首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   782篇
  免费   1篇
  国内免费   4篇
测绘学   4篇
大气科学   31篇
地球物理   132篇
地质学   277篇
海洋学   151篇
天文学   175篇
自然地理   17篇
  2022年   13篇
  2021年   20篇
  2020年   21篇
  2019年   28篇
  2018年   59篇
  2017年   25篇
  2016年   32篇
  2015年   12篇
  2014年   27篇
  2013年   51篇
  2012年   47篇
  2011年   46篇
  2010年   36篇
  2009年   30篇
  2008年   35篇
  2007年   46篇
  2006年   33篇
  2005年   13篇
  2004年   20篇
  2003年   19篇
  2002年   16篇
  2001年   14篇
  2000年   6篇
  1999年   8篇
  1998年   10篇
  1997年   9篇
  1996年   6篇
  1995年   7篇
  1994年   5篇
  1993年   3篇
  1992年   4篇
  1991年   3篇
  1990年   8篇
  1989年   5篇
  1987年   6篇
  1986年   4篇
  1985年   4篇
  1984年   4篇
  1983年   6篇
  1981年   4篇
  1980年   2篇
  1978年   2篇
  1977年   5篇
  1976年   4篇
  1974年   4篇
  1973年   3篇
  1972年   4篇
  1970年   3篇
  1966年   2篇
  1965年   3篇
排序方式: 共有787条查询结果,搜索用时 15 毫秒
711.
Four models used for evaluating the height of the evaporation duct from measured atmospheric pressure, water and air temperatures, and air humidity are considered.The calculated results are compared with the duct heights measured during two oceanographic expeditions in the tropical zone of the Atlantic Ocean and the equatorial zone of the Indian Ocean. The sensitivity of models to the errors in the meteorological parameters is investigated. It is shown that, in the case of unstable stratification, the heights of ducts in the 5–20-m range can be evaluated with an error of about 2.5 m. Recommendations for selection of optimal models are given.  相似文献   
712.
713.
The data accumulated by a measuring complex equipped with a gradient-distributed temperature sensor in the course of towing in the shelf zone near the South Coast of the Crimea and in the region where the flow of the Rim Current crosses the shelf edge are used to analyze the energy and space characteristics of internal waves formed when the flow runs through the shelf edge and to study the process of their propagation both to the coast and to the open part of the sea.  相似文献   
714.
We propose a new method for the evaluation of the velocities of surface currents according to the data of measurements carried out by using high-frequency land-based radars. The method is based on the representation of the velocity fields via two scalar potentials, expansion of these potentials in series in basis functions, and determination of the coefficients of expansion according to the data of radar measurements as solutions of the corresponding variational problems. The errors of the procedure of determination of the coefficients of expansion are removed by using a special regularization procedure based on information theory. The proposed method enables one to fill gaps in the space and time series of radar measurements. We illustrate the method by an example of numerical analysis of mesoscale and submesoscale (10–50 km) surface currents in the Monterey Bay (California, USA) performed on the basis of the data of radar measurements carried out in August 1994. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 2, pp. 24–36, March–April, 2005.  相似文献   
715.
Hydrocarbon gases were determined in sediments from three mud volcanoes in the Sorokin Trough. In comparison to a reference station outside the mud volcano area, the deposits are characterized by an enrichment of high-molecular hydrocarbons (C2–C4), an absence of unsaturated homologues, a predominance of iso-butane in comparison with n-butane, and the presence of gas hydrate. The molecular composition of the hydrocarbon gases suggests their deep sources and thermogenic origin. In the pelagic sediments at the reference station, the methane concentration is relatively low (up to 49 ml/l); maximum concentrations are reached in deposits of the Dvurechenskii mud volcano (up to 400 ml/l). It was the first time that gas hydrate was sampled at the Dvurechenskii mud volcano. The gas extracted by dissociation of hydrate samples was dominated by methane (99.5%) with low amounts of ethane and propane (less than 0.5%). The isotopic composition of the methane varies between –62 and –66 PDB in 13C, and between –185 and –209 SMOW in D, indicating a mainly biogenic origin with an admixture of thermogenic gas.  相似文献   
716.
Coupled modeling of currents and wind waves in the Kerch Strait   总被引:1,自引:0,他引:1  
We present a numerical model of the dynamics of the Kerch Strait allowing one to perform the coordinated analysis of the fields of currents and wind waves. The model includes the spectral wave module and the hydrodynamic block of currents. The influence of waves on the currents is taken into account in the hydrodynamic block both via the surface and bottom tangential stresses and via the radiation stresses. In order to take into account the inverse influence of currents upon the waves, we use the fields of currents and sea level from the hydrodynamic block in the wave module. The specific features of the structure of currents and wind waves in the strait are studied for the typical wave situations. The results of the coupled and separate simulation are compared and the importance of taking into account the mechanisms of interaction between waves and currents in the analysis of the dynamic processes in the strait is demonstrated. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 5, pp. 3–20, September–October, 2007.  相似文献   
717.
