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961.
Very high concentrations of Zn, Pb, Cu and Cd occur in the muddy bottom sediments of Lake Macquarie, a saline coastal lagoon in southeastern Australia. The trace metals emanate from industrial sources, especially a lead-zinc smelter, at the northern end of the lake. Individual metal concentrations decrease progressively away from the source area but at differing rates; Zn is most mobile and Cd appears to be deposited first. They approach natural background levels in the southern part of the lake. Mn shows a reverse trend but Ni, Co, Ag and Fe rarely rise above background levels.Shallow cores in the lake bed penetrated a metal enriched surface zone 15–35 cm thick underlain by uncontaminated sediments with natural (background) metal concentrations. Sedimentation rates determined from radiocarbon ages on shells in the cores mainly range between 0·15 and 0·5 mm yr?1. Over the 85 years since industrialization commenced, less than 5 cm of mud has accumulated on the lake bed. Bioturbation is invoked to account for the depth to which the sediment has been enriched in heavy metals.  相似文献   
962.
The known history of the solar system is discussed, also the types of dynamical problems exhibited by members of the solar system and the solutions suggested for a number of such problems. The recent work of Walker, Emslie and Roy, on Empirical Stability Criteria in Many Body Problems is also mentioned.Paper presented at the European Workshop on Planetary Sciences, organised by the Laboratorio di Astrofisica Spaziale di Frascati, and held between April 23–27, 1979, at the Accademia Nazionale del Lincei in Rome, Italy.  相似文献   
963.
Samples of vitrified and unvitrified Eocene woody plant tissues collected from the Fossil Forest site, Geodetic Hills, Axel Heiberg Island, have been characterized by TMAH thermochemolysis. All samples are gymnosperm-derived, are of very low maturity and all share the same post-depositional geologic history. Differences in the distributions of products observed from vitrified and unvitrified samples suggest that vitrification of woody tissue is associated with modification of the lignin C3 side chain, following loss of all or most of the carbohydrate present in the precursor woody tissues. The key driver of vitrification appears to be physical compression of the tissue following biological removal of cellulosic materials.  相似文献   
964.
The earthquake is known to be an unpredictable geophysical phenomenon. Only few seismic indicators and assumptions of earthquakes can be predicted with probable certainty. This study attempts to analyze the earthquakes over the Indo-Himalayan Border region including Bhutan, Bangladesh, Nepal, China and India during the period from 1995 to 2015. Bangladesh, Bhutan and China borders experience fewer earthquakes than Nepal and India border regions. However, Indo-China rim has inconsistency and vast range in its magnitude. Bangladesh though is a small country with respect to others, but it experiences earthquakes comparable to Bhutan. Nepal experiences highest number of earthquakes. In the last 20 years around 800 records have been observed with moment magnitude > 4.0 Richter scale, while very few records (around 10–12) have been observed for large earthquakes having moment magnitude > 6.0 Richter scale over the region. In this study adaptive neuro-fuzzy inference system has been implemented to assess the predictability of seismic moment associated with large earthquakes having the moment magnitude between 6.0 and 8.0 Richter scales using different combination of epochs, technique and membership functions. The Gaussian membership function with hybrid technique and 40 epochs is observed to be the reasonable model on the basis of the selected spatial and temporal scale. The forecast error in terms of root-mean-square error with the stopping criterion 0.001 has been observed to be 0.006 in case of large earthquakes (> 6.5 Richter scale), that is, forecast accuracy of 99.4%. The model bias of 0.6% may be due to inadequate number of large earthquakes having moment magnitude > 6.5 Richter scale over the region.  相似文献   
965.
The spatial–temporal patterns of cloud-to-ground (CG) lightning covering the period 2010–2015 over the northwest Iberian Peninsula were investigated. The analysis conducted employed three main methods: the circulation weather types developed by Jenkinson and Collison, the fit of a generalized additive model (GAM) for geographic variables, and the use of a concentration index for the ratio of lightning strikes and thunderstorm days. The main activity in the summer months can be attributed to situations with eastern or anticyclonic flow due to convection by insolation. In winter, lightning proves to have a frontal origin and is mainly associated with western or cyclonic flow situations which occur with advections of air masses of maritime origin. The largest number of CG discharges occurs under eastern flow and their hybrids with anticyclonic situations. Thunderstorms with greater CG lightning activity, highlighted by a higher concentration index, are located in areas with a higher density of lightning strikes, above all in mountainous areas away from the sea. The modeling of lightning density with geographic variables shows the positive influence of altitude and, particularly, distance to the sea, with nonlinear relationships due to the complex orography of the region. Likewise, areas with convex topography receive more lightning strikes than concave ones, a relation which has been demonstrated for the first time from a GAM.  相似文献   
966.
To a practicing foundation engineer, the performance of batter pile under seismic conditions still remains a questionable prospect. The contradictory findings reported by various investigators with regard to the performance of batter piles add to this dilemma. This calls for a rigorous three-dimensional investigation to evaluate seismic behavior of batter pile groups. In this study, a comparative assessment of three-dimensional seismic behavior of a 2 × 2 vertical and batter pile groups having batter angle of 15° was carried out using a full three-dimensional finite element code developed in MATLAB (Sarkar 2009). The effects of centre to centre spacing of piles and soil modulus values were investigated. Idealized soil profiles having constant and triangular variation of soil modulus were adopted for the study. Results of analyses for both the vertical and batter pile groups are presented in terms of dynamic stiffness and kinematic interaction factors. Results indicate better seismic performance of batter pile groups in comparison to that of vertical pile groups. To demonstrate the importance of the findings, a five-storied portal frame structure supported separately on vertical and batter pile groups were considered and analyzed for El-Centro Earthquake (1940) time history. The difference in structural response considering vertical and batter pile groups is highlighted.  相似文献   
967.
