全文获取类型
收费全文 | 8325篇 |
免费 | 1324篇 |
国内免费 | 1861篇 |
专业分类
测绘学 | 442篇 |
大气科学 | 1514篇 |
地球物理 | 1755篇 |
地质学 | 3229篇 |
海洋学 | 2055篇 |
天文学 | 123篇 |
综合类 | 564篇 |
自然地理 | 1828篇 |
出版年
2024年 | 45篇 |
2023年 | 139篇 |
2022年 | 284篇 |
2021年 | 343篇 |
2020年 | 356篇 |
2019年 | 435篇 |
2018年 | 326篇 |
2017年 | 379篇 |
2016年 | 385篇 |
2015年 | 425篇 |
2014年 | 531篇 |
2013年 | 602篇 |
2012年 | 552篇 |
2011年 | 554篇 |
2010年 | 480篇 |
2009年 | 519篇 |
2008年 | 495篇 |
2007年 | 540篇 |
2006年 | 491篇 |
2005年 | 418篇 |
2004年 | 380篇 |
2003年 | 346篇 |
2002年 | 303篇 |
2001年 | 262篇 |
2000年 | 274篇 |
1999年 | 231篇 |
1998年 | 193篇 |
1997年 | 213篇 |
1996年 | 176篇 |
1995年 | 142篇 |
1994年 | 127篇 |
1993年 | 104篇 |
1992年 | 119篇 |
1991年 | 69篇 |
1990年 | 58篇 |
1989年 | 43篇 |
1988年 | 32篇 |
1987年 | 18篇 |
1986年 | 26篇 |
1985年 | 22篇 |
1984年 | 13篇 |
1983年 | 20篇 |
1982年 | 11篇 |
1981年 | 10篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1978年 | 8篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1972年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
金矿带内不同金矿床氢氧和硫同位素组成,清楚地反映出各金矿产出地质背景的差异,显示出金矿与赋矿围岩有成因联系;δ^18O石英和δ^18O水的变化趋势,反映出金矿空间分布规律及其成矿系列演化。 相似文献
942.
不连续间距对岩体性质具有十分重要的意义。基于无限长测量线得到的岩体不连续间距的负幂指数分布是最重要的一种概率分布密度, 为纠正因用有限长测量线而带来的不连续间距的分布误差, 本文提出了一个封闭形式的修正函数。结果表明, 该法可显著减少不连续间距的相对误差, 从而可以采用较短的测量线来测量岩体的不连续间距。 相似文献
943.
P. H. Gregory 《Pure and Applied Geophysics》1978,116(2-3):309-315
The atmosphere near the ground contains a mixed population of pollen and spores in the 1 to 90 m diameter range. Continuous sampling at Rothamsted Experimental Station at 2 m above ground level indicated concentrations averaging 12,000 m–3 over 5 summer months, but 1 million m–3 can occur for short periods. Concentrations change rapidly with locality, season, time of day or night and weather. Normally concentration in the troposphere decreases logarithmically with height. The occurrence of long distance transport of pollen and spores by wind is demonstrated by sampling from aircraft, and supported by much circumstantial evidence. Possible effects of this air spora on the atmosphere may be sought in alterations to: opacity, ionization, condensation nuclei, and sinks for minor gases. 相似文献
944.
Using the data collected during the International Indian Ocean Expedition, maps showing the distribution of depth, acceleration
potential, salinity and oxyty were prepared for the northeast monsoon for the four potential thermosteric anomaly surfaces:
160, 120, 80 and 60 cl/t. Zonal components of current along 84°E were computed from the geopotential dynamic heights. From
such an analysis, it became clear that low-salinity water from the Pacific intrudes into the western Indian Ocean through
the Banda and Timor seas in the upper layers above 100 cl/t surface, while the North Indian Ocean Water penetrates towards
the Eastern Archipelago below 100 cl/t surface. The South Equatorial Countercurrent and the Tropical Countercurrent are well
depicted on the vertical section of zonal components as well as on the distribution of acceleration potential. 相似文献
945.
The lognormal approach to predicting local distributions of selective mining unit grades 总被引:1,自引:0,他引:1
A. G. Journel 《Mathematical Geology》1980,12(4):285-303
946.
947.
涡度规则分布与非规则分布的转换 总被引:2,自引:2,他引:0
用一个β平面准地转正压模式积分12个模式日,研究涡旋相互作用问题。初始场上有一个台风涡旋和一对涡旋偶极子,它们的等值线均为光滑、规则的分布。规则分布的涡旋之间的相互作用,可以激发出一个非规则的貌似混乱的涡度分布区域。随着时间的演化,在这个非规则分布的区域,一个相对有序的反气旋环流又逐渐显示出来。 相似文献
948.
There were 102 meso-α-scale convective systems(MαCSs)generated over China and theneighboring sea during June—August 1995.Those MαCSs were concentrated in three major areas:the west of South China,Sichuan Basin,and the middle and lower reaches of the Changjiang andthe Huanghe River Basin.Six cases of MαCS in different regions are given to show the variety ofthe MαCS genesis and development by the distributions of their cold-cloud-shield black bodytemperature. 相似文献
949.
Ammonite faunas consisting of Neolobites vibrayeanus (d'Orbigny), Calycoceras (Calycoceras) naviculare (Mantell), C. (Lotzeites(?)) sp., Pseudocalycoceras lattense Thomel, Metoicoceras geslinianum (d'Orbigny) and Euomphaloceras septemseriatum (Cragin) from Saumur, within the type area of the Turonian stage, are described from the collections of the Château de Saumur. They allow the recognition of two Upper Cenomanian horizons at Saumur, the one equivalent to the Sciponoceras gracile/Metoicoceras geslinianum Zone as developed in the Sables à Catopygus obtusus/Sables de Bousse of the Cenomanian stratotype; the other, older assemblage equates with the Calycoceras naviculare/Eucalycoceras pentagonum Zone fauna known from the Marnes à Ostracées of the type Cenomanian. From lithological comparisons it is suggested that this area is the source of the types of both Metoicoceras geslinianum and Neolobites vibrayeanus, which are redescribed. 相似文献
950.
SummarySome Foundation Stability Problems of the Railway Bridge over the Mala Rijeka The authors presented an outlay of problems occurring in estimating the stability of rocky slopes loaded by large vertical forces. General attitudes, kept by the authors during the stability analysis for an actual case — foundation of piers No. 3 and 4 of the railway bridge across the Mala Rijeka, are also presented. The results of calculation as well as the advantages of the approach applied are outlined in the paper. Finally, general conclusions are drawn regarding the method to be kept in solving the stability of slopes loaded by large artificial loading.With 7 Figures 相似文献