Late Cenozoic lavas from the western wall of the Khubsugul rift trough were erupted within the Tuva-Mongolian Massif with a pre-Vendian basement, and the lavas in the eastern wall of the trough were erupted within Early Caledonian terranes. The composition of the lavas was determined to vary across the strike of the boundary of the Tuva-Mongolian Massif. The western wall of the trough is dominated by hawaiites and contains subordinate volumes of basanites and much lower amounts of olivine tholeiites and basaltic trachyandesites. The eastern wall contains, in addition to hawaiites, widespread olivine tholeiites and basaltic andesites with subordinate amounts of basaltic trachyandesites. The boundary zone contains practically all rock types (except basaltic andesites) in roughly equal proportions. The trace-element simulations of the partial melting processes demonstrates that the basaltic magmas were produced mainly by 0.5–5% partial melting of garnet lherzolite, with the probable mixing with partial melts derived from spinel lherzolite. The main factor controlling the compositional variations of the lavas was likely the variable depths of their derivation due to variations in the lithosphere thickness at the boundary of the Tuva-Mongolian Massif. Based on the assumption that the source of the magmas was relatively homogeneous and on the results of simulations with the use of experimental data on peridotite melting, we concluded that the asthenospheric sources of the basaltic magmas occurred at depths of 75 ± 10 km (24.6 ± 3.2 kbar) beneath the Tuva-Mongolian Massif and at 60 ± 12 km (20.1 ± 3.8 kbar) beneath the Early Caledonian terranes.  相似文献   
718.
In the Triassic siliceous formation of Sikhote Alin, carbonaceous silicites occur in the late Olenekian-middle Anisian member (4–20 m) of alternating cherts and clayey cherts (“phtanite member”) near the section base. The silicites are represented by radiolarian and spicule-radiolarian cherts alternating with clayey cherts. They contain up to 8.5% Corg. In the majority of sections, the rocks underwent structural and mineral transformation at the mesocatagenetic stage. The slightly oxidized organic (primarily, marine sapropelic) matter contains quinones, methyl, methylene, and ether groups. The content of neutral bitumens in rocks shows a wide variation range. The carbon isotopic composition in phtanites and clayey phtanites (δ13C from ?27.3 to ?30.2‰) is identical to that in many Paleozoic-Mesozoic bitumens and oils. As compared with other Mesozoic sedimentary rocks of Sikhote Alin, the carbonaceous silicites are enriched in V, B, Mo, Ni, Cu, and Ag. Anomalously high concentrations of Ba are recorded in phtanite rock sections at the Gornaya and Khor rivers and in the vicinity of Khabarovsk. Modal value of the Au content in phtanites and clayey phtanites is three or four times higher than the clarke value in carbonaceous silicites and reaches anomalous values in some sections (e.g., Ogorodnaya River section). Carbonaceous silicites of this section are also enriched in Pt. Positive Au-Corg correlation is recorded in clayey phtanites of the Ogorodnaya River section containing more than 0.5% Corg. In organic fractions, Au and Ag are concentrated in alcohol and alcohol-benzene bitumens, asphalt acids, and asphaltenes. Migration of bitumens from high-carbonaceous clayey phtanites to the pore-fissure space of cherts and phtanites also fostered the concentration of these metals in some low-carbonaceous layers of the member.  相似文献   
719.
The work is dedicated to multidisciplinary study of Upper Cretaceous deposits exposed at the day surface in a ravine near the village of Vishnevoe, the Petrovsk district of Saratov oblast. The exposed section includes deposits of the Bannovka, Mozzhevelovyi Ovrag, Mesino-Lapshinovka, Rybushka, Ardym, Lokh formations and of the Borisoglebsk sequence first distinguished in the Volga River basin. Age ranges of the formations studied are confirmed or defined more precisely (the Ardym and Lokh formations) based on fossil faunas of cephalopods, bivalves, radiolarians, planktonic and benthic foraminifers. The middle-upper Coniacian range of the Borisoglebsk sequence is substantiated. Distribution of brachiopods, sponges, radiolarians, ostracodes and calcareous nannoplankton in the section is established. Radiolarian assemblages are used to distinguish biostratigraphic subdivisions corresponding in rank to faunal beds. Based on nannofossil assemblages, zones and subzones of standard zonations after Perch-Nielsen (1985) and Burnett (1998) are established. Stratigraphic ranges of certain radiolarian, ostracode and calcareous nannoplankton taxa are verified.  相似文献   
720.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号