全文获取类型
收费全文 | 561篇 |
免费 | 28篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 11篇 |
大气科学 | 57篇 |
地球物理 | 94篇 |
地质学 | 223篇 |
海洋学 | 61篇 |
天文学 | 105篇 |
综合类 | 3篇 |
自然地理 | 39篇 |
出版年
2024年 | 3篇 |
2022年 | 3篇 |
2021年 | 5篇 |
2020年 | 11篇 |
2019年 | 11篇 |
2018年 | 17篇 |
2017年 | 24篇 |
2016年 | 13篇 |
2015年 | 19篇 |
2014年 | 18篇 |
2013年 | 25篇 |
2012年 | 23篇 |
2011年 | 19篇 |
2010年 | 26篇 |
2009年 | 22篇 |
2008年 | 32篇 |
2007年 | 24篇 |
2006年 | 22篇 |
2005年 | 16篇 |
2004年 | 34篇 |
2003年 | 13篇 |
2002年 | 16篇 |
2001年 | 10篇 |
2000年 | 16篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 8篇 |
1996年 | 4篇 |
1995年 | 8篇 |
1994年 | 7篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1990年 | 3篇 |
1989年 | 9篇 |
1988年 | 9篇 |
1987年 | 9篇 |
1986年 | 10篇 |
1985年 | 11篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 10篇 |
1981年 | 8篇 |
1980年 | 4篇 |
1977年 | 3篇 |
1976年 | 5篇 |
1975年 | 11篇 |
1971年 | 2篇 |
1956年 | 2篇 |
1955年 | 2篇 |
排序方式: 共有593条查询结果,搜索用时 421 毫秒
1.
2.
3.
4.
Tony T. Gregg Amanda Dewees Drema Gross Bill Hoffman Dan Strub Matt Watson 《中国海洋大学学报(英文版)》2006,5(4):375-380
1Water LossInitiativesUnaccounted-for water(or unbilled water)has beenreceiving newscrutiny at both the state and nationallevels.For years,water conservationeffortsin Europehave emphasized reduction in water loss to a muchgreater extent thaninthe United S… 相似文献
5.
Sophie Verheyden Dominique Genty Olivier Cattani Martin R. van Breukelen 《Chemical Geology》2008,247(1-2):266-281
Speleothem fluid inclusions are a potential paleo-precipitation proxy to reconstruct past rainwater isotopic composition (δ18O, δD). To get a better insight in the extraction of inclusion water from heated speleothem calcite, we monitored the water released from crushed and uncrushed speleothem calcite, heated to 900 °C at a rate of 300 °C/h, with a quadrupole mass spectrometer. Crushed calcite released water in three not well individualised peaks between 25 and 360 °C, 360 and 650 °C and between 650 and 800 °C while uncrushed calcite released water in two distinct temperature intervals: between 25 and 550 °C and between 550 and 900 °C.Water from two speleothems from the Han-sur-Lesse cave was recovered using three different techniques: i) the crushing and heating to 360 °C technique, ii) the decrepitation by heating to 550 °C and iii) the decomposition by heating to 900 °C technique. Measurements of the δD of water recovered by the decomposition of Han-sur-Lesse calcite heated to 900 °C did not show a 20 to 30‰ offset as found by previous authors. However a difference of 7‰ was observed between water released before and after decomposition of the calcite. Water recovery from the Han-sur-Lesse samples suggests that a simple heating technique (up to 550 °C) without crushing could both (a) recover water with δD representative of that of the drip water and (b) double the water yield as compared to the crushing and heating method.Our study warns for possible contamination of the recovered inclusion water with hydration water of lime, responsible for the recovery of water with very negative δD values. 相似文献
6.
7.
