全文获取类型
收费全文 | 21758篇 |
免费 | 1322篇 |
国内免费 | 57篇 |
专业分类
电工技术 | 311篇 |
综合类 | 25篇 |
化学工业 | 4894篇 |
金属工艺 | 879篇 |
机械仪表 | 1302篇 |
建筑科学 | 426篇 |
矿业工程 | 6篇 |
能源动力 | 864篇 |
轻工业 | 1850篇 |
水利工程 | 91篇 |
石油天然气 | 16篇 |
无线电 | 3655篇 |
一般工业技术 | 4628篇 |
冶金工业 | 1541篇 |
原子能技术 | 291篇 |
自动化技术 | 2358篇 |
出版年
2024年 | 22篇 |
2023年 | 275篇 |
2022年 | 399篇 |
2021年 | 684篇 |
2020年 | 470篇 |
2019年 | 497篇 |
2018年 | 699篇 |
2017年 | 661篇 |
2016年 | 768篇 |
2015年 | 602篇 |
2014年 | 938篇 |
2013年 | 1389篇 |
2012年 | 1456篇 |
2011年 | 1789篇 |
2010年 | 1299篇 |
2009年 | 1332篇 |
2008年 | 1211篇 |
2007年 | 937篇 |
2006年 | 814篇 |
2005年 | 708篇 |
2004年 | 638篇 |
2003年 | 586篇 |
2002年 | 593篇 |
2001年 | 517篇 |
2000年 | 439篇 |
1999年 | 423篇 |
1998年 | 709篇 |
1997年 | 420篇 |
1996年 | 395篇 |
1995年 | 257篇 |
1994年 | 169篇 |
1993年 | 151篇 |
1992年 | 112篇 |
1991年 | 100篇 |
1990年 | 75篇 |
1989年 | 88篇 |
1988年 | 74篇 |
1987年 | 63篇 |
1986年 | 51篇 |
1985年 | 43篇 |
1984年 | 36篇 |
1983年 | 28篇 |
1982年 | 31篇 |
1981年 | 26篇 |
1980年 | 29篇 |
1979年 | 13篇 |
1977年 | 22篇 |
1976年 | 33篇 |
1975年 | 17篇 |
1974年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
Effect of Sintering Temperature on Thermoelectric Properties of p‐Bi2Te3 Alloys Produced by Gas Atomization 下载免费PDF全文
Babu Madavali Hyo‐Seob Kim Min‐Gyu Choi Gi‐Chan Park Jar‐Myung Koo Hyeon‐Taek Son Soon‐Jik Hong 《International Journal of Applied Ceramic Technology》2016,13(2):245-251
In this research, p‐type Bi2Te3–75% Sb2Te3 thermoelectric alloy powders were produced by gas atomization and subsequently sintered by hot pressing at different temperatures. The grain growth of the hot‐pressed samples was observed with increasing sintering temperature from 380°C to 460°C. The compressive strength increased with increasing hot‐pressing temperature due to the high relative density of bulk samples obtained at high temperatures. The effect of sintering temperature on thermoelectric (TE) properties was studied. The maximum power factor 3.48 mW/mK2 was obtained for the sample hot pressed at 420°C due to the resulting high electrical conductivity and enhanced Seebeck coefficient values. 相似文献
972.
Mechanical Properties of Submicrometer‐Grained Transparent Yttria Ceramics by Hot Pressing with Hot‐Isostatic Pressing 下载免费PDF全文
Lin Gan Young‐Jo Park Haneul Kim Jin‐Myung Kim Jae‐Woong Ko Jae‐Wook Lee 《International Journal of Applied Ceramic Technology》2016,13(4):678-684
Here, we report the fabrication and mechanical properties of submicrometer‐grained (0.29–0.58 μm) transparent yttria ceramics by hot pressing combined with hot‐isostatic pressing. The effects of the grain size on the microhardness and the fracture toughness were studied. An unusual decrease of the fracture toughness with an increase in the grain size was revealed, which may be attributed to the different grain size dependence of the fracture behavior of the ZrO2‐doped yttria ceramics compared to that of other yttria ceramics. The microhardness and fracture toughness of the transparent yttria ceramics were found to be better than those of the large‐grained yttria ceramics. 相似文献
973.
Yeonjung Han Yonggun Park Jun-Ho Park Sang-Yun Yang Chang-Deuk Eom 《Drying Technology》2016,34(13):1613-1620
This work focused on the shrinkage and drying stress of red pine (Pinus densiflora) wood during kiln drying and investigated transverse shrinkage and moisture changes in thin specimens using digital image analysis and near-infrared spectroscopy, respectively. The effect of specimen thickness, which ranged from 1 to 10?mm on shrinkage, was analyzed under drying conditions with restrained stresses. The shrinkage due to moisture content was presented in the form of an exponential function and a linear function above and below the fiber saturation point, respectively. A shorter existence of the moisture gradient increased the transverse shrinkage. The tangential and radial shrinkage at the tissue level in 30-µm (longitudinal) thick slices was measured and compared with the shrinkage of above specimens with difference thicknesses. The transverse shrinkage of 1-mm-thick specimen is similar to the shrinkage measured using 30-µm-thick slice. 相似文献
974.
