全文获取类型
收费全文 | 967篇 |
免费 | 31篇 |
国内免费 | 27篇 |
专业分类
测绘学 | 34篇 |
大气科学 | 156篇 |
地球物理 | 193篇 |
地质学 | 247篇 |
海洋学 | 257篇 |
天文学 | 64篇 |
综合类 | 17篇 |
自然地理 | 57篇 |
出版年
2023年 | 8篇 |
2022年 | 11篇 |
2021年 | 7篇 |
2020年 | 18篇 |
2019年 | 25篇 |
2018年 | 37篇 |
2017年 | 44篇 |
2016年 | 74篇 |
2015年 | 37篇 |
2014年 | 60篇 |
2013年 | 85篇 |
2012年 | 62篇 |
2011年 | 49篇 |
2010年 | 56篇 |
2009年 | 48篇 |
2008年 | 48篇 |
2007年 | 40篇 |
2006年 | 43篇 |
2005年 | 41篇 |
2004年 | 29篇 |
2003年 | 21篇 |
2002年 | 19篇 |
2001年 | 19篇 |
2000年 | 17篇 |
1999年 | 22篇 |
1998年 | 9篇 |
1997年 | 8篇 |
1996年 | 7篇 |
1995年 | 7篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1990年 | 3篇 |
1987年 | 6篇 |
1986年 | 2篇 |
1984年 | 8篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 7篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1973年 | 5篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1968年 | 1篇 |
1967年 | 3篇 |
排序方式: 共有1025条查询结果,搜索用时 31 毫秒
111.
R.G. Park 《Precambrian Research》1981,14(1):31-47
The later Archaean history of the granite-greenstone terrain of the western Superior Province in Manitoba was marked by the development of numerous shear zones with varying orientation and sense of movement. Data are presented on the orientation, width and displacement of 15 shear zones in a 61,000 km2 area east of Lake Winnipeg. By making simplifying assumptions, estimates are made of the orientation of the maximum compressive stress (N-S) and the bulk shortening strain caused by the shear zone displacements (39–45%).The estimates of shear zone displacement strain are compared with estimates of bulk strain obtained by analysing the granite-greenstone shape pattern over a large area of the western Superior Province, again making simplifying assumptions. As expected, the contribution of the more ductile greenstones to the bulk strain is proportionately greater. A value of around 40% is indicated for the bulk shortening strain.Estimates of mean shear strain obtained both from shear zone displacement/width measurements and from strain profiles show a wide range in values from around 10 in some narrow zones to around 1 in very wide zones. 相似文献
112.
On the relative importance of the driving forces of plate motion 总被引:4,自引:0,他引:4
113.
The Menderes Massif, in western Anatolia, has been described as a lithological succession comprising a basal ‘Precambrian gneissic core of sedimentary origin’ overlain in sequence by ‘Palaeozoic schist’ and ‘Mesozoic-Cenozoic marble’ forming the envelope. The boundary between core and schist envelope was interpreted as a major unconformity, the ‘Supra-Pan-African unconformity’. By contrast, our field observations and geochemical data show that around the southern side of Besparmak Mountain, north of Selimiye (Milas), the protoliths of highly deformed, mylonitized augen gneisses are granitoid rocks intrusive into the adjacent Palaeozoic metasedimentary schists. The field relationships indicate the age of intrusion to be younger than late Permian and there is no evidence for the existence of either an exposed Precambrian basement or the ‘Supra-Pan-African unconformity’ in this sector of the Menderes Massif. 相似文献
114.
The alignments of the strapdown inertial navigation system (SDINS) utilizing GPS carrier phase rate measurements is introduced. In this paper, a measurement model of GPS carrier phase rate under two antenna configurations is derived in order to be used for the SDINS alignment process. For in-flight alignment, the performance of the proposed SDINS/GPS integration method is analyzed using the covariance analysis and the overall performance is briefly confirmed by the navigation result of a van test. Furthermore, we find that during in-flight alignment the proposed SDINS/GPS integrated system using GPS carrier phase rate measurements can be implemented in real time because the integer ambiguity problem resulting from carrier phase measurements is avoided. 相似文献
115.
