全文获取类型
收费全文 | 42563篇 |
免费 | 4656篇 |
国内免费 | 26696篇 |
专业分类
安全科学 | 1918篇 |
废物处理 | 1689篇 |
环保管理 | 5253篇 |
综合类 | 33208篇 |
基础理论 | 11062篇 |
环境理论 | 9篇 |
污染及防治 | 14402篇 |
评价与监测 | 3809篇 |
社会与环境 | 2090篇 |
灾害及防治 | 475篇 |
出版年
2023年 | 172篇 |
2022年 | 311篇 |
2021年 | 343篇 |
2020年 | 811篇 |
2019年 | 2143篇 |
2018年 | 2528篇 |
2017年 | 2500篇 |
2016年 | 2557篇 |
2015年 | 2800篇 |
2014年 | 3742篇 |
2013年 | 5875篇 |
2012年 | 3969篇 |
2011年 | 3801篇 |
2010年 | 3394篇 |
2009年 | 3429篇 |
2008年 | 3288篇 |
2007年 | 3431篇 |
2006年 | 2710篇 |
2005年 | 2164篇 |
2004年 | 2066篇 |
2003年 | 1839篇 |
2002年 | 1665篇 |
2001年 | 2007篇 |
2000年 | 1663篇 |
1999年 | 1181篇 |
1998年 | 898篇 |
1997年 | 843篇 |
1996年 | 949篇 |
1995年 | 879篇 |
1994年 | 712篇 |
1993年 | 615篇 |
1992年 | 653篇 |
1991年 | 623篇 |
1990年 | 607篇 |
1989年 | 565篇 |
1988年 | 489篇 |
1987年 | 365篇 |
1986年 | 321篇 |
1985年 | 323篇 |
1984年 | 376篇 |
1983年 | 346篇 |
1982年 | 375篇 |
1981年 | 314篇 |
1980年 | 242篇 |
1979年 | 290篇 |
1978年 | 220篇 |
1977年 | 192篇 |
1976年 | 179篇 |
1975年 | 172篇 |
1972年 | 170篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
681.
环境表现对金融利害攸关者的价值 总被引:1,自引:0,他引:1
Evan C.Henry 《生态毒理学报》2000,22(1):11-12
公司财务表现与环境表现之间的联系日益明显.各公司可以通过促进后者而力求获得资助优势.公司环境表现对金融利害攸关者的价值随资助类型而异,同样也随环境改善的程度和具体细节而异.争取资助的公司,以及政府和非政府组织,应当熟悉不同的金融服务业及其具体需要和问题. 相似文献
682.
683.
684.
685.
686.
The reproductive strategies of two gammaridean amphipod species, Gammarus wilkitzkii and Apherusa glacialis, that permanently inhabit the Arctic sea ice were investigated. G. wilkitzkii reaches sexual maturity at an age of 2 years and produces 128 ± 54 eggs fem.−1 yr−1. Mating takes place during fall and winter, and the development of the large eggs (0.60 to 0.80 mm diam.) lasts 6 to 7 months.
The sex ratio of G. wilkitzkii was dominated by males in a proportion of 1.5:1. In vivo studies showed that juveniles are released in batches from the brood
pouches of the females during April and May. A. glacialis reaches sexual maturity at the age of 1 year and produces 555 ± 151 eggs fem.−1 yr−1. The eggs are between 0.18 and 0.23 mm in diameter, and are the smallest known for gammaridean amphipods. Eggs are kept in
packages of two to eight in the brood pouches of females. The sex ratio of A. glacialis was dominated by females in a proportion of 3:1. The high fecundity of both amphipod species, the release of juveniles in
batches over a period of time, a high proportion of females (A. glacialis), and an elongated life-span with multiple spawnings (G. wilkitzkii) are discussed as possible adaptations to the specific and highly variable conditions under Arctic sea ice.
Received: 29 December 1999 / Accepted: 8 March 2000 相似文献
687.
Strontium (Sr) and calcium (Ca) contents in the otoliths of yellow and silver European eels [Anguilla anguilla (L.)] collected from coastal waters of the Baltic Sea and a freshwater lake in Sweden were examined by wavelength dispersive
X-ray spectrometry with an electron microprobe. The mean Sr/Ca ratios from elver check to otolith edge were significantly
higher for the eels from coastal waters (5.39 ± 1.09‰) than for those from the lake (0.71 ± 0.89‰). The evidence indicates
that European eels in the Baltic Sea do not necessarily migrate into freshwater streams during the growth phase.
