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181.
Response of antioxidant systems to copper in the gills of the clam Ruditapes decussatus 总被引:1,自引:0,他引:1
Copper (Cu) is an essential element for biological systems, however, when present in excess, is toxic. Metallothioneins can play an important role in Cu homeostasis and detoxification. Moreover, Cu can catalyse the production of toxic hydroxyl radicals that cause lipid peroxidation but defence systems in the cells can limit the oxidative damage. The present study was performed to investigate the effect of three Cu concentrations (0.5, 2.5 and 25 microg l(-1)) on the response of antioxidant enzyme activities (superoxide dismutase (SOD), catalase (CAT), selenium-dependent glutathion peroxidase and total glutathion peroxidase), total proteins, metallothioneins (MT), malondialdehyde (MDA) concentrations in the gills of the clam, Ruditapes decussatus. The activity of antioxidant enzymes and total proteins, MT and MDA concentrations were measured in the gills of the clams after 1, 3, 7, 14, 21 and 28 days of Cu exposure. Results indicate that Cu only induces an imbalance in the oxygen metabolism during the first week of Cu exposure due to a decrease in mitochondrial SOD and CAT, selenium-dependent and total glutathion peroxidase activities. Cu also causes lipid peroxidation, measured by the MDA formation, that was Cu dependent. In the gills of clams exposed to 25 microg Cu/l, the excess of Cu triggers the induction of MT synthesis after 3 days of exposure. 相似文献
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183.
GyungNam Jo Hang S. Choi 《Oceanic Engineering, IEEE Journal of》2006,31(3):565-573
This paper discusses the problems related to constructing a receding horizon filter for underwater inertial navigation systems which are subject to external disturbances. Noises are assumed to be bounded, additive, and contained in both state and measurement equations. An estimator is designed according to the sliding-window strategy to minimize the receding horizon estimation cost function. The derived filter is applied to a velocity-aided inertial navigation system. Simulations show that the derived filter is more accurate than the standard Kalman filter (KF) for underwater navigation systems subject to temporary unknown disturbances 相似文献
184.
João Adauto Souza Neto Jean Michel Legrand Marcel Volfinger Marie-Lola Pascal Philippe Sonnet 《Mineralium Deposita》2008,43(2):185-205
The Seridó Mobile Belt (SMB) is located in the Borborema Province in northeastern Brazil and consists of a gneiss basement
(Archean to Paleo-Proterozoic), a metasedimentary sequence (marble, quartzites, and schists), and the Brasiliano igneous suite
(both of Neo-Proterozoic age). In this region, skarns occur within marble and at the marble–schist contact in the metasedimentary
sequence. Most of the skarn deposits have been discovered in the early 1940s, and since then, they have been exploited for
tungsten and locally gold. Recently, the discovery of gold in the Bonfim tungsten skarn has resulted in a better understanding
of the skarn mineralization in this region. The main characteristics of the SMB skarns are that they are dominantly oxidized
tungsten skarns, with the exception of the Itajubatiba and Bonfim gold-bearing skarns, which are reduced based on pyrrhotite
as the dominant sulfide, garnet with high almandine and spessartine component, and elevated gold contents. In the Bonfim deposit,
pressure estimates indicate that the skarns formed at 10- to 15-km depth. The mineralized skarns present the prograde stage
with almandine, diopside, anorthite, and actinolite-magnesio-hornblende, and titanite, apatite, allanite, zircon, and monazite
as accessory minerals. The retrograde stage is characterized by alkali feldspar, clinozoisite–zoisite–sericite, calcite, and
quartz. Scheelite occurs in four ore-shoots distributed within the marble and at the marble–schist contact. The main ore body
is 5–120 cm wide and contains an average of 4.8-wt.% WO3, which occurs in the basal marble–schist contact. Fold hinges appear to control the location of high-grade scheelite. The
late-stage gold mineralization contains bismite (Bi2O3), fluorine-bearing bismite, native bismuth, bismuthinite (Bi2S3), and joseite [Bi4(Te,S)3], and also chlorite, epidote, prehnite, chalcopyrite, and sphalerite. This gold–bismuth–tellurium mineralization exhibits
a typical late character and occurs as a black fine-grained mineral assemblage controlled by conjugate brittle-ductile faults
(and extensional fractures) that crosscut not only the banding in prograde skarn but also the retrograde alkali feldspar and
clinozoisite–zoisite–sericite assemblage. The Au–Bi–Te-bearing minerals are intergrown with retrograde epidote, prehnite,
chlorite, chalcopyrite, and sphalerite, indicating that gold mineralization at Bonfim is linked to a late-stage skarn event.
The polymetallic nature of the Bonfim deposit can be used as an important guide for the exploration of this type of skarn
deposit in the Borborema Province, which potentially contains significant new, undiscovered gold and polymetallic deposits. 相似文献
185.
