全文获取类型
收费全文 | 18475篇 |
免费 | 1732篇 |
国内免费 | 852篇 |
专业分类
电工技术 | 1192篇 |
综合类 | 1218篇 |
化学工业 | 2699篇 |
金属工艺 | 1251篇 |
机械仪表 | 1237篇 |
建筑科学 | 1460篇 |
矿业工程 | 646篇 |
能源动力 | 427篇 |
轻工业 | 1492篇 |
水利工程 | 343篇 |
石油天然气 | 1268篇 |
武器工业 | 166篇 |
无线电 | 2079篇 |
一般工业技术 | 2129篇 |
冶金工业 | 907篇 |
原子能技术 | 147篇 |
自动化技术 | 2398篇 |
出版年
2024年 | 113篇 |
2023年 | 353篇 |
2022年 | 588篇 |
2021年 | 803篇 |
2020年 | 619篇 |
2019年 | 513篇 |
2018年 | 533篇 |
2017年 | 635篇 |
2016年 | 513篇 |
2015年 | 746篇 |
2014年 | 966篇 |
2013年 | 1066篇 |
2012年 | 1172篇 |
2011年 | 1227篇 |
2010年 | 1111篇 |
2009年 | 1091篇 |
2008年 | 1026篇 |
2007年 | 984篇 |
2006年 | 1088篇 |
2005年 | 1006篇 |
2004年 | 632篇 |
2003年 | 571篇 |
2002年 | 538篇 |
2001年 | 424篇 |
2000年 | 418篇 |
1999年 | 423篇 |
1998年 | 364篇 |
1997年 | 318篇 |
1996年 | 280篇 |
1995年 | 242篇 |
1994年 | 184篇 |
1993年 | 117篇 |
1992年 | 91篇 |
1991年 | 68篇 |
1990年 | 58篇 |
1989年 | 53篇 |
1988年 | 42篇 |
1987年 | 22篇 |
1986年 | 15篇 |
1985年 | 10篇 |
1984年 | 9篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1980年 | 2篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Y. Yang B. F. Wang J. Xiong Y. Zeng Z. P. Chen X. Y. Yang 《Metallurgical and Materials Transactions A》2006,37(10):3131-3137
The microstructure and microtexture in adiabatic shear bands (ASBs) on the titanium side in the titanium/mild steel explosive
cladding interface are investigated by means of optical microscopy, scanning electron microscopy/electron backscattered diffraction
(SEM/EBSD), and transmission electron microscopy (TEM). Highly elongated subgrains and fine equiaxed grains with low dislocation
density are observed in the ASBs. Microtextures (25 deg, 75 deg, 0 deg), (70 deg, 45 deg, 0 deg), and (0 deg, 15 deg, 30 deg)
formed within the ASBs suggest the occurrence of the recrystallization. The grain boundaries within ASBs are geometrically
necessary boundaries (GNBs) with high angles. Finite element computations are performed to obtain the effective strain and
temperature distributions within the ASBs under the measured boundary conditions. The rotation dynamic recrystallization (RDR)
mechanism is employed to describe the kinetics of the nanograins’ formation and the recrystallized process within ASBs. During
the deformation time (about 5 to 10 μs), the following processes take place: dislocations accumulate to form elongated cell
structures, cell structures break up to form subgrains, and subgrains rotate and finally form recrystallized grains. The small
grains within ASBs are formed during the deformation and do not undergo significant growth by grain boundary migration after
deformation. 相似文献
32.
33.
Sihai Chen Xinjian Yi Hong Ma Tao Xiong Hongcheng Wang Caijun Ke 《Journal of Infrared, Millimeter and Terahertz Waves》2004,25(1):157-163
This paper presents a method to make vanadium dioxide (VO2) crystallites on silicon substrates by reactive ion beam sputtering. The thickness of the thin film is about 100nm. The phase transition temperature of VO2 is 65°C. The transmittance of the semiconducting phase VO2 is about 50% and it is reduced to as low as 3% in metal phase at the infrared wavelenghth spectrum. The extinction ratio of the optical switches is 12dB. and the insertion loss is of 1-2dB. The switching time is about 1ms. 相似文献
34.
35.
叙述了Quilone试剂的合成,改性脲醛树脂的原理、实验方法、改性后脲醛树脂的抗水性、抗渗透性、耐化学药品性及其影响因素。 相似文献
36.
Objective To study on the role of thymus transplantation for heart allograft in rats. Methods Vascularized heart-thymus combined transplantation was performed with microsurgical technique. Graft survival, histopathology,
level of IL-2, IL-4 and its mRNA expression in serum and cardiac grafts were investigated. Results Heart-thymus combined transplantation achieved effect in the prolongation of cardiac graft survival with short-term administration
of cyclosporine. Conclusions Vascularized thymus transplantation induced immune tolerance in thymectomized rats. 相似文献
37.
38.
An analytical solution of the dependence of the field distribution on the three-spatial coordinates in a permanent-magnet (PM) disk machine is obtained using the concept of magnetic charge and the method of images. A good correlation between the analytical solution and experimental data validates the method described. It is further indicated how this method can be extended to more complex problems. It is applicable to other PM machines, such as permanent-magnet linear synchronous motors.<> 相似文献
39.
E Aida Pea‐Ramos Youling L Xiong Guillermo E Arteaga 《Journal of the science of food and agriculture》2004,84(14):1908-1918
Whey protein isolate (WPI) was hydrolysed for 1 h using Alcalase, Protamex and Flavourzyme. Native WPI, hydrolysed WPI and two commercial WPI hydrolysates were subjected to fractionation by size exclusion chromatography. Antioxidant activity of WPI fractions was measured with a liposome‐oxidising system (50 µM FeCl3/0.1 µM ascorbate, pH 7.0). Lipid oxidation was measured as thiobarbituric acid‐reactive substances (TBARS). Gel electrophoresis and amino acid analysis were run to identify the peptide composition. The influence of amino acid composition on antioxidant activity was evaluated using multivariate analysis methods (correlation analysis, principal component analysis, multiple linear regression and discriminant analysis). TBARS assays indicated the presence of antioxidant activity in all protein fractions, including non‐hydrolysed WPI. For native and hydrolysed WPI samples the first fraction (> 45 kDa) showed a higher TBARS inhibition effect (24–27%) when compared with lower‐molecular‐weight fractions and hydrolysate mixtures. In contrast, for commercial WPI hydrolysates a higher inhibitory effect was found in most of the lower‐molecular‐weight fractions (30–55%). The ability of WPI fractions to delay lipid oxidation was found to be related to the prevalence of histidine and hydrophobic amino acids. Copyright © 2004 Society of Chemical Industry 相似文献
40.
Branched polyacrylonitrile (PAN) was prepared through a self‐condensing vinyl copolymerization of acrylonitrile and 2‐(2‐bromopropionyloxy)ethyl acrylate (BPEA). The branched architecture of the product was confirmed by NMR spectra and the average degree of branching (DB ) was estimated. Through a comparison of the intrinsic viscosity of the product with that of its linear analogue, the contraction factor g′ was calculated. It was found that the viscosity of the branched PAN was obviously lower that that of linear PAN. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献