全文获取类型
收费全文 | 224440篇 |
免费 | 3156篇 |
国内免费 | 1340篇 |
专业分类
化学 | 125723篇 |
晶体学 | 3244篇 |
力学 | 8967篇 |
综合类 | 61篇 |
数学 | 24862篇 |
物理学 | 66079篇 |
出版年
2020年 | 1878篇 |
2019年 | 2001篇 |
2018年 | 2529篇 |
2017年 | 2580篇 |
2016年 | 3809篇 |
2015年 | 2580篇 |
2014年 | 3684篇 |
2013年 | 9113篇 |
2012年 | 7995篇 |
2011年 | 9742篇 |
2010年 | 6839篇 |
2009年 | 6622篇 |
2008年 | 9068篇 |
2007年 | 9149篇 |
2006年 | 8613篇 |
2005年 | 7870篇 |
2004年 | 7045篇 |
2003年 | 6188篇 |
2002年 | 6102篇 |
2001年 | 6733篇 |
2000年 | 5099篇 |
1999年 | 3697篇 |
1998年 | 3055篇 |
1997年 | 3036篇 |
1996年 | 3038篇 |
1995年 | 2641篇 |
1994年 | 2739篇 |
1993年 | 2597篇 |
1992年 | 2848篇 |
1991年 | 2908篇 |
1990年 | 2723篇 |
1989年 | 2637篇 |
1988年 | 2576篇 |
1987年 | 2516篇 |
1986年 | 2538篇 |
1985年 | 3324篇 |
1984年 | 3384篇 |
1983年 | 2824篇 |
1982年 | 3065篇 |
1981年 | 2835篇 |
1980年 | 2617篇 |
1979年 | 2800篇 |
1978年 | 3003篇 |
1977年 | 3042篇 |
1976年 | 3062篇 |
1975年 | 2800篇 |
1974年 | 2915篇 |
1973年 | 2967篇 |
1972年 | 2320篇 |
1971年 | 1847篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
Edgardo Becerra Giovanny Aguilera-Durn Laura Berumen Antonio Romo-Mancillas Guadalupe García-Alcocer 《Molecules (Basel, Switzerland)》2021,26(4)
Multidrug resistance protein-4 (MRP4) belongs to the ABC transporter superfamily and promotes the transport of xenobiotics including drugs. A non-synonymous single nucleotide polymorphisms (nsSNPs) in the ABCC4 gene can promote changes in the structure and function of MRP4. In this work, the interaction of certain endogen substrates, drug substrates, and inhibitors with wild type-MRP4 (WT-MRP4) and its variants G187W and Y556C were studied to determine differences in the intermolecular interactions and affinity related to SNPs using protein threading modeling, molecular docking, all-atom, coarse grained, and umbrella sampling molecular dynamics simulations (AA-MDS and CG-MDS, respectively). The results showed that the three MRP4 structures had significantly different conformations at given sites, leading to differences in the docking scores (DS) and binding sites of three different groups of molecules. Folic acid (FA) had the highest variation in DS on G187W concerning WT-MRP4. WT-MRP4, G187W, Y556C, and FA had different conformations through 25 ns AA-MD. Umbrella sampling simulations indicated that the Y556C-FA complex was the most stable one with or without ATP. In Y556C, the cyclic adenosine monophosphate (cAMP) and ceefourin-1 binding sites are located out of the entrance of the inner cavity, which suggests that both cAMP and ceefourin-1 may not be transported. The binding site for cAMP and ceefourin-1 is quite similar and the affinity (binding energy) of ceefourin-1 to WT-MRP4, G187W, and Y556C is greater than the affinity of cAMP, which may suggest that ceefourin-1 works as a competitive inhibitor. In conclusion, the nsSNPs G187W and Y556C lead to changes in protein conformation, which modifies the ligand binding site, DS, and binding energy. 相似文献
73.
74.
Natalia L. Calvo Sebastian O. SimonettiRubén M. Maggio Teodoro S. Kaufman 《Analytica chimica acta》2015
Exposure of cimetidine (CIM) to dry heat (160–180 °C) afforded, upon cooling, a glassy solid containing new and hitherto unknown products. The kinetics of this process was studied by a second order chemometrics-assisted multi-spectroscopic approach. Proton and carbon-13 nuclear magnetic resonance (NMR), as well as ultraviolet and infrared spectroscopic data were jointly used, whereas multivariate curve resolution with alternating least squares (MCR-ALS) was employed as the chemometrics method to extract process information. It was established that drug degradation follows a first order kinetics. 相似文献
75.
ABSTRACT A new density functional for the study of associating inhomogeneous fluids based on Wertheim's first-order thermodynamic perturbation theory is presented and compared to the most currently used associating density functionals. This functional is developed using the weighted density approximation in the range of association of hard spheres. We implement this functional within the framework of classical density functional theory together with modified fundamental measure theory to account for volume exclusion of hard spheres. This approach is tested against molecular simulations from literature of pure associating hard spheres and mixtures of non-associationg and associating hard spheres with different number of bonding sites close to a hard uniform wall. Furthermore, we compare and review our results with the performance of associating functionals from literature, one based on fundamental measure theory and the inhomogeneous version of Wertheim's perturbation theory. Results obtained with classical DFT and the three functionals show excellent agreement with molecular simulations in systems with one hard wall. For the cases of small pores where only one or two layers of fluid are allowed discrepancies between results with classical DFT and molecular simulations were found. 相似文献
76.
77.
78.
79.
Synthesis,Electronic Properties and WOLED Devices of Planar Phosphorus‐Containing Polycyclic Aromatic Hydrocarbons 下载免费PDF全文
Dr. François Riobé Rózsa Szűcs Dr. Pierre‐Antoine Bouit Dr. Denis Tondelier Bernard Geffroy Fátima Aparicio Julia Buendía Prof. Luis Sánchez Prof. Régis Réau Prof. László Nyulászi Prof. Muriel Hissler 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(17):6547-6556
We describe the synthesis and the physical properties of polyaromatic hydrocarbons (PAHs) containing a phosphorus atom at the edge. In particular, the impact of the successive addition of aromatic rings on the electronic properties was investigated by experimental (UV/Vis absorption, fluorescence, cyclic voltammetry) and theoretical studies (DFT). The physical properties recorded in solution and in the solid state showed that the P‐containing PAHs exhibit properties expected for an emitter in white organic light‐emitting diodes (WOLEDs). 相似文献
80.
Sh. M. Khaliullin V. D. Zhuravlev V. G. Bamburov L. V. Ermakova 《Physics of Atomic Nuclei》2015,78(12):1382-1388
Submicron CaZrO3 powder is obtained in combustion reactions (solution combustion synthesis—SCS) with glycine. It is found that SCS reduces the sintering temperature of CaZrO3 powders. The dielectric properties of calcium zirconate ceramics are studied by the electrochemical impedance method. It is shown that a ceramics of powders obtained by the SCS method has high dielectric characteristics. 相似文献