全文获取类型
收费全文 | 625篇 |
免费 | 16篇 |
国内免费 | 28篇 |
专业分类
测绘学 | 7篇 |
大气科学 | 66篇 |
地球物理 | 184篇 |
地质学 | 172篇 |
海洋学 | 38篇 |
天文学 | 143篇 |
综合类 | 10篇 |
自然地理 | 49篇 |
出版年
2024年 | 2篇 |
2022年 | 2篇 |
2021年 | 7篇 |
2020年 | 7篇 |
2019年 | 6篇 |
2018年 | 29篇 |
2017年 | 21篇 |
2016年 | 30篇 |
2015年 | 29篇 |
2014年 | 36篇 |
2013年 | 30篇 |
2012年 | 26篇 |
2011年 | 33篇 |
2010年 | 39篇 |
2009年 | 39篇 |
2008年 | 38篇 |
2007年 | 29篇 |
2006年 | 26篇 |
2005年 | 24篇 |
2004年 | 19篇 |
2003年 | 23篇 |
2002年 | 13篇 |
2001年 | 19篇 |
2000年 | 12篇 |
1999年 | 7篇 |
1998年 | 9篇 |
1997年 | 14篇 |
1996年 | 17篇 |
1995年 | 9篇 |
1994年 | 4篇 |
1993年 | 13篇 |
1992年 | 6篇 |
1991年 | 8篇 |
1990年 | 3篇 |
1988年 | 4篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1965年 | 1篇 |
1963年 | 1篇 |
1959年 | 1篇 |
1957年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有669条查询结果,搜索用时 15 毫秒
81.
Darija Vukić Lušić Dražen Lušić Denis Pešut Vladimir Mićović Marin Glad Lovorka Bilajac Vesna Peršić 《Marine pollution bulletin》2013
The quality of bathing water is of considerable public importance due to the possibility of fecal contamination. In 2009, Croatia implemented the new European Bathing Water Directive (BWD, 2006/7/EC) establishing stricter microbiological standards for new parameters with new reference methods. This study aims to evaluate the equivalence of different methods according to the old and revised BWD and to provide the possibility of data comparison. Furthermore, the directive requires the establishment of the bathing water profile (BWP) for pollution risk assessment. The estimation of consistency of pollution risk assessment with obtained microbiological results was also performed. 相似文献
82.
Vladimir Sabinin 《Geofísica Internacional》2013,52(4):311-320
New computational techniques of QVOA analysis (Quality factor Versus Offset and Azimuth) for fracture characterization are developed. The techniques are applied to synthetic surface data of reflection with noise. 相似文献
83.
84.
William L. Bandy Yuri Taran Carlos Mortera Guti��rrez Vladimir Kostoglodov 《Pure and Applied Geophysics》2011,168(8-9):1251-1253
85.
We present a visco-elastic bubble growth model, accounting for viscous and elastic deformations and for volatile mass transfer
between bubbles and melt. We define the borders between previous bubble growth models accounting for incompressible viscous
melt, and our new model accounting also for elastic deformation; this is done by a set of end-member analytical solutions
and numerical simulations. Elastic deformation is most prominent for magma of small vesicularity, where the growth regime
depends on the shear modulus. For high shear modulus, bubble growth is slow and follows an exponential law in a viscous growth
regime, while for low shear modulus bubbles quickly follow a square-root diffusive solution. Our model provides all the elastic
components (stresses, strains and strain rates) required for defining criteria for failure and magma fragmentation. We suggest
two failure criteria, a stress related one based on the internal friction and the Mohr-Coulomb failure theory, and a strain
related one based on fibre elongation experiments. We argue that both criteria are equivalent if we consider their shear modulus
dependency and its effect on magma rheology. Last, we apply our model to the process of bubble nucleation. In the incompressible
case, following nucleation, growth is slow and leads to long incubation times during which bubbles may be dissolved back into
the melt. The elastic response in magmas with low shear modulus results in a short incubation time, increasing the probability
of survival. The above effects emphasize the significance of visco-elasticity for the dynamic processes occurring in magmas
during volcanic activity. 相似文献
86.
Results obtained by SASW and PS-logging (in-hole) seismic techniques are compared with the relatively new ReMi (Refraction microtremor) method at a common site with a well-known soil profile: a recently constructed high-speed railway embankment. PS-logging is the most accurate technique in identifying the soil profile of the embankment followed by Re-Mi and SASW. Mean shear wave velocity estimations are also higher for PS-logging, followed by SASW and ReMi, while mean deviation is similar in each technique. The ReMi technique has provided very accurate results in the study of the embankment profile, which in addition to its high operability and its fast data processing, makes it a very convenient technique for extensive geotechnical surveys. 相似文献
87.
