全文获取类型
收费全文 | 5874篇 |
免费 | 208篇 |
国内免费 | 45篇 |
专业分类
化学 | 4147篇 |
晶体学 | 35篇 |
力学 | 139篇 |
数学 | 1071篇 |
物理学 | 735篇 |
出版年
2024年 | 10篇 |
2023年 | 45篇 |
2022年 | 134篇 |
2021年 | 171篇 |
2020年 | 105篇 |
2019年 | 132篇 |
2018年 | 106篇 |
2017年 | 83篇 |
2016年 | 196篇 |
2015年 | 177篇 |
2014年 | 207篇 |
2013年 | 354篇 |
2012年 | 402篇 |
2011年 | 448篇 |
2010年 | 290篇 |
2009年 | 289篇 |
2008年 | 363篇 |
2007年 | 376篇 |
2006年 | 354篇 |
2005年 | 337篇 |
2004年 | 251篇 |
2003年 | 182篇 |
2002年 | 189篇 |
2001年 | 79篇 |
2000年 | 63篇 |
1999年 | 57篇 |
1998年 | 43篇 |
1997年 | 46篇 |
1996年 | 75篇 |
1995年 | 40篇 |
1994年 | 38篇 |
1993年 | 37篇 |
1992年 | 45篇 |
1991年 | 33篇 |
1990年 | 20篇 |
1989年 | 28篇 |
1988年 | 22篇 |
1987年 | 21篇 |
1986年 | 25篇 |
1985年 | 44篇 |
1984年 | 30篇 |
1983年 | 22篇 |
1982年 | 29篇 |
1981年 | 18篇 |
1980年 | 20篇 |
1979年 | 15篇 |
1978年 | 11篇 |
1977年 | 7篇 |
1975年 | 8篇 |
1974年 | 7篇 |
排序方式: 共有6127条查询结果,搜索用时 15 毫秒
891.
In the study of the conformational behavior of complex systems, such as proteins, several related statistical measures are commonly used to compare two different potential energy functions. Among them, the Pearson's correlation coefficient r has no units and allows only semiquantitative statements to be made. Those that do have units of energy and whose value may be compared to a physically relevant scale, such as the root-mean-square deviation (RMSD), the mean error of the energies (ER), the standard deviation of the error (SDER) or the mean absolute error (AER), overestimate the distance between potentials. Moreover, their precise statistical meaning is far from clear. In this article, a new measure of the distance between potential energy functions is defined that overcomes the aforementioned difficulties. In addition, its precise physical meaning is discussed, the important issue of its additivity is investigated, and some possible applications are proposed. Finally, two of these applications are illustrated with practical examples: the study of the van der Waals energy, as implemented in CHARMM, in the Trp-Cage protein (PDB code 1L2Y) and the comparison of different levels of the theory in the ab initio study of the Ramachandran map of the model peptide HCO-L-Ala-NH2. 相似文献
892.
Niranjan D. Parab Cang Zhao Ross Cunningham Luis I. Escano Kamel Fezzaa Wes Everhart Anthony D. Rollett Lianyi Chen Tao Sun 《Journal of synchrotron radiation》2018,25(5):1467-1477
The high‐speed synchrotron X‐ray imaging technique was synchronized with a custom‐built laser‐melting setup to capture the dynamics of laser powder‐bed fusion processes in situ. Various significant phenomena, including vapor‐depression and melt‐pool dynamics and powder‐spatter ejection, were captured with high spatial and temporal resolution. Imaging frame rates of up to 10 MHz were used to capture the rapid changes in these highly dynamic phenomena. At the same time, relatively slow frame rates were employed to capture large‐scale changes during the process. This experimental platform will be vital in the further understanding of laser additive manufacturing processes and will be particularly helpful in guiding efforts to reduce or eliminate microstructural defects in additively manufactured parts. 相似文献
893.
894.
