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951.
Alexander Filosa Heng Wang Wei‐Jian Li Wenjing Zhang Ellie Ngo Jonathan E. Piccolo Hai‐Bo Yang Xiaopeng Li 《中国化学》2019,37(11):1167-1173
Porphyrins have been widely used in the self‐assembly of metallo‐supramolecules. In this study, we introduced 2,2':6,2"‐terpyridine (tpy) into a porphyrin core to synthesize a tetratopic building block with multiple conformers. During the self‐assembly with Zn(II), such a mixture of conformers was able to form a discrete nanoprism with all building blocks in one conformation. Detailed characterizations, including NMR, ESI‐MS and traveling‐wave ion mobility‐mass spectrometry (TWIM‐MS), all supported the formation of the desired assemblies. AFM and TEM further confirmed the dimensions of assembled nanoprisms. Moreover, the photophysical properties of the ligands and complexes were noticeably different depending upon size and metal ion center. 相似文献
952.
A new approach to indolizines has been developed using a 5-endo-trig iodocyclization of allylic esters followed by isomerization and dehydroiodination facilitated by triethylamine at rt. This mild procedure enabled us to synthesize a number of highly substituted indolizines in good yields. 相似文献
953.
954.
Ge-132对小鼠H22肝癌移植瘤的实验研究证明:1.Ge-132对H22肝癌移植瘤有一定的抑制作用,300mg/kg体重剂量抑瘤率达到36.19%;2.增强机体的抗氧化作用,抑制脂质的过氧化物水平;3.促进免疫功能,当Ge-132和环磷酰胺联合使用时,可抵抗环磷酰胺的免疫抑制作用,而且并不减弱其抑制瘤作用。 相似文献
955.
Todorov E Evans M Lee S Rousseau R 《Chemistry (Weinheim an der Bergstrasse, Germany)》2001,7(12):2652-2662
The total electronic energies of the six electrons per atom (e per atom) alloys W, TaRe, HfOs, and YIr and the seven electrons per atom alloys Re, WOs, TaIr, HfPt, and YAu have been calculated in the local density approximation of density functional theory. When one considers common alloy structures such as atomically ordered variants of the body-centered cubic, face-centered cubic, or hexagonally closest packed structures and plots the total electronic energy as a function of the unit cell parameter, one finds for both the six and seven electrons per atom series energetic isosbestic points. An energetic isosbestic point corresponds to a critical value of the size parameter for which all members of the 6 or 7 e per atom series of compounds have nearly identical total electronic energy. Just as in spectroscopy, where the existence of such isosbestic points is the hallmark of two compounds present in the mixture, an energy isosbestic point implies there are just two separate energy curves. For both series it is found that the total electronic energy can be viewed as the weighted sum of a purely covalent term and a purely ionic term. Two semi-quantitative models are proposed to account for these two separate energies. In the first model the total energy is viewed as the sum of the elemental structural energy plus an ionic energy based on the Born-Mayer ionic model. In the second model one considers within the confines of mu2-Hückel theory the evolution of the total electronic energy as the Coulombic Hii integrals change in value. 相似文献
956.
据不同地貌、地质条件在30个县市按剖面、同步、随机取土壤样品372份.测定硒等微量元素含量.作等级相关分析显示。土壤硒含量与消化系统癌呈负相关关系.作相对危险度、剂量-效应及多因素分析,认为此负相关关系并非偶然现象. 相似文献
957.
Jin Ho Lee Heoung Woo Kim Pyong Ki Pak Hai Bang Lee 《Journal of polymer science. Part A, Polymer chemistry》1994,32(8):1569-1579
Functional group gradient surfaces where the density of functional groups changes gradually along the sample length were prepared. The functional group (? COOH, ? CONH2, and ? OH group) gradient surfaces were produced by the treatment of low-density PE sheets using a corona with gradually increasing power, followed by the graft copolymerization of acrylic acid and subsequent substitution reaction of carboxylic acid groups to amide or hydroxyl groups. The prepared gradient surfaces were characterized by the measurement of water contact angle, FTIR-ATR, and ESCA. The gradient surfaces prepared can be used to systematically investigate the interactions of biological or other species in terms of the surface functional groups and their density of polymeric materials. © 1994 John Wiley & Sons, Inc. 相似文献
958.
Alan E. Tonelli 《European Polymer Journal》1978,14(4):305
The Flory-Williams rotational isomeric state models describing the conformational characteristics of polyesters and polyamides are combined to calculate the dimensions of the alternating polyesteramide (PEA) of the type 6NT6. The calculated ratio of unperturbed dimensions is in excellent agreement with the value recently obtained from an intrinsic viscosity-molecular weight study of PEA. 相似文献
959.
The mass-transter characteristics of a two-phase system formed by mixing a fixed quantity (20 v/v%) of organic solvent with an aqueous ferricyanide electrolyte solution in an RDE system were studied. The Levich eqution, I1 = 0.62 nFACbD2/3v?1/6ω1/2, was found to be applicable to the two-phase system with only a minor modification in the angular velocity (ω) at Reynolds numbers between 3–5 × 104. The experimental results indicate that the interfacial tension is the most important variable for the two-phase system. One group of organic solvents with smaller interfacial tension, such as benzene or toluene, needs a modification of the Levich equation by replacing the observed angular velocity (ωo) with the true angular velocity (ωt) which was observed to be 1.1 times the observed angular velocity. For the other group with larger interfacial tension, such as n-hexane or cyclohexane, there is no need to modify the observed angular velocity. In other words, the Levich equation may be expressed as I1 = 0.65 nFACbD2/3v?1/6ω1/2 for two-phase solution if the interfacial tension is smaller than 37.0 dyne/cm. 相似文献
960.
Two new alkaloids, i.e., (2,3‐dihydro‐1‐oxo‐1H‐pyrrolo[1,2‐a]pyrrol‐7‐yl)methyl (2S*,3S*)‐3‐[(β‐D ‐glucopyranosyl)oxy]‐2‐hydroxy‐2‐(1‐methylethyl)butanoate ( 1 ) and 1,2‐dihydro‐8‐methoxy‐2‐oxoquinoline‐4‐carboxylic acid ( 2 ), were isolated from the alcoholic extract of the whole plant of Cynoglossum gansuense, together with twelve known compounds Their structures were characterized by means of spectroscopic methods, especially by 1H‐, 13C‐, and 2D‐NMR, as well as by HR‐MS experiments and comparison with literature data. 相似文献