全文获取类型
收费全文 | 31719篇 |
免费 | 3401篇 |
国内免费 | 3523篇 |
专业分类
化学 | 24301篇 |
晶体学 | 346篇 |
力学 | 1185篇 |
综合类 | 189篇 |
数学 | 4213篇 |
物理学 | 8409篇 |
出版年
2024年 | 41篇 |
2023年 | 429篇 |
2022年 | 441篇 |
2021年 | 887篇 |
2020年 | 897篇 |
2019年 | 926篇 |
2018年 | 745篇 |
2017年 | 659篇 |
2016年 | 1266篇 |
2015年 | 1183篇 |
2014年 | 1429篇 |
2013年 | 2346篇 |
2012年 | 2639篇 |
2011年 | 2763篇 |
2010年 | 1812篇 |
2009年 | 1902篇 |
2008年 | 1999篇 |
2007年 | 1933篇 |
2006年 | 1709篇 |
2005年 | 1679篇 |
2004年 | 1736篇 |
2003年 | 1338篇 |
2002年 | 1317篇 |
2001年 | 897篇 |
2000年 | 668篇 |
1999年 | 558篇 |
1998年 | 492篇 |
1997年 | 432篇 |
1996年 | 456篇 |
1995年 | 376篇 |
1994年 | 328篇 |
1993年 | 314篇 |
1992年 | 265篇 |
1991年 | 207篇 |
1990年 | 173篇 |
1989年 | 162篇 |
1988年 | 132篇 |
1987年 | 100篇 |
1986年 | 98篇 |
1985年 | 136篇 |
1984年 | 137篇 |
1983年 | 92篇 |
1982年 | 80篇 |
1981年 | 75篇 |
1980年 | 65篇 |
1979年 | 34篇 |
1978年 | 31篇 |
1977年 | 38篇 |
1976年 | 29篇 |
1974年 | 30篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
自组装量子点材料作为一种新型的光电材料无论在理论和实际应用都成为当今物理学界的研 究热点.由GaAs包围的InAs小岛,由于较大的晶格失配(≈-0.067),应变效应在量子点 的 形成过程中起主导作用.大部分计算量子点结构应变分布的方法都是基于数值解法,需要大 量的计算工作.给出用格林函数法推导各种常见形状量子点应变分布的解析表达式详细过程,讨论了弹性各向异性和形状各向异性对量子点应变分布的影响程度.结果表明对于不 同形状量子点结构中主要部分的应变分布都是相似的,流体静压变部分的特征值随量子点形状的变化不
关键词:
自组装量子点
格林函数
应变分布 相似文献
82.
83.
A class of chiral ketone was synthesized for asymmetric epoxidation. High ee values have been obtained for a number of cis olefin and trans olefin. The epoxidation was stereospecific with no isomerizatiom observed in the epoxidation of acyclic system. Encourageingly high ee value has also been obtained for a number of terminal olefins. Mechanistic studies show that electronic interactions play an important role in the stereodifferentiation. O O O O O O NBoc O O t-BuO2CH2CN O O O … 相似文献
84.
5,6-Dihydro-OSW-1 (1) was synthesized following our previous procedure for the total synthesis of OSW-1. This compound demonstrated slightly stronger potency than that of OSW-1 against the growth of cancer cells. 相似文献
85.
Gui Hong YAN Da XING* Shi Ci TAN Institute of Laser Life Science South China Normal University Guangzhou 《中国化学快报》2004,15(1):101-104
Electrochemiluminescence (ECL), like other chemiluminescence technique, offers high signal-to-noise ratio. Furthermore, it has the advantage over other chemiluminescence techniques of being initiated by a voltage potential. Thus, it provides a better-controlled luminescence. This technique has been used in measuring many kinds of organic and inorganic matters, and analyzing many kinds of antigen, antibody and hapten, such as carcinoembryonic antigen and alpha-fetoprotein, etc1-6. The ele… 相似文献
86.
The First Intramolecular Charge Transfer Transition Based on 2-Ureido-4[1H]-pyrimidinone Binding Module 总被引:1,自引:0,他引:1
The first intramolecular charge transfer transition based on 2-ureido-4[1H]-pyrimidinone binding module was reported. 相似文献
87.
The first hyperpolarizabilities of a series of novel azulenic-barbituric acid chromophores have been studied by using 12 excitation wavelengths, ranging from 900 to 1907 nm. The dispersion relation of the first hyperpolarizabilities of chromophores holds the same tendency as the experimental results. In addition, the static first hyperpolarizability β0 of molecules was calculated by means of the Sum-Over-States (SOS) expression and the two-level formula respectively. The results show that these molecules possess large static first hyperpolarizabilities and the, β0 value increases as the donor or acceptor strength enhances; the distorted degree of molecules has also an important influence on the β0 value. 相似文献
88.
Solid Phase Synthesis of 2-Substituted 1,3-Oxazin-6-ones Using Resin-bound Cyclic Malonic Acid Ester
A facile solid phase synthesis of 2-substituted 1,3-oxazin-6-ones using polymer-supported Meldrum‘s acid has been reported. Reaction of the resin-bound cyclic malonic acid ester with triethyl orthoformate and subsequent double substitution with amide, afforded the corresponding polymer-supported acylaminomethylene cyclic malonic acid ester, which upon thermal treatment led to 1, 3-oxazin-6-ones in good yields and with high purity. 相似文献
89.
JianXinCAO YiFengWANG GuoFangLAI ShiDeLUO 《中国化学快报》2004,15(7):797-800
From the dried aerial part ofParepigynumfuningesis Tsiang et P. T. Li (Apocynaceae),a new cardiac glucoside, named parefuningoside (1) had been isolated. Its structure was determined by means of hydrolysis and spectral analysis. 相似文献
90.
Francesc Carreras M. Dolors Llongueras Antonio Magaña 《Annals of Operations Research》2005,137(1):67-89
A partnership in a cooperative game is a coalition that possesses an internal structure and, simultaneously, behaves as an
individual member. Forming partnerships leads to a modification of the original game which differs from the quotient game
that arises when one or more coalitions are actually formed.
In this paper, the Shapley value is used to discuss the convenience to form either coalitions or partnerships. To this end,
the difference between the additive Shapley value of the partnership in the partnership game and the Shapley alliance value
of the coalition, and also between the corresponding value of the internal and external players, are analysed. Simple games
are especially considered.
Research partially supported by Grant BFM 2003-01314 of the Science and Technology Spanish Ministry and the European Regional
Development Fund. 相似文献