全文获取类型
收费全文 | 6596篇 |
免费 | 1160篇 |
国内免费 | 1063篇 |
专业分类
化学 | 3326篇 |
晶体学 | 35篇 |
力学 | 482篇 |
综合类 | 73篇 |
数学 | 1130篇 |
物理学 | 3773篇 |
出版年
2024年 | 7篇 |
2023年 | 87篇 |
2022年 | 178篇 |
2021年 | 173篇 |
2020年 | 241篇 |
2019年 | 221篇 |
2018年 | 182篇 |
2017年 | 200篇 |
2016年 | 220篇 |
2015年 | 224篇 |
2014年 | 312篇 |
2013年 | 585篇 |
2012年 | 408篇 |
2011年 | 413篇 |
2010年 | 337篇 |
2009年 | 422篇 |
2008年 | 473篇 |
2007年 | 465篇 |
2006年 | 457篇 |
2005年 | 389篇 |
2004年 | 367篇 |
2003年 | 332篇 |
2002年 | 285篇 |
2001年 | 220篇 |
2000年 | 231篇 |
1999年 | 191篇 |
1998年 | 193篇 |
1997年 | 167篇 |
1996年 | 106篇 |
1995年 | 99篇 |
1994年 | 85篇 |
1993年 | 74篇 |
1992年 | 77篇 |
1991年 | 60篇 |
1990年 | 46篇 |
1989年 | 35篇 |
1988年 | 35篇 |
1987年 | 32篇 |
1986年 | 27篇 |
1985年 | 27篇 |
1984年 | 12篇 |
1983年 | 10篇 |
1982年 | 25篇 |
1981年 | 19篇 |
1980年 | 16篇 |
1979年 | 11篇 |
1978年 | 12篇 |
1977年 | 11篇 |
1976年 | 7篇 |
1973年 | 4篇 |
排序方式: 共有8819条查询结果,搜索用时 15 毫秒
51.
M. Nagy 《Colloid and polymer science》1985,263(3):245-265
52.
摘要运用多参考微扰理论(Multireference MΦller-Plesset theory)计算了SSCH3垂直激发能及其S-C与S-S两种断键方式的绝热(Adiabatic)与非绝热(Diabatic)的基态和激发态势能曲线, 研究了在193nm激光作用下SSCH3的光解离过程, 理论计算值与实验值相符. 相似文献
53.
The electrostatic field associated with one complete turn of B-DNA is presented. Two base sequences poly (dG) · poly (dC) and poly (dA) · poly (dT) are studied and the effects of sodium counterions bound to the nucleic acid are investigated. The contrasts between the electrostatic potential and the electrostatic field of the macromolecules are discussed and the possible applications of the field are considered. 相似文献
54.
The dialysis potentials of different collodion membranes with graded pore sizes and electrochemical activities have been measured in dilute aqueous KCl solutions as functions of concentration. It is possible to predict the value of the diffusion potential within a few millivolts on the basis of electrical conductivity data obtained with the same membranes. In general, the measured values are lower than those calculated. It is assumed that this difference is caused by the membranes having a distribution of pore sizes. 相似文献
55.
二氧化碳和氧气的快速电化学方法联合测定 总被引:4,自引:0,他引:4
根据O2和CO2在二甲亚砜(DMSO)介质中Pt电极上的伏安特性,采用微电极并结构计算机控制的电位调制技术,建立了快速联合测定CO2和O2的调制电位脉冲库仑法和调制电位脉冲电流法,取得了满意的结果。一次测量时间快达40ms。CO2检测范围0 ̄10%(体积百分比);O2检测范围不受限制。通过编程设计特定的调制电位-时间波形,可保持连续检测的长期稳定性。 相似文献
56.
