全文获取类型
收费全文 | 25448篇 |
免费 | 1118篇 |
国内免费 | 1444篇 |
专业分类
化学 | 19040篇 |
晶体学 | 213篇 |
力学 | 649篇 |
综合类 | 10篇 |
数学 | 3470篇 |
物理学 | 4628篇 |
出版年
2023年 | 180篇 |
2022年 | 470篇 |
2021年 | 555篇 |
2020年 | 438篇 |
2019年 | 473篇 |
2018年 | 448篇 |
2017年 | 413篇 |
2016年 | 920篇 |
2015年 | 740篇 |
2014年 | 838篇 |
2013年 | 1825篇 |
2012年 | 1914篇 |
2011年 | 2078篇 |
2010年 | 1167篇 |
2009年 | 1356篇 |
2008年 | 1575篇 |
2007年 | 1556篇 |
2006年 | 1350篇 |
2005年 | 1361篇 |
2004年 | 1525篇 |
2003年 | 1153篇 |
2002年 | 1030篇 |
2001年 | 482篇 |
2000年 | 409篇 |
1999年 | 318篇 |
1998年 | 276篇 |
1997年 | 238篇 |
1996年 | 283篇 |
1995年 | 234篇 |
1994年 | 169篇 |
1993年 | 201篇 |
1992年 | 167篇 |
1991年 | 113篇 |
1990年 | 109篇 |
1989年 | 97篇 |
1988年 | 85篇 |
1987年 | 82篇 |
1986年 | 76篇 |
1985年 | 143篇 |
1984年 | 131篇 |
1983年 | 83篇 |
1982年 | 108篇 |
1981年 | 102篇 |
1980年 | 101篇 |
1979年 | 73篇 |
1978年 | 61篇 |
1977年 | 65篇 |
1976年 | 70篇 |
1975年 | 63篇 |
1974年 | 53篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
I. B. Plećaš A. D. Perić S. D. Glodić A. M. Kostadinović 《Journal of Radioanalytical and Nuclear Chemistry》1992,166(5):373-381
Results are presented of a series of experimental tests performed to determine the influence of matrix characteristics on the leaching mechanism of copper aluminium oxychloride immobilized into cement matrices. The objective of this research was to investigate the leaching mechanism of copper as a constituent of copper aluminium oxychloride (CAOX). 相似文献
92.
Carbon Nanotubes in Analytical Sciences 总被引:1,自引:0,他引:1
Arben Merkoçi 《Mikrochimica acta》2006,152(3-4):157-174
93.
1,4-Diamino-2-butyne was prepared from 1,4-dichloro-2-butyne via 1,4-diazido-2-butyne. Bis(amino acid) derivatives of 1,4-diamino-2-butyne having the general structure (Boc-Xxx-NHCH2C[triple bond])2 (Xxx = Ala, Phe and Met) were prepared and examined by 1H NMR spectroscopy. Using chemical shift, coupling constant and DMSO titration data it is found that these compounds adopt a C2-symmetric turn conformation featuring two intramolecular hydrogen bonds. 相似文献
94.
95.
A.M. Mota M.L.Simes Gonalves J.P. Farinha J. Buffle 《Colloids and surfaces. A, Physicochemical and engineering aspects》1994,90(2-3):271-278
In order to study the influence of the adsorption of fulvic compounds on voltammetric signals and to understand better the adsorption of these compounds on hydrophobic natural water interfaces, adsorption studies of macromolecules such as poly(ethylene glycol) (HO(CH2CH2O)n) with molecular weight of 8000 were done on the mercury/water interface by a.c. voltammetry at the potential of zero charge. The maximum surface concentration, adsorption equilibrium constant and adsorption rate constant have been determined from the global adsorption mechanism, controlled by two determining steps: diffusion and kinetics of adsorption at the interface. 相似文献
96.
97.
M. Piñeiro-Iglesias M. Miñones-Vázquez E. Vázquez-Blanco S. Muniategui-Lorenzo P. López-Mahía D. Prada-Rodríguez 《Chromatographia》2002,56(7-8):483-488
Summary The aim of this work is to establish the best conditions for concentration and purification steps in the trace analysis of
aliphatic and polycyclic aromatic hydrocarbons (PAH) from atmospheric particulate matter by gas chromatography-flame ionisation
detection (GC-FID) and high performance liquid chromatography with ultraviolet and fluorescence detection (HPLC-UV-FL). The
best results for the more volatile compound were obtained with a combination of rotary evaporation and a stream of nitrogen
(near to 100% for aliphatic hydrocarbons and from 70 to 105% for PAH). Two types of solid phase extraction (SPE)cartridges
(Supelclean
tm
LC-Silica SPE tubes and Sep-Pak? Plus silica cartridges) and glass column were examined for the purification and fractionation step. Blank chromatograms of
both types of cartridges analysed by GC-FID made this study difficult, because a PSS (programmed split-splitless) injector
was employed thereby increasing the sensitivity. This problem was not observed in the HPLC-UV-FL blank chromatograms of these
cartridges. Glass columns filled with silica and alumina were chosen because no interference was found in the GC-FID blank
chromatograms and the best recoveries in the fractionation of both aliphatic hydrocarbons and PAH were achieved. This is especially
important when aliphatic hydrocarbons concentrations are lower than 1 μg mL−1. Finally, the selected conditions were applied to the analysis of hydrocarbons in real atmospheric particulate samples. 相似文献
98.
基于PuH_2分子基态(X~7A_1)的分析势能函数,用准经典的Monte-Carlo轨线法 对Pu(~7Fg)+H_2(X~1∑_g~+,0,0)的分子反应动力学过程进行了计算。结果表明 :Pu(~7F_g)与H_2(X~1∑_g~+,0,0)碰撞是弹性碰撞。 相似文献
99.
J. J. LaBrecque Z. A. De Benzo E. Marcano C. A. Peña 《Journal of Radioanalytical and Nuclear Chemistry》1984,84(2):407-413
The comparison of an ambient temperature mercuric iodide spectrometer (HgI2) with a conventional cooled Si(Li) spectrometer is presented for the determination of niobium in Venezuelan laterites in the laboratory. The energy resolution of the HgI2 spectrometer was only about 590 eV (FWHM) at 5.9 keV compared to about 150 eV for the conventional Si(Li) spectrometer. The efficiency was about 5 times lower in the region of the NbK
peak as compared to the Si(Li) detector. Even though its energy resolution and efficiency is much poorer than the conventional Si(Li), the results it produced for the determination of niobium were acceptable for use in the exploration and exploitation of a niobium-rich deposit such as Cerro Impacto, Estado Bolívar, Venezuela. 相似文献
100.