Earthquake prediction: 20 years of global experiment 总被引:1,自引:0,他引:1
Vladimir G. Kossobokov 《Natural Hazards》2013,69(2):1155-1177
Earthquake professionals have for many decades recognized the benefits to society from reliable earthquake predictions, but uncertainties regarding source initiation, rupture phenomena, and accuracy of both the timing and magnitude of the earthquake occurrence have oftentimes seemed either very difficult or impossible to overcome. The problem is that most of these methods cannot be adequately tested and evaluated either because of (a) lack of a precise definition of “prediction” and/or (b) shortage of data for meaningful statistical verification. This is not the case for the pattern recognition algorithm M8 designed in 1984 for prediction of great, Magnitude 8, earthquakes, hence its name. By 1986, the algorithm was rescaled for applications aimed at smaller magnitude earthquakes, down to M5+ range, and since then it has become a useful tool for systematic monitoring of seismic activity in a number of test seismic regions worldwide. After confirmed predictions of both the 1988 Spitak (Armenia) and the 1989 Loma Prieta (California) earthquakes, a “rigid test” to evaluate the efficiency of the intermediate-term middle-range earthquake prediction technique has been designed. Since 1991, each half-year, the algorithm M8 alone and in combination with its refinement MSc has been applied in a real-time prediction mode to seismicity of the entire Earth, and this test outlines, where possible, the areas in the two approximations where magnitude 8.0+ and 7.5+ earthquakes are most likely to occur before the next update. The results of this truly global 20-year-old experiment are indirect confirmations of the existing common features of both the predictability and the diverse behavior of the Earth’s naturally fractal lithosphere. The statistics achieved to date prove (with confidence above 99 %) rather high efficiency of the M8 and M8-MSc predictions limited to intermediate-term middle- and narrow-range accuracy. These statistics support the following general conclusions—(1) precursory seismic patterns do exist; (2) the size of an area where precursory seismic patterns show up is much larger than that of the source zone of the incipient target earthquake; (3) many precursory seismic patterns appear to be similar, even in regions of fundamentally different tectonic environments; and (4) some precursory seismic patterns are analogous to those in advance of extreme catastrophic events in other complex nonlinear systems (e.g., magnetic storms, solar flares, “starquakes”, etc.)—that are of high importance for further searches of the improved earthquake forecast/prediction algorithms and methods. 相似文献
88.
89.
Joseph M. Grebowsky Robert F. Benson Phillip A. Webb Vladimir Truhlik Dieter Bilitza 《Journal of Atmospheric and Solar》2009,71(16):1669-1676
The projection of the plasmapause magnetic-field lines to low altitudes, where the light-ion chemistry is dominated by O+, tends to occur near the minimum electron density in the main (midlatitude) electron density trough at night. With increasing altitude in the trough, where H+ emerges as the dominant ion on the low-latitude boundary, we have found cases where the plasmapause field lines are located on the sharp low-latitude side of the trough as expected if this topside ionosphere H+ distribution varies in step with the plasmapause gradient in the distant plasmasphere. These conclusions are based on near-equatorial crossings of the plasmapause (corresponding to the steep gradient in the dominant species H+) by the Explorer-45 satellite as determined from electric-field measurements by Maynard and Cauffman in the early 1970s and ISIS-2 ionospheric topside-sounder measurements. The former data have now been converted to digital form and made available at http://nssdcftp.gsfc.nasa.gov. The latter provide samples of nearly coincident observations of ionospheric main trough crossings near the same magnetic-field lines of the Explorer 45-determined equatorial plasmapause. The ISIS-2 vertical electron density profiles are used to infer where the F-region transitions from an O+ to a H+ dominated plasma through the main trough boundaries. 相似文献
90.
A major complication caused by anisotropy in velocity analysis and imaging is the uncertainty in estimating the vertical velocity and depth scale of the model from surface data. For laterally homogeneous VTI (transversely isotropic with a vertical symmetry axis) media above the target reflector, P‐wave moveout has to be combined with other information (e.g. borehole data or converted waves) to build velocity models for depth imaging. The presence of lateral heterogeneity in the overburden creates the dependence of P‐wave reflection data on all three relevant parameters (the vertical velocity VP0 and the Thomsen coefficients ε and δ) and, therefore, may help to determine the depth scale of the velocity field. Here, we propose a tomographic algorithm designed to invert NMO ellipses (obtained from azimuthally varying stacking velocities) and zero‐offset traveltimes of P‐waves for the parameters of homogeneous VTI layers separated by either plane dipping or curved interfaces. For plane non‐intersecting layer boundaries, the interval parameters cannot be recovered from P‐wave moveout in a unique way. Nonetheless, if the reflectors have sufficiently different azimuths, a priori knowledge of any single interval parameter makes it possible to reconstruct the whole model in depth. For example, the parameter estimation becomes unique if the subsurface layer is known to be isotropic. In the case of 2D inversion on the dip line of co‐orientated reflectors, it is necessary to specify one parameter (e.g. the vertical velocity) per layer. Despite the higher complexity of models with curved interfaces, the increased angle coverage of reflected rays helps to resolve the trade‐offs between the medium parameters. Singular value decomposition (SVD) shows that in the presence of sufficient interface curvature all parameters needed for anisotropic depth processing can be obtained solely from conventional‐spread P‐wave moveout. By performing tests on noise‐contaminated data we demonstrate that the tomographic inversion procedure reconstructs both the interfaces and the VTI parameters with high accuracy. Both SVD analysis and moveout inversion are implemented using an efficient modelling technique based on the theory of NMO‐velocity surfaces generalized for wave propagation through curved interfaces. 相似文献