全文获取类型
收费全文 | 6885篇 |
免费 | 219篇 |
国内免费 | 55篇 |
专业分类
化学 | 4276篇 |
晶体学 | 52篇 |
力学 | 112篇 |
数学 | 1316篇 |
物理学 | 1403篇 |
出版年
2024年 | 6篇 |
2023年 | 25篇 |
2022年 | 136篇 |
2021年 | 180篇 |
2020年 | 129篇 |
2019年 | 193篇 |
2018年 | 206篇 |
2017年 | 177篇 |
2016年 | 257篇 |
2015年 | 216篇 |
2014年 | 218篇 |
2013年 | 482篇 |
2012年 | 432篇 |
2011年 | 539篇 |
2010年 | 377篇 |
2009年 | 308篇 |
2008年 | 442篇 |
2007年 | 412篇 |
2006年 | 367篇 |
2005年 | 356篇 |
2004年 | 307篇 |
2003年 | 245篇 |
2002年 | 199篇 |
2001年 | 89篇 |
2000年 | 87篇 |
1999年 | 100篇 |
1998年 | 77篇 |
1997年 | 55篇 |
1996年 | 86篇 |
1995年 | 50篇 |
1994年 | 46篇 |
1993年 | 52篇 |
1992年 | 42篇 |
1991年 | 30篇 |
1990年 | 14篇 |
1989年 | 20篇 |
1988年 | 11篇 |
1987年 | 10篇 |
1986年 | 13篇 |
1985年 | 15篇 |
1984年 | 13篇 |
1983年 | 18篇 |
1982年 | 14篇 |
1981年 | 13篇 |
1979年 | 9篇 |
1978年 | 11篇 |
1977年 | 12篇 |
1976年 | 6篇 |
1975年 | 11篇 |
1973年 | 5篇 |
排序方式: 共有7159条查询结果,搜索用时 15 毫秒
951.
Vladimir Martis Martin Martis John Lipp Dirk Detollenaere Trevor Rayment Gopinathan Sankar Wim Bras 《Journal of synchrotron radiation》2014,21(4):744-750
Energy‐resolved electron‐yield X‐ray absorption spectroscopy is a promising technique for probing the near‐surface structure of nanomaterials because of its ability to discriminate between the near‐surface and bulk of materials. So far, the technique has only been used in model systems. Here, the local structural characterization of nanoporous cobalt‐substituted aluminophosphates is reported and it is shown that the technique can be employed for the study of open‐framework catalytically active systems. Evidence that the cobalt ions on the surface of the crystals react differently to those in the bulk is found. 相似文献
952.
953.
Vladimir M. Uvarov Dimitry A. de Vekki 《Phosphorus, sulfur, and silicon and the related elements》2020,195(5):376-387
AbstractUsing a “chiral pool” approach, a number of chiral thiolate and sulfide ligands based on natural terpenes and terpenoids have been synthesized in a few simple steps. Two new Rh-thiolate complexes with the formula [Rh(CO)2(μ-SR)]2 were obtained. The influence of these complexes and catalytic systems formed by combining the synthesized ligands with [Rh(CO)2(μ-Cl)]2 and [Rh(cod)(μ-Cl)]2, on the reaction rate, chemoselectivity, stereoselectivity and formation of tetraphenyldisiloxane in Rh-catalyzed asymmetric hydrosilylation of acetophenone as a model reaction have been studied. Mechanistic aspects of formation of silyl enol ether as a side product in the presence of S-containing ligands are presented. 相似文献
954.
955.
956.
Journal of Russian Laser Research - We formulate the superposition principle of two states of qubit as a nonlinear addition rule of mean values of spin projections onto three perpendicular... 相似文献
957.
Vladimir I. Bakhmutov Aida Contreras-Ramirez Hannah Drake Hong-Cai Zhou 《Magnetic resonance in chemistry : MRC》2022,60(6):541-553
Solid-state NMR experiments on 2H, 31P, 13C, and 1H nuclei, including 31P T1, 1H T1, and 1H T1ρ measurements, as well as on the kinetics of proton-phosphorus cross-polarization have been performed to characterize the crystalline and amorphous α-zirconium phosphates, which were intercalated with D2O and/or CD3OD. The 13C{1H} CP MAS NMR experiment performed for compound 1-CD 3 OD (Zr (HPO4)2 . 0.2CD3OD) with carbon cross-polarization via protons of phosphate groups has provided a prove that the methanol was intercalated into the interlayer spaces of this compound. The variable-temperature 2H solid-echo MAS NMR spectra of intercalated compounds demonstrated that the methanol molecules, in contrast to the mobile water, were immobile, keeping, however, free CD3 rotations around the C3-axis. It has been demonstrated that the intercalated species, D2O and CD3OD, do not affect the high-frequency motions of the phosphate groups. By utilizing local structural models that satisfy the constraints of the experimental data, it has been suggested that the immobile methanol molecules are located in the cavity between two neighboring layers of the zirconium phosphates. Thus, the present work illustrates the reliable criteria in a comprehensive NMR approach to structural and dynamic studies of such systems. 相似文献
958.
959.
Zhu Wu Jrn Nitsch Julia Schuster Alexandra Friedrich Katharina Edkins Marcel Loebnitz Fabian Dinkelbach Vladimir Stepanenko Frank Würthner Christel M. Marian Lei Ji Todd B. Marder 《Angewandte Chemie (International ed. in English)》2020,59(39):17137-17144
Achieving highly efficient phosphorescence in purely organic luminophors at room temperature remains a major challenge due to slow intersystem crossing (ISC) rates in combination with effective non‐radiative processes in those systems. Most room temperature phosphorescent (RTP) organic materials have O‐ or N‐lone pairs leading to low lying (n, π*) and (π, π*) excited states which accelerate kisc through El‐Sayed's rule. Herein, we report the first persistent RTP with lifetimes up to 0.5 s from simple triarylboranes which have no lone pairs. RTP is only observed in the crystalline state and in highly doped PMMA films which are indicative of aggregation induced emission (AIE). Detailed crystal structure analysis suggested that intermolecular interactions are important for efficient RTP. Furthermore, photophysical studies of the isolated molecules in a frozen glass, in combination with DFT/MRCI calculations, show that (σ, B p)→(π, B p) transitions accelerate the ISC process. This work provides a new approach for the design of RTP materials without (n, π*) transitions. 相似文献
960.