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191.
C. Rodríguez-López A. Moya R. Garrido J. MacDonald R. Oreiro A. Ulla 《Astrophysics and Space Science》2010,329(1-2):205-209
Mode trapping of high-radial order gravity modes was found for a particular sdO model. The trapping is caused by the change in composition from the helium radiative shell to the hydrogen burning shell. A non-adiabatic effect of this trapping is the higher tendency to instability of the trapped modes. Low- to intermediate-radial order pressure modes (in sdO models they correspond to mixed modes with most nodes in the P-mode region) are found to be trapped by the chemical transition from the carbon-oxygen core to the He burning shell. As the trapping is produced in the deep interior of the star, where energy interchange is negligible at the p-mode frequencies, it has no particular effect on the driving. 相似文献
192.
In this paper we present a new method of restoration of the true three-dimensional (3D) trajectories of prominence knots using
ground-based observations taken with a single telescope that is equipped with a Multi-Channel Subtractive Double Pass imaging
spectrograph. Our method allows us to evaluate the true 3D trajectories of the prominence knots without any assumptions concerning
the shape of the trajectories or the dynamics of the motion. The reconstructed trajectories of several knots observed in three
prominences are presented. 相似文献
193.
Detection of nitric acid (HNO<Subscript>3</Subscript>) in the atmosphere using the LOPAP technique 总被引:1,自引:0,他引:1
Jörg Kleffmann Traian Gavriloaiei Yasin Elshorbany Milagros Ródenas Peter Wiesen 《Journal of Atmospheric Chemistry》2007,58(2):131-149
A new instrument (LOPAP: LOng Path liquid Absorption Photometer) for the sensitive detection of nitric acid (HNO3) in the atmosphere is described. HNO3 is sampled in a temperature controlled stripping coil mounted in an external sampling module to minimize sampling artefacts in sampling lines. After conversion into a strongly absorbing dye, HNO3 is detected in long path absorption in special Teflon® AF 2400 tubes used as liquid core wave guides. For the correction of some interferences, due to for example HONO and particle nitrate, two channels are used in series. The interferences from several potential interfering compounds including particle nitrate were quantified in the laboratory and in a large outdoor simulation chamber. With the exception of the interference caused by N2O5, which is quantitatively measured by the instrument, all tested interferences can be corrected under atmospheric conditions. Thus, in the instrument only the sum of N(V) from HNO3 and N2O5 is determined, which is expected to be a common problem of wet chemical HNO3 instruments. The instrument has a detection limit of 5–30 pptv for a time response of 6–2 min, respectively and was validated against the FTIR technique in a large outdoor simulation chamber. In addition, the applicability of the instrument was demonstrated in a field campaign. 相似文献
194.
Juan C. López Vieyra Alexander V. Turbiner Nicolais L. Guevara 《Astrophysics and Space Science》2007,308(1-4):493-497
- The exotic system H 3 ++ (which does not exist without magnetic field) exists in strong magnetic fields:
- In triangular configuration for B≈108–1011?G (under specific external conditions)
- In linear configuration for B>1010?G
- In the linear configuration the positive z-parity states 1σ g , 1π u , 1δ g are bound states
- In the linear configuration the negative z-parity states 1σ u , 1π g , 1δ u are repulsive states
- The H 3 ++ molecular ion is the most bound one-electron system made from protons at B>3×1013?G
195.
Geotechnical Characterization by In situ and Lab Tests to the Back-Analysis of a Supported Excavation in Metro do Porto 总被引:1,自引:1,他引:0
António Viana da Fonseca Sara Rios Silva Nuno Cruz 《Geotechnical and Geological Engineering》2010,28(3):251-264
This paper summarizes the geotechnical characterization conducted for the design and subsequent analysis of a strutted excavation in “Metro do Porto”. This region is geologically dominated by heterogeneous weathered granite masses with deep residual soil profiles. Local saprolitic soils exhibit, by their nature, a particular behavior characterized by very sensitive and weak relic micro-structures, due to their specific genesis. This study has included the interpretation of a significant volume of in situ test results, triaxial tests over undisturbed samples and monitoring data, giving rise to specific correlations between testing and design parameters. Real time monitoring enabled a back-analysis by FEM of a well instrumented section of the strutted excavation, which was calibrated taking into account the derived correlations and the deformability behavior of this specific geotechnical ambient. This geomaterial, although revealing very high initial stiffness values (for very small strain ranges) has shown low stiffness values for “medium to high” strain levels, reflecting a singular strong non-linearity in the stress-strain behavior. 相似文献
196.
197.
Damage and parameters of the earthquakes of October 14, 1800, September 18, 1826, and July 7, 1842, in Santiago de Cuba, in southeastern Cuba, have been studied. A quantitative re-evaluation of the size of the events is not feasible due to a lack of data. Hence, we have reinterpreted existing data to establish likely intensities and determine the epicentral region of occurrence. Available data do not permit accurate depth determinations. Intensities estimated from contemporary documentary sources give maximum values of 8, 8–9 and 8 (MSK scale), respectively. These seismic shocks were located in the Southeastern Seismotectonic Province of Cuba, Plate Boundary Zone Caribbean—North Atmerican. The earthquakes are associated with the Oriente fault system. 相似文献
198.
