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排序方式: 共有466条查询结果,搜索用时 233 毫秒
1.
Daniel Lane Colin P.R. McCarter Murray Richardson Chris McConnell Tim Field Huaxia Yao George Arhonditsis Carl P.J. Mitchell 《水文研究》2020,34(3):598-614
The estimation of hydrologic transit times in a catchment provides insights into the integrated effects of water storage, mixing dynamics, and runoff generation processes. There has been limited effort to estimate transit times in southern boreal Precambrian Shield landscapes, which are characteristically heterogeneous with surface cover including till, thin soils, bedrock outcrops, and depressional wetland features that play contrasting hydrologic roles. This study presents approximately 3.5 years of precipitation and streamflow water isotope data and estimates mean transit times (MTTs) and the young water fraction (py) across six small catchments in the Muskoka-Haliburton region of south-central Ontario. The main objectives were to define a typical range of MTTs for headwater catchments in this region and to identify landscape variables that best explain differences in MTTs/py using airborne light detection and ranging and digital terrain analysis. Of the transit time distributions, the two parallel linear reservoir and gamma distributions best describe the hydrology of these catchments, particularly because of their ability to capture more extreme changes related to events such as snowmelt. The estimated MTTs, regardless of the modelling approach or distribution used, are positively associated with the percent wetland area and negatively with mean slope in the catchments. In this landscape, low-gradient features such as wetlands increase catchment scale water storage when antecedent conditions are dryer and decrease transit times when there is a moisture surplus, which plausibly explains the increases in MTTs and mean annual runoff from catchments with significant coverage of these landscape features. 相似文献
2.
PROPAGATION OF 30—60 DAY LOW FREQUENCY OSCILLATIONS AND THEIR INFLUENCE UPON THE SUBTROPICAL WESTERLIES JET STREAM DURING NORTHERN HEMISPHERE WINTER 下载免费PDF全文
Based on daily ECMWF gridpoint data of two winters during 1981—1983 including an ENSOyear,propagation of low frequency oscillations(LFO)during Northern Hemisphere winters andtheir influences upon 30—60 day oscillations of the subtropical jet stream are studied with the sta-tistical methods as complex empirical orthogonal function(CEOF)and so on.Results show that inthe winter of a normal year(1981—1982),30—60 day oscillations in the subtropical zone aremainly in the northern and southern flanks of exit region of jet stream.In the ENSO year(1982—1983),they are mainly in the vicinity of entrance and exit regions of jet stream.Intraseasonalchanges of subtropical jet stream manifested themselves as latitudinal fluctuation or longitudinalprogression or regression of about 40 day period.There are marked differences between propagat-ing passages of low frequency modes responsible for changes of subtropical jet stream in the normalyear(1981—1982)and in the ENSO year(1982—1983).Changes of oscillation amplitude showobvious phases.In general,the one in late winter is stronger than that in early winter,strongestone occurs in February. 相似文献
3.
Gao Yinli Yan Shuwang Wang Jinying
Graduate Student Tianjin University Tianjin
Professor Tianjin University Tianjin
Senior Engineer China Offshore Oil Engineering Co. 《中国海洋工程》1995,(1)
This paper introduces a stability design system of submarine pipelines. The system can provide a reasonable design procedure for users with reference to domestic and foreign methods and in the light of home engineering experience. 相似文献
4.
Fractal Dimension and Fractals in Ocean Engineering 总被引:4,自引:0,他引:4
Fu Yuhua Senior Engineer China Offshore Oil Engineering Corporation P. O. Box Beijing 《中国海洋工程》1994,(3)
- This paper discusses the application of fractal dimension and fractals in ocean engineering. To handle some ocean environment problems, the existing fractal method, in which the fractal dimension is a constant, can be used. For some complicated problems in ocean engineering, this paper presents the concept of the variable dimension fractals (D = f(r)), i. e., the fractal dimension D is the function of characteristic scale r instead of a constant. By using variable dimension fractals, several deformation and stress states of offshore structures are described. 相似文献
5.
6.
