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961.
The effect of welding degree on geotechnical properties of an ignimbrite flow unit: the Bitlis castle case (eastern Turkey) 总被引:1,自引:0,他引:1
Tamer Koralay Mehmet ?zkul Halil Kumsar Sefer Beran ?elik Kadir Pekta? 《Environmental Earth Sciences》2011,64(3):869-881
Ignimbrites are associated with nearly most of the world’s volcanoes and are defined as a deposit from pyroclastic density
currents. They consist predominantly of pumiceous lapilli and blocks, and glass shards, which shows evidence of having been
emplaced as a concentrated hot and dry particulate flow. These rocks are widely used as building stone especially in ancient
buildings. Bitlis valley is covered by ignimbritic products, derived from Nemrut stratovolcano, one of the significant volcanic
centers in Eastern Anatolia. The Bitlis ignimbrite is separated into lower level (LL), middle level (ML) and upper level (UL)
according to color, welding degree and structural features. All three levels were used extensively in many parts of the Bitlis
castle as masonry materials. Studies were carried out on mineralogical and geochemical composition and on physical and mechanical
properties of the ignimbrites. In addition, a freeze–thaw cycle test was executed. There are no considerable differences in
mineralogical composition among the levels of ignimbrite. All levels contain plagioclase, sanidine, pyroxene, and opaque mineral.
In addition, anorthoclase and quartz are seen. In general, the LL of ignimbrite shows relic perlitic and eutaxitic texture,
whereas eutaxitic and vesicular texture are commonly developed in the ML and UL, respectively. Lower, middle, and upper level
ignimbrite samples display similar and limited compositional spread in terms of major oxide elements. They have trachyte composition.
Building stones can be classified according to mineralogy, mechanical and physical properties and processing types. Mechanical
and physical properties are very important with respect to stone quality/durability. The mechanical and physical properties
of the ignimbrites are controlled by the welding degree. It was found that increasing welding degree from UL to LL correlates
with increasing density, compressive strength and slake durability index and with decreasing porosity. The Bitlis ignimbrites
have turned out as susceptible to freeze–thaw cycles. 相似文献
962.
963.
Chemistry of the Ferraria thermal water, S. Miguel Island, Azores: mixing and precipitation processes 总被引:1,自引:1,他引:0
Maria do Rosário Carvalho António Mateus Jo?o C. Nunes José M. Carvalho 《Environmental Earth Sciences》2011,64(2):539-547
The Ferraria thermal water emerges at the sea level in the Ferraria lava delta (western edge of S. Miguel Island, Azores)
with temperature of ca. 60°C and pH varying between 5.4 and 6.2. It is of sodium chloride type, resulting from ca. 50% seawater
mixing with an acid brackish, at ≈100°C, denoting the presence of significant CO2(g) and the progress of water–rock interactions in open system conditions. The thermal Na–Cl water is strongly enriched with
Sr and Mn and, comparatively, has low concentrations in Al, Fe and As. These elements are removed from the solution as critical
conditions for the formation of several neo-formed mineral phases are gradually attained. Thermodynamic equilibrium calculations
are consistent with this interpretation, showing that the thermal fluid can precipitate Fe3+-(hydr-)oxides, kaolinite and non-crystalline silica. Wells logging show fracture planes and pores fully/partly filled up
with polyphase botryoidal aggregates mostly composed of goethite + ferrihydrite and displaying variable adsorbed contents
of Si, P and As. These neo-formed phases result from the pristine fluid oxidation due to seawater mixing; its precipitation
is easily affected by pH and redox variations of the brackish, due to volcanic gases pressure alterations, and fluid pressure
or flow-velocity oscillation in the fractured aquifer. 相似文献
964.
The shear band (SB) spacing phenomenon in geomaterials is addressed in this paper under plane strain extensional conditions.
On the basis of sand box observations, a method is proposed for the prediction of the spacing between shear bands based on
the so-called “bookshelf” deformation mechanism. The proposed method is based on the assumption that the material is softening
inside the shear bands whereas outside the SB it undergoes elastic unloading. The underlying assumption for the prediction
of SB spacing is that the material reaches the lowest possible energy rate. An analytical expression for the determination
of the shear band spacing is presented taking into account the plane strain extensional deformation of the specimen. The friction
due to the normal off-plane shear acting on the boundaries is then taken into account. 相似文献
965.
