全文获取类型
收费全文 | 10394篇 |
免费 | 1551篇 |
国内免费 | 1401篇 |
专业分类
化学 | 10170篇 |
晶体学 | 82篇 |
力学 | 34篇 |
综合类 | 88篇 |
数学 | 6篇 |
物理学 | 2966篇 |
出版年
2024年 | 20篇 |
2023年 | 99篇 |
2022年 | 244篇 |
2021年 | 407篇 |
2020年 | 503篇 |
2019年 | 494篇 |
2018年 | 361篇 |
2017年 | 402篇 |
2016年 | 585篇 |
2015年 | 561篇 |
2014年 | 594篇 |
2013年 | 982篇 |
2012年 | 822篇 |
2011年 | 634篇 |
2010年 | 625篇 |
2009年 | 667篇 |
2008年 | 659篇 |
2007年 | 693篇 |
2006年 | 628篇 |
2005年 | 541篇 |
2004年 | 477篇 |
2003年 | 397篇 |
2002年 | 318篇 |
2001年 | 185篇 |
2000年 | 208篇 |
1999年 | 159篇 |
1998年 | 166篇 |
1997年 | 159篇 |
1996年 | 106篇 |
1995年 | 142篇 |
1994年 | 96篇 |
1993年 | 99篇 |
1992年 | 74篇 |
1991年 | 65篇 |
1990年 | 43篇 |
1989年 | 29篇 |
1988年 | 28篇 |
1987年 | 30篇 |
1986年 | 9篇 |
1985年 | 8篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 359 毫秒
71.
72.
Multiwalled carbon nanotubes were modified by carboxy groups. Four independent methods for the determination of the degree
of functionalization of the surface were proposed: 13C NMR spectroscopy, thermogravimetry, titrimetry, and fluorimetry. The first two methods show the total content of carboxy
groups in the sample, and the latter two methods give information about the content of the surface groups only.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 291–295, February, 2008. 相似文献
73.
Anomalously high fluorescence spectrum Stokes' shifts of 2(4-pyridyl)-5-(4-methylphenyl)oxazole, 2(4-pyridyl)-5-(4-methoxyphenyl)oxazole, 2(4-pyridyl)-5-(4-N,N-dimethylaminophenyl)oxazole have been found. The fluorescence spectra of the compounds studied are shifted to longer wavelengths as the solvent dielectric constant increases. The dipole moments of these compounds increase by 3–4 times upon excitation. The fluorescence spectra of the compounds investigated are shifted to shorter wavelengths, and the fluorescence quantum yields increase as the temperature decreases. The fluorescence rate constant of 2(4-pyridyl)-5-(4-N,N-dimethylaminophenyl)oxazole changes slightly as the temperature decreases from 293 K (relaxed state) to 114 K (mainly nonrelaxed state). It was concluded that the anomalously high fluorescence Stokes' shift of 2-pyridyl-5-aryloxazole derivatives is caused by solvent orientation relaxation. 相似文献
74.
A.A. Dakhel 《Journal of Physics and Chemistry of Solids》2004,65(11):1765-1771
Thin Eu-In solid solution oxide films (SS) were grown on Si (P) substrates to form MOS devices. The samples were characterised by X-ray fluorescence and X-ray diffraction techniques. The ac-conductance and capacitance of the devices were studied as a function of frequency in the range 500 Hz to 100 kHz, temperature in the range 293-400 K and gate voltage. The investigation established that: (1) the prepared SS exhibit a sudden reversible structural change at about 370 K, (2) the frequency dependence for f>10 kHz of the ac-conductivity and capacitance of the insulator at room temperature is controlled by the ‘corrected barrier hopping’ CBH model, (3) the temperature dependence of the ac-conductance which shows a small activation energy characterises the hopping process of current carriers between equilibrium sites, and (4) the prepared transparent SS have a sufficiently high relative permittivity ?, around 30, which suggests they are promising candidates for high-? dielectric applications. 相似文献
75.
76.
Francesco Michelangeli 《Journal of fluorescence》1991,1(3):203-206
A simple fluorimetric method is presented for measuring calcium uptake and inositol 1,4,5-trisphosphate (InsP3)-induced calcium release in microsomes using Fluo-3. This method is used to investigate the amplitude of calcium release (quantal release) induced by InsP3 from rat cerebellum microsomes. 相似文献
77.
78.
The K-shell X-ray fluorescence cross sections are determined experimentally for 10 elements such as Pb, Hg, Ir, W, Lu, Tm,
Dy, Tb, Gd and Nd at excitation energy of 661.6 keV associated with γ-rays of 137Cs radioisotope. The technique employed involves the measurement of total intensity of fluorescent K X-rays that follow the
photoeffect absorption of a known flux of γ-rays using a well type Nal(Tl) detector. The obtained results are compared with the available theoretical values and other
measured values. 相似文献
79.
本文用激光感生荧光法(LIF)分析了Gd原子亚稳态能级215cm~(-1),533cm~(-1),999cm~(-1)在原子束中的速度分布。由原子束轴线上两不同点上的亚稳态原子速度分布的变化得到了亚稳态原子的寿命。理论分析和实验结果表明这是一种简单、灵敏并且有效的亚稳态原子寿命测量方法。 相似文献