全文获取类型
收费全文 | 25999篇 |
免费 | 286篇 |
国内免费 | 216篇 |
专业分类
安全科学 | 751篇 |
废物处理 | 969篇 |
环保管理 | 3609篇 |
综合类 | 4832篇 |
基础理论 | 6673篇 |
环境理论 | 17篇 |
污染及防治 | 6404篇 |
评价与监测 | 1598篇 |
社会与环境 | 1453篇 |
灾害及防治 | 195篇 |
出版年
2022年 | 215篇 |
2021年 | 214篇 |
2020年 | 170篇 |
2019年 | 216篇 |
2018年 | 341篇 |
2017年 | 366篇 |
2016年 | 517篇 |
2015年 | 443篇 |
2014年 | 601篇 |
2013年 | 2099篇 |
2012年 | 782篇 |
2011年 | 1056篇 |
2010年 | 860篇 |
2009年 | 990篇 |
2008年 | 1086篇 |
2007年 | 1093篇 |
2006年 | 1000篇 |
2005年 | 853篇 |
2004年 | 780篇 |
2003年 | 809篇 |
2002年 | 743篇 |
2001年 | 951篇 |
2000年 | 709篇 |
1999年 | 426篇 |
1998年 | 303篇 |
1997年 | 320篇 |
1996年 | 348篇 |
1995年 | 376篇 |
1994年 | 371篇 |
1993年 | 347篇 |
1992年 | 326篇 |
1991年 | 349篇 |
1990年 | 335篇 |
1989年 | 308篇 |
1988年 | 256篇 |
1987年 | 225篇 |
1986年 | 254篇 |
1985年 | 237篇 |
1984年 | 249篇 |
1983年 | 259篇 |
1982年 | 258篇 |
1981年 | 250篇 |
1980年 | 230篇 |
1979年 | 241篇 |
1978年 | 167篇 |
1977年 | 182篇 |
1975年 | 136篇 |
1974年 | 160篇 |
1973年 | 152篇 |
1972年 | 159篇 |
排序方式: 共有10000条查询结果,搜索用时 656 毫秒
441.
R.H. Field S. Benke K. Bdonyi R.B. Bradbury 《Agriculture, ecosystems & environment》2007,120(2-4):399-404
Bird use of conservation tillage-established (CT—seedbed preparation without soil inversion) crops was assessed at two adjacent sites in western Hungary, in comparison with conventionally established (mouldboard ploughed—P) fields. Bird abundance was assessed in a typical rotation of spring-sown maize and winter wheat in three consecutive winters. In the first winter, several species and the guild of seed-eating passerines were significantly more abundant on CT established plots, in both crop types. In the second winter, only starlings were more abundant on CT plots. In the third winter, only skylarks favoured CT over P plots. In combination with agri-environment scheme measures designed to provide resources for biodiversity, conservation tillage could play a role in softening the impact of agriculture on farmland birds in Hungary and elsewhere in Eastern Europe, in addition to its potential for reducing soil erosion and diffuse pollution. 相似文献
442.
重金属在牡蛎(Crassostrea virginica)中的生物积累及其影响因素的研究 总被引:11,自引:0,他引:11
牡蛎软体,贝壳和沉积物中Cd、Cr、Cu、Fe、Mn、Pb和Zn等重金属元素被同步分析研究,研究结果表明,重金属在牡蛎中的生物积累是牡自身的新陈代谢、重金属元素的地球化学性质和环境诸因素综合影响的结果,其中牡蛎斩生理作用对重金属在软体中的积累产生的影响尤为重要,而贝壳中重金属的积累对来自环境的影响更为敏感。 相似文献
443.
444.
445.
446.
447.
Stratigraphy, lithology and depositional structures of Liassic red limestone-breccias of the Adnet Formation, including the 'Adnet Scheck', were studied at several outcrops of the Northern Calcareous Alps (NCA) south-east of Salzburg. A four-fold lithostratigraphic division is proposed for the Adnet Formation of the Osterhorn Mountains: the hemipelagic Schmiedwirt (Sinemurian) and Kehlbach (Carixian) members are separated from the pelagic Saubach Member (Toarcian) by a layer of amalgamated breccias (Scheck Member, probably Domerian to early Toarcian). Several other breccia beds occur locally from the base of the Kehlbach Member up to the lower Saubach Member. Although the sediments overlying the Scheck Member breccias are of coeval age, the ages of the underlying strata are very different. This can be explained by submarine Liassic erosion during a period of resedimentation from the middle Carixian until the early Toarcian. At least 10–15?m of partly lithified sediments were eroded by gravity flows. The entire Kehlbach Member and up to two-thirds of the Schmiedwirt Member were removed at Adnet. The breccias originated from submarine debris flows. Repeated flows over a long period and the depositional setting exclude a triggering by sea-level fluctuations. Most probably they arose from tectonically triggered slumps and slides of superficial sediments. The 'Scheck' was initiated on the steep upper slope of the drowned Triassic Adnet reef and flowed to the north-east.The Pliensbachian to early Toarcian period of tectonic activity indicated by the breccias was the most important during the Liassic in the Osterhorn Mountains and other parts of the NCA. From the large-scale regional distribution of the breccias and in accord with published data, a roughly north-east trending strike-slip fault zone is proposed, crossing the NCA south of the Osterhorn block, with a peaking activity during the Pliensbachian to early Toarcian as the cause of the tectonic movements. 相似文献
448.
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
449.
Arachnoid cysts are an uncommon central nervous system malformation, representing only 1 per cent of all intracranial masses. We report the second-trimester prenatal diagnosis of a posterior fossa arachnoid cyst, associated with an unbalanced X;9 translocation. 相似文献
450.