全文获取类型
收费全文 | 10678篇 |
免费 | 553篇 |
国内免费 | 80篇 |
专业分类
化学 | 7978篇 |
晶体学 | 86篇 |
力学 | 190篇 |
数学 | 1066篇 |
物理学 | 1991篇 |
出版年
2023年 | 64篇 |
2022年 | 160篇 |
2021年 | 209篇 |
2020年 | 167篇 |
2019年 | 186篇 |
2018年 | 162篇 |
2017年 | 148篇 |
2016年 | 342篇 |
2015年 | 304篇 |
2014年 | 375篇 |
2013年 | 648篇 |
2012年 | 741篇 |
2011年 | 883篇 |
2010年 | 522篇 |
2009年 | 458篇 |
2008年 | 701篇 |
2007年 | 594篇 |
2006年 | 624篇 |
2005年 | 519篇 |
2004年 | 464篇 |
2003年 | 392篇 |
2002年 | 410篇 |
2001年 | 204篇 |
2000年 | 200篇 |
1999年 | 131篇 |
1998年 | 91篇 |
1997年 | 104篇 |
1996年 | 110篇 |
1995年 | 82篇 |
1994年 | 78篇 |
1993年 | 64篇 |
1992年 | 72篇 |
1991年 | 50篇 |
1990年 | 69篇 |
1989年 | 73篇 |
1988年 | 50篇 |
1987年 | 42篇 |
1986年 | 34篇 |
1985年 | 69篇 |
1984年 | 60篇 |
1983年 | 43篇 |
1982年 | 46篇 |
1981年 | 38篇 |
1980年 | 34篇 |
1979年 | 40篇 |
1978年 | 34篇 |
1977年 | 44篇 |
1976年 | 34篇 |
1975年 | 31篇 |
1973年 | 39篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
941.
Thuy-Duong Nguyen-Phan Myoung Bok Song Eui Jung Kim Eun Woo Shin 《Research on Chemical Intermediates》2010,36(6-7):613-619
One-dimensional titania nanomaterials were synthesized by soft chemical processes in an alkali medium. The effect of alkali-treatment temperature on the morphology, porosity, and crystalline phase of TiO2 nanomaterials was investigated. Nanotubes having an opening end were observed when aging the sample at 130 °C, while conducting the process at 180 °C resulted in nanoribbons with a high aspect ratio. Post-treatment at 300 °C led to the partial transformation from tubular structures into nanoparticles or ribbons into nanobelts. While the monoclinic sodium hexatitanate and anatase crystal had a tubular structure, nanoribbons and nanobelt TiO2 also showed the presence of hydrogen titanate and sodium trititanate. High surface areas were achieved in as-prepared nanotubes and nanoribbons, 456.5 and 72.1 m2/g, respectively, and a drastic reduction was obtained upon post-treatment at 300 °C to 72.1 and 19.2 m2/g, respectively. 相似文献
942.
K. J. Chen F. Y. Hung S. J. Chang S. J. Young Z. S. Hu S. P. Chang 《Journal of Sol-Gel Science and Technology》2010,54(3):347-354
The multi-compound ZITO transparent conductive oxide (TCO) thin films were synthesized using the sol–gel method. The ZITO
thin films with various volume ratios of ZnO to ITO (1:1, 2:1 and 9:1) were crystallized at different temperatures (600–700 °C).
The results showed that the crystalline characteristics and optical transmittance were mainly dependent on ITO content and
crystallization. Notably, the 650 °C Z9ITO film not only had better conductivity but also possessed excellent optical transmittance. In addition, the surface roughness
of the ZITO films and optoelectric properties of IZO (indium doped ZnO) films were analyzed to confirm the contribution of
indium dopants on the optical transmittance. Also, the ZITO films were subjected to the effects of indium and tin dopants
and this improved the related characteristics of ZnO films. 相似文献
943.
