全文获取类型
收费全文 | 287篇 |
免费 | 11篇 |
国内免费 | 12篇 |
专业分类
测绘学 | 7篇 |
大气科学 | 23篇 |
地球物理 | 69篇 |
地质学 | 119篇 |
海洋学 | 28篇 |
天文学 | 46篇 |
综合类 | 4篇 |
自然地理 | 14篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 9篇 |
2020年 | 5篇 |
2019年 | 9篇 |
2018年 | 17篇 |
2017年 | 14篇 |
2016年 | 14篇 |
2015年 | 17篇 |
2014年 | 21篇 |
2013年 | 18篇 |
2012年 | 12篇 |
2011年 | 15篇 |
2010年 | 21篇 |
2009年 | 21篇 |
2008年 | 15篇 |
2007年 | 18篇 |
2006年 | 11篇 |
2005年 | 8篇 |
2004年 | 12篇 |
2003年 | 6篇 |
2002年 | 8篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 1篇 |
1998年 | 7篇 |
1997年 | 6篇 |
1996年 | 2篇 |
1995年 | 4篇 |
1993年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1980年 | 1篇 |
1965年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有310条查询结果,搜索用时 8 毫秒
51.
M. V. Charykova V. G. Krivovichev O. S. Yakovenko V. V. Semenova K. N. Semenov W. Depmeier 《Geology of Ore Deposits》2012,54(8):638-646
The understanding of the mechanisms of the selenium behavior under near-surface conditions is an urgent problem of modern mineralogy and geochemistry, and is very important for solving environmental problems. The objective of this study is to synthesize analogs of ahlfeldite and cobaltomenite and to estimate their solubility in water. These analogs have been synthesized by mixing aqueous solutions of cobalt and nickel nitrates, respectively, and sodium selenite acidified with a solution of nitric acid. The obtained samples have been identified by X-ray diffraction and IR spectroscopy. The solubility has been determined by the isothermal saturation method in ampoules at 25°C, while the solubility products have been calculated using the Geochemist’s Workbench (GMB 7.0) software package. The solubility products of ahlfeldite and cobaltomenite are 10?9.20 and 10?9.44, respectively. The Eh-pH diagrams were calculated and plotted with the GMB 7.0 software package. The Eh-pH diagrams of the Ni-Se-H2O and Co-Se-H2O systems have been calculated for the average contents of these elements in underground water and their contents in acidic water of the oxidation zone of sulfide deposits. The formation of ahlfeldite and cobaltomenite under near-surface conditions is discussed. 相似文献
52.
53.
Numerical Modeling of Hydraulic Fractures Interaction in Complex Naturally Fractured Formations 总被引:1,自引:0,他引:1
Olga Kresse Xiaowei Weng Hongren Gu Ruiting Wu 《Rock Mechanics and Rock Engineering》2013,46(3):555-568
A recently developed unconventional fracture model (UFM) is able to simulate complex fracture network propagation in a formation with pre-existing natural fractures. A method for computing the stress shadow from fracture branches in a complex hydraulic fracture network (HFN) based on an enhanced 2D displacement discontinuity method with correction for finite fracture height is implemented in UFM and is presented in detail including approach validation and examples. The influence of stress shadow effect from the HFN generated at previous treatment stage on the HFN propagation and shape at new stage is also discussed. 相似文献
54.
M. V. Charykova V. G. Krivovichev O. S. Yakovenko V. V. Semenova K. N. Semenov W. Depmeier 《Geology of Ore Deposits》2013,55(7):525-531
Understanding the mechanisms of arsenic’s behavior under near-surface conditions is one of the actual problems of contemporary mineralogy and geochemistry and is important for solving environmental problems. The aim of this study is to synthesize analogs of erythrite and annabergite and to investigate their solubility in water. These phases have been synthesized by the boiling-dry of aqueous solutions of cobalt and nickel nitrates mixed with sodium hydroarsenate alkalized with NaOH. The samples obtained have been identified with electron microprobe, X-ray diffraction, and IR spectroscopy. Solubility has been determined by the isothermal saturation method in ampoules at 25°C. The solubility has been calculated using the Geochemist’s Workbench (GMB 7.0) software package. The measured solubilities of erythrite and annabergite are 10?35.76 and 10?36.43, respectively. Eh-pH diagrams were calculated and plotted using the GMB 7.0 software package. The database comprises the thermodynamic parameters of 46 elements, 47 main particles, 48 redox pairs, 552 particles in solution, 624 solid phases, and 10 gases. The Eh-pH diagrams of the Ni-As-H2O and Co-As-H2O systems were plotted for the average contents of these elements in the acidic waters in the oxidation zones of sulfide deposits. The formation of erythrite and annabergite under near-surface conditions is discussed. 相似文献
55.
