全文获取类型
收费全文 | 712篇 |
免费 | 26篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 24篇 |
大气科学 | 73篇 |
地球物理 | 162篇 |
地质学 | 262篇 |
海洋学 | 69篇 |
天文学 | 74篇 |
综合类 | 2篇 |
自然地理 | 76篇 |
出版年
2023年 | 3篇 |
2022年 | 3篇 |
2021年 | 2篇 |
2020年 | 13篇 |
2019年 | 10篇 |
2018年 | 27篇 |
2017年 | 20篇 |
2016年 | 25篇 |
2015年 | 22篇 |
2014年 | 23篇 |
2013年 | 27篇 |
2012年 | 25篇 |
2011年 | 34篇 |
2010年 | 41篇 |
2009年 | 52篇 |
2008年 | 43篇 |
2007年 | 39篇 |
2006年 | 22篇 |
2005年 | 37篇 |
2004年 | 25篇 |
2003年 | 24篇 |
2002年 | 22篇 |
2001年 | 15篇 |
2000年 | 7篇 |
1999年 | 10篇 |
1998年 | 17篇 |
1997年 | 4篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 8篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 7篇 |
1984年 | 16篇 |
1983年 | 7篇 |
1982年 | 11篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 7篇 |
1978年 | 8篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1973年 | 4篇 |
排序方式: 共有742条查询结果,搜索用时 15 毫秒
1.
2.
3.
Barbara Rubin 《The Professional geographer》1979,31(2):125-134
The representation of women on geography faculties did not increase appreciably between 1971 and 1977, but women in other academic disciplines have fared somewhat better. The latter have improved their status primarily as a result of actions taken by professional associations representing their fields. When a professional association ignores its female constituency or refuses to commit itself to improving their circumstances, federal agencies now offer alternative channels for obtaining redress. 相似文献
4.
Gerd Rantitsch Reinhard F. Sachsenhofer Christian Hasenhüttl Barbara Russegger Thomas Rainer 《Tectonophysics》2005,411(1-4):57-72
Following Early Cretaceous nappe stacking, the Eastern Alps were affected by late-orogenic extension during the Late Cretaceous. In the eastern segment of this range, a Late Cretaceous detachment separates a very low- to low-grade metamorphic cover (Graz Paleozoic Nappe Complex, GPNC) above a low- to high-grade metamorphic basement. Synchronously, the Kainach Gosau Basin (KGB) collapsed and subsided on top of the section.Metamorphism of organic material within this section has been investigated using vitrinite reflectance data and Raman spectra of extracted carbonaceous material. In the southern part of the GPNC, vitrinite reflectance indicates a decrease in organic maturity towards the stratigraphic youngest unit. The remaining part of the GPNC is characterized by an aureole of elevated vitrinite reflectance values and Raman R2 ratios that parallels the margins of the GPNC. Vitrinite reflectance in the KGB shows a steep coalification gradient and increases significantly towards the western basin margin. The observed stratigraphic trend in the southern GPNC is a result of deep Paleozoic to Early Cretaceous burial. This maturity pattern was overprinted along the margins by advective heat and convective fluids during Late Cretaceous to Paleogene exhumation of basement rocks.During shearing, the fault zone was heated up to ca. 500 °C. This overprint is explained by a two-dimensional thermal model with a ramp-flat fault geometry and a slip rate of 1 to 1.5 cm/year during 5 Ma fault movement. The collapse basin above the detachment subsided in a thermal regime which was characterized by relaxing isotherms. 相似文献
5.
6.
Magnetic properties of the profiles of polluted and non-polluted soils. A case study from Ukraine 总被引:7,自引:0,他引:7
7.
Measured spectra ofθ
x,θ
y,θ
z, the derivatives of temperature in streamwise, lateral and vertical directions, respectively, indicate that the spectral
densities ofθ
z andθ
y are nearly similar but significantly different from the spectral density ofθ
x. The high-frequency parts of the three spectra satisfy, in a qualitative sense, local isotropy requirements. In the high-frequency
end of the inertial subrange, the relative behaviour of spectra ofθ
x,θ
y andθ
z is also consistent with local isotropy. 相似文献
8.
An integrated mass balance and modelling approach for analysis of estuarine nutrient fluxes is demonstrated in the Swan River Estuary, a microtidal system with strong hydrological dependence on seasonal river inflows. Mass balance components included estimation of gauged and ungauged inputs to the estuary and losses to the ocean (outflow and tidal exchange). Modelling components included estimation of atmospheric (N fixation, denitrification) and sediment–water column nutrient exchanges. Gross and net denitrification derived using two independent methods were significantly correlated (r2 = 0.49, p < 0.01) with net rates averaging 40% of gross. Annual nitrogen (N) and phosphorus (P) loads from major tributaries were linearly correlated with annual freshwater discharge and were 3-fold higher in wet years than in dry years. Urban drains and groundwater contributed, on average, 26% of N inputs and 19% of P inputs, with higher relative contributions in years of low river discharge. Overall, ungauged inputs accounted for almost 35% of total nitrogen loads. For N, elevated loading in wet years was accompanied by large increases in outflow (7x) and tidal flushing (2x) losses and resulted in overall lower retention efficiency (31%) relative to dry years (70%). For P, tidal flushing losses were similar in wet and dry years, while outflow losses (4-fold higher) were comparable in magnitude to increases in loading. As a result, P retention within the estuary was not substantially affected by inter-annual variation in water and P loading (ca. 50% in all years). Sediment nutrient stores increased in most years (remineralisation efficiency ca. 50%), but sediment nutrient releases were significant and in some circumstances were a net source of nutrients to the water column. 相似文献
9.
10.
Brian N. Tissot Barbara A. Best Eric H. Borneman Andrew W. Bruckner Cara H. Cooper Heather D’Agnes Timothy P. Fitzgerald Amanda Leland Susan Lieberman Amy Mathews Amos Rashid Sumaila Teresa M. Telecky Frazer McGilvray Brian J. Plankis Andrew L. Rhyne Glynnis G. Roberts Benjamin Starkhouse Todd C. Stevenson 《Marine Policy》2010
As the world’s largest importer of marine ornamental species for the aquaria, curio, home décor, and jewelry industries, the United States has an opportunity to leverage its considerable market power to promote more sustainable trade and reduce the effects of ornamental trade stress on coral reefs worldwide. Evidence indicates that collection of some coral reef animals for these trades has caused virtual elimination of local populations, major changes in age structure, and promotion of collection practices that destroy reef habitats. Management and enforcement of collection activities in major source countries such as Indonesia and the Philippines remain weak. Strengthening US trade laws and enforcement capabilities combined with increasing consumer and industry demand for responsible conservation can create strong incentives for improving management in source countries. This is particularly important in light of the March 2010 failure of the parties to the Convention on International Trade in Endangered Species (CITES) to take action on key groups of corals. 相似文献