全文获取类型
收费全文 | 201620篇 |
免费 | 32995篇 |
国内免费 | 24100篇 |
专业分类
化学 | 137012篇 |
晶体学 | 2347篇 |
力学 | 12808篇 |
综合类 | 1579篇 |
数学 | 25858篇 |
物理学 | 79111篇 |
出版年
2024年 | 630篇 |
2023年 | 3761篇 |
2022年 | 6727篇 |
2021年 | 7221篇 |
2020年 | 7844篇 |
2019年 | 7445篇 |
2018年 | 6937篇 |
2017年 | 6519篇 |
2016年 | 9504篇 |
2015年 | 9486篇 |
2014年 | 11581篇 |
2013年 | 15113篇 |
2012年 | 17882篇 |
2011年 | 18375篇 |
2010年 | 12930篇 |
2009年 | 12592篇 |
2008年 | 13397篇 |
2007年 | 11924篇 |
2006年 | 11085篇 |
2005年 | 9156篇 |
2004年 | 7185篇 |
2003年 | 5802篇 |
2002年 | 5462篇 |
2001年 | 4640篇 |
2000年 | 4022篇 |
1999年 | 4142篇 |
1998年 | 3457篇 |
1997年 | 3258篇 |
1996年 | 3240篇 |
1995年 | 2763篇 |
1994年 | 2522篇 |
1993年 | 2090篇 |
1992年 | 1832篇 |
1991年 | 1618篇 |
1990年 | 1360篇 |
1989年 | 1030篇 |
1988年 | 782篇 |
1987年 | 671篇 |
1986年 | 675篇 |
1985年 | 533篇 |
1984年 | 339篇 |
1983年 | 284篇 |
1982年 | 231篇 |
1981年 | 147篇 |
1980年 | 101篇 |
1979年 | 57篇 |
1978年 | 32篇 |
1976年 | 28篇 |
1975年 | 28篇 |
1957年 | 52篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Nickel complexes 1–4 ligated with 2,9-disubstituted-1,10-phenanthroline were synthesized and characterized by FT-IR spectra and elemental analysis.
The molecular structure of complex 2 was confirmed by X-ray crystal diffraction analysis. Activated with methylaluminoxane (MAO), those complexes showed moderate
activities for ethylene oligomerization.
Published in Kinetika i Kataliz, 2007, Vol. 48, No. 5, pp. 710–714.
This article was submitted by the authors in English. 相似文献
62.
63.
64.
Anti-BZ-Structure in Effect Algebras 总被引:1,自引:0,他引:1
The definitions of sharply approximating effect algebras, anti-BZ-effect algebras, central approximating effect algebras, and S-anti-BZ-effect algebras are given, the relationships between sharply approximating effect algebras and anti-BZ-effect algebras, between central approximating effect algebras and anti-BZ-effect algebras are established, and the set of anti-BZ-sharp elements in S-anti-BZ-effect algebras is proved to be an orthomodular lattice. 相似文献
65.
Guobao Zhang Jianming Zhang Shenguo Wang Deyan Shen 《Journal of Polymer Science.Polymer Physics》2003,41(1):23-30
Blends of amorphous poly(DL‐lactide) (DL‐PLA) and crystalline poly(L‐lactide) (PLLA) with poly(methyl methacrylate) (PMMA) were prepared by both solution/precipitation and solution‐casting film methods. The miscibility, crystallization behavior, and component interaction of these blends were examined by differential scanning calorimetry. Only one glass‐transition temperature (Tg) was found in the DL‐PLA/PMMA solution/precipitation blends, indicating miscibility in this system. Two isolated Tg's appeared in the DL‐PLA/PMMA solution‐casting film blends, suggesting two segregated phases in the blend system, but evidence showed that two components were partially miscible. In the PLLA/PMMA blend, the crystallization of PLLA was greatly restricted by amorphous PMMA. Once the thermal history of the blend was destroyed, PLLA and PMMA were miscible. The Tg composition relationship for both DL‐PLA/PMMA and PLLA/PMMA miscible systems obeyed the Gordon–Taylor equation. Experiment results indicated that there is no more favorable trend of DL‐PLA to form miscible blends with PMMA than PLLA when PLLA is in the amorphous state. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 23–30, 2003 相似文献
66.
本文提出的MMD算法用于提高模型区别错误信息和正确信息的能力.利用该算法在对模型的参数进行重估计时.涉及到复杂的目标函数的梯度运算.击运用矩阵运算使得梯度运算变得简单明了,因此本文给出了MMD算法下的HMM参数重估计的矩阵表示形式并给出了证明. 相似文献
67.
Zhang Meirong 《数学年刊B辑(英文版)》1989,10(3):416-425
This paper considers the following question: Given an Anosov endomorphism f on T~m, whether f is topologically conjugate to some hyperbolic total endomorphism? It is well known that the answer for Anosov diffeomorphisms and expanding endomorphisms is affirmative. Hwever for the remainder Anosov endomorphisms, a quite different answer is obtained in this paper, i. e., for generic Anosov endomorphisms, they are not topologically conjugate to any hyperbolic toral endomorphism. 相似文献
68.
We present the cosmological solutions in the six-dimensional Einstein-gauge theory to which is added a matter term. The general behavior of the scale factors of the ordinary (R3) and extra (R2) dimensions can be depicted in four stages. Stage 1: Both R3 and R2 expand. Stage 2: R2 is a constant and R3 is an inflationary solution. Stage 3: R2 recollapses towards its minimum value, R3 will continue to increase monotonically. Stage 4: R2 stabilizes at RKK and R3 expands in the usual FRW way, while the four-dimensional cosmological constant becomes zero. 相似文献
69.
激光晶体YAG中Er3+的辐射跃迁 总被引:2,自引:0,他引:2
本文讨论和分析了激光晶体YAG中Er3+离子的激光上能级的4S3/2、4I11/2和4I13/2辐射跃迁的有关因素。 相似文献
70.
ZhenFengZHANG 《数学学报(英文版)》2005,21(1):155-168
In this paper, we extend a classical result of Hua to arithmetic progressions with large moduli. The result implies the Linnik Theorem on the least prime in an arithmetic progression. 相似文献