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921.
The mid-Pleistocene transition (MPT) of the global climate system, marked by a shift of previously dominant 41-ka cycles to lately dominant 100-ka cycles roughly in the mid-Pleistocene, is one of the fundamental enigma in the Quaternary climate evolution. The process and origin of the MPT remain of persistent interest and conjecture. Here we present high-resolution astronomically tuned magnetic susceptibility (MS) and grain‐size records from a complete loess–paleosol sequence at Chaona on the central Chinese Loess Plateau. These two proxies are well-known sensitive indicators to the East Asian summer and winter monsoons, respectively. The records reveal a remarkable two-step simultaneous enhancement of the East Asian summer and winter monsoons at 0.9 Ma and 0.64 Ma, respectively, accompanied with an onset of a clear 100-ka cycle at 0.9 Ma and of a final, predominant 100-ka cycle starting at 0.64 Ma. The mid-Pleistocene stepwise rapid uplift of the Tibetan Plateau could be the mechanism driving the simultaneous enhancement of East Asian summer and winter monsoons and the shift of the periodicities during the MPT by complex positive feedbacks.  相似文献   
922.
Sterol biomarkers serve as an alternative method for detecting sewage pollution. Sterols were extracted from samples of surface sediment collected in Cubat?o (the Vila dos Pescadores and Vila Esperan?a communities) and quantified using GC–MS after Soxhlet extraction, cleanup, and derivatization. Fecal contamination was evaluated based on the concentration of coprostanol and the ratio of the selected sterols. The most abundant sterol was cholestanol, followed by coprostanol. The concentrations of coprostanol in surface sediments ranged from a minimum of 4.21?μg?g?1 dry sediment (Vila dos Pescadores station) to a maximum of 8.32?μg?g?1 dry sediment (Vila Esperan?a station). A coprostanol concentration of about 10?μg?g?1 was found, indicating areas of high sewage contamination. Coprostanol levels at sewage stations were higher than in other Brazilian coastal areas, which may be attributed to the fraction of the population without sanitation services.  相似文献   
923.
Values regarding built heritage have developed historically in response to both international agendas and local circumstances, and have underpinned the creation of World Heritage Sites and regeneration approaches within these. Such regeneration processes are an arena where different interests meet and often confront each other, with concepts and values of built heritage being used to different ends by the actors involved. However, the origins of conservation concepts and approaches are seldom considered. This paper examines the historical development of built heritage awareness and conservation policies from an institutionalist perspective at the international, European and Latin. American levels. It then considers conservation policies in Scotland and Brazil, particularly in the central areas in Edinburgh and Salvador from the 19th century to the 1970s, and the growing awareness of built heritage among certain sections of society and local institutions in these localities. Finally, the paper analyses the reasons behind, and types of, interventions in Edinburgh’s Old Town and Salvador’s Pelourinho and Maciel neighbourhoods, and the level of awareness of built heritage among the general population in the two cities. The paper draws conclusions on the influence of various factors on the development of approaches to built heritage and on the different ways in which these contributed to a particular awareness of built heritage in Edinburgh and Salvador.  相似文献   
924.
925.
A methodological procedure is proposed for determining the renewal period (RP), which expresses the ratio of total storage to recharge of carbonate aquifers, and it was applied to the overexploited moderate-size Becerrero carbonate aquifer (southern Spain). To this end, geological and subsurface data—time domain electromagnetic (TEM) soundings and borehole logs—were integrated to construct a three-dimensional (3D) geological model of the aquifer. The interconnected porosity was estimated by analyzing 73 rock samples. The resulting 3D geometrical model makes it possible to quantify the fractions of the aquifer having a confined or unconfined behaviour. Based on the total storage capacity (179?·?106–514?·?106 m3) and available aquifer recharge estimation (4.8?·?106–6.4?·?106 m3/year), an RP between 37 and 106 years is obtained. In view of the RP, an exploitation rate slightly lower than the average recharge of the system is recommended, so that the piezometric level will be stable but below the discharge head that is produced through the springs in natural conditions. The proposed methodology to obtain an aquifer RP and the management strategies designed accordingly are of broad interest, especially for carbonate aquifers, which are abundant in arid and semiarid regions.  相似文献   
926.
In palaeoseismological trench studies, precise correlation of sedimentary units between fault blocks has an unquestionable value for accurately inferring the amounts of coseismic displacement and hence for assessing seismic hazard. A methodology based on laser analysis of particle size and mineralogic composition by X-ray diffraction is proposed in order to strengthen the correlation of sedimentary units in a trench excavated across the Concud Fault (central Iberian Chain, Spain). The surveyed sediments show sharp and multiple lateral facies changes, as well as inconsistent optically stimulated luminescence (OSL) ages. The results reinforce the correlation based on field inspection of lithologic and sedimentologic features. Moreover, they allow interpretation of rejuvenation of OSL ages of samples in the upthrown fault block, which has been attributed to partial erosion of sedimentary units, as evidenced by their smaller thickness and erosive boundaries. The correlated units are then used to estimate coseismic displacements for three palaeoseismic events.  相似文献   
927.
