全文获取类型
收费全文 | 229篇 |
免费 | 9篇 |
专业分类
化学 | 170篇 |
力学 | 12篇 |
数学 | 21篇 |
物理学 | 35篇 |
出版年
2023年 | 4篇 |
2022年 | 2篇 |
2021年 | 12篇 |
2020年 | 5篇 |
2019年 | 8篇 |
2018年 | 7篇 |
2017年 | 5篇 |
2016年 | 12篇 |
2015年 | 8篇 |
2014年 | 5篇 |
2013年 | 9篇 |
2012年 | 10篇 |
2011年 | 14篇 |
2010年 | 7篇 |
2009年 | 7篇 |
2008年 | 6篇 |
2007年 | 5篇 |
2006年 | 9篇 |
2005年 | 7篇 |
2004年 | 10篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1999年 | 2篇 |
1998年 | 5篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1993年 | 2篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1984年 | 2篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 5篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1969年 | 2篇 |
1966年 | 1篇 |
1907年 | 2篇 |
1890年 | 1篇 |
排序方式: 共有238条查询结果,搜索用时 15 毫秒
91.
Towards Structural‐Functional Mimics of Acetylene Hydratase: Reversible Activation of Acetylene using a Biomimetic Tungsten Complex
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
M. Sc. Lydia M. Peschel Prof. Dr. Ferdinand Belaj Prof. Dr. Nadia C. Mösch‐Zanetti 《Angewandte Chemie (International ed. in English)》2015,54(44):13018-13021
The synthesis and characterization of a biomimetic system that can reversibly bind acetylene (ethyne) is reported. The system has been designed to mimic catalytic intermediates of the tungstoenzyme acetylene hydratase. The thiophenyloxazoline ligand S‐Phoz (2‐(4′,4′‐dimethyloxazolin‐2′‐yl)thiophenolate) is used to generate a bioinspired donor environment around the W center, facilitating the stabilization of W–acetylene adducts. The featured complexes [W(C2H2)(CO)(S‐Phoz)2] ( 2 ) and [WO(C2H2)(S‐Phoz)2] ( 3 ) are extremely rare from a synthetic and structural point of view as very little is known about W–C2H2 adducts. Upon exposure to visible light, 3 can release C2H2 from its coordination sphere to yield the 14‐electron species [WO(S‐Phoz)2] ( 4 ). Under light‐exclusion 4 re‐activates C2H2 making this the first fully characterized system for the reversible activation of acetylene. 相似文献
92.
Heat transfer in complex physical situations such as nucleate boiling, quenching and dropwise condensation is strongly affected by the presence of a liquid–vapor–solid triple contact line, where intense energy transfer and phase change occur. A novel experimental technique for the detection of the liquid–vapor–solid line in these situations is presented. The technique is based on high-speed infrared (IR) thermometry through an IR-transparent silicon wafer heater; hence the name DEPIcT, or DEtection of Phase by Infrared Thermometry. Where the heater surface is wet, the IR camera measures the temperature of the hot water in contact with the heater. On the other hand, where vapor (whose IR absorptivity is very low) is in contact with the heater, the IR light comes from the cooler water beyond the vapor. The resulting IR image appears dark (cold) in dry spots and bright (hot) in wetted area. Using the contrast between the dark and bright areas, we can visualize the distribution of the liquid and gas phases in contact with the heater surface, and thus identify the liquid–vapor–solid contact line. In other words, we measure temperature beyond the surface to detect phases on the surface. It was shown that even small temperature differences (∼1 °C) can yield a sharp identification of the contact line, within about 100 μm resolution. DEPIcT was also shown to be able to detect thin liquid layers, through the analysis of interference patterns. 相似文献
93.
Jacopo Bellazzini Gaetano Siciliano 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2011,6(2):267-280
We prove the existence of orbitally stable standing waves with prescribed L 2-norm for the following Schrödinger-Poisson type equationwhen \({p\in \left\{ \frac{8}{3}\right\}\cup (3,\frac{10}{3})}\). In the case \({3 < p < \frac{10}{3}}\), we prove the existence and stability only for sufficiently large L 2-norm. In case \({p=\frac{8}{3}}\), our approach recovers the result of Sanchez and Soler (J Stat Phys 114:179–204, 2004) for sufficiently small charges. The main point is the analysis of the compactness of minimizing sequences for the related constrained minimization problem. In the final section, a further application to the Schrödinger equation involving the biharmonic operator is given.
相似文献
$i\psi_{t}+ \Delta \psi - (|x|^{-1}*|\psi|^{2}) \psi+|\psi|^{p-2}\psi=0 \quad \rm{in} \quad \mathbb R^{3},$
94.
