全文获取类型
收费全文 | 9931篇 |
免费 | 1852篇 |
国内免费 | 4179篇 |
专业分类
测绘学 | 250篇 |
大气科学 | 196篇 |
地球物理 | 1348篇 |
地质学 | 11774篇 |
海洋学 | 395篇 |
天文学 | 926篇 |
综合类 | 513篇 |
自然地理 | 560篇 |
出版年
2024年 | 40篇 |
2023年 | 167篇 |
2022年 | 262篇 |
2021年 | 330篇 |
2020年 | 325篇 |
2019年 | 486篇 |
2018年 | 362篇 |
2017年 | 361篇 |
2016年 | 504篇 |
2015年 | 445篇 |
2014年 | 686篇 |
2013年 | 651篇 |
2012年 | 777篇 |
2011年 | 671篇 |
2010年 | 569篇 |
2009年 | 727篇 |
2008年 | 770篇 |
2007年 | 818篇 |
2006年 | 821篇 |
2005年 | 705篇 |
2004年 | 586篇 |
2003年 | 626篇 |
2002年 | 536篇 |
2001年 | 494篇 |
2000年 | 428篇 |
1999年 | 510篇 |
1998年 | 403篇 |
1997年 | 329篇 |
1996年 | 321篇 |
1995年 | 244篇 |
1994年 | 207篇 |
1993年 | 190篇 |
1992年 | 146篇 |
1991年 | 114篇 |
1990年 | 77篇 |
1989年 | 72篇 |
1988年 | 59篇 |
1987年 | 50篇 |
1986年 | 34篇 |
1985年 | 19篇 |
1984年 | 15篇 |
1983年 | 6篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 3篇 |
1972年 | 1篇 |
1954年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
861.
新疆北天山巴音沟蛇绿岩的地质特征 总被引:3,自引:1,他引:3
巴音沟蛇绿岩虽受强热构造作用肢解,但仍保存有较完整的蛇纹石化超基性岩、状层辉长岩、基性熔岩(下部块状、上部枕状)和放射虫硅质岩的层序组合。岩石化学、地球化学、放射虫等古生物资料表明,它代表一个中石炭世陆缘海盆迅速扩张形成的洋壳和上地幔的残片。其侵位发生在中石炭世未海盆的封闭期间。 相似文献
862.
陈文升 《吉林大学学报(地球科学版)》1988,(1)
本文讨论了用于古地磁测量的超导岩石磁力仪的若干参数,如样品杜瓦管直径、探测线圈匝数、超导屏蔽筒直径等的选择,并计算了超导岩石磁力仪的理论灵敏度。 相似文献
863.
Summary A method of measuring ultrasonic wave properties in rocks during the complete stress-strain process is described. The relevant experimental laboratory study, to reveal the change of the amplitude spectrum parameters with strain (or stress) has been carried out. A preliminary study was conducted on the application of the ultrasonic measurement technique at a belt conveyor roadway of the north wing in Baodian coal mine, Shandong province. A borehole ultrasonic device with dry coupling was developed to provide better coupling and more accurate measurement data in comparison with those of a water coupled situation. Based on the interrelations between the complete stress-strain properties of specimens and their wave properties, the structural properties of surrounding rocks, the range of yield zones, and the change of stresses within the rocks surrounding a roadway which was subjected to mining influence of upper longwall face were analysed. Amplitude spectrum parameters were used to give a better prediction of the physico-mechanical state of the surrounding rocks. 相似文献
864.
Xing Zhang 《Geotechnical and Geological Engineering》1993,11(2):107-124
Summary Based on an extension to a model originally proposed by Zhang (1990), a method for estimating the shear strength of a jointed rock mass containing two joint sets is developed. Compared to the original method in which only a single en-echelon joint set was considered, the new method has the following advantages: (1) it allows a much more realistic joint pattern to be incorporated; (2) the effects of joint connectivity and intersection angle between joint sets on shear strength are included. Use of the new method is demonstrated by application to the calculation of the stability of slopes in jointed rock. The importance of joint connectivity, joint persistence and joint set intersection angle on slope stability, as predicted by the model, is revealed. 相似文献
865.
A suite of marl samples from the evaporitic series of the Mulhouse basin (France; Lower Oligocene) was studied for its biomarker content, in particular its polar constituents. Novel series of 3-carboxyalkyl steranes and 15-oxo triaromatic ketones were identified by synthesis. The 3-carboxyalkyl steranes probably originate from highly polar precursors yet unreported in living organisms. Our data suggest that micro-algae could be the major source of these compounds which seem to be indicators of high algal input rather than characteristic of evaporitic environments. The 15-oxo triaromatic ketones could be oxidation products of triaromatic steroid hydrocarbons formed during diagenesis, although their formation during work-up procedure could not be excluded. 相似文献
866.
米仓山碱性岩中的主要矿物为富铝的(次硅)铝铁质透辉石、钙质角闪石、霞石等,且大量出现霞石,但无或极少有碱性暗色矿物。研究表明:氧逸度低是碱性岩浆不能结晶出碱性暗色矿物的原因。本区这种无碱性暗色矿物的碱性岩是在封闭体系及深成条件下结晶的,而其它地区含有碱性暗色矿物的岩石则是在开放体系中形成的。 相似文献
867.
868.
869.
华南基底变质岩的Sm-Nd同位素及其对花岗岩类物质来源的制约 总被引:33,自引:17,他引:33
华南地区存在两种类型变质基底。Sm-Nd同位素数据的研究结果表明,它们可分别代表华南两种类型元古代地壳端员。华夏地块区副变质岩代表成熟度较高的(早)元古代地壳端员,~(147)Sm/~(144)Nd=0.1198,~(143)Nd/~(144)Nd=0.511822;江南古岛弧区副变质岩代表成熟度较低的(中—晚)元古代地壳端员,~(147)Sm/~(144)Nd=0.1246,~(143)Nd/~(144)Nd=0.512170。根据上述数据得出了华南元古代地壳Sm-Nd同位素演化域,进而对华南不同时代花岗岩类的物质来源作了进一步的讨论。 相似文献
870.