全文获取类型
收费全文 | 297篇 |
免费 | 14篇 |
专业分类
化学 | 156篇 |
晶体学 | 1篇 |
力学 | 19篇 |
数学 | 83篇 |
物理学 | 52篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 5篇 |
2020年 | 4篇 |
2019年 | 6篇 |
2018年 | 14篇 |
2017年 | 5篇 |
2016年 | 10篇 |
2015年 | 15篇 |
2014年 | 17篇 |
2013年 | 13篇 |
2012年 | 17篇 |
2011年 | 22篇 |
2010年 | 11篇 |
2009年 | 15篇 |
2008年 | 14篇 |
2007年 | 10篇 |
2006年 | 15篇 |
2005年 | 9篇 |
2004年 | 6篇 |
2003年 | 8篇 |
2002年 | 2篇 |
2001年 | 7篇 |
2000年 | 5篇 |
1999年 | 7篇 |
1998年 | 5篇 |
1997年 | 6篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 8篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1972年 | 1篇 |
1971年 | 2篇 |
排序方式: 共有311条查询结果,搜索用时 0 毫秒
1.
Unstable form changing (click) of an arched TiNi strip annealed at 773 K is investigated. After the annealing, the strip is
placed into the grips of a deforming machine and is transferred to the martensitic state by bending in the direction opposite
to its initial bend. Subsequent heating of the strip, which carries it to the austenitic state, is accompanied by a click
under the conditions of constrained form changing. Analysis of the martensitic deformation in terms of the theory of diffuse
martensitic transformations makes it possible to establish the conditions under which the form changing process becomes unstable. 相似文献
2.
3.
Marina A. Khokhlova Marat O. Gallyamov Alexei R. Khokhlov 《Colloid and polymer science》2012,290(15):1471-1480
Chitosan macromolecules can be dissolved in water saturated with CO2 under high pressure, i.e. in carbonic acid. This unique biocompatible solvent with acidity regulated by the variation of applied CO2 pressure is rather promising for biomedical applications. In this work the main features of deposition of chitosan structures on the model substrate from solutions in this media were examined. After deposition on the mica surface, the obtained structures have been successfully visualised by atomic force microscopy (AFM). It has been found out that they adsorb as rather peculiar elongated objects with an average length of about 70?nm. Such conformations are believed to appear due to amphiphilic nature of chitosan semiflexible chains in agreement with recent theoretical findings. The well-defined geometry of the elongated monodispersed structures allows them to demonstrate some elements of liquid crystalline-like ordering. 相似文献
4.
Marat Gafurov Vasyl Denysenkov Mark J. Prandolini Thomas F. Prisner 《Applied magnetic resonance》2012,43(1-2):119-128
The temperature dependence of the water-proton dynamic nuclear polarization (DNP) enhancement from Fremy’s salt nitroxide radicals was measured in a magnetic field of 9.2?T (corresponding to 260?GHz microwave (MW) and 392?MHz NMR frequencies) in the temperature range of 15–65?°C. The temperature could be determined directly from the proton NMR line shift of the sample. Very high DNP enhancements of ?38 (signal integral) or ?81 (peak intensity) could be achieved with a high-power gyrotron MW source. The experimental findings are compared with classical Overhauser theory for liquids, which is based on the translational and rotational motion of the molecules and with molecular dynamics calculations of the coupling factor. 相似文献
5.
Umbilic points--singular points of curvature characterized by a fractional topological charge q=+/-1/2--are the most numerous of all special points in the landscape of random optical fields (speckle patterns), outnumbering maxima, minima, saddle points, and optical vortices. To the best of our knowledge, we present the first experimental evidence that positive and negative umbilic points screen one another. Theory predicts that in the absence of screening the charge variance in a bounded region is proportional to the area of the region, whereas in the presence of screening the variance is drastically reduced and is proportional to the perimeter. Our data confirm this latter prediction and provide the first estimates of the screening lengths for umbilic points of the intensity and of the amplitude (field modulus). 相似文献
6.
Vladimir O. Abramov Marat S. Mullakaev Anna V. Abramova Igor B. Esipov Timothy J. Mason 《Ultrasonics sonochemistry》2013,20(5):1289-1295
A new method for the ultrasonic enhancement of oil recovery from failing wells is described. The technology involves lowering a source of power ultrasound to the bottom of the well either for a short treatment before removal or as a permanent placement for intermittent use. In wells where the permeability is above 20 mD and the porosity is greater than 15% ultrasonic treatment can increase oil production by up to 50% and in some cases even more. For wells of lower permeability and porosity ultrasonic treatment alone is less successful but high production rates can be achieved when ultrasound is applied in conjunction with chemicals. An average productivity increase of nearly 3 fold can be achieved for this type of production well using the combined ultrasound with chemical treatment technology. 相似文献
7.
