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101.
The phosphine complexes of beryllium chloride, bromide and iodide, [(PMe2Ph)2BeX2], [(PMePh2)2BeX2] and [(PPh3)BeX2]2 (X=Cl, Br, I) were prepared and characterised with multinuclear NMR spectroscopy. Additionally the molecular structure of dinuclear [(PPh3)BeCl2]2 was determined with single crystal X-ray diffraction techniques. The threshold cone angle of the phosphines, below which two ligands can coordinate to the beryllium dihalide fragments, is between 136° and 145°. Halide-chloride exchange in dichloromethane is observed for [(PPh3)BeBr2]2 and [(PPh3)BeI2]2, which leads to the formation of [(PPh3)BeCl2]2. Due to the relatively low Lewis basicity of PPh3, it almost exclusively acts as a spectator ligand with only little formation of phosphonium cations. 相似文献
102.
实验室比对盲样测定是检验实验室能力验证、实验室资质认定、机构考核的主要手段。为研究并解决测试实验室比对土壤盲样中铍、钒、镍、铜、锌、镉、铅的含量,采用微波消解电感耦合等离子体质谱(ICP-MS)法对土壤盲样进行研究,探讨了不同消解酸体系,检出限和定量限、测试模式和干扰消除、精密度和加标回收率、质控样品进行研究。结果表明:用6 mL HNO3,2 mL HCl和1 mL HF为混合酸体系,各待测元素标准曲线相关系数大于0.9995,检出限在0.001~2.985 mg.L-1,定量限在0.003~9.94 mg.L-1,采用氦气碰撞模式测试钒、镍、铜、锌、镉和铅,可以有效的降低多原子离子的干扰;采用no gas模式测试铍,可以有效的提高铍的测试灵敏度。方法精密度为0.2%~6.2%(n=6),加标回收率为92.3%~110.6%,采用土壤标准样品(GSS-4)进行全过程质控研究分析,各元素结果均在标准值参考范围内。用ICP-OES法测试土壤盲样中七种待测金属元素含量与用铑为内标的ICP-MS进行比对,测量分析结果基本一致。 相似文献
103.
Manuel Yáñez Filiberto Ortíz-Chi Gabriel Merino Ibon Alkorta 《Journal of computational chemistry》2023,44(3):159-167
The interaction of ammonia with Ben (n < 1–10) clusters has been investigated by density functional theory and ab initio calculations. The main conclusion is that, regardless of the size of the Be cluster, neither the structure of ammonia nor that of the Be clusters are preserved due to a systematic dissociation of its N H bonds and a spontaneous H-shift toward the available Be atoms. This H migration not only leads to rather stable Be H bonds, but dramatically enhances the strength of the Be N bonds as well. Accordingly, the maximum stability is found for the interaction with the beryllium trimer, leading to a complex with three N Be and three Be H bonds. Another maximum in stability, although lower than that reached for n = 3, is found for the Be heptamer, since from n = 6, a new N Be bond is formed, so that complexes from n = 6 to n = 10 are characterized by the formation of a NBe4 moiety, whose stability reaches a maximum at n = 7. The bonding characteristics of the different species formed are analyzed by means of AIM, NBO, ELF and AdNDP approaches. 相似文献
104.
Armando A. Morin-Martinez Jessica Arcudia Ximena Zarate Miguel Eduardo Cifuentes-Quintal Gabriel Merino 《Journal of computational chemistry》2023,44(3):248-255
Herein we show a density functional theory-based study performed on two recently predicted polymorphs of the BeH2 monolayer, α-BeH2 and β-BeH2. The α-BeH2 phase possesses an in-plane negative Poisson's ratio (NPR), introducing it into the unique group of auxetic materials. Our assessment delves into the linear-elastic and finite-strain regimes to understand both polymorphs' structural and mechanical responses to deformation. We find that the in-plane NPR is shown to be only parallel to the bonds in α-BeH2 and remains along the uniaxial tensile path. Concomitantly, an out-of-plane transition toward auxetic is also revealed in regions exhibiting conventional Poisson's ratios, making α-BeH2 a bidirectionally auxetic material. While phase transitions in β-BeH2 are triggered at very short strains, α-BeH2 displays excellent elasticity against tension, superior to that of most currently known 2D materials. 相似文献
105.
