全文获取类型
收费全文 | 9562篇 |
免费 | 1483篇 |
国内免费 | 2620篇 |
专业分类
测绘学 | 643篇 |
大气科学 | 568篇 |
地球物理 | 2030篇 |
地质学 | 5840篇 |
海洋学 | 1069篇 |
天文学 | 1654篇 |
综合类 | 608篇 |
自然地理 | 1253篇 |
出版年
2024年 | 31篇 |
2023年 | 116篇 |
2022年 | 264篇 |
2021年 | 242篇 |
2020年 | 302篇 |
2019年 | 394篇 |
2018年 | 322篇 |
2017年 | 325篇 |
2016年 | 374篇 |
2015年 | 392篇 |
2014年 | 498篇 |
2013年 | 629篇 |
2012年 | 512篇 |
2011年 | 542篇 |
2010年 | 451篇 |
2009年 | 682篇 |
2008年 | 713篇 |
2007年 | 773篇 |
2006年 | 730篇 |
2005年 | 612篇 |
2004年 | 589篇 |
2003年 | 577篇 |
2002年 | 472篇 |
2001年 | 457篇 |
2000年 | 410篇 |
1999年 | 386篇 |
1998年 | 346篇 |
1997年 | 234篇 |
1996年 | 211篇 |
1995年 | 196篇 |
1994年 | 185篇 |
1993年 | 161篇 |
1992年 | 111篇 |
1991年 | 78篇 |
1990年 | 90篇 |
1989年 | 64篇 |
1988年 | 49篇 |
1987年 | 48篇 |
1986年 | 27篇 |
1985年 | 18篇 |
1984年 | 15篇 |
1983年 | 5篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1979年 | 3篇 |
1977年 | 7篇 |
1976年 | 4篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1954年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
311.
Water is the most active component in all geological systems.It has an important effect on the physical properties of minerals and melts.It also plays a key role in the evolution of the Earth.Accurate thermodynamics data on water are currently confined to pressures below 1.0GPa and temperatures below 900℃.Presented in this paper are new data available on the P-T properties of water at pressures up to 5.0GPa,develoged from differential thermal analysis and ultrasonic wave amplitude analysis.It has been found that there may exist another ternary point at 3.0GPa and that ultrasonic wave amplitude change of ice-water transition shows two inflection points above 2.0GPa, consistent with the two peaks of differential thermal curves above 2.0GPa .It may be a new phenomenon which needs further study. 相似文献
312.
Porewater pressure increases in soil and rock from underground chemical and nuclear explosions 总被引:3,自引:0,他引:3
Wayne A. Charlie George E. Veyera Deanna S. Durnford Donald O. Doehring 《Engineering Geology》1996,43(4):225-236
A review and analysis of chemical and nuclear explosive-induced porewater pressure increases and induced rise in groundwater table elevations (groundwater mounding) is presented. Our analysis indicates that residual pore pressure increases and groundwater mounding can be induced by underground chemical and nuclear explosions to scaled distances of 879 m/(kt)1/3. This relationship is linear over seven orders of magnitude of explosive energy ranging from a 0.01 kg chemical explosion to a 100 kt nuclear explosion and is valid for a wide variety of saturated geological profiles. Underground chemical explosions, and probably underground nuclear explosions have the potential to induce liquefaction of water-saturated soils to scaled distances of about 260 m/(kt)1/3. 相似文献
313.
314.
315.
Application of an optimum design technique for determining the coefficient of consolidation by using piezocone test data 总被引:4,自引:0,他引:4
For normally consolidated clay, several researchers have developed a number of theoretical time factors to determine the coefficient of consolidation from piezocone test results. However, depending on assumptions and analytical techniques, it could vary considerably, even for a specific degree of consolidation. In this paper a method is proposed to determine a consistent coefficient of consolidation by applying the concept of an optimum design technique over all ranges of the degree of consolidation. Initial excess pore pressure distribution is assumed to be capable of being obtained by the successive spherical cavity expansion theory. The dissipation of pore pressure is simulated by means of a two-dimensional linear-uncoupled axi-symmetric consolidation analysis. The minimization of differences between measured and predicted excess pore pressure was carried out by the BFGS unconstrained optimum design algorithm with a one-dimensional golden section search technique. By analyzing numerical examples and in-situ test results, it was found that the adopted optimum design technique gives consistent and convergent results. 相似文献
316.
