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951.
Evangelos P. Tziritis 《Environmental Earth Sciences》2010,60(7):1381-1390
Kopaida plain is a cultivated region of Eastern Greece, with specific characteristic related with the paleogeographic evolution
and the changes in land use. The present article examines the contamination that derives from nitrates, in terms of contaminant
levels, definition of sources and spatial distribution of contaminant plume. For this purpose, 50 water samples were collected
from the karstic aquifer and analyzed for 15 parameters including major ions, trace elements, physicochemical parameters,
and stable isotopes. The assessment of the above parameter values along with the notes derived by the statistical process
revealed the existence of nitrate contamination which has been spatial defined with the aid of spatial interpolation techniques.
The correlation of NO3
− concentrations with the stable isotope values, defined the infiltration conditions and showed contaminant transport. Nitrate
values revealed the potential environmental threat for local people, as 10% of the samples exceeded the parametric value of
50 ppm and 54% of them are above 25 ppm, indicating no optimal quality conditions. The origin of nitrate contamination seems
to derive exclusively from the application of N-fertilizers, since the rest of potential sources were not verified by analytical
data and field works. 相似文献
952.
953.
A sequence of mineral associations was examined in eclogitized basites of the Krasnaya Guba dike field in the Belomorian Mobile
Belt. Two morphological types of eclogite and eclogite-like rocks were recognized: (1) eclogite rocks that developed after
ferrogabbro dikes and completely replaced these dikes from contact to contact and (2) eclogite-like rocks that developed after
gabbronorites in zones of ductile deformations and shearing. According to data mineral geothermobaromety, both rock types
were formed within temperature and pressure ranges corresponding to high-pressure and high-temperature amphibolite facies
at T = 700 ± 40°C and P = 10.0 ± 0.5 kbar. The peak metamorphic parameters of the host gneisses are analogous. The decompressional stage, which is
unambiguously identified by reaction textures, occurred at 630–660°C and 7.9–8.2 kbar. As the temperature and, first of all,
pressure decreased, the SiO2 activity in the fluid systematically varied. The eclogitization of the basites took place locally in relation to fluid fluxes,
which were restricted to zones of intense deformations, at variable SiO2 activity. The rocks show evidence of two stages of post-eclogite amphibolization. Older amphibolization 1 was coeval with
the late prograde metamorphic stage (T = 650°C, P = 10–11 kbar). Younger amphibolization 2 affected eclogitized basite dikes and unaltered gabbronorites (together with their
host gneisses) over large areas. This process coincided with decompression (T = 580°C, P = 7–8 kbar) and was likely accompanied by the exhumation of deep zones of BMB to upper-middle crustal levels. 相似文献
954.
955.
This paper reports REE data on resin-asphaltene components of oil from six oil-gas-bearing provinces and on bitumoids from
inferred oil-source rocks (domanikites and bazhenites). It was shown that, regardless of geological-tectonic structure of
the regions, oil composition, depth of reservoirs, and host lithologies, oil exhibits significant REE fractionation, and,
unlike bitumoids, positive Eu anomaly. The (Eu/Sm)n ratio increases from asphaltenes to resins and further to oils. Based on REE distribution in oil, source rocks, and bitumoids,
it was concluded that deep-seated fluids were one of the possible sources that defined the trace element composition of oil. 相似文献
956.
957.
U-Th-Pb systematics of precambrian carbonate rocks: Dating of the formation and transformation of carbonate sediments 总被引:1,自引:0,他引:1
O. K. Kaurova G. V. Ovchinnikova I. M. Gorokhov 《Stratigraphy and Geological Correlation》2010,18(3):252-268
The current state in the Pb-Pb dating of the formation and epigenesis of Precambrian carbonate sediments has been reviewed.
