全文获取类型
收费全文 | 5177篇 |
免费 | 243篇 |
国内免费 | 2篇 |
专业分类
化学 | 3344篇 |
晶体学 | 40篇 |
力学 | 129篇 |
数学 | 1013篇 |
物理学 | 896篇 |
出版年
2023年 | 35篇 |
2022年 | 42篇 |
2021年 | 63篇 |
2020年 | 113篇 |
2019年 | 94篇 |
2018年 | 136篇 |
2017年 | 109篇 |
2016年 | 206篇 |
2015年 | 176篇 |
2014年 | 187篇 |
2013年 | 365篇 |
2012年 | 383篇 |
2011年 | 956篇 |
2010年 | 208篇 |
2009年 | 198篇 |
2008年 | 296篇 |
2007年 | 254篇 |
2006年 | 253篇 |
2005年 | 222篇 |
2004年 | 174篇 |
2003年 | 144篇 |
2002年 | 148篇 |
2001年 | 70篇 |
2000年 | 62篇 |
1999年 | 42篇 |
1998年 | 39篇 |
1997年 | 33篇 |
1996年 | 54篇 |
1995年 | 28篇 |
1994年 | 38篇 |
1993年 | 29篇 |
1992年 | 30篇 |
1991年 | 18篇 |
1990年 | 22篇 |
1989年 | 15篇 |
1988年 | 7篇 |
1987年 | 9篇 |
1986年 | 12篇 |
1985年 | 17篇 |
1984年 | 12篇 |
1983年 | 9篇 |
1982年 | 11篇 |
1981年 | 10篇 |
1980年 | 9篇 |
1979年 | 7篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1975年 | 8篇 |
1973年 | 8篇 |
1969年 | 6篇 |
排序方式: 共有5422条查询结果,搜索用时 15 毫秒
71.
72.
Sérgio L. C. Ferreira Neyla M. L. Araújo Adriana B. Santos Alailson F. Dantas A. C. Spinola Costa 《Mikrochimica acta》1995,118(1-2):123-129
TAN reacts with zinc(II) forming a red complex with composition 1:2 Zn(II)-TAN and absorption maximum at 582 nm. Zinc can be determined with this reagent in the presence of Triton X-100, in the pH range 6.20-8.00 with a molar absorptivity of 4.5×104 l/mol/cm Beer's Law was obeyed up to least 1.55 g/ml. Copper interference was eliminated with a mixture of thiosulfate and ascorbic acid and nickel separated by precipitation with dimethylglyoxime. The proposed method was used for zinc determination in several copper-base alloys and the results of analysis in comparison with certified values indicated that the procedure was accurate and precise. A derivative procedure is also proposed, allowing zinc determination with high sensitivity (5-400 ng/ml). 相似文献
73.
74.
I. Orúe P. Gorría F. Plazaola M. L. Fernández-Gubieda J. M. Barandiarán 《Hyperfine Interactions》1994,94(1):2199-2205
Mössbauer measurements have been performed on amorphous and nanocrystalline alloy ribbons of nominal composition Fe86Zr7Cu1B6. The nanocrystalline samples were obtained by annealing the as-quenched alloy at different temperatures in the range between 650 and 870 K. Mössbauer spectra of the as-quenched amorphous sample have been recorded at 77 K, room temperature and above the Curie temperature (330 K) at 360 K. We have also performed Mössbauer measurements at room temperature in the nanocrystalline alloys to characterize the phases that appear after the annealing and their relative concentration. The as-quenched sample spectra reveal the existence of two inequivalent sites for Fe. Such a feature is also observed in the remaining amorphous phase of the annealed samples. In the first steps of crystallization, -Fe precipitates and its concentration increases with the annealing temperature. The experimental results suggest that the composition of the whole amorphous phase does not suffer large changes during crystallization. 相似文献
75.
76.
77.
Mn2(CO)10 was photolysed in the gas phase by the XeCl-excimer laser with fluence in the range 25–300 mJ/cm2 and a dye laser. The UV/VIS emission of the products was probed on a nanosecond time scale. The emission from excited states of metal atoms was detected only. The Mn atoms are predominantly formed in their ground statea
6
S
2 1/2. The absorption of one photon and the subsequent relaxation process leads to the formation ofz
6
P
J
0
(J = 11/2, 21/2, 31/2) states and emission of photons at a wavelength of 403 nm. The formation of the excited statese
8
D
5 1/2,z
6
F
4 1/2
0
ande
6
D
4 1/2 and the subsequent emission observed at wavelengths of 357, 383 and 446 nm requires the absorption of two photons by the ground-state Mn atoms. In addition, transition from thea
6
D
j (J = 11/2, 21/2) lower states were observed in the wavelength-resolved Laser-Induced Fluorescence (LIF) spectra. 相似文献
78.
79.
80.
Sample stacking with matrix removal for the determination of paraquat, diquat and difenzoquat in water by capillary electrophoresis 总被引:2,自引:0,他引:2
Conditions for the simultaneous determination of paraquat, diquat and difenzoquat by capillary zone electrophoresis using a stacking technique in a chemically modified capillary have been established. To apply the stacking method with sample matrix removal for the analysis of cations, an anodic electroosmotic flow is mandatory. For quats, 50 mM acetic acid-ammonium acetate (pH 4.0) with 5% (v/v) methanol as electrophoretic buffer and the addition of 0.8 mM cetyltrimethylammonium bromide as wall capillary organic modifier was proposed. Field polarity reversal time was optimised for several sample matrices. Detection was carried out at 220 and 255 nm. Detection limits, based on a signal-to-noise ratio of 3:1, were lower than 15 microg l(-1) for standards in Milli-Q water and two to ten times higher for drinking water samples. Run-to-run and day-to-day reproducibility have been established. The method was successfully applied to the determination of the three herbicides in spiked drinking water. 相似文献