全文获取类型
收费全文 | 101611篇 |
免费 | 1473篇 |
国内免费 | 727篇 |
专业分类
测绘学 | 2333篇 |
大气科学 | 6807篇 |
地球物理 | 19551篇 |
地质学 | 36365篇 |
海洋学 | 9312篇 |
天文学 | 23488篇 |
综合类 | 282篇 |
自然地理 | 5673篇 |
出版年
2022年 | 669篇 |
2021年 | 1181篇 |
2020年 | 1302篇 |
2019年 | 1403篇 |
2018年 | 2874篇 |
2017年 | 2666篇 |
2016年 | 3117篇 |
2015年 | 1620篇 |
2014年 | 3002篇 |
2013年 | 5305篇 |
2012年 | 3309篇 |
2011年 | 4305篇 |
2010年 | 3937篇 |
2009年 | 4957篇 |
2008年 | 4387篇 |
2007年 | 4434篇 |
2006年 | 4160篇 |
2005年 | 3037篇 |
2004年 | 2966篇 |
2003年 | 2768篇 |
2002年 | 2729篇 |
2001年 | 2355篇 |
2000年 | 2346篇 |
1999年 | 1901篇 |
1998年 | 1958篇 |
1997年 | 1797篇 |
1996年 | 1519篇 |
1995年 | 1514篇 |
1994年 | 1326篇 |
1993年 | 1228篇 |
1992年 | 1158篇 |
1991年 | 1153篇 |
1990年 | 1160篇 |
1989年 | 1014篇 |
1988年 | 941篇 |
1987年 | 1077篇 |
1986年 | 946篇 |
1985年 | 1198篇 |
1984年 | 1332篇 |
1983年 | 1291篇 |
1982年 | 1197篇 |
1981年 | 1082篇 |
1980年 | 1009篇 |
1979年 | 917篇 |
1978年 | 884篇 |
1977年 | 784篇 |
1976年 | 756篇 |
1975年 | 751篇 |
1974年 | 722篇 |
1973年 | 782篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Fossil diatom algae first found in the Paleogene marine succession (Alugivayam Formation) of the Il’pinskii Peninsula, northeastern Kamchatka are studied, and new data on molluscan assemblages from the same sequences are presented. Some of the diatom forms identified suggest the Oligocene age of their host deposits. This is consistent with earlier inference from benthic groups of marine organisms. 相似文献
102.
103.
Mineralogical alluvial prospecting search for base metals have been carried out from 1968 to 1970 in the Friuli — Venezia Giulia region. The Carnia, a part of this region, was well known from ancient times as an important mining district. Numerous anomalies of the content of some elements and minerals in river sands have been recognized by means of the above mentioned searches. This indicates that important and till now unknown ore concentrations are possible in this region. In fact three new sphalerite and/or galena concentrations and one fluorite concentration in association with As-sulphides have already been discovered during a partial development of these surveys. In the present work the advantages of alluvial prospecting in mining searches are remarked. Moreover method and application of mineralogical alluvial prospecting are described. In the last paragraph the steps which allowed the discovering of the new metal concentrations are reported in detail. The discovered concentrations are shortly analyzed. Strict aim of this note is to indicate the value and scientific importance of the described method.For reasons not within author's control, the results of these researches can be published only to day. But, owing the importance of some recent discoveries, the authors remind that these results have already been discussed at 2nd Int. Symp. on the Mineral Deposits on the Alps Bled, 1971, and at the meeting of Società di Mineralogia e Petrografia Pisa, 1974. 相似文献
104.
The petrology and mineralogy of three lavas from the Lupata Gorge, Mocambique, containing primary euhedral analcime phenocrysts, up to 1.5 cm in diameter, as well as potassium feldspar and nepheline phenocrysts, are described. Electron microprobe analyses of these phases and a whole rock analysis of the blairmorite are given. Reference to published and unpublished experimental work indicates that these rocks must have been generated at water pressures between about 5 and 13 kbars, implying depths of origin of between 20 and 50 km. Very rapid transport to the surface and quenching is implied. It is suggested that these indications of the considerable depth of origin of these rocks, taken together with the absence of associated intermediate and basic rocks, lends credence to the hypothesis of D. K. Bailey that the voluminous associations of salic igneous rocks found in parts of the African continent, unaccompanied by associated basic rocks, are explicable in terms of partial melting, under high water pressures, of the lower part of the crust. 相似文献
105.
William A. Olsson 《Tectonophysics》1974,24(3):277-285
Two fundamentally distinct types of microfractures are present in an experimentally deformed limestone: subaxial microfractures and microfaults. Macroscopic faults are composed of coalesced microfaults and are not related to the subaxial microfractures. A high-temperature mechanical instability occurs at temperatures of 200° C and above when the confining pressure is 600 bars or less. 相似文献
106.
Dr. T. P. Chang 《Aquatic Sciences - Research Across Boundaries》1977,39(2):178-181
Sheath formation was observed in laboratory culturedO. agardhii. The sheath serves as a protective cover against bacteria. Some comments on sheath formation by this alga are given.
Zusammenfassung Scheidenbildung beiOscillatoria agardhii Gomont Im Kulturmaterial vonOscillatoria agardhii Gomont wurde die Bildung von Scheiden beobachtet. Diese dienen als Schutz gegen Bakterien. Es werden weitere überlegungen über die Scheidenbildung bei dieser Alge angestellt.
Résumé Formation de gaines chezOscillatoria agardhii Gomont La formation d’une gaine chezOscillatoria agardhii Gomont fut observée dans une culture. Ces gaines protègent les algues contre les bactéries. Des considérations ultérieures sont faites sur le phénomène des gaines chez cette algue.相似文献
107.
108.
109.
THE VARIABILITY OF MICACEOUS MINERALS IN SEDIMENTARY ROCKS 总被引:1,自引:0,他引:1
110.
R. E. Bevan A.C.I.S. F. Insp. P.C. 《Aquatic Sciences - Research Across Boundaries》1969,31(2):322-334
Ohne Zusammenfassung 相似文献