The geochemistry of admixture elements (U, Th, Pb, Rb, Sr, Mn, and Fe) constituting carbonate minerals and the redistribution
of the elements in the course of early diagenesis and epigenesis have been considered. The advantages of choosing samples
for Pb-Pb dating on the basis of geochemical criteria similar to those applied for Sr-isotope stratigraphy and the potentialities
of applying different methods of decontamination of specimens, analyzed from surface contamination and possible epigenetic
carbonate phases, were illustrated. By the example of a series of carbonate formations, distinctions in susceptibility of
U-Pb and Rb-Sr systems of carbonate minerals to secondary transformations have been demonstrated. The prospects for using
the method of step solution allowing noncogenetic carbonate generations to be separated and thus the accuracy and reliability
of Pb-Pb dates to be upgraded were considered. 相似文献
958.
G. G. Msilimba 《Natural Hazards》2010,53(2):347-360
Despite the occurrence of fatal landslides in Malawi, literature is not available on their socio-economic and environmental
effects. Limited or no research is being carried out in this area except for technical reports commissioned by the government.
Landsliding does not appear on the ten environmental concerns affecting the nation. This paper attempts to examine the socio-economic
and environmental effects of landslides that struck parts of Ntcheu district of central Malawi and Rumphi district of northern
Malawi in 2003. This paper asserts that poor rural people are more vulnerable to landslides and their resilience is low. Unsustainable
production systems, inappropriate location of settlements, low incomes coupled with lack of government support aggravates
the situation. Mitigation measures, which were in conflict with people’s production systems, prevented them from participating
in the rehabilitation of the areas. Lack of support from government for the reconstruction and regeneration of local production
had economic effects such as loss of livelihood, unemployment, decreased productivity and out migration to urban centers.
The study recommends the participation of all stakeholders in reducing the impacts of landslides and the development of disaster
management plans to achieve timely response to landslide hazards. 相似文献
959.
Government policies intended to reduce flood losses can increase the potential for catastrophe by stimulating development
inside the floodplain, a phenomenon referred to as the “safe development paradox.” New Urbanist design has the potential to
both exacerbate and alleviate flood risks. Because they are built at relatively high densities, New Urbanist developments
can exacerbate risk by placing more people and property in harm’s way. Conversely, New Urbanist design features theoretically
better enable designers of New Urbanist developments to avoid floodplain portions of project sites than designers of conventional
subdivisions. Using a sample of New Urbanist developments in the US that contain floodplain portions within their boundaries,
this paper focuses on whether and why these developments locate built structures inside the floodplain. The authors find that
roughly 30% of the developments locate structures inside the floodplain, and that the odds of locating structures inside the
floodplain increase with the proportion of the project site located inside the floodplain and decrease with the presence of
government policies that prohibit residential development in the floodplain. The authors also identify confusion among government
planners regarding the distinction between pre and postconstruction floodplain boundaries. A subset of New Urbanist developments
is found to have built structures located outside the postconstruction floodplain boundary, but inside the preconstruction
floodplain boundary. This finding is cited as an example of the “safe development paradox” in action. The authors recommend
changes in New Urbanist design codes and local government floodplain management to increasingly direct new development away
from the floodplain. 相似文献
960.
E. A. Avvakumova 《Astronomy Reports》2010,54(1):17-27
We searched for signs of the presence of circumstellar gaseous matter in photometric data for massive contact early-type binaries
by analyzing residual curves (the dependence of the difference between the observed and theoretical brightness variations
on the orbital-period phase) for three such stars. The residual curves make it possible to estimate the influence of gas in
the common envelope on the observed light curves for different phase intervals and to qualitatively describe the character
of the distortion of the light from the system’s components. Changes of the residual curves from filter to filter indicate
varying conditions in the circumstellar matter. Changes of the residual curves from one observation epoch to another indicate
varying conditions in the circumstellar matter. We compared the residual curves obtained for different photometric bands and
epochs via a correlation analysis. The distortion of light from the components of LY Aurigae in the ultraviolet differs from
that in the visual. The distortion of light from the components of SV Centauri is appreciable, but not selective, and does
not vary in time, while the distortion of light from BH Centauri possesses a strong selective component. A comparison of the
radii computed for the components of BH Centauri and SV Centauri shows that the gas distribution near these binaries varies
in time. 相似文献