全文获取类型
收费全文 | 260篇 |
免费 | 4篇 |
国内免费 | 5篇 |
专业分类
测绘学 | 3篇 |
大气科学 | 3篇 |
地球物理 | 34篇 |
地质学 | 137篇 |
海洋学 | 8篇 |
天文学 | 77篇 |
自然地理 | 7篇 |
出版年
2022年 | 1篇 |
2021年 | 5篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 18篇 |
2017年 | 11篇 |
2016年 | 17篇 |
2015年 | 6篇 |
2014年 | 9篇 |
2013年 | 18篇 |
2012年 | 11篇 |
2011年 | 14篇 |
2010年 | 3篇 |
2009年 | 11篇 |
2008年 | 11篇 |
2007年 | 8篇 |
2006年 | 6篇 |
2005年 | 10篇 |
2004年 | 3篇 |
2003年 | 1篇 |
2002年 | 5篇 |
2001年 | 6篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 4篇 |
1997年 | 1篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 7篇 |
1991年 | 1篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1978年 | 5篇 |
1977年 | 1篇 |
1969年 | 1篇 |
1917年 | 1篇 |
1907年 | 1篇 |
排序方式: 共有269条查询结果,搜索用时 546 毫秒
261.
The first and second order generating functions and the first second and third order new J-S-U-N Hamiltonians are calculated by the Hori-Lie procedure. 相似文献
262.
We construct a first order canonical general planetary theory, assuming the solar system to be composed of 8 planets excluding Pluto, referring to common fixed plane and applying the Jacobi-Radau set of origins. We eliminated by von Zeipel's method the 2:5 and 1:2 critical terms of Jupiter-Saturn and Uranus-Neptune inequalities. Our variables are those of Poincaré, and we expanded up to power three in the eccentricities and sines of the inclinations. 相似文献
263.
Osman Demircan 《Astrophysics and Space Science》1987,135(1):169-174
Photoelectric BV observations of W UMa-type binaries CK Boo, BI CVn, and AH Vir are presented, and light curve variations and shifts of minima are discussed in the context of stellar activity and mass transfer. The O–C increments in three systems were found to be 0.08, 0.80, and 0.60 s per revolution, respectively. The new ephemeris for the future observations were also found. 相似文献
264.
265.
Early Maastrichtian larger foraminifera of the Qahlah Formation, United Arab Emirates and Sultanate of Oman border region 总被引:2,自引:0,他引:2
The Early Maastrichtian (Late Cretaceous) Qahlah Formation is the oldest stratigraphical unit lying upon the eroded top of the obducted Semail Ophiolite, of Santonian–Campanian age, in the Northern Oman Mountains. It crops out as a series of low hills on the western flank of the mountains, which are located along the boundary between the United Arab Emirates and the Sultanate of Oman. This paper presents the results of an investigation into the bio- and lithofacies of the Qahlah Formation in the Jabal Huwayyah section (at the boundary between the Al Ain area of the United Arab Emirates and the Buraimi area of Oman). The data collected were used to determine the age and depositional environment of the rock unit studied. In addition, the section is lithostratigraphically correlated with other sections in the study area. Microfossils from Jabal Huwayyah are represented mainly by the larger benthic foraminifera Loftusia elongata, L. morgani, Pseudorbitolina marthae, Orbitoides media, Omphalocyclus macroporus and Lepidorbitoides minor. These foraminifera are reported for the first time from this section. The diversity and abundance of fauna, particularly within the calcareous siltstone bed near the top of the formation (unique to the Huwayyah area), reflect a shallow marine depositional environment. 相似文献
266.
