全文获取类型
收费全文 | 2685篇 |
免费 | 172篇 |
国内免费 | 314篇 |
专业分类
电工技术 | 21篇 |
综合类 | 209篇 |
化学工业 | 295篇 |
金属工艺 | 30篇 |
机械仪表 | 155篇 |
建筑科学 | 622篇 |
矿业工程 | 675篇 |
能源动力 | 31篇 |
轻工业 | 117篇 |
水利工程 | 95篇 |
石油天然气 | 224篇 |
武器工业 | 35篇 |
无线电 | 31篇 |
一般工业技术 | 368篇 |
冶金工业 | 89篇 |
原子能技术 | 55篇 |
自动化技术 | 119篇 |
出版年
2024年 | 10篇 |
2023年 | 34篇 |
2022年 | 147篇 |
2021年 | 89篇 |
2020年 | 98篇 |
2019年 | 86篇 |
2018年 | 96篇 |
2017年 | 85篇 |
2016年 | 111篇 |
2015年 | 104篇 |
2014年 | 134篇 |
2013年 | 147篇 |
2012年 | 106篇 |
2011年 | 168篇 |
2010年 | 125篇 |
2009年 | 121篇 |
2008年 | 174篇 |
2007年 | 134篇 |
2006年 | 151篇 |
2005年 | 118篇 |
2004年 | 121篇 |
2003年 | 110篇 |
2002年 | 74篇 |
2001年 | 62篇 |
2000年 | 67篇 |
1999年 | 59篇 |
1998年 | 75篇 |
1997年 | 75篇 |
1996年 | 63篇 |
1995年 | 57篇 |
1994年 | 30篇 |
1993年 | 44篇 |
1992年 | 31篇 |
1991年 | 14篇 |
1990年 | 11篇 |
1989年 | 6篇 |
1988年 | 9篇 |
1987年 | 11篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1981年 | 5篇 |
1978年 | 1篇 |
排序方式: 共有3171条查询结果,搜索用时 15 毫秒
1.
2.
Robert Bertuzzi 《岩石力学与岩土工程学报(英文版)》2019,11(3):494-510
This paper presents the results of ongoing research carried out by the author exploring methods to provide a more robust estimate of rock mass properties specifically for use in tunnel design. Data from various large-scale rock mass failures are introduced, including coal pillars. The damage-initiation,spalling-limit approach is compared to the coal pillar database. New comparisons of estimating the geological strength index(GSI) and relationships to estimate the Hoeke Brown failure criterion parameters, mb, s and a, are presented. 相似文献
3.
Strain rate is not only an important measure to characterize the deformation property, but also an important parameter to analyze the dynamic mechanical properties of rock materials. In this paper, by using the SHPB test system improved with high temperature device, the dynamic compressive tests of sandstone at seven temperatures in the range of room temperature to 1000 °C and five impact velocities in the range of 11.0–15.0 m/s were conducted. Investigations were carried out on the influences of strain rate on dynamic compressive mechanical behaviors of sandstone. The results of the study indicate that the enhancement effects of strain rates on dynamic compressive strength, peak strain, energy absorption ratio of sandstone under high temperatures still exist. However, the increase ratios of dynamic compressive strength, peak strain, and energy absorption ratio of rock under high temperature compared to room temperature have no obvious strain rate effects. The temperatures at which the strain rates affect dynamic compressive strength and peak strain most, are 800, and 1000 °C, respectively. The temperatures at which the strain rates affect dynamic compressive strength and peak strain weakest, are 1000 °C, and room temperature, respectively. At 200 and 800 °C, the strain rate effect on energy absorption ratio are most significant, while at 1000 °C, it is weakest. There are no obvious strain rate effects on elastic modulus and increase ratio of elastic modulus under high temperatures. According to test results, the relationship formula of strain rate with high temperature and impact load was derived by internalizing fitting parameters. Compared with the strain rate effect at room temperature condition, essential differences have occurred in the strain rate effect of rock material under the influence of high temperature. 相似文献
4.