M. Villalobos D. G. García-Payne J. L. López-Zepeda A. E. Ceniceros-Gómez M. E. Gutiérrez-Ruiz 《Aquatic Geochemistry》2010,16(2):225-250
Arsenic from natural and anthropogenic sources is a worldwide contaminant of aqueous environments, such as groundwater and
soils. The present investigation was performed on Mexican soils contaminated with residues from metallurgical processes that
have shown a natural As attenuation. Experimental aqueous arsenic extractions in these were successfully simulated for almost
half of the soil samples using a database updated for all known metal arsenate formation constants, revealing the predominance
of solubility-controlled As mobility via Pb, mixed Pb–Cu, and Ca arsenate solid formation. The relatively low total Fe/As
ratios (2–13 w/w) present in the soils studied, together with the high and equivalent contents of As, Pb, and Cu in these,
favor the precipitation process over As(V) adsorption to Fe oxides, despite a 2% average Fe content in the soils studied.
Under these conditions bicarbonate was found to be a highly unsuitable extractant due to its indirect As release from the
solid arsenates, via heavy metal carbonate precipitation processes. 相似文献
199.
F. Figueroa J. Castro-Larragoitia A. Aragón J. V. García-Meza 《Environmental Earth Sciences》2010,60(2):395-407
The 7-year-old mine tailings pile P2 from Concepción del Oro has been revegetated spontaneously by xerophyte grasses, covering
about the 30% of its surface. To elucidate the effect of the grass cover in the geochemical behavior of the sulfide minerals
(SM) and metals, the strata of four selected profiles (P2-I, P2-II, P2-III and P2-IV, with high, middle, low, and null grass
cover, respectively) were analyzed mineralogically and chemically, using scanner electron microscopy, X-ray diffractometer
and performing a six-step sequential extraction method. An older (50-year-old) and uncovered (without grass cover) profile
of the tailings pile P3 was also analyzed. In all the profiles from P2, the SM oxidation is not yet an extended process; however,
the samples from the uncovered profile P2-IV showed evidences of SM (pyrite and chalcocite) oxidation, as well as the presence
of gypsum and Fe oxides, as the major secondary phases resulted from the SM oxidation. Additionally, the carbonate content
and pH values in P2-IV were lower than in the covered profiles from P2. The oldest and uncovered P3-I profile showed an extensive
oxidation of sulfurs which resulted in the depletion of carbonates and a pH 2. Another distinctive characteristics of the
covered profiles was that Pb, Cu, and Zn were mainly associated with the reducible fractions (carbonates and/or amorphous
oxides); meanwhile, in the uncovered (P2-IV and P3-I) such metals were mainly associated with the oxidizable fraction (crystalline
oxides). The results suggest that the mineralogical transformations control metal stability in plant-covered impoundments
(phytostabilization): the occurrence of a thick grass cover, with an efficient water usage and retention, seems to shun both
the acidic dissolution of carbonates and the reductive dissociation of the formerly present oxyhydroxides, which is desired
for remediation tasks. This is the first report about the effects of grass cover for a carbonaceous and unsaturated mine tailings
from a semiarid region, that can help in a better understanding of the scope of phytoremediation in such conditions. 相似文献
200.
Edmundo Placencia-Gómez Annika Parviainen Tero Hokkanen Kirsti Loukola-Ruskeeniemi 《Environmental Earth Sciences》2010,61(7):1435-1447
The Haveri tailings area contains 1.5 Mt of sulfide-bearing waste from the Au–Cu mine that operated during 1942–1961. Geophysical
and geochemical methods were used to evaluate and characterize the generation of acid mine drainage (AMD). Correlations were
examined among the electrical resistivity tomography (ERT) data, the total sulfide content and concentrations of sulfide-bound
metals (Cu, Co, Fe, Mn, Ni, Pb and Zn) of tailings samples, and the resistivity and geochemistry of surface water. The resulting
geophysical–geochemical model defines an area in the vadose tailings, where a low resistivity anomaly (<10 Ohm m) is correlated
with the highest sulfide content, extensive sulfide oxidation and low pH (average 3.1). The physical and geochemical conditions,
resulting from the oxidation of the sulfide minerals, suggest that the low resistivity anomaly is associated with acidic and
metal-rich porewater (i.e., AMD). The lower resistivity values in the saturated zone of the central impoundment suggest the
formation of a plume of AMD. The natural subsoil layer (silt and clay) and the bedrock surface below the tailings area were
well mapped from the ERT data. The detected fracture zones of the bedrock that could work as leakage pathways for AMD were
consistent with previous geological studies. The integrated methodology of the study offers a promising approach to fast and
reliable monitoring of areas of potential AMD generation and its subsurface movement over large areas (ca. 9 ha). This methodology
could be helpful in planning drill core sampling locations for geochemical and mineralogical analysis, groundwater sampling,
and choosing and monitoring remedial programs. 相似文献