Sun Hwa Lee Li Xu Dr. Byeong Kwon Park Yuri V. Mironov Dr. Soo Hyun Kim Young Ju Song Cheal Kim Prof. Dr. Youngmee Kim Dr. Sung‐Jin Kim Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(15):4678-4685
Two new tetranuclear chalcocyanide cluster complexes, [{Mn(saloph)H2O}4Re4Q4(CN)12]?4 CH3OH? 8 H2O (saloph=N,N′‐o‐phenylenebis(salicylidenaminato), Q=Se ( 1 ‐Se), Te ( 2 ‐Te)), have been synthesized by the diffusion of a methanolic solution of [PPh4]4[Re4Q4(CN)12] into a methanolic solution of [Mn(saloph)]+. The structure of 2 ‐Te has been determined by X‐ray crystallography. These rhenium cluster‐supported [MnIII(saloph)] complexes have been found to efficiently catalyze a wide range of olefin epoxidations under mild experimental conditions in the presence of meta‐chloroperbenzoic acid (mCPBA). Olefin epoxidation by these catalysts is proposed to involve the multiple active oxidants MnV?O, MnIV?O, and MnIII? OOC(O)R. Evidence in support of this interpretation has been derived from reactivity and Hammett studies, H218O‐exchange experiments, and the use of peroxyphenylacetic acid as a mechanistic probe. Moreover, it has been observed that the participation of MnV?O, MnIV?O, and MnIII? OOC(O)R can be controlled by changing the substrate concentration. This mechanism provides the greatest congruity with related oxidation reactions that employ certain Mn complexes as catalysts. 相似文献
944.
Satish Balasaheb Nimse Junghoon Kim Keum-Soo Song Chan-Yong Jung Sudhakara Reddy Seelam 《Tetrahedron letters》2010,51(21):2840-551
We report the new water-soluble aminocalix[4]arene hosts 1 and 2 with deep hydrophobic cavity facilitating hydrophobic mouth and hydrophilic mouth, respectively. The 1H NMR titrations revealed that host 1 shows high selectivity for neutral guests 9 and 10, with log K of 4.2 and 4.6, respectively. The host 2 shows log K of 4.9 for binding with guest 15. Moreover, the binding ability of the host 2 for guest 14 is stronger by a factor of 1000 than that of the host 1. 相似文献
945.
A novel tandem one-pot method for the synthesis of α-aminomethylene-γ-butyrolactone derivatives has been developed through the regioselective epoxide opening reactions with the Blaise reaction intermediates, generated by the reaction of a Reformatsky reagent with nitriles. Formation of a modified Blaise reaction intermediate by the addition of a stoichiometric amount of n-BuLi followed by slow addition of epoxide is required for the good yield of γ-butyrolactones. 相似文献
946.
Sook Kyung Kim K.M.K. Swamy So-Young Chung Min Jung Kim Juyoung Yoon 《Tetrahedron letters》2010,51(25):3286-1197
Novel rhodamine B (RB) derivatives bearing mono and bis-boronic acid groups were investigated as Hg2+ selective fluorescent and colorimetric sensors. These derivatives are first examples of reversible fluorescent chemosensors for Hg2+ which utilized boronic acid groups as binding sites. Two new RB-boronic acid derivatives displayed selective ‘Off-On’-type fluorescent enhancements and distinct color changes with Hg2+. Selective fluorescent enhancement of two rhodamine derivatives was attributed to ring opening from the spirolactam (nonfluorescent) to ring-opened amide (fluorescent). 相似文献
947.
Anionic tetrahydrofuran clusters (THF)(n) (-) (1≤n≤100) are studied with photoelectron imaging as gas-phase precursors for electrons solvated in THF. Photoelectron spectra of clusters up to n=5 show two peaks, one of which is attributed to a solvated open chain radical anion and the other to the closed THF ring. At n=6, the spectra change shape abruptly, which become more characteristic of (THF)(n) (-) clusters containing solvated electrons. From n=6-100, the vertical detachment energies (VDEs) of these solvated electron clusters increase from 1.96 to 2.71 eV, scaling linearly with n(-1/3). For fully deuterated (THF-d8)(n) (-) clusters, the apparent transition to a solvated electron cluster is delayed to n=11. Extrapolation of the VDEs to infinite cluster size yields a value of 3.10 eV for the bulk photoelectric threshold. The relatively large VDEs at onset and small stabilization with increasing cluster size compared to other solvated electron clusters may reflect the tendency of the bulk solvent to form preexisting voids that can readily solvate a free electron. 相似文献
948.
949.
950.