全文获取类型
收费全文 | 20903篇 |
免费 | 2990篇 |
国内免费 | 2375篇 |
专业分类
化学 | 8404篇 |
晶体学 | 272篇 |
力学 | 661篇 |
综合类 | 171篇 |
数学 | 1216篇 |
物理学 | 4863篇 |
综合类 | 10681篇 |
出版年
2024年 | 109篇 |
2023年 | 462篇 |
2022年 | 756篇 |
2021年 | 890篇 |
2020年 | 871篇 |
2019年 | 734篇 |
2018年 | 650篇 |
2017年 | 658篇 |
2016年 | 828篇 |
2015年 | 1124篇 |
2014年 | 1327篇 |
2013年 | 1559篇 |
2012年 | 1706篇 |
2011年 | 1719篇 |
2010年 | 1385篇 |
2009年 | 1482篇 |
2008年 | 1579篇 |
2007年 | 1392篇 |
2006年 | 1201篇 |
2005年 | 1029篇 |
2004年 | 736篇 |
2003年 | 524篇 |
2002年 | 568篇 |
2001年 | 473篇 |
2000年 | 471篇 |
1999年 | 348篇 |
1998年 | 221篇 |
1997年 | 196篇 |
1996年 | 181篇 |
1995年 | 149篇 |
1994年 | 136篇 |
1993年 | 129篇 |
1992年 | 102篇 |
1991年 | 97篇 |
1990年 | 63篇 |
1989年 | 54篇 |
1988年 | 44篇 |
1987年 | 39篇 |
1986年 | 36篇 |
1985年 | 31篇 |
1984年 | 28篇 |
1983年 | 14篇 |
1982年 | 12篇 |
1980年 | 9篇 |
1978年 | 12篇 |
1966年 | 11篇 |
1965年 | 44篇 |
1964年 | 12篇 |
1959年 | 8篇 |
1957年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 375 毫秒
201.
In this paper, the chronoamperometry was used to study the charging processes of polyethylenedioxythiophene (PEDOT) modified electrodes in the potential range where PEDOT was in the oxidized state. The results show that the charging behaviors of the PEDOT films are well agreed with the exhausted finite diffusion model. The dependence of the capacitance values of the films on potential and concentration of solution was also studied in this potential range. 相似文献
202.
A reversed-phase ion-pair HPLC with indirect photometric detection for the simultaneous determination of sulfite, sulfate, hydroxymethanesulfonate (HMS), and other inorganic anions in atmospheric water has been developed. Separations were accomplished in less than 10 min in a cetylpyridinium-coated C18 column with 0.5 mM potassium hydrogen phthalate-0.015% triethanolamine-3% methanol at pH 7.9 as mobile phase. Quantitation was carried out by the peak area method, with detection limits in the pmol range. UV light absorption responses were linear over a wide concentration range from several hundred μmoles to the detection limits of each anion. The application of the method provides a rapid and efficient technique for the quantitative determination of sulfur and other inorganic species in atmospheric liquids. 相似文献
203.
A systematic quantum chemical characterization of intrinsic structure, energies and spectral properties of all the studied cross-link adducts formed by the novel trans platinum with thiazole ligand has been carried out at B3LYP/6-31G^* level of theory with the Lanl2dz pseudo potential basis set for the Pt atom. Special attention has been paid to the relative stability of these complexes and the factors that probably alter the order of the relative stability. The important influence of hydrogen bond on the structures, the energies and the spectral property was revealed. Other factors that contribute to relative stability including solvation effect, entropy and electronic delocalization energy were taken into account. The stability energy of the whole complex, and the interaction energy between two purine bases and the [Pt-(NH3)thiazole]^2+ group were adopted to study the interplay among subsystems and their contribution to relative stability of all the studied cross-link model. Finally, basic spectral properties of these complexes including H(8) chemical shifts of all the studied complexes and the VCD (vibrational circular dichroism) spectra of two pairs of GG chelate enantiomers, were provided in order to define the structure of the most possible duplex bearing novel trans platinum drug lesions. 相似文献
204.
Ying-Tong Di Hong-Ping He Zhi-Zhi Du Xian-Wen Yang Xiao-Jiang Hao 《Tetrahedron letters》2006,47(30):5329-5331
A novel Daphniphyllum alkaloid with a rearranged fused-hexacyclic ring system, calycilactone A, was isolated from the leaves of Daphniphyllum calycillum (Daphniphyllaceae), and the structure and relative stereochemistry of the new compound were elucidated on the basis of spectroscopic data. 相似文献
205.
206.
Xiao Ying Xu Feng Cheng Jian Hua Shen Xiao Min Luo Li Li Chen Li Duo Yue Yi Du Fei Ye Shan Hao Jiang Da Yuan Zhu Hua Liang Jiang Kai Xian Chen 《International journal of quantum chemistry》2003,93(6):405-410
Docking simulation of 18 agonists with the ligand binding pocket (LBP) of PPARγ has been performed. The binding conformations and binding affinities of these agonists were obtained by use of the flexible docking protocol FlexX. Test compound calculations indicated that FlexX can reproduce the binding conformation of the crystal structure (root mean square deviation = 1.43 Å); moreover, the predicted binding affinities correlate well with the activities of these agonists. The interaction model and pharmacophore of PPARγ agonists were derived and the difference in biologic activities of these agonists can be well explained. The PPARγ agonists must have both polar head and the hydrophobic tail, which form hydrogen bonds and hydrophobic contacts with hydrophilic and hydrophobic regions of the LBP of PPARγ, respectively. In addition, a suitable linker is also necessary. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 93: 405–410, 2003 相似文献
207.
208.
LBL分子沉积法制备葡萄糖氧化酶电极 总被引:1,自引:0,他引:1
采用以静电力为主的逐层分子交替沉积技术制备葡萄糖氧化酶(GOD)电极.通过带有正电荷的聚二甲基二烯丙基铵盐酸盐(PDDA)和带有负电荷的GOD交替沉积在修饰有3-巯基-1-丙基磺酸钠(MPS)的金电极表面.以甲酸二茂铁为电子媒介体,用循环伏安法检测GOD电极对葡萄糖的响应.结果表明,当GOD电极组装层数小于4时,电流响应随着层数的增加而增大,超过4层时电流响应减小.其中4层GOD修饰电极的线性范围为0.55~6.63 mmol•L-1,当pH为7.0时,响应最大.同时电极的检测重现性能良好,相对标准偏差为2.4%. 相似文献
209.
210.
X射线荧光光谱法在稀土元素分析中的应用 总被引:6,自引:0,他引:6
本文研究了X射线荧光光谱在混合稀土氧化物和高纯稀土氧化物分析中的应用,并探讨了在常量分析中影响分析准确度和精密度的主要因素;样品及标样制备,基体效应校正方法在痕量分析中降低检测限的方法,选择最佳测量条件,降低背景,与分离富集手段相结合,取得满意的结果。 相似文献