全文获取类型
收费全文 | 203852篇 |
免费 | 1962篇 |
国内免费 | 591篇 |
专业分类
化学 | 102304篇 |
晶体学 | 3340篇 |
力学 | 9287篇 |
综合类 | 5篇 |
数学 | 22470篇 |
物理学 | 68999篇 |
出版年
2021年 | 1653篇 |
2020年 | 1797篇 |
2019年 | 1998篇 |
2018年 | 2699篇 |
2017年 | 2601篇 |
2016年 | 3765篇 |
2015年 | 2304篇 |
2014年 | 3613篇 |
2013年 | 9084篇 |
2012年 | 7239篇 |
2011年 | 8734篇 |
2010年 | 6040篇 |
2009年 | 5908篇 |
2008年 | 7911篇 |
2007年 | 8079篇 |
2006年 | 7722篇 |
2005年 | 6890篇 |
2004年 | 6424篇 |
2003年 | 5650篇 |
2002年 | 5491篇 |
2001年 | 6424篇 |
2000年 | 4931篇 |
1999年 | 3794篇 |
1998年 | 3038篇 |
1997年 | 3045篇 |
1996年 | 2791篇 |
1995年 | 2613篇 |
1994年 | 2462篇 |
1993年 | 2337篇 |
1992年 | 2691篇 |
1991年 | 2671篇 |
1990年 | 2600篇 |
1989年 | 2396篇 |
1988年 | 2449篇 |
1987年 | 2448篇 |
1986年 | 2279篇 |
1985年 | 2960篇 |
1984年 | 3215篇 |
1983年 | 2631篇 |
1982年 | 2801篇 |
1981年 | 2771篇 |
1980年 | 2637篇 |
1979年 | 2727篇 |
1978年 | 2821篇 |
1977年 | 2819篇 |
1976年 | 2886篇 |
1975年 | 2670篇 |
1974年 | 2644篇 |
1973年 | 2776篇 |
1972年 | 1763篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
S. D. Borkute U. H. Nagvekar S. A. Balakrishnan R. S. Mani 《Journal of Radioanalytical and Nuclear Chemistry》1987,119(4):297-302
A novel method to eliminate T3 from gross sera/plasma based on prior treatment with 8-anilino-1-naphthalene sulphonic acid has been standardized. This method is rapid with a minimum loss of protein and uses only small quantities of charcoal. The treated sera have been tested for acceptance in the RIA system for routine assays. 相似文献
972.
973.
SiC films doped with aluminum (Al) were prepared by the rf-magnetron sputtering technique on p-Si substrates with a composite target of a single crystalline SiC containing several Al pieces on the surface. The as-deposited films were annealed in the temperature range of 400-800 °C under nitrogen ambient. The thin films have been characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The results show that the introduction of Al into films hinders crystalline formation process. And with the increase of annealing temperature, more Si particles are formed in the films, which strongly affect the optical absorption properties. The photoluminescence (PL) spectra of the samples show two peaks at 370 nm and 412 nm. The intensities of the PL peaks are evidently improved after Al doped. We attribute the origin of the two PL peaks to a kind of Si-related defect centres. The obtained results are expected to have important applications in modern optoelectronic devices. 相似文献
974.
The Gelfand-Zetlin basis is adapted toSU(N)
q
forq a root of unit. Extra parameters are incorporated in the matrix elements of the generators to obtain all the invariants corresponding to the augmented center. A crucial identity is derived and proved, which guarantees the periodicity of the action of the generators. Full periodicity is relaxed by stages, some raising and lowering operators remaining injective while others become nilpotent with corresponding changes in the dimension of the representation. In the extreme case of highest weight representations. all the raising and lowering operators are nilpotent. As an alternative approach an auxiliary algebra giving all the periodic representations is presented. An explicit solution of this system forN=3, while fully equivalent to the G.-Z. basis, turns out to be much simpler. 相似文献
975.
V. N. Volynets D. I. Slovetskii A. Ya. Strochkov V. N. Trofimov 《Journal of Applied Spectroscopy》1991,54(6):613-619
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 6, pp. 1004–1010, June, 1991. 相似文献
976.
977.
978.
979.
980.
S. M. Arabei D. V. Novik T. A. Pavich K. N. Solov’ev 《Journal of Applied Spectroscopy》2006,73(4):511-521
We have studied the fluorescence and fluorescence excitation spectra at 300 K, 77 K, and 4.2 K for silicate gel matrices colored
with meso-tetrapropylporphin by impregnation of the matrix with a solution of the pigment. Comparison of the data obtained
with the absorption spectra in acidified solutions and analysis of the low-temperature fine-structure vibronic spectra, and
also taking into account data obtained earlier for octaethylporphin in a xerogel showed formation of two cationic forms of
meso-tetrapropylporphin in the gel matrix: the short-wavelength form has a dicationic structure, while the long-wavelength form
has a monocationic structure. We have traced out the correlations of the vibrational structure in the spectra of the dicationic
form with data for the porphin dication, and we have drawn a number of conclusions concerning the normal vibrational modes
that are active in the vibronic fluorescence and absorption spectra of the studied cationic forms. Using the AM1 semiempirical
quantum chemical method, we optimized the geometry of the mesotetrapropylporphin dication: the most stable of the possible
conformers is the dication structure with saddleshaped macrocycle nonplanarity.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 453–461, July–August, 2006. 相似文献