The low seismic activity of the Korean Peninsula surrounded by high earthquake countries 总被引:1,自引:0,他引:1
Although the Korean Peninsula is locatednear several great earthquake regions suchas NE China and SW Japan, it has neversuffered from catastrophic earthquakes forthe last 2000 years according to historicaland instrumental records. We investigatedthe low seismicity of Korea based on thehypothesis of the Baikal-Korea Plate (BKP)or Amurian Plate movement which isinitiated by the Baikal Rift Zone spreadingin a southeastward motion with acounter-clockwise rotation due to thecollision of the Indian Plate against theEurasian Plate. Many disastrous earthquakesof NE China, SW Japan and Sakhalin releaselarge amounts of seismic energy along theboundary of the Baikal-Korea Plate. It isnecessary to compute the released seismicenergy along the presumed boundary of theBaikal-Korea Plate compared to the KoreanPeninsula in order to estimate themicro-plate boundary. The total energyreleases (1900–1999) from the majordisastrous earthquakes (M6.0) alongthe Baikal-Korea plate are about103–104 times as much as theKorean Peninsula (M3.0). The focalmechanisms for the intra-continentalearthquakes near and/or along theBaikal-Korea Plate boundary of NE China, SW Japan, Sakhalin and Mongolia mostlyrepresent the horizontal motions of theright-lateral strike slip type, indicatingthat the Baikal-Korea Plate is acounter-clockwise and transcurrent motion. The relative displacement vectors of GPS(global positioning system) also indicatedthat the Baikal-Korea Plate movescounter-clockwise around the KoreanPeninsula. These factors may indicate thatthe Korean Peninsula is not located at thePlate boundary, but just within a margin ofthe Baikal-Korea Plate which movessoutheastward with a counter-clockwiserotation from the Baikal Rift Zone in NEAsia. Therefore there is no enoughaccumulated strain to generate largeearthquakes in the Korean Peninsula and itmakes the Korean Peninsula free fromseismic hazard of large catastrophicearthquakes. 相似文献
116.
Retracking considerations in spaceborne GNSS-R altimetry 总被引:1,自引:0,他引:1
Hyuk Park Adriano Camps Enric Valencia Nereida Rodriguez-Alvarez Xavier Bosch-Lluis Isaac Ramos-Perez Hugo Carreno-Luengo 《GPS Solutions》2012,16(4):507-518
The European Space Agency Passive Reflectometry and Interferometry System In-orbit Demonstrator (IoD) aims to perform mesoscale altimetric observations by measuring the Global Navigation Satellite System (GNSS) opportunity signals reflected over the sea surface. Altimetry based on GNSS reflectometry (GNSS-R) is significantly affected by satellite motion, since it requires relatively long integration times to reduce noise. We present the impact of the satellite motion on the GNSS-R observables and the need to retrack the waveforms. By using a detailed GNSS-R space mission simulator, the change of delay difference between the direct and the reflected signals during the incoherent averaging of the waveform has been investigated. Their effects on the waveform shape and the altimetric performance are presented comparing the aligned and non-aligned waveforms. Results show that the performance of spaceborne GNSS-R altimeter is seriously degraded without a proper alignment of the waveform samples. 相似文献
117.
The direct and semi-direct radiative effects of anthropogenic aerosols on the radiative transfer and cloud fields in the Western United States (WUS) according to seasonal aerosol optical depth (AOD) and regional climate are examined using a regional climate model (RCM) in conjunction with the aerosol fields from a GEOS-Chem chemical-transport model (CTM) simulation. The two radiative effects cannot be separated within the experimental design in this study, thus the combined direct- and semi-direct effects are called radiative effects hereafter. The CTM shows that the AOD associated with the anthropogenic aerosols is chiefly due to sulfates with minor contributions from black carbon (BC) and that the AOD of the anthropogenic aerosol varies according to local emissions and the seasonal low-level winds. The RCM-simulated anthropogenic aerosol radiative effects vary according to the characteristics of regional climate, in addition to the AOD. The effects on the top of the atmosphere (TOA) outgoing shortwave radiation (OSRT) range from ?0.2?Wm?2 to ?1?Wm?2. In Northwestern US (NWUS), the maximum and minimum impact of anthropogenic aerosols on OSRT occurs in summer and winter, respectively, following the seasonal AOD. In Arizona-New Mexico (AZNM), the effect of anthropogenic sulfates on OSRT shows a bimodal distribution with winter/summer minima and spring/fall maxima, while the effect of anthropogenic BC shows a single peak in summer. The anthropogenic aerosols affect surface insolation range from ?0.6?Wm?2 to ?2.4?Wm?2, with similar variations found for the effects on OSRT except that the radiative effects of anthropogenic BC over AZNM show a bimodal distribution with spring/fall maxima and summer/winter minima. The radiative effects of anthropogenic sulfates on TOA outgoing longwave radiation (OLR) and the surface downward longwave radiation (DLRS) are notable only in summer and are characterized by strong geographical contrasts; the summer OLR in NWUS (AZNM) is reduced (enhanced) by 0.52?Wm?2 (1.14?Wm?2). The anthropogenic sulfates enhance (reduce) summer DLRS by 0.2?Wm?2 (0.65?Wm?2) in NWUS (AZNM). The anthropogenic BC affect DLRS noticeably only in AZNM during summer. The anthropogenic aerosols affect the cloud water path (CWP) and the radiative transfer noticeably only in summer when convective clouds are dominant. Primarily shortwave-reflecting anthropogenic sulfates decrease and increase CWP in AZNM and NWUS, respectively, however, the shortwave-absorbing anthropogenic BC reduces CWP in both regions. Due to strong feedback via convective clouds, the radiative effects of anthropogenic aerosols on the summer radiation field are more closely correlated with the changes in CWP than the AOD. The radiative effect of the total anthropogenic aerosols is dominated by the anthropogenic sulfates that contribute more than 80% of the total AOD associated with the anthropogenic aerosols. 相似文献
118.
