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151.
Frank E. Senftle Arthur N. Thorpe Charles Briggs Corrine Alexander Jean Minkin David L. Griscom 《Earth and Planetary Science Letters》1975,26(3):377-386
The magnetic susceptibility of a terrestrial, synthetic and lunar ilmenite specimen has been measured from 4 to 300 K. All specimens had a single Néel temperature transition which ranged from 56 to 57.7 K. In one case the powdered specimen was partially aligned in the magnetic field prior to the susceptibility measurements and the Néel transition was observed to shift to 60 K indicating magnetic anisotropy. A study of several magnetic parameters calculated from the experimental data showed gross impurities in the terrestrial specimen, single-domain to multi-domain metallic iron in the synthetic specimen, and a small amount of superparamagnetic metallic iron in the lunar sample. No multidomain iron was observed in the lunar ilmenite. The results of electron spin resonance measurements were also in general agreement with these findings. Because of the absence of Fe3+ compared to most terrestrial samples it is suggested that the anisotropic magnetic parameters be determined on lunar ilmenite when a large enough single crystal becomes available. 相似文献
152.
Frank S. Spear 《Contributions to Mineralogy and Petrology》1980,72(1):33-41
The exchange equilibrium between plagioclase and amphibole, 2 albite+tschermakite=2 anorthite+glaucophane, has been calibrated empirically using data from natural amphibolites. The partition coefficient, K
D, for the exchange reaction is (X
an/X
ab)plag ·(Na, M4/Ca, M4)amph.. Partitioning is systematic between plagioclase and amphibole in suites collected from single exposures, but the solid solutions are highly non-ideal: values of In K
D range from –3.0 at X
an=0.30 to –1.0 at X
an=0.90 in samples from a single roadcut. Changes in both K
D and the topology of the ternary reciprocal exchange diagram occur with increasing metamorphic grade. Temperature dependence of In K
D is moderate with ¯H35 to 47 kcal at X
an=0.25; pressure dependence is small with ¯V –0.24 cal/bar. Usefulness of this exchange equilibrium as a geothermometer is restricted by uncertainties in the calculation of the amphibole formula from a microprobe analysis, especially with regard to Na, M4 in amphibole, to approximately ±50 ° C. 相似文献
153.
A number of experimental CO2 solubility data for silicate and aluminosilicate melts at a variety of P- T conditions are consistent with solution of CO2 in the melt by polymer condensation reactions such as SiO 4(m 4? +CO2(v)+Si n O 3n+1(m) (2n+1) ?Si n+1O 3n+4(m) (2n+4)? +CO 3(m )2? . For various metalsilicate systems the relative solubility of CO2 should depend markedly on the relative Gibbs free change of reaction. Experimental solubility data for the systems Li2O-SiO2, Na2O-SiO2, K2O-SiO2, CaO-SiO2, MgO-SiO2 and other aluminosilicate melts are in complete accord with predictions based on Gibbs Free energies of model polycondesation reactions. A rigorous thermodynamic treatment of published P- T-wt.% CO2 solubility data for a number of mineral and natural melts suggests that for the reaction CO2(m) ? CO2(v)
- CO2-melt mixing may be considered ideal (i.e., { \(a_{{\text{CO}}_{\text{2}} }^m = X_{{\text{CO}}_{\text{2}} }^m \) );
- \(\bar V_{{\text{CO}}_{\text{2}} }^m \) , the partial molal volume of CO2 in the melt, is approximately equal to 30 cm3 mole?1 and independent of P and T;
- Δ C p 0 is approximately equal to zero in the T range 1,400° to 1,650 °C and
- enthalpies and entropies of the dissolution reaction depend on the ratio of network modifiers to network builders in the melt. Analytic expressions which relate the CO2 content of a melt to P, T, and \(f_{{\text{CO}}_{\text{2}} } \) for andesite, tholeiite and olivine melilite melts of the form
154.
Transposed Climates for Study of Water Supply Variability on the Laurentian Great Lakes 总被引:2,自引:0,他引:2
Kenneth E. Kunkel Stanley A. Changnon Thomas E. Croley II Frank H. Quinn 《Climatic change》1998,38(4):387-404
Hydrological models of the Great Lakes basin were used to study the sensitivity of Great Lakes water supplies to climate warming by driving them with meteorological data from four U.S. climate zones that were transposed to the basin. Widely different existing climates were selected for transposition in order to identify thresholds of change where major impacts on water supplies begin to occur and whether there are non-linear responses in the system. The climate zones each consist of 43 years of daily temperature and precipitation data for 1,000 or more stations and daily evaporation-related variables (temperature, wind speed, humidity, cloud cover) for approximately 20–35 stations. A key characteristic of these selected climates was much larger variability in inter-annual precipitation than currently experienced over the Great Lakes. Climate data were adjusted to simulate lake effects; however, a comparison of hydrologic results with and without lake effects showed that there was only minor effects on water supplies. 相似文献
155.
