全文获取类型
收费全文 | 28543篇 |
免费 | 5460篇 |
国内免费 | 4551篇 |
专业分类
化学 | 21014篇 |
晶体学 | 456篇 |
力学 | 1822篇 |
综合类 | 402篇 |
数学 | 3337篇 |
物理学 | 11523篇 |
出版年
2024年 | 43篇 |
2023年 | 470篇 |
2022年 | 677篇 |
2021年 | 950篇 |
2020年 | 1225篇 |
2019年 | 1165篇 |
2018年 | 1034篇 |
2017年 | 1003篇 |
2016年 | 1360篇 |
2015年 | 1469篇 |
2014年 | 1842篇 |
2013年 | 2247篇 |
2012年 | 2588篇 |
2011年 | 2787篇 |
2010年 | 2075篇 |
2009年 | 2056篇 |
2008年 | 2236篇 |
2007年 | 1989篇 |
2006年 | 1845篇 |
2005年 | 1510篇 |
2004年 | 1232篇 |
2003年 | 945篇 |
2002年 | 958篇 |
2001年 | 837篇 |
2000年 | 631篇 |
1999年 | 544篇 |
1998年 | 409篇 |
1997年 | 413篇 |
1996年 | 350篇 |
1995年 | 290篇 |
1994年 | 256篇 |
1993年 | 199篇 |
1992年 | 127篇 |
1991年 | 149篇 |
1990年 | 126篇 |
1989年 | 87篇 |
1988年 | 83篇 |
1987年 | 74篇 |
1986年 | 55篇 |
1985年 | 44篇 |
1984年 | 33篇 |
1983年 | 31篇 |
1982年 | 29篇 |
1981年 | 18篇 |
1980年 | 16篇 |
1979年 | 7篇 |
1976年 | 6篇 |
1975年 | 8篇 |
1959年 | 5篇 |
1957年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
991.
Quantitation of agmatine by liquid chromatography with laser-induced fluorescence detection 总被引:3,自引:0,他引:3
Shulin Zhao Yangzheng Feng Michael H. LeBlanc John E. Piletz Yi-Ming Liu 《Analytica chimica acta》2002,470(2):155-161
A high performance liquid chromatography (HPLC) method is described for the determination of agmatine, an endogenous neuromodulator. The method involves pre-column derivatization of the sample with a fluorescent tagging reagent, 7-fluoro-4-nitrobenzoxadiazole (NBD-F). The resulting agmatine derivative is stable and can be readily extracted into ethyl acetate at pH 8.5. The extraction enhances the quantification of low level agmatine because it eliminates chromatographic peaks caused by endogenous amino acids. The HPLC separation is carried out on a C8 reversed phase column and completed in less than 10 min. With laser-induced fluorescence (LIF) detection, the detection limit is 5×10−9 M agmatine. Method precision (coefficient of variation) is 5% for agmatine in human plasma at the sub-μM level. This method has been validated by determination of agmatine in biological samples including human plasma and rat brain and stomach tissues. 相似文献
992.
Adrenaline was found to inhibit strongly the electrochemiluminescence (ECL) from the Ru(bpy)32+/tripropylamine system when a working Pt electrode was maintained at 1.05 V (versus Ag/AgCl) in pH 8.0 phosphate buffer. On this basis, a flow injection (FI) procedure with inhibited electrochemiluminescence detection has been developed for determination of adrenaline. The method exhibited a good reproducibility, sensitivity, and stability with a detection limit (signal-to-noise ratio = 3) of 7.0×10−9 mol l−1 and dynamic concentration range of 2×10−8 to 1×10−4 mol l−1. The relative standard deviation was 2.2% for 1.0×10−6 mol l−1 adrenaline (n=11). The method was successfully applied to the determination of adrenaline in pharmaceutical samples. Moreover, ECL emission spectra, UV-Vis absorption spectra and cyclic voltammograms of Ru(bpy)32+/tripropylamine/adrenaline were studied. The inhibition mechanism has been proposed as the interaction of electrogenerated Ru(bpy)32+* and the o-benzoquinone derivatives, adrenochrome and adrenalinequinone, at the electrode surface. 相似文献
993.
Filter-based microfluidic device as a platform for immunofluorescent assay of microbial cells 总被引:5,自引:0,他引:5
A filter-based microfluidic device was combined with immunofluorescent labeling as a platform to rapidly detect microbial cells. The coin-sized device consisted of micro-chambers, micro-channels and filter weirs (gap = 1-2 microm), and was demonstrated to effectively trap and concentrate microbial cells (i.e., Cryptosporidium parvum and Giardia lamblia), which were larger in size than the weir gap. After sample injection, a staining solution containing fluorescently-labeled antibodies was continuously provided into the device (flow rate = 20 microl min(-1)) to flush the microbial cells toward the weirs and to accelerate the fluorescent labeling reaction. Using a staining solution that was 10 to 100 times more dilute than the recommended concentration used in a conventional glass method, those target cells with a fluorescent signal-to-noise ratio of 12 could be microscopically observed at single-cell level within 2 to 5 min prior to secondary washing. 相似文献
994.
995.
996.
997.
998.
999.
1000.
Shao-Chen Yang Qihuang Gong Zongju Xia Y. H. Zou Y. Q. Wu D. Qiang Y. L. Sun Z. N. Gu 《Applied physics. B, Lasers and optics》1992,55(1):51-53
The nonlinear third-order optical susceptibility of C70 in a toluene solution is measured for the first time by the method of degenerate four-wave mixing using 10 ns laser pulses at 1.06 m. The third-order susceptibility X
in
(3)
is 5.6×10–12 esu for a C70 toluene solution at a concentration of 0.476 g/l. The correspondent magnitude of the hyperpolarizability 1111 of the C70 molecule is 1.2×10–30 esu which is in a good agreement with the prediction given by the model of a free electron in a spherical box. 相似文献