全文获取类型
收费全文 | 6729篇 |
免费 | 949篇 |
国内免费 | 637篇 |
专业分类
化学 | 2955篇 |
晶体学 | 6篇 |
力学 | 399篇 |
综合类 | 172篇 |
数学 | 3487篇 |
物理学 | 1296篇 |
出版年
2024年 | 14篇 |
2023年 | 55篇 |
2022年 | 148篇 |
2021年 | 141篇 |
2020年 | 226篇 |
2019年 | 151篇 |
2018年 | 177篇 |
2017年 | 192篇 |
2016年 | 322篇 |
2015年 | 267篇 |
2014年 | 387篇 |
2013年 | 506篇 |
2012年 | 437篇 |
2011年 | 466篇 |
2010年 | 384篇 |
2009年 | 462篇 |
2008年 | 454篇 |
2007年 | 528篇 |
2006年 | 426篇 |
2005年 | 368篇 |
2004年 | 327篇 |
2003年 | 317篇 |
2002年 | 219篇 |
2001年 | 198篇 |
2000年 | 160篇 |
1999年 | 146篇 |
1998年 | 148篇 |
1997年 | 126篇 |
1996年 | 108篇 |
1995年 | 65篇 |
1994年 | 54篇 |
1993年 | 45篇 |
1992年 | 41篇 |
1991年 | 36篇 |
1990年 | 16篇 |
1989年 | 19篇 |
1988年 | 21篇 |
1987年 | 13篇 |
1986年 | 12篇 |
1985年 | 18篇 |
1984年 | 15篇 |
1983年 | 9篇 |
1982年 | 18篇 |
1981年 | 11篇 |
1980年 | 19篇 |
1979年 | 16篇 |
1978年 | 9篇 |
1977年 | 8篇 |
1976年 | 3篇 |
1973年 | 3篇 |
排序方式: 共有8315条查询结果,搜索用时 15 毫秒
11.
Browder-Petryshyn 型的严格伪压缩映射的粘滞迭代逼近方法 总被引:1,自引:0,他引:1
主要研究Browder-Petryshyn型的严格伪压缩映射的粘滞迭代逼近过程,证明了Browder-Petryshyn型的严格伪压缩映射的不动点集F(T)是闭凸集.在q-一致光滑且一致凸的Banach空间中,对于严格伪压缩映射T,利用徐洪坤在2004年引进的粘滞迭代得到的序列弱收敛于T的某个不动点.同时证明了Hilbert空间中Browder-Petryshyn型的严格伪压缩映射的相应迭代序列强收敛到T的某个不动点,其结果推广与改进了徐洪坤2004年的相应结果. 相似文献
12.
Liang-gen Hu 《应用数学学报(英文版)》2007,23(2):281-288
In this paper,we will establish several strong convergence theorems for the approximation ofcommon fixed points of r-strictly asymptotically pseudocontractive mappings in uniformly convex Banachspaces using the modiied implicit iteration sequence with errors,and prove the necessary and sufficient conditionsfor the convergence of the sequence.Our results generalize,extend and improve the recent work,in thistopic. 相似文献
13.
Heinz H. Bauschke 《Proceedings of the American Mathematical Society》2007,135(1):135-139
Recently, S. Reich and S. Simons provided a novel proof of the Kirszbraun-Valentine extension theorem using Fenchel duality and Fitzpatrick functions. In the same spirit, we provide a new proof of an extension result for firmly nonexpansive mappings with an optimally localized range.
14.
15.
O. Wibbelhoff C. Meier A. Lorke P. Schafmeister A. D. Wieck 《Physica E: Low-dimensional Systems and Nanostructures》2004,21(2-4):516
We use frequency-dependent capacitance–voltage spectroscopy to study the dynamic charging of self-assembled InAs quantum dots. With increasing frequency, the AC charging becomes suppressed, beginning with the low-energy states. By applying an in-plane magnetic field, we generate an additional magnetic confinement that alters the tunneling barrier and hence the charging dynamics. In traveling through the potential barrier, the electrons acquire an additional momentum k0, proportional to the magnetic field B. As the tunneling is enhanced, when k0 matches the maximum of the electronic wave function Ψ (in momentum representation), we are able to map out the shape of Ψ by varying B. 相似文献
16.
New Exact Solutions to the Combined KdV and mKdV Equation 总被引:2,自引:0,他引:2
Yan-ze Peng 《International Journal of Theoretical Physics》2003,42(4):863-868
The modified mapping method is developed to obtain new exact solutions to the combined KdV and mKdV equation. The method is applicable to a large variety of nonlinear evolution equations, as long as odd- and even-order derivative terms do not coexist in the equation under consideration. 相似文献
17.
Qinghai He 《Journal of Mathematical Analysis and Applications》2007,333(2):1070-1078
In this paper, variational conclusions of set-valued bifunctions on convex subsets of Banach spaces are investigated and several new results are obtained. The results are applied to the fixed point theory and variational inequalities. We obtain two fixed point theorems and existence theorems of solutions of variational inequalities. 相似文献
18.
Electric fields of the anions, cations and neutral forms of 2-aminopurine and 6-thioguanine have been mapped. Certain important
features of the maps are similar to those found earlier in the neutral and ionic forms of adenine and guanine. The computed
electric field patterns satisfactorily explain reactive sites and biological activity of the molecules. 相似文献
19.
Thin films of polystyrene (PS), poly(methyl methacrylate) (PMMA) and polystyrene-polyacrylonitrile copolymer (PS-AN), containing various embedded transition-metal complexes, have been studied by FTIR microscopy. The spatial distributions of the transition-metal carbonyl complexes throughout the thin organic polymer films have been determined by a two-dimensional IR mapping procedure. The spectral variations observed in the distribution of the metal carbonyls throughout the different polymer films are discussed. The IR data show that the technique used to prepare the organometallic-embedded thin films (viz. freeze-drying of solutions followed by hot mechanical pressing of the residues) does in general lead to homogeneous films which may eventually find industrial application, e.g. as membrane sensors for small molecules. 相似文献
20.
There is a high correlation between molecular surface area (TSA) of triorganotin and triorganolead compounds and their toxicity towards a bacterium (Escherichia coli) and an alga (Selenastrum capricornutum). Parallel attempts to correlate other Group IVA organometals incorporating silicon or germanium were unsuccessful. It was further demonstrated, however, that a high correlation was obtainable between certain series of compounds with the same organic substituent but different metal centers involving all Group IVA elements. In both instances, the inability to obtain a quantitative structure-activity relationship (QSAR) for all systems studied appears to be a function of the solubility of the compounds. While organotin TSA values have been found to correlate well with their toxicities toward various organisms, this study clearly suggests that this type of QSAR can be readily extended to include other organometal systems, provided that there is no solubility problem and the toxicity is a function of the hydrophobicity of the organometal compounds. 相似文献