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991.
《Applied Surface Science》2008,254(10):3039-3044
In this work, we have investigated the electrical characteristics, such as current-voltage (I-V) and capacitance-voltage (C-V) measurements, of identically prepared crystal violet/p-Si Organic/Inorganic (OI) Schottky structures formed by evaporation of organic compound solution to directly p-Si semiconductor substrate. It has been seen that the crystal violet organic dye thin film on the p-Si substrate has exhibited a good rectifying behavior. The barrier heights (BHs) and ideality factors of all devices have been calculated from the electrical characteristics. Although the diodes were all identically prepared, there was a diode-to-diode variation: the effective barrier heights ranged from 0.6 ± 0.1 to 0.8 ± 0.1 eV, and the ideality factor from 1.6 ± 0.4 to 3.5 ± 0.4. The barrier height versus ideality factor plot has been plotted for the OI devices. Lateral homogeneous BH was calculated as a value of 0.7 eV from the observed linear correlation between BH and ideality factor, which can be explained by laterally inhomogeneities of BHs. The values of barrier height and acceptor doping concentration yielded from the reverse bias C-V measurements ranged from 0.7 ± 0.1 to 1.3 ± 0.1 eV and from (4.7 ± 0.8) × 1014 to (8.1 ± 0.8) × 1014 cm−3, respectively. The mean barrier height and mean acceptor doping concentration from C-V characteristics has been calculated 1.0 eV and 5.9 × 1014 cm−3, respectively. It has been seen that the mean BH value of 0.7 eV obtained for the Al/methyl violet/p-Si contact is significantly larger than BH values of the conventional Al/p-Si Schottky diodes. Thus, modification of the interfacial potential barrier for metal/Si diodes has been achieved using a thin interlayer of the methyl violet organic semiconductor; this has been ascribed to the fact that the methyl violet interlayer increases the effective barrier height by influencing the space charge region of Si. 相似文献
992.
Proteins are important biomolecules, which perform diverse structural and functional roles in living systems. Starting from
a linear chain of amino acids, proteins fold to different secondary structures, which then fold through short- and long-range
interactions to give rise to the final three-dimensional shapes useful to carry out the biophysical and biochemical functions.
Proteins are defined as having a common ‘fold’ if they have major secondary structural elements with same topological connections.
It is known that folding mechanisms are largely determined by a protein’s topology rather than its interatomic interactions.
The native state protein structures can, thus, be modelled, using a graph-theoretical approach, as coarse-grained networks
of amino acid residues as ‘nodes’ and the inter-residue interactions/contacts as ‘links’. Using the network representation
of protein structures and their 2D contact maps, we have identified the conserved contact patterns (groups of contacts) representing
two typical folds — the EF-hand and the ubiquitin-like folds. Our results suggest that this direct and computationally simple
methodology can be used to infer about the presence of specific folds from the protein’s contact map alone.
相似文献
993.
粉末热压扩散与应力场耦合的力学模型 总被引:3,自引:0,他引:3
以弹性接触应力场为初始条件,建立了热压条件下球形颗粒表面扩散与应力场耦合的力学模型. 引入包含表面能项级数形式的应力函数,以描述随时间演化的表面扩散过程及扩散对应力场演化的影响. 而应力场通过改变化学势梯度,又会促进(或阻止)表面扩散结合的进程.利用该模型分析了压力、温度和界面区应力场演化对致密化参数的影响. 比较了满足粘着或非粘着对结合宽度和应力分布的影响,将考虑粘着的弹性接触应力场作为初始条件,分析了弹性变形和表面扩散共同驱动的粉末冶金热压烧结致密化规律. 相似文献
994.
Elaine Pratt Alain Leger Michel Jean 《Archive of Applied Mechanics (Ingenieur Archiv)》2008,78(2):89-104
Critical values of the parameters governing the dynamics of simple systems appear when Coulomb friction is not regularized.
We explore such systems using a method based on the fact that under constant or analytical data the trajectory exists, is
unique and is also sufficiently regular. In fact these properties justify elementary analytical computations on successive
time intervals where the condition used to connect the solution from one interval to the other is due to the regularity. Although
the systems are simple the dynamics turn out to be quite complex and thus furnish an interesting benchmark for contact dynamics
numerical codes. Among other possible applications we choose to present here how to use a mass–spring chain with Coulomb friction
to slow down in a progressive and regular manner an oncoming mass with a given initial velocity. 相似文献
995.
996.
998.
传热与接触两类问题耦合作用的有限元分析 总被引:16,自引:2,他引:14
考虑传热接触耦合作用的热力学分析问题大量存在于工程中,分析的难点是必须考虑热与可移动接触边界间的耦合作用。针对这类问题的求解,该文给出了接触边界上热交换与温度边界条件,并在此基础上建立了两类变分方程,一类是热力学变分泛函,其考虑了接触区域对结构热传导的影响;另一类是二维热弹性接触分析的参数变分原理,可以方便地对接触问题进行求解。文中给出有限元分析的离散公式,并进一步给出两类问题耦合分析的迭代算法,其中接触分析的惩罚因子是可以消除的,数值结果验证了该文的理论与算法。 相似文献
999.
多孔饱和半空间上弹性圆板垂直振动的积分方程 总被引:5,自引:0,他引:5
应用新的方法求解多孔饱和固体的动力基本方程-Biot波动方程,首先把Biot波动方程化为仅有土骨架位移和孔隙水压力的偏微分方程组,并且逐次解耦方法(不引入位移势函数)求解此偏微分方程组,然后按混合边值条件建立多孔饱和半空间上弹性圆板垂直振动的对偶积分方程,用Abel变换化对偶积分方程为第二类Fredholm积分方程。文中考虑两种孔隙流体的表面边界条件:(a)半空间表面(包括圆板与半空间的接触面)是 相似文献
1000.
Methods are presented for obtaining exact analytical representations of supercoiled equilibrium configurations of impenetrable
elastic rods of circular cross-section that have been pretwisted and closed to form rings, and a discussion is given of applications
in the theory of the elastic rod model for DNA. When, as here, self-contact is taken into account, and the rod is assumed
to be inextensible, intrinsically straight, transversely isotropic, and homogeneous, the important parameters in the theory
are the excess link Δℒ (a measure of the amount the rod was twisted before its ends were joined), the ratio ω of the coefficients
of torsional and flexural rigidity, and the ratio d of cross-sectional diameter to the length of the axial curve C. Solutions of the equations of equilibrium are given for cases in which self-contact occurs at isolated points and along
intervals. Bifurcation diagrams are presented as graphs of Δℒ versus the writhe of C and are employed for analysis of the stability of equilibrium configurations. It is shown that, in addition to primary, secondary,
and tertiary branches that arise by successive bifurcations from the trivial branch made up of configurations for which the
axial curve is a circle, there are families of equilibrium configurations that are isolas in the sense that they are not connected
to bifurcation branches by paths of equilibrium configurations compatible with the assumed impenetrability of the rod. Each
of the isolas found to date is connected to a bifurcation branch by a path which, although made up of solutions of the governing
equations, contains regions on which the condition of impenetrability does not hold.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献