全文获取类型
收费全文 | 14125篇 |
免费 | 2569篇 |
国内免费 | 3398篇 |
专业分类
测绘学 | 1027篇 |
大气科学 | 2990篇 |
地球物理 | 3423篇 |
地质学 | 6733篇 |
海洋学 | 1889篇 |
天文学 | 853篇 |
综合类 | 1491篇 |
自然地理 | 1686篇 |
出版年
2024年 | 49篇 |
2023年 | 184篇 |
2022年 | 521篇 |
2021年 | 618篇 |
2020年 | 525篇 |
2019年 | 632篇 |
2018年 | 691篇 |
2017年 | 652篇 |
2016年 | 797篇 |
2015年 | 633篇 |
2014年 | 865篇 |
2013年 | 845篇 |
2012年 | 787篇 |
2011年 | 791篇 |
2010年 | 900篇 |
2009年 | 813篇 |
2008年 | 756篇 |
2007年 | 737篇 |
2006年 | 599篇 |
2005年 | 563篇 |
2004年 | 410篇 |
2003年 | 410篇 |
2002年 | 372篇 |
2001年 | 458篇 |
2000年 | 479篇 |
1999年 | 692篇 |
1998年 | 566篇 |
1997年 | 523篇 |
1996年 | 527篇 |
1995年 | 448篇 |
1994年 | 403篇 |
1993年 | 370篇 |
1992年 | 296篇 |
1991年 | 234篇 |
1990年 | 174篇 |
1989年 | 142篇 |
1988年 | 152篇 |
1987年 | 83篇 |
1986年 | 77篇 |
1985年 | 56篇 |
1984年 | 37篇 |
1983年 | 27篇 |
1982年 | 45篇 |
1981年 | 37篇 |
1980年 | 22篇 |
1979年 | 22篇 |
1978年 | 8篇 |
1976年 | 12篇 |
1973年 | 5篇 |
1958年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
971.
论辽宁锦西杨家杖子杂岩体的岩浆成因演化及成矿作用 总被引:1,自引:1,他引:1
杨家杖子杂岩体中的二长闪长岩代表一种母岩浆,它是燕山早期库拉板块向欧亚板块下俯冲所产生的,并汇聚上升的安山质岩浆。粗粒似斑状二长花岗岩、细粒似斑状二长花岗岩和(碱长)花岗斑岩是二长闪长岩浆在7km深、弱还原环境、氧逸度为10~(-8)~10~(-10)Pa、1200°~1250℃的岩浆房中经结晶分异作用的派生物。以后,这些岩浆相继上侵,定位于2.5km深处。由这些岩浆岩侵入体所引起的镁夕卡岩、钙夕卡岩和岩浆期后酸性热液淋滤蚀变非常发育。只有来自细粒似斑状二长花岗岩和(碱长)花岗斑岩岩浆、富含Mo的酸性热液沿着裂隙侵入夕卡岩中,在240~330℃时,才形成Mo矿床。此种酸性热液也沿着裂隙侵入细粒似斑状二长花岗岩和(碱长)花岗斑岩中,而形成细脉浸染Mo矿床。因此,杨家杖子Mo矿床属于斑岩-夕卡岩型。 相似文献
972.
973.
本文阐述了环境水利学的定义与内容,提出了环境水利学的五大任务,并根据每一个任务分别说明了在中国的发展情况。最后。提出了如何发展这一学科的一些设想. 相似文献
974.
975.
976.
The axisymmetric finite element technique is used in this paper to analyze the creep effects on pole foundation. Generalized Kelvin model and Bingham model are proposed to simulate the viscoelastic and viscoelastic behavior of soil respectively. Viscoelastic and viscoelastic strain incremental formulas are derived for interface elements and soil elements around piles and the axisymmetric elastic-viscoelastc-viscoplastic finite element program is compiled. Creep effects on the settlement of poles, the building load carried by raft and the distribution of stresses along piles are analyzed. In addition, the behavior of interface between pile and soil are investigated through experiment. 相似文献
977.
Orogenic and Anorogenic Granitoids in the Altay Mountains of Xinjiang and Their Discrimination Criteria 总被引:1,自引:0,他引:1
On the basis of field geological studies of the granotoids in the region, mineralogical, petrological, geochemical(including stable isotope geochemical) and isotopic geochronological investigations were carried out on selected representative granitic bodies of various types. The authors have concluded that, apart from the bodies of the orogenic granitoid series, there also exist intrusions of the anorogenic granitoid series in the region. The intrusives of the two series were formed not only in different ages and tectonic environments, but also were derived from different sources of materials. Moreover, they are associated with different mineralizations, belonging to different minerologenetic series(Cheng et al., 1983). They show distinctly a series of discriminative criteria. The problems under discussion in the present paper are of important theoretical and practical significance in the studies of granites of the orogenic belt, particularly the studies of the genesis and related metallogeny of the granites of the region. 相似文献
978.
979.
Wu Zhishan Lin Junqin 《吉林大学学报(地球科学版)》1989,(4)
本文用加权剩余法导出点源二维地电断面的边界单元法积分方程。通过付氏反变换,可获得三维空间的电位。若干模型上正演计算结果与解析解完全一致。对实测的ρ_s曲线进行了地形攻正及选择法反演拟合,解释结果与实际地质断面符合得很好。 相似文献
980.
Schuman Wu 《Tectonophysics》1989,170(3-4):171-182
In a low-temperature environment, the thin-section scale rock-deformation mode is primarily a function of confining pressure and total strain at geological strain rates. A deformation mode diagram is constructed from published experimental data by plotting the deformation mode on a graph of total strain versus the confining pressure. Four deformation modes are shown on the diagram: extensional fracturing, mesoscopic faulting, incipient faulting, and uniform flow. By determining the total strain and the deformation mode of a naturally deformed sample, the confining pressure and hence the depth at which the rock was deformed can be evaluated. The method is applied to normal faults exposed on the gently dipping southeast limb of the Birmingham anticlinorium in the Red Mountain expressway cut in Birmingham, Alabama. Samples of the Ordovician Chickamauga Limestone within and adjacent to the faults contain brittle structures, including mesoscopic faults and veins, and ductile deformation features including calcite twins, intergranular and transgranular pressure solution, and deformed burrows. During compaction, a vertical shortening of about 45 to 80% in shale is indicated by deformed burrows and relative compaction of shale to burrows, about 6% in limestone by stylolites. The normal faults formed after the Ordovician rocks were consolidated because the faults and associated veins truncate the deformed burrows and stylolites, which truncate the calcite cement. A total strain of 2.0% was caused by mesoscopic faults during normal faulting. A later homogenous deformation, indicated by the calcite twins in veins, cement and fossil fragments, has its major principal shortening strain in the dip direction at a low angle (about 22°) to bedding. The strain magnitude is about 2.6%. By locating the observed data on the deformation mode diagram, it is found that the normal faulting characterized by brittle deformation occurred under low confining pressure (< 18 MPa) at shallow depth (< 800 m), and the homogenous horizontal compression characterized by uniform flow occurred under higher confining pressure (at least 60 MPa) at greater depth (> 2.5 km). 相似文献