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41.
M. Wołoszyn D. Stauffer K. Kułakowski 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,57(3):331-335
We investigate the network model of community by Watts, Dodds and Newman (D.J. Watts et al., Science 296, 1302 (2002)) as a hierarchy of groups, each of 5 individuals. A homophily parameter
α controls the probability proportional to exp (-αx) of selection of neighbours
against distance x. The network nodes are endowed with spin-like variables si = ± 1,
with Ising interaction J > 0. The Glauber dynamics is used to investigate the
order-disorder transition. The transition temperature Tc is close to 3.8 for
α < 0.0 and it falls down to zero above this value. The result provides a mathematical
illustration of the social ability to a collective action via weak ties, as discussed
by Granovetter in 1973. 相似文献
42.
Study of carboxylic functionalization of polypropylene surface using the underwater plasma technique
R. S. Joshi J. F. Friedrich M. H. Wagner 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(2):249-258
Non-equilibrium solution plasma treatment of polymer surfaces in water offers the possibility of more dense and selective
polymer surface functionalization in comparison to the well-known and frequently used low-pressure oxygen plasma. Functional
groups are introduced when the polymer surface contacts the plasma moderated solution especially water solutions. The emission
of ions, electrons, energy-rich neutrals and complexes, produced by the ion avalanche are limited by quenching, with the aid
of the ambient water phase. The UV-radiation produced in plasma formation also helps to moderate the reaction solution further
by producing additional excited, ionized/dissociated molecules. Thus, monotype functional groups equipped polymer surfaces,
preferably OH groups, originating from the dissociated water molecules, could be produced more selectively. An interesting
feature of the technique is its flexibility to use a wide variety of additives in the water phase. Another way to modify polymer
surfaces is the deposition of plasma polymers carrying functional groups as carboxylic groups used in this work. Acetic acid,
acrylic acid, maleic and itaconic acid were used as additive monomers. Acetic acid is not a chemically polymerizing monomer
but it could polymerize by monomer/molecular fragmentation and recombination to a cross linked layer. The other monomers form
preferably water-soluble polymers on a chemical way. Only the fragmented fraction of these monomers could form an insoluble
coating by cross linking to substrate. The XPS analysis was used to track the alterations in –O-CO- bond percentage on the
PP surface. To identify the -COOH groups on substrate surface unambiguously, which have survived the plasma polymerization
process, the derivatization with trifluoroethanol was performed. 相似文献
43.
Shreyas Gokhale 《物理学进展》2016,65(4):363-452
The glass transition is the most enduring grand-challenge problem in contemporary condensed matter physics. Here, we review the contribution of colloid experiments to our understanding of this problem. First, we briefly outline the success of colloidal systems in yielding microscopic insights into a wide range of condensed matter phenomena. In the context of the glass transition, we demonstrate their utility in revealing the nature of spatial and temporal dynamical heterogeneity. We then discuss the evidence from colloid experiments in favor of various theories of glass formation that has accumulated over the last two decades. In the next section, we expound on the recent paradigm shift in colloid experiments from an exploratory approach to a critical one aimed at distinguishing between predictions of competing frameworks. We demonstrate how this critical approach is aided by the discovery of novel dynamical crossovers within the range accessible to colloid experiments. We also highlight the impact of alternate routes to glass formation such as random pinning, trajectory space phase transitions and replica coupling on current and future research on the glass transition. We conclude our review by listing some key open challenges in glass physics such as the comparison of growing static length scales and the preparation of ultrastable glasses that can be addressed using colloid experiments. 相似文献
44.
45.
T. Grenet J. Delahaye M. Sabra F. Gay 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,56(3):183-197
We present a study of non-equilibrium phenomena observed
in the electrical conductance of insulating granular aluminium thin films.
An anomalous field effect and its slow relaxation are studied in some
detail. The phenomenology is very similar to the one already observed in
indium oxide. The origin of the phenomena is discussed. In granular systems,
the present experiments can naturally be interpreted along two different
lines. One relies on a slow polarisation in the dielectric surrounding the
metallic islands. The other one relies on a purely electronic mechanism: the
formation of an electron Coulomb glass in the granular metal. More selective
experiments and/or quantitative predictions about the Coulomb glass
properties are still needed to definitely distinguish between the two
scenarios. 相似文献
46.
