全文获取类型
收费全文 | 19388篇 |
免费 | 1589篇 |
国内免费 | 1526篇 |
专业分类
化学 | 1756篇 |
晶体学 | 28篇 |
力学 | 1088篇 |
综合类 | 146篇 |
数学 | 8450篇 |
物理学 | 2518篇 |
综合类 | 8517篇 |
出版年
2024年 | 38篇 |
2023年 | 145篇 |
2022年 | 239篇 |
2021年 | 309篇 |
2020年 | 432篇 |
2019年 | 459篇 |
2018年 | 402篇 |
2017年 | 475篇 |
2016年 | 541篇 |
2015年 | 538篇 |
2014年 | 874篇 |
2013年 | 1365篇 |
2012年 | 1028篇 |
2011年 | 1117篇 |
2010年 | 899篇 |
2009年 | 1157篇 |
2008年 | 1052篇 |
2007年 | 1276篇 |
2006年 | 1155篇 |
2005年 | 1034篇 |
2004年 | 937篇 |
2003年 | 863篇 |
2002年 | 824篇 |
2001年 | 660篇 |
2000年 | 623篇 |
1999年 | 601篇 |
1998年 | 475篇 |
1997年 | 501篇 |
1996年 | 374篇 |
1995年 | 321篇 |
1994年 | 270篇 |
1993年 | 214篇 |
1992年 | 221篇 |
1991年 | 168篇 |
1990年 | 158篇 |
1989年 | 144篇 |
1988年 | 103篇 |
1987年 | 73篇 |
1986年 | 58篇 |
1985年 | 57篇 |
1984年 | 60篇 |
1983年 | 25篇 |
1982年 | 42篇 |
1981年 | 39篇 |
1980年 | 37篇 |
1979年 | 37篇 |
1978年 | 18篇 |
1977年 | 24篇 |
1976年 | 24篇 |
1974年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
61.
Wuqing Ning 《Journal of Mathematical Analysis and Applications》2007,327(2):1396-1419
In this paper, an algorithm is established to reconstruct an eigenvalue problem from the given data satisfying certain conditions. These conditions are proved to be not only necessary but also sufficient for the given data to coincide with the spectral characteristics corresponding to the reconstructed eigenvalue problem. 相似文献
62.
In this work, the melting behaviors of nonisothermally and isothermally melt‐crystallized poly(L ‐lactic acid) (PLLA) from the melt were investigated with differential scanning calorimetry (DSC) and temperature‐modulated differential scanning calorimetry (TMDSC). The isothermal melt crystallizations of PLLA at a temperature in the range of 100–110 °C for 120 min or at 110 °C for a time in the range of 10–180 min appeared to exhibit double melting peaks in the DSC heating curves of 10 °C/min. TMDSC analysis revealed that the melting–recrystallization mechanism dominated the formation of the double melting peaks in PLLA samples following melt crystallizations at 110 °C for a shorter time (≤30 min) or at a lower temperature (100, 103, or 105 °C) for 120 min, whereas the double lamellar thickness model dominated the formation of the double melting peaks in those PLLA samples crystallized at a higher temperature (108 or 110 °C) for 120 min or at 110 °C for a longer time (≥45 min). © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 466–474, 2007 相似文献
63.
吴臻 《数学物理学报(B辑英文版)》2004,24(1):91-99
The existence and uniqueness results of fully coupled forward-backward stochastic differential equations with stopping time (unbounded) is obtained. One kind of comparison theorem for this kind of equations is also proved. 相似文献
64.
N. E. Tovmasyan H. A. Babayan 《Journal of Contemporary Mathematical Analysis (Armenian Academy of Sciences)》2007,42(4):198-204
The paper establishes some solvability conditions of the Cauchy problem for linear differential equation in the class of monotone increasing functions. The results are applied for clarifying the possibility of flight along a given trajectory under existence of braking forces. 相似文献
65.
Let P(z) be a polynomial of degree n with complex coefficients and consider the n–th order linear differential operator P(D). We show that the equation P(D)f = 0 has the Hyers–Ulam stability, if and only if the equation P(z) = 0 has no pure imaginary solution. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
66.
P. Q. Khanh 《Journal of Optimization Theory and Applications》1995,87(2):359-378
We prove the Kuhn-Tucker sufficient optimality condition, the Wolfe duality, and a modified Mond-Weir duality for vector optimization problems involving various types of invex-convexlike functions. The class of such functins contains many known generalized convex functions. As applications, we demonstrate that, under invex-convexlikeness assumptions, the Pontryagin maximum principle is a sufficient optimality condition for cooperative differential games. The Wolfe duality is established for these games.The author is indebted to the referees and Professor W. Stadler for valuable remarks and comments, which have been used to revise considerably the paper. 相似文献
67.
李扬国 《汕头大学学报(自然科学版)》1992,7(1):9-16
在已获得的中能区反质子与核的中心势的光学势基础上,把光学势扩大到包含自旋轨道耦合势.在反质子能量为179.8,294.8和508MeV各情况下,分别计算和分析与~(12)C靶核的微分截面(dσ)/(dΩ),极化度P(θ)和自旋转动函数Q(θ).在与极化度的实验比较中,得到中能区普遍形式的反质子光学势. 相似文献
68.
用离散余弦变换(DCT)的一种快速算法按“方差准则”实现心电图(ECG)数据压缩.这种算法减少了乘法次数且结构简单.采用分段变换的方法,能有效地进行心电图数据压缩. 相似文献
69.
Carlos E. Alciaturi Thais Montero Carlos De La Cruz Marcos E. Escobar 《Analytica chimica acta》1997,340(1-3):233-240
Reduction of the representation of infrared spectra from coal samples by osculating polynomials of degree nine is discussed. The reduced representation contains polynomial coefficients of order zero to four. Mathematical models of the original spectra are obtained by linear combination of the coefficients. These compressed models are statistically correlated to coal properties, namely, volatile matter, fixed carbon, ash content, heating value, hydrogen, carbon, sulphur, nitrogen, and maximum vitrinite reflectance, and the results are compared with those previously obtained from second derivatives of the same spectra. The use of compressed data, while giving slightly better correlations for some of the properties, has the advantage of requiring less computational time. 相似文献
70.
安韶君 《中山大学学报(自然科学版)》2002,41(5):11-14
图视密码学方案最初由Naor和Shamir在 1994年欧洲密码学会议上提出 ,但像素扩展太大 ,生成分存图像太大。采用小波变换对分存图像进行压缩 ,有效地降低了分存图像规模。 相似文献