全文获取类型
收费全文 | 41614篇 |
免费 | 7459篇 |
国内免费 | 9118篇 |
专业分类
测绘学 | 3716篇 |
大气科学 | 6197篇 |
地球物理 | 8082篇 |
地质学 | 21967篇 |
海洋学 | 5310篇 |
天文学 | 3697篇 |
综合类 | 2724篇 |
自然地理 | 6498篇 |
出版年
2024年 | 174篇 |
2023年 | 545篇 |
2022年 | 1394篇 |
2021年 | 1601篇 |
2020年 | 1538篇 |
2019年 | 1995篇 |
2018年 | 1407篇 |
2017年 | 1641篇 |
2016年 | 1726篇 |
2015年 | 1886篇 |
2014年 | 2430篇 |
2013年 | 2480篇 |
2012年 | 2527篇 |
2011年 | 2740篇 |
2010年 | 2367篇 |
2009年 | 2877篇 |
2008年 | 2797篇 |
2007年 | 2954篇 |
2006年 | 2852篇 |
2005年 | 2606篇 |
2004年 | 2294篇 |
2003年 | 2136篇 |
2002年 | 1872篇 |
2001年 | 1638篇 |
2000年 | 1634篇 |
1999年 | 1472篇 |
1998年 | 1286篇 |
1997年 | 938篇 |
1996年 | 838篇 |
1995年 | 671篇 |
1994年 | 651篇 |
1993年 | 539篇 |
1992年 | 409篇 |
1991年 | 346篇 |
1990年 | 228篇 |
1989年 | 192篇 |
1988年 | 146篇 |
1987年 | 88篇 |
1986年 | 49篇 |
1985年 | 42篇 |
1984年 | 28篇 |
1983年 | 26篇 |
1982年 | 22篇 |
1981年 | 17篇 |
1980年 | 12篇 |
1979年 | 6篇 |
1978年 | 22篇 |
1977年 | 9篇 |
1976年 | 4篇 |
1954年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
21.
In this work, the factors controlling the formation and preservation of high-pressure mineral assemblages in the metamorphosed orthopyroxene-bearing metagranitoids of the Sandmata Complex, Aravalli-Delhi Mobile Belt (ADMB), northwestern India have been modelled. The rocks range in composition from farsundite through quartz mangerite to opdalite, and with varying K2 O, Ca/(Ca + Na)rock and FeOtot + MgO contents. A two stage metamorphic evolution has been recorded in these rocks.
An early hydration event stabilized biotite with or without epidote at the expense of magmatic orthopyroxene and plagioclase. Subsequent high-pressure granulite facies metamorphism (∼15 kbar, ∼800 °C) of these hydrated rocks produced two rock types with contrasting mineralogy and textures. In the non-migmatitic metagranitoids, spectacular garnet ± K-feldspar ± quartz corona was formed around reacting biotite, plagioclase, quartz and/or pyroxene. In contrast, biotite ± epidote melting produced migmatites, containing porphyroblastic garnet incongruent solids and leucosomes.
Applying NCKFMASHTO T–M (H2 O) and P–T pseudosection modelling techniques, it is demonstrated that the differential response of these magmatic rocks to high-pressure metamorphism is primarily controlled by the scale of initial hydration. Rocks, which were pervasively hydrated, produced garnetiferous migmatites, while for limited hydration, the same metamorphism formed sub-solidus garnet-bearing coronae. Based on the sequence of mineral assemblage evolution and the mineral compositional zoning features in the two metagranitoids, a clockwise metamorphic P–T path is constrained for the high-pressure metamorphic event. The finding has major implications in formulating geodynamic model of crustal amalgamation in the ADMB. 相似文献
An early hydration event stabilized biotite with or without epidote at the expense of magmatic orthopyroxene and plagioclase. Subsequent high-pressure granulite facies metamorphism (∼15 kbar, ∼800 °C) of these hydrated rocks produced two rock types with contrasting mineralogy and textures. In the non-migmatitic metagranitoids, spectacular garnet ± K-feldspar ± quartz corona was formed around reacting biotite, plagioclase, quartz and/or pyroxene. In contrast, biotite ± epidote melting produced migmatites, containing porphyroblastic garnet incongruent solids and leucosomes.
Applying NCKFMASHTO T–M (H
22.
对边界层理论新结果中出现的一类奇异积分方程w(t)=∫1 t(1-s)(λ+λs+s)/w(s)ds+(1-t)∫t 0s/w(s)ds,t∈(0,1)进行讨论,并得出了上述方程在λ∈(-1/2,0)上正解存在性的新结果。 相似文献
23.
E.A. Evstigneeva R.R. de Carvalho A.L. Ribeiro H.V. Capelato 《Astrophysics and Space Science》2003,284(2):487-490
We present the preliminary results of a study of how small stellar systems merge to form larger ones. As we display the families
of galaxies in the μe - Re plane (effective surface brightness versus effective radius) we realize that different morphological types occupy different
loci, evidencing the different physical mechanisms operating in each family. As proposed by Capaccioli et al. (1992) this
diagram is the logical equivalent of the HR diagram for stars. Here we take some initial steps in understanding of how we
can establish the evolutionary tracks, solely due to dynamical processes, in the μe - Re plane, ultimately making a dwarf elliptical to turn into a normal elliptical galaxy.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
24.
25.
26.
乐茂华 《广东海洋大学学报》2004,24(4):47-48
对于正整数a ,设S(a)是Smarandache函数。证明了 :方程S(1·2 ) +S(2·3) +… +S(x(x +1) ) =S(x(x +1) (x +2 ) /3)仅有正整数解x =1。 相似文献
27.
The Tamtsag Basin is located in the extreme eastern portion of the Mongolia. The Basin and its counterpart in China (the Hailar Basin) are united a whole basin on the structural setting. In recent years, the Tamtsag Basin attracts more and more attention with the important exploration discovered in the 19th block by SOCO and in Hailar Basin of China. This paper discusses the exploration potential of Tamtsag Basin from the viewpoint of petroleum geology. 相似文献
28.
陈以良 《广东海洋大学学报》1992,(1)
用比电导法研究两种活性炭自稀水溶液中吸附强电解质硫酸铬和硫酸铜的吸附平衡特性。结果表明,在本文的研究条件下,两种活性炭对硫酸铬和硫酸铜都有吸附作用。同时,活性炭吸附硫酸铜的吸附平衡特性可以用 Freundlich 方程式来描述。研究的结果对固体在溶液中的吸附基础理论以及处理工业废水具有一定的意义。 相似文献
29.
北部湾北部海上油田的开发工作始于50年代,60~70年代作了大量地质工作。改革开放后,油气勘查取得突破性进展。累计发现油气构造6个,含油面积超过40km2,石油地质储量约4亿t,已开发油田2个,揭开我国南方油气资源开发序幕 相似文献
30.
Zhang Chuanling 《地球科学与环境学报》1997,(1)
文中详细地论述了新疆阿尔泰哈巴河一带古生代火山岩的地质、岩石化学、稀土元素地球化学特征。将其分为三个类型,认为火山岩是在陆缘裂陷槽的区域构造背景下发生和演化的。对各类型火山岩岩浆来源,上升模式也做了初步讨论。 相似文献