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891.
892.
Zusammenfassung Die Zweiachsigkeit von Calciten und Dolomiten wird durch Zwillingslamellen erklärt. Die Größe des Achsenwinkels hängt vom Volumenanteil der gleich orientierten Lamellen und vom Zwillingswinkel ab. Die Doppelbrechung hat nur geringen Einfluß.
Biaxial interference figures in calcite and dolomite
The biaxiality of calcites and dolomites is explained by twin lamellae. The amount of the axial angle depends from the part of volume built up by the lamellae of equal orientation, and from the twin angle. The birefringence is of minor influence.相似文献
893.
The parameters of the September 3, 1978, earthquake in the Western Caucasus are presented according to data from different seismological agencies. This event, along with the 1966 earthquake in Anapa, is the strongest seismic event in the region. The solutions suggested in the main international and national seismological agencies contradict the well-known fact that the earthquake did not have catastrophic consequences. This is confirmed only by the position of the epicenter according to GCMT data intended for determining somewhat different earthquake parameters: the focal mechanism and seismic moment. Despite the fact that there was no expedition to perform a macroseismic study of the earthquake, some information was collected by phone survey. Information on the spatial distribution of the macroseismic effect made it possible to more accurately determine the epicenter position according to the GCMT data. 相似文献
894.
The effect of biological soil crusts of different successional stages and conditions on the germination of seeds of three desert plants 总被引:1,自引:0,他引:1
Biological soil crusts greatly affect soil surface properties, which, in turn, may alter seed germination of vascular plants. We investigated the effects of two types of biological soil crusts (moss crust and algal crust) at different ages on the seed germination of Bassia dasyphylla and Artemisia ordosica. We also investigated the effects of crust conditions (living crust and dead crust) on seed germination of B. dasyphylla, A. ordosica and Eragrostis poaeoides. The presence of both algal and moss crusts significantly enhanced the germination of B. dasyphylla and A. ordosica compared with uncrusted soil. Crust age had no significant effect on the germination of either B. dasyphylla or A. ordosica for both moss and algal crusts. Germination of B. dasyphylla differed significantly between moss and algal crusts, but germination of both A. ordosica and E. poaeoides did not. Germination of A. ordosica, E. poaeoides and B. dasyphylla was significantly higher on living algal crust than on dead crust and uncrusted soil, while living moss crust enhanced the germination of both A. ordosica and B. dasyphylla but had no significant effect on E. poaeoides. 相似文献
895.
896.
Periodic Hartree-Fock STO-3G calculations have been performed on several tetracoordinated silica polymorphs: low and high quartz, low and idealized high cristobalite and prototype tridymite. The optimized structural parameters are in overall good agreement with experimental data. In the particular case of -quartz, the SiO4 tetrahedra are found to be irregular. The optimized values of the two different SiO bond lengths are respectively 1.608 Å and 1.613 Å. The potential energy versus tilt angle curves suggest a picture of the high temperature phases in terms of delocalized oxygen atoms which is consistent with a disordered structure. Finally, the bonding in silica polymorphs is discussed from electron density maps and Mulliken population analysis. 相似文献
897.
898.
The performance of a well-designed layer of sand, and composites like layer of sand mixed with shredded rubber tire(RSM) as low cost base isolators, is studied in shake table tests in the laboratory. The building foundation is modeled by a 200 mm by 200 mm and 40 mm thick rigid plexi-glass block. The block is placed in the middle of a 1m by 1m tank filled with sand. The selected base isolator is placed between the block and the sand foundation. Accelerometers are placed on top of the footing and foundation sand layer. The displacement of the footing is also measured by LVDT. The whole setup is mounted on a shake table and subjected to sinusoidal motions with varying amplitude and frequency. Sand is found to be effective only at very high amplitude( 0.65 g) of motions. The performance of a composite consisting of sand and 50% shredded rubber tire placed under the footing is found to be most promising as a low-cost effective base isolator. 相似文献
899.
R. S. Bortkovskii B. N. Egorov V. M. Kattsov T. V. Pavlova 《Izvestiya Atmospheric and Oceanic Physics》2007,43(3):378-383
Annual mean fluxes of CO2 and oxygen across the sea surface are estimated with the use of numerical modeling for several regions located in the Gulf Stream and Kuroshio zones. The present-day climatic conditions and the climatic conditions expected in the middle and at the end of the 21st century are considered. Specific features of gas exchange under a strong wind that are associated with gas exchange by bubbles and with changes in the air-water difference of the gas concentrations were taken into account in the calculations. The estimates obtained differ substantially from the results based on the traditional approach, which disregards the above features. A considerable increase in the absorption of CO2 by the ocean, which is mainly caused by the continuing increase in the CO2 concentration in the air during its small changes in the ocean, is expected in the 21st century. At the same time, no trends are revealed in the annual mean fluxes of oxygen across the ocean surface. The conclusion is made that, in calculations of CO2 absorption by the world ocean, it is necessary to take into account both specific features of gas transfer under a strong wind and an increase in the atmospheric concentration of CO2. 相似文献
900.
V. I. Vedernikov V. G. Bondur M. E. Vinogradov M. R. Landry M. N. Tsidilina 《Oceanology》2007,47(2):221-237
The anthropogenic impact on the biomass of coastal plankton communities caused by submerged disposal of urban sewage waters (dumping) was studied. The observations were carried out in August–September of 2002–2004 in Mamala Bay (Oahu Island, Hawaii) using satellite and sea truth methods. An analysis of the variability of the integral indicators of the water column determined on the basis of shipborne measurements allowed us to divide them into two groups: the elements most sensitive to the pollution (heterotrophic bacteria (H-Bact), the phototrophic cyanobacteria Synechococcus spp. (SYN), and chlorophyll a (CHLa)) and the elements that manifested episodic positive dependence on the inflow of the polluted waters (heterotrophic unicellular eukaryotes, small unicellular algae, the phototrophic green bacteria Prochlorococcus spp., as well as the total biomass of microplankton). It was shown that the submerged wastewater disposal in the region of the diffuser of the dumping device led to an insignificant (1.2–1.4 times, on the average) local increase in the integral biomass of H-Bact, SYN, and in the content of CHLa. A similar but sharper (1.5–2.1, on the average) increase in these parameters was found in the water layers with maximal biomasses. The possible pathways of disposed waters (under the pycnocline, at its upper boundary, and in the entire mixed layer) were analyzed on the basis of studying the vertical displacement of the biomasses of H-Bact, SYN, and prochlorophytes. The possibility of using the optical anomalies distinguished from satellite data as markers of anthropogenic eutrophication caused by dumping was confirmed. Application of such markers depends on the water transparency and on the shapes of the curves of the vertical distribution of autotrophic organisms. 相似文献