Earthquakes are one of the most important natural hazards to be evaluated carefully in engineering projects, due to the severely damaging effects on human-life and human-made structures. The hazard of an earthquake is defined by several approaches and consequently earthquake parameters such as peak ground acceleration occurring on the focused area can be determined. In an earthquake prone area, the identification of the seismicity patterns is an important task to assess the seismic activities and evaluate the risk of damage and loss along with an earthquake occurrence. As a powerful and flexible framework to characterize the temporal seismicity changes and reveal unexpected patterns, Poisson hidden Markov model provides a better understanding of the nature of earthquakes. In this paper, Poisson hidden Markov model is used to predict the earthquake hazard in Bilecik (NW Turkey) as a result of its important geographic location. Bilecik is in close proximity to the North Anatolian Fault Zone and situated between Ankara and Istanbul, the two biggest cites of Turkey. Consequently, there are major highways, railroads and many engineering structures are being constructed in this area. The annual frequencies of earthquakes occurred within a radius of 100 km area centered on Bilecik, from January 1900 to December 2012, with magnitudes (M) at least 4.0 are modeled by using Poisson-HMM. The hazards for the next 35 years from 2013 to 2047 around the area are obtained from the model by forecasting the annual frequencies of M ≥ 4 earthquakes. 相似文献
267.
268.
The Cerchar abrasivity index (CAI) is one of the most widely known index method for identification of rock abrasivity. It is a simple and fast testing method providing reliable information on rock abrasiveness. In this study, the relationships between the CAI and some rock properties such as uniaxial compressive strength (UCS), point load strength, Brazilian tensile strength and Schmidt rebound hardness, and equivalent quartz content (EQC) are examined. The relationships between the CAI and drill bit lifetime is also investigated and the type of drill bit wear observed is mentioned. Additionally, the CAI is modeled using simple and multiple linear regression analysis based on the rock properties. Drill bit lifetime is also modeled based on the CAI. The results show that the CAI increases with the increase of the UCS, point load strength, Brazilian tensile strength, L-type and N-type Schmidt rebound hardness, and the EQC. It is concluded that the higher and the lower bit lifetime are obtained for marl and andesitic-basaltic formation, respectively. Moreover, flushing holes, inserted button, button removal, and failures of button on the bits are determined as the type of drill bit wear. The modeling results show that the models based on the UCS and the EQC give the better forecasting performances for the CAI. 相似文献
269.
Mohammed Benaafi Mustafa Hariri Osman Abdullatif Mohammed Makkawi Abdulaziz Al-Shaibani 《Arabian Journal of Geosciences》2017,10(5):106
The Wajid Group is a Cambro-Permian sedimentary succession in southwest Saudi Arabia. This group is a well-known groundwater aquifer in the Wadi Al-Dawasir and Najran areas. The group also represents siliciclastic hydrocarbon reservoirs in the Rub' Al-Khali Basin. The Wajid Group is exposed in an area extending from Wadi Al-Dawasir southward to Najran city. This study aims to map and characterize the lineament traces of the Wajid Group outcrops. Landsat-8 OLI/TIRS satellite images with 30-m resolution, Spot-5 satellite images with 2.5-m resolution and SRTM digital elevation models (DEM) with 30-m resolution were used for lineament trace detection. Those lineament traces supplemented by aeromagnetic lineaments detected from reduced to pole magnetic anomaly map of the studied outcrop. Multi-scale lineament trace maps were generated, and the lineament datasets, including orientation and length, were analyzed statistically. Eight lineament trace trends were identified including NW-SE, NNW-SSE, N-S, NNE-SSW, NE-SW, ENE-WSW, E-W, and WNW-ESE. The northerly, northwesterly, and northeasterly trending lineament traces are predominant. The lineament trace lengths are generally followed the power law distribution. The lineament trace trends were validated through field investigation of the Wajid Group outcrop. The reported outcrop fracture trends are consistent with major lineament trace trends. Lineaments within the Wajid Group outcrop are also consistent with those of the southern portion of the Arabian Shield. The results of this study provide insight into the tectonic origin of the Wajid Group outcrop lineaments, and understanding of the lineaments distribution which can help to predict the fluid flow behavior within the groundwater fractured aquifers or hydrocarbon fractured reservoirs in Rub’ Al-Khali Basin. 相似文献