全文获取类型
收费全文 | 441篇 |
免费 | 14篇 |
国内免费 | 12篇 |
专业分类
测绘学 | 2篇 |
大气科学 | 39篇 |
地球物理 | 129篇 |
地质学 | 119篇 |
海洋学 | 102篇 |
天文学 | 54篇 |
综合类 | 4篇 |
自然地理 | 18篇 |
出版年
2022年 | 3篇 |
2021年 | 5篇 |
2020年 | 2篇 |
2019年 | 7篇 |
2018年 | 8篇 |
2017年 | 9篇 |
2016年 | 9篇 |
2015年 | 7篇 |
2014年 | 24篇 |
2013年 | 18篇 |
2012年 | 20篇 |
2011年 | 23篇 |
2010年 | 19篇 |
2009年 | 27篇 |
2008年 | 17篇 |
2007年 | 23篇 |
2006年 | 21篇 |
2005年 | 24篇 |
2004年 | 15篇 |
2003年 | 9篇 |
2002年 | 17篇 |
2001年 | 14篇 |
2000年 | 14篇 |
1999年 | 12篇 |
1998年 | 11篇 |
1997年 | 7篇 |
1996年 | 5篇 |
1995年 | 7篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 7篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1978年 | 8篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 4篇 |
1971年 | 2篇 |
1970年 | 2篇 |
1968年 | 2篇 |
排序方式: 共有467条查询结果,搜索用时 15 毫秒
81.
82.
Rato M Gaspar MB Takahashi S Yano S Tanabe S Barroso C 《Marine pollution bulletin》2008,56(7):1323-1331
Imposex and organotin (OT) tissue contamination of the netted whelk Nassarius reticulatus (L.) were assessed in the continental shelves around the main estuaries of the central coast of Portugal (Lisbon: Tagus estuary; Setúbal: Sado estuary) and the main coastal lagoon in the Southern of Portugal (Faro: Ria Formosa). Pollution levels were higher in areas of more intense boat traffic and shipyard activities and imposex showed a clear decreasing gradient from the estuaries to the offshore, in relation to a similar gradient of tissue contamination by tributyltin. Remarkably, imposex was extensively spread over the adjacent continental shelves of Tagus and Sado estuaries. The current work shows that TBT pollution is undoubtedly a matter of concern not only for the above estuaries where harbours are implanted but also for the adjacent continental shelves, regardless the massive dilution of contaminants that may occur in these deeper areas. 相似文献
83.
84.
Nobuhiko Nakano Yasuhito Osanai Masaaki Owada Yasutaka Hayasaka Tran Ngoc Nam 《Island Arc》2009,18(1):126-143
The Kontum Massif in central Vietnam is composed of various metamorphic complexes including a high-temperature southern part (Kannak and Ngoc Linh complexes) and a low- to medium-temperature northern part (Kham Duc complex). The Kham Duc complex exhibits Barrovian-type medium-pressure metamorphism evidenced by kyanite- and/or staurolite-bearing metapelites. The garnet–gedrite–kyanite gneiss, which is the focus of the present study, preserves several mineral parageneses formed during a prograde and retrograde metamorphic history: staurolite + quartz in gedrite, garnet + gedrite + kyanite in the matrix, and spinel + cordierite symplectite between gedrite and sillimanite. The calculated semiquantitative petrogenetic grid reveals peak pressure conditions of 620–650°C at 1.1–1.2 GPa and peak temperature conditions of 730–750°C at 0.7–0.8 GPa. The monazite U–Th–Pb electron microprobe ages of the garnet–gedrite–kyanite gneiss and associated gneisses yield 246 ± 3 Ma for the Kham Duc complex, which is similar to the age of the high- to ultrahigh-temperature metamorphism in the adjacent Kannak and Ngoc Linh complexes of the southern Kontum Massif. The present results indicate that both the Barrovian-type and ultrahigh-temperature metamorphism occurred simultaneously in the Kontum Massif during an event strongly related to Permo–Triassic microcontinental collision tectonics in Asia. 相似文献
85.
86.
