全文获取类型
收费全文 | 377篇 |
免费 | 21篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 50篇 |
地球物理 | 88篇 |
地质学 | 131篇 |
海洋学 | 32篇 |
天文学 | 42篇 |
综合类 | 1篇 |
自然地理 | 51篇 |
出版年
2022年 | 2篇 |
2021年 | 4篇 |
2020年 | 9篇 |
2019年 | 9篇 |
2018年 | 16篇 |
2017年 | 14篇 |
2016年 | 14篇 |
2015年 | 10篇 |
2014年 | 15篇 |
2013年 | 35篇 |
2012年 | 19篇 |
2011年 | 27篇 |
2010年 | 26篇 |
2009年 | 33篇 |
2008年 | 29篇 |
2007年 | 25篇 |
2006年 | 18篇 |
2005年 | 8篇 |
2004年 | 4篇 |
2003年 | 12篇 |
2002年 | 7篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
排序方式: 共有399条查询结果,搜索用时 15 毫秒
81.
82.
83.
Eric N. Powell Julie D. Gauthier Elizabeth A. Wilson Alanna Nelson Roger R. Fay James M. Brooks 《Marine Ecology》1992,13(3):243-270
84.
Ichthyoplankton distribution and abundance in the Celtic Sea 总被引:1,自引:1,他引:1
85.
William J. Sydeman Michelle M. Hester Julie A. Thayer Franklin Gress Paige Martin Joelle Buffa 《Progress in Oceanography》2001,49(1-4)
We studied the effects of low-frequency climate change on the reproductive performance of 11 species of marine bird in the southern California Current system, 1969–1997. Reproductive performance of Brown Pelican (Pelecanus occidentalis) and Double-crested Cormorant (Phalacrocrax auritus) in southern California demonstrated an increase in the 1970s and early 1980s, attributable to recovery from organochlorine contamination (primarily DDE). Brandt's Cormorant (Phalacrocorax penicillatus) in central California was the only species to demonstrate a secular increase in performance through time, a pattern that remains unexplained. Ashy Storm-petrel (Oceanodroma homochroa) and Pelagic Cormorant (Phalacrocorax pelagicus) demonstrated curvilinear patterns of change, with decreasing reproductive performance in the past decade. All other species including Western Gull (Larus occidentalis), Pigeon Guillemot (Cepphus columba), Xantus's Murrelet (Synthiloboramphus hypoleucus), Common Murre (Uria aalge), Cassin's Auklet (Ptychoramphus aleuticus) and Rhinoceros Auklet (Cerorhinca monocerata) showed diminishing reproductive performance through time. Patterns of change for the murre and auklets were not significant, presumably because of a lack of reproductive variation for these species, which display a conservative breeding effort (i.e. single-egg clutches). Changes in the birds' abilities to provision young and maintain chick survival during May–July each year appeared most closely related to overall changes in reproductive performance. Dietary change indicated a decline in use of juvenile rockfish (Sebastes spp.) by marine birds in central California. There was also significant interannual variability in consumption of juvenile rockfish and the euphausiid Thysanoessa spinifera. Patterns of change in marine bird reproductive performance were generally concordant between southern and central California after considering the period of recovery for Brown Pelican and Double-crested Cormorant. The decline in reproductive performance and changes in diet composition do not appear directly related to the polarity reversal of the Pacific Decadal Oscillation in 1976/1977. Instead, reproductive performance and dietary characteristics indicate substantial change in the late 1980s, suggesting another regime-shift at that time. 相似文献
86.
87.