Samuel García-Arellano Luis Alexis Hernndez-Palma Sergio Cerpa-Cruz Gabriela Athziri Snchez-Zuno Melva Guadalupe Herrera-Godina Jos Francisco Muoz-Valle 《Molecules (Basel, Switzerland)》2021,26(16)
Rheumatoid arthritis (RA) is an autoimmune inflammatory joint disease with complex pathogenesis associated with cytokine dysregulation. Macrophage migration inhibitory factor (MIF) plays a role in systemic inflammation and joint destruction in RA and could be associated with the secretion of other immune-modulatory cytokines such as IL-25, IL-31, and IL-33. For the above, our main aim was to evaluate the IL-25, IL-31, and IL-33 secretion from recombinant human MIF (rhMIF)-stimulated peripheral blood mononuclear cells (PBMC) of RA patients. The rhMIF and lipopolysaccharide (LPS) plus rhMIF stimuli promote the secretion of IL-25, IL-31, and IL-33 (p < 0.05) from PBMC of RA patients. The study groups, the different stimuli, and the interaction between both showed a statistically significant effect on the secretion of IL-25 (p < 0.05) and IL-31 (p < 0.01). The study of the effect of the RA patient treatments and their interaction with the effect of stimuli did not show an interaction between them. In conclusion, our study generates new evidence for the role of MIF in the secretion of IL-25, IL-31, and IL-33 and its immunomodulatory effect on RA. 相似文献
895.
896.
897.
Bernardo?Nu?ez-MoraledaEmail author Joaquin?Pizarro Elisa?Guerrero Maria?P.?Guerrero-Lebrero Andres?Yá?ez Sergio?Ignacio?Molina Pedro?Luis?Galindo 《The European Physical Journal B - Condensed Matter and Complex Systems》2014,87(11):263
In this paper, stress fields at the surface of the capping layer of self-assembled InAsP quantum wires grown on an InP (001) substrate have been determined from atomistic models using molecular dynamics and Stillinger-Weber potentials. To carry out these calculations, the quantum wire compositional distribution was extracted from previous works, where the As and P distributions were determined by electron energy loss spectroscopy and high-resolution aberration-corrected Z-contrast imaging. Preferential sites for the nucleation of wires on the surface of the capping layer were studied and compared with (i) previous simulations using finite element analysis to solve anisotropic elastic theory equations and (ii) experimentally measured locations of stacked wires. Preferential nucleation sites of stacked wires were determined by the maximum stress location at the MD model surface in good agreement with experimental results and those derived from finite element analysis. This indicates that MD simulations based on empirical potentials provide a suitable and flexible tool to study strain dependent atom processes. 相似文献
898.
Yoshiki Nishi Yuta Ueno Masachika Nishio Luis Antonio Rodrigues Quadrante Kentaroh Kokubun 《Journal of sound and vibration》2014
We conducted an experiment in a towing tank to investigate the performance of an energy extraction system using the flow-induced vibration of a circular cylinder. This experiment tested three different cases involving the following arrangements of cylinder(s) of identical diameter: the upstream fixed–downstream movable arrangement (case F); the upstream movable–downstream fixed arrangement (case R); and a movable isolated cylinder (case I). In cases F and R, the separation distance (ratio of the distance between the centers of the two cylinders to their diameters) is fixed at 1.30. Measurement results show that while cases F and I generate vortex-induced vibration (VIV) resonance responses, case R yields wake-induced vibration (WIV) at reduced velocity over 9.0, which is significantly larger than that of the VIV response, leading to the induction of higher electronic power in a generator. Accordingly, primary energy conversion efficiency is higher in the case involving WIV. 相似文献
899.
José Martínez-Casas Egidio Di Gialleonardo Stefano Bruni Luis Baeza 《Journal of sound and vibration》2014
Train–track interaction has been extensively studied in the last 40 years at least, leading to modelling approaches that can deal satisfactorily with many dynamic problems arising at the wheel/rail interface. However, the available models are usually not considering specifically the running dynamics of the vehicle in a curve, whereas a number of train–track interaction phenomena are specific to curve negotiation. 相似文献
900.