全文获取类型
收费全文 | 9550篇 |
免费 | 1444篇 |
国内免费 | 1174篇 |
专业分类
化学 | 6957篇 |
晶体学 | 91篇 |
力学 | 423篇 |
综合类 | 112篇 |
数学 | 1065篇 |
物理学 | 3520篇 |
出版年
2024年 | 20篇 |
2023年 | 223篇 |
2022年 | 290篇 |
2021年 | 341篇 |
2020年 | 449篇 |
2019年 | 426篇 |
2018年 | 332篇 |
2017年 | 338篇 |
2016年 | 453篇 |
2015年 | 448篇 |
2014年 | 551篇 |
2013年 | 656篇 |
2012年 | 868篇 |
2011年 | 844篇 |
2010年 | 545篇 |
2009年 | 504篇 |
2008年 | 628篇 |
2007年 | 600篇 |
2006年 | 491篇 |
2005年 | 437篇 |
2004年 | 299篇 |
2003年 | 250篇 |
2002年 | 235篇 |
2001年 | 216篇 |
2000年 | 223篇 |
1999年 | 187篇 |
1998年 | 175篇 |
1997年 | 146篇 |
1996年 | 164篇 |
1995年 | 151篇 |
1994年 | 108篇 |
1993年 | 100篇 |
1992年 | 82篇 |
1991年 | 63篇 |
1990年 | 67篇 |
1989年 | 40篇 |
1988年 | 40篇 |
1987年 | 32篇 |
1986年 | 27篇 |
1985年 | 35篇 |
1984年 | 15篇 |
1983年 | 16篇 |
1982年 | 15篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1957年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
991.
Bo Ding Wei‐Wei Ma Yi Dai Hao Gao Yang Yu Ye Tao Yi Zhong Xin‐Sheng Yao 《Helvetica chimica acta》2010,93(12):2488-2494
Two new iridoids, 10‐O‐benzoyl‐6′‐O‐α‐L ‐arabino(1→6)‐β‐D ‐glucopyranosylgeniposidic acid ( 1 ), deacetyl‐6‐ethoxyasperulosidic acid methyl ester ( 2 ), along with 14 other known iridoids, were isolated from the whole plant of Hedyotis diffusa Willd. Their structures were determined on the basis of spectroscopic analysis. The short‐term‐memory‐enhancement activities of compounds 1, 7 – 9, 11 , and 13 were evaluated on an Aβ transgenic drosophila model. 相似文献
992.
993.
K. B. Yemel’yanov A. Ye. Bychkov V. L. Zelenko L. I. Heifets 《Moscow University Chemistry Bulletin》2010,65(2):75-79
The article suggests a mathematical model for the process of anodic intercalation of the dense graphite suspension in dilute
nitric acid, where the spontaneous intercalation is absent. The model is based on the idea of electric neutrality of a graphite
particle, due to which the anion current NO3− entering the particle is precisely equal to the quantity of electrons, which are diverted from a particle to a current lead
according to the mechanism of electronic conductivity provided by the outer constriction of the suspension. The anodic polarization
is conditioned by the mass transfer of anions NO3− inside the equipotential graphite particle. The computational solution of the problem showed that even at a small suspension
layer height (2 cm), there is a significant nonuniformity of intercalation, which corresponds to the data provided in the
literature. A method for the estimation of an intercalation nonuniformity and a method for its reduction by using a multistep
process were suggested. The results of the computation can be used for an estimation of the technical characteristics of the
final product. 相似文献
994.
995.
The Cu(I)-catalyzed cascade coupling/cyclization reaction of N-tosylhydrazones with 3-butyn-1-ol has been explored. This new strategy represents a simple platform for the synthesis of tetrahydrofurans in moderate to good yields. 相似文献
996.