The second order theory of elasticity, in which terms to second order in strain are retained in calculating atomic bond length changes and elastic moduli, is extended to describe thermal vibration of a face-centred cubic crystal. Coupled with equations relating the pressure dependences of elastic constants, this yields a new formulation of the thermal Grüneisen parameter γ in terms of pressure P, incompressibility K and rigidity, μ where f = 24 (3 K ? 2 P)/(3 K + 115 μ + 90 P). The factor f arises from bond interactions and the case f = 1, representing independent bonds (no interactions), yields the free-volume γ- Since we have shown earlier that the second order elasticity theory provides a convincing explanation of the elasticity of the inner core, we believe that the new formula is appropriate for the inner core. It is, however, inadequate to describe the lower mantle γ, in which atomic bond angle rigidity, not considered here, may be appreciable. 相似文献
156.
The Fuscaldo assemblages show that in metabasites suitable for the production of glaucophane at higher pressures, amphibole poor(er) in Gl-molecule + albite + Al-rich chlorite is formed at lower pressure. Blue amphibole formed together with albite, chlorite and a Ca-silicate appears to have a fixed content of the Gl-molecule and of Ca2+, apart from the Fe2+/ R2+ ratio, which varies with host rock chemistry. The constant Gl-content indicates attainment of equilibrium, and is a function of T and especially P, so it may be used as a geobarometer. Glaucophane generally forms at the cost of albite+chlorite. In a P-T diagram the reaction is probably situated somewhat below the reaction albitejadeite+quartz, and has a smaller slope than the latter. The concomitant high-pressure character of glaucophane justifies reintroduction of Eskola's glaucophane-schist facies, of which glaucophane is critical. 相似文献
157.
Ge Verver Frank Raes Daan Vogelezang Doug Johnson 《Tellus. Series B, Chemical and physical meteorology》2000,52(2):126-140
A review is given of the climatological and actual meteorological conditions in the sub‐tropical northeast Atlantic, during June–July 1997, when the 2nd Aerosol Characterization Experiment (ACE‐2) took place. Surface pressure maps, trajectory calculations and in‐situ measurements show how the outflow of European pollution into the marine boundary layer of this area is determined by the location of the Azores high pressure cell. Observations during ACE‐2 and 3 preceding summers show that pollution outbreaks both from the Iberian peninsula and from northern or central Europe can occur during such situations. During ACE‐2, an unusually low number of strong North African dust outbreaks were recorded at the free tropospheric station of Izaña (Tenerife, 2360 m asl), although dust was recorded aloft the station. 相似文献
158.
David J. Ampleford Andrea Ciardi Sergey V. Lebedev Simon N. Bland Simon C. Bott Jeremy P. Chittenden Gareth N. Hall Adam Frank Eric Blackman 《Astrophysics and Space Science》2007,307(1-3):29-34
We present experimental data on the steady state deflection of a highly supersonic jet by a side-wind in the laboratory. The
use of a long interaction region enables internal shocks to fully cross the jet, leading to the development of significantly
more structure in the jet than in previous work with a similar setup (Lebedev et al., 2004). The ability to control the length
of the interaction region in the laboratory allows the switch between a regime representing a clumpy jet or wind and a regime
similar to a slowly varying mass loss rate. The results indicate that multiple internal oblique shocks develop in the jet
and the possible formation of a second working surface as the jet attempts to tunnel through the ambient medium. 相似文献
159.
Frank Press 《地震地质》2000,22(2):103
我想根据自己的经历回顾过去 4 0年来美国科学的发展 ,我有幸在这个时期中成长为一名地球物理学家。这个时期被称为科学的黄金时代 ,因为在基础科学和工程科学中有大量发现和进展。在这个时期 ,不仅有伟大的创造和充足的资金支持 ,还获得了很多新知识 ,正是这些知识产生了新的工业并使我们增加了对环境的理解。对于地球物理学 ,正是在这个时期使用现代技术对海底进行了勘测 ,建立了全球地震台网 ,用实验室实验模拟深部地球环境 ,将示踪元素化学应用于岩石系统。也是在这个时期 ,对其它行星做了探测并从月球取回了岩样 ,创立了板块构造理论。在其它领域也有巨大进展 ,如分子生物学与疾病性质研究 ,以及农业绿色革命等。许多科学家在开始自己的研究时 ,并未想到后来会有那么多的创效益应用。许多年轻的科学家不珍惜美国科学尤其是地球物理学的繁荣。在四十年代以前 ,美国有较强的技术和工业生产优势 ,但在科学方面不如西欧 ,类似于现在的日本。那时基础研究主要在得到私人慈善机构支持的大学以及少数政府机构和工业实验室中进行。例如州立大学和地质调查局承担了地质填图 ,一些石油公司实验室开拓了勘探地球物理。除了地学外 ,政府对基础科学的资助很少。那时世 相似文献
160.
Axel D. Schwope Valeri Hambaryan Frank Haberl Christian Motch 《Astrophysics and Space Science》2007,308(1-4):619-623
We present a first analysis of a deep X-ray spectrum of the isolated neutron star RBS1223 obtained with XMM-Newton. Spectral
data from four new monitoring observations in 2005/2006 were combined with archival observations obtained in 2003 and 2004
to form a spin-phase averaged spectrum containing 290 000 EPIC-pn photons. This spectrum shows higher complexity than its
predecessors, and can be parameterised with two Gaussian absorption lines superimposed on a blackbody. The line centers, E
2≃2E
1, could be regarded as supporting the cyclotron interpretation of the absorption features in a field B∼4×1013 G. The flux ratio of those lines does not support this interpretation. Hence, either feature might be of truly atomic origin.
相似文献