全文获取类型
收费全文 | 3088篇 |
免费 | 116篇 |
国内免费 | 7篇 |
专业分类
化学 | 2435篇 |
晶体学 | 35篇 |
力学 | 70篇 |
数学 | 98篇 |
物理学 | 573篇 |
出版年
2022年 | 21篇 |
2021年 | 30篇 |
2020年 | 50篇 |
2019年 | 48篇 |
2018年 | 38篇 |
2017年 | 15篇 |
2016年 | 64篇 |
2015年 | 53篇 |
2014年 | 50篇 |
2013年 | 136篇 |
2012年 | 140篇 |
2011年 | 162篇 |
2010年 | 70篇 |
2009年 | 92篇 |
2008年 | 180篇 |
2007年 | 181篇 |
2006年 | 186篇 |
2005年 | 173篇 |
2004年 | 148篇 |
2003年 | 131篇 |
2002年 | 114篇 |
2001年 | 67篇 |
2000年 | 70篇 |
1999年 | 44篇 |
1998年 | 19篇 |
1997年 | 29篇 |
1996年 | 37篇 |
1995年 | 38篇 |
1994年 | 41篇 |
1993年 | 29篇 |
1992年 | 50篇 |
1991年 | 36篇 |
1990年 | 42篇 |
1989年 | 47篇 |
1988年 | 40篇 |
1987年 | 34篇 |
1986年 | 29篇 |
1985年 | 68篇 |
1984年 | 60篇 |
1983年 | 20篇 |
1982年 | 37篇 |
1981年 | 26篇 |
1980年 | 31篇 |
1979年 | 40篇 |
1978年 | 32篇 |
1977年 | 25篇 |
1976年 | 33篇 |
1975年 | 20篇 |
1974年 | 16篇 |
1973年 | 15篇 |
排序方式: 共有3211条查询结果,搜索用时 46 毫秒
81.
Yasuyuki Takeda Chihiro Takagi 《Journal of inclusion phenomena and macrocyclic chemistry》1994,17(1):93-97
The theory is derived to determine the dimer-formation constant,K
2, of a crown ethermetal salt 111 complex in organic solvents of low dielectric constant by solvent extraction. The theoretical predictions are verified experimentally by extraction of sodium picrate (NaA) with 15-crown-5 (15C5) into carbon tetrachloride. All the experiments were conducted at 25°C. The logK
2 value of the Na(15C5)A complex in carbon tetrachloride has been determined to be 4.05±0.11. Moreover, the partition constant of the complex is calculated. 相似文献
82.
83.
Wang J Beton PH Mori N Eaves L Buhmann H Mansouri L Main PC Foster TJ Henini M 《Physical review letters》1994,73(8):1146-1149
84.
Ar+ sputtering of an Cu(111) surface while simultaneously supplying Mo atoms is known to induce an oriented growth of Mo thin crystals, or seed-layers, on evolving conical Cu protrusions. The seed-layers thus formed are shown to be dual-oriented, or bicrystalline, consisting of columnar crystallites grown homo-epitaxially. The orientation relationship between the two types of crystallites was (100)I (111)II with [001]I [110]II, and this bicrystallinity probably resulted from a non-uniform charge-up of the layers' growth front. As concluded from high-resolution electron microscopy, the Mo(100) stacking is elastically converted into the Mo(111) stacking and vice versa, under the influence of tensile stress. The homo-epitaxy that the seed-layers exhibited is believed to reflect the mutual convertibility of the Mo(100) and (111) stackings. 相似文献
85.
K. Nishimura S. Ohya K. Heiguchi S. Muto Y. Isikawa K. Mori 《Hyperfine Interactions》1993,78(1-4):475-479
A magnetic property of Pm as an impurity in PrNi single crystal was investigated by means of the low-temperature nuclear orientation of143,144Pm. The angular distribution of -ray anisotropies revealed that the direction of hyperfine field experienced by the nuclei lie in the (a, c) plane andmade an angle of 60° (5) or 240° (5) with respect to the crystallinec-axis. From the temperature dependence of the anisotropies the strength of the hyperfine field of Pm in PrNi was deduced to be 185(22)T. The hyperfine field of Co at the Ni site of PrNi was found to be less than 4T. 相似文献
86.