An effort has been made for obtaining the anharmonic properties of rocksalt structure solids starting from primary physical parameters viz. nearest-neighbor distance and hardness parameter assuming long- and short-range potentials at elevated temperatures. The elastic energy density for a deformed crystal can be expanded as power series of strains for obtaining coefficients of quadratic, cubic and quartic terms which are known as the second-, third- and fourth-order elastic constants, respectively. When the values of the higher-order elastic constants are known for a crystal, many of the anharmonic properties of the crystal can be treated within the limit of the continuum approximation in a quantitative manner. In this study, higher-order elastic constants are computed up to their melting temperature for rocksalt structure solids, which are alkali cyanides, sodium and potassium halides. The first order pressure derivatives of second- and third-order elastic constants, the second-order pressure derivatives of second-order elastic constants and partial contractions are also evaluated at different temperatures for these substances. The results thus obtained are compared with experimental data and found in well agreement with present values. 相似文献
47.
苹果可溶性固形物便携式检测实验研究 总被引:1,自引:0,他引:1
为实现苹果可溶性固形物的便携式快速检测,搭建了以STS光谱仪和自制样品杯作为光谱检测装置的苹果可溶性固形物便携式检测平台。采用自行设计的检测平台采集了苹果的近红外漫反射光谱,对比分析了不同的光照角度、光源与探头距离对光谱响应特性的影响,建立了苹果可溶性固形物偏最小二乘模型(PLS)和最小二乘支持向量机模型(LS-SVM),采用连续投影算法及主成分分分析法对最小二乘支持向量机模型进行了优化,并对比分析了两种检测模型的优劣。其中当光源距探头距离为15 mm光源角度为45°时,结合偏最小二乘法建立苹果的可溶性固形物定量检测模型精度最高。模型的预测集相关系数为0.924,预测均方根误差为0.334%。实验结果表明,采用四周照射、底部接收并结合避光圈的这种结构布置能够有效的克服杂散光现象并且提高了光谱中的有效信息。研究可为快速、便携的苹果可溶性固形物检测仪器的设计提供参考依据和理论支撑。 相似文献
48.
G. Sidenius 《辐射效应与固体损伤》2013,168(1-4):145-155
An analysis of some of the fundamental and special physical processes occurring in discharge and plasma ion sources is presented. The main purpose of the lecture is to present to the users of ion sources some key elements of information, of which not all may be generally recognised and which hopefully will be of value for a better understanding of the operational problems related to the complex behaviour of discharge and plasma ion sources. 相似文献
49.
K. Lochmann A. Anikeenko A. Elsner N. Medvedev D. Stoyan 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,53(1):67-76
The performance of various structure characteristics in
the task of indicating structural peculiarities in packings of
hard spheres is investigated. Various characteristics based on
Voronoi polyhedra, spherical harmonics, and Delaunay simplices are
considered together with the pair correlation function and the
mean number of r-close triples. They are applied to a set of
hard sphere packings of density φ from 0.62 to 0.72. It turns
out that all used structure characteristics are able to indicate
changes of order from non-crystalline to crystalline packings.
However, not all of them are sensitive enough to indicate
different stages of structure transformation under densification.
The characteristics based on Delaunay simplices turn out to be the
most sensitive for this purpose.
For the models considered three principal structure classes are
found: packings of densities lower than the known critical value
0.64 showing a non-crystalline behavior; packings with
considerable crystalline regions for φ up to 0.66–0.67;
rather complete crystals although with numerous defects for φ
above 0.67. 相似文献
50.
C. Monthus T. Garel 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,53(1):39-45
The directed polymer in a 1+3 dimensional
random medium is known to present a disorder-induced phase
transition. For a polymer of length L, the high temperature
phase is characterized by a diffusive behavior for the end-point
displacement R2 ∼L and by free-energy fluctuations of order
ΔF(L) ∼O(1). The low-temperature phase is characterized by
an anomalous wandering exponent R2/L ∼Lω and
by free-energy fluctuations of order ΔF(L) ∼Lω
where ω∼0.18. In this paper, we first study the scaling
behavior of various properties to localize the critical temperature
Tc. Our results concerning R2/L and ΔF(L) point towards
0.76 < Tc ≤T2=0.79, so our conclusion is that Tc is equal
or very close to the upper bound T2 derived by Derrida and
coworkers (T2 corresponds to the temperature above which the ratio
remains finite as L ↦
∞). We then present histograms for the free-energy, energy and
entropy over disorder samples. For T ≫Tc, the free-energy
distribution is found to be Gaussian. For T ≪Tc, the free-energy
distribution coincides with the ground state energy distribution, in
agreement with the zero-temperature fixed point picture. Moreover the
entropy fluctuations are of order ΔS ∼L1/2 and follow a
Gaussian distribution, in agreement with the droplet predictions,
where the free-energy term ΔF ∼Lω is a near
cancellation of energy and entropy contributions of order L1/2. 相似文献