Dr. Hong Li Ye Liu Xin Cao Dr. Lu Han Prof. Dr. Chun Jiang Prof. Dr. Shunai Che 《Angewandte Chemie (International ed. in English)》2017,56(3):806-811
Photonic crystals are expected to be metamaterials because of their potential to control the propagation of light in the linear and nonlinear regimes. Biological single-network, triply periodic constant mean curvature surface structures are considered excellent candidates owing to their large complete band gap. However, the chemical construction of these relevant structures is rare and developing new structures from thermodynamically stable double-network self-organizing systems is challenging. Herein, we reveal that the shifted double-diamond titania scaffold can achieve a complete band gap. The largest (7.71 %) band gap is theoretically obtained by shifting 0.332 c with the dielectric contrast of titania (6.25). A titania scaffold with similar shifted double-diamond structure was fabricated using a reverse core–shell microphase-templating system with an amphiphilic diblock copolymer and a titania source in a mixture of tetrahydrofuran and water, which could result in a 2.05–3.78 % gap. 相似文献
997.
998.
Ying Lin Teng‐Ling Ye Yu Chen Dong‐Ge Ma Zhi‐Kuan Chen Yan‐Feng Dai Yong‐Xi Li 《Journal of polymer science. Part A, Polymer chemistry》2010,48(24):5930-5937
A new bipolar conjugated polyfluorene copolymer with triphenylamine and cyanophenylfluorene as side chains, poly{[9,9‐di(triphenylamine)fluorene]‐[9,9‐dihexyl‐fluorene]‐[2,7‐bis(4′‐cyanophenyl)‐9,9′‐spirobifluorene]} ( PTHCF ), was synthesized for studying the polymer backbone emission. Its absolute weight‐average molecular weight was determined as 4.85 × 104 by using gel permeation chromatography with a multiangle light scattering detector. In contrast to the electronic absorption spectrum in dilute solution, the absorbance of PTHCF in thin film was slightly blue shifted. By comparison of the solution and thin‐film photoluminescence (PL) spectra, a red shift of Δλ = 8–9 nm was observed in the thin‐film PL spectrum. The HOMO and LUMO energy levels of the resulting polymer were electrochemically estimated as ?5.68 and ?2.80 eV, respectively. Under the electric‐field intensity of 4.8 × 105 V cm?1, the obtained hole and electron mobilities were 2.41 × 10?4 and 1.40 × 10?4 cm2 V?1 s?1, respectively. An electroluminescence device with configuration of ITO/PEDOT:PSS/ PTHCF 70%+PBD30%/CsF/Ca/Al exhibited a deep‐blue emission as a result of excitons formed by the charges migrating along the full‐fluorene main chain. The incorporation of the bipolar side chains into the polymer structure prevented the intermolecular interaction of the fluorene moieties, balance charge injection/transport, and thereby improve the polymer backbone emission. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献
999.
Enantioselective addition of diethylzinc to a series of aromatic aldehydes was developed using a modular amino acid amide chiral ligand (2S)‐3‐phenyl‐N‐((R)‐1‐phenyl‐ethyl)‐2‐(tosylamino)propanamide without using titanium complex. The catalytic system employing 10 mol% of 1g was found to promote the addition of diethylzinc (ZnEt2) to a wide range of aromatic aldehydes with electron‐donating and electron‐withdrawing substituents, giving up to 82% ee of the corresponding secondary alcohol under mild conditions. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
1000.
Zicong Jian Yuying Pu Jianzhang Fang Zhiping Ye 《Photochemistry and photobiology》2010,86(5):1016-1021
Microemulsion is the easiest and cleanest of the popular methods of synthesizing nanomaterial. This work synthesized the nanosized La-TiO2 and Ce-TiO2 particles through the hydrolyzation of tetrabutyl titanate in a Triton X-100/n-hexanol/cyclohexane/water reverse microemulsion. The particles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform-infrared spectroscopy (FT-IR) and thermogravimetry (TG). The photocatalytic activity was evaluated by photocatalytic degradation of methyl orange (MO) under ultraviolet light and visible light irradiation. The results showed that reverse microemulsion produced the nanosized and well-separated particles, which are obviously in degrading MO. Comparing the pure TiO2 with doping TiO2, the doping ones are smaller and have better photocatalytic activity, which was best at the molar content of 0.1% for La, whereas for Ce it was 0.5%. 相似文献