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71.
72.
垃圾填埋场复合衬垫剪切特性单剪试验研究 总被引:1,自引:0,他引:1
针对垃圾填埋工程中复合衬垫的界面抗剪特性,利用改进的叠环式单剪仪,对由砂土-无纺型土工布-土工网格-土工膜-夯实粘土组成复合衬垫进行了整体剪切试验研究。重点讨论了复合衬垫整体单剪试验的应力-位移曲线、相同剪切应力下各个界面的位移大小与变化特征和强度特性。研究结果表明:复合衬垫整体单剪试验的应力-位移曲线在低法向应力试验中没有呈现明显的软化特征,在高法向应力试验中有硬化现象;随法向应力增加剪切破坏面会发生转移;目前常用的把复合衬垫拆分为单个界面进行研究来确定最危险界面的方法不能够正确地反映填埋场中的复合衬垫在加载过程中的衬垫单元的实际受压变形情况和在剪切变形过程中最危险破坏面转移的情况;复合衬垫界面的抗剪强度包线呈现双曲线性质。 相似文献
73.
74.
白云石具有较高的热膨胀系数,较低的热导率和稳定的高压物相,用它制成金刚石合成的高压腔内衬,可以减少腔内压力梯度,屏蔽矿物成份及杂质进入高压腔,提高金刚石合成效果。 相似文献
75.
76.
防渗工程中土工膜的褶皱现象普遍存在,然而目前关于土工膜界面剪切特性的研究大都忽略了褶皱的影响。以糙面土工膜(GM)和针刺钠基膨润土防水毯(GCL)组成的复合衬里为研究对象,利用水化变形试验证实两步水化法能有效地加速含褶皱GM+GCL复合衬里的水化步骤,使用大尺寸温控水浴直剪仪对含褶皱GM+GCL复合衬里的剪切特性进行了试验研究。通过将含褶皱GM+GCL复合衬里的剪切特性与无褶皱复合衬里进行对比分析,揭露了GM褶皱对复合衬里剪切特性的影响机制。GM褶皱的存在使得GM+GCL复合衬里的剪切应力-位移曲线产生较大差异,并使得低压下复合衬里的抗剪强度明显降低。GM褶皱使复合衬里产生明显的渐进破坏效应,复合衬里内部能出现多种破坏模式共存的现象。 相似文献
77.
78.
Summary. The liner of a pressure tunnel needs to be designed such that it can withstand the loads from the ground, the internal pressure,
and minimize the development of significant pore pressures at the liner-ground interface. Pore pressures behind the liner
reduce the effective stresses in the ground immediately in contact with the liner and can ultimately produce loss of support
from the ground. Deformations and loads of the liner are intimately connected to the interplay that exists between liner,
ground, and pore pressures in the ground. A closed-form analytical solution has been derived that accounts for the inter-relation
between liner, ground, and pore pressures. Elastic response of the liner and ground, and plane strain conditions at any cross-section
of the tunnel are assumed. The solution shows that stresses in the ground depend on the following dimensionless factors: relative
stiffness of the ground and liner, ground Poisson’s ratio, surface slope angle, coefficient of earth pressure at rest, relative
tunnel depth, and magnitude of the pore pressure behind the liner relative to the internal pressure. The minimum ground effective
tangential stresses at the ground-liner interface increase with the relative stiffness of the liner, with the coefficient
of earth pressure at rest, and with tunnel depth. They decrease with increasing surface slope angle and pore pressures behind
the liner. As leakage through the liner increases, the pore pressures in the ground increase. This results in a decrease of
effective radial and tangential stresses in the ground while displacements and loads of the liner are relatively less affected. 相似文献
79.
Testing the ability of bentonite-amended natural zeolite (clinoptinolite) to remove heavy metals from liquid waste 总被引:2,自引:0,他引:2
The design of environmentally sound liquid waste containment structures has become a crucial task in engineering applications
due to ever increasing groundwater contamination from such sites. Construction of such structures usually requires a bottom
liner of low hydraulic conductivity as part of the design. In order to reduce the hazards associated with liquid wastes including
landfill leachate, bentonite-amended natural zeolite is proposed as an alternative to conventional earthen liners. Among many
contaminants associated with liquid wastes, heavy metals are the most dangerous ones. This paper deals with determining the
ability of natural zeolite to remove heavy metals from aqueous waste. For this purpose, crushed natural zeolite (clinoptinolite)
is amended with commercial powdered bentonite to yield a soil mixture low in permeability and high in ion-exchange capacity.
Leachate from a conventional landfill is used as the percolation fluid. Concentrations of certain heavy metals in the effluent
fluid percolated through the bentonite-zeolite mixture are compared with that of initial leachate. The conclusion is reached
that certain metals are efficiently removed from the influent solution by the soil matrix whereas some ions do not show significant
reduction in concentration. This is attributed to high hydraulic conductivity of the bentonite-zeolite mixture. 相似文献
80.
为研究浅埋黄土隧道锚喷初支+初衬+二衬构成的3层支护体系力学特性,以某黄土隧道为依托,采用钢弦式传感器对围岩压力、初衬与二衬接触压力、二衬钢筋轴力、二衬混凝土应变、钢拱架应力等进行了系统测试与分析。结果表明:(1) 作用在左拱腰处的围岩压力较大,且稳定值为240 kPa;(2) 浅埋段按不同围岩压力计算公式得到压力值均大于围岩压力实测值,其中采用太沙基公式得到的压力值与实测值相对接近;(3) 该黄土隧道二衬全部受压,其分布形态呈明显的猫耳形,初支、初衬、二衬承受的荷载比例分别为51.34%、37.29%、11.38%;(4) 钢拱架整体以受压为主,在拱顶和拱腰处受力较大,接近屈服状态;(5) 初支发挥了一定的围岩自承能力,其与初衬共同承担了大部分围岩荷载,二衬主要为结构安全储备。 相似文献