全文获取类型
收费全文 | 14741篇 |
免费 | 2795篇 |
国内免费 | 4663篇 |
专业分类
化学 | 11352篇 |
晶体学 | 522篇 |
力学 | 916篇 |
综合类 | 464篇 |
数学 | 2163篇 |
物理学 | 6782篇 |
出版年
2024年 | 29篇 |
2023年 | 198篇 |
2022年 | 512篇 |
2021年 | 506篇 |
2020年 | 623篇 |
2019年 | 566篇 |
2018年 | 543篇 |
2017年 | 716篇 |
2016年 | 650篇 |
2015年 | 748篇 |
2014年 | 963篇 |
2013年 | 1267篇 |
2012年 | 1242篇 |
2011年 | 1395篇 |
2010年 | 1161篇 |
2009年 | 1267篇 |
2008年 | 1368篇 |
2007年 | 1142篇 |
2006年 | 1135篇 |
2005年 | 928篇 |
2004年 | 725篇 |
2003年 | 656篇 |
2002年 | 680篇 |
2001年 | 623篇 |
2000年 | 623篇 |
1999年 | 392篇 |
1998年 | 192篇 |
1997年 | 141篇 |
1996年 | 170篇 |
1995年 | 126篇 |
1994年 | 153篇 |
1993年 | 123篇 |
1992年 | 97篇 |
1991年 | 74篇 |
1990年 | 76篇 |
1989年 | 61篇 |
1988年 | 54篇 |
1987年 | 43篇 |
1986年 | 47篇 |
1985年 | 25篇 |
1984年 | 28篇 |
1983年 | 27篇 |
1982年 | 20篇 |
1981年 | 21篇 |
1980年 | 12篇 |
1979年 | 13篇 |
1978年 | 7篇 |
1975年 | 4篇 |
1959年 | 5篇 |
1957年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
161.
ZHANG Wei-wei CHEN Yu-chun LUO Zhao-feng WANG Ju-ying MA De-yi 《高等学校化学研究》2007,23(4):404-407
In this study, surface plasmon resonance (SPR) for monitoring 17β-eatradiol (E2) was developed. The small molecule E2 was immobilized on a CM5 sensor chip for an indirect competitive immunoassay to detect E2. The SPR response bahed on the antigen-antibody reaction was measured by injecting the sample solution into the flow system. The limitation of detection was 0.445 μg/L. The developed SPE-SPR system was applied to analyze the seawater samples. Recovery of E2 was 91.6%-93. 1%. Relative standard deviations(RSD) for the E2 assay were between 10.9%-15.1% (n = 3). The range of determination of E2 samples from the sewage in the coastal marine environ-ment was between ND(lower than detection limit) and ca. 11.78 ng/L. 相似文献
163.
Supermolecular compounds of glycine monosubstituted heteropolytungstates isomer with Keggin structure βi-K6-n(HGly)n[SiW11M(H2O)O39]·xH2O (M=Co2+, Ni2+; βi=β2, β3) were synthesized and characterized by means of elementary analysis, IR, UV, TG-DTA, X-ray diffraction, polarography and CV. The results indicate that glycin combines the electrostatic effect with heteropolytungstates isomer. The heteropoly anion still remains its Keggin structure in supermolecular compounds. The electrochemical behavior of the compound in 1 mol·L-1 HAc-NaAc shows that two redox waves correspond to two two-electron processes attributing to the reduction of [SiW11Co(H2O)O39]6-. Steady-state fluorescence spectrum shows two intenser fluorescence emission peaks in 447 nm and 486 nm appeared after the supermolecular compound being excited by the excitation wavelength in 274 nm. 相似文献
164.
DongJunWANG QunLUO DanDanJIA XiaoDongLI XinQiouWANG YongHuang ZhenZHEN XinHouLIU 《中国化学快报》2003,14(12):1306-1308
The hydrolysis of tetraethoxysilane (TEOS) occurred on the surface of poly(methyl methacrylate) (PMMA) microshperes immediately after these microshperes were prepared in TEOS. Micron-sized hollow SiO2 spheres were obtained by calcination of the coated PMMA microshperes. It was found that the final hollow spheres were constituted by small SiO2 particles. 相似文献
165.
166.
MA En CHEN Da-Qin HU Zhong-Jian LIU Feng HUANG Zi-Xiang BAO Feng WANG Yuan-Sheng ② 《结构化学》2007,26(3):303-308
The distribution characteristics of Er3+ ions doped in the oxyfluoride glass ceramics containing LaF3 nanocrystals heat-treated at 650 ℃ for different durations were investigated. The results of the integral absorption cross-section analysis demonstrated that the partition fraction of Er3+ in LaF3 nanocrystals increases with prolonging of heating time. The anomalous phenomena of Er3+ emissions in the up-and the down-conversion fluorescence spectra are well explained based on the calculated results. 相似文献
167.
A new fluorescent compound based on calix[4] arene skeleton was synthesized.Its complexation ability with transition metal ions,such as Fe^3 ,Co^2 ,Ni^2 ,Cu^2 ,Zn^2 and Ag^ ,Was investigated by UV-vis and fluorescent spectra. 相似文献
168.
离子色谱法同时测定水中六种阳离子 总被引:3,自引:0,他引:3
研究了用抑制电导离子色谱法一次进样同时测定水中Li^ ,Na^ , NH4^ ,Mg^2 ,Ca^2 的色谱法条件,相对标准偏差小于0.5%,加标回收率在97.5%-104.0%。在水质分析中运用t检验法,比较了用钙、镁离子浓度计算和传统方法测定的总硬度之间是否存在显著性差异。 相似文献
169.
Synthesis and Characterization of Novel Orange-emitting Iridium(Ⅲ) Complexes with Diphenylquinoline Ligands Containing Fluorinated Substituent 总被引:1,自引:0,他引:1
Xiao Wei ZHANG Chu Luo YANG Zhong An LI Lin Na ZHU Jin Gui QIN Jia GAO Dong Ge MA 《中国化学快报》2006,17(3):411-414
Three new cyclometalated iridium(m) complexes based on ligands of diphenylquinoline with fluorinated subsfituents were prepared, and characterized by elemental analysis (EA), ^1H NMR, and mass spectroscopy (MS). The photophysical and electrophosphorescent properties of the complexes were briefly discussed. 相似文献
170.