全文获取类型
收费全文 | 10389篇 |
免费 | 420篇 |
国内免费 | 62篇 |
专业分类
化学 | 7879篇 |
晶体学 | 81篇 |
力学 | 229篇 |
数学 | 1298篇 |
物理学 | 1384篇 |
出版年
2023年 | 72篇 |
2022年 | 90篇 |
2021年 | 126篇 |
2020年 | 206篇 |
2019年 | 167篇 |
2018年 | 129篇 |
2017年 | 115篇 |
2016年 | 268篇 |
2015年 | 251篇 |
2014年 | 287篇 |
2013年 | 511篇 |
2012年 | 743篇 |
2011年 | 917篇 |
2010年 | 434篇 |
2009年 | 284篇 |
2008年 | 669篇 |
2007年 | 728篇 |
2006年 | 767篇 |
2005年 | 749篇 |
2004年 | 591篇 |
2003年 | 502篇 |
2002年 | 434篇 |
2001年 | 111篇 |
2000年 | 105篇 |
1999年 | 100篇 |
1998年 | 91篇 |
1997年 | 101篇 |
1996年 | 120篇 |
1995年 | 84篇 |
1994年 | 88篇 |
1993年 | 73篇 |
1992年 | 65篇 |
1991年 | 63篇 |
1990年 | 49篇 |
1989年 | 34篇 |
1988年 | 44篇 |
1987年 | 33篇 |
1986年 | 21篇 |
1985年 | 82篇 |
1984年 | 49篇 |
1983年 | 33篇 |
1982年 | 60篇 |
1981年 | 59篇 |
1980年 | 48篇 |
1979年 | 46篇 |
1978年 | 42篇 |
1977年 | 38篇 |
1976年 | 31篇 |
1975年 | 35篇 |
1974年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Several 2- and 4-alkylcyclohexadienones were prepared and shown to accept electrons to produce ketyl radical anions that dissociated rapidly at room temperature to release carbon-centered radicals and an aromatic phenoxide type anion. In the PET process with benzyl-substituted cyclohexadienones, initiated with triethylamine, the benzyl radicals dimerised or abstracted an H-atom from solvent. In electrochemical reductions, and in reductions with alkali metals in liquid ammonia, the benzyl radicals were further reduced to anions. 相似文献
12.
13.
Andrew Vince 《Graphs and Combinatorics》1993,9(1):75-84
A short graph theoretic proof of the classification of closed surfaces is given. The new proof has the feature that the symmetric canonical graphs for the surfaces do not correspond to the canonical polygons in the usual proof of the classification. 相似文献
14.
Christopher Batchelor-McAuley Craig E Banks Andrew O Simm Timothy G J Jones Richard G Compton 《Chemphyschem》2006,7(5):1081-1085
The benefits of using nanoparticle-modified electrodes are exemplified through the electrochemical detection of protons and/or hydrogen. It is shown that a palladium-nanoparticle-modified boron-doped diamond allows voltammetric information relating to the relative roles played by the surface and the bulk metal to be obtained for the proton-hydrogen system at palladium surfaces which is not accessible using palladium macroelectrodes or microelectrodes. 相似文献
15.
16.
Andrew Mills Anne Lepre Nicholas Elliott Sharan Bhopal Ivan P. Parkin S. A. ONeill 《Journal of photochemistry and photobiology. A, Chemistry》2003,160(3):213-224
Pilkington Glass Activ™ represents a possible suitable successor to P25 TiO2, especially as a benchmark photocatalyst film for comparing other photocatalyst or PSH self-cleaning films. Activ™ is a glass product with a clear, colourless, effectively invisible, photocatalytic coating of titania that also exhibits PSH. Although not as active as a film of P25 TiO2, Activ™ vastly superior mechanical stability, very reproducible activity and widespread commercial availability makes it highly attractive as a reference photocatalytic film. The photocatalytic and photo-induced superhydrophilitic (PSH) properties of Activ™ are studied in some detail and the results reported. Thus, the kinetics of stearic acid destruction (a 104 electron process) are zero order over the stearic acid range 4–129 monolayers and exhibit formal quantum efficiencies (FQE) of 0.7×10−5 and 10.2×10−5 molecules per photon when irradiated with light of 365±20 and 254 nm, respectively; the latter appears also to be the quantum yield for Activ™ at 254 nm. The kinetics of stearic acid destruction exhibit Langmuir–Hinshelwood-like saturation type kinetics as a function of oxygen partial pressure, with no destruction occurring in the absence of oxygen and the rate of destruction appearing the same in air and oxygen atmospheres. Further kinetic work revealed a Langmuir adsorption type constant for oxygen of 0.45±0.16 kPa−1 and an activation energy of 19±1 kJ mol−1. A study of the PSH properties of Activ™ reveals a high water contact angle (67°) before ultra-bandgap irradiation reduced to 0° after prolonged irradiation. The kinetics of PSH are similar to those reported by others for sol–gel films using a low level of UV light. The kinetics of contact angle recovery in the dark appear monophasic and different to the biphasic kinetics reported recently by others for sol–gel films [J. Phys. Chem. B 107 (2003) 1028]. Overall, Activ™ appears a very suitable reference material for semiconductor film photocatalysis. 相似文献
17.
A classification of homogeneous quaternionic Kähler structures by real tensors is given and related to Fino's representation theoretic decomposition. A relationship between the modules whose dimension grows linearly and quaternionic hyperbolic space is found. To cite this article: M. Castrillón López et al., C. R. Acad. Sci. Paris, Ser. I 338 (2004). 相似文献
18.
Andrew Bach Xinglong Jiang Joseph Mckenna Kapa Prasad Oljan Repic Wen‐Chung Shieh 《Journal of heterocyclic chemistry》2004,41(4):637-640
An efficient approach has been developed for the synthesis of an isofervenulin analogue 1 employing a one‐pot condensation‐substitution reaction of a chlorocarboethoxytriazine (electrophile) with a urea (nucleophile). The resulting cyclization reaction resulted in the synthesis of a pyrimido‐heterocycle in good yield in either acidic or basic media. The former was assisted by utilizing trimethylsilyl chloride. 相似文献
19.
20.