Asian dust events occurred in Asia during March 2010 were simulated using the Asian Dust Aerosol Model 2 (ADAM2). The performance of the model for simulations of surface dust concentrations and dust event occurrences was tested at several monitoring sites located in the dust source region and the downstream region of Korea. The observed and modeled dust event occurrences at each monitoring site were defined with the hourly observed and modeled dust concentrations that were used to evaluate the performance of the model by constructing a contingency table for the dust event occurrence. It was found that the model simulated quite well the starting and ending times of dust events with their peak dust concentrations for most dust events occurred both in the dust source region and the downstream region of Korea. However, the model failed to simulate a few dust events observed in both regions mainly due to the inaccurate simulations of the meteorological fields. Inaccurate simulations of wind speeds have caused for the model to simulate dust events poorly in the dust source region whereas poor simulations of precipitation of the fifth-generation mesoscale model (MM5) model have led to miss dust events in the downstream region of Korea. The contingency table made with the hourly data for the dust event occurrence made it possible to evaluate the ADAM2 model for the simulation of the dust event occurrence. It was found that the model has the probabilistic simulation capability for dust events of about 78% with the hit rate of more than 83% and the false alarm rate of about 27% for the dust events occurred during March in 2010. The probabilistic capability of the model could be much improved by improving the meteorological model (MM5 model). 相似文献
119.
A multimodel comparison of centennial Atlantic meridional overturning circulation variability 总被引:1,自引:1,他引:0
Matthew B. Menary Wonsun Park Katja Lohmann Michael Vellinga Matthew D. Palmer Mojib Latif Johann H. Jungclaus 《Climate Dynamics》2012,38(11-12):2377-2388
A mechanism contributing to centennial variability of the Atlantic Meridional Overturning Circulation (AMOC) is tested with multi-millennial control simulations of several coupled general circulation models (CGCMs). These are a substantially extended integration of the 3rd Hadley Centre Coupled Climate Model (HadCM3), the Kiel Climate Model (KCM), and the Max Plank Institute Earth System Model (MPI-ESM). Significant AMOC variability on time scales of around 100?years is simulated in these models. The centennial mechanism links changes in the strength of the AMOC with oceanic salinities and surface temperatures, and atmospheric phenomena such as the Intertropical Convergence Zone (ITCZ). 2 of the 3 models reproduce all aspects of the mechanism, with the third (MPI-ESM) reproducing most of them. A comparison with a high resolution paleo-proxy for Sea Surface Temperatures (SSTs) north of Iceland over the last 4,000?years, also linked to the ITCZ, suggests that elements of this mechanism may also be detectable in the real world. 相似文献
120.
Recent and future sea surface temperature trends in tropical pacific warm pool and cold tongue regions 总被引:3,自引:2,他引:1
Soon-Il An Ji-Won Kim Seul-Hee Im Beak-Min Kim Jae-Heung Park 《Climate Dynamics》2012,39(6):1373-1383
Using coral data, sea surface temperature (SST) reanalysis data, and Climate Model Intercomparison Project III (CMIP3) data, we analyze 20th-century and future warm pool and cold tongue SST trends. For the last 100?years, a broad La Nina-like SST trend, in which the warming trend of the warm pool SST is greater than that of the cold tongue SST, has appeared in reanalysis SST data sets, 20C scenario experiments of the CMIP3 data and less significantly in coral records. However, most Coupled General Circulation Models subjected to scenarios of future high greenhouse gas concentrations produce larger SST warming trends in cold tongues than in warm pools, resembling El Nino-like SST patterns. In other words, warmer tropical climate conditions correspond to stronger El Nino-like response. Heat budget analyses further verify that warmer tropical climates diminish the role of the ocean’s dynamic thermostat, which currently regulates cold tongue temperatures. Therefore, the thermodynamic thermostat, whose efficiency depends on the mean temperature, becomes the main regulator (particularly via evaporative cooling) of both warm pool and cold tongue temperatures in future warm climate conditions. Thus, the warming tendency of the cold tongue SST may lead that of the warm pool SST in near future. 相似文献