全文获取类型
收费全文 | 4919篇 |
免费 | 247篇 |
国内免费 | 233篇 |
专业分类
电工技术 | 133篇 |
综合类 | 283篇 |
化学工业 | 651篇 |
金属工艺 | 206篇 |
机械仪表 | 218篇 |
建筑科学 | 951篇 |
矿业工程 | 76篇 |
能源动力 | 126篇 |
轻工业 | 226篇 |
水利工程 | 123篇 |
石油天然气 | 75篇 |
武器工业 | 20篇 |
无线电 | 116篇 |
一般工业技术 | 768篇 |
冶金工业 | 1109篇 |
原子能技术 | 50篇 |
自动化技术 | 268篇 |
出版年
2024年 | 14篇 |
2023年 | 65篇 |
2022年 | 85篇 |
2021年 | 111篇 |
2020年 | 107篇 |
2019年 | 119篇 |
2018年 | 119篇 |
2017年 | 131篇 |
2016年 | 147篇 |
2015年 | 120篇 |
2014年 | 209篇 |
2013年 | 349篇 |
2012年 | 207篇 |
2011年 | 383篇 |
2010年 | 277篇 |
2009年 | 330篇 |
2008年 | 308篇 |
2007年 | 312篇 |
2006年 | 298篇 |
2005年 | 211篇 |
2004年 | 196篇 |
2003年 | 189篇 |
2002年 | 171篇 |
2001年 | 90篇 |
2000年 | 76篇 |
1999年 | 75篇 |
1998年 | 56篇 |
1997年 | 63篇 |
1996年 | 49篇 |
1995年 | 62篇 |
1994年 | 51篇 |
1993年 | 42篇 |
1992年 | 42篇 |
1991年 | 26篇 |
1990年 | 23篇 |
1989年 | 21篇 |
1988年 | 15篇 |
1987年 | 21篇 |
1986年 | 7篇 |
1985年 | 23篇 |
1984年 | 22篇 |
1983年 | 19篇 |
1982年 | 25篇 |
1981年 | 8篇 |
1965年 | 14篇 |
1961年 | 8篇 |
1960年 | 6篇 |
1957年 | 11篇 |
1955年 | 16篇 |
1954年 | 9篇 |
排序方式: 共有5399条查询结果,搜索用时 15 毫秒
1.
《Ceramics International》2022,48(1):769-775
Brittle materials generally exhibit size effects, and the mechanical properties of these materials degrade significantly with an increase in size. However, the mathematical law governing the attenuation degree of mechanical properties with the increase in size is still unknown. In this study, maximum loads of differently sized ceramic test strips were subjected to three point bending tests under two working conditions of equal spans and span amplifications, respectively. Subsequently, the theoretical maximum loads of materials were calculated using the finite element method (FEM). By calculating the difference between the calculated values and the actual maximum loads, the attenuation of mechanical properties of ceramic samples were observed. The results show that the theoretical mechanical properties and the performance attenuation caused by the size effect tend to increase according to the following equation: y=ax3+bx2+cx+d. Therefore, mechanical properties and performance attenuation of any sample exhibiting a size within the experimental range can be predicted by a mathematical law, which was obtained through mechanical tests results of four samples with different sizes. The obtained mathematical law holds great significance for predicting the mechanical properties of materials under size effects. 相似文献
2.
Inspired by biological systems in which damage triggers an autonomic healing response, a polymer composite material that can heal itself when cracked has been developed. In this work, compression and tensile properties of a self-healed fibre reinforced epoxy composites were investigated. Microencapsulated epoxy and mercaptan healing agents were incorporated into a glass fibre reinforced epoxy matrix to produce a polymer composite capable of self-healing. The self-repair microcapsules in the epoxy resin would break as a result of microcrack expansion in the matrix, and letting out the strong repair agent to recover the mechanical strength with a relative healing efficiency of up to 140% which is a ratio of healed property value to initial property value or healing efficiency up to 119% if using the healed strength with the damaged strength. 相似文献
3.
《Geotextiles and Geomembranes》2020,48(6):897-911
Dynamic responses of the geosynthetic-encased stone column (GESC) supported embankment under traffic loads have become a hot topic. This study investigates the responses of GESC improved ground under vertical cyclic loading. A series of laboratory tests in a designed model test tank have been carried out with different loading parameters (varied loading amplitudes and frequencies), different column dimensions (varied encasement lengths and column diameters). In the tests, the soil-column stress distribution, accumulated settlement of loading plate, excess pore water pressure in the surrounding soil and lateral bulging of the stone column are monitored. Experimental results indicate that the vertical stress on the stone column increases with the increment of encasement length, and decreases with the increment of column diameter, loading amplitude and loading frequency. The increasing stress on the surrounding soil leads to a greater accumulated settlement of the loading plate and excess pore water pressure, while the increasing stress on the column leads to larger lateral bulging of the column. Excess pore water pressure dissipates effectively through vertical and horizontal drainage channels provided by the stone column and the sand bed. The geosynthetic encasement prevents the clay from obstructing the drainage channel by filtration and guarantees the drainage effect. 相似文献
4.