The combined observations of Saturn's moon Enceladus by the Cassini CAPS, INMS and UVIS instruments detected water vapor geysers in which were present molecular nitrogen (N2), carbon dioxide (CO2), methane (CH4), propane (C3H8), acetylene (C2H2), and several other species, together with all of the decomposition products of water. We propose that the presence of N2 in the plume indicates thermal decomposition of ammonia, and hence high temperatures in the interior of the moon (e.g., 500 to 800 K). Such an environment also appears to be suitable for the production of methane (CH4) from carbon monoxide (CO), or carbon dioxide (CO2). The presence of C2H2 and C3H8 strongly suggest that catalytic reactions took place within a very hot environment. The internal environment of Enceladus is inferred to be or have been favorable for aqueous, catalytic chemistry. This permits the synthesis of many complex organic compounds that could be detected in future Cassini observations. 相似文献
88.
Stefanie Brachfeld Deepa Shah Emily First Julia Hammer Julie Bowles 《Meteoritics & planetary science》2015,50(10):1703-1717
We evaluate the relationship between the intensity of remanent magnetization and fO2 in natural and synthetic Mars meteorites. The olivine‐phyric shergottite meteorite Yamato 980459 (Y‐980459) and a sulfur‐free synthetic analog (Y‐98*) of identical major element composition were analyzed to explore the rock magnetic and remanence properties of a basalt crystallized from a primitive melt, and to explore the role of magmatic and alteration environment fO2 on Mars crustal anomalies. The reducing conditions under which Y‐980459 is estimated to have formed (QFM‐2.5; Shearer et al. 2006) were replicated during the synthesis of Y‐98*. Y‐980459 contains pyrrhotite and chromite. Chromite is the only magnetic phase in Y‐98*. The remanence‐carrying capacity of Y‐980459 is comparable to other shergottites that formed in the fO2 range of QFM‐3 to QFM‐1. The remanence‐carrying capacity of these low fO2 basalts is 1–2 orders of magnitude too weak to account for the intense crustal anomalies observed in Mars's southern cratered highlands. Moderately oxidizing conditions of >QFM‐1, which are more commonly observed in nakhlites and Noachian breccias, are key to generating either a primary igneous assemblage or secondary alteration assemblage capable of acquiring an intense remanent magnetization, regardless of the basalt character or thermal history. This suggests that if igneous rocks are responsible for the intensely magnetized crust, these oxidizing conditions must have existed in the magmatic plumbing systems of early Mars or must have existed in the crust during secondary processes that led to acquisition of a chemical remanent magnetization. 相似文献
89.
We report a study on the broadband ultraviolet photolysis of methane-water ice mixtures, at low methane concentrations and temperatures relevant to the icy satellites of the outer Solar System. The photochemistry of these mixtures is dominated by the action of hydroxyl radicals on methane and the resulting products. This implies that, given sufficient exposure time, the methane will eventually be completely oxidized to carbon dioxide. The presence of methane inhibits the formation of hydrogen peroxide by serving as a trap for hydroxyl radicals. The distribution of photochemical products is broadly similar to that previously conducted using ion and electron sources, with some differences possibly attributable to the difference in radiation source. The results are applicable to a variety of icy bodies in the Solar System. On Enceladus, where methane mixed with water is measured in the plumes, methane in the surface ices is subject to oxidation and will eventually be converted to CO2. The CH stretch feature detected in the VIMS spectra of the Enceladus surface ice suggests that methane is currently being supplied to the surface ice, likely from re-condensation of the plume gas. 相似文献
90.
In a previous paper (Gayon and Bois 2008a), we have shown the general efficiency of retrograde resonances for stabilizing
compact planetary systems. Such retrograde resonances can be found when two-planets of a three-body planetary system are both
in mean motion resonance and revolve in opposite directions. For a particular two-planet system, we have also obtained a new
orbital fit involving such a counter-revolving configuration and consistent with the observational data. In the present paper,
we analytically investigate the three-body problem in this particular case of retrograde resonances. We therefore define a
new set of canonical variables allowing to express correctly the resonance angles and obtain the Hamiltonian of a system harboring
planets revolving in opposite directions. The acquiring of an analytical “rail” may notably contribute to a deeper understanding
of our numerical investigation and provides the major structures related to the stability properties. A comparison between
our analytical and numerical results is also carried out. 相似文献