全文获取类型
收费全文 | 11868篇 |
免费 | 2973篇 |
国内免费 | 3618篇 |
专业分类
测绘学 | 1820篇 |
大气科学 | 1743篇 |
地球物理 | 2544篇 |
地质学 | 7313篇 |
海洋学 | 1874篇 |
天文学 | 230篇 |
综合类 | 973篇 |
自然地理 | 1962篇 |
出版年
2024年 | 98篇 |
2023年 | 274篇 |
2022年 | 703篇 |
2021年 | 883篇 |
2020年 | 688篇 |
2019年 | 806篇 |
2018年 | 737篇 |
2017年 | 671篇 |
2016年 | 677篇 |
2015年 | 762篇 |
2014年 | 799篇 |
2013年 | 950篇 |
2012年 | 952篇 |
2011年 | 1004篇 |
2010年 | 977篇 |
2009年 | 892篇 |
2008年 | 904篇 |
2007年 | 886篇 |
2006年 | 785篇 |
2005年 | 682篇 |
2004年 | 507篇 |
2003年 | 453篇 |
2002年 | 565篇 |
2001年 | 462篇 |
2000年 | 372篇 |
1999年 | 218篇 |
1998年 | 97篇 |
1997年 | 107篇 |
1996年 | 112篇 |
1995年 | 76篇 |
1994年 | 70篇 |
1993年 | 54篇 |
1992年 | 39篇 |
1991年 | 26篇 |
1990年 | 30篇 |
1989年 | 21篇 |
1988年 | 23篇 |
1987年 | 18篇 |
1986年 | 8篇 |
1985年 | 12篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1975年 | 3篇 |
1965年 | 4篇 |
1964年 | 2篇 |
1954年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
991.
Geometrical textures of faults,evolution of physical field and instability characteristics 总被引:9,自引:0,他引:9
Geometricaltexturesoffaults,evolutionofphysicalfieldandinstabilitycharacteristicsJINMA(马瑾),SHENG-LIMA(马胜利),LI-QIANGLIU(刘力强),Z... 相似文献
992.
993.
滑坡灾害预测研究概况 总被引:2,自引:0,他引:2
本文以文献资料为依据,阐述了滑坡灾害的严重性、人类活动与滑坡灾害的伴生性,并从减轻灾害的角度,分析了滑坡灾害空间预测和长时间预测的重要意义及其研究趋势。 相似文献
994.
A lot of researches onb value have been made in seismology. Since the 1960’s Mogi, Scholz and others have studied AE of rock specimens in laboratory
and discovered that it is related to natural earthquakes. All former researchers used integral specimens to studyb value in the laboratory. However a major earthquake is usually related to a existing seismic-fault in that area. For this
reason, a series of fracture experiments with rock and glass specimens having pre-existing crack or notch is performed in
order to examine the effect of preexisting crack tob value. The experimental results show that theb value begins to decrease as soon as the initiation of the crack and finally drop to a very low value when the specimen breaks
unstably. Based on these, a brief discussion on the possible mechanism ofb value change for natural earthquakes is given.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,9, 393–400, 1987.
Projects sponsored by the Chinese Joint Seismological Science Foundation. 相似文献
995.
瞬变电磁测深法的研究深度 总被引:2,自引:0,他引:2
殷长春 《吉林大学学报(地球科学版)》1992,(1)
研究发现,瞬变测深法研究深度除了与采样时间(采样间隔,起始和终止采样时间等)有关外,还与信号源强度、大地电导率、系统噪音水平以及仪器观测精度等因素有关,文中对研究深度与这些量之间的关系作了数学描述。 相似文献
996.
通过对柴达木盆地北缘西段重点探井的岩心观测、重矿物分析、测井数据及地震资料的分析,研究了冷湖构造带古近系沉积体系及演化特征和不同时期沉积微相及砂体的展布规律.结果认为,冷湖构造带古近系主要发育冲积扇-辫状河-辫状河三角洲-湖泊沉积体系,物源来自北东方向的小赛什腾山和赛什腾山附近.古近系路乐河组(E1+2)沉积期,主要发育辫状河以及辫状河三角洲平原沉积,仅在靠近山前发育少量冲积扇沉积;至下干柴沟组(E3)沉积时期,主要发育辫状河、辫状河三角洲平原、辫状河三角洲前缘及滨-浅湖沉积.古近纪时期冷湖构造带表现为一次较大规模的水进过程,纵向沉积继承性明显,很好地记录了这一沉积演化过程.这一沉积体系及演化过程有利于粗碎屑和细碎屑交互沉积,形成较好的储盖组合,为柴达木盆地冷湖构造带下一步的油气勘探提供了可靠的地质依据. 相似文献
997.
An improvement on the new method of Intervalhalving-Scanning (INS) proposed by the senior author for derivation of thermodynamic properties of minerals from reversed experiment (REP) data has been made in the present work. The treatment of the REP data of 6 reactions in the system MgO-SiO_2-H_2O and the derivation of △_(?)H(?) (298. 15K) for minerals Talc,Forsterite and Anthophyllite are chosen as an example for demonstration of the application of the method.INS is quite different from all the methods for the derivation in the literature and throughout based on thermodynamic principles and equations so that its thermodynamical validity is thoroughgoing. 相似文献
998.
BIOCHEMICAL CHANGES DURING DEVELOPMENT OF EGGS AND YOLK-SAC LARVAE OF HERRING AND PLAICE 总被引:2,自引:1,他引:2
Changes in quantities of water, sodium, potassium, lipid and protein were compared in developing eggs and yolk-sac larvae of herring dupes harengus L., a species with demersal eggs, and plaice Pleuroncctcs platessa L., a species with pelagic eggs. The principal difference between the two species was the occurrence in herring, but not in plaice of considerable increases in water content and in one or both of the above ions at three distinct stages: at fertilization,during the middle stage of egg development, and in the days immediately after hatching. Newly hatched larvae of the two species differed greatly in water content because of the difference in mass and water content of the yolk, not in the water content of the rest of the body. In herring, there were increases in sodium and potassium which coincided broadly with the increase in water content. These differences are related to the gradual acquisition of buoyancy by herring during this period, comparable with the buoyancy conferred on plaice eggs a 相似文献
999.
1000.