Glen M. MacDonald Katrina A. Moser David F. Porinchu Brent B. Wolfe Amanda Petel Amalie Jo Orme 《Quaternary Research》2008,70(2):131-140
Sediment records from two lakes in the east-central Sierra Nevada, California, provide evidence of cooling and hydrological shifts during the Younger Dryas stade (YD; ~ 12,900-11,500 cal yr BP). A chironomid transfer function suggests that lake-water temperatures were depressed by 2°C to 4°C relative to maximum temperatures during the preceding Bølling-Allerød interstade (BA; ~ 14,500-12,900 cal yr BP). Diatom and stable isotope records suggest dry conditions during the latter part of the BA interstade and development of relatively moist conditions during the initiation of the YD stade, with a reversion to drier conditions later in the YD. These paleohydrological inferences correlate with similar timed changes detected in the adjacent Great Basin. Vegetation response during the YD stade includes the development of more open and xeric vegetation toward the end of the YD. The new records support linkages between the North Atlantic, the North Pacific, and widespread YD cooling in western North America, but they also suggest complex hydrological influences. Shifting hydrological conditions and relatively muted vegetation changes may explain the previous lack of evidence for the YD stade in the Sierra Nevada and the discordance in some paleohydrological and glacial records of the YD stade from the western United States. 相似文献
186.
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188.
Joël Arnault Benjamin Fersch Thomas Rummler Zhenyu Zhang Gandome Mayeul Quenum Jianhui Wei Maximilian Graf Patrick Laux Harald Kunstmann 《水文研究》2021,35(5):e14183
It is well accepted that summer precipitation can be altered by soil moisture condition. Coupled land surface – atmospheric models have been routinely used to quantify soil moisture – precipitation feedback processes. However, most of the land surface models (LSMs) assume a vertical soil water transport and neglect lateral terrestrial water flow at the surface and in the subsurface, which potentially reduces the realism of the simulated soil moisture – precipitation feedback. In this study, the contribution of lateral terrestrial water flow to summer precipitation is assessed in two different climatic regions, Europe and West Africa, for the period June–September 2008. A version of the coupled atmospheric-hydrological model WRF-Hydro with an option to tag and trace land surface evaporation in the modelled atmosphere, named WRF-Hydro-tag, is employed. An ensemble of 30 simulations with terrestrial routing and 30 simulations without terrestrial routing is generated with random realizations of turbulent energy with the stochastic kinetic energy backscatter scheme, for both Europe and West Africa. The ensemble size allows to extract random noise from continental-scale averaged modelled precipitation. It is found that lateral terrestrial water flow increases the relative contribution of land surface evaporation to precipitation by 3.6% in Europe and 5.6% in West Africa, which enhances a positive soil moisture – precipitation feedback and generates more uncertainty in modelled precipitation, as diagnosed by a slight increase in normalized ensemble spread. This study demonstrates the small but non-negligible contribution of lateral terrestrial water flow to precipitation at continental scale. 相似文献
189.
Lithospheric mantle signatures as revealed by zircon Hf isotopes of Late Triassic post‐collisional plutons from the central Korean peninsula,and their tectonic implications
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Chang‐Sik Cheong Namhoon Kim Hui Je Jo Moonsup Cho Sung Hi Choi Hongying Zhou Jian‐zhen Geng 《地学学报》2015,27(2):97-105
The Mesozoic tectonic architecture of the Korean peninsula is largely governed by the continental collision between the North and South China blocks. Zircon Hf isotopic compositions presented in this study and whole‐rock geochemical and Sr‐Nd isotope data in the literature collectively suggest that the lithophile‐elements‐enriched signature of the Late Triassic post‐collisional plutons from the Gyeonggi massif in central Korea is a primary feature inherited from the metasomatized mantle lithosphere. Highly negative zircon εHf (t) values (?23 to ?19) of plutons from the middle and eastern parts of the massif indicate an ancient metasomatism of their mantle source. Distinctly higher zircon εHf (t) values (?15 to ?12) from the southwestern plutons are ascribed to a contribution from an accreted component of the South China‐like block. The involvement of asthenospheric mantle is not recognized in zircons from either group. The implications of these isotopic features are discussed in the context of Mesozoic collisional tectonics. 相似文献
190.
Xavier Romão João Guedes Aníbal Costa Raimundo Delgado 《Bulletin of Earthquake Engineering》2008,6(2):309-333
Probabilistic seismic assessment requires extensive computational effort resulting from variability both in input ground motions
and mechanical properties. Nonetheless, such methodologies are of considerable importance, namely for pre-earthquake disaster
planning or development of retrofitting programs. A framework for the analytical definition of closed form expressions for
exceedance probabilities of structural component limit states, defined by limit values of structural response parameters,
is proposed herein. The definition of these expressions is based on the probabilistic representation of the ground motion
intensity and on the establishment of suitable expressions characterizing the evolution of structural demand with increasing
earthquake intensity. Distinction is made between deformation-based and force-based structural parameters in the definition
of such relations. Within the proposed framework, the limit states are defined by single deterministic thresholds of structural
response quantities at the component level, as defined in structural codes. Different approaches are also discussed to account
for the randomness of the mechanical properties and ground motion input within the proposed methodology. An application of
the assessment of different limit state probabilities of members from a reinforced concrete building is presented, for which
limit states and limit state capacities are defined according to the upcoming Part 3 of the Eurocode 8. Although the presented
application only deals with member chord rotation and shear force limit state probabilities, the proposed methodology can
be generalized to other deformation-based and force-based structural parameters. 相似文献