Fading memory is a distinguishing characteristic of viscoelastic solids. Its assessment is often achieved by measuring the stress due to harmonic strain histories at different frequencies: from the experimental point of view, the storage and loss moduli are, hence, introduced. On the other side, the mathematical modeling of viscoelastic materials is usually based on the consideration of a kernel function whose decay rate is sufficiently fast. For several different solid materials, we have collated experimental evidence showing an high sensitivity to frequency variations of both the storage and loss moduli. By contrast, we prove that the commonly employed viscoelastic kernels (Prony series, continuous kernel, etc.) cannot reproduce this experimental behavior, as the resulting frequency sensitivity of the storage modulus is always zero when assessed at low frequency. This leads to identification problems of the material parameters which are strongly ill conditioned. However, we identify the specific kernel property which is responsible for this misbehavior: the long-term material memory must not decrease too fast. Some viscoelastic kernels, showing the correct memory??s rate of decay, are introduced and their improved ability to match the experimental data analyzed. 相似文献
95.
We study structural properties of the q-color Potts field theory which, for real values of q, describes the scaling limit of the random cluster model. We show that the number of independent n-point Potts spin correlators coincides with that of independent n-point cluster connectivities and is given by generalized Bell numbers. Only a subset of these spin correlators enters the determination of the Potts magnetic properties for q integer. The structure of the operator product expansion of the spin fields for generic q is also identified. For the two-dimensional case, we analyze the duality relation between spin and kink field correlators, both for the bulk and boundary cases, obtaining in particular a sum rule for the kink-kink elastic scattering amplitudes. 相似文献
96.
Light transport in superdiffusive media of finite size is studied theoretically. The intensity Green's function for a slab geometry is found by discretizing the fractional diffusion equation and employing the eigenfunction expansion method. Truncated step length distributions and complex boundary conditions are considered. The profile of a coherent backscattering cone is calculated in the superdiffusion approximation. 相似文献
97.
Beatrice Rubin Jacopo Manso Halenya Monticelli Loris Bertazza Marco Redaelli Francesca Sensi 《Natural product research》2019,33(11):1646-1649
Oregano (Origanum vulgare L.) is a common aromatic plant used in Mediterranean and Asian Regions for treating respiratory diseases, painful menstruation, rheumatoid arthritis, etc. Recently its role as an anticancer plant has been suggested, although oregano has been never evaluated into adrenocortical tumour cell models. This study analysed for the first time the anticancer effects of a crude extract of wild mountain oregano (Origanum vulgare L.) in SW13 and H295R cell lines. The crude extract was characterised by GC/MS and the toxic effects of oregano were first analysed by brine shrimp lethality assay. Our findings demonstrated that oregano decreased cell viability, survival, modified cell cycle and induced cell death (through necrotic process) and that the effects can be attributed to a blockade of MAPK and PI3 K/Akt pathways. These results suggest that oregano extract exerts anticancer activities in adrenocortical tumour cell lines, providing evidence for further research in higher models. 相似文献
98.
Geoffrey Schwertz Andrea Zanetti Marllon Nascimento de Oliveira Mario Andrès Gomez Fernandez Fabienne Dioury Janine Cossy Zacharias Amara 《Tetrahedron》2019,75(6):743-748
Amorphadiene is a natural product involved in the biosynthesis of the antimalarial drug artemisinin. A convenient four-step synthesis of amorphadiene, starting from commercially available dihydroartemisinic acid, is reported. The targeted molecule is isolated with an overall yield of 85% on a multi-gram scale in four steps with only one chromatography. 相似文献
99.
Diamond James Profili Jacopo Hamdan Ahmad 《Plasma Chemistry and Plasma Processing》2019,39(6):1483-1498
Plasma Chemistry and Plasma Processing - Plasma in- or in-contact-with liquid is an emerging technology that has high potential for use in liquid treatment applications. Due to the simultaneous... 相似文献
100.
Marco Zanetti Giovanni Camino Peter Reichert Rolf Mülhaupt 《Macromolecular rapid communications》2001,22(3):176-180
The thermal degradation behaviour of nanocomposites based upon poly(propylene)/organoclay, modified with protonated octadecyl amine (C18) in comparison to that of non‐exfoliated microcomposites based upon organoclay, modified with protonated butyl amine (C4), was studied by thermogravimetry. In the case of the nanocomposite, the temperature at which volatilisation occurs increases as compared of the microcomposite. Moreover, the thermal oxidation process of the polymer is strongly slowed down in the nanocomposite with high char yield both by a physical barrier effect, enhanced by ablative reassembling of the silicate, and by a chemical catalytic action due to the silicate and to the strongly acid sites created by thermal decomposition of the protonated amine silicate modifier. 相似文献