全文获取类型
收费全文 | 824篇 |
免费 | 64篇 |
国内免费 | 119篇 |
专业分类
化学 | 680篇 |
晶体学 | 8篇 |
力学 | 48篇 |
综合类 | 10篇 |
数学 | 87篇 |
物理学 | 174篇 |
出版年
2024年 | 2篇 |
2023年 | 18篇 |
2022年 | 43篇 |
2021年 | 41篇 |
2020年 | 44篇 |
2019年 | 29篇 |
2018年 | 35篇 |
2017年 | 23篇 |
2016年 | 40篇 |
2015年 | 49篇 |
2014年 | 39篇 |
2013年 | 64篇 |
2012年 | 73篇 |
2011年 | 82篇 |
2010年 | 54篇 |
2009年 | 48篇 |
2008年 | 47篇 |
2007年 | 42篇 |
2006年 | 41篇 |
2005年 | 32篇 |
2004年 | 13篇 |
2003年 | 18篇 |
2002年 | 11篇 |
2001年 | 11篇 |
2000年 | 20篇 |
1999年 | 17篇 |
1998年 | 17篇 |
1997年 | 13篇 |
1996年 | 8篇 |
1995年 | 8篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 7篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
排序方式: 共有1007条查询结果,搜索用时 15 毫秒
91.
采用水热法制备了一种新型稀土配位聚合物[Dy(3-PA)3(H2O)]n(3-PA=3-吡啶丙烯酸)(1),并通过X射线单晶衍射结构分析、元素分析、红外光谱、热重分析对配合物1进行了结构表征.结构分析表明,标题配合物属于三斜晶系,Pī空间群,晶胞参数为:a=0.617 16(5)nm,b=1.270 45(11)nm,c=1.564 03(13)nm,α=111.557 0(10)°,β=90.307 0(10)°,γ=95.342 0(10)°,V=1.134 54(16)nm3,Z=2.金属离子Dy(III)通过配体3-AP羧基的桥联作用,链接成为一维双螺旋链状配位聚合物. 相似文献
92.
建立黑顺片中6种酯型生物碱含量的高效液相测定方法。采用岛津C18色谱柱(250 mm×4.6 mm,5μm),以乙腈–四氢呋喃(体积比为25∶15)为流动相A,以0.1 mol/L乙酸铵溶液(每1 000 m L加冰乙酸0.5 m L)为流动相B梯度洗脱,流量为1.0 ml/min,检测波长为235 nm,柱温为35℃。苯甲酰新乌头原碱、苯甲酰乌头原碱、苯甲酰次乌头原碱、新乌头碱、次乌头碱、乌头碱进样量分别在0.222~4.430,0.060~1.119,0.144~2.878,0.015~0.297,0.025~0.496,0.011~0.229μg范围内与色谱峰面积线性呈良好的线性关系,相关系数r均大于0.999 5,检出限分别为2.10,2.70,2.20,2.60,1.60,3.10 ng,样品在12 h内稳定。苯甲酰新乌头原碱、苯甲酰乌头原碱、苯甲酰次乌头原碱、新乌头碱、次乌头碱、乌头碱的加标回收率分别为98.7%~102.2%,98.6%~102.3%,99.0%~101.9%,102.0%~97.3%,102.1%~98.3%,95.7%~103.5%,测定结果的相对标准偏差分别为2.5%,2.5%,2.2%,2.3%,2.2%,1.7%(n=6)。该方法简便,测定结果准确、可靠,可为黑顺片的质量评价和质量控制提供参考。 相似文献
93.
Xiaobo Duan Yingxing Wang Weipei Feng Yaxing Yang Hongyan Li Shenghui Li Xiaobing Yang Jinchao Zhang Shuxiang Wang Guoqiang Zhou Chuanqi Zhou 《Research on Chemical Intermediates》2017,43(1):271-281
A series of novel N-arylpyrazole derivatives (4a–4l) bearing the sulfonamide moiety were synthesized by the condensation reaction of 1,3-dicarbonyl compounds with 4-hydrazinylbenzenesulfonamide. The structures of the obtained compounds were established on the basis of elemental (C, H, and N) and spectral analysis (1H NMR, 13C NMR, ESIMS, and FT-IR). These compounds were tested for their in vitro cytotoxic activity against three human tumor cell lines: MCF-7, Hela, and A549. The results showed that most of the obtained compounds exhibited promising cytotoxicity against the tested cell lines with low IC50 values. The pyrazole derivative 4k, bearing two methoxy groups on the 3-position and 4-position of the phenyl ring, was the most effective one. Its inhibition of cell growth of MCF-7 cells was better than that of celecoxib and cisplatin. 相似文献
94.
通过简单易行的曼尼希(Mannich)反应,合成了一种[N_2O_2]型配体,在少量三乙胺存在条件下,成功实现了与高氯酸镍配位,得到了镍金属配合物。通过核磁共振氢谱、高分辨质谱等手段对配体和配合物进行了表征。该化合物在水中具有一定的溶解度,并在中性磷酸缓冲溶液中显示出良好的电化学催化产氢活性。 相似文献
95.
