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131.
The different mechanisms, rotation, inversion, or intermediate mechanism, by which occur the topomerization of imine systems R2 CN X have been studied by applying ab initio, B3LYP, and MP2 methods. The effect of a wide variety of substituents R and X on the isomerization pathway have been examined by computing fully optimized structures of the ground and transition states (136 isomers belonging to different imine families were studied and more than 300 transition structures were determined at various levels of theory). Energy barriers have been also obtained and it was found that the groups R and X have a strong influence on the type of mechanism involved and the activation energies. Thus, and depending on the type of substituents, transition state structures related to the following kinds of processes were found: pure inversion, intermediate mechanisms, rotation, and enhanced rotation (hyper‐rotation). In turn, the corresponding activation energies range between very low (<10 kcal/mol) and extremely high (> 70 kcal/mol) values. A simple index that allows us to quantify the percentage of inversion or rotation mechanism is proposed. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010 相似文献
132.
In this work the Couette cell is compared with a more recently constructed disk shear cell. There are distinct advantages
of the disk over the Couette cell, in particular, when it comes to the determination of the intensity along certain Bragg
rods.
Received: 12 December 2000 Accepted: 31 January 2001 相似文献
133.
一种适合工程实用的捷联航姿算法 总被引:5,自引:0,他引:5
从工程实用的角度出发,针对惯性元件输出中存在干扰这一问题对四元数的三子样旋转矢量算法和四阶龙格-库塔法进行了分析和比较,指出四阶龙格-库塔法是一种具有工程实用价值的捷联航姿算法,并给出了在理想情况和有干扰的情况下算法的仿真结果。 相似文献
134.
Amitabha Ghosh 《Pramana》1986,26(1):1-8
According to the model of inertial induction proposed earlier, the inertia force consists of an acceleration-dependent term
which comes out as identically equal to -ma. Besides, there is a velocity-dependent term which is exceedingly small to be easily detected. However, it has been shown
that this results in a cosmological red shift of light coming from distant stars and galaxies; the magnitude of the red shift
agrees very well with the observed values. Though this model yields correct results when applied to photons it needs modification
before applying to other bodies. A modified form of the inertial induction model is now proposed where the proposed velocity-dependent
inertia forces, when applied to the solar system, yields correct order of magnitude for the secular retardation of the earth’s
rotation. Moreover, a combined model using the velocity term and the tidal friction also does not suggest any close proximity
of the moon to the earth in the past. When the model is applied to the case of Phobos, a secular acceleration of the order
of magnitude of 10−3 deg yr−2 is obtained. 相似文献
135.
Jet-cooled fluorescence excitation and dispersed fluorescence spectra of 9-methylanthracene (MA), 9-cyanoanthracene (CA) and 9-cyano-10-methylanthracene (CMA) have been measured. The spectra of MA and CMA near the S0-S1 origin reveal a prominent torsional progression due to the hindered methyl group rotation and its torsional vibration against the aromatic ring frame. Additionally, the laser induced fluorescence LIF excitation spectrum of CMA shows the splitting of many vibrational modes.Observed positions and relative intensities of the methyl internal rotational bands were interpreted in terms of transitions calculated based on the quantum mechanical one-dimensional rotor. The low-frequency vibrational bands were interpreted also with the all electron quantum mechanical calculations within the RHF/6-31G(d,p), CIS/3-21G and CIS/6-31G(d,p) approximations. It is predicted that in the case of MA the eclipsed geometry (one C-H in the plane of the ring) is most stable in both S0 and S1 states. Conformation of the methyl group in CMA is suggested to change upon S1 ← S0 excitation (π/12 phase shift of the methyl group). The predicted energy barrier for methyl group rotation in the S0 state of CMA is considerably higher (72 cm−1) than that in the S1 state (22 cm−1). Following the present quantum mechanical calculations, the carbon atom of the methyl group belongs to the aromatic plane in the S0 ground state but it deviates from this plane in the S1 excited state. These in turn suggest that the calculated barrier for methyl group rotation in CMA has a 6-fold symmetry in the S0 ground state and roughly a 4-fold symmetry in the S1 state. 相似文献
136.
Windows95环境中转速测量和直流电机转速控制方法 总被引:1,自引:1,他引:0
介绍在Windows95环境中用Visual Basic5.0编写转速测量和直流电机转速控制方法的过程。 相似文献
137.
138.
《Journal of computational chemistry》2017,38(12):892-900
An accurate potential energy surface of sulfur dioxide, SO2, in its ground electronic state has been determined from ab initio calculations using the coupled‐cluster approach in conjunction with the correlation‐consistent basis sets up to septuple‐zeta quality. The results obtained with the conventional and explicitly correlated coupled‐cluster methods are compared. The role of the core–electron correlation, higher‐order valence–electron correlation, scalar relativistic, and adiabatic effects in determining the structure and dynamics of the SO2 molecule is discussed. The vibration‐rotation energy levels of the 32SO2 and 34SO2 isotopologues were predicted using a variational approach. It was shown that the inclusion of the aforementioned effects was mandatory to attain the “spectroscopic” accuracy. © 2017 Wiley Periodicals, Inc. 相似文献
139.
本文以量级分析为基础,建立了一般曲线坐标系上的三维旋转边界层方程。对旋转在边界层中的影响进行分析之后,提出了一个能够处理壁面法向压力梯度不为零问题的压力梯度迭代方法。在传统的Box法的基础上发展了一套完整的求解三维旋转边界层的方法和程序,并对螺旋面、压气机转子叶面以及圆柱面上的旋转边界层进行了计算,与他人的计算和实验的对比分析表明,该方法和程序是正确的,可用于求解任意几何物面上的三维旋转边界层。 相似文献
140.
Angelika Baranowska Krzysztof Z. Ła̧czkowski Andrzej J. Sadlej 《Journal of computational chemistry》2010,31(6):1176-1181
We have carried out extensive studies on the basis set dependence of the calculated specific optical rotation (OR) in molecules at the level of the time–dependent Hartree–Fock and density functional approximations. To reach the limits of the basis set saturation, we have devised an artificial model, the asymmetrically deformed (chiral) methane (CM) molecule. This small system permits to use basis sets which are prohibitively large for real chiral molecules and yet shows all the important features of the basis set dependence of the OR values. The convergence of the OR has been studied with n‐aug‐cc‐pVXZ basis sets of Dunning up to the 6–ζ. In a parallel series of calculations, we have used the recently developed large polarized (LPolX) basis sets. The relatively small LPolX sets have been shown to be competitive to very large n‐aug‐cc‐pVXZ basis sets. The conclusions reached in calculations of OR in CM concerning the usefulness of LPolX basis sets have been further tested on (S)‐methyloxirane and (S)‐fluoro‐oxirane. The smallest set of the LPolX family (LPol–ds) has been found to yield OR values of similar quality as those obtained with much larger Dunning's aug‐cc‐pVQZ basis set. These results have encouraged us to carry out the OR calculations with LPol–ds basis sets for systems as large as β‐pinene and trans‐pinane. In both cases, our calculations have lead to the correct sign of the OR value in these molecules. This makes the relatively small LPol–ds basis sets likely to be useful in OR calculations for large molecules. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010 相似文献