全文获取类型
收费全文 | 426篇 |
免费 | 1篇 |
国内免费 | 11篇 |
专业分类
测绘学 | 17篇 |
大气科学 | 12篇 |
地球物理 | 58篇 |
地质学 | 90篇 |
海洋学 | 254篇 |
天文学 | 1篇 |
自然地理 | 6篇 |
出版年
2013年 | 4篇 |
2007年 | 3篇 |
2004年 | 3篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 37篇 |
1998年 | 41篇 |
1997年 | 39篇 |
1996年 | 30篇 |
1995年 | 29篇 |
1994年 | 32篇 |
1993年 | 30篇 |
1992年 | 20篇 |
1991年 | 30篇 |
1990年 | 12篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1974年 | 3篇 |
1970年 | 3篇 |
1969年 | 3篇 |
1966年 | 6篇 |
1965年 | 16篇 |
1962年 | 2篇 |
1960年 | 2篇 |
1959年 | 2篇 |
1956年 | 1篇 |
1955年 | 4篇 |
1954年 | 3篇 |
1953年 | 1篇 |
1952年 | 2篇 |
1950年 | 1篇 |
1949年 | 5篇 |
1948年 | 2篇 |
1942年 | 1篇 |
1939年 | 1篇 |
1937年 | 2篇 |
1936年 | 1篇 |
1933年 | 7篇 |
1931年 | 1篇 |
1924年 | 2篇 |
1923年 | 2篇 |
排序方式: 共有438条查询结果,搜索用时 203 毫秒
41.
XU Jiongxin Professor Institute of Geography Chinese Academy of Sciences Beijing China 《国际泥沙研究》1997,(3)
LINTRODUCTIONThetributariesofmiddleYellowRiverarefamousintheworldforthehighestsuspendedsedimentconcentrationandsedimentyield.Forexample,atWenjiachuanstationofKuyeheRiverthemeasuredhighestsuspendedconcentrationis1700kg/m',andthemeanannualsedimentyieldis25000t/(kln'.a).Theformationofhyperconcentratedflowsandtheirinfluenceonerosionprocessesareofgreatimportancenotonlyfromatheoreticalpointofviewbutalsoforpracticalpurposes.Therefore,scientistsfromChinaandallovertheworldhavedrawntheirintensio… 相似文献
42.
43.
Xia Zhenhuan. Professor Dept. Hydraulic Engineering. Tsinshua University. Song Genpei. Lecturer. kept. Hydraulic Engineering. Tsinghua University. Chen Yiping. Assistant. Dept. Hydraulic Engineerins Tsomghua University Wang Gang. Engineer. Research institute of Naval Engineering. PLA 《国际泥沙研究》1990,(1)
1. INTRODUCTIONAs a wide range of size distirbution including usually a certain POrtion of cohesive material is thecommon feature of the sediment constituting hyperconcentrated flows. it is desirable to study the settling properties of mixtures of cohesive and non--cohesjve sediment particles at high concentrations.Past studies on the settling of discrete particles in a suspension of fine cohesjve sediment is scarcein the literature. The Sediment Research Laboratory of Tsinghua Universi… 相似文献
44.
Professor Dr. Hans-Ulrich Roll 《Ocean Dynamics》1990,43(4):207-208
Ohne Zusammenfassung 相似文献
45.
The effects of grain size on the analysis of fabrics by X-ray diffraction using both the fabric camera and the texture goniometer are discussed. Simple calculations show the interdependance between the mean grain diameter and the number of crystals which are measured by each instrument. The effects of both grain size and modal composition of the specimen are illustrated by comparative analyses. Both the fabric camera and texture goniometer are well suited to the analysis of specimens in which the mean grain diameter is between approximately 10 and 100 microns. The texture goniometer is more suitable when the grain size is less than this, while the fabric camera is better suited when the grain size is coarser, especially when the specimen is not monomineralic. 相似文献
46.
Professor Dr. Hellmut Grabert 《International Journal of Earth Sciences》1983,72(2):671-683
The history of the Amazon river system is fixed by two geologic main events: the development of the Atlantic Ocean caused by the break up of the Gondwana continent, and the evolution of the Andean orogenesis. On the other hand the direction of the drainage flow is caused by the Amazon Graben in the subsoil. Also the pleistocene glaciation influenced the Amazon drainage system by lowering the sea level as result of ice fixing in polar regions. 相似文献
47.
A robust algorithm for ellipse-based discrete element modelling of granular materials 总被引:1,自引:0,他引:1
With recent research indicating the importance of the rolling mechanism of deformation in granular systems consisting of perfectly round particles, it has become popular to use ellipse-shaped particles in the Discrete Element Method (DEM) numerical model. Inherent in this technique is the need for accurately computing ellipse to ellipse intersection, in order to properly detect contact formation and compute relative contact velocities. However, the commonly used algorithms for computing ellipse-ellipse intersection are generally poorly conditioned and can be inaccurate. An alternate method for computing ellipse-ellipse intersection is developed and presented which results in a well-conditioned, stable and accurate contact detection method. These modification are incorporated into the general DEM algorithm. 相似文献
48.
YU Wei-Sheng Post-Doctoral Fellow Hydraulic Research Laboratory National Taiwan University Taipei Taiwan China LEE Hong-Yuan Professor Department of Civil Engineering National Taiwan University Taipei Taiwan China 《国际泥沙研究》1993,(2)
I. INTRODUCTIONWhen a sediment--laden flow reaches the backwater zone of a reservoir, the suddenreduction of flow velocity causes sediment particles to settle toward the river bed. Undercertain circumstsnces, it will plunge and form a layer of sediment--water mixture flowingbeneath the water surface. This flowing layer is called the turbidity current. A turbiditycurrent is relatively stable and has important impacts on reservoir sedimentation.In the case of deep reservoirs, due to temper… 相似文献
49.
WANG Guixian WANG Xingkui GUO Jiachao Professor Sediment Research Laboratory Dept. of Hydraulic Engineering Tsinghua University Beijing China. Associate Professor Dept. of Hydraulic Engineering Tsinghua University. Assistant Dept. of Hydraulic Engineering Tsinghua University. 《国际泥沙研究》1993,(3)
I. INTRODUCTIONResistance to flow in alluvial streams is one of the crucial problems in fluvial hydraulics. Despite that large amount of studies have been conducted for centuries, no perfectmethod describing and calculating the resistance to flow in alluvial streams is availablehll now. Investigation on bed forms and resistance properties of light--weight bed materials is even more scarce. USWES (1936) has conducted systematic experiments onlight--weight materials in a flume & m long an… 相似文献
50.