This paper applies and validates a method for generating spatially distributed hydraulic conductivity (k) based on the specific capacity (Q s) for data-scarce regions. This method has been applied to the Araripe sedimentary basin, Brazil, and consists of four steps: (1) selection of (32) wells for which both k and Q s data are available; (2) estimation of k as a function of Q s for the (128) wells for which only specific capacity data are available; (3) spatial distribution of k using the kriging geostatistical tool; (4) validation of the method, using (17) representative wells with k measured data. The equation relating k and Q s showed a statistically significant linear relationship (R = 0.93), from which a database has been generated using kriging with the spherical model. The results showed a calibration coefficient of Nash and Sutcliffe (NS) of 0.54 and moderate spatial dependence ratio of 69 %. The validation process provided only a moderate efficiency (NS = 0.22), possibly due to the geological complexity of the focus system. Despite its limitations, the method indicates the possibility of application of ordinary kriging to generate reliable data from auxiliary variables, especially for the water management of data-scarce areas.  相似文献   
928.
Recharge is a key parameter in groundwater resources management, and a reliable estimate of recharge is required for their sustainable development. Several methods are available to evaluate recharge; however, selecting the appropriate one is made difficult because each method has its advantages and drawbacks, and results can vary greatly from one method to another. Recharge methods can actually refer to different processes. This paper compares and discusses the results obtained from five regional-scale recharge assessment approaches applied to a fractured rock aquifer in a region with a temperate and humid climate (Annapolis Valley, Nova Scotia, Canada). These methods are distinguished between those providing estimates of the net infiltration (I) into the subsurface (river hydrograph separation and soil moisture balance) from those considering the net recharge (W) to the regional bedrock aquifer (river 7-day low-flows, the corrected soil moisture balance, a numerical groundwater flow model developed with FEFLOW and an infiltration model developed with HELP). The estimated net infiltration ranges from 160 to 250 mm/year, whereas the net recharge estimates range from 80 to 175 mm/year for the entire study area. Although different assessment methods were used, the estimated recharge range is still quite large, demonstrating the importance of using several methods. This case study should provide guidance on choices to be made in the development of a strategy for assessing representative values of aquifer recharge at the regional scale under similar geological and climatic conditions. The use of multiple complementary approaches should lead to a better understanding of the system dynamics and to better defined a representative range of recharge estimates.  相似文献   
929.
Assessing the climatic characteristics and identifying the climatic parameters of a specific region can play a major role in human welfare. Thermal comfort conditions are among the most significant factors of climatic variables in the northwestern regions of Iran due to the considerable spatial and temporal variations and are vital for environmental, energy and economic management. It is therefore necessary to advance our knowledge of the climatic conditions in order to provide an appropriate tool for managing climatic extremes. This requires charting of the range of clusters of the thermal comfort conditions in this region. In this study, the general atmosphere circulation model HADCM3 and the A1 scenario, downscaled by the LARS-WG model, were employed to simulate the climatic conditions in Iran during the period 2011–2040. The data obtained were compared with sampled data from six Iranian climatic stations for the 30-year period (1961–1990). In order to tabulate this comparison, six clusters per climatic station were defined based on intrinsic similarity of data. Results show an increase in the annual average temperature of these six stations by 1.69 °C for the predicted years, projected from the base years 1961–1990. This factor has resulted in an increment of the annual average thermal comfort temperature inside buildings by a magnitude of 0.52 °C in future decades. When the thermal requirements of the studied region were evaluated based on the real temperature difference and the degree of thermal comfort, it becomes clear that apart from cluster 1, the energy required to reach thermal comfort inside buildings will increase in the future. As a result of this temperature increase, an increase of the energy required to reach the thermal comfort is expected. This new methodology is an interesting tool and needs to be seriously considered by engineers and architects in designing buildings of the future.  相似文献   
930.
<正>Representatives of the extinct psocid family Empheriidae are known from Eocene Baltic amber, Lowermost Eocene French amber(Oise),and Lower Cretaceous Spanish amber(Alava).We report herein the first discovery of an empheriid psocid from the Cretaceous amber of New Jersey as Jerseyempheria grimaldii gen.et sp. nov.The fossil is figured and described.The new species is distinguished from related taxa.A discussion and checklist of Empheriidae are provided.  相似文献   
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