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161.
A gradient-based inverse method – the sequential self-calibrated method – is combined with a genetic algorithm method to search
the optimal design scheme for a tracer test. The sequential self-calibrated method is developed for estimating conductivity
distribution in a study domain conditioning on tracer test data. To improve the calculation efficiency, a fast streamline-based
approach is used to compute the derivative of concentration with respect to the changes of hydraulic conductivity. Performance
of the sequential self-calibrated method has been studied using a synthetic aquifer having a sandwich-like geologic structure
where hypothetical tracer tests are conducted. The study results indicate that the locations and number of sampling wells
will significantly affect accuracy in the estimates. To maximize estimating accuracy in the sequential self-calibrated method
for a fixed number of sampling wells, a genetic algorithm method is applied to search the optimal locations for sampling wells.
The results indicate that the optimal sampling well locations depend on the apparent geologic structure and the difference
in conductivity values for the various regions. For the sandwich-like structure, when the difference between conductivity
values in the two separate regions is large enough, the optimal locations for the sampling wells will be fixed, regardless
of conductivity values. The study results also show that based on the optimal sampling-well scheme, estimating accuracy will
increase as the number of sampling wells increases, even though the rate of increasing accuracy slows as the number of wells
increases. 相似文献
162.
An fKdV equation of two-layer flow and an averaged fKdV equation (AfKdV equation) with respect to phase are derived to determine the theoretical amplitude and period of the precursor solitons in the present paper. In terms of the AfKdV equation derived by the authors, a new theory on the precursor soliton generation based on Lee et al.'s concept is presented. Concepts of asymptotic mean hydraulic fall and level are introduced in our analysis, and the theoretical amplitude and period both depend on the asymptotic mean levels and stratified parameters. From the present theoretical results, it is obtained that when the moving velocity of the topography is at the resonant points, there exist two general relations: (1) amplitude relation Å=2F, (2) period relation $\mathop \tau \limits^ \circ = - 8m_1 m_3^{ - 1} \sqrt {6m_4 m_3^{ - 1} } \mathcal{F}$ , in which Å and $\tau $ are the amplitude and period of the precursor solitons at the resonant points respectively,m 1,m 3 andm 4 are coefficients of the fKdV equation, andF is an asymptotic mean half-hydraulic fall at subcritical cutoff points. The theoretical results of this paper are compared with experiments and numerical calculations of two-layer flow over a semicircular topography and all these results are in good agreement. Due to the canonical character of the coefficients of fKdV equations, this theory also holds for any two-dimensional system, which can be reduced to fKdV equations. 相似文献
163.
Yuewu LIU Dapeng GAO Qi LI Yizhao WAN Wenjie DUAN Xiaguang ZENG Mingyao LI Yewang SU Yongbo FAN Shihai LI Xiaobing LU Dong ZHOU Weimin CHEN Yiqin FU Chunhui JIANG Shaoji HOU Lisheng PAN Xiaolin WEI Zhiming HU Xianggang DUAN Shusheng GAO Rui SHEN Jin CHANG Xiaoyan LI Zhanli LIU Yujie WEI Zhemin ZHENG 《力学进展》1971,49(1):201901
页岩气的开采涉及破裂和收集输运两个关键过程.如何实现2000,m以下、复杂地应力作用下、多相复杂介质组分的页岩层内网状裂纹的形成,同时将孔洞、缝隙中的游离、吸附气体进行高效收集,涉及到诸多的核心力学问题.这一工程过程涵盖了力学前沿研究的诸多领域:介质和裂纹从纳米尺度到千米尺度的空间跨越,游离、吸附气体输运过程中微秒以下的时间尺度事件到历经数年开采的时间尺度跨越,不同尺度上流体固体的相互作用,以及压裂过程中通过监测信息反演内部破坏状态等.针对近年来我们国家页岩气勘探开发工作所取得的成就及后续发展中面临的前沿力学问题,在综合介绍页岩气藏的基本特征和开发技术的基础上,以页岩气开采中的若干力学前沿问题为主线,从页岩力学性质及其表征方法、页岩气藏实验模拟技术、页岩气微观流动机制及流固耦合特征、水力压裂过程数值模拟方法、水力压裂过程微地震监测技术、高效环保的无水压裂技术等6个方面的最新研究进展进行了总结和展望,结合页岩气藏开发的工程实践, 深入探究了其中力学关键问题,以期对从事页岩气领域的开发和研究的从业人员提供理论基础, 同时,该方面的内容对力学学科、尤其是岩土力学领域的科研工作也具有重要指导价值. 相似文献
164.
Results of experimental velocity measurements in air at several cross-sections along a straight annular section channel comparable to a hydraulic machine admission duct are presented. The flow analysis focuses on the axial and tangential velocity components and their modification with changes in the intensity of swirl along the channel. Particular prominence is given to an anomalous flow, the ‘dead water core’, occurring at the greatest swirl intensities. An earlier method of evaluating the core size of this anomalous flow on the basis of a vortex-type schematization is tested; Strscheletzky's method is also analysed. Finally a definition of the dead water core dimensions based on the axial velocity component distribution is proposed 相似文献
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169.
水工混凝土小角度冲蚀磨损特性的研究 总被引:6,自引:0,他引:6
选用55kW的3GQ-2/70型高压清洗水射流装置作为水工混凝土的冲蚀磨损设备,考察了小角度条件下含沙高速水射流作用下混凝土材料的冲蚀磨损性能。结果表明:混凝土肥到严重的冲蚀磨损;在冲击角度较小时,混凝土材料的冲蚀磨损机制主要表现为硬质磨粒沿水平速度方向的切削作用,以及沿垂直方向的冲击作用导致的表面裂纹和脆性断裂;钢纤维对混凝土材料的小角度冲蚀破坏有明显的增强作用。 相似文献
170.
Jonathan J. Halvorson Donald K. McCool Larry G. King Lawrence W. Gatto 《Journal of Terramechanics》2001,38(3)
We monitored two experimental areas at the Yakima Training Center (YTC) in central Washington to measure changes to M1A2 Abrams (M1) tank-rut surface geometry and in- and out-of-rut saturated hydraulic conductivity (Kfs), soil penetration resistance (SPR) and soil bulk density (BD). Profile-meter data show that rut cross-sectional profiles smoothed significantly and that turning ruts did so more than straight ruts. Rut edges were zones of erosion and sidewall bases were zones of deposition. Kfs values were similar in and out of ruts formed on soil with 0–5% moisture by volume, but were lower in ruts formed on soil with about 15% water. Mean SPR was similar in and out of ruts from 0- to 5-cm depth, increased to 2 MPa outside ruts and 4 MPa inside ruts at 10- to 15-cm depth, and decreased by 10–38% outside ruts and by 39–48% inside ruts at the 30-cm depth. Soil BD was similar in and out of ruts from 0- to 2.5-cm depth, and below 2.5 cm, it was generally higher in ruts formed on moist soil with highest values between 10- and 20-cm depth. Conversely, BD in ruts formed on dry soil was similar to out-of-rut BD at all depths. This information is important for determining impacts of tank ruts on water infiltration and soil erosion and for modifying the Revised Universal Soil Loss Equation (RUSLE) and the Water Erosion Prediction Project (WEPP) models to more accurately predict soil losses on army training lands. 相似文献