全文获取类型
收费全文 | 197947篇 |
免费 | 23933篇 |
国内免费 | 17039篇 |
专业分类
电工技术 | 19124篇 |
综合类 | 21372篇 |
化学工业 | 23120篇 |
金属工艺 | 13954篇 |
机械仪表 | 14411篇 |
建筑科学 | 15198篇 |
矿业工程 | 7791篇 |
能源动力 | 5384篇 |
轻工业 | 22916篇 |
水利工程 | 7213篇 |
石油天然气 | 6182篇 |
武器工业 | 2762篇 |
无线电 | 21014篇 |
一般工业技术 | 16204篇 |
冶金工业 | 7772篇 |
原子能技术 | 3960篇 |
自动化技术 | 30542篇 |
出版年
2024年 | 1293篇 |
2023年 | 3284篇 |
2022年 | 7904篇 |
2021年 | 10085篇 |
2020年 | 7354篇 |
2019年 | 4899篇 |
2018年 | 5144篇 |
2017年 | 6085篇 |
2016年 | 5411篇 |
2015年 | 8761篇 |
2014年 | 11054篇 |
2013年 | 13020篇 |
2012年 | 16353篇 |
2011年 | 16781篇 |
2010年 | 16651篇 |
2009年 | 15823篇 |
2008年 | 16523篇 |
2007年 | 16318篇 |
2006年 | 13600篇 |
2005年 | 11305篇 |
2004年 | 8312篇 |
2003年 | 5392篇 |
2002年 | 5033篇 |
2001年 | 4903篇 |
2000年 | 3831篇 |
1999年 | 1409篇 |
1998年 | 399篇 |
1997年 | 330篇 |
1996年 | 234篇 |
1995年 | 198篇 |
1994年 | 139篇 |
1993年 | 175篇 |
1992年 | 123篇 |
1991年 | 88篇 |
1990年 | 84篇 |
1989年 | 98篇 |
1988年 | 64篇 |
1987年 | 60篇 |
1986年 | 55篇 |
1985年 | 28篇 |
1984年 | 19篇 |
1983年 | 23篇 |
1982年 | 18篇 |
1981年 | 34篇 |
1980年 | 69篇 |
1979年 | 35篇 |
1977年 | 6篇 |
1976年 | 7篇 |
1959年 | 33篇 |
1951年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
52.
53.
本文研究了具有典型分解特征的Al-Zn-Ce非晶合金的形成和晶化过程,探讨了各种相的生成顺序。XRD和DSC测试结果表明强烈的化合物短程序有利于Al-Zn-Ce非晶合金的形成。在Al-Zn-Ce非晶合金的晶化过程中存在复杂的相选择行为,多种相的竞争形核和有限生长使其具有复杂的结构特点。同时,结果也表明冷速对该体系非晶的形成有很大影响。 相似文献
54.
武付华 《广东工业大学高等工程教育研究》2007,7(3):34-35,41
马克思以实践为出发点和指导原则,创立了马克思主义哲学理论。正确理解和把握马克思主义实践哲学的科学意蕴,具有重要意义。 相似文献
55.
L. T. MO M. HUURMAN S. P. WU A. A. A. MOLENAAR 《Fatigue & Fracture of Engineering Materials & Structures》2007,30(9):823-831
Tensile fatigue behaviours of bitumen–stone adhesion were investigated using a dynamic mechanics analyser under stress‐controlled mode at two temperatures of 5 and 25°C and various controlled‐stress levels. Failure characteristics including interfacial failure and cohesive failure were examined using image analysis of fracture surfaces. Finite‐element analysis on stress distributions was conducted under different temperatures, film thickness and interfacial bonding conditions. A Coulomb–Mohr like criterion in combination with shear and normal stresses is proposed to deal with the extreme thin adhesive layer, which can be further simplified into an adhesive zone without significant loss of accuracy for stress analysis. 相似文献
56.
控轧技术在H型钢生产中的应用 总被引:2,自引:0,他引:2
根据钢板的控轧经验,结合H型钢轧制的特点分析控轧在轧制中运用的具体问题,制定H型钢控轧工艺方案。介绍了实际应用情况,并提出改进的措施。 相似文献
57.
Itwasreported[1] thatthemicro stereostructureofprimaryausteniteincastironconsistsofprimarystemsandsecondaryarmsthat growaccordingtodendritecrystalsbranchrule ,andsomeofprimaryausteniteevenhavethirdarms .MiyakeHetal[2 ]proposedaconceptofregionmodelbystudying… 相似文献
58.
The behaviour of hydrogen permeation and diffusion in amorphous alloy Ni68Cr7Si8B14Fe3 hasbeen investigated by an ultrahigh vacuum gas permeation technique. A comparison experimentwas carried out between the as-quenched and annealed States (400℃/2h) of the amorphousalloy. The results show that, for both states of the amorphous alloy in the temperature rangeof 200~350℃, the diffusivity and permeability of hydrogen are in agreement with Arrheniusrelationship, there does not exist H-trapping effect, and the activation energies of diffusion andpermeation almost keep the same. 相似文献
59.
S Modi DE Gilham MJ Sutcliffe LY Lian WU Primrose CR Wolf GC Roberts 《Canadian Metallurgical Quarterly》1997,36(15):4461-4470
1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a neurotoxin that produces Parkinsonism symptoms in man, has been examined as a substrate of recombinant human cytochrome P450 2D6. When cumene hydroperoxide is used as an oxygen and electron donor, a single product is formed, identified as 4-phenyl-1,2,3,6-tetrahydropyridine. The K(m) for formation of this product (130 microM) is in agreement with the dissociation constants for MPTP binding to the enzyme determined by optical and nuclear magnetic resonance (NMR) spectroscopy. When the reaction is carried out with nicotinamide adenine dinucleotide phosphate (reduced) (NADPH) and recombinant human NADPH-cytochrome P450 reductase, a second product, identified as 1-methyl-4-(4'-hydroxyphenyl)-1,2,3,6-tetrahydropyridine, is formed in addition to 4-phenyl-1,2,3,6-tetrahydropyridine. The K(m) values for formation of these two products are 19 microM and 120 microM, respectively. Paramagnetic relaxation experiments have been used to measure distances between the protons of bound MPTP and the heme iron, and these have been used to construct models for the position and orientation of MPTP in the active site. For the cytochrome alone, a single mode of binding was observed, with the N-methyl close to the heme iron in a position appropriate for the observed N-demethylation reaction. In the presence of the reductase, the data were not consistent with a single mode of binding but could be explained by the existence of two alternative orientations of MPTP in the active site. One of these, characterized by a dissociation constant of 150 microM, is essentially identical to that observed in the absence of the reductase. In the second, which has a K(d) of 25 microM, the MPTP is oriented so that the aromatic ring is close to the heme iron, in a position appropriate for p-hydroxylation leading to the formation of the product seen only in the presence of the reductase. In the case of codeine, another substrate for cytochrome P450 2D6, the addition of reductase had no effect on the nature of the product formed, the dissociation constant, or the orientation in the binding site. These observations show that NADPH-cytochrome P450 reductase has an allosteric effect on the active site of cytochrome P450 2D6 that affects the binding of some substrates but not others. 相似文献
60.