Allen WH Bond IA Budding E Conway MJ Daniel A Fenton KB Fujii H Fujii Z Hayashida N Hibino K Honda M Humble JE Kabe S Kasahara K Kifune T Lythe GD Masaike A Matsubara Y Mitsui K Miura Y Mori M Muraki Y Nagano M Nakamura T Nishizawa M Morris PM Ogio S Saito T Sakata M Sato H Shimizu HM Spencer M Storey JR Tanimori T Teshima M Torii S Wadsworth A Watase Y Woodhams MD Yamamoto Y Yock PC Yuda T 《Physical review D: Particles and fields》1993,48(2):466-478
87.
Akinori Mori 《Tetrahedron》2006,62(51):11925-11932
While Pd/C is one of the most useful catalysts for hydrogenation, the high catalyst activity of Pd/C causes difficulty in its application to chemoselective hydrogenation between different types of reducible functionalities. In order to achieve chemoselective hydrogenation using Pd/C, we investigated catalyst poison as a controller of the catalyst activity. We found that the addition of Ph2S (diphenylsulfide) to the Pd/C-catalyzed hydrogenation reaction mixture led to reasonable deactivation of Pd/C. By the use of the Pd/C-Ph2S catalytic system, olefins, acetylenes, and azides can be selectively reduced in the coexistence of aromatic carbonyls, aromatic halides, cyano groups, benzyl esters, and N-Cbz (benzyloxycarbonyl) protecting groups. The present method is promising as a general and practical chemoselective hydrogenation process in synthetic organic chemistry. 相似文献
88.
Recently, we reported that multi-hollow polymer particles can be prepared from carboxylated polymer particles by the stepwise
alkali/acid method. In this article, an attempt was made to prepare similar particles from acid-swellable polymer particles
by the stepwise treatment with acid and alkali, which was named the stepwise acid/alkali method. The acid-swellable particles
were produced by emulsion terpolymerization of styrene, butyl acrylate, and dimethyl 2-amino ethyl methacrylate. The effects
of initial pH value, temperature, and time in the acid and alkali treatment processes on the multi-hollow structure were examined.
Received: 18 December 1996 Accepted: 11 March 1997 相似文献
89.
The first examples of sequential photocycloaddition-rearrangement reactions of naphthalene-tethered resorcinol ethers are described. Bichromophoric aromatic compounds with naphthalene and resorcinol ether moieties were irradiated in the presence/absence of a small amount of acid to give the corresponding cycloaddition-rearrangement products. From the determination of quantum yields, steady-state fluorescence spectral studies, and fluorescence lifetime measurements, the mechanism of this novel photoinduced multistep reaction was elucidated to involve the initial intramolecular exciplex formation, followed by the intramolecular [2 + 2] photocycloaddition between the two aromatic rings and the subsequent acid-catalyzed skeletal rearrangement of the resulting cyclobutane derivative leading to the final products. 相似文献
90.
Cluster-size dependence of alloying behavior in nm-sized atom clusters has been studied by transmission electron microscopy, using clusters in the Au-Cu system. It was revealed that occurrence of rapid spontaneous alloying becomes more difficult with increasing cluster size. In gold clusters of approximately 4 nm in the mean size, a rapid dissolution of copper atoms took place and homogeneously mixed Au-Cu alloy clusters were formed. In gold clusters of approximately 10 nm in the mean size, rapid alloying of copper took place only at a shell-shaped region beneath the free surface of individual clusters and pure gold was retained at the central region of clusters. In gold clusters of approximately 30 nm in the mean size, no rapid alloying of copper was induced. The ease with which spontaneous alloying takes place is discussed in terms of the lattice softening in atom clusters. 相似文献