全文获取类型
收费全文 | 86篇 |
免费 | 3篇 |
国内免费 | 5篇 |
专业分类
大气科学 | 4篇 |
地球物理 | 11篇 |
地质学 | 50篇 |
海洋学 | 6篇 |
天文学 | 3篇 |
自然地理 | 20篇 |
出版年
2017年 | 2篇 |
2016年 | 1篇 |
2014年 | 1篇 |
2013年 | 6篇 |
2012年 | 5篇 |
2010年 | 3篇 |
2009年 | 1篇 |
2008年 | 2篇 |
2006年 | 2篇 |
2005年 | 1篇 |
2004年 | 1篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 10篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 4篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1979年 | 4篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1972年 | 3篇 |
1971年 | 2篇 |
1969年 | 1篇 |
1968年 | 3篇 |
1967年 | 1篇 |
1966年 | 3篇 |
1965年 | 1篇 |
1963年 | 1篇 |
1962年 | 2篇 |
排序方式: 共有94条查询结果,搜索用时 328 毫秒
71.
72.
73.
The Rio Dell Formation (Pleistocene and Pliocene), exposed south of Eureka, California, is a prograded sequence of basinal turbidites overlain by basin slope and shelf deposits. The slope deposits studied in the Centerville Beach section accumulated in a steadily shallowing environment delineated by analysis of palaeobathymetrically significant benthonic foraminiferal biofacies in turn suggesting deposition at depths of 1000–100 m. Lower slope deposits interfinger with basinal turbidites derived from the Eel River delta to the north. Slumped blocks of silty mudstone, and associated silt and mud beds, are common. The middle slope deposits are mudstones; coarser sediments bypassed this zone. Mudstones and muddy siltstones alternate on the upper slope. Shallow depressions, probably slump scars, that have been rapidly filled by upper slope sediment are common. The transition to shelf deposits is marked by an increase in sediment grain size, in the degree of oxidation, and in the abundance of megafossils. High percentages of benthonic foraminifera displaced from shelf depths indicate that resedimentation processes are most important on the upper slope. 相似文献
74.
75.
O18/O16 and C12/C13 ratios have been determined for carbonaterocks and coexisting minerals from two contact metamorphic aureolesat Birch Creek, California and Marble Canyon, Texas. The peliticmetasediments and granitic intrusions of the Birth Creek localitywere also analyzed for their O18/16 and D/H ratios. Oxygen andcarbon isotope fractionations in coexisting dolomite and calciteare interrelated but show no obvious correlation with sampledistance from the intrusive contact. Small-scale oxygen isotopicexchange effects between rock units are observed within a fewfeet of the intrusive-country rock contacts and the marble-schistcontacts at Birch Creek. Oxygen isotopic temperatures obtainedfrom quartzbiotite fractionations in the biotite schistsof Birch Creek show a systematic decrease with increasing distanceaway from the intrusive contact; the isotopic contact temperatureis calculated to be 53545°C. Low O18/16 and C13/12ratiosof the contact metamorphic marbles generally correlate wellwith presence of calc-silicate minerals, indicating that theCO2 liberated during metamorphic decarbonation reactions isenriched in both O18and C12 relative to the carbonates. Materialbalance calculations indicate that the liberated CO2 is about5 per mille richer in O18 and about 6 per mille richer in C13than coexisting calcite. 相似文献
76.
Abstract. When simultaneously presented with equal numbers of four sizes of clumped Mytilus californianus (20, 35, 55 and 85 mm shell length), Pisaster ochraceus (arm length of 70-110mm R) showed a preference for the medium sizes (35 and 55mm length). Prey-size preference was positively correlated with predator size. Mean prey-digestion times (insertion of the stomach, opening of the valves and digestive period) decreased significantly following fiiing of an artificial gape between the valves of mussels. When presented with different sizes of clumped filed mussels, starfish still chose medium mussels, indicating that stomach insertion, valve opening, and digestion rate may not be important constraints determining size selective predation. Measurements of the force required to dislodge mussels from the substratum and conspecifics showed an increasing exponential relationship with mussel size. Size selective feeding may be an energy maximizing and time minimizing strategy, where energy gained from choosing larger mussels is balanced against disproportionately increased costs in energy and time of removing large mussels from the substratum. 相似文献
77.
ROGER F. AUCH DARRELL E. NAPTON STEVEN KAMBLY THOMAS R. MORELAND JR. KRISTI L. SAYLER 《Geographical review》2012,102(1):53-75
Driving forces facilitate or inhibit land‐use / land‐cover change. Human driving forces include political, economic, cultural, and social attributes that often change across time and space. Remotely sensed imagery provides regional land‐change data for the Northern Piedmont, an ecoregion of the United States that continued to urbanize after 1970 through conversion of agricultural and forest land covers to developed uses. Eight major driving forces facilitated most of the land conversion; other drivers inhibited or slowed change. A synergistic web of drivers may be more important in understanding land change than individual drivers by themselves. 相似文献
78.
Under winter conditions, stemflow drainage in forested ecosystems is often assumed to be a negligible component of the hydrological cycle. This paper reports on mid-winter stemflow drainage from the broadleaved deciduous tree species Populus grandidentata. Stemflow volumes from this species at air temperatures of < 0°C were found to be comparable to rainfall-generated stemflow during summer. Over the three-month period January–March 1993, stemflow ranged from 5.4 to 9.9% of the incident gross precipitation. Expressed as depth equivalents per unit trunk basal area, these stemflow inputs ranged from 1.8 to 4.9 m. These concentrated mid-winter inputs of liquid water to the bases of canopy trees were attributable to: (1) snow interception by the leafless woody frame of each tree; (2) snow retention by glazed ice precipitation associated with the snowfall event; (3) increased temperature at the bark/snow interface caused by the low albedo of the bark tissue; and (4) convergence of snowmelt drainage from steeply inclined upthrust primary branches. The hydrological and ecological significance of liquid water inputs to the forest floor under sub-zero conditions are discussed. © 1997 by John Wiley & Sons Ltd. 相似文献
79.
对石墨涂样检测 Cs2 BO2 离子条件下甘露醇对硼同位素测定的影响进行了研究 ,结果表明在甘露醇存在下 11B/ 10 B比值明显高于只有石墨存在时的比值。硼 -甘露醇络合物的形成可能改变了 Cs2 BO2 -石墨方法的电离和蒸发条件。 相似文献
80.
Abstract Field, geochemical and geophysical evidence show that the southern Zambales Ophiolite Complex attained its present-day configuration through the juxtapositioning of an arc terrane (San Antonio massif) to a back-arc crust (Cabangan massif). The San Antonio massif manifests island arc-related characteristics (i.e. spinel XCr [Cr/(Cr + Al)] >0.60; mostly plagioclase An92–95; pyroxene crystallizing ahead of plagioclase; orthopyroxene as an early, major crystallizing phase) which cannot be directly parental to the Cabangan massif transitional mid-ocean ridge basalt to island arc tholeiitic volcanic carapace. The two massifs are believed to be separated by a left-lateral strike–slip fault, the Subic Bay Fault Zone. Apart from the presence of highly sheared, allochthonous outcrops, the Subic Bay Fault Zone is generally defined by northwest–southeast trending magnetic and bouguer anomalies. The San Antonio massif was translated southward from the northern part of the Zambales Ophiolite Complex through the Subic Bay Fault Zone. This resulted into its suturing with the Cabangan massif and could have led to the formation of the present-day Subic Bay. 相似文献