全文获取类型
收费全文 | 801篇 |
免费 | 24篇 |
国内免费 | 5篇 |
专业分类
测绘学 | 36篇 |
大气科学 | 73篇 |
地球物理 | 205篇 |
地质学 | 230篇 |
海洋学 | 63篇 |
天文学 | 126篇 |
自然地理 | 97篇 |
出版年
2021年 | 9篇 |
2020年 | 10篇 |
2019年 | 11篇 |
2018年 | 15篇 |
2017年 | 10篇 |
2016年 | 25篇 |
2015年 | 23篇 |
2014年 | 26篇 |
2013年 | 40篇 |
2012年 | 46篇 |
2011年 | 34篇 |
2010年 | 25篇 |
2009年 | 42篇 |
2008年 | 38篇 |
2007年 | 35篇 |
2006年 | 27篇 |
2005年 | 40篇 |
2004年 | 34篇 |
2003年 | 25篇 |
2002年 | 26篇 |
2001年 | 22篇 |
2000年 | 13篇 |
1999年 | 13篇 |
1998年 | 20篇 |
1997年 | 20篇 |
1996年 | 9篇 |
1995年 | 7篇 |
1994年 | 7篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1990年 | 16篇 |
1989年 | 9篇 |
1988年 | 3篇 |
1987年 | 8篇 |
1986年 | 7篇 |
1985年 | 11篇 |
1984年 | 14篇 |
1983年 | 6篇 |
1982年 | 11篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1979年 | 10篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1976年 | 9篇 |
1975年 | 4篇 |
1973年 | 4篇 |
1972年 | 3篇 |
1971年 | 4篇 |
1970年 | 4篇 |
排序方式: 共有830条查询结果,搜索用时 15 毫秒
731.
The localization of electronics manufacturing in the Greater Pearl River Delta, China: Do global implants put down local roots? 总被引:1,自引:0,他引:1
Against the background of a recent shift in growth dynamics from export-oriented activities towards the domestic market in Chinese regions, it is the aim of this paper to demonstrate how the spatial organization of the electronics industry in Hong Kong and the Pearl River Delta has evolved over time and to assess the impact of the institutional setting and differences between Hong Kong and the Pearl River Delta on localization and upgrading of the industry. The empirical findings suggest a strong trend towards the localization of business activities in China and a differentiated perspective regarding the kinds of activities that are more likely to be localized. An advanced front shop, back factory model with complementary, but intertwined assets has been identified. The institutional interpretation of spatial processes has proven its potential to further develop contextually sensitive concepts for the economic geography of China. 相似文献
732.
733.
Ocean wave characteristics around New Zealand 总被引:1,自引:1,他引:0
Nearly 17 years wave records from deep water and shore‐based stations are used to describe the ocean wave characteristics around New Zealand. The wave environment is dominated by west and southwest swell and storm waves generated in the temperate latitude belt of westerly winds. As a result, the west and south coasts are exposed, high energy shores, the east coast is a high energy lee shore, and the northern coast from North Cape to East Cape is a low energy lee shore sheltered from these winds and waves. South of New Zealand, wave energies are extremely high; the prevailing deep water wave is 3.5–4.5 m high and has a 10–12 s period, with a slight increase in wave heights in winter. The west coast wave environment is mixed, and consists of locally generated westerly and southerly storm waves, and swell waves generated to the south. The prevailing wave is t.0–3.0 m and 6–8 s period. There are no strong seasonal rhythms, only shorter period cycles of wave height (5 day) associated with similar quasi‐rhythmic cycles in the weather. The east coast also has a mixed wave climate with southerly swells, originating in the westerlies south of New Zealand, and locally generated southerly and northerly storm waves. The prevailing wave is 0.5–2.0 m and 7–11 s period. A short period rhythmic cycle, similar to that on the west coast, is superimposed on a weak seasonal cycle. The seasonal, cycle results from an increase in the frequency of local northerly waves in summer. The prevailing wave on the north coast is a northeasterly, 0.5–1.5 m high and 5–7 s period. Subtropical disturbances and southward‐moving depressions generate a mixed wave environment and a possible seasonally reflecting a winter increase in. storminess. 相似文献
734.
Charles P. Mitchell 《新西兰海洋与淡水研究杂志》2013,47(3):325-336
Galaxias maculatus has considerable potential as a laboratory animal. Laboratory techniques used to maintain, artificially spawn, hatch, and rear this New Zealand native freshwater fish are described. Potential research applications for the fish, the eggs, and the larvae are outlined. The development of the larvae is described. 相似文献
735.