Oriana Brea Prof. Otilia Mó Prof. Manuel Yáñez Prof. Ibon Alkorta Prof. José Elguero 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(36):12676-12682
Through the use of ab initio theoretical models based on MP2/aug‐cc‐pVDZ‐optimized geometries and CCSD(T)/aug‐cc‐pVTZ and CCSD(T)/aug‐c‐pVDZ total energies, it has been shown that the significant electron density rearrangements that follow the formation of a beryllium bond may lead to the appearance of a σ‐hole in systems that previously do not exhibit this feature, such as CH3OF, NO2F, NO3F, and other fluorine‐containing systems. The creation of the σ‐hole is another manifestation of the bond activation–reinforcement (BAR) rule. The appearance of a σ‐hole on the F atoms of CH3OF is due to the enhancement of the electronegativity of the O atom that participates in the beryllium bond. This atom recovers part of the charge transferred to Be by polarizing the valence density of the F into the bonding region. An analysis of the electron density shows that indeed this bond becomes reinforced, but the F atom becomes more electron deficient with the appearance of the σ‐hole. Importantly, similar effects are also observed even when the atom participating in the beryllium bond is not directly attached to the F atom, as in NO2F, NO3F, or NCF. Hence, whereas the isolated CH3OF, NO2F, and NO3F are unable to yield F ??? Base halogen bonds, their complexes with BeX2 derivatives are able to yield such bonds. Significant cooperative effects between the new halogen bond and the beryllium bond reinforce the strength of both noncovalent interactions. 相似文献
106.
A computational study of model halogen-bonded FCl?…?YZ dimers and FX′?…?FCl?…?YZ (FX′ = FH, FCl, F2Be; YZ = BF, CO, N2) trimers was undertaken at the MP2/6-311++G (2d, 2p) level of theory. Three different trimer arrangements are possible and the cooperative effect of hydrogen-, halogen- and beryllium-bonding in each of these trimers was assessed relative to the FCl?…?YZ dimer. It was found that the beryllium bond has the largest cooperative effect, while the halogen bond has the smallest, with the hydrogen bond being intermediate between the other two interactions. Interesting trends in selected properties were identified and discussed. 相似文献
107.
以多电子原子精细结构哈密顿的球张量形式为基础,借助不可约张量理论,对铍原子1s22snp(n=2~6) 3p态精细结构(包括自旋-轨道相互作用、自旋-其它轨道相互作用和自旋-自旋相互作用)进行了具体地计算,并将计算结果与文献结果进行了比较,符合地较好.同时,计算了1s22snp(n=2~6)3p态精细结构参数A和B的值. 相似文献
108.
Abstract The volume compressions of a tantalum alloy, tungsten alloy, and beryllium oxide (BeO) have been derived from the measurements of axial shortenings of cylindrical specimens of these materials to 4.5 GPa at room temperature. These measurements were carried out in a solid pressure medium piston- cylinder apparatus. 相似文献
109.
110.
S. Yu. Gus’kov N. V. Zmitrenko Yu. E. Markushkin Yu. A. Merkul’ev 《Journal of Russian Laser Research》2007,28(2):148-162
The energetic characteristics of the compression and burning of targets with beryllium and beryllium deuteride shells are
compared. The characteristics considered include the hydrodynamic efficiency, the efficiency of energy transmission to the
thermonuclear fuel, and the gain factor found from numerical simulation using the ‘Diana’ one-dimensional mathematical code.
The calculations are carried out for direct-drive cryogenic laser targets with the ablator shells made of beryllium or beryllium
deuteride with parameters corresponding to the third harmonic of energy of the neodymium-laser radiation with a pulse energy
of 1–3 MJ. It is proved that the gain of beryllium hydride targets can be brought to the level of beryllium targets due to
variations in the geometrical parameters of BeD2 targets. It is shown that the fission of BeD2 or BeDT ablators in reactor-scale targets could significantly contribute to the final thermonuclear yield.
__________
Translated from Preprint No. 20 of the P. N. Lebedev Physical Institute, Moscow (2001). 相似文献