Ali AREFNIA Ali DEHGHANBANADAKI Khairul Anuar KASSIM 《Frontiers of Structural and Civil Engineering》2021,15(4):1016
This study investigated the use of recycled tire-derived aggregate (TDA) mixed with kaolin as a method of increasing the ultimate bearing capacity ( UBC) of a strip footing. Thirteen 1g physical modeling tests were prepared in a rigid box of 0.6 m × 0.9 m in plan and 0.6 m in height. During sample preparation, 0%, 20%, 40%, or 60% (by weight) of powdery, shredded, small-sized granular (G 1–4 mm) or large-sized granular (G 5–8 mm) TDA was mixed with the kaolin. A strip footing was then placed on the stabilized kaolin and was caused to fail under stress-controlled conditions to determine the UBC. A rigorous 3D finite element analysis was developed in Optum G-3 to determine the UBC values based on the experimental test results. The experimental results showed that, except for the 20% powdery TDA, the TDA showed an increase in the UBC of the strip footing. When kaolin mixed with 20% G (5–8 mm), the UBC showed a threefold increase over that for the unreinforced case. The test with 20% G (1–4 mm) recorded the highest subgrade modulus. It was observed that the UBC calculated using finite element modeling overestimated the experimental UBC by an average of 9%. 相似文献
5.
6.
7.
《岩石力学与岩土工程学报(英文版)》2020,12(6):1214-1225
With rapid development of infrastructures like tunnels and open excavations in Shanghai, investigations on deeper soils have become critically important. Most of the existing laboratory works were focused on the clayey strata up to Layer 6 in Shanghai, i.e. at depth of up to 40 m. In this paper, Layers 7, 9, and 11, which were mostly formed of sandy soils at depth of up to 150 m, were experimentally investigated with respect to physico-mechanical behaviors. The stress–strain behaviors were analyzed by the consolidated drained/undrained (CD/CU) triaxial tests under monotonic loading. One-dimensional (1D) oedometer tests were performed to investigate the consolidation properties of the sandy soils. Specimens were prepared at three different relative densities for each layer. Also, the micro-images and particle size analyzers were used to analyze the shape and size of the sand grains. The influences of grain size, density, and angularity on the stress–strain behaviors and compressibility were also studied. Compared to the other layers, Layer 11 had the smallest mean grain size (D50), highest compressibility, and lowest shear strength. In contrast, Layer 9 had the largest mean grain size, lowest compressibility, and highest shear strength. Layer 7 was of intermediate mean grain size, exhibiting more compressibility and less shear strength than that of Layer 9. Also, the critical state parameters and maximum dilatancy rate of different layers were discussed. 相似文献
8.
The present study focuses on the sintering of silicon carbide-based ceramics (SiC) by liquid phase sintering (LPS) followed by characterization of the produced ceramics. AlN/Re2O3 mixtures were used as additives in the LPS process. In the first step, the LPS-SiC materials were produced in a graphite resistance furnace in the form of discs at different temperatures. The conditions with the best results regarding real density and relative density were taken as reference for sintering in the form of prismatic bars. In the second step, these samples were evaluated regarding fracture toughness (KIC), by the Single Edge V Notch Beam – SEVNB – method, and flexural strength. KIC behavior was evaluated according to the depth and curvature radius of the notches. Reliable KIC values were presented when the ceramic displayed a small curvature radius at the notch tip. When the radius was large, it did not maintain the square root singularity of the notch tip. Tests were carried out to determine KIC values in atmospheric air and water. KIC results were lower in water than air, with a decrease ranging between 2.56% and 11.26%. The observations indicated a direct grain size correlation between KIC values and fracture strength of the SiC ceramics. 相似文献
9.
Field Static Load Test on Kao-Ping-Hsi Cable-Stayed Bridge 总被引:1,自引:0,他引:1
Field load testing is an effective method for understanding the behavior and fundamental characteristics of a cable-stayed bridge. This paper presents the results of field static load tests on the Kao-Ping-Hsi cable-stayed bridge, the longest cable-stayed bridge in Taiwan, before it was open to traffic. A total of 40 loading cases, including the unit and distributed bending and torsion loading effects, were conducted to investigate the bridge behavior. The atmospheric temperature effect on the variations of the main girder deflections was also monitored. The results of static load testing include the main girder deflections, the flexural strains of the prestressed concrete girder, and the variations of the cable forces. A three-dimensional finite-element model was developed. The results show that the bridge under the planned load test conditions has linear superposition characteristics and the analytical model shows a very good agreement with the bridge responses. Further discussion of deflection and cable forces of the design specifications for a cable-stayed bridge is also presented. 相似文献
10.