全文获取类型
收费全文 | 7872篇 |
免费 | 59篇 |
国内免费 | 40篇 |
专业分类
安全科学 | 174篇 |
废物处理 | 336篇 |
环保管理 | 683篇 |
综合类 | 1110篇 |
基础理论 | 1622篇 |
环境理论 | 6篇 |
污染及防治 | 2082篇 |
评价与监测 | 666篇 |
社会与环境 | 1260篇 |
灾害及防治 | 32篇 |
出版年
2023年 | 34篇 |
2022年 | 101篇 |
2021年 | 121篇 |
2020年 | 55篇 |
2019年 | 79篇 |
2018年 | 134篇 |
2017年 | 165篇 |
2016年 | 221篇 |
2015年 | 159篇 |
2014年 | 301篇 |
2013年 | 682篇 |
2012年 | 340篇 |
2011年 | 374篇 |
2010年 | 293篇 |
2009年 | 329篇 |
2008年 | 395篇 |
2007年 | 417篇 |
2006年 | 354篇 |
2005年 | 313篇 |
2004年 | 290篇 |
2003年 | 262篇 |
2002年 | 261篇 |
2001年 | 271篇 |
2000年 | 207篇 |
1999年 | 101篇 |
1998年 | 74篇 |
1997年 | 81篇 |
1996年 | 69篇 |
1995年 | 91篇 |
1994年 | 75篇 |
1993年 | 62篇 |
1992年 | 59篇 |
1991年 | 62篇 |
1990年 | 75篇 |
1989年 | 56篇 |
1988年 | 42篇 |
1987年 | 38篇 |
1986年 | 48篇 |
1985年 | 46篇 |
1984年 | 51篇 |
1983年 | 38篇 |
1982年 | 48篇 |
1981年 | 37篇 |
1980年 | 44篇 |
1979年 | 44篇 |
1977年 | 32篇 |
1975年 | 31篇 |
1973年 | 34篇 |
1972年 | 39篇 |
1969年 | 31篇 |
排序方式: 共有7971条查询结果,搜索用时 171 毫秒
911.
MarÍA JOSÉ Ruiz‐López Natalia Gañan José Antonio Godoy Ana Del Olmo Julian Garde Gerardo Espeso Astrid Vargas Fernando Martinez Eduardo R. S. Roldán Montserrat Gomendio 《Conservation biology》2012,26(6):1121-1129
The relation among inbreeding, heterozygosity, and fitness has been studied primarily among outbred populations, and little is known about these phenomena in endangered populations. Most researchers conclude that the relation between coefficient of inbreeding estimated from pedigrees and fitness traits (inbreeding‐fitness correlations) better reflects inbreeding depression than the relation between marker heterozygosity and fitness traits (heterozygosity‐fitness correlations). However, it has been suggested recently that heterozygosity‐fitness correlations should only be expected when inbreeding generates extensive identity disequilibrium (correlations in heterozygosity and homozygosity across loci throughout the genome). We tested this hypothesis in Mohor gazelle (Gazella dama mhorr) and Iberian lynx (Lynx pardinus). For Mohor gazelle, we calculated the inbreeding coefficient and measured heterozygosity at 17 microsatellite loci. For Iberian lynx, we measured heterozygosity at 36 microsatellite loci. In both species we estimated semen quality, a phenotypic trait directly related to fitness that is controlled by many loci and is affected by inbreeding depression. Both species showed evidence of extensive identity disequilibrium, and in both species heterozygosity was associated with semen quality. In the Iberian lynx the low proportion of normal sperm associated with low levels of heterozygosity was so extreme that it is likely to limit the fertility of males. In Mohor gazelle, although heterozygosity was associated with semen quality, inbreeding coefficient was not. This result suggests that when coefficient of inbreeding is calculated on the basis of a genealogy that begins after a long history of inbreeding, the coefficient of inbreeding fails to capture previous demographic information because it is a poor estimator of accumulated individual inbreeding. We conclude that among highly endangered species with extensive identity disequilibrium, examination of heterozygosity‐fitness correlations may be an effective way to detect inbreeding depression, whereas inbreeding‐fitness correlations may be poor indicators of inbreeding depression if the pedigree does not accurately reflect the history of inbreeding. Correlaciones Heterocigosidad‐ Adaptabilidad y Depresión Endogámica en Dos Especies de Mamíferos Críticamente en Peligro 相似文献
912.
A. V. Trapeznikov P. I. Yushkov V. N. Nikolkin V. N. Trapeznikova M. Ya. Chebotina V. P. Guseva 《Russian Journal of Ecology》2007,38(1):27-33
Radioecological conditions have been estimated in Lake Chervyanoe located on the central axis of the Eastern Ural Radioactive Trace (EURT) about 100–110 km northeast of the Mayak Production Association. Data on the 90Sr and 137Cs contents in the main components of the lake, the distribution of these radionuclides over the profile of bottom sediments, and their amounts in the lake are presented. The experimental data have been used to construct mathematical models for estimating changes in the radionuclide concentrations and amounts in the water and bottom sediments of the lake over a long period after the nuclear accident, as well as the tritium content of the lake water in different periods of time. 相似文献
913.