《矿业科学技术学报(英文版)》2020,30(2):265-269
The purpose of this study was to develop a physico-mathematical model and technique for estimation of chemical bond stability depending on electric field intensity of an external point charge. A hypothesis for a possible physico-chemical mechanism of the formation of additional harmful gases in the rock destruction by blasting was proposed. The theoretical basis of the hypothesis is the method of theretical evaluation of bond energy depending on the distance to a point charge, the third Coulomb centre. The quantum-mechanical model for calculating the electronic terms of molecules makes it possible to solve problems associated with the determination of parameters of molecules under the action of various physical fields on the system under consideration. The model was approved for some diatomic molecules. The discrepancy between the experimental data and calculated data did not exceed 14%, which proves accuracy of the obtained results. The model can be used in the field of research into the causes of gas-dynamic phenomena in underground coal mines, in studies of the degree of stability of nanostructured components of coal under physical influences, and in the theoretical design of new compounds and structures in the field of nanomaterial science and nanotechnology. 相似文献
5.
《Journal of the European Ceramic Society》2020,40(4):1644-1650
Possibility of formation of quinary and senary equimolar high entropy oxides from the Co-Cr-Fe-Mg-Mn-Ni-O system is presented. Different proposed compositions are synthesized using the solid-state reaction route at high temperatures (900−1100 °C) and quenched to room temperature. Phase composition of the samples is studied, showing tendency toward formation of two main phases: rock salt-structured Fm-3 m and spinel-structured Fd-3 m. It is documented that the annealing temperature has a profound effect on stability of both structures, and at 1100 °C usually the highest content of Fm-3 m phase is usually observed. Three different oxides, namely, (Co,Cr,Fe,Mn,Ni)3O4, (Co,Cr,Fe,Mg,Mn)3O4 and (Cr,Fe,Mg,Mn,Ni)3O4 are obtained as single-phase materials, which structure can be described as the high entropy Fd-3 m spinel one. The latter two compounds have not been previously reported in the literature. Activated character of the electrical conductivity dependence on temperature is observed, with relatively high total conductivity at high temperatures and corresponding high absolute values of Seebeck coefficient. 相似文献
6.
通过认真学习《细节决定成败》,结合井矿盐开采的实际,分别以生产过程中的三个细节为主,讨论了在采输卤生产技术控制中的细节的重要性。 相似文献
7.
8.
9.
Practical Equivalent Continuum Model for Simulation of Jointed Rock Mass Using FLAC3D 总被引:1,自引:0,他引:1
A simple practical equivalent continuum numerical model for simulating the behavior of jointed rock mass has been extended to three-dimensional using FLAC3D. This model estimates the properties of jointed rock mass from the properties of intact rock and a joint factor (Jf), which is the integration of the properties of joints to take care of the effects of frequency, orientation, and strength of joint. A new FISH function has been written in FLAC3D specifically for modeling jointed rocks using the Duncan and Chang hyperbolic model. This model has been validated first with simple element tests at different confining pressures for different rocks with different joint configurations. Explicit modeling of the joints has also been done in element tests and results obtained compare well with the results of equivalent continuum model and also with experimental results. Further, this has been applied for a case study of a large underground power house cavern in the Himalayas. The analysis has been done under various stages of excavation, assigning a null model available in FLAC3D for simulating the excavation. 相似文献
10.
M. D. Beard M. J. S. Lowe 《International Journal of Rock Mechanics and Mining Sciences》2003,40(4):527-536
The research outlined in this paper is aimed at the development of a portable non-destructive testing instrument for evaluating the condition of rock bolts. In applications such as coal mine roof reinforcement, the opportunities for rock bolt inspection are currently limited to destructive techniques such as the pull-out test. It is proposed that guided ultrasonic waves can be used to solve this inspection problem, using a pulse-echo test carried out from the free end of the bolt. Suitable test frequencies have been identified through the use of modelling software, and successful laboratory and site trials have been undertaken. The research has shown that the proposed approach is capable of determining the bolt length, and of identifying major defects such as necking, deformation, and loss of resin encapsulation. 相似文献