全文获取类型
收费全文 | 5868篇 |
免费 | 703篇 |
国内免费 | 610篇 |
专业分类
化学 | 1437篇 |
晶体学 | 50篇 |
力学 | 805篇 |
综合类 | 125篇 |
数学 | 2404篇 |
物理学 | 2360篇 |
出版年
2024年 | 12篇 |
2023年 | 61篇 |
2022年 | 107篇 |
2021年 | 134篇 |
2020年 | 147篇 |
2019年 | 169篇 |
2018年 | 153篇 |
2017年 | 201篇 |
2016年 | 208篇 |
2015年 | 173篇 |
2014年 | 288篇 |
2013年 | 497篇 |
2012年 | 288篇 |
2011年 | 318篇 |
2010年 | 233篇 |
2009年 | 358篇 |
2008年 | 320篇 |
2007年 | 336篇 |
2006年 | 345篇 |
2005年 | 297篇 |
2004年 | 270篇 |
2003年 | 253篇 |
2002年 | 254篇 |
2001年 | 213篇 |
2000年 | 196篇 |
1999年 | 192篇 |
1998年 | 151篇 |
1997年 | 133篇 |
1996年 | 105篇 |
1995年 | 92篇 |
1994年 | 80篇 |
1993年 | 68篇 |
1992年 | 72篇 |
1991年 | 48篇 |
1990年 | 53篇 |
1989年 | 32篇 |
1988年 | 59篇 |
1987年 | 44篇 |
1986年 | 40篇 |
1985年 | 30篇 |
1984年 | 27篇 |
1983年 | 14篇 |
1982年 | 26篇 |
1981年 | 18篇 |
1980年 | 8篇 |
1979年 | 10篇 |
1978年 | 16篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1973年 | 8篇 |
排序方式: 共有7181条查询结果,搜索用时 15 毫秒
991.
992.
K. Morawetz C. Olbrich S. Gemming 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(3):311-317
The coverage of vicinal, stepped surfaces with molecules is simulated with
the help of a two-dimensional Ising model including local distortions and
an Ehrlich-Schwoebel barrier term at the steps. An effective two-spin model is capable
to describe the main properties of this distorted Ising model. It is employed
to analyze the behavior of the system close to the critical points.
Within a well-defined regime of bonding strengths and Ehrlich-Schwoebel barriers we
find a reduction of coverage (magnetization) at low temperatures due to the
presence of the surface step. This results in a second, low-temperature
transition besides the standard Ising order-disorder transition.
The additional transition is characterized by a divergence of the
susceptibility as a finite-size effect. Due to the
surface step the mean-field specific heat diverges with a power law. 相似文献
993.
Spontaneous-search method and short-time dynamics: applications to the
Domany-Kinzel cellular automaton 总被引:1,自引:0,他引:1
S. D. da Cunha U. L. Fulco L. R. da Silva F. D. Nobre 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(1):93-100
The one-dimensional Domany-Kinzel cellular automaton is investigated by two
numerical approaches: (i) the spontaneous-search method, which is a method
appropriated for a search of criticality; (ii) short-time dynamics. Both
critical frontiers of the system are investigated, namely, the one
separating the frozen and active phases, as well as the critical line
determined by damage spreading between two cellular automata, that splits
the active phase into the nonchaotic and chaotic phases.
The efficiency of the spontaneous-search method is established herein
through a precise estimate of both critical frontiers, and in addition to
that, it is shown that this method may also be used in the determination
of the critical exponent ν⊥. Using the critical frontiers
obtained, other exponents are estimated through short-time dynamics. It is
verified that the critical exponents of both critical frontiers fall in the
universality class of directed percolation. 相似文献
994.
We present a theory for the phase behaviour of mixtures of charge-stabilised colloidal spheres plus interacting polymer chains
in good and θ -solvents within the framework of free-volume theory. We use simple but accurate combination rules for the depletion
thickness around a colloidal particle and for the osmotic pressure up to the semi-dilute concentration regime. Hence, we obtain
expressions for the free energy for mixtures of charged colloidal particles and non-adsorbing interacting polymers. From that,
we calculate the phase behaviour, and discuss its topology in dependence on the competition between the charge-induced repulsion
and the polymer-induced attraction. The homogeneous mixture of colloids and polymers becomes more stabilised against demixing
when increasing the electrostatic repulsion. This charge-induced stabilisation is strongest for small polymer-to-colloid size
ratios and is more pronounced for charged colloids mixed with polymers in a good solvent than for polymers in a θ -solvent.
For the weakly charged regime we find that the phase diagram becomes salt-concentration-independent in the protein limit for
charged colloids plus polymers in a θ -solvent. The liquid window, i.e., the concentration regimes where a colloidal liquid exists, is narrowed down upon increasing the charge-induced repulsion.