The Hydrograph model (a distributed process-based model) was applied to the simulation of soil freeze-thaw and runoff processes, to assess the viability of the model approach and the influence of specific environmental factors in a permafrost environment. Three mountainous permafrost watersheds were studied, at the Kolyma Water Balance Station in north-eastern Russia. The watersheds include rocky talus, mountainous tundra and moist larch-forest landscape regimes, and they were modelled at daily time-steps for the period 1971–1984. Simulated results of soil freeze-thaw depth and runoff showed reasonable agreement with observed values. This study reveals and mathematically describes the dependence of surface and subsurface flow on thawing depth and landscape characteristics. Process analysis and modelling in permafrost regions, including ungauged basins, is suggested, with observable properties of landscapes being used as model parameters, combined with an appropriate level of physically based conceptualization. 相似文献
56.
Cd, Cu, Fe, Mn, Ni, Pb, Zn concentration in the organs (muscle, gonads, mantle, gills, digestive gland, kidney) of mussel Modiolus modiolus was studied. Mussels were collected from shelf upwelling sites of Kuril Is. Sea of Okhotsk (104 and 85 m) and, for comparison, coastal high contaminated and clean sites (Peter the Great Bay, Sea of Japan). It was found that mussels from shelf upwelling regions accumulated unusually high Cd concentration in studied organs, excepting digestive gland. Shelf mussels have evolved passive adaptation to elevated level of ambient heavy metals (distribution of heavy metal load between all organs, especially, muscle). In contrast, mussels from high contaminated sites have evolved active adaptation (strong regulation of metal concentration in the organs at the maximal permissible concentration due to increased kidney function). We supported that under natural condition, passive adaptation of aquatic organisms to increased ambient metal level have been evolved only under constant low-water temperature. 相似文献
57.
Nino MATESHVILI Giuli MATESHVILI Iuri MATESHVILI Lev GHEONDJIAN Olga AVSAJANISHVILI 《Meteoritics & planetary science》1999,34(6):969-973
Abstract— Photometric observations of the twilight sky were carried out during Leonids 1998. The obtained vertical distributions of aerosol between 20 and 140 km demonstrate the processes of the intrusion of fine meteor dust and its subsequent intra-atmospheric dynamics. The characteristic radii of two fractions of the meteor dust particles were estimated by their sedimentation velocities. They varied within rp = 0.006–0.06 μm and rp = 19–81 μm limits depending on an assumed particle density within ρp = 0.4–4.0 g cm?3. The assumption of ρp = 2.0 g cm?3 gave radii of the two fractions to be 0.01 and 30 μm, respectively. 相似文献
58.
We have investigated the frustule ultrastructure of Baikalian Aulacoseira: A.baicalensis (K.Meyer) Sim. and of thin-wall, spore-producing Aulacoseira which has long been designated as A. islandica (O.Muller) Sim. or A.islandica ssp. helvetica (O.Muller) Sim. (now A.skvortzowii Edlund, Stoermer,Taylor). It was found that the disagreement on the name of spore-forming Aulacoseira is due to the destruction of its vegetative frustules in the process of breaking free of the organic content, while ultrastructure data on A.islandica from different Russia''s regions can reflect signatures of different species.A. baicalensis is characterized by great polymorphism. A. baicalensis starts its development from the initial cell (auxospore). The morphological characteristics of the frustule undergo the drastic changes in the course of the life cycle. It sequentially changes the morphology and structure of its valves. Its cells evolve through several stages of development:from cyclotella-like cells to narrow and short reproducing cells. In the influence zone of the Baikalsky Pulp-and-Paper Plant (BPPP), waste waters, disturbances in the frustule structure both in vegetative and generative cells have been detected. 相似文献
59.
Upper Cambrian to Middle Ordovician radiolarian chert successions from Kazakhstan were studied to clarify the history of the emergence of benthic animals in ocean floor sediments. Radiolarian tests and clay were deposited for a period of 30 Myr without experiencing an influx of continent-derived coarse clastic materials. Red, grey and black cherts of the Upper Cambrian to the upper mid-Darriwilian are thinly laminated, and no trace of benthic animal activity is recognized in that time interval. Bioturbation structures and burrow traces in mid-Darriwilian stage red chert in Kazakhstan suggest that benthic animals colonized the location where radiolarian chert formed, but that there was a significant delay in colonization when compared with similar reported occurrences in Australia and Canada. 相似文献
60.