Application of Gurson Model for Evaluation of Density‐Dependent Mechanical Behavior of Polyurethane Foam: Comparative Study on Explicit and Implicit Method 下载免费PDF全文
Recently, liquefied natural gas (LNG) is a focus of interest around the world for several reasons, and LNG cargo containment systems (CCS) increase in quality to prevent loss of LNG during shipping. For insulation of CCS, polyurethane foam (PUF), an outstanding insulation material, is commonly used. However, until now, although its mechanical properties are relatively good, the material is not considered as a structural member under compressive loading, principal load direction in CCS. Moreover, as PUF is a porous material by mixing and foaming, its mechanical properties depend on voids, which is a dominant parameter for density. Therefore, in the present study, nonlinear behavior of PUF is described using Gurson model with a novel technique, i.e., an acceleration factor. The model expresses the behavior through the volume fraction of voids with consideration of the density effect to evaluate structural performance using user‐defined material subroutine with explicit and implicit methods.
975.
976.
977.
Kyung-Wan Kang Hyoung-Ho Doh Jung-Hyeon Park Dong-Ho Lee 《The International Journal of Advanced Manufacturing Technology》2016,82(9-12):1463-1473
We consider two interrelated problems that occurred in disassembly systems: disassembly leveling and lot sizing. Disassembly leveling, one of disassembly process planning decisions, is to determine disassembly structures that specify parts and/or subassemblies to be obtained from disassembling used/end-of-life products, and disassembly lot sizing is the problem of determining the amounts of disassembly operations required to satisfy the demands of their parts and/or subassemblies. Unlike the existing studies, this study considers the two problems at the same time for the objective of minimizing the sum of disassembly setup and operation costs. In particular, we consider a generalized version in which disassembly levels may be different even for products of the same type. Two types of the problem are considered in this study. The first one is the basic problem without parts commonality, i.e., products do not share their parts or subassemblies, for which a polynomial time optimal algorithm is suggested after developing a mathematical programming model. The second one is an extended problem with parts commonality. After developing another mathematical programming model for the extension, we prove that it is NP hard. Then, a heuristic algorithm is suggested together with its computational results. 相似文献
978.
Jong-ha Park Soo-sang Park Xue-feng Han Kyung-woo Yi 《Metals and Materials International》2016,22(1):118-128
To understand complex behavior in the smelting furnace of Mitsubishi continuous process for copper refining, comprehensive 3-D numerical simulation and field experiment were performed. The numerical simulation results showed that strong and complex velocity fields of gas, matte and slag were generated in the furnace and large amounts of matte and slag were splashed into the gas area. Temperature measurements at the lance during field operation revealed that wide range of temperature variation appeared depending on the injection condition of concentrates. Numerical simulation results provided good agreements with experiments results and showed that the chemical reaction induces temperature increase during gas injection period. On the other hand, lance temperature is decreasing because of cold concentrates during gas and particles injection period. From the FFT analysis results, the fluctuations of matte and slag volume fraction near the lance induce temperature fluctuations of the lance. Through these experimental and simulation results, it was revealed that the lances in the smelting furnace were exposed to severe conditions such as high temperature, repeated large temperature change and cyclic change of large temperature gradient across the thickness. 相似文献
979.
Jong Min Byun Su-Ryong Bang Chun Woong Park Myung-Jin Suk Young Do Kim 《Metals and Materials International》2016,22(1):81-86
In general, size, shape and dispersion of phases in alloys significantly affect mechanical properties. In this study, the mechanical properties of Mo-Si-B alloys were experimentally investigated with regards to the refinement of intermetallic compound. To confirm the size effect of the intermetallic compound phases on mechanical properties, two differently sized intermetallic compound powders consisting Mo5SiB2 and Mo3Si were fabricated by mechano-chemical process and high-energy ball milling. A modified powder metallurgy method was used with core-shell intermetallic powders where the intermetallic compound particles were the core and nano-sized Mo particles which formed by the hydrogen reduction of Mo oxide were the shells, leading to the microstructures with uniformly distributed intermetallic compound phases within a continuous α-Mo matrix phase. Vickers hardness and fracture toughness were measured to examine the mechanical properties of sintered bodies. Vickers hardness was 472 Hv for the fine intermetallic compound powder and 415 Hv for the coarse intermetallic compound powder. The fracture toughness was 12.4 MPa·√m for the fine IMC powders and 13.5 MPa·√m for the coarse intermetallic compound powder. 相似文献
980.
Kang?Hyun?Choi Hyun-Su?Kim Chang?Hyun?Park Gon-Ho?Kim Kyoung?Ho?Baik Sung?Ho?Lee Taehyung?Kim Hyoung?Seop?KimEmail author 《Metals and Materials International》2016,22(5):817-824
Thermal barrier coatings are widely used in aerospace industries to protect exterior surfaces from harsh environments. In this study, functionally graded materials (FGMs) were investigated with the aim to optimize their high temperature resistance and strength characteristics. NiCrAlY bond coats were deposited on Inconel-617 superalloy substrate specimens by the low vacuum plasma spraying technique. Functionally graded Ni-yttria-stabilized zirconia (YSZ) coatings with gradually varying amounts of YSZ (20%-100%) were fabricated from composite powders by vacuum plasma spraying. Heat shield performance tests were conducted using a high- temperature plasma torch. The temperature distributions were measured using thermocouples at the interfaces of the FGM layers during the tests. A model for predicting the temperature at the bond coating–substrate interface was established. The temperature distributions simulated using the finite element method agreed well with the experimental results. 相似文献