全文获取类型
收费全文 | 30559篇 |
免费 | 689篇 |
国内免费 | 349篇 |
专业分类
测绘学 | 793篇 |
大气科学 | 2453篇 |
地球物理 | 6732篇 |
地质学 | 10692篇 |
海洋学 | 2542篇 |
天文学 | 6073篇 |
综合类 | 60篇 |
自然地理 | 2252篇 |
出版年
2020年 | 194篇 |
2019年 | 210篇 |
2018年 | 411篇 |
2017年 | 379篇 |
2016年 | 560篇 |
2015年 | 439篇 |
2014年 | 609篇 |
2013年 | 1486篇 |
2012年 | 727篇 |
2011年 | 1022篇 |
2010年 | 828篇 |
2009年 | 1192篇 |
2008年 | 1094篇 |
2007年 | 1033篇 |
2006年 | 1029篇 |
2005年 | 893篇 |
2004年 | 924篇 |
2003年 | 885篇 |
2002年 | 884篇 |
2001年 | 711篇 |
2000年 | 728篇 |
1999年 | 678篇 |
1998年 | 651篇 |
1997年 | 647篇 |
1996年 | 541篇 |
1995年 | 535篇 |
1994年 | 507篇 |
1993年 | 473篇 |
1992年 | 444篇 |
1991年 | 391篇 |
1990年 | 442篇 |
1989年 | 355篇 |
1988年 | 396篇 |
1987年 | 437篇 |
1986年 | 364篇 |
1985年 | 546篇 |
1984年 | 597篇 |
1983年 | 596篇 |
1982年 | 483篇 |
1981年 | 489篇 |
1980年 | 490篇 |
1979年 | 433篇 |
1978年 | 434篇 |
1977年 | 399篇 |
1976年 | 433篇 |
1975年 | 383篇 |
1974年 | 429篇 |
1973年 | 409篇 |
1972年 | 255篇 |
1971年 | 200篇 |
排序方式: 共有10000条查询结果,搜索用时 7 毫秒
171.
H. W. van der Marel 《Contributions to Mineralogy and Petrology》1964,9(5):462-480
A scheme is presented for the identification and classification of chlorite and related minerals in sediments which is mainly based on X-ray characteristics of the orginal sample and the sample heated at 350°C and treated with K+ and with glycerol. Examples are given. It is emphasized that additional data about clay mineral genesis, electron microscopy, infrared spectroscopy and chemical analyses are needed for the ordening of a certain mineral in the proposed scheme. Many names of minerals so far found to occur in the clay separate of sediments proved to be synonymous (52 of a total of 88) and thus should be abandoned. They only give confusion and needlessly increase the many difficulties which already exist in the identification, classification and quantitative determination of this complicated group of minerals of about 36 well defined specimens which may be found in sediments. 相似文献
172.
G. R. Huguenin A. E. Lilley W. H. McDonough M. D. Papagiannis 《Planetary and Space Science》1964,12(12):1157-1167
Radio noise observations at frequencies of 0·700 Mc and 2·200 Mc were made at altitudes between 3000 and 11,000 km from a Blue Scout Jr. high-altitude rocket probe on 30 July 1963. A steady background flux of (7·5−3+6) × 10−19 W m−2)(c/s)−1 at 0·700 Mc and (1·8+1.0−0.5 × 10−19 W m−2 (c/s)−1 at 2·200 Mc was observed. Assuming a galactic origin of the observed fluxes at both frequencies, the averaged sky brightnesses are b(0·700 Mc) = (6−3+5) × 10−20 W m−2 (c/s)−1 sr−1b(2·200 Mc) = (1.4+1.0−0.5 × 10−20 W m−2 (c/s)−1 sr−1 The observed brightness at 2·200 Mc is in reasonable agreement with the results of other observers. The apparent brightness at 0·700 Mc is, however, greater than was expected from previous observations. An alternative source of the 0·700 Mc flux in the terrestrial exosphere, as well as characteristics of several noise bursts observed during the flight, is briefly discussed. 相似文献
173.
174.
Some glaucophane schists are chemically indistinguishable fromgreenschists and epidote amphibolites. Provided all three rocktypes represent equilibrium assemblages, they must have formedunder differing physical conditions. The mineralogy of suchglaucophane schists taken in conjunction with experimental evidencesuggests that these rocks formed at low temperatures and atrelatively elevated pressures. The relatively high-pressure,low-temperature phases lawsonite, jadeitic pyroxene, and metamorphicaragonite are diagnostic of physical conditions attending thismetamorphism. Differential stress may aid in the attainmentof the appropriate mean pressure necessary for the productionof these phases. Graphic analysis and approximated thermodynamic calculationsindicate that relatively elevated pressures, or relatively lowtemperatures, or both, promote the formation of glaucophanein rocks of a wide range of bulk compositions while restrictingthe compositional range of albite-bearing rocks. It is concludedthat the coexistence of glaucophane with carbonate, calcium-aluminumsilicate or paragonite results from such physical conditions,and it is on the basis of these associations or, equally well,the presence of lawsonite, jadeitic pyroxene, or metamorphicaragonite that the blueschist facies should be defined. High pressures are not required for the production of glaucophaneitself. It is stable under physical conditions present in thegreenschist and epidote amphibolite facies in rocks deficientin CaO and rich in Na2O and MgO relative to A12O3. Such bulkcompositions might result from exchange of material betweenserpentinite and albite-bearing country rocks, and could accountfor glaucophane aureoles around, and inclusions of glaucophanerock within, some serpentinites. 相似文献
175.
F. Steinhauser W. Mörikofer K. Cehak W. Müller 《Theoretical and Applied Climatology》1965,13(4):558-568
Ohne Zusammenfassung 相似文献
176.
F. Steinhauser W. Mörikofer J. Drimmel Peter Steinhauser 《Meteorology and Atmospheric Physics》1965,15(2):251-264
Ohne Zusammenfassung 相似文献
177.
178.
179.
180.