全文获取类型
收费全文 | 7053篇 |
免费 | 1127篇 |
国内免费 | 719篇 |
专业分类
化学 | 4687篇 |
晶体学 | 72篇 |
力学 | 414篇 |
综合类 | 41篇 |
数学 | 641篇 |
物理学 | 3044篇 |
出版年
2024年 | 27篇 |
2023年 | 149篇 |
2022年 | 201篇 |
2021年 | 203篇 |
2020年 | 262篇 |
2019年 | 221篇 |
2018年 | 207篇 |
2017年 | 190篇 |
2016年 | 301篇 |
2015年 | 300篇 |
2014年 | 370篇 |
2013年 | 512篇 |
2012年 | 547篇 |
2011年 | 589篇 |
2010年 | 396篇 |
2009年 | 403篇 |
2008年 | 426篇 |
2007年 | 363篇 |
2006年 | 355篇 |
2005年 | 330篇 |
2004年 | 274篇 |
2003年 | 201篇 |
2002年 | 222篇 |
2001年 | 173篇 |
2000年 | 169篇 |
1999年 | 175篇 |
1998年 | 128篇 |
1997年 | 128篇 |
1996年 | 151篇 |
1995年 | 107篇 |
1994年 | 113篇 |
1993年 | 108篇 |
1992年 | 100篇 |
1991年 | 82篇 |
1990年 | 63篇 |
1989年 | 74篇 |
1988年 | 52篇 |
1987年 | 47篇 |
1986年 | 38篇 |
1985年 | 34篇 |
1984年 | 19篇 |
1983年 | 18篇 |
1982年 | 14篇 |
1981年 | 13篇 |
1980年 | 9篇 |
1979年 | 6篇 |
1976年 | 4篇 |
1973年 | 3篇 |
1970年 | 3篇 |
1957年 | 3篇 |
排序方式: 共有8899条查询结果,搜索用时 0 毫秒
991.
D. Raghavan X. Gu T. Nguyen M. Vanlandingham 《Journal of Polymer Science.Polymer Physics》2001,39(13):1460-1470
Characterization of polymer coatings microstructure is critical to the fundamental understanding of the corrosion of coated metals. An approach for mapping the chemical heterogeneity of a polymer system using chemical modification and tapping‐mode atomic force microscopy (TMAFM) is demonstrated. This approach is based on the selective degradation of one of the phases in a multiphase polymer blend system and the ability of TMAFM to provide nanoscale lateral information about the different phases in the polymer system. Films made of a 70:30 polyethyl acrylate/polystyrene (PEA/PS) blend were exposed to a hydrolytic acidic environment and analyzed using TMAFM. Pits were observed to form in the PEA/PS blend films, and this degradation behavior was similar to that of the PEA material. Using these results, the domains in the 70:30 blend were identified as the PS‐rich regions and the matrix as the PEA‐rich region. This conclusion was confirmed by Fourier transform infrared‐attenuated total reflection analyses that revealed the hydrolysis of the PEA material. TMAFM phase imaging was also used to follow pit growth of the blend as a function of exposure time. The usefulness of the chemical modification/AFM imaging approach in understanding the degradation process of a coating film is discussed. © 2001 John Wiley & Sons, Inc. J Polym Sci B Part B: Polym Phys 39: 1460–1470, 2001 相似文献
992.
Let F be a family of mermorphic functions in a domain D, and let a, b, c be complex numbers, a ≠ b. If for each f ∈ F, the zeros of f-c are of multiplicity ≥ k + 1, and -↑Ef(k)(a) belong to -↑Ef (a), -↑Ef(k)(b)belong to -↑Ef (b), then F is normal in D. 相似文献
993.
In this study, one kind of lithium aluminosilicate-β-quartz glass-ceramic containing Na2O has been chosen, which can be used for low-temperature bonding with a higher bonding rate for the manufacture of microelectronic mechanical systems. The microstructure of the glass-ceramic is analyzed by transmission electron microscopy, high resolution transmission electron microscopy, selected-area diffraction, energy dispersive spectrometry and X-ray diffraction. The influence of the heat treatment process of the glass on the properties and the microstructure of the glass-ceramics is discussed. The microstructure of the glass-ceramic has the continuous glassy region with higher alkali metal ion content, which benefits the low-temperature anodic bonding. 相似文献
994.
IntroductionThecomprehensivemathematicalmodeldevelopedinthefirstpartofthispaper[1]containsdozensofcoupledequationsthatformalargenonlinearequationsystem.Herewecombineanalyticalandnumericalmethodstosolveitanddiscussandanalyzesomeimportantproblemsinmicroc… 相似文献
995.
996.
The Schur-convexity at the upper and lower limits of the integral for the mean of a convex function is researched. As applications, a form with a parameter of Stolarsky’s mean is obtained and a relevant double inequality that is an extension of a known inequality is established. 相似文献
997.
A simple procedure for the systematical synthesis of eight distamycin analogues containing N‐methylpyrrole (Py) and N‐methylimidazole (Im) has been developed by a chloroform reaction and DCC coupling reaction without amino protection and deprotection, and the interaction of the analogues with Herring Sperm DNA was investigated by fluorescence spectroscopy. 相似文献
998.
999.
A kind of function-valued Padé-type approximant via the formal orthogonal polynomials (FPTAVOP) is introduced on the polynomial space and an algorithm is sketched by means of the formal orthogonal polynomials. This method can be applied to approximate characteristic values and the corresponding characteristic function of Fredholm integral equation of the second kind. Moreover, theoretical analyses show that FPTAVOP method is the most effective one for accelerating the convergence of a sequence of functions. In addition, a typical numerical example is presented to illustrate when the estimates of characteristic value and characteristic function by using this new method are more accurate than other methods. 相似文献
1000.