Colson S Konczykowski M Gaifullin MB Matsuda Y Gierłowski P Li M Kes PH Van Der Beek CJ 《Physical review letters》2003,90(13):137002
Vortex thermal fluctuations in heavily underdoped Bi(2)Sr(2)CaCu(2)O(8+delta) (T(c)=69.4 K) are studied using Josephson plasma resonance. From the zero-field data, we obtain the c-axis penetration depth lambda(L,c)(0)=230+/-10 micrometer and the anisotropy ratio gamma(T). The low plasma frequency allows us to study phase correlations over the whole vortex solid state and to extract a wandering length r(w) of vortex pancakes. The temperature dependence of r(w) as well as its increase with dc magnetic field is explained by the renormalization of the vortex line tension by the fluctuations, suggesting that this softening is responsible for the dissociation of the vortices at the first order transition. 相似文献
8.
Marat K. Ibrayev Oralgazy A. Nurkenov Zhanar B. Rakhimberlinova Altynaray T. Takibayeva Irina V. Palamarchuk Dastan M. Turdybekov Assel A. Kelmyalene Ivan V. Kulakov 《Molecules (Basel, Switzerland)》2022,27(21)
The interaction results of 1,2-dibromo-3-isothiocyanatopropane with some pyrazoles as well as cytisine and salsoline alkaloids were presented in this paper. It was shown that the reaction resulted in one one-step and rather mild method for the preparation of the corresponding 1,3-thiazoline bromomethyl derivatives. The yield of this reaction was affected by the presence of a base and an order in which reagents were added. Molecular docking of the synthesized 1,3-thiazoline derivatives for putative antibacterial activity was carried out using the penicillin-binding target protein (PBP4) of the bacteria E. coli “Homo sapiens” and S. aureus “Homo sapiens” as an example. Molecular docking demonstrated that the compounds had insignificant binding energies at the level of selected reference drugs (Cephalotin and Chloramphenicol). The presence of natural alkaloids in the structure of thiazoline derivatives somewhat increased the affinity of these substrates for target proteins selected. 相似文献
9.
In this article, we present a Python‐based library of high quality semi‐global potential energy surfaces for 50 polyatomic molecules with up to six atoms. We anticipate that these surfaces will find widespread application in the testing of new potential energy surface construction algorithms and nuclear ro‐vibrational structure theories. To this end, we provide the ability to generate the energy derivatives required for Taylor series expansions to sixth order about any point on the potential energy surface in a range of common coordinate systems, including curvilinear internal, Cartesian, and normal mode coordinates. The PyPES package, along with FORTRAN, C, MATLAB and Mathematica wrappers, is available at http://sourceforge.net/projects/pypes-lib . © 2015 Wiley Periodicals, Inc. 相似文献
10.
Murdachaew G Valiev M Kathmann SM Wang XB 《The journal of physical chemistry. A》2012,116(9):2055-2061
Alkali metal cations often show pronounced ion-specific interactions and selectivity with macromolecules in biological processes, colloids, and interfacial sciences, but a fundamental understanding about the underlying microscopic mechanism is still very limited. Here we report a direct probe of interactions between alkali metal cations (M(+)) and dicarboxylate dianions, (-)O(2)C(CH(2))(n)CO(2)(-) (D(n)(2-)) in the gas phase by combined photoelectron spectroscopy (PES) and ab initio electronic structure calculations on nine M(+)-D(n)(2-) complexes (M = Li, Na, K; n = 2, 4, 6). PES spectra show that the electron binding energy (EBE) decreases from Li(+) to Na(+) to K(+) for complexes of M(+)-D(2)(2-), whereas the order is Li(+) < Na(+) ≈ K(+) when M(+) interacts with a more flexible D(6)(2-) dianion. Theoretical modeling suggests that M(+) prefers to interact with both ends of the carboxylate -COO(-) groups by bending the flexible aliphatic backbone, and the local binding environments are found to depend upon backbone length n, carboxylate orientation, and the specific cation M(+). The observed variance of EBEs reflects how well each specific dicarboxylate dianion accommodates each M(+). This work demonstrates the delicate interplay among several factors (electrostatic interaction, size matching, and strain energy) that play critical roles in determining the structures and energetics of gaseous clusters as well as ion specificity and selectivity in solutions and biological systems. 相似文献