全文获取类型
收费全文 | 65028篇 |
免费 | 940篇 |
国内免费 | 648篇 |
专业分类
测绘学 | 1756篇 |
大气科学 | 4540篇 |
地球物理 | 12804篇 |
地质学 | 22837篇 |
海洋学 | 5953篇 |
天文学 | 15385篇 |
综合类 | 174篇 |
自然地理 | 3167篇 |
出版年
2022年 | 416篇 |
2021年 | 685篇 |
2020年 | 789篇 |
2019年 | 886篇 |
2018年 | 1855篇 |
2017年 | 1711篇 |
2016年 | 2061篇 |
2015年 | 1114篇 |
2014年 | 1936篇 |
2013年 | 3387篇 |
2012年 | 2130篇 |
2011年 | 2733篇 |
2010年 | 2466篇 |
2009年 | 3199篇 |
2008年 | 2802篇 |
2007年 | 2874篇 |
2006年 | 2679篇 |
2005年 | 1852篇 |
2004年 | 1835篇 |
2003年 | 1717篇 |
2002年 | 1748篇 |
2001年 | 1564篇 |
2000年 | 1456篇 |
1999年 | 1256篇 |
1998年 | 1267篇 |
1997年 | 1236篇 |
1996年 | 1038篇 |
1995年 | 967篇 |
1994年 | 928篇 |
1993年 | 783篇 |
1992年 | 715篇 |
1991年 | 710篇 |
1990年 | 741篇 |
1989年 | 668篇 |
1988年 | 619篇 |
1987年 | 726篇 |
1986年 | 631篇 |
1985年 | 798篇 |
1984年 | 886篇 |
1983年 | 777篇 |
1982年 | 776篇 |
1981年 | 674篇 |
1980年 | 646篇 |
1979年 | 599篇 |
1978年 | 612篇 |
1977年 | 524篇 |
1976年 | 487篇 |
1975年 | 493篇 |
1974年 | 472篇 |
1973年 | 505篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Developments in the study of wave forces and construction techniques in deep water by the offshore oil industry have increased the use of marine terminals at deep water locations. A thorough understanding of moored ship dynamics when subjected to waves, wind and current combined with the use of flexible mooring lines would help to design berthing terminals for exposed areas. In this paper, the three dimensional problem of wave interactions with a barge moored to a single point is dealt with, based on the finite element method. The effect of flexibility of the mooring line and the point of mooring on the response of the barge as well as the mooring line tension is investigated. The paper compares the numerical results with model tests carried out on a barge moored to a fixed support under regular and random waves in head sea. The effect of stiffness of the mooring line on the barge response for different mooring points is discussed, which would be useful for the designers. The effect of viscous damping is also considered. The analytical results are in good agreement with the experimental results in both regular and random waves. 相似文献
992.
In Turkey, neotectonic activity originated from the collision of the Arabian and Anatolian land masses during the Middle Miocene. As a result of the collision, westward escape of the Anatolian block introduced E-W compression in Western Turkey which began to be relieved by N-S extension. The North Anatolian Fault (NAF) is the major active strike-slip fault that was formed under the neotectonic regime. The rates of the motion along this fault estimated by several authors are in the range of 0.4–2.9 cm/a according to kinematic data. In Turkey, the first studies of crustal movements by geodetic methods were started in the west section of the NAF in 1972. So far, individual activities and studies coordinated by multidisciplinary projects have been realized in this region. The results obtained from available geodetic data indicate the motion of the Anatolian block relative to Eurasia. 相似文献
993.
P. A. Taylor 《Boundary-Layer Meteorology》1972,2(3):381-389
Results are presented from a numerical experiment of wind and shear stress profile development away from a shore line; the water surface is assumed to obey the Charnock-Ellison relation between surface roughness and friction velocity. In typical cases the upwind, land surface is rough relative to the sea and the velocity and shear stress results are qualitatively similar to those for flows from relatively rough to relatively smooth solid surfaces. In the present case, however, the downwind surface roughness and friction velocity vary with position and we find that wind profile development may play a significant role in the relationship between sea surface roughness and fetch. 相似文献
994.
A one-dimensional numerical model of the planetary boundary layer was used to investigate thermal and kinetic energy budgets. The simulation experiments were based on two sets of data. The first set was based on a ‘typical’ June with climatological data extracted for the oceanic region slightly northeast of Barbados. The second set used data from the third phase of project BOMEX, for approximately the same area and time of year as the first set. Comparison with observations of three simulated elements (viz., sea surface temperature and wind and humidity at 6 m) which are important in determining the near-interface energy transports shows that:
- the model is capable of realistic simulations of both ‘typical’ conditions, and conditions for a specific four-day period;
- the model is capable of realistically simulating the differences between prevailing values of these parameters in the two cases (‘typical’ and specific four-day period).
995.
Design and Long-Term Monitoring of Tokyo International Airport Extension Project Constructed on Super-Soft Ground 总被引:1,自引:0,他引:1
K. Morohoshi K. Yoshinaga M. Miyata I. Sasaki H. Saitoh M. Tokoro N. Fukuda T. Fujii K. Yamada M. Ishikawa 《Geotechnical and Geological Engineering》2010,28(3):223-232
To meet the increasing demand for air transportation, Ministry of Land, Infrastructure and Transport had carried out the offshore
extension project at Tokyo International Airport (Haneda Airport). The airport should be constructed to be perfectly level,
but the ground conditions with very thick layers of super soft dredged soils and need for reclamation made the task very difficult.
