全文获取类型
收费全文 | 247篇 |
免费 | 2篇 |
国内免费 | 3篇 |
专业分类
安全科学 | 22篇 |
废物处理 | 8篇 |
环保管理 | 45篇 |
综合类 | 36篇 |
基础理论 | 54篇 |
污染及防治 | 49篇 |
评价与监测 | 11篇 |
社会与环境 | 22篇 |
灾害及防治 | 5篇 |
出版年
2024年 | 1篇 |
2022年 | 5篇 |
2021年 | 10篇 |
2020年 | 2篇 |
2019年 | 2篇 |
2018年 | 6篇 |
2017年 | 14篇 |
2016年 | 16篇 |
2015年 | 14篇 |
2014年 | 5篇 |
2013年 | 11篇 |
2012年 | 12篇 |
2011年 | 16篇 |
2010年 | 13篇 |
2009年 | 11篇 |
2008年 | 8篇 |
2007年 | 18篇 |
2006年 | 7篇 |
2005年 | 9篇 |
2004年 | 9篇 |
2003年 | 4篇 |
2002年 | 8篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1997年 | 4篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1976年 | 1篇 |
1964年 | 1篇 |
1959年 | 2篇 |
1951年 | 1篇 |
1950年 | 1篇 |
1948年 | 1篇 |
1946年 | 1篇 |
1940年 | 1篇 |
1936年 | 2篇 |
排序方式: 共有252条查询结果,搜索用时 265 毫秒
81.
In mark-recapture studies, various techniques can be used to uniquely identify individual animals, such as ringing, tagging
or photo-identification using natural markings. In some long-term studies more than one type of marking procedure may be implemented
during the study period. In these circumstances, ignoring the different mark types can produce biased survival estimates since
the assumption that the different mark types are equally catchable (homogeneous capture probability across mark types) may
be incorrect. We implement an integrated approach where we simultaneously analyse data obtained using three different marking
techniques, assuming that animals can be cross-classified across the different mark types. We discriminate between competing
models using the AIC statistic. This technique also allows us to estimate both relative mark-loss probabilities and relative
recapture efficiency rates for the different marking methods. We initially perform a simulation study to explore the different
biases that can be introduced if we assume a homogeneous recapture probability over mark type, before applying the method
to a real dataset. We make use of data obtained from an intensive long-term observational study of UK female grey seals (Halichoerus grypus) at a single breeding colony, where three different methods are used to identify individuals within a single study: branding,
tagging and photo-identification based on seal coat pattern or pelage. 相似文献
82.
Mordechai Shohat MD Edna Akstein Bella Davidov Gad Barkai Cyril Legum Miriam David Hanna Dar Yitzhak Romem Aliza Amiel Hana Cohen Gideon Bach Ziva Ben-Neriah Ruth N. Sheffer Zvi Appelman Juan Chemke Pnina Zadka Tamy Zer Boleslaw Goldman 《黑龙江环境通报》1995,15(10):967-970
We investigated the contribution of different screening criteria to the prenatal detection of Down syndrome (DS) as well as other chromosomal anomalies in the Jewish population in Israel during 1990 and 1992. There was a significant decrease (P<0·03) in the incidence of DS live-births during 1992 (40:78 442) compared with 1990 (69:73 751) which paralleled a marked increase in total prenatal testing and in DS cases detected prenatally. Private laboratories, which perform amniocenteses mostly for women with a low risk of DS and without genetic counselling, had a significantly lower detection rate (1:917) compared with that of the genetic institutes, which following genetic counselling test both women ≥ 37 years of age (1:91) and women younger than 37 years (1:113). The detection of chromosomal anomalies other than DS was less affected by the reason for amniocentesis. Amniocentesis indicated by maternal serum marker screening of women younger than 37 years identified a greater number of chromosomal anomalies other than DS than amniocentesis based on age (≥37 years) alone (111:9604 versus 94:9810; P<0·06). Prenatal detection of DS is most effective when the indication for amniocentesis follows genetic counselling. The increasing use of maternal serum marker screening leads to a significant improvement in the positive detection rate of chromosomal anomalies other than DS in young women. 相似文献
83.
Gene flow from crop fields to wild populations produces hybrids that often differ from their wild counterparts in growth form, phenology, and life history characteristics. Germination and dormancy dynamics have a strong influence on population persistence, competitive dynamics, and ultimately, plant fitness. They may also play a role in modifying crop gene introgression, which has been of primary interest since the release of transgenic crops. We investigated how seed germination and dormancy were affected by sunflower crop wild hybridization in both laboratory and field experiments. Hybridization increased seed germination and decreased dormancy. Of the nine wild populations we assayed, most of their hybrids had higher germination than the wilds of the same population. However, absolute germination levels varied by population and testing environment. Hybrids produced by three different crop lines differed in germination, and their germination rankings shifted across populations. Increased germination in hybrids could accelerate crop gene introgression, provided that hybrids germinate in an appropriate period. Differences in relative germination of wild and hybrid seed indicated that the effect of germination on introgression will likely vary by population due, in part, to initial levels of dormancy in the population. Therefore, the implications of gene flow from crops with novel characteristics or from transgenic crops will also vary by population. 相似文献
84.
85.
