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461.
In the Soil Conservation Service Curve Number (SCS‐CN) method, the three levels of antecedent moisture condition (AMC) permit unreasonable sudden jumps in curve numbers, which result into corresponding jumps in the estimated runoff. A few recently developed SCS‐CN‐based models obviate this problem, yet they have several limitations. In this study, such a model incorporating a continuous function for antecedent moisture has been presented. It has several advantages over the other existing SCS‐CN‐based models. Its application to a large dataset from US watersheds showed to perform better than the existing SCS‐CN method and the others based on it. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
462.
Molla Nageswar Rao Gaud Angad Ram Anirudh Vidavalur Siddaiah Sudhakaran Rakesh Payipattu Pitchaikkaran Raja 《Ocean Science Journal》2021,56(1):55-68
Ocean Science Journal - This study seeks to evaluate levels of seven trace metals (Cr, Mn, Fe, Cu, Zn, Pb and Hg) and biochemical (proteins, lipids and carbohydrates) alterations in muscle tissue... 相似文献
463.
J. Meléndez I. Ramírez L. Casagrande M. Asplund B. Gustafsson D. Yong J. D. do Nascimento Jr. M. Castro M. Bazot 《Astrophysics and Space Science》2010,328(1-2):193-200
We review three Li problems. First, the Li problem in the Sun, for which some previous studies have argued that it may be Li-poor compared to other Suns. Second, we discuss the Li problem in planet hosting stars, which are claimed to be Li-poor when compared to field stars. Third, we discuss the cosmological Li problem, i.e. the discrepancy between the Li abundance in metal-poor stars (Spite plateau stars) and the predictions from standard Big Bang Nucleosynthesis. In all three cases we find that the “problems” are naturally explained by non-standard mixing in stars. 相似文献
464.
Implementation and integrated numerical modeling of a landslide early warning system: a pilot study in Colombia 总被引:3,自引:2,他引:1
Christian Huggel Nikolay Khabarov Michael Obersteiner Juan Manuel Ramírez 《Natural Hazards》2010,52(2):501-518
Landslide early warning systems (EWS) are an important tool to reduce landslide risks, especially where the potential for
structural protection measures is limited. However, design, implementation, and successful operation of a landslide EWS is
complex and has not been achieved in many cases. Critical problems are uncertainties related to landslide triggering conditions,
successful implementation of emergency protocols, and the response of the local population. We describe here the recent implementation
of a landslide EWS for the Combeima valley in Colombia, a region particularly affected by landslide hazards. As in many other
cases, an insufficient basis of data (rainfall, soil measurements, landslide event record) and related uncertainties represent
a difficult complication. To be able to better assess the influence of the different EWS components, we developed a numerical
model that simulates the EWS in a simplified yet integrated way. The results show that the expected landslide-induced losses
depend nearly exponentially on the errors in precipitation measurements. Stochastic optimization furthermore suggests an increasing
adjustment of the rainfall landslide-triggering threshold for an increasing observation error. These modeling studies are
a first step toward a more generic and integrated approach that bears important potential for substantial improvements in
design and operation of a landslide EWS. 相似文献
465.
Arti Goyal Mukul Mhaskey Gopal-Krishna Paul J. Wiita C. S. Stalin Ram Sagar 《Journal of Astrophysics and Astronomy》2013,34(3):273-296
It is important to quantify the underestimation of rms photometric errors returned by the commonly used APPHOT algorithm in the IRAF software, in the context of differential photometry of point-like AGN, because of the crucial role it plays in evaluating their variability properties. Published values of the underestimation factor, η, using several different telescopes, lie in the range 1.3–1.75. The present study aims to revisit this question by employing an exceptionally large data set of 262 differential light curves (DLCs) derived from 262 pairs of non-varying stars monitored under our ARIES AGN monitoring program for characterizing the intra-night optical variability (INOV) of prominent AGN classes. The bulk of these data were taken with the 1-m Sampurnanad Telescope (ST). We find η?=?1.54±0.05 which is close to our recently reported value of η?=?1.5. Moreover, this consistency holds at least up to a brightness mismatch of 1.5 mag between the paired stars. From this we infer that a magnitude difference of at least up to 1.5 mag between a point-like AGN and comparison star(s) monitored simultaneously is within the same CCD chip acceptable, as it should not lead to spurious claims of INOV. 相似文献
466.
Despite the recent upsurge in rock coast research, many aspects of abrasion and their relationships to other processes remain poorly understood. In this paper, mechanisms subsumed under the general term abrasion were investigated at the beaches of Oia and Sartaña along the Galician coast of NW Spain, in particular at the micro- to meso-scale (mm–cm). Relationships between abrasion and mechanical rock strength served to explore feedbacks between weathering and abrasion on rock coasts, based on measurements of rock surface strength by means of the Equotip (Proceq) method, and stereomicroscope analyses of rock surfaces undergoing varying degrees of abrasion. The results suggest that (1) abrasion along near-vertical rock surfaces leads to a decrease in rock strength with elevation above the top of the basal sediment layer, (2) abrasion processes encompass two different modes, namely, the wave-induced sweeping and dragging of sand and gravel, and the projection of clasts against rock surfaces, each mode depending predominantly on the grain size of the abrasive agent, and (3) the two abrasion modes produce different rock surfaces whose roughness is strongly influenced by the properties of diverse minerals, in particular fracture and cleavage. 相似文献
467.
