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41.
A series of complexes formed between halogen-containing molecules and ammonia have been investigated by means of the atoms in molecules (AIM) approach to gain a deeper insight into halogen bonding. The existence of the halogen bond critical points (XBCP) and the values of the electron density (Pb) and Laplacian of electron density (V2pb) at the XBCP reveal the closed-shell interactions in these complexes. Integrated atomic properties such as charge, energy, polarization moment, volume of the halogen bond donor atoms, and the corresponding changes (△) upon complexation have been calculated. The present calculations have demonstrated that the halogen bond represents different AIM properties as compared to the well-documented hydrogen bond. Both the electron density and the Laplacian of electron density at the XBCP have been shown to correlate well with the interaction energy, which indicates that the topological parameters at the XBCP can be treated as a good measure of the halogen bond strength In addition, an excellent linear relationship between the interatomic distance d(X…N) and the logarithm of Pb has been established. 相似文献
42.
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44.
《Physics letters. A》2006,349(6):462-466
Many social, technological, biological and economical systems are best described by evolved network models. In this short Letter, we propose and study a new evolving network model. The model is based on the new concept of neighbourhood connectivity, which exists in many physical complex networks. The statistical properties and dynamics of the proposed model is analytically studied and compared with those of Barabási–Albert scale-free model. Numerical simulations indicate that this network model yields a transition between power-law and exponential scaling, while the Barabási–Albert scale-free model is only one of its special (limiting) cases. Particularly, this model can be used to enhance the evolving mechanism of complex networks in the real world, such as some social networks development. 相似文献
45.
张少林 《高校应用数学学报(英文版)》2004,19(3):257-262
In this paper, an important problem arising from conservation biology is considered. Namely, how does the introduced species affect the survival of a native endangered species through predation? By using Kamke comparison theorem and some results in Cui and Chen‘s paper (1998), some sufficient conditions that guarantee the permanence of the species and global stability of a unique positive periodic solution are obtained. Biological implication of these results are discussed. 相似文献
46.
In the present paper, we prove that the Bernstein-Kantorovič operators have the ability of preserving translation property
in both C and Lp norms.
Supported (in part) by the NSFC(10471130,10371024) of PRC and the Natural Science Foundation (Y604003) of Zhejiang Province. 相似文献
47.
《Electrochemistry communications》2007,9(8):1991-1997
The controllability of pore density and diameter is critical for emerging applications, e.g., non-lithographic photonic-crystal formation; however pore density and diameter could either increase or decrease self-orderedly with enhanced current density. In this letter, similar paradoxical phenomena were demonstrated; the etch rate as a function of field strength was evidenced and interpreted in light of current-burst-model. Based on a hybrid of SCR (space charge region) and breakdown effects, a semi-quantitative model was established in order to disentangle the paradox: such a model could also potentially serve as a design reference for various applications as far as breakdown comes into play. The paradox was finally found to be dominated by physics on patterned samples. 相似文献
48.
针对带约束的凸多面体线性不确定模型,提出了一种新型鲁棒预测控制方法,它采用离散化的不确定模型构造最小-最大优化控制问题,并在其中直接引入状态反馈机制,与其他最小-最大预测控制方法相比,这种方法等效于增加了控制序列的长度,为优化问题增加了更多的自由度,从而扩大了可行域,作为最小化目标的是离散化不确定系统在整个预测时域上二次型成本函数的最大值,而不是各预测阶段应成本项的上界之和,从而减少了与最小-最大优化相关的方程个数,有利于降低计算复杂性,文中进一步证明了不确定系统的闭环稳定性取决于优化问题在初始时刻的可行性,并将优化问题转化为线性矩阵不等式形式。最后,以数值仿赵例子验证了方法的有效性。 相似文献
49.
《Journal of Electrostatics》2006,64(7-9):569-573
Experimental and theoretical investigations have been conducted for the on-set of electrohydrodynamically (EHD) induced turbulence for cylinder in cross flow. The experiments were conducted for Reynolds numbers from 0.2 to 80 based on cylinder diameters, and Reynolds numbers from 103 to 4×103 based on the flow channel width. This flow conditions represent laminar to transitional-flow before the on-set of the EHD-turbulent flow. Theoretical analysis was based on the mass, momentum, and charged particle conservation equations coupled with the Poisson's equation for electric field evaluation. The results showed that: (1) on-set of EHD turbulence is initiated near the real-stagnation point; (2) EHD turbulence can be generated even for Reynolds numbers (Re) less than 0.2, if the EHD number (Ehd) is larger than the critical Reynolds number square (Ehd>Re2); and (3) the electrical origin of instability, which is leading into the on-set of turbulence can be estimated from Ehd/Db2>Re2 relation, where Db is the Debye number. 相似文献
50.
《Physica A》2006,365(1):190-196
The formula for probability density functions (PDFs) has been extended to include PDF for energy dissipation rates in addition to other PDFs such as for velocity fluctuations, velocity derivatives, fluid particle accelerations, energy transfer rates, etc., and it is shown that the formula actually explains various PDFs extracted from direct numerical simulations and experiments performed in a wind tunnel. It is also shown that the formula with appropriate zooming increment corresponding to experimental situation gives a new route to obtain the scaling exponents of velocity structure function, including intermittency exponent, out of PDFs of velocity fluctuations. 相似文献