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141.
Petra Hoffman Siegfried Hünig Leonhard Walz Karl Peters Hans-Georg von Schnering 《Tetrahedron》1995,51(48):13197-13216
Azo compounds 1 and 3 containing a CC-double bond in a parallel but distant position are quatemized by Me3OBF4 to 1,MeBF4 and 3,MeBF4, whereas MeI produces the cage compounds 2,HX and 4,HX. These [3+2] cycloadducts also are quantitatively formed from 1,MeBF4 and 3,MeBF4 with catalytic amounts of azo compounds. Intermolecular [3+2] cycloadditions occur with a mixture of DBH (5) or DBO (8), MeI and a variety of alkenes (→ HI) salts of (6, 7, 9 — 12). The intermediate azomethineimines, if stabilized by a fluorenylidene group, can be isolated (20, 22,24), but not, however, in the presence of a close parallel CC-bond (25 → 26). 相似文献
142.
von Euler H Olsson JM Hultenby K Thörne A Lagerstedt AS 《Bioelectrochemistry (Amsterdam, Netherlands)》2003,59(1-2):89-98
INTRODUCTION: Electrochemical treatment (EChT) has been taken under serious consideration as being one of several techniques for local treatment of malignancies. The advantage of EChT is the minimal invasive approach and the absence of serious side effects. Macroscopic, histopathological and ultra-structural findings in liver following a four-electrode configuration (dog) and a two-electrode EChT design (dog and rat) were studied. MATERIALS AND METHODS: 30 female Sprague-Dawley rats and four female beagle dogs were studied with EChT using Platinum:Iridium electrodes and the delivered dose was 5, 10 or 90 C (As). After EChT, the animals were euthanized. RESULTS: The distribution of the lesions was predictable, irrespective of dose and electrode configuration. Destruction volumes were found to fit into a logarithmic curve (dose-response). Histopathological examination confirmed a spherical (rat) and cylindrical/ellipsoidal (dog) lesion. The type of necrosis differed due to electrode polarity. Ultra-structural analysis showed distinct features of cell damage depending on the distance from the electrode. Histopathological and ultra-structural examination demonstrated that the liver tissue close to the border of the lesion displayed a normal morphology. CONCLUSIONS: The in vivo dose-planning model is reliable, even in species with larger tissue mass such as dogs. A multi-electrode EChT-design could obtain predictable lesions. The cellular toxicity following EChT is clearly identified and varies with the distance from the electrode and polarity. The distinct border between the lesion and normal tissue suggests that EChT in a clinical setting for the treatment of liver tumours can give a reliable destruction margin. 相似文献
143.
The gas-phase infrared absorption spectra of neutral benzyl and tropyl, isomers of formula C7H7, have been measured in the 400-1800 cm-1 spectral region. In addition, a quantum chemical calculation has been performed to model the infrared spectra. For the benzyl radical, the theory shows satisfactory overlap with the experiment, although vibrations involving the CH2 group might be anharmonic. The tropyl radical, which is subject to the Jahn-Teller effect, seems well modeled for the out-of-plane vibrational modes, but less so for the in-plane vibrational modes. 相似文献
144.
Jayaraman Chandrasekhar Eluvathingal D. Jemmis Paul von Ragué Schleyer 《Tetrahedron letters》1979,20(39):3707-3710
The 3,5-dehydrophenyl cation (I), which may represent the structure of C6H3 ions observed mass spectroscopically, illustrates : two different aromatic systems in orthogonal planes. 相似文献
145.
The aim of this work was the preparation of enantiomerically pure bis(pinene-bipyridine) ligands containing the ferrocenyl moiety. Several such ligands (1-3) were synthesized and completely characterized. These molecules can be diastereoselectively deprotonated at the acidic methylene group of the pinene moiety using a strong and sterically hindered base such as LDA. Subsequent reaction of the formed anion with alkyl halides yield the family of C(2)-symmetric enantiopure compounds (1a-c). Copper(I), silver(I), or zinc(II) complexes with several ligands (C1-C8) were prepared and structurally characterized in the solid state and in solution. Self-assembled helical species are formed in several cases. It became evident that the chiral groups present in the ligand do not completely determined the helical configuration of the assemblages. Diastereoselectivity is thus not complete with this type of ligands, contrary to other, similar ligands studied before. 相似文献
146.
