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81.
The diagonal elements of the first and second order spinless density matrices have been calculated for the lowest excited1
P and3
P terms of Be, B+ and C++ using wavefunctions at different levels of approximations published in the literature. The analysis of these functions has
resulted in a new interpretation of Hund's first rule in terms of an anisotropic screening effect. 相似文献
82.
ABSTRACTCo-crystallization frequently employs forces such as hydrogen bonds, halogen bonds, and π-π stacking to assemble molecules in a multi-component crystal. In an effort to increase the strength of the intermolecular interaction between the anti-cholesterol drug bezafibrate (BEZA), a wastewater contaminant, and hydrogen-bond-acceptor molecules, we modified the pKa values of the acceptors. Here, we describe the first series of salts incorporating BEZA and achieve a variety of supramolecular architectures including discrete assemblies, 1D chains, tapes, and 2D sheets. We discuss exceptions to the pKa rule, and demonstrate that the presence of hydrogen-bond-donor atoms on the acceptor molecule supports salt formation. 相似文献
83.
Crystallization of organic molecules is quite complicated because the crystallization process is governed by weak intermolecular interactions. By exploiting aggregation‐induced emission (AIE), we attempted to realize the selective detection of phase transformation during the evaporative crystallization of hexaphenylsilole (HPS), which shows different fluorescent colors in the amorphous and crystalline phases. No fluorescence emission was observed in the HPS solution immediately after dropping on the glass substrate due to the non‐radiative deactivation induced by intramolecular rotational or vibrational motion, suggesting that HPS exists as a monomer in solution. As time elapsed after dropping, green emission first appeared, which changed to blue after solvent evaporation, because of phase transformation from the amorphous state to the crystalline state. This phenomenon supports not only the two‐step nucleation model involving an intermediate such as a liquid‐like cluster prior to nucleation but also the real‐time detection of Ostwald's rule of stages during evaporative crystallization. 相似文献
84.
85.
Guohai Deng Shujun Lei Dr. Sudip Pan Jiaye Jin Prof. Guanjun Wang Prof. Lili Zhao Prof. Mingfei Zhou Prof. Gernot Frenking 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(46):10487-10500
Homoleptic Group 4 metal carbonyl cation and neutral complexes were prepared in the gas phase and/or in solid neon matrix. Infrared spectroscopy studies reveal that both zirconium and hafnium form eight-coordinate carbonyl neutral and cation complexes. In contrast, titanium forms only the six-coordinate Ti(CO)6+ and seven-coordinate Ti(CO)7. Titanium octacarbonyl Ti(CO)8 is unstable as a result of steric repulsion between the CO ligands. The 20-electron Zr(CO)8 and Hf(CO)8 complexes represent the first experimentally observed homoleptic octacarbonyl neutral complexes of transition metals. The molecules still fulfill the 18-electron rule, because one doubly occupied valence orbital does not mix with any of the metal valence atomic orbitals. Zr(CO)8 and Hf(CO)8 are stable against the loss of one CO because the CO ligands encounter less steric repulsion than Zr(CO)7 and Hf(CO)7. The heptacarbonyl complexes have shorter metal−CO bonds than that of the octacarbonyl complexes due to stronger electrostatic and covalent bonding, but the significantly smaller repulsive Pauli term makes the octacarbonyl complexes stable. 相似文献
86.
U. Turgut E. Büyükkasap O. ?im?ek M. Ertu?rul 《Journal of Quantitative Spectroscopy & Radiative Transfer》2005,92(2):143-151
The total mass attenuation coefficients for element Fe and compounds FeF3, Fe2O3, FeCl2·4H2O, FeCl32NH4Cl·H2O were measured at different energies between 4.508-17.443 keV range by using secondary excitation method. Ti, V, Cr, Ni, Cu, Zn, As, Se, Br, Rb, Sr, Y, Zr, Nb, Mo were chosen as secondary exciter. 59.5 keV gamma rays emitted from an 241Am annular source were used to excite secondary exciter and Kα(K-L3, L2) lines emitted of secondary exciter were counted by a Si(Li) detector with a resolution of 160 eV at 5.9 keV. It was observed that mixture rule method is not a suitable method for determination of the mass attenuation coefficients of compounds, especially at energy that is near the absorption edge. Obtained values were compared with theoretical values. 相似文献
87.
Ricardo Vessecchi Flávio S. Emery Sérgio E. Galembeck Norberto P. Lopes 《Journal of mass spectrometry : JMS》2012,47(12):1648-1659
In order to understand the influence of alkyl side chains on the gas‐phase reactivity of 1,4‐naphthoquinone derivatives, some 2‐hydroxy‐1,4‐naphthoquinone derivatives have been prepared and studied by electrospray ionization tandem mass spectrometry in combination with computational quantum chemistry calculations. Protonation and deprotonation sites were suggested on the basis of gas‐phase basicity, proton affinity, gas‐phase acidity (ΔGacid), atomic charges and frontier orbital analyses. The nature of the intramolecular interaction as well as of the hydrogen bond in the systems was investigated by the atoms‐in‐molecules theory and the natural bond orbital analysis. The results were compared with data published for lapachol (2‐hydroxy‐3‐(3‐methyl‐2‐butenyl)‐1,4‐naphthoquinone). For the protonated molecules, water elimination was verified to occur at lower proportion when compared with side chain elimination, as evidenced in earlier studies on lapachol. The side chain at position C(3) was found to play important roles in the fragmentation mechanisms of these compounds. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
88.
在Nagel Schrekenberg单车道元胞自动机交通流模型(简称NS模型)的基础上,考虑车辆之间的相对运动薛郁等提出了一种改进的单车道元胞自动机交通流模型(简称改进的NS模型).通过两种情况列出了改进的NS模型存在不尽周严的地方,随之在新模型中引入了行车状态 变量和反馈规则,从而控制车辆出现倒车和刹车过急等现象.通过计算机对新模型进行模拟 ,发现减速概率和车流密度对车流状态的演化影响很大,当减速概率高(如道路条件差)时 ,即使车流密度低,车流也会出现局部堵塞状态;而当减速概率一定时,随着车流密度增加 ,车流的运动相与堵塞相发生了全局性的交替出现,此时类似于波的波峰和波谷的传播.与 改进的NS模型相比较,新模型模拟的车流量较高,说明新模型减少了车流的总体停滞状态.
关键词:
交通流
元胞自动机
行车状态
反馈规则 相似文献
89.
信息熵增量最小化准则在供应链中的应用 总被引:1,自引:0,他引:1
本文研究了在考虑利润最大化准则和信息熵增量最小准则下,既能满足了利润最大化,又要增加利润可得性,销售商如何确定订购量的问题。数字实验表明:考虑双重准则得到的策略比仅考虑利润最大化准则得到的策略更好,可以使供应链、销售商及制造商都受益。 相似文献
90.