全文获取类型
收费全文 | 1700篇 |
免费 | 65篇 |
国内免费 | 18篇 |
专业分类
化学 | 1084篇 |
晶体学 | 8篇 |
力学 | 32篇 |
数学 | 288篇 |
物理学 | 371篇 |
出版年
2023年 | 11篇 |
2022年 | 36篇 |
2021年 | 39篇 |
2020年 | 40篇 |
2019年 | 50篇 |
2018年 | 45篇 |
2017年 | 30篇 |
2016年 | 65篇 |
2015年 | 44篇 |
2014年 | 49篇 |
2013年 | 95篇 |
2012年 | 103篇 |
2011年 | 124篇 |
2010年 | 38篇 |
2009年 | 45篇 |
2008年 | 85篇 |
2007年 | 74篇 |
2006年 | 97篇 |
2005年 | 84篇 |
2004年 | 61篇 |
2003年 | 49篇 |
2002年 | 51篇 |
2001年 | 28篇 |
2000年 | 31篇 |
1999年 | 22篇 |
1998年 | 13篇 |
1997年 | 13篇 |
1996年 | 17篇 |
1995年 | 13篇 |
1994年 | 9篇 |
1993年 | 14篇 |
1992年 | 9篇 |
1991年 | 11篇 |
1990年 | 11篇 |
1989年 | 9篇 |
1988年 | 14篇 |
1987年 | 11篇 |
1986年 | 11篇 |
1985年 | 16篇 |
1984年 | 12篇 |
1983年 | 9篇 |
1982年 | 12篇 |
1981年 | 11篇 |
1980年 | 8篇 |
1979年 | 9篇 |
1978年 | 10篇 |
1977年 | 10篇 |
1976年 | 14篇 |
1975年 | 14篇 |
1973年 | 8篇 |
排序方式: 共有1783条查询结果,搜索用时 0 毫秒
1.
Chemistry of Heterocyclic Compounds - This microreview presents the current state of research on functionalization of α-mangostin, a natural hydroxyxanthone. Examples of transformations are... 相似文献
2.
Partially supported by the general research fund at the University of Kansas 相似文献
3.
We study the aggregation of oxygen dipoles well dispersed in a CaF2 crystal upon annealing at temperatures ranging from 370 to 420 K. The concentration of oxygen dipoles is monitored by measuring the intensity of the ionic thermocurrent peak as well as by absorption and luminescence spectroscopies. Results from three methods agree within experimental error and yield an activation energy of (1.2±0.1) eV for the diffusion of isolated oxygen centres in the crystal. 相似文献
4.
5.
6.
Capillary electrophoresis-mass spectrometry (CE-MS) with an electrospray ionization interface was applied for the quantitative analysis of imazamox pesticide in well water, potable water, and pond water. The detector response for imazamox was determined to be linear over the concentration range of 50-1 ng/ml. The limits of quantitation and detection of the method were determined to be 200 and 20 ng/l for imazamox compound in each type of water sample, respectively. The total sample preparation and CE-MS analysis time was under 2 h. 相似文献
7.
Alan D. Potoff Bertrand L. Chamberland Lewis Katz 《Journal of solid state chemistry》1973,8(3):234-237
A single crystal study of hydrothermally prepared eight-layer BaMnO3 has been carried out which confirms the (Zhdanov notation) 121121 layer stacking scheme for the BaO3 layers. The MnO6 octahedra share faces in strings of four, and these strings are connected to each other by corner sharing. The compound has an hexagonal unit cell of dimensions a = 5.667 ± 0.003 and c = 18.738 ± 0.009 Å, probable space group . Its structure has been determined from 352 independent reflections, of which 242 were considered observed, collected manually by a counter technique and refined to a conventional R value of 0.079. 相似文献
8.
Yellowish crystals of K2[(UO2)As2O7] ( 1 ) have been synthesized by solid‐state reactions method. The structure of 1 [orthorhombic, Pmmn, a = 12.601(2), b = 13.242(2), c = 5.621(1) Å, V = 937.9(3) Å3, Z = 4] has been solved by direct methods and refined to R1 = 0.049, wR2 = 0.1060 for 1059 observed reflections. The structure of 1 is based upon [(UO2)As2O7]2? sheets formed by corner sharing between [UO6]6? distorted octahedra and [As2O7]4? polyarsenate groups. The K+ cations are either in eightfold or tenfold coordination and are located between the sheets. The topology of the uranyl arsenate sheet is related to silicate minerals of the melilite group and related synthetic silicate, aluminate and germanate compounds. 相似文献
9.
Inorganic oxide core, polymer shell nanocomposite as a high K gate dielectric for flexible electronics applications 总被引:1,自引:0,他引:1
Maliakal A Katz H Cotts PM Subramoney S Mirau P 《Journal of the American Chemical Society》2005,127(42):14655-14662
Organic/inorganic core shell nanoparticles have been synthesized using high K TiO(2) as the core nanoparticle, and polystyrene as the shell. This material is easy to process and forms transparent continuous thin films, which exhibit a dielectric constant enhancement of over 3 times that of bulk polystyrene. This new dielectric material has been incorporated into capacitors and thin film transistors (TFTs). Mobilities approaching 0.2 cm(2)/V.s have been measured for pentacene TFTs incorporating the new TiO(2) polystyrene nanostructured gate dielectric, indicating good surface properties for pentacene film growth. This novel strategy for generating high K flexible gate dielectrics will be of value in improving organic and flexible electronic device performance. 相似文献
10.
Kudrik EV Theodoridis A van Eldik R Makarov SV 《Dalton transactions (Cambridge, England : 2003)》2005,(6):1117-1122
Catalytic oxidation of N,N'-dimethylthiourea and thiourea by dioxygen in water using a new cobalt(II) complex of octasulfophenyltetrapyrazinoporphyrazine was performed under mild conditions. The reaction is shown to include the formation of an intermediate anionic five-coordinate complex followed by an unusual two-electron oxidation to produce the corresponding urea and elemental sulfur (S8). Kinetic and thermodynamic parameters for the different reaction steps of the process were determined. Drastic differences in catalytic activity of cobalt and iron octasulfophenyltetrapyrazinoporphyrazines were observed. 相似文献