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951.
Protonation increases the total binding energy of the 8-oxoguanine-cytosine (8OG:C) base pair by 60–70% at the B3LYP/6-311++G(d,?p) level of theory. It changes the individual H-bond energies, estimated from electron charge densities at bond critical points, by 1.16 to ?16.41?kcal?mol?1. The individual H-bond energies and the two bond X–Y spin–spin coupling constants (2hJX–Y) increase with protonation where 8OG behaves as an H-bond donor; the reverse is true for the H-bonds in which the 8OG unit acts as an H-bond acceptor. Similar to 2hJX–Y, the value of 1hJO–H (a one-bond H?···?Y spin–spin coupling constant) is distance dependent and in linear correlation with the O?···?H distance, but the 1hJN–H values are independent of the N–H distance and the PSO term is the predominant portion in it. The 1JX–H spin–spin coupling constant is dominated by the negative FC term for all hydrogen bonds, although the PSO term is the best to investigate the behaviour of 1JX–H across the X–H?·?Y H-bond. 相似文献
952.
Monte Carlo simulations with the Keating model have been performed to predict the lattice constant and bond length variations with composition for pseudo-binary semiconducting alloys. In general, it is observed that the deviations of the lattice constants from Vegard's law predictions are larger as the lattice mismatch between the constituent binaries increases. Further, it is noted that these alloys have partial virtual crystal model characteristics and tend to be more towards the flexible (floppy) crystal limit as compared to the rigid crystal limit. The topological rigidity parameters are bond-type dependent. The angular deviations from perfect tetrahedral structure are also measured. 相似文献
953.
Hydrophobic bimetallic catalysts of Pt-M on styrenedivinylbenzene were prepared, where M represents successively: Ir, Rh, Pd, Cu and Ag. The total metal loading was 0.5 wt% and the weight fractions of the metal M were: 0.0,0.05,0.1,0.25,0.5,0.75 and 1.0. For each sample, the catalytic activity for H/D exchange between hydrogen and water vapor was measured. In case of monometallic catalysts, no activity was detected for M = Cu and M = Ag, and the order of the activity values for the other metals was: Pt < Ir < Rh < Pd. For each bimetallic catalyst, the activity measurements indicated a clear interaction between the platinum and the second metal, thus the activity was significantly increased for M = Ir, increased for M = Rh, decreased for M = Pd, drastically decreased for M = Cu and M = Ag. 相似文献
954.
A theory for the coexistence problem of the spin density wave (SDW) and superconductivity (SC) in highly anisotropic materials is presented. On the basis of a simplified electronic band model a Hartree-Fock approximation is applied. It is concluded that SDW is precluded when SC developes at a higher temperature. When the SDW onset temperature is higher than that of SC, these long range orders generally coexist unless two orders interchange by a first order phase transition. Discussions on possible phase diagrams for (TMTSF)2PF6 under pressure are given. 相似文献
955.
Measurements of the pressure and temperature dependence of the a-axis resistivity of (TMTSF) 2ReO4, are presented. The metal-insulator transition seen in this material at the remarkably high temperature of ~180 K at ambient pressure and which is associated with an ordering of the ReO4, anions is suppressed under pressure. For pressures above ~9.5 kbar we observe a superconducting transition near 1.3 K. There is a narrow intermediate pressure regime about 2.5 kbar in width in which both superconductivity and effects of anion ordering are observed. In this regime (i) a superconducting transition is seen near 1.3 K even though ρ just above the transition can be up to 10-100 times greater than ρ(300 K), and (ii) there is an extraordinarily large hysteresis in p below ~ 100 K with the possibility of varying the resistance of the low temperature state by several orders of magnitude by appropriate temperature cycling. These results establish the first order character of the transition. We suggest that at high pressures the anions remain frozen in a metastable disordered state to low temperatures. 相似文献
956.
采用含Davidson修正的内收缩多参考组态相互作用的方法和考虑相对论修正, 在价态范围内的最大相关一致基 aug-cc-pV6Z 的条件下, 对SF分子的基态2∏及几个低激发态4∑-, 2∑-, 2Δ进行了势能扫描计算. 对SF分子的势能曲线进行拟合, 得到了该分子的光谱常数Re, ωe, ωeχe, D0, De, Be和 αe, 通过比较发现它们与已有的实验结果较为一致. 利用SF分子的势能曲线, 通过求解双原子分子核运动的径向Schrödinger方程得到J=0 时SF分子所计算各电子态的多个振动态. 对于每一振动态, 分别计算了振动能级、惯性转动常数和离心畸变常数.
关键词:
SF
势能曲线
光谱常数
分子常数 相似文献
957.
In this paper, we give a definition of pseudo almost periodic sequence and study the existence of pseudo almost periodic sequence to difference equation. Based on these, we investigate the existence of pseudo almost periodic solutions to differential equations with piecewise constant arguments which was considered by K. L. Cooke & J. Wiener and found applications in certain biomedical problems. 相似文献
958.
959.
960.
《Quaestiones Mathematicae》2013,36(3):290-304
Abstract A categorical notion of interior operator is used in topology to define connectedness and disconnectedness with respect to an interior operator. A commutative diagram of Galois connections is used to show a relationship between these notions and Arhangelskii and Wiegandt's notions of connectedness and disconnectedness with respect to a subclass of topological spaces. Examples are included. 相似文献