全文获取类型
收费全文 | 7915篇 |
免费 | 401篇 |
国内免费 | 1870篇 |
专业分类
安全科学 | 558篇 |
废物处理 | 339篇 |
环保管理 | 700篇 |
综合类 | 3711篇 |
基础理论 | 1917篇 |
污染及防治 | 1774篇 |
评价与监测 | 486篇 |
社会与环境 | 484篇 |
灾害及防治 | 217篇 |
出版年
2024年 | 34篇 |
2023年 | 99篇 |
2022年 | 290篇 |
2021年 | 280篇 |
2020年 | 305篇 |
2019年 | 210篇 |
2018年 | 362篇 |
2017年 | 389篇 |
2016年 | 444篇 |
2015年 | 389篇 |
2014年 | 374篇 |
2013年 | 517篇 |
2012年 | 848篇 |
2011年 | 680篇 |
2010年 | 389篇 |
2009年 | 375篇 |
2008年 | 390篇 |
2007年 | 421篇 |
2006年 | 316篇 |
2005年 | 600篇 |
2004年 | 696篇 |
2003年 | 602篇 |
2002年 | 231篇 |
2001年 | 199篇 |
2000年 | 170篇 |
1999年 | 121篇 |
1998年 | 75篇 |
1997年 | 94篇 |
1996年 | 54篇 |
1995年 | 49篇 |
1994年 | 47篇 |
1993年 | 32篇 |
1992年 | 30篇 |
1991年 | 17篇 |
1990年 | 17篇 |
1989年 | 11篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1981年 | 1篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1966年 | 2篇 |
1961年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
A. Kr?ner A. P. Willner E. Hegner A. Frischbutter J. Hofmann R. Bergner 《Geologische Rundschau》1995,84(3):437-456
Single zircons from two orthogneiss complexes, the Grey Gneiss and Red Gneiss, the lowermost tectonic units in the Erzgebirge, were dated. The grey Freiberg Gneiss is of igneous origin and has a 207Pb/206Pb emplacement age of 550±7 Ma. A quartz monzonite from Lauenstein contains idiomorphic zircons with a mean 207Pb/206Pb age of 555±7 Ma as well as xenocrysts ranging in age between 850 and 1910 Ma. Red gneisses from the central Erzgebirge contain complex zircon populations, including numerous xenocrysts up to 2464 Ma in age. The youngest, idiomorphic, zircons in all samples yielded uniform 207Pb/206Pb ages between 550±9 and 554±10 Ma. Nd isotopic data support the interpretation of crustal anatexis for the origin of both units. Nd(t) values for the grey gneisses are –7.5 and –6.0 respectively, (mean crustal residence ages of 1.7–1.8 Ga). The red gneisses have a wider range in Nd(t) values from –7.7 to –2.8 (T
DM ages of 1.4–1.8 Ga). The zircon ages document a distinct late Proterozoic phase of granitoid magmatism, similar in age to granitoids in the Lusatian block farther north-east. However, Palaeozoic deformation as well as medium pressure metamorphism ( 8 kbar/600–650° C) are identical in both gneiss units and distinguish these rocks from the Lusatian granitoids. The grey and red gneisses were overthrust by units with abundant high-pressure relicts and a contrasting P-T evolution. Zircon xenocryst and Nd model ages in the range 1000–1700 Ma are similar to those in granitoid rocks of Lusatia and the West-Sudetes, and document a pre-Cadomian basement in parts of east-central Europe that, chronologically, has similarities with the Sveconorwegian domain in the Baltic Shield. 相似文献
92.
Michael H?der 《Die Naturwissenschaften》1989,76(7):340
Naturwissenschaften Aktuell
Großforschung mit anderen Namen 相似文献93.
The larvae and pupae of the ladybird Thalassa saginata develop inside colonies of the dolichoderine ant Dolichoderus bidens. This association is the first specific and obligatory relationship recorded between ants and ladybirds. The ants provide shelter and protection to the larvae but the diet of the latter remains unclear. The integration of T. saginata larvae into the ant colonies is achieved by mimicking the cuticular patterns of the ants brood. Moreover, the larvae secrete substances from their hairs and anal gland that are likely to enhance their attractiveness. 相似文献
94.
Carbon sequestration in the global carbon cycle is almost always attributed to organic carbon storage alone, while soil mineral carbon is generally neglected. However, due to the longer residence time of mineral carbon in soils (102–106 years), if stored in large quantities it represents a potentially more efficient sink. The aim of this study is to estimate the mineral carbon accumulation due to the tropical iroko tree (Milicia excelsa) in Ivory Coast. The iroko tree has the ability to accumulate mineral carbon as calcium carbonate (CaCO3) in ferralitic soils, where CaCO3 is not expected to precipitate. An estimate of this accumulation was made by titrating carbonate from two characteristic soil profiles in the iroko environment and by identifying calcium (Ca) sources. The system is considered as a net carbon sink because carbonate accumulation involves only atmospheric CO2 and Ca from Ca-carbonate-free sources. Around one ton of mineral carbon was found in and around an 80-year-old iroko stump, proving the existence of a mineral carbon sink related to the iroko ecosystem. Conservation of iroko trees and the many other biomineralizing plant species is crucial to the maintenance of this mineral carbon sink. 相似文献
95.
96.
97.
98.
产学研结合是高职教育改革发展的必由之路。本文从通信专业的发展现状着手,详述了通信专业在校企合作方面所做的努力和取得的成果,并探讨了校企合作今后需努力的方向。 相似文献
99.
IntroductionBothmethomylandthiodicarbareNmethylcarbmatepesticides.Methomyliseffectiveonawiderangeofinsectsasanovicide,larvicid... 相似文献
100.
水环境中痕量有机有害物质的监测 总被引:3,自引:0,他引:3
论述了水中有机有害物质的监测,实质上是一项复杂系统的痕量分析课题。重点评述了痕量富集、色谱分离与监测、综合分析的主要进展。 相似文献