全文获取类型
收费全文 | 4310篇 |
免费 | 124篇 |
国内免费 | 20篇 |
专业分类
化学 | 2780篇 |
晶体学 | 39篇 |
力学 | 79篇 |
数学 | 843篇 |
物理学 | 713篇 |
出版年
2023年 | 40篇 |
2022年 | 59篇 |
2021年 | 125篇 |
2020年 | 98篇 |
2019年 | 122篇 |
2018年 | 132篇 |
2017年 | 111篇 |
2016年 | 151篇 |
2015年 | 121篇 |
2014年 | 125篇 |
2013年 | 271篇 |
2012年 | 236篇 |
2011年 | 302篇 |
2010年 | 192篇 |
2009年 | 194篇 |
2008年 | 243篇 |
2007年 | 228篇 |
2006年 | 225篇 |
2005年 | 211篇 |
2004年 | 174篇 |
2003年 | 137篇 |
2002年 | 113篇 |
2001年 | 71篇 |
2000年 | 53篇 |
1999年 | 38篇 |
1998年 | 38篇 |
1997年 | 33篇 |
1996年 | 26篇 |
1995年 | 22篇 |
1994年 | 25篇 |
1993年 | 32篇 |
1992年 | 17篇 |
1991年 | 31篇 |
1990年 | 17篇 |
1989年 | 14篇 |
1987年 | 15篇 |
1986年 | 20篇 |
1985年 | 22篇 |
1984年 | 30篇 |
1983年 | 20篇 |
1982年 | 20篇 |
1981年 | 27篇 |
1980年 | 22篇 |
1979年 | 25篇 |
1978年 | 26篇 |
1977年 | 27篇 |
1975年 | 20篇 |
1974年 | 15篇 |
1958年 | 13篇 |
1955年 | 15篇 |
排序方式: 共有4454条查询结果,搜索用时 62 毫秒
931.
Ihor Pavlov Andrey Rybak Andrii Dobrovolskiy Viktor Kadan Ivan Blonskiy Fatih Ö. Ilday 《Liquid crystals》2018,45(9):1265-1271
It is well known that the alignment of liquid crystals (LCs) can be realised by rubbing or photoalignment technologies. Recently, nonlinear laser lithography (NLL) was introduced as a fast, relatively low-cost method for large area nano-grating fabrication based on laser-induced periodic surface structuring. In this letter for the first time, the usage of the NLL as a perspective method of the alignment of nematics was presented. By NLL, nanogrooves with about 0.92 μm period were formed on Ti layer. The nanostructured Ti layer (NSTL) was coated with oxidianiline-polyimide film with annealing of the polymer followed without any further processing. Aligning properties of NSTLs were examined with combined twist LC cell. The dependencies of the twist angle of LC cells and azimuthal anchoring energy (AE) of layers on scanning speed and power of laser beam during processing of the Ti layer were the focus of our studies as well. The maximum azimuthal AE, obtained for pure NSTL, is comparable with photoalignment technology. It was found that the deposition of polyimide film on NSTL leads to the gain effect of the azimuthal AE. Also, atomic force microscopy (AFM) study of aligning surfaces was carried out. 相似文献
932.
Egorin Andrei Sokolnitskaya Tatiana Azarova Yuliya Portnyagin Arseniy Balanov Mikhail Misko Darya Shelestyuk Evgeny Kalashnikova Anastasia Tokar Eduard Tananaev Ivan Avramenko Valentin 《Journal of Radioanalytical and Nuclear Chemistry》2018,317(1):243-251
Sorption of micro- and microamounts of Sr from seawater has been studied using granulated Na-birnessite. Distribution coefficients of 90Sr in the natural seawater are 0.8–1.2?×?103 ml g?1, in the model seawater they are 1.6–1.8?×?103 ml g?1. Application of Na-birnessite was shown to be prospective in sorption–desorption–regeneration regime. In dynamic sorption conditions, over 150 bed volumes of seawater can be purified till 5% breakthrough occurs at feed rate 10 BV h?1. Na-birnessite can be used for 90Sr radionuclide removal from liquid radioactive wastes containing seawater.
相似文献933.
V. V. Matrenichev P. V. Popryadukhin A. E. Kryukov N. V. Smirnova E. M. Ivan’kova I. P. Dobrovol’skaya V. E. Yudin 《Polymer Science Series A》2018,60(2):215-221
The investigation of the dependence of effective viscosity on shear rate for a water-alcohol solution of an aliphatic copolyamide and its mixtures with single-wall carbon nanotubes reveals that additives of the nanoparticles in the amount of 0.5 wt % lead to a substantial reduction in the effective viscosity as the shear rate rises. The measurement of the surface tension and electrical conductivity of the solutions bearing 0.1–2.0 wt % of the nanotubes allows one to choose an optimal mode for electrospinning of the composite nanofibers based on the aliphatic copolyamide. The introduction of carbon nanofibers reduces the specific resistance of the material to 8.9 × 109 Ω m, but increases the elastic modulus. The lack of cytotoxicity of the resulting materials and the high proliferative activity of human dermal fibroblasts on their surface allow one to use the film materials based on the composite nanofibers in cell technologies and as matrices for tissue engineering. 相似文献
934.
