全文获取类型
收费全文 | 4150篇 |
免费 | 36篇 |
国内免费 | 15篇 |
专业分类
安全科学 | 45篇 |
废物处理 | 272篇 |
环保管理 | 255篇 |
综合类 | 658篇 |
基础理论 | 858篇 |
环境理论 | 4篇 |
污染及防治 | 1464篇 |
评价与监测 | 380篇 |
社会与环境 | 256篇 |
灾害及防治 | 9篇 |
出版年
2023年 | 45篇 |
2022年 | 127篇 |
2021年 | 124篇 |
2020年 | 46篇 |
2019年 | 54篇 |
2018年 | 154篇 |
2017年 | 112篇 |
2016年 | 209篇 |
2015年 | 115篇 |
2014年 | 234篇 |
2013年 | 396篇 |
2012年 | 255篇 |
2011年 | 253篇 |
2010年 | 196篇 |
2009年 | 142篇 |
2008年 | 236篇 |
2007年 | 240篇 |
2006年 | 217篇 |
2005年 | 148篇 |
2004年 | 127篇 |
2003年 | 111篇 |
2002年 | 100篇 |
2001年 | 60篇 |
2000年 | 45篇 |
1999年 | 38篇 |
1998年 | 15篇 |
1997年 | 14篇 |
1996年 | 8篇 |
1995年 | 24篇 |
1994年 | 16篇 |
1993年 | 13篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 11篇 |
1989年 | 9篇 |
1970年 | 6篇 |
1967年 | 7篇 |
1966年 | 11篇 |
1965年 | 15篇 |
1964年 | 28篇 |
1963年 | 12篇 |
1962年 | 17篇 |
1961年 | 11篇 |
1960年 | 9篇 |
1959年 | 26篇 |
1958年 | 25篇 |
1957年 | 17篇 |
1956年 | 13篇 |
1955年 | 18篇 |
1954年 | 7篇 |
排序方式: 共有4201条查询结果,搜索用时 265 毫秒
981.
In Portuguese waters, thornback ray Raja clavata spawns mainly between May and January, although females and males in spawning condition are found throughout the year. The
maturation process can be divided into three main phases by using information on gonad weight, oviducal gland and uterus width
in females and on gonad weight, clasper length and sperm duct width in males. Females attain length-at-first-maturity at 784 mm
and males at 676 mm, at ages of 7.5 and 5.8 years, respectively. In females larger than length-at-first-maturity, a resting
stage was identified characterized by low gonadosomatic index and well-developed oviducal glands and uteri. These results
along with the low proportion of adult females that are effectively reproducing per month demonstrated that the thornback
ray cannot be considered a continuous spawner as described in other studies. Fecundity was determinate with about 35 eggs
released per batch. During the spawning season, a total of four batch episodes occur indicating that the total fecundity was
approximately 136 eggs per female. Regional differences may exist in the reproductive strategy of the species, namely on the
duration of the spawning season, length-at-first-maturity, and fecundity, which can be related to a more intense fishing pressure
in northern European waters. 相似文献
982.
Seán Lyons Liam Murphy Richard S.J. Tol 《Atmospheric environment (Oxford, England : 1994)》2010,44(32):3901-3906
There are no observations for methane emissions from landfill waste in Ireland. Methane emissions are imputed from waste data. There are intermittent data on waste sent to landfill. We compare two alternative ways to impute the missing waste “data” and evaluate the impact on methane emissions. We estimate Irish historical landfill quantities from 1960–2008 and Irish methane emissions from 1968–2006. A model is constructed in which waste generation is a function of income, price of waste disposal and, household economies of scale. A transformation ratio of waste to methane is also included in the methane emissions model. Our results contrast significantly with the Irish Environmental Protection Agency’s (EPA) figures due to the differences in the underlying assumptions. The EPA’s waste generation and methane emission figures are larger than our estimates from the early 1990s onwards. Projections of the distance to target show that the EPA overestimates the required policy effort. 相似文献
983.
Environmental Chemistry Letters - Steroids are abundant in living organisms and are responsible for various biological functions. They are good candidates for inclusion complexes formation with... 相似文献
984.
Maria João Cruz Elisabeth Maria Rogier Robert Tiago Costa David Avelar Rui Rebelo Mário Pulquério 《Regional Environmental Change》2016,16(5):1293-1304
Assessing biodiversity vulnerability to future climate change is essential for developing robust adaptation strategies. A number of vulnerability assessment methodologies have been developed, from bioclimatic envelop models to more complex approaches that also consider biological traits and population status. However, the lack of comparative studies leaves the user to choose among the different methodologies without much guidance. This study applied three vulnerability assessment approaches to the Portuguese herpetofauna: (I) impact assessment approach based on bioclimatic models; (II) integrated vulnerability assessment approach, adding the evaluation of adaptive capacity to approach I; and (III) integrated vulnerability assessment and validation based on expert consultation. Results showed disagreement between the different approaches for 19 % of the species studied. Most differences were found between approach III and the two other approaches. All approaches showed advantages and limitations, the choice of a methodology being ultimately dependent on the study goals. Approach I has proven efficient to capture general vulnerability patterns. Approach II, although presenting results similar to approach I, allows for the identification of key factors affecting the species adaptive capacity and may be useful in tailoring adaptation measures. Approach III further allows us to identify knowledge gaps and to evaluate vulnerability when data availability or quality is reduced. Further, because this approach is based on an expert workshop, it has proven a perfect means to build on the vulnerability assessment results to identify indicator species and prioritize specific adaptation options. 相似文献
985.