Ekaterina V. KOROCHANTSEVA Susanne P. SCHWENZER Alexei I. BUIKIN Jens HOPP Ulrich OTT Mario TRIELOFF 《Meteoritics & planetary science》2011,46(9):1397-1417
Abstract– We present 40Ar‐39Ar dating results of handpicked mineral separates and whole‐rock samples of Nakhla, Lafayette, and Chassigny. Our data on Nakhla and Lafayette and recently reported ages for some nakhlites and Chassigny ( Misawa et al. 2006 ; Park et al. 2009 ) point to formation ages of approximately 1.4 Ga rather than 1.3 Ga that is consistent with previous suggestions of close‐in‐time formation of nakhlites and Chassigny. In Lafayette mesostasis, we detected a secondary degassing event at approximately 1.1 Ga, which is not related to iddingsite formation. It may have been caused by a medium‐grade thermal event resetting the mesostasis age but not influencing the K‐Ar system of magmatic inclusions and the original igneous texture of this rock. Cosmic‐ray exposure ages for these meteorites and for Governador Valadares were calculated from bulk rock concentrations of cosmogenic nuclides 3He, 21Ne, and 38Ar. Individual results are similar to literature data. The considerable scatter of T3, T21, and T38 ages is due to systematic uncertainties related to bulk rock and target element chemistry, production rates, and shielding effects. This hampers efforts to better constrain the hypothesis of a single ejection event for all nakhlites and Chassigny from a confined Martian surface terrain ( Eugster 2003 ; Garrison and Bogard 2005 ). Cosmic‐ray exposure ages from stepwise release age spectra using 38Ar and neutron induced 37Ar from Ca in irradiated samples can eliminate errors induced by bulk chemistry on production rates, although not from shielding conditions. 相似文献
736.
737.
SeaSat-A Satellite Scatterometer (SASS) measurements of normalized radar cross section (NRCS) have been merged with high quality surface-wind fields based on in situ, to create a large data base of NRCS-wind signature data. These data are compared to the existing NRCS-wind model used by the SASS to infer winds. False-color maps of SASS NRCS and ocean winds from multiple orbits show important synoptic trends. 相似文献
738.
Detachment of the deeper part of subducted lithosphere causes changes in a subduction zone system which may be observed on the Earth's surface. Constraints on the expected magnitudes of these surface effects can aid in the interpretation of geological observations near convergent plate margins where detachment is expected. In this study, we quantify surface deformation caused by detachment of subducted lithosphere. We determine the range of displacement magnitudes which can be associated with slab detachment using numerical models. The lithospheric plates in our models have an effective elastic thickness, which provides an upper bound for rapid processes, like slab detachment, to the surface deformation of lithosphere with a more realistic rheology. The surface topography which develops during subduction is compared with the topography shortly after detachment is imposed. Subduction with a non-migrating trench system followed by detachment leads to a maximum surface uplift of 2–6 km, while this may be higher for the case of roll-back preceding detachment. In the latter situation, the back-arc basin may experience a phase of compression after detachment. Within the context of our elastic model, the surface uplift resulting from slab detachment is sensitive to the depth of detachment, a change in friction on the subduction fault during detachment and viscous stresses generated by sinking of the detached part of the slab. Overall, surface uplift of these magnitudes is not diagnostic of slab detachment since variations during ongoing subduction may result in similar vertical surface displacements. 相似文献
739.
Uncompacted artificial-fill deposits on the east side of San Francisco Bay suffered severe levels of soil liquefaction during the Loma Prieta earthquake of 17 October 1989. Damaged areas included maritime-port facilities, office buildings, and shoreline transportation arteries, ranging from 65 to 85 km from the north end of the Loma Prieta rupture zone. Typical of all these sites, which represent occurrences of liquefaction-induced damage farthest from the rupture zone, are low cone penetration test and Standard Penetration Test resistances in zones of cohesionless silty and sandy hydraulic fill, and underlying soft cohesive Holocene and Pleistocene sediment that strongly amplified ground motions. Postearthquake investigations at five study sites using standard penetration tests and cone penetration tests provide a basis for evaluation of the Arias intensity-based methodology for assessment of liquefaction susceptibility. 相似文献
740.