Norihisa?UsuiEmail author Shiro?Ishizaki Yosuke?Fujii Masafumi?Kamachi 《Journal of Oceanography》2011,67(3):253-262
We assess validity of a Gaussian error assumption, the basic assumption in data assimilation theory, and propose two kinds
of constraints regarding non-Gaussian statistics. In the mixed water region (MWR) off the east coast of Japan exhibiting complicated
frontal structures, a probability density function (PDF) of subsurface temperature shows double peaks corresponding to the
Kuroshio and Oyashio waters. The complicated frontal structures characterized by the temperature PDF sometimes cause large
innovations, bringing about a non-Gaussianity of errors. It is also revealed that assimilated results with a standard three-dimensional
variational (3DVAR) scheme have some issues in MWR, arising from the non-Gaussianity of errors. The Oyashio water sometimes
becomes unrealistically cold. The double peaks seen in the observed temperature PDF are too smoothed. To improve the assimilated
field in MWR, we introduce two kinds of constraints, J
c1 and J
c2, which model the observed temperature PDF. The constraint J
c1 prevents the unrealistically cold Oyashio water, and J
c2 intends to reproduce the double peaks. The assimilated fields are significantly improved by using these constraints. The
constraint J
c1 effectively reduces the unrealistically cold Oyashio water. The double peaks in the observed temperature PDF are successfully
reproduced by J
c2. In addition, not only subsurface temperature but also whole level temperature and salinity (T–S) fields are improved by
adopting J
c1 and J
c2 to a multivariate 3DVAR scheme with vertical coupled T–S empirical orthogonal function modes. 相似文献
966.
967.
By comparing different climatologies in El Niño decaying summer with regard to the presence of Indian Ocean Basin (IOB) warming, we studied the effect of IOB warming on the Northwest Pacific sea surface temperature (SST) anomalies and the coupling process with the surface wind. Zonal asymmetric coupling feedback in the west and east of the Northwest Pacific were caused by the asymmetric spring–summer transition of the background tropical atmospheric circulation. Although the westward wind anomaly caused by the remote effect of IOB warming is found in the whole Northwest Pacific, reversal of the mean background surface winds in the western part leads to negative wind-evaporation SST (WES), whereas sustained trade winds lead to positive WES in the eastern part. The east–west SST gradient resulting from this zonal asymmetric evolution of SST sets off more positive feedback that strengthens the local anticyclone easterly anomalies. 相似文献
968.
This study developed a post-processing quality check (QC) process to eliminate cloud contamination in infrared sea surface
temperature (SST) without manual handling. Cloudiness of a pixel was evaluated quantitatively, in which the graduated verifications
and a comprehensive decision from a combination of several tests were conducted. Additionally, the quality of SST data at
the pixel was measured by acceptable limits from reference SST, which were obtained from historical data. The QC processed
data showed good accuracy below 0.8°C, even in the near-cloud area. Before the QC, their accuracies including near-cloud areas
were as poor as 2–5°C. 相似文献
969.
Shu?WuEmail author Zhengyu?Liu Rong?Zhang Thomas?L.?Delworth 《Journal of Oceanography》2011,67(1):27-35
We studied the relationship between the dominant patterns of sea surface temperature (SST) variability in the North Pacific
and the North Atlantic. The patterns are known as the Pacific Decadal Oscillation (PDO) and the Atlantic Multi-decadal Oscillation
(AMO). In the analysis we used two different observational data sets for SST. Due to the high degree of serial correlation
in the PDO and AMO time series, various tests were carried out to assess the significance of the correlations. The results
demonstrated that the correlations are significant when the PDO leads the AMO by 1 year and when the AMO leads the PDO by
11–12 years. The possible physical processes involved are discussed, along with their potential implication for decadal prediction. 相似文献
970.
In this paper, we examined the detailed morphology of two strains of Prorocentrum isolated from the coastal waters of Zhejiang (Wenling area), China, and Masan Bay of Korea. A taxonomic comparison was made among strains on the basis of morphological and molecular data. The cellular dimensions of the Chinese Wenling strain (LAMB090508) and Korean strain (PDKS0206) were similar and the cells of both strains were of asymmetric and elongated shape. The posterior end of most cells was rounded. Megacytic zones of aged cells were broader with dense tiny knobs. The roundish nucleus was located in the posterior part of the cell. A few irregular shaped chloroplasts were distributed within the cell. The nucleotide similarity of the two strains, determined from the 5.8S rDNA-ITS sequences, was 99.83%. The comparative results of morphology and molecular analysis suggest that both strains isolated from China and Korea were the identical species, Prorocentrum donghaiense Lu. 相似文献