96.
Enhanced indirect fluorescence detection with in-column optical-fiber LED-induced fluorescence (LED-IF) detection has been developed for the simultaneous separation and determination of p-nitrophenol, 2,4-dinitrophenol and trinitrophenol. The instrumental set-up is simple, cost-effective and the detection method is stable. Different experimental parameters have been studied. The optimum conditions were determined as: running buffer (pH 9.1) composed of 10 mM borate, 80 mM sodium dodecylsulfate and 0.18 μM fluorescein (as a background reagent); applied voltage of 15 kV; working temperature of 25.0 °C. The limits of detection (S/N = 3) were 11, 18 and 16 μM for p-nitrophenol, 2,4-dinitrophenol and trinitrophenol, respectively. The nitrophenols were completely separated in 13 min and the number of theoretical plates for p-nitrophenol, 2,4-dinitrophenol and trinitrophenol were 8.1 × 10(6), 6.5 × 10(6) and 8.4 × 10(6), respectively. The RSDs (n = 6) for the migration time and the peak area were better than 0.85 and 0.91%, respectively. Our proposed method possesses the advantages of rapidness and good separation efficiency. 相似文献
97.
Keying Zhang Na Zhang Li Zhang Jigui Xu Hongyan Wang Cong Wang Tao Geng 《Mikrochimica acta》2011,173(1-2):135-141
A sensitive amperometric sensor for hydrogen peroxide (HP) was constructed that is based on a glassy carbon electrode (GCE) modified with silver nanoparticles on poly(alizarin yellow R). The polymer was electropolymerized onto the surface of the GCE by cyclic voltammetry (CV), and the AgNPs were then electrodeposited onto its surface. The electrode was characterized by scanning electron microscopy and CV, and used for amperometric determination of HP. The electrode exhibits a favorable catalytic activity towards the reduction of HP, with a linear response range from 1.0???M to 450???M and a detection limit of 0.32???M. The sensor also displays high selectivity, excellent reproducibility, and good long-term stability. Figure
Schematic representation of the preparation process of the HP sensor and catalytic activity towards HP 相似文献
98.
Highly ordered titanium dioxide (TiO2) nanotubes film was successfully synthesized via anodic oxidation of a Ti foil in an ammonium fluoride-based ethylene glycol solution. The electrogenerated chemiluminescence (ECL) behavior of the resulting TiO2 nanotubes film was subsequently studied. Strong ECL emission was observed at −1.40 V (vs. Ag/AgCl) and the ECL spectrum displayed three emission peaks which were bathochromatically shifted by ca. 140 nm as compared to its corresponding photoluminescence (PL) emission peaks, indicating that the surface state plays an important role in the emission process. The ECL emission can also occur in a deareated solution attributing to the surface adsorbed O2 molecules. The ECL emission intensity was quenched by dopamine and greatly enhanced in the presence of dissolved O2 and H2O2, making it possible to detect these analytes. The TiO2 nanotubes film has been successfully applied to determine the dissolved O2 content in river and pond water samples, the H2O2 concentration in commercial disinfectant samples and the dopamine concentration in commercial dopamine injections with satisfactory results. The plausible ECL mechanisms of TiO2 nanotubes film in aqueous solution are discussed. 相似文献
99.
Gold nanoparticles-poly(luminol) (Plu-AuNPs) hybrid film and multi-walled carbon nanotubes with incorporated β-cyclodextrin modified glassy carbon electrode (β-CD-MWCNTs/Plu-AuNPs/GCE) was successfully prepared for simultaneous determination of dopamine (DA) and uric acid (UA). The surface of the modified electrode has been characterized by X-ray photo-electron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDS), field-emission scanning electron microscope (SEM) and transmission electron microscope (TEM). Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV) have been used to investigate the β-CD-MWCNTs/Plu-AuNPs composite film. Gold nanoparticles anchored into poly(luminol) film exhibited catalytic activity for DA. MWCNTs with incorporated β-CD can greatly promote the direct electron transfer. In 0.10 M phosphate buffer solution (PBS, pH 7.0), the DPV response of the β-CD-MWCNTs/Plu-AuNPs/GCE sensor to DA is about 8-fold as compared with the Plu-AuNPs/GCE sensor, and the detection limit for DA is about one order of magnitude lower than the Plu-AuNPs/GCE sensor. The steady-state current response increases linearly with DA concentration from 1.0 × 10−6 to 5.6 × 10−5 M with a low detection limit (S/N = 3) of 1.9 × 10−7 M. Moreover, the interferences of ascorbic acid (AA) and uric acid (UA) are effectively diminished. The applicability of the prepared electrode has been demonstrated by measuring DA contents in dopamine hydrochloride injection. 相似文献
100.