全文获取类型
收费全文 | 1855篇 |
免费 | 187篇 |
国内免费 | 209篇 |
专业分类
电工技术 | 21篇 |
综合类 | 214篇 |
化学工业 | 121篇 |
金属工艺 | 374篇 |
机械仪表 | 476篇 |
建筑科学 | 17篇 |
矿业工程 | 20篇 |
能源动力 | 105篇 |
轻工业 | 33篇 |
水利工程 | 6篇 |
石油天然气 | 5篇 |
武器工业 | 17篇 |
无线电 | 163篇 |
一般工业技术 | 410篇 |
冶金工业 | 57篇 |
原子能技术 | 4篇 |
自动化技术 | 208篇 |
出版年
2024年 | 1篇 |
2023年 | 27篇 |
2022年 | 26篇 |
2021年 | 37篇 |
2020年 | 52篇 |
2019年 | 51篇 |
2018年 | 27篇 |
2017年 | 23篇 |
2016年 | 43篇 |
2015年 | 41篇 |
2014年 | 76篇 |
2013年 | 110篇 |
2012年 | 143篇 |
2011年 | 201篇 |
2010年 | 169篇 |
2009年 | 184篇 |
2008年 | 119篇 |
2007年 | 208篇 |
2006年 | 237篇 |
2005年 | 77篇 |
2004年 | 57篇 |
2003年 | 48篇 |
2002年 | 38篇 |
2001年 | 32篇 |
2000年 | 56篇 |
1999年 | 31篇 |
1998年 | 27篇 |
1997年 | 20篇 |
1996年 | 18篇 |
1995年 | 15篇 |
1994年 | 10篇 |
1993年 | 13篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1984年 | 1篇 |
1981年 | 3篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1976年 | 3篇 |
排序方式: 共有2251条查询结果,搜索用时 15 毫秒
61.
62.
Temperature control of optical focal planes comes with the intrinsic challenge of creating a pathway that is both extremely flexible mechanically and highly conductive thermally. The task is further complicated because science-caliber optical focal planes are extremely delicate, yet time, cost, and their unique nature means that their mechanical resiliency is rarely tested and documented. The mechanical engineer tasked with the thermo-mechanical design must then create a highly conductive thermal link that minimizes the tensile and shear stresses transmitted to the focal plane without design parameters on an acceptable stiffness and without data on the stiffness of previously implemented thermal links.This paper describes the development and testing of the thermal link developed for the Portable Remote Imaging Spectrometer (PRISM) instrument. It will provide experimentally determined mechanical stiffness plots in the three axes of interest. Analytical and experimental thermal conductance results for the two-arm focal-plane thermal strap (TAFTS), from cryogenic to room temperatures, are also presented. The paper also briefly describes some elements of the fabrication process followed in developing a novel design solution, which provides high conductance and symmetrical mechanical loading, while providing enhanced flexibility in all three dimensions. 相似文献
63.
This paper presents a link adaptation algorithm dedicated for 100 Gbps wireless transmission. Interleaved Reed-Solomon codes are selected as forward error correction (FEC) algorithms. The redundancy of the codes is selected according to the channel bit error rate (BER). The uncomplicated FEC scheme allows implementing a complete data link layer processor in an FPGA (field programmable gate array). In our case, we use the Virtex7 FPGA to validate the functionality of our implementation. The proposed FPGA-processor achieves 169 Gbps throughput. Moreover, the implementation is synthesized into 40 nm CMOS technology and the described link adaptation algorithm allows reducing consumed energy per bit to values below 1 pJ/bit at BER <1e−4. With higher BER, the energy increases up to ∼13 pJ/bit. 相似文献
64.
Journal of Failure Analysis and Prevention - To investigate the strength and fatigue life of a fracture-split connecting rod, this study combines experiments on connecting rod fracture splitting,... 相似文献
65.
