全文获取类型
收费全文 | 1628篇 |
免费 | 65篇 |
国内免费 | 29篇 |
专业分类
测绘学 | 39篇 |
大气科学 | 176篇 |
地球物理 | 364篇 |
地质学 | 601篇 |
海洋学 | 132篇 |
天文学 | 248篇 |
综合类 | 4篇 |
自然地理 | 158篇 |
出版年
2023年 | 5篇 |
2022年 | 10篇 |
2021年 | 31篇 |
2020年 | 33篇 |
2019年 | 21篇 |
2018年 | 49篇 |
2017年 | 40篇 |
2016年 | 74篇 |
2015年 | 45篇 |
2014年 | 65篇 |
2013年 | 109篇 |
2012年 | 55篇 |
2011年 | 99篇 |
2010年 | 83篇 |
2009年 | 92篇 |
2008年 | 90篇 |
2007年 | 93篇 |
2006年 | 93篇 |
2005年 | 61篇 |
2004年 | 63篇 |
2003年 | 47篇 |
2002年 | 47篇 |
2001年 | 40篇 |
2000年 | 31篇 |
1999年 | 36篇 |
1998年 | 23篇 |
1997年 | 19篇 |
1996年 | 19篇 |
1995年 | 16篇 |
1994年 | 12篇 |
1993年 | 16篇 |
1992年 | 7篇 |
1991年 | 17篇 |
1990年 | 15篇 |
1989年 | 15篇 |
1987年 | 13篇 |
1986年 | 17篇 |
1985年 | 8篇 |
1984年 | 5篇 |
1983年 | 14篇 |
1982年 | 12篇 |
1981年 | 14篇 |
1980年 | 12篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1975年 | 4篇 |
1974年 | 7篇 |
1973年 | 5篇 |
排序方式: 共有1722条查询结果,搜索用时 0 毫秒
261.
262.
Eric Robinson 《Geology Today》2003,19(6):219-222
263.
Jerry Edelstein Stuart Bowyer Eric J. Korpela Michael Lampton JoaquÍn Trapero José F. Gómez Carmen Morales Veronica Orozco 《Astrophysics and Space Science》2001,276(1):177-185
The hot interstellar medium (ISM) has far-reaching effect upon thestructure of galaxies. Although ISM heating processes are fairly wellunderstood, after decades of study, the processes that cool the hotinterstellar medium remain obscure. The EURD spectrograph was designed tomeasure the diffuse cosmic background from 350 to 1100 Å in order tostudy the hot ISM and the mechanisms by which it sheds its energy. Wepresent the first analysis of EURD observations of the cosmic background.These EURD observations have proven to be far more sensitive than previouswork; compared to previous results, we have improved the limits to theintensity of 450 to 900 Å line emission from the ISM by one to twoorders of magnitude. Our limit to OVI 1032 Å / 1038 Å doublet of 7900ph s-1 cm-2 str-1 is the lowest yet reported. The EURDlimits to line emission are less intense than predicted by a varietytheoretical models of the local ISM. 相似文献
264.
265.
266.
267.
Eric J. Bakker 《Astrophysics and Space Science》1997,251(1-2):73-80
In this paper we discuss the relevance, and possible scientific gains, which can be acquired from studying circumstellar molecular spectra toward evolved stars. Where can we expect circumstellar molecular spectra, why would we want to study these spectra, which molecules might be present, and what can we learn from these studies? We present an overview of reported detections, and discuss some of the results. 相似文献
268.
269.
Jemma Davidson Alexander N. Krot Kazuhide Nagashima Eric Hellebrand Dante S. Lauretta 《Meteoritics & planetary science》2014,49(8):1456-1474
We report in situ O isotope and chemical compositions of magnetite and olivine in chondrules of the carbonaceous chondrites Watson‐002 (anomalous CK3) and Asuka (A)‐881595 (ungrouped C3). Magnetite in Watson‐002 occurs as inclusion‐free subhedral grains and rounded inclusion‐bearing porous grains replacing Fe,Ni‐metal. In A‐881595, magnetite is almost entirely inclusion‐free and coexists with Ni‐rich sulfide and less abundant Ni‐poor metal. Oxygen isotope compositions of chondrule olivine in both meteorites plot along carbonaceous chondrite anhydrous mineral (CCAM) line with a slope of approximately 1 and show a range of Δ17O values (from approximately ?3 to ?6‰). One chondrule from each sample was found to contain O isotopically heterogeneous olivine, probably relict grains. Oxygen isotope compositions of magnetite in A‐881595 plot along a mass‐dependent fractionation line with a slope of 0.5 and show a range of Δ17O values from ?2.4‰ to ?1.1‰. Oxygen isotope compositions of magnetite in Watson‐002 cluster near the CCAM line and a Δ17O value of ?4.0‰ to ?2.9‰. These observations indicate that magnetite and chondrule olivine are in O isotope disequilibrium, and, therefore, not cogenetic. We infer that magnetite in CK chondrites formed by the oxidation of pre‐existing metal grains by an aqueous fluid during parent body alteration, in agreement with previous studies. The differences in Δ17O values of magnetite between Watson‐002 and A‐881595 can be attributed to their different thermal histories: the former experienced a higher degree of thermal metamorphism that led to the O isotope exchange between magnetite and adjacent silicates. 相似文献
270.