Received: 30 September 1999 / Accepted: 6 April 2000 相似文献
688.
F. Maltagliati A. P. Peru M. Casu F. Rossi C. Lardicci M. Curini-Galletti A. Castelli 《Marine Biology》2000,136(5):871-879
The genetic relationships between morphologically indistinguishable marine and brackish populations of Syllis gracilis Grube, 1840 (Polychaeta: Syllidae) were studied by means of allozyme electrophoresis. Samples of S. gracilis from marine coastal and brackish-water habitats were examined for variation at 13 presumptive loci. In addition, a sample
of the closely related species S. prolifera (Krohn, 1852) was analysed. Five loci were multiallelic in at least one population of S. gracilis and eight loci in S. prolifera. Low to moderate levels of within-population genetic variability were found, with average expected heterozygosity values
ranging from H = 0.068 (±0.043 SE) to 0.187 (±0.069 SE) in the populations of S. gracilis; higher values were found in S. prolifera (H = 0.325 ± 0.076). The presence of various private alleles indicated a marked genetic divergence among populations of S. gracilis, with Nei's genetic distances ranging from D = 0.000 to 0.833 and a highly significant F
ST value. Furthermore, evidence for strong genetic heterogeneity between two sympatric marine populations was found. UPGMA cluster
analysis and multidimensional scaling pointed out a clear genetic divergence between brackish and marine populations. At least
two genetically divergent entities occurred in marine and brackish habitats. This could be due to local adaptation of individuals
coming from marine populations to brackish habitats, but more presumably to the occurrence of a species complex within S. gracilis.
Received: 6 June 1999 / Accepted: 7 February 2000 相似文献
689.
C. T. Achuthankutty Y. Shrivastava G. G. Mahambre S. C. Goswami M. Madhupratap 《Marine Biology》2000,137(1):19-22
Effect of salinity on the feeding rate and parthenogenetic reproduction of asexual females of the cladoceran Diaphanosoma celebensis Stingelin was studied. Short-term (10 h) grazing experiments were conducted using Isochrysis galbana as feed at 5, 17, 25 and 30 psu salinity. Gut pigment concentration showed a significantly higher rate of feeding at lower
salinities. Survival, growth, maturity attainment and neonate production of asexual females reared in the above four test
salinities indicated preference for lower salinities (5 and 17 psu). The mean size of adult females decreased from 909 to
593 μm, mean life span from 24 to 5 d, mean neonate production from 12 to 2 and mean size of neonates from 434 to 400 μm as
the salinity increased from 5 to 30 psu. Salinity variations also affected the size and age of primiparous females. Resting
egg formation and sexual reproduction did not occur at the tested salinities. The results indicate that D. celebensis is adapted to low saline, estuarine environments.
Received: 14 January 2000 / Accepted: 24 March 2000 相似文献
690.
The Chilean intertidal Lottiidae limpet fauna consists of at least nine species, grouped into the monophyletic taxon Scurria and a single taxon preliminarily designated as `Lottia' orbignyi (Dall). Within the Scurria clade, the most basal species are Scurria variabilis (Sowerby), S. viridula (Lamarck), and S.zebrina (Lesson), and among the most crown groups are S. ceciliana (Orbigny) and S. araucana (Orbigny). This phylogenetic information, obtained by the analysis of molecular characters (16S mtDNA), provides a framework
for a comparative study of behavioral characters. In this study, we analyze the escape responses of two basal limpet species
(`L.' orbignyi and S. viridula) and two derived limpet species (S. araucana and S. ceciliana) in the presence of the limpet predatory seastar Heliaster helianthus (Lamarck) and the limpet non-predatory seastars Stichaster striatus Muller and Troschel and Patiria chilensis Lutken. Neither P.chilensis nor Stichaster striatus induced escape responses such as those observed with the predatory H. helianthus. Moreover, in the presence of H. helianthus, basal and derived limpet species differed significantly in the percentage of individuals responding, reaction time, and
duration of the response. The basal species `L.' orbignyi and Scurriaviridula exhibited instantaneous and vigorous locomotor responses, whereas the derived species S. araucana and S. ceciliana displayed no locomotor responses. The same pattern was found in responses to H. helianthus homogenates. The results strongly suggest a correlation between phylogeny and anti-predator escape responses to the seastar
H. helianthus. Alternative escape responses have evolved for basal and derived species within the Chilean clade.
Received: 27 April 2000 / Accepted: 16 August 2000 相似文献