The importance of material fatigue information in design has been well recognized. There are a few existing fatigue life prediction methods based on materials tensile properties. Some of these fatigue life prediction methods can be successfully applied for non-heat affected materials. However, industrial components, such as pressure vessel and pipelines are commonly constructed by welding parts together. The fatigue lives of welded section and its surrounding material could be greatly affected by the welding process. Therefore, it is beneficial to develop a fatigue life prediction model for the weld and surrounding heat affected zone (HAZ) materials based on their tensile testing data. In this paper, fatigue lives of base material and its weld and HAZ materials for constructing coke drums are studied. Mechanical properties are first obtained from the tensile tests. Then, fully-reversed strain-controlled fatigue tests were performed. It is found that the fatigue life of pure base material is roughly twice of the weld and four time of the HAZ at the same strain amplitude. Four-point correlation (FPC) method by Manson can reasonably predict the life of base material. However, it over-predicts the lives of weld and HAZ. By introducing two reduction factors Rplastic and Relastic for the weld and HAZ material respectively into the FPC method, the over-prediction can be rectified. Therefore, the proposed modified FPC method could be applied in predicting fatigue lives of weld and HAZ materials. 相似文献
66.
Y. F. Yang H. Y. Wang J. G. Wang Q. C. Jiang 《Metallurgical and Materials Transactions A》2009,40(11):2514-2518
The ignition temperature of the thermal explosion reaction from the Ti-C system under air is much lower than that under Ar
atmosphere. The ignition mechanism for the Ti-C system under air is determined to be a mechanism of chemical oven, and the
reaction mechanism is dissolution, reaction, and precipitation. Namely, the heat generated from the oxidation and nitrification
of Ti and C can promote the melting of Ti inside the compact; subsequently, the carbon atoms dissolve into the Ti melt and
TiC precipitate. 相似文献
67.
为了能实现对轻、薄、小物料的稳定输送,提出了一种压电双晶片为驱动源配重式直线振动输送器。设计了压电振动输送器的结构并分析了其工作原理,建立了系统的动力学模型,推导出了双自由度系统的振动位移表达式以及近似得到系统的固有频率,制作了振动输送器的样机,并进行了试验测试。试验结果表明:在系统共振频率为120.5Hz,料道振动位移达到最大,3个测试点分别为39μm,34μm,37μm,但不影响物料输送,工作频率范围为117~124Hz,处于共振频率最大输送速度达到52mm/s。与同型号的电磁式振动输送器相比,在共振条件下研制的样机的电流仅为电磁式的16.58%,速度是其1.36倍,振幅为电磁式的32.38%,噪音降低了33dB。设计的输送器具有送速度稳定、节能、噪音小等优点。 相似文献
68.
Nanosized Cu-doped TiO2 film was prepared by the sol–gel spin coating technique. XPS analysis showed that Cu atoms had been successfully doped into TiO2 lattice, which hence modified the surface chemical composition. As a result, the Cu-doped TiO2 thin film possessed a superhydrophilic surface with a water contact angle (WCA) only 5.1° and exhibited excellent anti-fogging behavior. The Cu-doped TiO2 thin film also exhibited a much better photocatalytic activity than the reference TiO2 thin film, as evaluated by the degradation of 10 mg/L methylene blue (MB) solution under simulated solar-driven irradiation. 相似文献
69.
70.
The role of magnesium segregation in the intergranular stress corrosion cracking of aluminium alloys
《Corrosion Science》1987,27(4):329-347
Stress corrosion susceptibility of aluminium alloys has been related to the grain boundary segregation of magnesium. In this paper segregation mechanisms are reviewed and examined with reference to both direct and indirect experimental evidence for magnesium segregation. Important parameters considered are the solution heat treatment temperature and the effect of grain boundary precipitation. Evidence to support both equilibrium and non-equilibrium segregation of magnesium is presented. Significantly magnesium segregation promotes hydrogen entry into aluminium but in isolation is not responsible for cracking susceptibility which depends on a critical grain boundary precipitate/hydrogen interaction. 相似文献