全文获取类型
收费全文 | 27093篇 |
免费 | 2970篇 |
国内免费 | 2848篇 |
专业分类
化学 | 20944篇 |
晶体学 | 322篇 |
力学 | 926篇 |
综合类 | 128篇 |
数学 | 3274篇 |
物理学 | 7317篇 |
出版年
2024年 | 64篇 |
2023年 | 424篇 |
2022年 | 854篇 |
2021年 | 1018篇 |
2020年 | 876篇 |
2019年 | 884篇 |
2018年 | 727篇 |
2017年 | 684篇 |
2016年 | 1160篇 |
2015年 | 1179篇 |
2014年 | 1301篇 |
2013年 | 2085篇 |
2012年 | 2350篇 |
2011年 | 2408篇 |
2010年 | 1486篇 |
2009年 | 1743篇 |
2008年 | 1759篇 |
2007年 | 1588篇 |
2006年 | 1391篇 |
2005年 | 1308篇 |
2004年 | 1474篇 |
2003年 | 1044篇 |
2002年 | 969篇 |
2001年 | 528篇 |
2000年 | 451篇 |
1999年 | 343篇 |
1998年 | 309篇 |
1997年 | 258篇 |
1996年 | 256篇 |
1995年 | 208篇 |
1994年 | 156篇 |
1993年 | 182篇 |
1992年 | 151篇 |
1991年 | 97篇 |
1990年 | 99篇 |
1989年 | 85篇 |
1988年 | 81篇 |
1987年 | 73篇 |
1986年 | 84篇 |
1985年 | 105篇 |
1984年 | 101篇 |
1983年 | 70篇 |
1982年 | 60篇 |
1981年 | 61篇 |
1980年 | 54篇 |
1979年 | 35篇 |
1978年 | 29篇 |
1977年 | 36篇 |
1976年 | 28篇 |
1974年 | 28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.
93.
用ATRP法构筑核壳型梯度极性的多羟基多臂星状超支化聚合物及聚合物刷——双层聚合物刷的合成与表征 总被引:3,自引:0,他引:3
设计并通过原子转移自由基聚合方法 (ATRP)合成了核壳型多羟基多臂星状超支化聚合物刷 .以 2 溴异丁基酰溴封端的超支化聚 (3 乙基 3 羟甲基氧杂环丁烷 ) (HP Br)作为大分子引发剂 ,采用Cu(I)Br和N ,N ,N′ ,N′ ,N″ 五甲基二乙基三胺 (PMDETA)催化体系 ,在丁酮与丙醇的混和溶液中 ,通过甲基丙烯酸羟乙酯(HEMA)的ATRP溶液聚合 ,得到了一系列含有大量羟基的多臂星状超支化聚合物刷 (HP g PHEMA) ,并考察了其羟基的活性 ,发现羟基还可以与苯甲酰氯发生反应 .产物的结构和热性能用1 H NMR、FTIR、GPC、TGA、DSC等进行了表征和测试 . 相似文献
94.
95.
Zhengping Hao Lidun An Junling Zhou Hongli Wang 《Reaction Kinetics and Catalysis Letters》1996,59(2):295-300
Supported gold catalyst for eliminating hydrogen from CO2 feed gas in the production of urea is found to be superior to other industrial catalysts (e.g. Pt/Al2O3 and PdPt/Al2O3) in catalytic activity and resistance to sulfur poisoning. 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.
ICP激发光源以其独特的功能使ICP/AES技术在稀土分析中的应用日益广泛,在一定程度上取代了经典的直流电弧光谱法,但应指出,由于常规雾化器的低雾化效率(≤5%)和试样的高倍稀释,ICP/AES技术的实际检测能力的改善并不明显,本文用ICP光谱法测定了 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.