全文获取类型
收费全文 | 188896篇 |
免费 | 6918篇 |
国内免费 | 4076篇 |
专业分类
化学 | 109632篇 |
晶体学 | 2764篇 |
力学 | 8382篇 |
综合类 | 244篇 |
数学 | 18615篇 |
物理学 | 60253篇 |
出版年
2022年 | 2013篇 |
2021年 | 2434篇 |
2020年 | 2685篇 |
2019年 | 2637篇 |
2018年 | 2824篇 |
2017年 | 2788篇 |
2016年 | 4271篇 |
2015年 | 3310篇 |
2014年 | 4450篇 |
2013年 | 8826篇 |
2012年 | 8367篇 |
2011年 | 9440篇 |
2010年 | 6503篇 |
2009年 | 6379篇 |
2008年 | 8213篇 |
2007年 | 7815篇 |
2006年 | 7575篇 |
2005年 | 6765篇 |
2004年 | 6011篇 |
2003年 | 5344篇 |
2002年 | 5122篇 |
2001年 | 6312篇 |
2000年 | 4674篇 |
1999年 | 3922篇 |
1998年 | 2847篇 |
1997年 | 2902篇 |
1996年 | 2833篇 |
1995年 | 2572篇 |
1994年 | 2517篇 |
1993年 | 2289篇 |
1992年 | 2709篇 |
1991年 | 2706篇 |
1990年 | 2517篇 |
1989年 | 2378篇 |
1988年 | 2322篇 |
1987年 | 2315篇 |
1986年 | 2076篇 |
1985年 | 2588篇 |
1984年 | 2577篇 |
1983年 | 2056篇 |
1982年 | 2047篇 |
1981年 | 1862篇 |
1980年 | 1831篇 |
1979年 | 2096篇 |
1978年 | 2159篇 |
1977年 | 2087篇 |
1976年 | 2035篇 |
1975年 | 1910篇 |
1974年 | 1879篇 |
1973年 | 1901篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
72.
73.
A new electroactive polynuclear inorganic compound of rare earth metal, gadolinium hexacyanoferrate (GdHCF), was prepared and characterized using the techniques of FTIR spectroscopy, thermogravimetric analysis (TG), UV-Vis spectrometry, X-ray photoelectron spectroscopy (XPS), ICP atomic emission spectroscopy, and EDX. The results of ICP atomic emission spectroscopy, EDX, and TGA indicated that the prepared GdHCF sample had a stoichiometry of NaGdFe(CN)6·12H2O (when GdHCF was prepared in NaCl solution). The FTIR spectrum of GdHCF showed that there were two types of water molecules in the structure of GdHCF: one was the interstitial water (5 H2O), which resulted from the association of water due to H-bonding, and the other was water coordinated with Gd (7 H2O). The results obtained using XPS showed that the oxidation state of Fe and Gd in the GdHCF sample was +2 and +3, respectively. GdHCF was immobilized on the surface of spectroscopically pure graphite (SG) electrode forming the GdHCF/SG electrode, and the solid-state electrochemistry of the resultant electrode was studied using cyclic voltammetry. The cyclic voltammetric results indicated that the GdHCF/SG electrode exhibited a pair of well-defined and stable redox peaks with the formal potential of E0′=(197±3) mV. The effects of the concentration of the supporting electrolyte on the electrochemical characteristics of GdHCF were studied, and the results showed that the value of E0′ increased linearly with the activity of the cationic ion of the supporting electrolyte (lgaNa+), with a slope of 54.1 mV, which may become a novel method for determining the activity of Na+ in solution. Further experimental results indicated that GdHCF had electrocatalytic activities toward the oxidation of dopamine (DA) and ascorbic acid (AA), and the electrocatalytic current increased linearly with the concentration of DA (or AA) in the range of 1.0–10.0 mmol·L?1 (for DA) or 0.5–20.0 mmol·L?1 (for AA). 相似文献
74.
75.
76.
77.
Zi‐Niu Wu 《国际流体数值方法杂志》2005,48(5):541-564
The widely used locally adaptive Cartesian grid methods involve a series of abruptly refined interfaces. In this paper we consider the influence of the refined interfaces on the steady state errors for second‐order three‐point difference approximations of flow equations. Since the various characteristic components of the Euler equations should behave similarly on such grids with regard to refinement‐induced errors, it is sufficient enough to conduct the analysis on a scalar model problem. The error we consider is a global error, different to local truncation error, and reflects the interaction between multiple interfaces. The steady state error will be compared to the errors on smooth refinement grids and on uniform grids. The conclusion seems to support the numerical findings of Yamaleev and Carpenter (J. Comput. Phys. 2002; 181: 280–316) that refinement does not necessarily reduce the numerical error. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
78.
79.
Effect of nickel coating on electrochemical performance of graphite anodes for lithium ion batteries
Among the different materials often studied and proposed as negative electrodes for lithium-ion batteries, graphite anodes
are the most used in commercial batteries. For this study, synthetic graphite was tested. During the first discharge 0.2 Li
ions were consumed for the formation of the SEI film and the capacity reaches about 387 mAh/g. But at the end of the first
charge only 72% of the initial charge was recovered (the reversible capacity is about 279 mAh/g). In order to improve this
performance we have deposited metallic nickel on graphite with the intention to obtain a homogeneous thin layer able to modify
the nature of the SEI film, to allow the diffusion of lithium ions through the protective layer, and also to increase the
performance of graphite electrodes. The results show a decrease of the irreversible capacity loss (16% instead of 28% for
pure graphite electrodes) as well as better cycleability for a nickel-deposited graphite electrode with only 11% weight ratio
of nickel. On the other hand, an increase of the nickel content decreases this performance. 相似文献
80.