全文获取类型
收费全文 | 1622篇 |
免费 | 51篇 |
国内免费 | 7篇 |
专业分类
化学 | 1331篇 |
晶体学 | 10篇 |
力学 | 14篇 |
数学 | 73篇 |
物理学 | 252篇 |
出版年
2023年 | 16篇 |
2022年 | 20篇 |
2021年 | 20篇 |
2020年 | 25篇 |
2019年 | 26篇 |
2018年 | 26篇 |
2017年 | 16篇 |
2016年 | 42篇 |
2015年 | 33篇 |
2014年 | 48篇 |
2013年 | 84篇 |
2012年 | 142篇 |
2011年 | 111篇 |
2010年 | 61篇 |
2009年 | 71篇 |
2008年 | 113篇 |
2007年 | 122篇 |
2006年 | 125篇 |
2005年 | 95篇 |
2004年 | 77篇 |
2003年 | 59篇 |
2002年 | 42篇 |
2001年 | 26篇 |
2000年 | 23篇 |
1999年 | 12篇 |
1998年 | 14篇 |
1997年 | 10篇 |
1996年 | 9篇 |
1995年 | 13篇 |
1994年 | 7篇 |
1993年 | 9篇 |
1992年 | 8篇 |
1991年 | 9篇 |
1990年 | 8篇 |
1988年 | 12篇 |
1986年 | 7篇 |
1985年 | 16篇 |
1984年 | 15篇 |
1983年 | 10篇 |
1982年 | 12篇 |
1981年 | 8篇 |
1980年 | 5篇 |
1979年 | 10篇 |
1978年 | 10篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1975年 | 5篇 |
1974年 | 5篇 |
1971年 | 6篇 |
1969年 | 4篇 |
排序方式: 共有1680条查询结果,搜索用时 8 毫秒
991.
A Haldane chain under applied field is analyzed numerically, and a clear minimum of magnetization is observed as a function of temperature. We elucidate its origin using the effective theory near the critical field and propose a simple method to estimate the gap from the magnetization at finite temperatures. We also demonstrate that there exists a relation between the temperature dependence of the magnetization and the field dependence of the spin-wave velocity. Our arguments are universal for general axially symmetric one-dimensional spin systems. 相似文献
992.
The noisy fluctuation of chemical reactions should profoundly affect the oscillatory dynamics of gene circuit. In this paper a prototypical genetic oscillator, repressilator, is numerically simulated to analyze effects of noise on oscillatory dynamics. The oscillation is coherent when the protein number and the rate of the DNA state alteration are within appropriate ranges, showing the phenomenon of coherence resonance. Stochastic fluctuation not only disturbs the coherent oscillation in a chaotic way but also destabilizes the stationary state to make the oscillation relatively stable. Bursting in translation, which is a source of intense stochastic fluctuation in protein numbers, suppresses the destructive effects of the finite leakage rate of protein production and thus plays a constructive role for the persistent oscillation. When multiple repressilators are coupled to each other, the cooperative interactions among repressilators enhance the coherence in oscillation but the dephasing fluctuation among multiple repressilators induces the amplitude fluctuation in the collective oscillation. 相似文献
993.
Utsuno M Yutaka T Murata M Kurihara M Tamai N Nishihara H 《Inorganic chemistry》2007,46(26):11291-11296
Anthraquinone-bridged mononuclear and dinuclear complexes, [PtCl(AQ-amide-tpy)](PF6) (1), [Pt2Cl2(AQ-amide-tpy2)](PF6)2 (2), and [Pt2Cl2(AQ-eth-tpy2)](PF6)2 (3), were synthesized and their photochemical properties were investigated. Amide-bound mononuclear complex 1 exhibited only metal-to-ligand charge transfer (MLCT) absorption and emission, whereas dinuclear complex 2 exhibited a low-energy emission around 700 nm at room temperature. Emission lifetime analysis indicated that this emission was originated from the metal-metal-to-ligand charge transfer (MMLCT) excited state, implying the existence of an intramolecular Pt-Pt interaction at the photoexcited state. 3 with rigid ethynylene linkers showed a low-energy absorption around 520 nm (epsilon = approximately 1100 M(-1) cm(-1)) in addition to an 1MLCT absorption, which was ascribed to a 3MLCT absorption from the consideration of the Pt-Pt distance on a geometry-optimized structure. The emission of 3 appeared at 600 nm, which is higher in energy compared with the emission of 2. It is postulated that the restriction of the Pt-Pt distance flexibility in the rigid structure of 3 prevents the significant increase of the Pt-Pt interaction at the excited state. 相似文献
994.
Dye-sensitized TiO2 solar cells using imidazolium-type ionic liquid crystal systems as effective electrolytes 总被引:1,自引:0,他引:1
Yamanaka N Kawano R Kubo W Masaki N Kitamura T Wada Y Watanabe M Yanagida S 《The journal of physical chemistry. B》2007,111(18):4763-4769
A novel ionic liquid crystal (ILC) system (C(12)MImI/I(2)) with a smectic A phase used as an electrolyte for a dye-sensitized solar cell (DSSC) showed the higher short-circuit current density (J(SC)) and the higher light-to-electricity conversion efficiency than the system using the non-liquid crystalline ionic liquid (C(11)MImI/I(2)), due to the higher conductivity of ILC. To investigate charge transport properties of the electrolytes in detail, the exchange reaction-based diffusion coefficients (D(ex)) were evaluated. The larger D(ex) value of ILC supported that the higher conductivity of ILC is attributed to the enhancement of the exchange reaction between iodide species. As a result of formation of the two-dimensional electron conductive pathways organized by the localized I(3)- and I- at S(A) layers, the concentration of polyiodide species exemplified by I(m)- (m = 5, 7, ...) was higher in C(12)MImI/I(2). However, as the increment of the concentration of polyiodide species is less than that of D(ex), the contribution of a two-dimensional structure of the conductive pathway through the increase of collision frequency between iodide species was proposed. Furthermore, a quasi-solid-state ionic liquid crystal DSSC was successfully fabricated by employing a low molecular gelator. Addition of the 5.0 g/L gelator to ILC improved light-to-electricity conversion efficiency through the increase of J(SC) due to the enhancement of the conductivity in C(12)MImI/I(2)-gel. 相似文献
995.
996.
997.
998.
Carbon dioxide in atmosphere is increasing gradually every year and the amount of its generation is restricted. Carbon dioxide is dissolved in environmental waters and kept equilibrium between air and water. 相似文献
999.
1000.