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741.
Study on the improvement of crystallization of high density polyethylene through dynamic packing injection molding 下载免费PDF全文
To better understand the effect of high‐density polyethylene on crystal morphology under the shear stress field, the dynamic packing injection molding was used to prepare the oriented pure polyethylene. In this present work, dynamic packing injection molding can exert a successive shear field on the melt in the mold cavity during packing stage. The structure of the samples was characterized through differential scanning calorimetry, wide‐angle X‐ray diffraction, and scanning electron microscopy. The oriented lamellae perpendicular to the flow direction can be formed. Oscillating stress between the lower and upper critical values can induce shish forming. The shish kebabs can be generated through sufficient relaxation led by slow cooling and suitable shear. We roughly discuss the relationship between the shear rate and crystal shape. Our results set up a method to reinforce polymer parts by regulating morphology and structure which can be used to do practical processing condition. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
742.
S. Fakirov Z. Sarac T. Anbar B. Boz I. Bahar M. Evstatiev A. A. Apostolov J. E. Mark A. Kloczkowski 《Colloid and polymer science》1996,274(4):334-341
This study is an extension of previous work on cellulosics [(1994)Colloid Polym Sci 272: 284, 393] that showed that unusually good mechanical properties can be obtained by drying a swollen network of semirigid chains in a state of strain. This novel approach is applied in this investigation to gelatin, because of its attractive environmental characteristics but poor mechanical properties in the unmodified form. Since drawing of non-crosslinked gelatin is not practical, crosslinking by formaldehyde was used, followed by swelling, drawing and drying at fixed length. Mechanical tests were performed in static and dynamic modes. In this way improvements of Young's modulusE, and stress at break
b were determined as a function of gelatin concentration during drying. An increase inE and
b up to 2–3 times, and in the dynamic modulusE up to 6 times, was obtained when the draw ratio reached 4–5, after whichE, E, and
b were found to decrease. Such behavior is explained by the highest orientation being achieved at =4–5, as proved by x-ray analysis. At =10–20 the orientation is lost due to relaxation of chain segments, which is preceded by partial destroying of the network structure (chemical and physical), possibly via chain scission, but probably mostly by the pulling out of chains from crystallites. In any case, the mechanical properties become poor again.The improvements reported above were referred to the undrawn but crosslinked gelatin. Compared to the starting isotropic non-crosslinked material, the improvement is slightly higher. The observation that the improvements are less than those obtained for the cellulosics is explained by the coexistence of interpenetrating chemical and physical networks, which is typical of gelatin. This structural feature drastically reduces the orientability of the chains and the improvements that can be expected in the mechanical properties. 相似文献
743.
The dissociative electron attachment process for CHCl3 at different electric field have been studied with nitrogen as drift and carrier gas using corona discharge ionization source ion mobility spectrometry (CD-IMS). The corresponding electron attachment rate constants varied from 1.26×10-8 cm3/(molecules s) to 8.24×10-9 cm3/(molecules s) as the electric field changed from 200 V/cm to 500 V/cm. At a fixed electric field in the drift region,the attachment rate constants are also detected at different sample concentration. The ion-molecule reaction rate constants for the further reaction between Cl- and CHCl3 are also detected, which indicates that the technique maybe becomes a new method to research the rate constants between ions and neural molecules. And the reaction rate constants between Cl- and CHCl3 are the first time detected using CD-IMS. 相似文献
744.
B3L YP/6-31 g(d,p)method was used to calculate the lithium and sodium affinities of n-alkyl fluoride. These affinities were found to obey the Holmes relationship, i.e.they correlate linearly with the quotient n/(n 1), where n is the number of carbon atoms in the alkyl chain. From the correlation the limiting values of lithium and sodium affinities for very long alkyl chain were predicted to be-153.3kJ/mol and -108.4kJ/mol,respectively. 相似文献
745.
746.
In a discrete-time financial market setting, the paper relates various concepts introduced for dynamic portfolios (both in discrete and in continuous time). These concepts are: value preserving portfolios, numeraire portfolios, interest oriented portfolios, and growth optimal portfolios. It will turn out that these concepts are all associated with a unique martingale measure which agrees with the minimal martingale measure only for complete markets. 相似文献
747.
在建立微分线性空间基础上、引入向量外积和有向体积,找到了微分线性变换与有向体积之间的关系,由此给出了n重积分换元公式的一个简单证法. 相似文献
748.
Ali N. A. Koam 《代数通讯》2018,46(7):2947-2963
In this paper, our goal is to develop the equivariant version of Hochschild cohomology. In particular, we develop a cohomology theory for oriented algebras. 相似文献
749.
Ivanova EP Mitik-Dineva N Wang J Pham DK Wright JP Nicolau DV Mocanasu RC Crawford RJ 《Micron (Oxford, England : 1993)》2008,39(8):1197-1204
The attachment behaviour of Staleya guttiformis DSM 11458T on poly(tert-butyl methacrylate) (P(tBMA)) polymeric surfaces has been studied. The electrostatic charge of the S. guttiformis cell surface (measured as zeta potential via microelectrophoresis) was −43.18 mV. S. guttiformis cells appeared weakly hydrophilic as the water contact angle measured on lawns of bacterial cells was found to be 55 ± 4.9°. It was found that while attaching on P(tBMA) surfaces, S. guttiformis cells produced extracellular polymeric substances (EPS) as observed from atomic force microscopy (AFM) and scanning electron microscopy (SEM) analysis. The AFM high resolution imaging revealed the nano-topography of the ‘free’ (the EPS that is produced by the bacterial cells, but no longer directly attached to the cells) EPS associated on the cell surface and also found on P(tBMA) surface. The ‘free’ EPS exhibited granular structure with lateral dimensions of 30–50 nm and a vertical nano-roughness of 7–10 nm. Another type of the EPS secreted by S. guttiformis cells appeared as a hydogel substance, presumably polysaccharide that formed a biopolymer network that facilitated bacterial attachment. 相似文献
750.