全文获取类型
收费全文 | 2141篇 |
免费 | 63篇 |
国内免费 | 5篇 |
专业分类
化学 | 1378篇 |
晶体学 | 20篇 |
力学 | 51篇 |
数学 | 193篇 |
物理学 | 567篇 |
出版年
2023年 | 21篇 |
2022年 | 39篇 |
2021年 | 23篇 |
2020年 | 45篇 |
2019年 | 39篇 |
2018年 | 38篇 |
2017年 | 43篇 |
2016年 | 53篇 |
2015年 | 60篇 |
2014年 | 78篇 |
2013年 | 134篇 |
2012年 | 157篇 |
2011年 | 165篇 |
2010年 | 114篇 |
2009年 | 93篇 |
2008年 | 131篇 |
2007年 | 131篇 |
2006年 | 102篇 |
2005年 | 92篇 |
2004年 | 60篇 |
2003年 | 57篇 |
2002年 | 44篇 |
2001年 | 26篇 |
2000年 | 27篇 |
1999年 | 35篇 |
1998年 | 17篇 |
1997年 | 18篇 |
1996年 | 15篇 |
1995年 | 17篇 |
1994年 | 18篇 |
1993年 | 19篇 |
1992年 | 25篇 |
1991年 | 18篇 |
1990年 | 16篇 |
1989年 | 15篇 |
1988年 | 14篇 |
1987年 | 20篇 |
1985年 | 19篇 |
1984年 | 18篇 |
1983年 | 14篇 |
1982年 | 16篇 |
1981年 | 12篇 |
1980年 | 9篇 |
1979年 | 13篇 |
1978年 | 9篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1975年 | 10篇 |
1974年 | 7篇 |
1973年 | 6篇 |
排序方式: 共有2209条查询结果,搜索用时 15 毫秒
921.
Phototoxicity of Some Bromine-Substituted Rhodamine Dyes: Synthesis, Photophysical Properties and Application as Photosensitizers 总被引:2,自引:0,他引:2
Prabir Pal Hualing Zeng Gilles Durocher Denis Girard Tiechao Li Ajay K. Gupta Richard Giasson Louise Blanchard Louis Gaboury Antonia Balassy Chantal Turmel ré Laperrière Luc Villeneuve 《Photochemistry and photobiology》1996,63(2):161-168
Abstract— The synthesis of some bromine-substituted rhodamine derivatives viz. , 4,5-dibromorhodamine methyl ester (dye 2) and 4,5-dibromorhodamine n -butyl ester (dye 3) are reported. These dyes were synthesized to promote a more efficient cancer cell photosensitizer for potential use in in vitro bone marrow purging in preparation for autologous bone marrow transplantation. Spectroscopic and photo-physical characterization of these dyes together with rhodamine 123 (dye 1) are reported in water, methanol, eth-anol and also in a microheterogeneous system, sodium dodecyl sulfate. The possible mechanism of photosensi-tization is characterized in terms of singlet oxygen efficiency of these dyes. Singlet oxygen quantum yields for bromine-substituted dyes are in the range of 0.3-0.5 depending on the solvent. For dye 1 no singlet oxygen production is found. The photodynamic actions of these dyes in different cell lines are tested. It was found that dye 2 and dye 3 are efficient photosensitizers and mediate eradication of K562, EM2, myeloid cell lines (CML) and the SMF-AI rhabdomyosarcoma line. 相似文献
922.
We present a topological minimax theorem (Theorem 2.2). The topological assumptions on the spaces involved are somewhat weaker than those usually found in the literature. Even when reinterpreted in the convex setting of topological vector spaces, our theorem yields nonnegligible improvements, for example, of the Passy–Prisman theorem and consequently of the Sion theorem, contrary to most results on topological minimax. This work is part of our ongoing effort to elaborate a coherent theory of minimax. 相似文献
923.
In this article, we consider the problem of estimating a p-variate (p ≥ 3) normal mean vector in a decision-theoretic setup. Using a simple property of the noncentral chi-square distribution, we have produced a sequence of smooth estimators dominating the James-Stein estimator and each improved estimator is better than the previous one. It is also shown by using a technique of [5]. J. Multivariate Anal.36 121–126) that our smooth estimators can be dominated by non-smooth estimators. 相似文献
924.
925.
926.
We investigate the possibility that family symmetry, GF, is spontaneously broken chiral global symmetry. We classify the interesting cases when family symmetry can result in an automatic Peccei-Quinn symmetry U(1)PQ and thus provide a solution to the strong CP problem. The result disfavors having two or four families. For more than four families, U(1)PQ is in general automatic. In the case of three families, a unique Higgs sector allows U(1)PQ in the simplest case of GF = [SU(3)]3. Cosmological consideration also puts strong constraint on the number of families. For GF = [SU(N)]3 cosmology singles out the three-family (N = 3) case as a unique solution if there are three light neutrinos. Possible implication of decoupling theorem as applied to family symmetry breaking is also discussed. 相似文献
927.
Six different hydroxyanthraquinones (HAQs) in aqueous micellar (cationic, anionic and non-ionic) media were tested as effective and selective chelators for the MgII ion in alkaline conditions. Of these 1,4 and 1,8-dihydroxyanthraquinones were found to effectively bind to MgII ions and were useful for the ppm level spectral determination of MgII ion. The MgII ion forms 1 : 1 and 1 : 2 chelates with 1,4-and 1,8-dihydroxyanthraquinones, respectively, which have maximum absorption at 610 and 575 nm, respectively. MgII can be determined in the presence of a large excess of foreign ions including the CaII ion. The statistical analysis of the results, apparent pK(a), expected bathchromic shift of the reagent absorption, molar absorptivity change and electronic spectra in various organized media are discussed. 相似文献
928.
929.
930.