Also this effect is more pronounced when charged colloids are mixed with polymer chains in a good solvent. In summary, we
demonstrate that the solvent quality significantly influences the phase behaviour of mixtures of charged colloids plus non-adsorbing
polymers if the range of the screened electrostatic repulsion becomes of the order of the range of the depletion-induced attraction. 相似文献
995.
We consider a crosslinked polymer blend that may undergo a microphase separation. When the temperature is changed from an
initial value towards a final one very close to the spinodal point, the mixture is out equilibrium. The aim is the study of
dynamics at a given time t, before the system reaches its final equilibrium state. The dynamics is investigated through the structure factor, S(q, t), which is a function of the wave vector q, temperature T, time t, and reticulation dose D. To determine the phase behavior of this dynamic structure factor, we start from a generalized Langevin equation (model C) solved by the time composition fluctuation. Beside the standard de Gennes Hamiltonian, this equation incorporates a Gaussian
local noise, ζ. First, by averaging over ζ, we get an effective Hamiltonian. Second, we renormalize this dynamic field theory and write a Renormalization-Group equation
for the dynamic structure factor. Third, solving this equation yields the behavior of S(q, t), in space of relevant parameters. As result, S(q, t) depends on three kinds of lengths, which are the wavelength q
−1, a time length scale R(t) ∼ t
1/z
, and the mesh size ξ
*. The scale R(t) is interpreted as the size of growing microdomains at time t. When R(t) becomes of the order of ξ
*, the dynamics is stopped. The final time, t
*, then scales as t
* ∼ ξ
*
z, with the dynamic exponent z = 6−η. Here, η is the usual Ising critical exponent. Since the final size of microdomains ξ
* is very small (few nanometers), the dynamics is of short time. Finally, all these results we obtained from renormalization
theory are compared to those we stated in some recent work using a scaling argument. 相似文献
996.
采用单室空气阴极微生物燃料电池(MFC)反应器构型, 以不同浓度萘为基底物质, 考察MFC的产电性能、 萘降解率、 化学需氧量(COD)和总有机碳含量(TOC)降解率及MFC阴阳极微生物活性和多样性. 结果表明, 循环伏安曲线受不同浓度萘的影响变化较为明显, 随着萘浓度的增大, 最大功率密度呈下降趋势, 且萘对MFC的阴极电极电势影响较大; 当萘的浓度为15 mg/L时, MFC最大功率密度可达(645.841±28.08) mW/m 2; 对萘的降解率高达100%, 且MFC对COD和TOC的降解率随着萘浓度的提高而增大, 但是增大的速率逐渐减小. 对MFC阳极微生物膜进行高通量测序发现, Geobacter是优势菌属, 相对丰度达81%, 阴极主要以Aquamicrobium为主. 相似文献
997.
结合实例介绍了基于波普尔证伪思想视角下的化学课堂教学,具体教学形式包括:教学预设与生成不一致时,用证实或证伪进行验证;教学设计中埋下教学冲突,给学生创造出证伪机会;充分利用实验探究功能,通过证伪提升原理认识;引导学生自主合作学习时,相互质疑、讨论、释疑、证伪。波普尔证伪思想对化学教学具有一定的启示作用:发展学生的批判思维是化学教学的应有之义;培育学生的创新意识是化学教学的重要职责。 相似文献
998.
We present the next step in an ongoing research program to allow for the black-box computation of the so-called finite-genus solutions of integrable differential equations. This next step consists of the black-box computation of the Abel map from a Riemann surface to its Jacobian. Using a plane algebraic curve representation of the Riemann surface, we provide an algorithm for the numerical computation of this Abel map. Since our plane algebraic curves are of arbitrary degree and may have arbitrary singularities, the Abel map of any connected compact Riemann surface may be obtained in this way. This generality is necessary in order for these algorithms to be relevant for the computation of the finite-genus solutions of any integrable equation. 相似文献
999.
A promising application of the multivariate curve resolution based on alternating least squares (MCR-ALS) method is reported for the analysis of the temperature-dependent conformational changes in poly(l-lysine) (PLL). The MCR-ALS approach has enabled detection of three structural components developed during the melting experiment. Most important is an infrared signature of the intermediate component described as a mixture of native α-helical conformation and its extended forms. 相似文献
1000.
In situ monitoring of nucleation and evolution of Ge nanodots on faintly oxidized Si(1 1 1) surfaces
We have investigated the nucleation and evolution of germanium (Ge) nanodot (ND)s taking place while depositing Ge onto the silicon (Si) (1 1 1) surfaces with ultra-thin Si oxide films by using ultra-high vacuum in situ high-resolution transmission electron microscopy in the profile-imaging geometry. Various types of growth phenomena such as nucleation, growth and coalescence of Ge NDs have successfully been observed. The results show that the growth phenomena of the Ge NDs are dramatically rapid after their size reaches the size of the critical nucleus. The critical nucleus size estimated from a model using the cohesive energy of the Ge NDs has been consistent with observed one. 相似文献