317.
Study of the liquefaction resistance of a saturated sand reinforced with Geosynthetics 总被引:1,自引:0,他引:1
This article presents various tests using a cyclic triaxial instrument, on samples of saturated Hostun RF sand, reinforced with circular sheets of geosynthetic material. Tests performed with different types of geosynthetics of different compressibility, rigidity and roughness characteristics indicate a significant increase in liquefaction resistance for samples reinforced with compressible, non-woven geotextiles. The undrained behaviour of saturated Hostun RF sand reinforced with non-woven geotextiles is analysed on the basis of different test series. This analysis highlights the influence of reinforcement compressibility on interstitial pressure distribution in the sample, thus showing the role of this type of inclusion in the increase in liquefaction resistance. 相似文献
318.
Measurement and research method of metallogenic depths of Jiaojia orefield and Linglong orefield Shandong Province, China 总被引:1,自引:0,他引:1
Guxian Lü 《中国科学D辑(英文版)》1997,40(5):449-455
Taking the contribution of the tectonic force to the total hydrostatic pressure into account, the author puts forward a new
method on the calculation of the depth of petrogenesis and metallogenesis which is summarized as follows: first the tectonic
added hydrostatic pressured Ps is subtracted from the total hydrostatic pressure P, then using their difference Pr, according to the general method the depth of petrogenesis and metallogenesis can be determined in consideration of lateral
constraint.
By the new method the following data on the depths of the metallogenesis are obtained: 2 243.6 m (No. I and No. II veins with
metallogenic epoch of 105 Ma) and 1 632. 38 m (No. III vein with 105 Ma) for Jiaojia orefield, and 3 454.97 m (NE-trending
zone with 213.2 Ma), 1 902.79 III (ENE-trending zone with 100.28 Ma), 1 090.97 m (NE-trending zone with 80.67 Ma) and 720.55
m (NNE-trending zone with 71.86 Ma) for Linglong orefield.
Project supported by the Foundation of the State Planning Commission, China and the Foundation of the State Science and Technology
Commission, China. 相似文献
319.
Yousheng Xu Hongsen Xie Jie Guo Haifei Zheng Yueming Zhang Maoshuang Song 《中国科学D辑(英文版)》1997,40(4):398-402
NaCI-H2O is the most fundamental ternary system in geology. Until now, the measurements of electrical conductivity of NaCl solutions
are still little at high pressures (> O.5 GPa) We measured the conductivity of 0.01 m NaCl solution at 0.4–5.0 GPa and 25-500°C.
The results are consistent with that of Quist and Marshall (1968) at 0.4 GPa. The conductivity of NaCl solution increases
with increasing temperature. The results also show that the conductivity of NaCl solution changes little with increasing pressure
below 1.5 GPa and changes rapidly with increasing pressure above 1.5 GPa. The rapid increase of the conductivity of NaCl solution
may play an important role in many geological processes (such as the genesis of ore deposits under hydrothermal condition)
and other fields.
Project supported by the National Natural Science Foundation of China. 相似文献
320.
Crustal structure of Dabieshan orogenic belt 总被引:2,自引:0,他引:2
Chunyong Wang Xiankang Zhang Buyun Chen Xuebo Chen Songyan Song Jinhan Zheng Hongxiang Hu Hai Lou 《中国科学D辑(英文版)》1997,40(5):456-462
The crustal structures ofP velocity and density on the deep seismic sounding profile across the Ilabieshan orogenic belt are presented. There is a 5-km-thick
crustal “root” between the Yuexi and Xiaotian where the elevation is highest on the profile. An apparent Moho offset of 4.
5 km beneath the Xiaotian-Mozitan fault marks the paleo-suture of the Triassic collision. A high-velocity anomaly zone at
the depth below 3 km beneath the ultra-high pressure (UHP) zone may be correlated to the higher content of UHP metamorphic
rocks.
Project supported by the National Natural Science Foundation of China and the Joint Earthquake Science Foundation. 相似文献