全文获取类型
收费全文 | 2934篇 |
免费 | 88篇 |
国内免费 | 12篇 |
专业分类
化学 | 2296篇 |
晶体学 | 41篇 |
力学 | 25篇 |
数学 | 54篇 |
物理学 | 618篇 |
出版年
2022年 | 13篇 |
2021年 | 24篇 |
2020年 | 21篇 |
2019年 | 31篇 |
2018年 | 16篇 |
2017年 | 23篇 |
2016年 | 49篇 |
2015年 | 45篇 |
2014年 | 53篇 |
2013年 | 102篇 |
2012年 | 156篇 |
2011年 | 182篇 |
2010年 | 93篇 |
2009年 | 100篇 |
2008年 | 162篇 |
2007年 | 175篇 |
2006年 | 151篇 |
2005年 | 168篇 |
2004年 | 146篇 |
2003年 | 132篇 |
2002年 | 104篇 |
2001年 | 104篇 |
2000年 | 76篇 |
1999年 | 69篇 |
1998年 | 35篇 |
1997年 | 39篇 |
1996年 | 36篇 |
1995年 | 30篇 |
1994年 | 26篇 |
1993年 | 27篇 |
1992年 | 41篇 |
1991年 | 31篇 |
1990年 | 38篇 |
1989年 | 27篇 |
1988年 | 18篇 |
1987年 | 35篇 |
1986年 | 19篇 |
1985年 | 34篇 |
1984年 | 36篇 |
1983年 | 20篇 |
1982年 | 36篇 |
1981年 | 32篇 |
1980年 | 22篇 |
1979年 | 43篇 |
1978年 | 27篇 |
1977年 | 20篇 |
1976年 | 15篇 |
1975年 | 18篇 |
1974年 | 19篇 |
1973年 | 15篇 |
排序方式: 共有3034条查询结果,搜索用时 15 毫秒
221.
222.
Single crystals of 6H-SiC were epitaxially grown on 6H-SiC substrates in the temperature range of 1500 to 1750°C with gas composition: H2 ≈ 1 l/min, SiCl4 ≈ 1 ml/min, C3H8 ≈ 0.05 ml/min. The grown layers were transparent and mirror-like. The morphology of the grown layer was strongly influenced by the polarity of the substrate surface. Aggregates of trapezoidal crystals were observed on the (000)C surface and a mosaic pattern was observed on the (0001)Si surface. By observing the initial stage of the crystal growth, the growth mechanism of 6H-SiC is discussed. On (000)C surfaces the vertical growth dominates, while on (0001)Si surfaces the lateral growth dominates. 相似文献
223.
Photoluminescence excitation spectra of donor-acceptor pairs have been observed in phosphorus doped ZnTe. Binding energies of the donor and the acceptor is estimated from the spectra. Emission spectra measured under below-band-gap excitation showed sharp bands superimposed with a broad emission band. The result indicates the existence of two decay processes under the below-band-gap excitation: (1) recombination of an electron and a hole trapped on a given D-A pair, and (2) recombination of D-A pairs with various distances for which bound electrons are formed via conduction band. 相似文献
224.
Sugita M Yamaguchi A Yamagiwa N Handa S Matsunaga S Shibasaki M 《Organic letters》2005,7(23):5339-5342
[reaction, structure: see text] Chiral Y{N(SiMe3)2}3/linked-BINOL catalyst generated Y-enolate in situ from various hydroxyketones (R2 = aryl, heteroaryl). Beta-amino-alpha-hydroxy ketones (R1 = aryl, heteroaryl, alkenyl) were obtained syn-selectively (up to 96/4) in high ee (up to 98%) and good yield (up to 98% yield). 相似文献
225.
Yang Y Nesterenko DV Trump RP Yamaguchi K Bartlett PA Drueckhammer DG 《Journal of chemical information and modeling》2005,45(6):1820-1823
Three new virtual databases have been developed for use with the bond-orientation-based database searching program CAVEAT. These consist of a database of trisubstituted monocyclic hydrocarbons having ethyl, vinyl, and phenyl substituents; a database of unsubstituted bicyclic hydrocarbons; and a database of core structures from established combinatorial synthetic methods having hydrogen, ethyl, vinyl, and phenyl substituents at the readily varied positions. Each collection of molecules was subjected to a batch conformational search, minimization, and conversion to a vector database for use with CAVEAT. 相似文献
226.
Taniguchi J Yamaguchi A Ishimoto H Ikegami H Matsushita T Wada N Gatica SM Cole MW Ancilotto F Inagaki S Fukushima Y 《Physical review letters》2005,94(6):065301
Heat capacity measurements have been made down to 5 mK for 3He fluid films adsorbed in one-dimensional (1D) nanometer-scale pores, 28 A in diameter, preplated with 4He of 1.47 atomic layers. At low 3He density, the heat capacity shows a density-dependent, Schottky-like peak near 150 mK asymptoting to the value corresponding to a 2D Boltzmann gas at high temperatures. The peak behavior is attributed to the crossover from a 2D gas to a 1D state at low temperatures. The degenerate state of the 1D 3He fluid is indicated by a predominantly linear temperature dependence below about 30 mK. 相似文献
227.
The effect of data assimilation of large-scale eddies on small-scale eddies in turbulence is studied by direct numerical simulations (DNSs) of Navier-Stokes turbulence with Taylor microscale Reynolds numbers up to 179. The DNSs show that even if the data of small-scale eddies are lost at some initial instant, they can be regenerated from the data of large-scale eddies under the condition that Fourier modes with wave number less than a critical wave number k(*) are continuously assimilated, where k(*) approximately 0.2eta(-1) with eta identical with(nu(3)/epsilon)(1/4), epsilon the mean energy dissipation rate, and nu the viscosity. 相似文献
228.
229.
[reaction: see text] The reaction of (o-silylphenyl)acetylene derivatives with lithium naphthalenide undergoes intramolecular reductive cyclization to produce various silaindene derivatives. On the basis of this methodology, a series of silaindene-containing pi-electron systems are synthesized that show intense blue to greenish-blue fluorescence. 相似文献
230.