全文获取类型
收费全文 | 31035篇 |
免费 | 367篇 |
国内免费 | 215篇 |
专业分类
测绘学 | 534篇 |
大气科学 | 2883篇 |
地球物理 | 6388篇 |
地质学 | 11886篇 |
海洋学 | 2128篇 |
天文学 | 6028篇 |
综合类 | 50篇 |
自然地理 | 1720篇 |
出版年
2019年 | 209篇 |
2018年 | 498篇 |
2017年 | 462篇 |
2016年 | 568篇 |
2015年 | 438篇 |
2014年 | 607篇 |
2013年 | 1263篇 |
2012年 | 743篇 |
2011年 | 1020篇 |
2010年 | 880篇 |
2009年 | 1229篇 |
2008年 | 1056篇 |
2007年 | 1060篇 |
2006年 | 999篇 |
2005年 | 835篇 |
2004年 | 850篇 |
2003年 | 804篇 |
2002年 | 747篇 |
2001年 | 693篇 |
2000年 | 647篇 |
1999年 | 583篇 |
1998年 | 599篇 |
1997年 | 608篇 |
1996年 | 509篇 |
1995年 | 461篇 |
1994年 | 416篇 |
1993年 | 391篇 |
1992年 | 450篇 |
1991年 | 420篇 |
1990年 | 437篇 |
1989年 | 403篇 |
1988年 | 362篇 |
1987年 | 471篇 |
1986年 | 374篇 |
1985年 | 453篇 |
1984年 | 521篇 |
1983年 | 527篇 |
1982年 | 510篇 |
1981年 | 481篇 |
1980年 | 454篇 |
1979年 | 456篇 |
1978年 | 453篇 |
1977年 | 401篇 |
1976年 | 377篇 |
1975年 | 404篇 |
1974年 | 352篇 |
1973年 | 375篇 |
1972年 | 279篇 |
1971年 | 282篇 |
1970年 | 254篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
Gerd Rantitsch Reinhard F. Sachsenhofer Christian Hasenhüttl Barbara Russegger Thomas Rainer 《Tectonophysics》2005,411(1-4):57-72
Following Early Cretaceous nappe stacking, the Eastern Alps were affected by late-orogenic extension during the Late Cretaceous. In the eastern segment of this range, a Late Cretaceous detachment separates a very low- to low-grade metamorphic cover (Graz Paleozoic Nappe Complex, GPNC) above a low- to high-grade metamorphic basement. Synchronously, the Kainach Gosau Basin (KGB) collapsed and subsided on top of the section.Metamorphism of organic material within this section has been investigated using vitrinite reflectance data and Raman spectra of extracted carbonaceous material. In the southern part of the GPNC, vitrinite reflectance indicates a decrease in organic maturity towards the stratigraphic youngest unit. The remaining part of the GPNC is characterized by an aureole of elevated vitrinite reflectance values and Raman R2 ratios that parallels the margins of the GPNC. Vitrinite reflectance in the KGB shows a steep coalification gradient and increases significantly towards the western basin margin. The observed stratigraphic trend in the southern GPNC is a result of deep Paleozoic to Early Cretaceous burial. This maturity pattern was overprinted along the margins by advective heat and convective fluids during Late Cretaceous to Paleogene exhumation of basement rocks.During shearing, the fault zone was heated up to ca. 500 °C. This overprint is explained by a two-dimensional thermal model with a ramp-flat fault geometry and a slip rate of 1 to 1.5 cm/year during 5 Ma fault movement. The collapse basin above the detachment subsided in a thermal regime which was characterized by relaxing isotherms. 相似文献
103.
104.
Doklady Earth Sciences - The results of isotope U–Pb dating of zircons from lherzolite and vein olivine orthopyroxenite composing the Roseta ultramafic massif are presented. The zircons... 相似文献
105.
Viking images of Martian craters with rampart-bordered ejecta deposits reveal distinct impact ejecta morphology when compared to that associated with similar-sized craters on the Moon and Mercury. Topographic control of distribution, lobate and terraced margins, cross-cutting relationships, and multiple stratigraphic units are evidence for ejecta emplacement by surface flowage. It is suggested that target water explosively vaporized during impact alters initial ballistic trajectories of ejecta and produces surging flow emplacement. The dispersal of particulates during a series of controlled steam explosions generated by interaction of a thermite melt with water has been experimentally modeled. Preliminary results indicate that the mass ratio of water to melt and confining pressure control the degree of melt fragmentation (ejecta particle size) and the energy and mode of melt-ejecta dispersal. Study of terrestrial, lobate, volcanic ejecta produced by steam-blast explosions reveals that particle size and vapor to clast volume ratio are primary parameters characterizing the emplacement mechanism and deposit morphology. Martian crater ramparts are formed when ejecta surges lose fluidizing vapors and transported particles are deposited en masse. This deposition results from flow yield strength increasing above shear stress due to interparticle friction. 相似文献
106.
107.
R. G. Bill Jr. E. Chen R. A. Sutherland J. F. Bartholic 《Boundary-Layer Meteorology》1979,16(1):23-33
A steady-state, two-dimensional numerical model is used to simulate air temperatures and humidity downwind of a lake at night. Thermal effects of the lake were modelled for the case of moderate and low surface winds under the cold-air advective conditions that occur following the passage of a cold front. Surface temperatures were found to be in good agreement with observations. A comparison of model results with thermal imagery indicated the model successfully predicts the downwind distance for which thermal effects due to the lake are significant. 相似文献
108.
Ground-based thermal emission measurements of the zenith sky have been made at Peterborough, Ontario since January 1993. In this paper, the measurement of the 6 band of atmospheric CFC-12, an important greenhouse gas, is presented for a cold, clear day in January 1994. A spectrum of the non-CFC-12 emission features has been simulated using the FASCD3P radiation code and measured radiosonde profiles of temperature, pressure and humidity. This has enabled a satisfactory subtraction of the interfering emission features from the CFC-12 emission spectrum. A comparison of the observed and simulated 6-bands of CFC-12 shows good agreement at all frequencies of emission. From these spectra the total downward greenhouse radiative flux from the CFC-12 6 emission based for a very cold day has been estimated to be 0.27 W m−2±10%. 相似文献
109.
110.
F. Brngen 《Astronomische Nachrichten》1980,301(6):305-310
Für 95 sehr schwache blaue Objekte in der Nähe des Zentrums des Virgo-Galaxienhaufens werden Auffindungskarten, Koordinaten, Schätzungen des (U – B)-Farbenindexes und grobe B-Helligkeiten mitgeteilt. Die Objekte wurden durch Blinken einer Tautenburger U- und B-Schmidtplatte gefunden. 相似文献