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121.
Are human able to foresee the future? For thou-sands of years close attention has been paid to this issue. At the present day, in order to survive from competition and to predominate over the nature, hu-man抯 desire of forecasting things has become more and more intense. Compared to conquering space, more people yearn for being able to control the time. From ancient to the present, mankind always dream of contacting the past, governing the present and tran-scending the future. Recent years in…  相似文献   
122.
桂北新元古代两类过铝花岗岩的地球化学研究   总被引:24,自引:3,他引:24  
广西北部新元古代花岗岩类岩石包括黑云母花岗闪长岩和黑云母花岗岩。地球化学特征表明,黑云母花岗闪长岩与含堇青石的过铝花岗岩(CPG)相当,而黑云母花岗岩则类似于白云母二长花岗岩(MPG)。黑云母花岗岩类是成熟地宙岩石部分熔融作用的产物,而黑云母花岗闪长岩类的形成与地幔柱起源的镁铁质岩浆和地壳起源的过铝质黑云母花岗岩浆之间的混合作用有关。这两类新元古代过铝花岗岩的形成与碰撞造山导致地壳加厚的挤压性构造无关,而与导致Rodinia超大陆裂解的地幔柱上升诱发岩石圈伸展的张性构造相联系。  相似文献   
123.
亚洲500毫巴月平均环流指数(1939—1962年)的谱分析   总被引:1,自引:0,他引:1  
李小泉  瞿栋根 《气象学报》1964,34(2):127-134
本文计算了亚洲500毫巴月平均环流指数的方差谱。结果指出:亚洲经向及纬向环流指数谱的分布是有一定差异的,前者以5个月左右为周期的谐和振动占有显著的地位,而后者则以5个月以上的长周期振动所占的成分较大。  相似文献   
124.
Glaucophane-bearing Metamorphic Rock Types of the Cazadero Area, California   总被引:1,自引:0,他引:1  
A detailed field and laboratory study has been made of a well-exposedglaucophane schist sequence within the Jurassic and CretaceousFranciscan Formation of northern California. Three types ofglaucophane-bearing metamorphic rocks have been distinguishedin and around the area of the detailed study. Each is characterizedby distinctive textures and mineral assemblages that are interpretedto represent different grades of metamorphism within the glaucophaneschist facies. From the combination of small- and large-scale mapping in thearea described it is clear that coarsely schistose blocks, tensof feet in diameter, commonly rest directly upon and withinless intensely metamorphosed terrain. In the Cazadero area theseisolated blocks of coarsely crystalline rocks are concentratedin a band that is roughly concordant with some of the majorfaulting, and their metamorphic fabric shows no consistent relationto local or regional structures. It is tentatively suggestedthat these blocks have been transported upward tectonicallyand that they are not stratigraphically equivalent to the othertypes of glaucophane-bearing metamorphic rocks in the area. Chemical and petrographic evidence indicates that basalt andsediments have been converted to glaucophane-bearing rocks underconditions of metamorphism that were essentially isochemical,except for fugitive components and some minor elements.  相似文献   
125.
The presence of a conducting environment about a spherical ore body must be considered when calculating the transient electromagnetic response of the ore body due to a step current flowing in a large circular loop at the earth's surface. Failure to do this can easily lead to errors in excess of 10% in numerical calculations. Moreover, there is only a limited time interval in which the response of the spherical conductor is easily seen. In a poorly conducting ground the resonance response of the sphere is the first to be excited. Later, however, the non-resonance or wave-type response is excited. These waves destructively interfere and finally the response of the sphere decays with time as t?7/2. For a range of times and depths the best loop for detecting the sphere has about the same radius as the sphere.  相似文献   
126.
To recognize the geographical characteristics of the landslide areas will be helpful for the watershedmanagement in the reservoir watershed. According to the quantitative analysis, we'll take differentscores and weighting for the potential parameters of the landslide areas in the Tsengwen reservoirwatershed, and in the meanwhile, we'll extract the different factors, including the slope, aspect,altitude, soil and geological textures etc., and the results shown as maximum one--day rainfall, ratio offorests and average relief is the most affecting parameters on the potential risk map of landslide areas.  相似文献   
127.
V/Sc systematics in peridotites, mid-ocean ridge basalts andarc basalts are investigated to constrain the variation of fO2in the asthenospheric mantle. V/Sc ratios are used here to ‘seethrough’ those processes that can modify barometric fO2determinations in mantle rocks and/or magmas: early fractionalcrystallization, degassing, crustal assimilation and mantlemetasomatism. Melting models are combined here with a literaturedatabase on peridotites, arc lavas and mid-ocean ridge basalts,along with new, more precise data on peridotites and selectedarc lavas. V/Sc ratios in primitive arc lavas from the Cascadesmagmatic arc are correlated with fluid-mobile elements (e.g.Ba and K), indicating that fluids may subtly influence fO2 duringmelting. However, for the most part, the average V/Sc-inferredfO2s of arc basalts, MORB and peridotites are remarkably similar(–1·25 to +0·5 log units from the FMQ buffer)and disagree with the observation that the barometric fO2s ofarc lavas are several orders of magnitude higher. These observationssuggest that the upper part of the Earth's mantle may be stronglybuffered in terms of fO2. The higher barometric fO2s of arclavas and some arc-related xenoliths may be due respectivelyto magmatic differentiation processes and to exposure to large,time-integrated fluid fluxes incurred during the long-term stabilityof the lithospheric mantle. KEY WORDS: vanadium; scandium; oxygen fugacity; mantle; arcs  相似文献   
128.
PROBABLEMAXIMUMFLOODFORDAMSAFETYASSESSMENTC.F.LEE(Formerly,ManagerofGeotechnicalandHydraulicEngineeringDepartment;ManagerofCi...  相似文献   
129.
A new deterministic technique for estimating a wavelet suggested by Loewenthal and Jakubowicz requires measurement of both pressure and vertical particle velocity. Through construction of the impedance function a deterministic estimation of the wavelet and the reflectivity can be obtained. This idea is tested for a one-dimensional model. The test is carried out by forming a synthetic seismogram of both pressure and particle velocity and checking the formulas for obtaining the estimated wavelet under noisy conditions.  相似文献   
130.
Surging of the southwestern part of the Laurentide Ice Sheet   总被引:1,自引:0,他引:1  
The southwestern part of the Laurentidc Ice Sheet, in central North America, repeatedly surged during the last part of the Wisconsin Glaciation. Evidence includes the extreme lobation of the ice margin, the gentle slopes of lateral moraines and other marginal features, a radiocarbon chronology indicating extremely rapid marginal advance and retreat, and the abundance of supraglacial flow till. Rapid ice movement was caused by subglacial water and was probably limited to areas of slowly permeable substrate, which slowed the escape of the water.  相似文献   
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