Shin-ichi Naya 《Tetrahedron》2004,60(23):4953-4958
The synthesis and properties of a novel type of 7,7-bis(heteroazulen-3-yl)-8,8-dicyano-1,4-quinodimethanes (9a-c) are studied. The synthetic method is based on a TFA-catalyzed electrophilic aromatic substitution on the heteroazulenes with 4-(dicyanomethyl)benzaldehyde to afford the corresponding methane derivatives, followed by oxidative hydrogen abstraction with DDQ. The polarization of 9a-c is evaluated by the inspection of their 13C NMR and IR spectra. Based on the investigation of the UV-Vis spectra of 9a-c and protonated cations 10a-c, conformational changes of the heteroazulene-moiety and (dicyanomethyl)phenyl group are suggested. In the CV measurements of 9a-c, two reversible reduction waves are observed, indicating the stabilizing ability of heteroazulenes toward the corresponding radical and anion species. Furthermore, 9a-c exhibit two irreversible oxidation waves, which suggest a conformational change in the radical cation during the redox process. The conformational change is rationalized on the basis of the MO calculations. 相似文献
57.
UV absorption spectra of acetyl fluoride-h3 and -d3 (CH3COF and CD3COF) molecules in the region of S1S0 electronic transitions are investigated. The origins (00
0 or 140±
0) of these transitions are observed at 39912 and 39904 cm–1, respectively, and some of the fundamental frequencies of these molecules in the s0 and S1 states are determined. In particular, the systems of torsion and inversion (out-of-plane C=O vibrations) energy levels are studied. The geometric parameters of an acetyl fluoride-h3 molecule in the S1 state are estimated by the theoretical simulation of the rotational contours of the 00
0 (140±
0) band. These data are used to evaluate the potential barriers to internal rotation in the S0 and S1 states, which were found to be 360 and 560 cm–1 for acetyl fluoride-h3 and 380 and 770 cm–1 for acetyl fluoride-d3, respectively, as well as the potential barriers to inversion in the S1 states, which were found to be 2090 and 2370 cm–1 for acetyl fluoride-h3 and acetyl fluoride-d3, respectively.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1957–1964, November, 1994.In conclusion, the authors would like to acknowledge T. S. Kuznetsova for the synthesis and purification of the AF samples.The research presented here was supported in part by the International Science Foundation under grant No. MJ 1000. 相似文献
58.
构造了氮-镍相互作用的5-参数Morse势,研究了氮原子在Ni(\r\n100),Ni(110)和Ni(111)平坦表面的吸附和振动,获得了氮原子\r\n在三个低指数表面的吸附位、吸附构型、结合能和本征振动等数据,计\r\n算结果与实验结果非常吻合.同时,与Ni(100)表面对比,系统研究\r\n了氮原子在Ni(510)台阶面的吸附和扩散.计算结果表明,氮原子在\r\n台阶下部形成最稳定的吸附态,台阶对下台面上扩散的氮原子形成捕获\r\n势,对上台面上扩散的氮原子形成反射势. 相似文献
59.
A. Gil 《Adsorption》1998,4(3-4):197-206
The micropore structure of four microporous materials (two zeolites, ZSM-5 and Y-82; an activated carbon and an alumina pillared clay) and their binary physical mixtures (50-50 wt%) have been examined by nitrogen adsorption at 77 K. Various micropore sizes have been considered from the stages on the micropore filling mechanism in the microporous materials. The application of the Dubinin-Astakhov (DA) equation to characterize and obtain the adsorption potential distributions of the microporous materials is presented. 相似文献
60.
Laurent Chaloin Nicole Van Mau Frédéric Heitz Laurent Chiche Jean-Claude Talbot 《Colloids and surfaces. B, Biointerfaces》1998,10(6):389R-412
In order to elucidate the influence on the lipidic environment on the recognition process of its membrane associated receptor, the interactions of the vasoconstrictor peptide endothelin 1 with various phospholipids have been investigated using different lipidic model membranes: monolayers at constant surface pressure, vesicles and micelles. A monolayer study of ET1 adsorbed onto the water surface has shown that the C-terminus of the peptide points towards the aqueous phase. Penetration measurements into lipidic monolayers indicate that ET1 adsorbs to phospholipids with an orientation similar to that of the air–water interface and fluorescence measurements are in agreement with such an orientation of the peptide. This adsorption is selective for neutral phospholipids and indicates that the nature of the phospholipid headgroups is of major importance for the approach of the membrane associated receptor. 相似文献