Subsurface exploration for uranium in the northwestern part of Bundelkhand massif, near Khor area, Shivpuri dist., M.P., resulted in intercepting a substantial thickness of mafic rock within Bundelkhand granitoid. Intercepts of this mafic rock at various levels in the boreholes, indicate that the rock mainly occurs as dykelike intrusion and fracture-fills within Bundelkhand granite. It is essentially composed of hypersthene and plagioclase, with or without olivine, leading to the characterisation as hypersthene microdolerite, noritic dolerite and norite (±olivine), depending on the grainsize and variation from intergranular to ophitic texture. Chemically, the rock is characterised by av. 49.09% SiO2, 2.46%TiO2, 2.33 Fe2O3, 9.45% FeO, 5.75% MgO, 8.37% CaO and 0.96% K2O. The normative composition ranges from 3.53% quartz, 46.86% plagioclase, 12.58% diopside, 19.24% hypersthene. The olivine normative samples show av. 5.65% olivine. Geochemical plots indicate an intra-plate affinity along with oceanic signature, while presence of mineralogical and normative olivine, together with the REE pattern, point towards a lower crustal or mantle source. The mineralogical and normative presence of either quartz or olivine in these mafic rocks implies that it has an intermediate character between the tholeiitic dolerite dykes and the komatiite-type ultramafics reported from Bundelkhand craton. The complex geochemical signature of the rocks also reveals that both intra-continental as well as a mixture of oceanic- to upper mantle signatures are evident. The present study is a first time report of the occurrence of this hitherto unknown noritic body at depth within the Bundelkhand granite, which has no visible surface expression. The findings may strengthen the existing concept of a continuum between Rajasthan craton in the west and Bundelkhand craton in the east, as a single protocontinent.  相似文献   
968.
The lacustrine sediments are one of the best sources to provide information on climate change, specially in peri-glacial climatic region. Schirmacher Oasis, located on the Princess Astrid Coast in Queen Maud Land, is one of the few areas in East Antarctica that provides valuable information on paleoclimate of the region with various depositional features formed due to deglaciation process. This Oasis is dotted with more than 100 lakes of proglacial, land-locked and epi-shelf type. The multi-proxy sedimentological data, generated from the sediment cores from land-locked lakes and grab sample from a proglacial lake, lying in the same drainage line in the central part of Schirmacher region has provided better insight into the paleoclimatic evolution of the region. The immature and chemically unaltered lake sediments have shown restricted drainage pattern. Different phases of warmer and cooler intervals are highlighted by the patterns of fluctuations in different sedimentological and statistical parameters. The dominance of glacial signatures is very clear on the lake sediments as revealed by the surface textures of quartz grains. Physical weathering has mainly controlled the overall sediments and the composition of clay fraction. The clay minerals indicate a gradual shift in the weathering regime and therewith in climate from strongly glacial to fluvioglacial specially around 42 ka. This indicates beginning of warming of the area much before the LGM. But the warm period is not strong enough to alter the overall clay chemistry. Proxy records indicate short-period climatic oscillations during late Quaternary.  相似文献   
969.
The structural and spectroscopic characteristics of phosphatic ferruginous shale samples from the Bijawar Group rocks from Sagar District of Madhya Pradesh (India) have been probed for identification of uranium species. Fluorapatite (\(\hbox {Ca}_{5}\hbox {(PO}_{4})_{3}\hbox {F}\), FAP) and haematite (\(\upalpha \)-\(\hbox {Fe}_{2}\hbox {O}_{3}\)) were identified as the main phases in the separated mineral concentrates. The photoluminescence (PL) and X-ray absorption near edge spectroscopy (XANES) studies pointed to a strong experimental evidence of both U(IV) and U(VI) oxidation states in the mineral concentrate portion obtained from the same parent host rock. The PL spectrum has confirmed the charge transfer (f–d) transition bands in UV and near-UV regions with emission peaks at ca. 290, 313, 336, 399 and 416 nm, which has been attributed to the substitution of \(\hbox {Ca}^{2+}\) ions by U(IV) in FAP and broad structureless emission due to stabilisation of U(VI) as \(\hbox {UO}_{6}^{6-}\) in haematite. Time-resolved spectroscopy studies have revealed biexponential decay components lasting 2–5 ns for U(IV) species and \(10\,\upmu \hbox {s}\) for U(VI) species. These characterisations revealed the fundamental information about the oxidation state and form of uranium in this region. Remediation measures for the Bijawar region are also suggested.  相似文献   
970.
Parama Roy 《GeoJournal》2018,83(2):289-304
Based on a Danish case study of urban renewal in Copenhagen’s Sundholm District, this paper examines, (a) how present urban regeneration efforts in a historically welfare-driven, but increasingly neoliberalized state context, is contributing to more or less spatial exclusion of the homeless, and (b) to what extent this may be associated with a revanchist/punitive stance of the Danish state. Using an urban political ecological lens, this paper highlights a relational understanding of the apparently dualistic/competing public and civic discourses shaping the Danish urban regeneration program. Revealing the complex ways that public socio-environmental policies and middle-class civic environmentalism/activism intersect with state-entrepreneurialism within such regeneration efforts, this paper presents an instance of a historically and geographically distinct process of neoliberal disciplining of the poor in Sundholm District. The paper shows that while such disciplining of the homeless is not driven by a purely punitive state, it results in soft, green-coded, nonetheless exclusionary implications for the homeless and their socio-spatial practices within the renewed urban spaces.  相似文献   
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