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131.
Reported herein is an intramolecular 1,3-dipolar cycloaddition strategy for rapid entry into benzopyranopyrazoles (BPP) on water medium as “open flask chemistry” approach. The in situ generation of diazo functionality in two-step sequence from the appropriate alkylated salicylaldehydes undergoes smooth [3?+?2]-cycloaddition with unactivated alkynes/alkenes furnishing benzopyranopyrazoles in good yield. This methodology was also extended for the synthesis of pyrazole incorporated macrocycles. This cascade protocol involving water medium provides an atom-economical and environment friendly approach. 相似文献
132.
本文提出一种利用正、赝再现像,将物体的正、反两面信息复合在一起的全息术.在一张全息干板片上,可以同时看到物体的两面,增强立体效果和艺术感.文中介绍了原理、方法和结果. 相似文献
133.
134.
L.M. da Silva M.C. de Melo A.N. Medina F.G. Gandra 《Physica B: Condensed Matter》2009,404(19):3018-3020
We report on results of X-ray powder diffraction, magnetization and specific heat measurements of the pseudo-ternary (Ce1−xLax)PdIn2 system with x=0; 0.2; 0.4 and 0.6. The results show a linear increase of the unit cell volume and a reduction of the ferromagnetic transition as La content increases. The Debye temperature, Sommerfeld coefficient and crystal field parameters were estimated from specific heat data, and are found to be weakly dependent of the Ce concentration. Also, the variation of magnetic entropy at TC is only weakly dependent on x (ΔS≅0.92Rln2) indicating that TK/TC is approximately constant along the series. The TC and TK behaviors are explained by the variation of the exchange parameter due to the volume change when Ce is replaced by La. Our results indicate that the chemical pressure is the dominant effect rather than the chemical disorder for determining the physical proprieties of the (Ce1−xLax)PdIn2 system. 相似文献
135.
From a new magnetically diluted spinel oxide with composition Fe0.6Mg1.6Ni0.1Ti0.7O4 an as-prepared sample and one after reheating three times have been investigated with Mössbauer spectroscopy. The spectra of the as-prepared sample clearly show a typical superparamagnetic behaviour of magnetic clusters with diverging sizes. On the other hand, the reheated sample exhibits a sharp magnetic transition at 16 K. External-field Mössbauer measurements of the latter reveal spin canting to be exclusively present on the octahedral sites which disappears at the magnetic transition temperature. These results show that this spinel compound exhibits a transition to a spin-glass for which the random freezing only occurs on the octahedral sites. 相似文献
136.
A novel mixed‐tribridged dimolybdenum(I) compound [Bn4N][Mo2(μ‐SPh)2(μ‐Cl)(CO)6] (1) has been synthesized from the reaction of Mo2(CO)3(SPh)2 with BU4NCl. Compound 1 was characterized by IR, UV‐Vis and 1H, 13C, 95Mo NMR spectroscopic analyses. The electrochemical behavior was measured by cyclic voltammetry, indicating a quasi‐reversible two‐electron transfer in one step. The crystal structure determined by X‐ray crystallography shows that 1 contains a [Mo2(μ‐S)2(μ‐Cl)]? core with a planar Mo2S2unit and a Cl bridge. The Mo? Mo distance is 0.28709(7) nm, and the Mo‐Cl‐Mo angle is 66.44(4)°. A newface‐sharing bioctahedral structure is discussed. 相似文献
137.
Photoreduction of nitro compounds is accompanied by formation of various radical products that can react with the starting
nitro compound, thus causing deviation of the decomposition kinetics from the first-order kinetics with respect to the nitro
compound. The results of quantum chemical modeling of the reactions of nitro compounds with radicals and the pathways of further
transformations of radical adducts formed in the reactions are presented.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 202–206, February, 2006. 相似文献
138.
The interaction of diethyl (pyridyn-2-ylmethyl)phosphonate (2-pmpe) with Cu(NO3)2 · 6H2O leads to a partial hydrolysis of the starting ligand and formation of the compound of the formula Cu2(2-mpmpe)2(H2O)2(NO3)2, where 2-mpmpe = monoethyl (pyridyn-2-ylmethyl)phosphonate. The crystal and molecular structure of a copper(II) compound was determined by single X-ray diffraction method. Its structure consists of five-coordinated in distorted square planar geometry (CuNO4 chromophore) copper(II) ions doubly bridged by OPO from phosphonate. The Cu?Cu distance is 4.69 Å. The crystal packing is determined by the interdinuclear hydrogen bond system, which leads to a three-dimensional (3D) H-bonds network. The compound was characterized by infrared, ligand field, EPR spectroscopy, and magnetic studies. The magnetic properties of the title compound investigated over the 1.8–300 K, revealed the occurrence of a weak ferromagnetic coupling through phosphonate bridge (J = 1.86 cm−1) and interdimer superexchange coupling through H-bond network (zJ′ = −0.17 cm−1). Spectroscopic and magnetic properties are presented in the light of crystal structure. 相似文献
139.
This paper reports the syntheses and characterization of two phosphonate compounds with layered structures, namely, Mn2(2-C5H4NPO3)2(H2O) (1) and Zn(6-Me-2-C5H4NPO3) (2). In compound 1, double chains are found in which the {Mn2O2} dimers are linked by both aqua and O-P-O bridges. These double chains are connected through corner-sharing of {MnO5N} octahedra and {CPO3} tetrahedra, forming an inorganic layer. The pyridyl groups fill the inter-layer spaces. In compound 2, each {ZnO3N} tetrahedron is vertex-shared with three {CPO3} tetrahedra and vice versa, hence forming an inorganic honeycomb layer. The pyridyl groups reside between the layers. Magnetic studies show that weak antiferromagnetic interactions are mediated between the manganese ions in compound 1. Crystal data for 1: monoclinic, space group C2/c, , , , β=107.3(1)°. For 2: orthorhombic, space group Pbca, , , . 相似文献
140.
Raman Maksimenka Markus Margraf Juliane Khler Alexander Heckmann Christoph Lambert Ingo Fischer 《Chemical physics》2008,347(1-3):436-445
In this article we report a femtosecond time-resolved transient absorption study of a neutral organic mixed-valence (MV) compound with the aim to gain insight into its charge-transfer dynamics upon optical excitation. The back-electron transfer was investigated in five different solvents, toluene, dibutyl ether, methyl-tert-butyl ether (MTBE), benzonitrile and n-hexane. In the pump step, the molecule was excited at 760 nm and 850 nm into the intervalence charge-transfer band. The resulting transients can be described by two time constant. We assign one time constant to the rearrangement of solvent molecules in the charge-transfer state and the second time constant to back-electron transfer to the electronic ground state. Back-electron transfer rates range from 1.5 × 1012 s−1 in benzonitrile through 8.3 × 1011 s−1 in MTBE, around 1.6 × 1011 s−1 in dibutylether and toluene and to 3.8 × 109 s−1 in n-hexane. 相似文献