935.
Ilija N. Cvijetić Miloš P. Pešić Miljana D. Todorov Branko J. Drakulić Ivan O. Juranić Tatjana Ž. Verbić Mire Zloh 《Structural chemistry》2018,29(2):423-434
Aryldiketo acids (ADKs) exhibit the variety of biological activities, mainly due to large affinity toward divalent metal ions. Metal complexation ability of ADKs, as well as interactions with proteins, depend on tautomeric form present in solution. The main aim of this study was to fully explore the tautomeric preferences of 4-phenyl-2,4-dioxobutanoic acid (4PDA), as ADKs representative, in aqueous media at different pH values. 1D and 2D NMR spectroscopy in combination with quantum chemical calculations was applied in order to better understand the tautomeric preferences of 4PDA. The data in highly acidic media are especially interesting since there are no such findings in the literature due to low solubility of ADKs in molecular form. At low pH values, where 4PDA is unionized, the most abundant tautomeric form is enol with keto group closer to phenyl ring. At higher pH values, mixture of two 4PDA ionic forms coexists in solution. Their ratio calculated according to NMR data fits the values predicted using two experimentally determined pK a values. Based on the complexity of 1H NMR spectrum of monoanionic 4PDA form, coexistence of two stable rotamers was assumed. In an alkaline media, 4PDA is mostly present in dianionic form. As π-electrons of dianion are delocalized over an entire keto-enol moiety, spectral distinction between tautomers was not possible. Quantum chemical calculations were used to predict relative stability of tautomers. The predictions were in good accordance with experimental results only in case when explicit water molecule was included in calculations. 相似文献
936.
937.
Dr. Quan Pang Xiao Liang Ivan R. Kochetkov Dr. Pascal Hartmann Prof. Dr. Linda F. Nazar 《Angewandte Chemie (International ed. in English)》2018,57(31):9795-9798
The dendritic growth of Li metal leads to electrode degradation and safety concerns, impeding its application in building high energy density batteries. Forming a protective layer on the Li surface that is electron‐insulating, ion‐conducting, and maintains an intimate interface is critical. We herein demonstrate that Li plating is stabilized by a biphasic surface layer composed of a lithium‐indium alloy and a lithium halide, formed in situ by the reaction of an electrolyte additive with Li metal. This stabilization is attributed to the fast lithium migration though the alloy bulk and lithium halide surface, which is enabled by the electric field across the layer that is established owing to the electron‐insulating halide phase. A greatly stabilized Li‐electrolyte interface and dendrite‐free plating over 400 hours in Li|Li symmetric cells using an alkyl carbonate electrolyte is demonstrated. High energy efficiency operation of the Li4Ti5O12 (LTO)|Li cell over 1000 cycles is achieved. 相似文献
938.
Dr. Subrata Saha Dr. Brice Kauffmann Dr. Yann Ferrand Dr. Ivan Huc 《Angewandte Chemie (International ed. in English)》2018,57(41):13542-13546
Xylobiose sequestration in a helical aromatic oligoamide capsule was evidenced by circular dichroism, NMR spectroscopy, and crystallography. The preparation of the 5 kDa oligoamide sequence was made possible by the transient use of acid‐labile dimethoxybenzyl tertiary amide substituents that disrupt helical folding and prevent double helix formation. Binding of other disaccharides was not detected. Crystallographic data revealed a complex composed of a d ‐xylobiose α anomer and two water molecules accommodated in the right‐handed helix. The disaccharide was found to adopt an unusual all‐axial compact conformation. A dense network of 18 hydrogen bonds forms between the guest, the cavity wall, and the two water molecules. 相似文献
939.
940.
Ledeti Ionut Pusztai Agneta Maria Murariu Marius Olariu Sorin Ivan Codrut Circioban Denisa Vlase Gabriela Ledeti Adriana Vlase Titus Matusz Petru 《Journal of Thermal Analysis and Calorimetry》2018,131(2):1345-1360
Journal of Thermal Analysis and Calorimetry - In this work, solifenacin succinate (SOLS), flavoxate HCl (FLXHC) and tolterodine tartrate (TOLT) drugs were investigated using thermal analysis (TA)... 相似文献