A Unified Variational Principle of Fluid Mechanics and Application on Solitary Subdomain or Point 总被引:1,自引:0,他引:1
-According to basic equations of fluid mechanics, this paper presents a unified variational principle of fluid mechanics (UVPFM) by using the optimization method of weighted residuals (OMWR). The advantages are as follows, the establishment of the functional and the variational principle is easy, it can change various problems of fluid mechanics derived by basic equations into a unified optimization problem, and the solution is the optimum one in some sense. According to the OMWR for the solitary subdomain, this paper uses UVPFM onto any solitary subdomain and gives the solution of the hydrodynamics equation which is suitable only for that solitary subdomain. According to the OMWR for solitary point, this paper uses UVPFM to any solitary point and gives the solution of the hydrodynamics equation (point solution) which is suitable only for that solitary point. As the solution for the solitary subdomain or solitary point is developed independently, the compatibility with other subdomain or other points, do 相似文献
7.
In 1980, a large earthquake caused extensive sediment failure on the shallow continental shelf off the Klamath River in northern
California. Side-scan sonography was used to complement detailed geophysical profiling in identifying specific features and
resolving modes of failure. The features include a nearly flat failure terrace mantled with sand boils, collapse craters and
sediment flows, and bounded on the seaward side by a meandering continuous toe ridge. Seaward of the terrace lies a compression
zone delineated by small pressure ridges. Our findings indicate a temporal progression of failure from lique-faction of shallow
subsurface sand to lateral spread of intact blocks to sediment collapse and flow. 相似文献
8.
Several aspects of the Maryland ridge field are pertinent to the problem of ridge genesis in response to Holocene sea-level
rise. There is a systematic morphologic change fromshoreface ridges throughnearshore ridges tooffshore ridges, which reflects the changing hydraulic regime. Grain size is 90° out of phase with topography, so that the coarsest sand
lies between the axis of each trough and the adjacent seaward ridge crest, while the finest sand lies between each ridge crest
and the axis of the adjacent seaward trough. Finally, analysis over a 43-year period on an outer ridge reveals a systematic
pattern of landward flank erosion, seaward flank deposition, and seaward crest migration.
These relationships support a model which explains the ridges as consequences of the up-current shift of maximum bottom shear
stress with respect to the crests of initial bottom irregularities. The oblique orientation of the ridges with respect to
the beach may be at least partly due to the more rapid migration rate of the ridges’ inshore ends. 相似文献
9.
Breakthrough tailing has been observed during dye-tracing recovery tests in the Norville aquifer system (chalk), France. Karst-conduit flow and transport parameters were assessed using two different interpretative methods: the linear graphical method and the Chatwin method (implemented in the Qtracer2 program). The linear graphical method was used to model the observed tailing effects, which was explained by a second smaller delayed breakthrough curve. By comparing the results of tracer-test interpretation for the two methods, it was possible to relate the area of this second curve to the importance of turbulent flow in spring discharge. The more turbulent the flow, the less important the contribution of the second breakthrough curve and the tailing effect. The observed tailing could possibly be controlled by hydrodynamics to a greater extent than usually expected, the tailing effects being mostly attributed to diffusion phenomena. Tailing effects were expected to increase with discharge and the piezometric level, which would have resulted in overpressure in conduits, fissure flooding, etc. Instead, breakthrough tailing tended to disappear with increasing aquifer discharge, which would support the hypothesis of there being mostly hydrodynamic-controlled tailing effects instead of matrix- or fissure-diffusion.An erratum to this article can be found at 相似文献
10.
SUN Xiao-jie LI Chao-lin WANG Li-bin REN Ri-chun LI Hai-yan ZHUANG Yi-ming LIU Ying-xin SUN Ke .Daqing Petroleum Institute Daqing Heilongjiang China .Coalfield Geological Geophysical Exploration Company of Jilin Province Changchun China .Coal Field Geology Bureun of Jilin Province Changchun China 《吉林大学学报(地球科学版)》2006,(Z2)
已知勘查区深度范围前提下,最大炮检X和道间距ΔX,不可以太大也不可以太小,施工前能够计算出它的允许值范围。 相似文献