We developed ring-width chronologies of Cedrus deodara [(Roxb.) G. Don] and Pinus gerardiana (Wall. Ex. Lamb) from a homogeneous moisture stressed area in Kinnaur, Himachal Pradesh. Running correlation using a 50-year window with overlap of 25 years showed strong correlations between these species chronologies during the entire common period (ad 1310–2005). Response function analysis indicated that except for January–February, precipitation has a direct relationship with growth of these species. We therefore combined both the species chronologies to develop a statistically calibrated reconstruction of March–July precipitation that spans from ad 1310–2004, and explains 46% of the variance contained in the instrumental data from the calibration period 1951–1994. In the past 694 years of the reconstruction, the wettest period was in the twentieth century (1963–1992) and the driest in the eighteenth century (1773–1802). The relationships observed between reconstructed precipitation and Indian summer monsoon on interdecadal scale, SOI, PDO and NAO indicate the potential utility of such long-term reconstructions in understanding the large-scale climate variability. Multi-taper method (MTM) spectral analysis indicated significant (p < 0.05) spectral peaks at 2–4, 6, 8, 10, 30, 33, 37 and 40–42 years in the reconstructed precipitation data. 相似文献
468.
Ramón de Elía Daniel Caya Hélène Côté Anne Frigon Sébastien Biner Michel Giguère Dominique Paquin Richard Harvey David Plummer 《Climate Dynamics》2008,30(2-3):113-132
This work is a first step in the analysis of uncertainty sources in the RCM-simulated climate over North America. Three main
sets of sensitivity studies were carried out: the first estimates the magnitude of internal variability, which is needed to
evaluate the significance of changes in the simulated climate induced by any model modification. The second is devoted to
the role of CRCM configuration as a source of uncertainty, in particular the sensitivity to nesting technique, domain size,
and driving reanalysis. The third study aims to assess the relative importance of the previously estimated sensitivities by
performing two additional sensitivity experiments: one, in which the reanalysis driving data is replaced by data generated
by the second generation Coupled Global Climate Model (CGCM2), and another, in which a different CRCM version is used. Results
show that the internal variability, triggered by differences in initial conditions, is much smaller than the sensitivity to
any other source. Results also show that levels of uncertainty originating from liberty of choices in the definition of configuration
parameters are comparable among themselves and are smaller than those due to the choice of CGCM or CRCM version used. These
results suggest that uncertainty originated by the CRCM configuration latitude (freedom of choice among domain sizes, nesting
techniques and reanalysis dataset), although important, does not seem to be a major obstacle to climate downscaling. Finally,
with the aim of evaluating the combined effect of the different uncertainties, the ensemble spread is estimated for a subset
of the analysed simulations. Results show that downscaled surface temperature is in general more uncertain in the northern
regions, while precipitation is more uncertain in the central and eastern US. 相似文献
469.
The spiral arms of disk galaxies are very sensitive to various morphological properties, such as, the gas content, the disk-to-bulge
ratioetc. Here, the stability of self-gravitating annular disks surrounding the central rigid bulge component has been studied in
order to explain the transition from the tight spiral arms in Sa galaxies to rather open patterns in Sc galaxies as the central
amorphous component diminishes. Smooth spiral patterns are found associated with the dominant (or the fastest growing) modes
of the system. When the disk-to-bulge mass ratio is small, a tight pattern results restricted to the inner regions of the
disk. This pattern opens up and occupies larger disk areas as the disk component becomes comparable to the bulge. It is found
here that the ‘explosive’ instabilities of the global density waves do not occur in the presence of a massive bulge. The growth-rates
of the eigen-modes decrease as the disk-to-bulge mass ratio decreases. It is also found that unstable modes of the annular
disk can be suppressed by increasing the thermal pressure sufficiently. 相似文献
470.
Ram Sagar 《Astrophysics and Space Science》1985,113(1):171-180
Existing methods for age estimation of open clusters are discussed. Most of the observed open clusters (except extremely young and old) contain 50–90% unevolved Main-Sequence stars. Possible difficulties encountered in estimating the actual age of an unevolved Main-Sequence star are discussed. For a relatively reliable cluster age estimation only a small percentage of cluster members are suitable. The effect of unevolved Main-Sequence stars on open cluster age estimates using the modified method of isochromes is analyzed.On leave of absence from the Department of Physics, Kumaon University, Naini Tal, India. 相似文献