全文获取类型
收费全文 | 40357篇 |
免费 | 404篇 |
国内免费 | 370篇 |
专业分类
安全科学 | 1281篇 |
废物处理 | 1877篇 |
环保管理 | 5113篇 |
综合类 | 7000篇 |
基础理论 | 10248篇 |
环境理论 | 13篇 |
污染及防治 | 9918篇 |
评价与监测 | 2891篇 |
社会与环境 | 2547篇 |
灾害及防治 | 243篇 |
出版年
2022年 | 364篇 |
2021年 | 391篇 |
2020年 | 248篇 |
2019年 | 318篇 |
2018年 | 568篇 |
2017年 | 609篇 |
2016年 | 936篇 |
2015年 | 699篇 |
2014年 | 1121篇 |
2013年 | 3221篇 |
2012年 | 1355篇 |
2011年 | 1769篇 |
2010年 | 1435篇 |
2009年 | 1521篇 |
2008年 | 1794篇 |
2007年 | 1736篇 |
2006年 | 1571篇 |
2005年 | 1412篇 |
2004年 | 1352篇 |
2003年 | 1320篇 |
2002年 | 1236篇 |
2001年 | 1513篇 |
2000年 | 1026篇 |
1999年 | 671篇 |
1998年 | 467篇 |
1997年 | 509篇 |
1996年 | 530篇 |
1995年 | 595篇 |
1994年 | 533篇 |
1993年 | 444篇 |
1992年 | 493篇 |
1991年 | 479篇 |
1990年 | 456篇 |
1989年 | 430篇 |
1988年 | 413篇 |
1987年 | 319篇 |
1986年 | 335篇 |
1985年 | 353篇 |
1984年 | 360篇 |
1983年 | 344篇 |
1982年 | 362篇 |
1981年 | 320篇 |
1980年 | 238篇 |
1979年 | 269篇 |
1978年 | 248篇 |
1977年 | 203篇 |
1975年 | 204篇 |
1974年 | 218篇 |
1973年 | 237篇 |
1972年 | 214篇 |
排序方式: 共有10000条查询结果,搜索用时 468 毫秒
21.
22.
23.
24.
25.
26.
The periodicity of fires in larch forests of Evenkia and their relationship with landscape elements have been studied. Cross-sections with “burns” in them caused by past fires have been analyzed in 72 test plots; the fire chronology encompassed the period from the 15th to the 20th century. The between-fire intervals (BFIs) have been calculated by two methods: (I) on the basis of burns alone and (II) on the basis of burns and the start of growth of the new generation of larch after the earliest fire. The BFI depends on local orographic features; it is 86 ± 11 (105 ± 12), 61 ± 8 (73 ± 8), 139 ± 17 (138 ± 18), and 68 ± 14 (70 ± 13) years for northeastern slopes, southwestern slopes, bogs, and flatlands, respectively. The mean BFIs calculated by methods I and II are 82 ± 7 and 95 ± 7 years, respectively. The permafrost horizon rises at a mean rate of 0.3 cm per year after a forest fire. It has been shown that the number of fires regularly peaks at periods of 36 and 82 years. There is also a temporal trend in fire frequency: the mean BFI was approximately 100 years in the 19th century and 65 years in the 20th century. 相似文献
27.
28.
29.
Molecular phylogeny and population structure of tideland snails in the genus Cerithidea around Japan
Phylogenetic relationships and genetic population structures were analyzed for tideland gastropods in the genus Cerithidea around Japan on the basis of partial sequence of the mitochondrial COI gene. Large genetic divergence was shown between individuals of Cerithidea cingulata in the southern Ryukyus and those in the central Ryukyus and the Japanese Islands. Haplotypes of C. cingulata from the Japanese Islands were paraphyletic with the exclusion of a monophyletic group from the central Ryukyus. Genetic differentiation of C. cingulata was also detected between Amami-Oshima Island and Okinawajima Island. No genetic divergence was found between Cerithidea rhizophorarum in the Japanese Islands and its subspecies C. rhizophorarum morchii in the Ryukyu Islands. The lack of genetic divergence of Cerithidea largillierti between continental China and Japan suggests relatively recent migration between the Japanese Islands and the Asian continent. For all three Cerithidea species distributed in both the Japanese Islands and the Ryukyu Islands, the Tokara Gap and the Kerama Gap were shown to have acted as barriers to the dispersal. 相似文献
30.