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951.
A.K. Singh 《Geomechanics and Geoengineering》2016,11(2):125-134
Consideration of the average pore water pressure and average unit weight of soil in the slope of a levee, ignoring the position of phreatic line for stability analysis is not correct. In addition, the influence of a rock-filled portion on the upstream slope, ignored in Kozeny analysis, plays a significant role in the stability of the downstream slope. In this study, levees resting on an impervious base, without a filter and with a filter, taking into consideration a realistic pore water pressure and corresponding seepage force, with unsaturated and saturated unit weights of soil above and below the phreatic line, respectively, by taking into account the capillary effect, location of the inverted filter and rock-filled portion of the upstream slope have been analysed. A numerical technique has been applied to compute the elevation of the phreatic line and a computer program was developed. The appropriate unit weight of soil above and below the phreatic line, taking into consideration the capillary effect, and actual pore water pressure ensure greater safety of the downstream slope. The factor of safety has been found to be 16.5% more for a levee with a filter than a levee without a filter for an upstream pondage depth of 18 m, this is increased by 22.0% in cases where there is an upstream rock-filled portion. 相似文献
952.
中国边境地区城镇化时空格局及其驱动力 总被引:2,自引:1,他引:2
Border area is not only an important gateway for inland opening-up,but also an important part of completing the building of a moderately prosperous society and optimizing national urban spatial pattern in China.Due to the location,natural resources endowment,and traffic accessibility,the urbanization speed is relatively slow in border areas.Therefore,it is a special area that needs to pay close attention to,especially under the background of the Belt and Road Initiative and China's regional coordinated development program.Based on the county-level data from 2000 to 2015,this paper tries to analyze the spatio-temporal pattern of urbanization in 134 border counties,and applies geographical detector method to study the driving forces of urbanization in border areas.Conclusions are as follows:(1)From 2000 to 2015,urbanization rate in border areas has been lower than the national average,and the gap has been widening.Some border counties in southern Xinjiang,Tibet,northeast of Inner Mongolia,and Yunnan,are even facing the problem of population loss.(2)In the same period,urbanization rate in the northwestern and southwestern border is low,while their urbanization rate grows relatively faster comparing with other border counties;urbanization rate in Tibet border is the lowest and grows relatively slowly;urbanization rate in the northeastern and northern border is slightly higher,but it grows slowly or even stagnates.(3)Transportation and industry are the important driving forces of urbanization in border areas,while the driving forces of market is relatively weak.And there are obvious mutual reinforcements among the driving forces,while the effort and explanatory power of resource force increases obviously after interaction.(4)Urbanization rate in the northwestern and southwestern border areas grows relatively fast,with industrial force and transportation force,market force and administrative force as the main driving forces respectively.Tibet border area has the lowest urbanization rate and growth rate,as the driving force of urbanization with strong contribution has not yet formed in Tibet.In the northeastern and northern border areas,the contribution of transportation force to urbanization is greater than other forces,and its interaction with market and industry has obvious effects. 相似文献
953.
盾构法隧道施工阶段管片的力学分析 总被引:6,自引:1,他引:5
盾构隧道衬砌管片在施工阶段处于复杂的受力状态,易出现局部破损现象。阐明了盾构施工阶段管片的受力特点,对其常见的局部破损现象及产生原因进行了总结与分析,在此基础上构建了施工阶段的管片力学模型,即一端固定、一端简支的受力构件。以某盾构工程施工参数为例,运用有限元方法实现该力学模型,按不同工况对其进行了数值模拟,并与现场实测结果进行了对比分析。研究表明:盾构施工阶段,衬砌管片会在第5~7环之间产生局部破损,与现场出现的管片破损部位十分接近;千斤顶推力的大小、倾角及偏差是导致施工阶段管片局部破损的主要原因,并给出了盾构施工阶段减轻管片破损的一些建议。 相似文献
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957.
通过正向与斜向波浪对半圆型防波堤(不开孔出水堤)的实验研究,给出了其水力特性及单位堤长所受的无因次水平波浪力、竖向波浪力和波浪浮托力随各主要影响因素的变化规律,特别指出了斜向波浪力可大于正向波浪力及水平波浪力中波谷作用大于波峰作用发生的条件。 相似文献
958.
塔克拉玛干沙漠腹地风沙土的力学性质 总被引:9,自引:5,他引:4
风沙土是形成于干旱、半干旱区的一种特殊性质的土,其力学性质不同于一般土体,结构松散性为其最主要的特点。通过对塔克拉玛干沙漠腹地14个风沙土样进行压缩试验和抗剪试验,获得了风沙土的基本力学参数:风沙土压缩模量值在50.00~142.86MPa之间,是一种低压缩性土;风沙土的内摩擦角值在31°55'~36°19'之间,低于河流冲积砂的内摩擦角值;风沙土存在结构力,其力学效应相当于粘聚力,可以在剪切试验中测出,其值在0.6~9.3kPa之间。并分析了影响这些力学参数的主要因素。 相似文献
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960.