Stable carbon isotope distribution of particulate organic matter in the ocean: a model study 总被引:4,自引:0,他引:4
Matthias Hofmann Dieter A. Wolf-Gladrow Taro Takahashi Steward C. Sutherland Katharina D. Six Ernst Maier-Reimer 《Marine Chemistry》2000,72(2-4)
The stable carbon isotopic composition of particulate organic matter in the ocean, δ13CPOC, shows characteristic spatial variations with high values in low latitudes and low values in high latitudes. The lowest δ13CPOC values (−32‰ to −35‰) have been reported in the Southern Ocean, whereas in arctic and subarctic regions δ13CPOC values do not drop below −27‰. This interhemispheric asymmetry is still unexplained. Global gradients in δ13CPOC are much greater than in δ13CDIC, suggesting that variations in isotopic fractionation during organic matter production are primarily responsible for the observed range in δ13CPOC. Understanding the factors that control isotope variability is a prerequisite when applying δ13CPOC to the study of marine carbon biogeochemistry. The present model study attempts to reproduce the δ13CPOC distribution pattern in the ocean. The three-dimensional (3D) Hamburg Model of the Oceanic Carbon Cycle version 3.1 (HAMOCC3.1) was combined with two different parametrizations of the biological fractionation of stable carbon isotopes. In the first parametrization, it is assumed that the isotopic fractionation between CO2 in seawater and the organic material produced by algae, P, is a function of the ambient CO2 concentration. The two parameters of this function are derived from observations and are not based on an assumption of any specific mechanism. Thus, this parametrization is purely empirical. The second parametrization is based on fractionation models for microalgae. It is supported by several laboratory experiments. Here the fractionation, P, depends on the CO2 concentration in seawater and on the (instantaneous) growth rates, μi, of the phytoplankton. In the Atlantic Ocean, where most field data are available, both parametrizations reproduce the latitudinal variability of the mean δ13CPOC distribution. The interhemispheric asymmetry of δ13CPOC can mostly be attributed to the interhemispheric asymmetry of CO2 concentration in the water. However, the strong seasonal variations of δ13CPOC as reported by several authors, can only be explained by a growth rate-dependent fractionation, which reflects variations in the cellular carbon demand. 相似文献
87.
Shuichi Tanahashi Hiroshi Kawamura Toshihiko Matsuura Tomoyuki Takahashi Hiroyuki Yusa 《Journal of Oceanography》2000,56(3):345-358
We have developed an algorithm to estimate the wide-ranging Sea Surface Temperature (SST) data from the GMS-5 (Geostationary Meteorological Satellite) S-VISSR (Stretched-Visible Infrared Spin Scan Radiometer). Better SST estimates are realized by averaging the temporal variation of the VISSR calibration table and decreasing noise of the split-window terms using a spatial filter. The effects of the satellite zenith angle were examined in detail for better estimates, and VISSR-derived SSTs with root-mean-square (rms) error of 0.8 K were achieved using a new algorithm. The accuracy of SST estimates has been improved by using the temporal-spatial average of the split-window terms. Using the new techniques, we demonstrate that the hourly wide-ranging SST image data can be used to study the daily variations of SSTs in the Northern and Southern Pacific Oceans. 相似文献
88.
Very large short lived enhancements observed in Na nightglow measurements are described. Only nine such events have been observed in about 8 years of regular nocturnal observations at 23°S. These enhancements are believed to be due to excess sodium deposited in the upper atmosphere by meteoroid ablation. The cases observed are not always correlated with known meteor showers, except perhaps in June with χ Scorpiids and θ Ophiuchids. 相似文献
89.
The upper mesosphere airglow emissions OI 5577, NaD and OH have been observed at Cachoeira Paulista (22.7°S; 45.0°W) Brazil. Nocturnal variations and their seasonal dependencies in amplitude and phase, and the annual variations of these emissions are presented, analysing the data obtained from 1977 to 1982 during the ascending phase of the last solar cycle. The nocturnal variations of the OI 5577 emission and the OH rotational temperature showed a significant semidiurnal oscillation, with the phase of maximum moving from midnight in January to early morning in June. Semiannual variation of the OI 5577 and NaD emissions with the maximum intensities in April/May and October/November were observed. The OH rotational temperature, however, showed an annual variation, maximum in summer and minimum in winter, while no significant seasonal variation was found in the OH emission intensities. Long-term intensity variations are also presented with the solar sunspot numbers and the 10.7 cm flux. 相似文献
90.
Kenzo Toki Tadanobu Sato Junji Kiyono Nozar Kishi Garmroudi Susumu Emi Masaaki Yoshikawa 《地震工程与结构动力学》1991,20(10):895-909
Non-linear seismic soil-pile interaction was studied with a hybrid procedure that used a pseudo-dynamic testing (PDT) method modified to account for frequency dependence and developed for foundation-soil systems. The numerical scheme used in the conventional PDT was improved by the introduction of a time-dependent pseudo-forcing function derived from the frequency-dependent dynamic characteristics of the system by Hilbert transformation in the frequency domain. Single, 2-, 3- and 9-pile group foundation models were used, their mechanical characteristics later being determined from static and forced vibration dynamic tests. Amplitude scaling was used for three recorded accelerograms. Data recorded during an earthquake at the site of the experiments revealed that the proposed methodology predicts well seismic nonlinear interaction and accounts for frequency dependence and non-linearity in the time domain. 相似文献