Because of large amount of consolidation settlement, ground improvement by combined vertical drain method was applied to decrease
residual and differential settlement after opening of new airport. This paper is aimed to introduce the design concept and
method of ground improvement for this project. In addition the result of ground improvement is keeping satisfactory performance
for operating airport confirmed by long-term monitoring for airport facilities. 相似文献
996.
Ionosphere Disturbances Preceding Earthquakes according to the Data of Ground Based Station of the Vertical Ionospheric Sounding Wakkanai 总被引:1,自引:0,他引:1
S. A. Pulinets A. D. Legen’ka V. V. Hegai V. P. Kim L. P. Korsunova 《Geomagnetism and Aeronomy》2018,58(5):686-692
The paper analyzes the data of manual ionograms processing of hourly measurements of the critical frequency foF2 of the F2 ionospheric layer at the Wakkanai ionospheric vertical sounding station (Japan) in a geomagnetically quiet environment before a series of earthquakes with magnitude M > 6.0, for which the station entered the earthquake preparation zone, in order to detect possible Ionospheric Disturbances Preceding Earthquakes (IDPE), and to determine their quantitative characteristics. Detected IDPE, in the opinion of the authors, can be related to the processes of preparation of the corresponding earthquakes, i.e., to be Ionospheric Precursors of Earthquakes (IPE). 相似文献
997.
Marked fluctuation of concentrations of90Sr and137Cs was observed in the bottom waters at the entrance of Wakasa Bay during 1987–1992, and the cause was investigated. The concentrations of90Sr and137Cs in the bottom waters were significantly low when the upper level of the Japan Sea Proper Water (JSPW) was high and covered the sampling depth, but high when the upper level of the JSPW was low. The cause of the fluctuation observed in the bottom waters is, therefore, suggested to be the vertical fluctuation of the upper level of the JSPW on the shelf slope, which has been little described before. 相似文献
998.
Deshcherevskii A. V. Modin I. N. Sidorin A. Ya. 《Izvestiya Atmospheric and Oceanic Physics》2018,54(10):1490-1511
Izvestiya, Atmospheric and Oceanic Physics - In geophysical studies, particularly when searching for precursors of earthquakes, there are problems of investigating the geoelectric structure of the... 相似文献
999.
A subset of 2660 shallow earthquakes (0–50 km) that occurred from 1988 to 1996 in south central Alaska between 155°W and 145°W and 59°N and 63°N was relocated using the joint hypocenter determination (JHD) method. Both P- and S-wave observations recorded by the regional seismic network were used. Events were relocated in twenty different groups based on their geographic location and depth using two velocity models. As a result of the relocation, the majority of the hypocenters shifted downward, while the epicenter locations did not change significantly. The distribution of the shallow subduction zone earthquakes indicates the existence of two seismically independent blocks, with one block occupying the northeastern part and the other occupying the central and western parts of the study area. The boundary between the blocks is marked by a 15 to 20 km wide seismicity gap to the southeast of 149.5°W and 62°N. The analysis of the fault plane solutions for shallow subduction zone earthquakes shows that an overwhelming majority of the solutions represent normal, oblique-normal or strike-slip faulting with predominant WNW-ESE orientation of T-axes. This indicates a down-dip extensional regime for the subducting slab at shallow depths. Very few earthquakes yielded fault plane solutions consistent with thrusting on a contact zone between the overriding and subducting plates. This result may be an indication that currently either the strain energy is not released at the contact zone or it is associated with aseismic motion. 相似文献
1000.
M. Déqué R. G. Jones M. Wild F. Giorgi J. H. Christensen D. C. Hassell P. L. Vidale B. Rockel D. Jacob E. Kjellström M. de. Castro F. Kucharski B. van den Hurk 《Climate Dynamics》2005,25(6):653-670
Four high resolution atmospheric general circulation models (GCMs) have been integrated with the standard forcings of the
PRUDENCE experiment: IPCC-SRES A2 radiative forcing and Hadley Centre sea surface temperature and sea-ice extent. The response
over Europe, calculated as the difference between the 2071–2100 and the 1961–1990 means is compared with the same diagnostic
obtained with nine Regional Climate Models (RCM) all driven by the Hadley Centre atmospheric GCM. The seasonal mean response
for 2m temperature and precipitation is investigated. For temperature, GCMs and RCMs behave similarly, except that GCMs exhibit
a larger spread. However, during summer, the spread of the RCMs—in particular in terms of precipitation—is larger than that
of the GCMs. This indicates that the European summer climate is strongly controlled by parameterized physics and/or high-resolution
processes. The temperature response is larger than the systematic error. The situation is different for precipitation. The
model bias is twice as large as the climate response. The confidence in PRUDENCE results comes from the fact that the models
have a similar response to the IPCC-SRES A2 forcing, whereas their systematic errors are more spread. In addition, GCM precipitation
response is slightly but significantly different from that of the RCMs. 相似文献