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31.
Claude Belin Monique Tillard Laurent Spina Yong Zhong Jia 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(5):i51-i53
Aluminium germanium lithium, AlGeLi, crystallizes in two cubic dimorphs. The structure of the F3m form, already inferred from powder data, has been confirmed by both powder and single‐crystal X‐ray diffraction studies. The second dimorph, not previously identified, adopts a disordered centrosymmetric structure with space group Fmm. 相似文献
32.
Five cellulase components were identified and purified in one step from Streptomyces strain A20 using electroendosmotic preparative electrophoresis. By this procedure up to 18 mg of protein mixture could be loaded on the column, with an estimated recovery of 60-70% of total activity; activity and protein recovery could be estimated 32% and 47% respectively, if only activity peaks were considered. In comparison to other purification methods, this technique results in high protein recovery and resolution of applied samples. 相似文献
33.
本文报导了采用氩离子激光器来泵浦Pr3+:YLF晶体,应用声光调制器实现了主动锁模;同时应用振动─高反射平面镜也实现了被动锁模,两种锁模均得到了ps光脉冲.据作者了解这是这种晶体材料的第一次锁模运转. 相似文献
34.
We present a general method for the linear least-squares solutionof overdetermined and underdetermined systems. The method isparticularly efficient when the coefficient matrix is quasi-square,that is when the number of rows and number of columns is almostthe same. The numerical methods for linear least-squares problemsand minimum-norm solutions do not generally take account ofthis special characteristic. The proposed method is based onLU factorization of the original quasi-square matrix A, assumingthat A has full rank. In the overdetermined case, the LU factorsare used to compute a basis for the null space of AT. The right-handside vector b is then projected onto this subspace and the least-squaressolution is obtained from the solution of this reduced problem.In the case of underdetermined systems, the desired solutionis again obtained through the solution of a reduced system.The use of this method may lead to important savings in computationaltime for both dense and sparse matrices. It is also shown inthe paper that, even in cases where the matrices are quite small,sparse solvers perform better than dense solvers. Some practicalexamples that illustrate the use of the method are included. 相似文献
35.
The lithium–aluminum–silver ternary system has been investigated and two new phases Li6.98Al4.15Ag0.87 and LiAlAg2 were characterized using both powder and single crystal X-ray diffraction techniques. These phases crystallize in the cubic system, space group (a=6.344(1), 6.3124(5) Å), they, respectively, display the Pearson's cF12- and cF16-type structural arrangements. Compared to Li2AlAg, the only phase in the system reported so far, the structure of Li6.98Al4.15Ag0.87 is disordered owing to atomic substitutions and contains a full site vacancy. Band structures and densities of states of Li6.98Al4.15Ag0.87, LiAlAg2 and Li2AlAg have been calculated by a first principle pseudopotential method using the plane-wave basis CASTEP package. 相似文献
36.
Li13Cu6Ga21 crystallizes in a cubic structure, space group Im3, with a = 13.568(2) Å, Z = 4. Diffraction data were collected on a NONIUS CAD 4 diffractometer in the range 4 ≤ 2θ ≤ 50° (MoKα radiation). The structure was solved by direct methods and refined by full-matrix least-squares to a final R(F) = 0.033 for 346 independent reflections with I> 3σ(I). Li13Cu6Ga21 presents an interesting structure composed of Samson's polyhedral clusters (104 atoms) linked to each other through smaller junction polyhedral clusters (truncated tetrahedra and hypho-13-vertex polyhedra) containing lithium atoms in their centers. 相似文献
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38.
Ribet JP Pena R Maurel JL Belin C Tillard M Vacher B Bonnaud B Colpaert F 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,62(1-3):353-363
{[1-(3-Chloro-4-fluorobenzoyl)-4-fluoropiperidin-4yl]methyl}[(5-methylpyridin-2-yl)methyl]amine, fumaric acid salt (C(20)H(22)ClF(2)N(3)O, C(4)H(4)O(4)) (1) was synthesized and characterized by the complete (1)H, (13)C and (19)F NMR analyses. The conformation of the piperidin ring, in the solution state, was particularly studied from the coupling constants determined by recording a double-quantum filtered COSY experiment in phase-sensitive mode. (1)H NMR line-shape analysis was used, at temperatures varying between -5 and +60 degrees C, to determine the enthalpy of activation of the rotational barrier around the CN bond. Compound 1 crystallizes in the triclinic space group P1 with a=8.517(3) Angstrom, b=12.384(2) Angstrom, c=12.472(3) Angstrom, alpha=70.88(2) degrees, beta=82.04(2) degrees, gamma=83.58(2) degrees. The results strongly indicate that the solid and solution conformations are similar. Thermal stability and phases transitions were investigated by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). Furthermore polymorphism screening was studied from recrystallization of 1 performed in seven solvents and by slurry conversion in water. The X-ray powder diffraction (XRPD) and differential scanning calorimetry results suggested that 1 crystallizes into one crystalline form which melts at 157 degrees C (DeltaH=132 J g(-1)). 相似文献
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