Abstract: A drastic decline in the number of black rhinoceroses ( Diceros bicornis ), primarily as a result of poaching places this species in imminent danger of extinction. The remaining black rhinos are divided into small, isolated populations that are vulnerable to demographic extinction, disease epidemics, genetic drift and inbreeding. Some conservationists have suggested minimizing these threats by moving as many animals as possible from different isolated populations to a few safe "rhino sanctuaries." To examine the possible long-term genetic consequences of such a strategy, we focused our efforts on determining the level of genetic differences among the remaining black rhino populations by examining restriction fragment length polymorphisms of the rapidly evolving mitochondrial DNA molecule. The 23 black rhinos in our survey, including animals from three geographic regions and two named subspecies, showed very little mitochondrial DNA differentiation. Only 4 out of 18 restriction enzymes revealed any mtDNA polymorphism, and the average estimated percent sequence divergence between the four mtDNA genotypes observed as 0.17%. Mitochondrial DNA divergence between the two named subspecies, D. b. minor and D. b. michaeli , was estimated to be only 0.29%. These results indicate a very close genetic relationship among the black rhinos in our survey. Thus, the mitochondrial DNA data suggest that within national boundaries, the black rhino populations we sampled may be considered single populations for breeding purposes, which might increase the species' probability of survival. 相似文献
914.
G. Langhendries D. E. De Vos B. F. Sels I. Vankelecom P. A. Jacobs G. V. Baron 《Clean Products and Processes》1998,1(1):21-29
Liquid phase hydrocarbon oxidation is one of the principal routes towards industrial organic chemicals. However, low product
selectivity and associated by-product formation are major problems in several oxidation processes. As a result of the increasingly
stringent environmental regulations, the development of oxidation catalysts has been a major challenge in the last decade.
An overview of novel selective and clean oxidation catalysts and processes is presented.
Received: 27 July 1998 / Accepted: 8 September 1998 相似文献
915.
Yu. N. Litvinov S. A. Abramov V. Yu. Kovaleva A. V. Krivopalov E. A. Novikov A. I. Chechulin 《Russian Journal of Ecology》2007,38(6):413-418
The structural-temporal organization of a murine rodent community in the taiga has been studied near Lake Teletskoe, Mountain Altai. The results show that the long-term dynamics of indices characterizing community diversity depend mainly on changes in the structure of dominance rather than on the population dynamics of species. The distribution of species in the factor space corresponds to their preference for certain biotopes, from dry to relatively moist. An analysis of relationships within the rodent community has revealed the synchronous dynamics of species abundance and antiphase pattern of changes in the structural indices of dominant species. 相似文献
916.
917.
Chemical pollution: Transfer of chemical elements to the aboverground phytomass of herbaceous plants
Changes in the species composition and a decrease in species diversity and total plant biomass along the gradient of soil pollution with heavy metals have been shown. Data on the concentrations of chemical elements (Zn, Cu, Cd, Pb, Co, Ni, Mn, Cr, and Fe) in the aboveground organs of herbaceous plants and the biomass of each species make it possible to estimate the role of higher producers in the incorporation of chemical elements into biogenic cycles in background zones and under conditions of chemical pollution. Plants of the composite family (Asteraceae) play the main role in accumulation of chemical elements. The results obtained indicate that natural ecosystems have mechanisms limiting excessive accumulation of chemical elements into the aboveground plant biomass. 相似文献
918.
919.
Otávio José de Oliveira José Roberto Serra Manoel Henrique Salgado 《Journal of Cleaner Production》2010,18(18):1797-1806
As a result of increasing global awareness about the importance of the environment, depletion of natural resources and legal pressures for companies to manage their processes in a sustainable manner, ISO 14001 systems have been gaining increasingly more importance in the organizational scenario. These elements are even more critical in emerging nations due to less awareness and fewer demands by governments and the population in relation to environmental issues. Therefore, the main objective of this study is to verify the benefits and difficulties of Environmental Management Systems based on ISO 14001 at industries in the state of São Paulo – Brazil (an emerging country) by conducting a survey to subsidize the proposal for actions in the public, academic and private sectors to promote the use of this standard of reference and strengthen its results in Brazil. A questionnaire was sent to 194 companies from the National Institute of Metrology, Standardization and Industrial Quality database. 69 answered, representing a return rate of 35.36%. The main benefits identified are related to the development of preventive environmental actions, reduction in the consumption of power, water, gas and fuel oil, and a positive influence on other internal management processes. The main difficulties are related to cost increases from ISO 14001 management systems and the constant changes in environmental legislation in Brazil. Some actions are proposed at the end of the analyses to intensify the use and improve the results of this standard, such as changes in government legislation and its collective development and implementation in industries. 相似文献
920.