全文获取类型
收费全文 | 27713篇 |
免费 | 256篇 |
国内免费 | 203篇 |
专业分类
安全科学 | 708篇 |
废物处理 | 927篇 |
环保管理 | 3628篇 |
综合类 | 7595篇 |
基础理论 | 6186篇 |
环境理论 | 8篇 |
污染及防治 | 6759篇 |
评价与监测 | 1340篇 |
社会与环境 | 897篇 |
灾害及防治 | 124篇 |
出版年
2018年 | 305篇 |
2017年 | 296篇 |
2016年 | 437篇 |
2015年 | 335篇 |
2014年 | 480篇 |
2013年 | 1976篇 |
2012年 | 627篇 |
2011年 | 897篇 |
2010年 | 741篇 |
2009年 | 874篇 |
2008年 | 937篇 |
2007年 | 994篇 |
2006年 | 888篇 |
2005年 | 740篇 |
2004年 | 776篇 |
2003年 | 777篇 |
2002年 | 699篇 |
2001年 | 974篇 |
2000年 | 669篇 |
1999年 | 456篇 |
1998年 | 334篇 |
1997年 | 307篇 |
1996年 | 352篇 |
1995年 | 376篇 |
1994年 | 402篇 |
1993年 | 358篇 |
1992年 | 377篇 |
1991年 | 367篇 |
1990年 | 404篇 |
1989年 | 396篇 |
1988年 | 319篇 |
1987年 | 317篇 |
1986年 | 294篇 |
1985年 | 307篇 |
1984年 | 314篇 |
1983年 | 309篇 |
1982年 | 320篇 |
1981年 | 336篇 |
1980年 | 286篇 |
1979年 | 294篇 |
1978年 | 255篇 |
1977年 | 230篇 |
1976年 | 247篇 |
1974年 | 260篇 |
1973年 | 238篇 |
1972年 | 229篇 |
1971年 | 217篇 |
1968年 | 229篇 |
1967年 | 260篇 |
1966年 | 222篇 |
排序方式: 共有10000条查询结果,搜索用时 33 毫秒
91.
92.
93.
94.
95.
96.
97.
In vitro studies of the submerged angiospermRuppia maritima: Auxin and cytokinin effects on plant growth and development 总被引:1,自引:0,他引:1
Axenic tissue cultures ofRuppia maritima L. were established and propagated clonally in vitro from terminal rhizome segments collected from Tampa Bay, Florida, USA. Cultures were maintained in a base medium consisting of synthetic seawater supplemented with half-strength Murashige and Skoog salts and 1% sucrose at pH 5.6. The effects of five cytokins [6-furfurylaminopurine (kinetin), 6-benzylaminopurine (BAP), 2-isopentyladenine (2iP), 6-(4-hydroxy-3-methyl-but-2-enylamino) purine (zeatin), andn-phenyl-n-1,2,3-thidiazol-5yl urea (thidiazuron)] and one auxin [napthalene acetic acid (NAA)] on explant growth and development were investigated. Cytokinin additions resulted in a 3- to 4-fold increase in nodal production, branching, and biomass ofR. maritima after 12 wk in culture. Cultures responded in a dose-dependent manner to 2iP but exhibited broad dose-response curves to kinetin, BAP, zeatin, and thidiazuron. NAA addition resulted in increased leaf and internodal lengths, but reduced the number of leaves per node and the rhizome biomass. The addition of NAA almost completely suppressed root growth in media without cytokinins and had an antagonistic effect on nodal production and branching in cytokinin-supplemented media. 相似文献
98.
99.
Monitoring of airborne dust in Delhi during May to July 1985 revealed residues of DDT varying from 1.3 to 7.14 ng mg(-1) (4.06-22.31 ng m(-2) day(-1)) with an average of 3.32 ng mg(-1) (10.38 ng m(-2) day(-1)), and HCH which ranged from 0.46 to 2.35 ng mg(-1) (1.44-7.34 ng m(-2) day(-1)) with a mean of 1.16 ng mg(-1) (3.63 ng m(-2) day(-1)). The concentration of total DDT was almost 3 times greater than that of HCH. 相似文献
100.
The relative tissue accumulation of Pb, Cd and Zn were compared in two populations each of two species of slugs (Arion subfuscus and Deroceras reticulatum). One population was resident at a contaminated Pb/Zn mine site, and the other population was from an uncontaminated site and was transferred for 20 days to microcosms established at the mine site. It was found that when the experiment was conducted during late spring (May), but not in late winter (February), that the Pb and Zn concentrations in the tissues of the 'transplants', were significantly higher than in the tissues of 'residents'; the Cd concentrations in the transplants, although significantly higher in the May sample than in February, did not exceed those of their 'resident' counterparts. It was postulated that: (a) Pb and Zn tolerance in slugs is phenotypically expressed by a reduction in metal accumulation; (b) Cd tolerance, if present, may be characterized by enhanced storage capacity; and (c) the presence of local metal-tolerant ecotypes is a biotic variable that may confound the relationship between dry tissue and environmental metal concentrations that forms a basis of pollution biomonitoring. 相似文献