The spinels of the system LixMn1?xV2O4 (0 ? x ? 1) have been prepared at 700–750°C from LiV2O4 and MnV2O4. The lattice constants decrease linearly with increasing x. In the region x>0.75, the d-electrons of V should be delocalized as the VV distances are lower than the critical VV separation of 2.94 Å. Experimentally, the samples with x>0.6 show no IR absorption bands and the Seebeck coefficient is near zero. The Seebeck coefficient can be described with a model of intermediate polarons and can be expressed by the equation . 相似文献
147.
The structure and configuration of harpagoside, a bitter principle from the roots of Harpagophytum procumbens DC, have been elucidated by degradation reactions and NMR. spectra. The hitherto uncertain position of a secondary hydroxyl group could be assigned to C-6 of the aglycone moiety. As earlier postulated, harpagoside ( 1 ) as well as its saponification product, harpagide ( 12 ), belong to a series of natural enol ethers known as iridoids. 相似文献
148.
Wolfgang Hnle Walter Schmettow Karl Peters Jen‐Hui Chang Hans Georg von Schnering 《无机化学与普通化学杂志》2004,630(12):1858-1862
The novel ternary polyphosphides M4P21I (M = K, Rb) have been synthesized from the elements in single crystalline form, representing further examples for the formation of mixed crystals between simple salts and binary phosphides. They form as ruby‐red platelets and dark‐red prisms, respectively, and are only slightly sensitive to moisture and oxygen. The compounds are isotypic (Ccmm (no 63); Z = 4; oP104; K4P21I: a = 12.853Å; b = 21.795Å; c = 9.748Å; 1168 hkl, R = 0.033; Rb4P21I: a = 13.281Å; b = 21.868Å; c = 9.771Å; 777 hkl, R = 0.053) and feature corrugated 2D networks formed from two different types of polymerized P7 units. The networks form large cavities filled by M+ and I‐ ions. Zigzag chains of condensed trigonal M6 prisms, centered by the I‐ anions, separate the polyphosphide nets. The mean homoatomic P‐P bond length (d = 2.216Å) corresponds to a P‐P single bond. However, the individual P‐P distances vary with position and function (2.126 ‐ 2.247Å) and these are compared with those of the isolated P21‐3 anion. 相似文献
149.
High-resolution 29Si NMR spectra of zunyite Si5Al13O20 (OH,F)18Cl have been studied by magic-angle sample spinning in combination with high-power proton decouplina and polarization transfer. The isotropic 29Si chemical shift depends mainly on the number of Si-O-Si bridges and the bond angles in these bridges connecting the different SiO4 tetrahedra. 相似文献
150.
Renate Borowski Dieter Rehder Klaus von Deuten 《Journal of organometallic chemistry》1981,220(1):45-54
Photo-reaction between the ligands Ph2ECH2EPh2 (E = P: dppm, E = As: dpam, E = Sb: dpsm), L, and the vanadium complexes η5-C5H5V(CO)4 and [Et4N][V(CO)6] yields monosubstituted mononuclear (dpsm) and dinuclear, ligand-bridged complexes (dpam, dpsm). With dppm, the final products are disubstituted chelate complexes, but monosubstituted mono- and dinuclear species are formed as intermediates.The shielding of the 51V nucleus decreases in the series dpsm > dppm > dpam and {M(CO)n} > {M(CO)n?1} L > {M(CO)n?1}2μ-L > {M(CO)n?2}dppm ({M(CO)n}[V(CO)6]?, η5-C5H5V(CO)4). The half-widths of the NMR signals are greater for dinuclear than for mononuclear complexes.The crystal and molecular structures of η5-C5H5V(CO)3As2Ph4 have been determined. The compound crystallizes in the space group P21/c with a = 1347.8, b = 1020.0, c = 2085.2 pm and β = 82.3°. Due to steric crowding, the 51V shielding is low composed to that of {η5-C5H5V(CO)3}2μ-dpam. 相似文献