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231.
Recent changes of Shandong sandy coast and in flence of human activitiesTXRecentchangesofShandongsandycoastandinfluenceofhuman... 相似文献
232.
Based on the damage mechanism of rock during excavation, the maximum tensile strain criterion for pinpointing relaxation region or excavation‐disturbed (damage) zone (EDZ) is introduced. To simulate the deformation and stress redistribution caused by the deterioration of the deformation and strength parameters in the EDZ, the ‘restraint‐relaxation’ finite element algorithm is formulated using the deformation and strength parameters of pre‐and post‐relaxation. The Xiaowan arch dam project (292 m high) is studied by the proposed method, in which the permissible tensile strain and fluidity parameter are evaluated using back analysis. The computation results have good agreement with the field monitoring. An important inference from the study is the necessity of considering the relaxation effects on the dam/foundation system during the construction and operation period. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
233.
The developmental activities, particularly the construction of hydroelectric projects are causing a great loss of biodiversity
in the Indian Himalayan Region. The Himachal Pradesh, a part of IHR is well known for the development of hydroelectric projects.
The Parbati H.E. Project is amongst the major projects of the State. The different stages of the project are all causing loss
of biodiversity of the area. Stage III of the Parbati H.E. Project is a run of the river scheme on the Sainj River downstream
of Power House of Parbati H.E. Project Stage II. The project shall utilize regulated discharge of Parbati H.E. Project Stage
II and inflow of River Sainj for power generation, and has been contemplated as a peaking station operating in tandem with
Stage II. The present study has been undertaken to see the impact of hydroelectric project on the biodiversity, particularly
on medicinal plants. A total of 104 species of medicinal plants, belonging to different life forms, i.e., trees (23 spp.),
shrubs (22 spp.), herbs (57 spp.) and ferns (2 spp.) were recorded. The species have been analyzed and studied for their distribution,
classification, altitudinal zones, part (s) used, indigenous uses, nativity, endemism and rarity. DDifferent parts of these
species, such as whole plants, roots (including rhizomes and tubers), leaves, flowers, fruits, seeds, stems, barks, spikes,
nuts and insect galls are used by the inhabitants for curing various diseases and ailments. 30 species are native to the Himalayan
region, 9 species native to the Himalayan region and adjacent countries also and 65 species are non-natives. 9 species are
near endemics. Considering the whole Himalaya as a biogeographic unit (sensu lato), the near endemics are endemic to the Himalaya. Among these species, Zanthoxylum armatum is categorized as Endangered and Valeriana wallichii as Vulnerable. Hedychium spicatum, Rhus javanica, Berberis lycium, Thalictrum foliolossum, Salvia lanata, Rubia cordifolia and Bergenia ligulata may be considered as threatened species due to their over exploitation for trade. 90 species are propagated by seeds, 8 species
by seeds and rhizomes/roots/tubers, 4 species by seeds and cuttings, and 2 species by sori. A management plan for the cultivation
and conservation of the medicinal plants in the dam submergence area, and the commercially viable medicinal plants with high
value in the catchment area is suggested. 相似文献
234.
Linked hydrologic, hydraulic, and ecological models can facilitate planning and implementing water releases from reservoirs to achieve ecological objectives along rivers. We applied a flow-ecology model, the Ecosystem Functions Model (HEC-EFM), to the Bill Williams River in southwestern USA to estimate areas suitable for recruitment of riparian tree seedlings in the context of managing flow releases from a large dam for riparian restoration. Ecological variables in the model included timing of seed dispersal, tolerable rates of flow recession, and tolerable duration of inundation following germination and early seedling establishment for native Fremont cottonwood and Goodding's willow, and non-native tamarisk. Hydrological variables included peak flow timing, rate of flow recession following the peak, and duration of inundation. A one-dimensional hydraulic model was applied to estimate stage-discharge relationships along ~58 river kilometres. We then used HEC-EFM to apply relationships between seedling ecology and streamflow to link hydrological dynamics with ecological response. We developed and validated HEC-EFM based on an examination of seedling recruitment following an experimental flow release from Alamo Dam in spring 2006. The model predicted the largest area of potential recruitment for cottonwood (280–481 ha), with smaller areas predicted for willow (174–188 ha) and tamarisk (59–60 ha). Correlations between observed and predicted patches with successful seedling recruitment for areas within 40 m of the main channel ranged from 0.66 to 0.94. Finally, we examined arrays of hydrographs to identify which are most conducive to seedling recruitment along the river, given different combinations of peak flow, recession rate, and water volume released. Similar application of this model could be useful for informing reservoir management in the context of riparian restoration along other rivers facing similar challenges. 相似文献
235.
236.
以石门子水库副坝(土石坝)变形监测为例,介绍了其监测方法及对观测数据的处理和分析,采用G PS平面拟合高程进行水库竖向位移监测,其精度与三等水准精度相当,而且可以将平面与竖向位移同时观测,大大提高了测量效率,节省了人力和物力。 相似文献
237.
