient reaching the highest values in the nesting period and decreasing to a minimum during the flight period. 相似文献
999.
Qinhua Fang Luoping Zhang Huasheng Hong Liyu Zhang Frances Bristow 《Environment, Development and Sustainability》2008,10(1):41-49
Environmental planning at different levels has been called for by environmental departments in China during last years to
integrate environment consideration to economic development. Based on the accomplished environmental planning practice in
Xiamen China, the paper suggests a general environmental planning process with ecological function zoning as its key steps,
at the same time an effective method for ecological function zoning was formulated. The case studies of Dongfu suburban town
environmental planning and Xiamen eco-city conceptual planning indicate that scientifically sound results of ecological function
zoning can contribute to improving not only the adaptability and acceptability of environmental planning, also the environmental
management and the decision-making. The experience shows that the ecological function zoning methods should be applied according
to the principles of adaptive management, resource-based and community-based, so that it can integrate science into decision-making
process, avoiding both narrow-minded viewpoints of planners and natural resource use conflicts among variety of stakeholders.
Problems to be resolved in the future are also pointed out in the ending part. 相似文献
1000.
We tested the prediction that lactating fur seals (Arctocephalus gazella) at South Georgia will take prey of greater energy density with increasing distance of foraging from the colony. The study
investigated the differences in diet of fur seals foraging within two regions, one near the breeding colony and the other
at greater distance. Diet varied significantly in relation to foraging location. Dietary items of low quality were eaten in
both regions but more food items with a high-energy content appeared in the diet of seals travelling to distant oceanic waters.
We conclude that there is likely to be a trade-off between energy gain and distance travelled which enables female fur seals
to maintain a relatively constant rate of energy delivery to their offspring irrespective of the distance travelled to find
food. 相似文献