全文获取类型
收费全文 | 21014篇 |
免费 | 285篇 |
国内免费 | 552篇 |
专业分类
安全科学 | 551篇 |
废物处理 | 933篇 |
环保管理 | 2252篇 |
综合类 | 3890篇 |
基础理论 | 5631篇 |
环境理论 | 5篇 |
污染及防治 | 5374篇 |
评价与监测 | 1460篇 |
社会与环境 | 1613篇 |
灾害及防治 | 142篇 |
出版年
2023年 | 135篇 |
2022年 | 272篇 |
2021年 | 217篇 |
2020年 | 214篇 |
2019年 | 218篇 |
2018年 | 336篇 |
2017年 | 383篇 |
2016年 | 472篇 |
2015年 | 400篇 |
2014年 | 661篇 |
2013年 | 1639篇 |
2012年 | 714篇 |
2011年 | 992篇 |
2010年 | 887篇 |
2009年 | 817篇 |
2008年 | 948篇 |
2007年 | 945篇 |
2006年 | 824篇 |
2005年 | 709篇 |
2004年 | 688篇 |
2003年 | 699篇 |
2002年 | 643篇 |
2001年 | 859篇 |
2000年 | 609篇 |
1999年 | 346篇 |
1998年 | 209篇 |
1997年 | 256篇 |
1996年 | 249篇 |
1995年 | 287篇 |
1994年 | 288篇 |
1993年 | 232篇 |
1992年 | 251篇 |
1991年 | 228篇 |
1990年 | 260篇 |
1989年 | 234篇 |
1988年 | 199篇 |
1987年 | 212篇 |
1986年 | 195篇 |
1985年 | 193篇 |
1984年 | 188篇 |
1983年 | 180篇 |
1982年 | 167篇 |
1981年 | 140篇 |
1980年 | 143篇 |
1979年 | 150篇 |
1978年 | 127篇 |
1977年 | 136篇 |
1974年 | 113篇 |
1973年 | 125篇 |
1972年 | 110篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
P Joseph S Viswanatha M K Krishnakumari 《Journal of environmental science and health. Part. B》1992,27(3):269-280
The haematotoxicity of technical hexachlorocyclohexane (HCH) (1000 ppm) was investigated in male albino rats fed with diet free of vitamin A or containing vitamin A at 2000 or 10(5) I.U./kg. Assessment of HCH-induced haematotoxicity at the end of the 7 weeks feeding period was done on the basis of haemoglobin content, total count of red blood cells and white blood cells and the differential counts of the white blood cells as well as by parameters such as packed cell volume, mean corpuscular volume, mean corpuscular haemoglobin, mean corpuscular haemoglobin content, prothrombin time and clotting time. In the rats fed with vitamin A-free diet containing HCH, significant reductions were noticed in the total white blood cells count, clotting time and prothrombin time indicating severe haematotoxicity. Differential count of the white blood cells of these rats revealed a non-significant reduction in the lymphocyte count. The only indication of haematotoxicity caused by hexachlorocyclohexane in the vitamin A supplemented rats was a slight but statistically significant reduction of the total count of white blood cells. These results demonstrate that the haematotoxicity of hexachlorocyclohexane in the rats is enhanced by vitamin A-deficiency and its supplementation particularly in excess but not at hypervitaminotic level is protective against the toxicity. 相似文献
22.
As part of a programme to characterize floating anthropogenic debris in the aquatic environment, the US Environmental Protection Agency (EPA) conducted 18 field surveys in the harbours of major metropolitan cities of the east, west, and Gulf coasts of the United States and the Mid-Atlantic Bight. the surveys were designed to provide information on the types, relative amounts, and distributions of aquatic debris in different geographic regions of the United States. Neuston nets (0.33 mm mesh) were used to collect surface debris during outgoing tides on two or three consecutive days in selected areas of each city. After each net tow, the debris, which ranged in size from small resin pellets to large plastic sheeting pieces, was identified, categorized, and counted. the data are being used to qualitatively characterize aquatic debris in coastal metropolitan areas, to examine potential regional variations, and to tentatively identify potential sources. 相似文献
23.
24.
Daytime sampling of mangrove and seagrass (Halophila/Halodule community) habitats every 7 wk at Alligator Creek, Queensland, Australia, over a period of 13 mo (February 1985–February
1986) using two types of seine net, revealed distinct mangrove and seagrass fish and crustacean faunas. Total abundance of
fish and relative abundance of small and large fish also varied between habitats and seasonally. Post-larval, juvenile and
small adult fish captured with a small seine-net (3 mm mesh) were significantly more abundant (4 to 10 times) in the mangrove
habitat throughout the 13 mo of sampling. Mangrove fish abundance showed significant seasonality, greatest catches being recorded
in the warm, wet-season months of the year. Relative abundances of larger fish (captured in a seine net with 18 mm mesh) in
the two habitats varied throughout the year, but did not show a seasonal pattern. At the same site, small crustaceans were
significantly more abundant in the mangroves in all but one dryseason sample. Similar comparisons for three riverine sites,
sampled less frequently, in the dry and wet seasons of 1985 and 1986, respectively, showed that in general mangrove habitats
had significantly more fish per sample, although the relative abundance of fish in mangroves and other habitats changed with
season. Crustacean catches showed a similar pattern, except that densities among sites changed with season. Fish and crustacean
abundance in mangroves varied among sites, indicating that estuaries differ in their nursery-ground value. The juveniles of
two commercially important penaeid prawn species (Penaeus merguiensis and Metapenaeus ensis) were amongst the top three species of crustaceans captured in the study, and both were significantly more abundant in the
mangrove habitat. By contrast, mangroves could not be considered an important nursery for juveniles of commercially important
fish species in northern Australia. However, based on comparisons of fish catches in other regions, the results of the present
study indicate the importance of mangroves as nursery sites for commercially exploited fish stocks elsewhere in South-East
Asia.
Contribution No. 378 from the Australian Institute of Marine Science 相似文献
25.
A significant positive correlation between the lipid content of eight fish species and their bioconcentration factor (BCF) of 1,2,4-trichlorobenzene is demonstrated. The log BCF value on a lipid basis is in good agreement with the log n-octanol/water partition coefficient. 相似文献
26.
Data on the existence of a specific system regulating the growth, size, and structure of enterobacterial populations are first summarized in terms of the chemical ecology concept formulated by S.S. Shvarts. The role of this system in transgene functioning is described using the example of the lux operon integrated into Escherichia coli. A relatively simple test for estimating such interactions is proposed.Translated from Ekologiya, No. 2, 2005, pp. 91–96.Original Russian Text Copyright © 2005 by Pshenichnov, Maslennikova, Nikitina. 相似文献
27.
28.
29.
30.
Four introduced and one aboriginal species of the genus Pinus L. have been studied in the middle taiga subzone of southern Karelia. Significant interspecific differences in the dates of onset, cessation, and peak of the growth of shoots and needles have been revealed. It has been shown that their annual increment depends on the rate of growth, rather than on its duration. The dynamics of shoot and needle growth in introduced and aboriginal species, though largely similar, differ in some respects. These differences reflect species-specific responses to hydrothermal conditions in a certain growing season. 相似文献