全文获取类型
收费全文 | 32819篇 |
免费 | 308篇 |
国内免费 | 246篇 |
专业分类
安全科学 | 810篇 |
废物处理 | 1272篇 |
环保管理 | 4023篇 |
综合类 | 6825篇 |
基础理论 | 8186篇 |
环境理论 | 17篇 |
污染及防治 | 8302篇 |
评价与监测 | 1983篇 |
社会与环境 | 1810篇 |
灾害及防治 | 145篇 |
出版年
2022年 | 231篇 |
2021年 | 255篇 |
2019年 | 258篇 |
2018年 | 463篇 |
2017年 | 451篇 |
2016年 | 687篇 |
2015年 | 520篇 |
2014年 | 738篇 |
2013年 | 2324篇 |
2012年 | 875篇 |
2011年 | 1314篇 |
2010年 | 1024篇 |
2009年 | 1086篇 |
2008年 | 1355篇 |
2007年 | 1405篇 |
2006年 | 1263篇 |
2005年 | 1026篇 |
2004年 | 1084篇 |
2003年 | 1016篇 |
2002年 | 981篇 |
2001年 | 1243篇 |
2000年 | 817篇 |
1999年 | 554篇 |
1998年 | 415篇 |
1997年 | 420篇 |
1996年 | 453篇 |
1995年 | 481篇 |
1994年 | 488篇 |
1993年 | 424篇 |
1992年 | 430篇 |
1991年 | 418篇 |
1990年 | 434篇 |
1989年 | 397篇 |
1988年 | 342篇 |
1987年 | 319篇 |
1986年 | 302篇 |
1985年 | 315篇 |
1984年 | 342篇 |
1983年 | 344篇 |
1982年 | 351篇 |
1981年 | 314篇 |
1980年 | 257篇 |
1979年 | 268篇 |
1978年 | 257篇 |
1977年 | 230篇 |
1976年 | 197篇 |
1975年 | 213篇 |
1974年 | 226篇 |
1973年 | 208篇 |
1972年 | 219篇 |
排序方式: 共有10000条查询结果,搜索用时 671 毫秒
51.
The amounts of total NH
4
+
detected in the external media in which Phascolosoma arcuatum had been exposed to various periods of anoxia were significantly greater than those in which the worms were exposed to normoxia for a similar period. The increased NH
4
+
production by P. arcuatum during anoxic exposure was unlikely to be due to an increased catabolism of adenine nucleotides or urea. In contrast, there were significant decreases in the concentrations of several free amino acids in the coelomic plasma and body tissues of individuals during the 48 h of anoxic exposure. The amount of NH
4
+
produced by the anoxic P. arcuatum could be accounted for by the decreases in the concentrations of aspartate or glycine. Increases in the catabolism of free amino acids (FAA), leading to the increased production of NH
4
+
, in P. arcuatum during anoxia were supported by the detection of significant changes in the kinetic properties of glutamate dehydrogenase (GDH), in the deaminating direction, from worms exposed to anoxia for 48 h. The apparent increase in the affinity of GDH from the anoxic worm to glutamate would bring about a greater deaminating activity at physiological concentrations of ths substrate. P. arcuatum used in these experiments were collected from the mangrove swamp at Mandai, Singapore between 1990 and 1993. 相似文献
52.
53.
54.
55.
G. D. Kataev 《Russian Journal of Ecology》2005,36(6):421-426
The effect of industrial air pollution on natural small mammal populations has been studied in the northern taiga subzone of the boreal forest zone. The results of long-term monitoring have been used to demonstrate the possibility of predicting changes in the main population and community characteristics of the animal species studied as dependent on the degree of anthropogenic impact. 相似文献
56.
M Mora R Skiles B McKinney M Paredes D Buckler D Papoulias D Klein 《Environmental pollution (Barking, Essex : 1987)》2002,116(1):169-176
Peregrine falcons (Falco peregrinus) have been recorded nesting in Big Bend National Park, Texas, USA and other areas of the Chihuahuan Desert since the early 1900s. From 1993 to 1996, peregrine falcon productivity rates were very low and coincided with periods of low rainfall. However, low productivity also was suspected to be caused by environmental contaminants. To evaluate potential impacts of contaminants on peregrine falcon populations, likely avian and bat prey species were collected during 1994 and 1997 breeding seasons in selected regions of western Texas, primarily in Big Bend National Park. Tissues of three peregrine falcons found injured or dead and feathers of one live fledgling also were analyzed. Overall, mean concentrations of DDE [1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene], a metabolite of DDT [1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane], were low in all prey species except for northern rough-winged swallows (Stelgidopteryx serripennis, mean = 5.1 microg/g ww). Concentrations of mercury and selenium were elevated in some species, up to 2.5 microg/g dw, and 15 microg/g dw, respectively, which upon consumption could seriously affect reproduction of top predators. DDE levels near 5 microg/g ww were detected in carcass of one peregrine falcon found dead but the cause of death was unknown. Mercury, selenium, and DDE to some extent, may be contributing to low reproductive rates of peregrine falcons in the Big Bend region. 相似文献
57.
58.
59.
This work, carried out within the framework of the PRISMA II project, aims at evaluating the effects of the Po River flow on primary productivity, measured by C with in situ sample incubations. A total of four cruises was carried out in late winter and early summer (1996-1998) along transects from the coast offshore. In both seasons, the highest primary productivity was found in the most oligohaline stations. The effects of the Po River inputs were therefore clearly evident in the westernmost area, both in high productivity values and in the shape of productivity profiles. In late winter, extensive blooms of Skeletonema costatum and Pseudo-nitzschia delicatissima resulted in productivity values that were sometimes higher than in early summer. In early summer 1996, greatly reduced river flow clearly influenced productivity which was much lower than in 1997. 相似文献
60.