Ruth E. Bennett T. Scott Sillett Robert A. Rice Peter P. Marra 《Conservation biology》2022,36(1):e13779
To meet the growing demand for chocolate, cocoa (Theobroma cacao) agriculture is expanding and intensifying. Although this threatens tropical forests, cocoa sustainability initiatives largely overlook biodiversity conservation. To inform these initiatives, we analyzed how cocoa agriculture affects bird diversity at farm and landscape scales with a meta-analysis of 23 studies. We extracted 214 Hedges' g* comparisons of bird diversity and 14 comparisons of community similarity between a forest baseline and 4 farming systems that cover an intensification gradient in landscapes with high and low forest cover, and we summarized 119 correlations between cocoa farm features and bird diversity. Bird diversity declined sharply in low shade cocoa. Cocoa with >30% canopy cover from diverse trees retained bird diversity similar to nearby primary or mature secondary forest but held a different community of birds. Diversity of endemic species, frugivores, and insectivores (agriculture avoiders) declined, whereas diversity of habitat generalists, migrants, nectarivores, and granivores (agriculture associates) increased. As forest decreased on the landscape, the difference in bird community composition between forest and cocoa also decreased, indicating agriculture associates replaced agriculture avoiders in forest patches. Our results emphasize the need to conserve forested landscapes (land sparing) and invest in mixed-shade agroforestry (land sharing) because each strategy benefits a diverse and distinct biological community. 相似文献
86.
87.
Large-scale environmental research efforts are conducted under frameworks that provide a common basis for evaluating research
in many diverse fields. Such frameworks should be subjected to critical review to determine if they meet crucial expectations.
In the case of the US Global Change Research Program, we perceive that most research follows a framework that we define as
the predictive model framework. We believe this framework is insufficient for resolving the unprecedented predicaments posed
by global change. We recommend a complementary framework, the system response framework, which directs research toward useful
indicators of change rather than precise predictions. We further argue that, even if research is complementary and effective
under the two frameworks, conclusive results prior to decisions should not be expected. The burden of proof must itself be
a continuing topic of open discourse and inquiry. 相似文献
88.
Ruth M. Thompson Jordan Hall Chris Morrison Nicole R. Palmer David L. Roberts 《Conservation biology》2021,35(6):1747-1754
Internet-based research is increasingly important for conservation science and has wide-ranging applications and contexts, including culturomics, illegal wildlife trade, and citizen science. However, online research methods pose a range of ethical and legal challenges. Online data may be protected by copyright, database rights, or contract law. Privacy rights may also restrict the use and access of data, as well as ethical requirements from institutions. Online data have real-world meaning, and the ethical treatment of individuals and communities must not be marginalized when conducting internet-based research. As ethics frameworks originally developed for biomedical applications are inadequate for these methods, we propose that research activities involving the analysis of preexisting online data be treated analogous to offline social science methods, in particular, nondeceptive covert observation. By treating internet users and their data with respect and due consideration, conservationists can uphold the public trust needed to effectively address real-world issues. 相似文献
89.
Floods are the most common type of natural disaster in both developed and developing countries and have led to extensive morbidity and mortality throughout the world. Worldwide, over the past 30 years, flooding has claimed the lives of more than 200,000 people and affected more than 2.8 billion others. The impact of flooding on health varies among populations and depends primarily on vulnerability and the kind of event experienced. It severely disrupts livelihoods and has a significant impact on the health of pregnant women and children. In addition, it may exacerbate a range of negative psychological and physiological child and reproductive health outcomes. Awareness‐raising, education, and the issuing of warnings appear to be key initiatives to mitigate or prevent flood morbidity and mortality, especially among people living in low‐ and middle‐income countries. Agencies responding to emergencies also need to be more cognisant of the dangers, specifically those engaged in healthcare, nutrition, and water safety programmes. 相似文献
90.
According to current environmental legislation concerned with water scarcity, paper industry is being forced to adopt a zero liquid effluent policy. In consequence, reverse osmosis (RO) systems are being assessed as the final step of effluent treatment trains aiming to recover final wastewater and reuse it as process water. One of the most important drawbacks of these treatments is the production of a retentated stream, which is usually highly loaded with biorecalcitrant organic matter and inorganics; and this effluent must meet current legislation stringent constraints before being ultimately disposed. The treatment of biorefractory RO retentate from a paper mill by several promising advanced oxidation processes (AOPs) - conventional Fenton, photo-Fenton and photocatalysis - was optimized considering the effect and interaction of reaction parameters; particularly using response surface methodology (RSM) when appropriate (Fenton processes). The economical cost of these treatments was also comparatively assessed. Photo-Fenton process was able to totally remove the COD of the retentate, and resulted even operatively cheaper at high COD removal levels than conventional Fenton, which achieved an 80% reduction of the COD at best. In addition, although these optimal results were produced at pH=2.8, it was also tested that Fenton processes are able to achieve good COD reduction efficiencies (>60%) without adjusting the initial pH value, provided the natural pH of this wastewater was close to neutral. Finally, although TiO(2)-photocatalysis showed the least efficient and most expensive figures, it improved the biodegradability of the retentate, so its combination with a final biological step almost achieved the total removal of the COD. 相似文献