986.
González-Marín Rosa María Moreno-Casasola Patricia Castro-Luna Alejandro Antonio Castillo Alicia 《Regional Environmental Change》2017,17(5):1343-1354
Regional Environmental Change - Wetlands play important roles that benefit social-ecological systems. They are threatened by climate change and human activities, i.e., raising livestock and... 相似文献
987.
Isabel Díaz-Reviriego Álvaro Fernández-Llamazares Matthieu Salpeteur Patricia L. Howard Victoria Reyes-García 《Ambio》2016,45(3):263-275
Local medical systems are key elements of social-ecological systems as they provide culturally appropriate and locally accessible health care options, especially for populations with scarce access to biomedicine. The adaptive capacity of local medical systems generally rests on two pillars: species diversity and a robust local knowledge system, both threatened by local and global environmental change. We first present a conceptual framework to guide the assessment of knowledge diversity and redundancy in local medicinal knowledge systems through a gender lens. Then, we apply this conceptual framework to our research on the local medicinal plant knowledge of the Tsimane’ Amerindians. Our results suggest that Tsimane’ medicinal plant knowledge is gendered and that the frequency of reported ailments and the redundancy of knowledge used to treat them are positively associated. We discuss the implications of knowledge diversity and redundancy for local knowledge systems’ adaptive capacity, resilience, and health sovereignty. 相似文献
988.
Gladbach A Gladbach DJ Kempenaers B Quillfeldt P 《Behavioral ecology and sociobiology》2010,64(11):1779-1789
Although studies on the evolution and function of female ornaments have become more numerous in the last years, the majority
of these studies were carried out in cases where female ornaments were a smaller and duller version of the ornaments found
in males. There are substantially fewer studies on species with female-specific ornaments. However, no study so far investigated
the potential of female-specific colouration as a quality signal in birds with conventional sex roles. We studied female-specific
ornamentation in a strongly sexually dichromatic species, the upland goose Chloephaga picta leucoptera, in two consecutive years. Male upland geese have white head and breast feathers and black legs, whereas females have reddish-brown
head and breast feathers and conspicuous yellow-orange legs. We found that female-specific colouration in upland geese can
reliably indicate different aspects of female phenotypic quality. Females with more orange coloured legs and more red-like
head colours had higher clutch and egg volumes than females with a paler leg and head colouration, and a more reddish plumage
colouration was related to a higher body condition. These relationships provide the theoretic possibility for males to assess
female phenotypic quality on the basis of colouration. Furthermore, the females with a more orange-like tarsus colouration
had higher plasma carotenoid levels. Both tarsus colouration and carotenoid concentrations of individual females were highly
correlated across years, indicating that tarsus colour is a stable signal. Despite this correlation, small individual differences
in plasma carotenoid concentrations between the two study years were related to differences in tarsus colouration. We thus
show for the first time in a wild bird and under natural conditions that carotenoid-based integument colouration remains consistent
between individuals in consecutive years and is also a dynamic trait reflecting individual changes in carotenoid levels. In
this species, where pairs form life-long bonds, the honesty of the carotenoid-based integument colouration suggests that it
may be a sexually selected female ornament that has evolved through male mate choice. 相似文献
989.
As some species of game and free‐living animals promptly respond to ecosystem damage by a reaction that is easy to interpret, they are important ecological indicators in assessing the total contamination of the environment. Consumers of the highest order like predators, predatory and fish‐eating birds are among the most important bioindicators of environmental contamination by chlorinated hydrocarbons and PCB. Data on chlorinated hydrocarbons and PCB levels were collected throughout 1988–1992 and obtained from 16 species of free‐living animals from 9 protected areas of Slovakia. Muscle tissue, liver, kidney and egg samples were examined for HCB, HCH isomers, DDT and its analogues, and PCB. Levels of organic chlorinated contaminants reveal a decreasing tendency and thus cease to be a toxicologically important risk factor in game, with the exception of predatory birds, as significant values have been recorded in their eggs and reproductive organs. 相似文献
990.
Dorottya Kiss Gergely Hegyi János Török Balázs Rosivall 《Behavioral ecology and sociobiology》2013,67(2):185-192
In altricial birds, parental feeding is essential, and its amount may depend on the quality of both parents. A relationship between parental quality and feeding rate is generally attributed to an active adjustment by parents in order to retain good quality mates or ensure high fitness through raising high-quality offspring. However, the behaviour and need of young may also change with parental quality, and this may affect parental behaviour. A further problem is that most studies have investigated post-hatching parental investment in relation to the secondary sexual signals of males, but not females. In a cross-fostering experiment, we examined the feeding rates of rearing parents in relation to the size and ornamentation of both original and rearing parents in collared flycatchers (Ficedula albicollis). Using this setup, we could examine whether the observed feeding patterns were the results of the decision of the parents based on their own and their partner’s traits or the constraints imposed by the behaviour or need of offspring. When correcting for clutch size and year, we found that feeding rate of both foster parents correlated with the wing patch size of the original female. This implies that original maternal quality had an offspring-mediated indirect effect on investment of foster parents, that is intrinsic nestling quality may constrain parental feeding decisions. This explanation should not be overlooked in future studies on preferential parental investment, and our results also point out that maternal ornaments deserve more attention in such studies. 相似文献