全文获取类型
收费全文 | 5869篇 |
免费 | 290篇 |
国内免费 | 27篇 |
专业分类
测绘学 | 193篇 |
大气科学 | 400篇 |
地球物理 | 2187篇 |
地质学 | 1993篇 |
海洋学 | 253篇 |
天文学 | 924篇 |
综合类 | 32篇 |
自然地理 | 204篇 |
出版年
2022年 | 44篇 |
2021年 | 111篇 |
2020年 | 111篇 |
2019年 | 86篇 |
2018年 | 263篇 |
2017年 | 240篇 |
2016年 | 359篇 |
2015年 | 263篇 |
2014年 | 285篇 |
2013年 | 366篇 |
2012年 | 319篇 |
2011年 | 268篇 |
2010年 | 258篇 |
2009年 | 283篇 |
2008年 | 216篇 |
2007年 | 166篇 |
2006年 | 164篇 |
2005年 | 138篇 |
2004年 | 124篇 |
2003年 | 140篇 |
2002年 | 100篇 |
2001年 | 100篇 |
2000年 | 101篇 |
1999年 | 61篇 |
1998年 | 90篇 |
1997年 | 72篇 |
1996年 | 44篇 |
1995年 | 71篇 |
1994年 | 84篇 |
1993年 | 48篇 |
1992年 | 48篇 |
1991年 | 44篇 |
1990年 | 59篇 |
1989年 | 43篇 |
1988年 | 41篇 |
1987年 | 36篇 |
1986年 | 43篇 |
1985年 | 45篇 |
1984年 | 37篇 |
1983年 | 45篇 |
1982年 | 50篇 |
1981年 | 43篇 |
1980年 | 43篇 |
1979年 | 40篇 |
1978年 | 50篇 |
1977年 | 41篇 |
1975年 | 40篇 |
1974年 | 31篇 |
1973年 | 43篇 |
1971年 | 40篇 |
排序方式: 共有6186条查询结果,搜索用时 392 毫秒
991.
Dominique Girard Sabrina Clemente Kilian Toledo-Guedes Alberto Brito José Carlos Hernández 《Marine Ecology》2012,33(3):377-385
An outbreak of bald sea urchin disease was detected affecting intertidal populations of the edible temperate species Paracentrotus lividus at its southernmost geographical limit. The mortality event was detected in three sites (Güímar, Palmar and Alcalá) off Tenerife, Canary Islands (Northeastern Atlantic), in October 2003, coinciding with the highest sea surface temperatures (SST) and the lowest wave heights of the year. The prevalence of infection reached 100% but did not affect equally all studied sites or the different size classes. The disease was more prevalent in large sea urchins (>40 mm). The prevalence appeared to be positively correlated with the environmental variable SST and negatively correlated with wave height. In October 2004, only two infected urchins were found (prevalence 1%) at one of the studied sites. However, during 2004 no such extreme values of temperature and wave height were observed. We conclude that high SSTs and low wave heights such as those observed during 2003 are conditions that may trigger outbreaks of urchin disease. 相似文献
992.
José De La Cruz-Agüero Francisco Javier García-Rodríguez Víctor Manuel Cota-Gómez Felipe Neri Melo-Barrera Rogelio González-Armas 《Ocean Science Journal》2012,47(2):147-153
Fresh and preserved (type material) specimens of the black ghost chimaera Hydrolagus melanophasma were compared for morphometric characteristics. A molecular comparison was also performed on two mitochondrial gene sequences (12S rRNA and 16S rRNA gene sequences). While significant differences in measurements were found, the differences were not attributable to sexual dimorphism or the quality of the specimens, but to the sample size and the type of statistical tests. The result of the genetic characterization showed that 12S rRNA and 16S rRNA genes represented robust molecular markers that characterized the species. 相似文献
993.
Valentí Rull José A. López-Sáez Teresa Vegas-Vilarrúbia 《Journal of Paleolimnology》2008,40(1):399-411
This paper evaluates the potential usefulness of non-pollen palynomorphs or NPPs (microfossils other than pollen and spores
present in palynological preparations) contained in lake sediments in the paleolimnological reconstruction of high altitude
environments (>4,000 m) from the Venezuelan Andes. A synthetic, quantitative approach is employed, instead of the classical
analytical and mostly qualitative approach commonly used so far for NPPs. The main sources of variation are the Pediastrum–Botryococcus alternation and the relationship between these two algae and animal remains such as Acari legs, postabdomina of Cladocera,
mandibles of other invertebrates, and an unknown type called LVA-1. Other significant microfossils are remains of Rivularia-type and turbellarian oocytes, including Gyratrix. The sequence initiates around 15,000 calibrated years before present (cal BP) with the deglaciation of the lake catchment,
high water levels and still cold climates. A phase of lower lake levels was recorded between about 12,000 and 6,000 cal BP.
Temperatures increased by around 9,000 and 7,000 cal BP, and then decreased until 6,000 cal BP. Since that time, both lake
levels and temperature increased again and stabilized at about 4,000 cal BP, when they reach modern-like values. These results
show a good agreement with previous studies based on pollen, diatom and oxygen isotope analyses, and provide additional paleoecological
information, as for example the possibility of a previously unrecorded Younger Dryas signal. The inclusion of quantitative
NPP analysis in routine paleolimnological studies using synthetic methods is thus recommended. Possible future improvements
are suggested, mainly those related with the development and use of NPP modern analogs. 相似文献
994.
995.
Moment tensor decompositions revisited 总被引:3,自引:0,他引:3
Václav Vavryčuk 《Journal of Seismology》2015,19(1):231-252
996.
997.
998.
999.
1000.