D. J. Mackey J. E. O'Sullivan R. J. Watson G. Dal Pont 《Deep Sea Research Part I: Oceanographic Research Papers》2002,49(12)
Profiles of total dissolvable Cd, Cu, Mn and Ni are reported for samples collected from the southwest Pacific in 1989, from the western equatorial Pacific along 155°E at 5°S, 0° and 5°N in 1990 and 1993, and along the equator from 143°E to 152°E and in the Bismarck Sea in 1997 and 2000. Profiles of Cd along 155°E in 1990 and along the equator were essentially the same but, in 1993, Cd values at 5°N were higher by a factor of about 1.5–2 than at 5°S over the depth range 500–1500 m. Similar, but less pronounced, differences were observed for PO4 and Ni. Cd and Ni were both strongly correlated with PO4, and an even stronger correlation was found between Ni and Cd. The concentration of Ni did not fall below ≈2 nmolkg−1, even in the nitrate-depleted waters of the western equatorial Pacific, where primary production is strongly dependent on recycled nitrogen (mainly ammonia and urea). It is proposed that this residual Ni is not bioavailable and that Ni could be biolimiting, since the metabolism of urea requires the nickel-containing enzyme urease. The impact of the Sepik River on Cd, Cu and Ni concentrations was small but elevated concentrations of Mn were observed near the Sepik River and close to the coast suggesting that the rivers and sediments on the north coast of New Guinea are a significant local source of Mn to the Bismarck Sea. Simple mass balance calculations show that the elevated levels of Mn observed in the Equatorial Undercurrent cannot be due to input from the rivers of New Guinea and they were attributed to the trapping of particulate matter due to strong current shear. A strong hydrothermal source of Mn was observed in the central Bismarck Sea. 相似文献
8.
9.
Watson W. Gregg Paul Ginoux Paul S. Schopf Nancy W. Casey 《Deep Sea Research Part II: Topical Studies in Oceanography》2003,50(22-26):3143
The JGOFS program and NASA ocean-color satellites have provided a wealth of data that can be used to test and validate models of ocean biogeochemistry. A coupled three-dimensional general circulation, biogeochemical, and radiative model of the global oceans was validated using these in situ data sources and satellite data sets. Biogeochemical processes in the model were determined from the influences of circulation and turbulence dynamics, irradiance availability, and the interactions among four phytoplankton functional groups (diatoms, chlorophytes, cyanobacteria, and coccolithophores) and four nutrients (nitrate, ammonium, silica, and dissolved iron).Annual mean log-transformed dissolved iron concentrations in the model were statistically positively correlated on basin scale with observations (P<0.05) over the eight (out of 12) major oceanographic basins where data were available. The model tended to overestimate in situ observations, except in the Antarctic where a large underestimate occurred. Inadequate scavenging and excessive remineralization and/or regeneration were possible reasons for the overestimation.Basin scale model chlorophyll seasonal distributions were positively correlated with SeaWiFS chlorophyll in each of the 12 oceanographic basins (P<0.05). The global mean difference was 3.9% (model higher than SeaWiFS).The four phytoplankton groups were initialized as homogeneous and equal distributions throughout the model domain. After 26 years of simulation, they arrived at reasonable distributions throughout the global oceans: diatoms predominated high latitudes, coastal, and equatorial upwelling areas, cyanobacteria predominated the mid-ocean gyres, and chlorophytes and coccolithophores represented transitional assemblages. Seasonal patterns exhibited a range of relative responses: from a seasonal succession in the North Atlantic with coccolithophores replacing diatoms as the dominant group in mid-summer, to successional patterns with cyanobacteria replacing diatoms in mid-summer in the central North Pacific. Diatoms were associated with regions where nutrient availability was high. Cyanobacteria predominated in quiescent regions with low nutrients.While the overall patterns of phytoplankton functional group distributions exhibited broad qualitative agreement with in situ data, quantitative comparisons were mixed. Three of the four phytoplankton groups exhibited statistically significant correspondence across basins. Diatoms did not. Some basins exhibited excellent correspondence, while most showed moderate agreement, with two functional groups in agreement with data and the other two in disagreement. The results are encouraging for a first attempt at simulating functional groups in a global coupled three-dimensional model but many issues remain. 相似文献
10.