Anita Moldenhauer-Roth Guillaume Piton Sebastian Schwindt Mona Jafarnejad Anton JSchleiss 《国际泥沙研究》2021,36(1):136-150
Sediment detention basins are implemented on mountain rivers to trap solid material that may aggravate the flooding of downstream settlements.However,retention structures built in the past may unnecessarily retain sediment during non-hazardous flood events,resulting in high maintenance costs and sediment deficit downstream.In addition,the so-called spontaneous self-flushing of previously retained sediment during floods has occasionally been observed.Recent research suggests to design sediment detention basins for controlling sediment passage with a guiding channel across the deposition area upstream of a hybrid barrier.Such barriers consist of a check dam with a slot orifice and an upstream bar screen with a bottom clearance in order to benefit from a combined mechanical-hydraulic retention control.The present paper enhances this pioneering research with the help of new experimental data,including a wide range of sediment mixtures and large wood,as well as variable barrier heights.Improved design criteria are provided regarding the bar screen and the basin storage capacity.The functionality of the enhanced concept for sediment detention is illustrated by a case study on a physical model:the protection of the Villard-Bonnot village(France)against torrential hazards. 相似文献
238.
组件式地理信息系统是一种新型的系统,利用组件式技术开发地理信息系统已成为地理信息系统二次开发的主流。由于采用该技术可以把地理信息系统和其他专业应用系统充分结合起来,因而得到广泛的应用。本文系统介绍了组件式地理信息系统的基本概念及其特点功能,列举说明了一种二次开发的代表性控件一MapX,最后结合实例讨论了基于组件式技术开发应用系统的思想和过程。 相似文献
239.
Stepwise decreases of the Huanghe (Yellow River) sediment load (1950–2005): Impacts of climate change and human activities 总被引:3,自引:0,他引:3
Houjie Wang Zuosheng Yang Yoshiki Saito J. Paul Liu Xiaoxia Sun Yan Wang 《Global and Planetary Change》2007,57(3-4):331-354
The sediment load delivered from the Huanghe (Yellow River) to the sea has decreased sharply to 0.15 × 109 metric tons per year (0.15 Gt/yr) between 2000 and 2005, and now represents only 14% of the widely cited estimate of 1.08 Gt/yr. The river seems to be reverting to the pristine levels characteristic of the middle Holocene, prior to human intervention. Datasets from 1950 to 2005 from four key gauging stations in the main stream reveal distinct stepwise decreases in sediment load, which are attributed to both natural and anthropogenic impacts over the past 56 yr. Completions of two reservoirs, Liujiaxia (1968) and Longyangxia (1985), in the upper reaches of the river and their joint operations have resulted in stepwise decreases in sediment load coming from the upper reaches. Effective soil conservation practices in the middle reaches since the late 1970s, combined with the operation of the Sanmenxia and Xiaolangdi reservoirs, have also caused stepwise decreases in sediment load at Huayuankou in the middle reaches, but the decrease differs from that observed in the upper reaches. Decrease in precipitation is responsible for 30% of the decrease in sediment load at Huayuankou, while the remaining 70% is ascribed to human activities in the river basin, of which soil conservation practices contribute 40% to the total decrease. Sediment retention within reservoirs accounts for 20% of the total sediment load decrease, although there was notable sediment retention within the Xiaolangdi reservoir from 2000 to 2005. The remaining 10% of the decrease in sediment load is a result of the operation of reservoirs in the upper reaches. In the lower reaches, 20% of the sediment passing Huayuankou has been lost as a result of channel deposition and water abstraction. Soil conservation practices and the operation of reservoirs have lowered the content of coarser sediment (D > 0.05 mm) at Huayuankou, and reduced channel deposition in the lower reaches. In contrast, sediment loss owing to water abstraction in the lower reaches has increased considerably as water consumption for agricultural needs has increased. Therefore, the combined effects of climate change and human activities in the upper, middle, and lower reaches have resulted in stepwise decreases in the sediment load delivered from the Huanghe to the sea. The Huanghe provides an excellent example of the altered river systems impacted by climate change and extensive human activities over the past 56 yr. Further dramatic decreases in sediment load and water discharge in the Huanghe will trigger profound geological, morphological, ecological, and biogeochemical responses in the estuary, delta, and coastal sea. 相似文献
240.
Ashok K. Chugh 《国际地质力学数值与分析法杂志》2007,31(4):607-648
A forced vibration procedure is presented to estimate fundamental and higher frequencies of vibrations and associated mode shapes of gravity structures. The gravity structures considered are retaining walls and gravity dams. The validity of the proposed procedure is tested on three test problems of varying complexity for which the natural vibration frequencies and mode shapes either have known analytical solutions or have been determined via numerical means/field tests by others. Also included are the results of natural vibration frequencies and associated mode shapes for a spillway control structure located near the abutment end of an embankment dam obtained using the proposed procedure. For all problems considered, fundamental frequency and mode shape results using the proposed procedure are compared with the results obtained using an alternative procedure in which static deflections due to the structure's own weight are used as the starting point for free vibrations by setting the gravity vector to zero. All results compare well. The merits of the proposed procedure are discussed. Published in 2006 by John Wiley & Sons, Ltd. 相似文献