全文获取类型
收费全文 | 936篇 |
免费 | 17篇 |
国内免费 | 1篇 |
专业分类
化学 | 524篇 |
晶体学 | 7篇 |
力学 | 19篇 |
数学 | 147篇 |
物理学 | 257篇 |
出版年
2021年 | 15篇 |
2020年 | 11篇 |
2019年 | 12篇 |
2018年 | 13篇 |
2017年 | 15篇 |
2016年 | 22篇 |
2015年 | 20篇 |
2014年 | 53篇 |
2013年 | 108篇 |
2012年 | 52篇 |
2011年 | 29篇 |
2010年 | 28篇 |
2009年 | 16篇 |
2008年 | 30篇 |
2007年 | 30篇 |
2006年 | 23篇 |
2005年 | 18篇 |
2004年 | 10篇 |
2003年 | 18篇 |
2002年 | 25篇 |
2001年 | 17篇 |
2000年 | 9篇 |
1999年 | 12篇 |
1998年 | 16篇 |
1997年 | 9篇 |
1996年 | 12篇 |
1995年 | 9篇 |
1993年 | 12篇 |
1992年 | 11篇 |
1991年 | 12篇 |
1990年 | 17篇 |
1989年 | 24篇 |
1988年 | 9篇 |
1987年 | 13篇 |
1986年 | 13篇 |
1985年 | 7篇 |
1984年 | 14篇 |
1983年 | 10篇 |
1982年 | 10篇 |
1981年 | 14篇 |
1980年 | 11篇 |
1979年 | 12篇 |
1978年 | 16篇 |
1977年 | 10篇 |
1976年 | 10篇 |
1975年 | 12篇 |
1974年 | 6篇 |
1973年 | 7篇 |
1972年 | 8篇 |
1970年 | 6篇 |
排序方式: 共有954条查询结果,搜索用时 15 毫秒
91.
V. Torres-Zúñiga O. G. Morales-Saavedra E. Rivera R. Castañeda-Guzmán J. G. Bañuelos R. Ortega-Martínez 《Journal of Sol-Gel Science and Technology》2010,56(1):7-18
SiO2-based bulk and film sol–gel hybrid materials were prepared with a family of novel liquid crystalline (LC) amphiphilic azo-dyes
bearing oligo(ethylene glycol) spacers (named here RED-PEG-n, n = 2, 3, 4, 6). The catalyst-free-sonogel route was implemented to produce optically active hybrid monoliths and spin-coated
films with these materials. Comprehensive morphological, thermal, photo-acoustic and spectroscopic sample characterizations
were performed in order to elucidate the physical properties of these novel compounds within the sonogel environment. Film
samples were also studied via the nonlinear optical (NLO) second harmonic generation (SHG)-Maker fringes technique. Results
show that the chromophores were homogeneously embedded within the highly pure SiO2-sonogel network, showing a clear thermotropic mesogenic behavior. The push–pull structure of the implemented azo-dyes allowed
effective electrically-induced monomeric alignment within the sonogel confinement; thus, stable quadratic NLO-SHG-activity
in the organic–inorganic film samples was achieved despite the lack of glass transition temperature (T
g
) of the guest LC-compounds. 相似文献
92.
Genovaitė Valiulienė Albina Žielienė Birutė Šimkūnaitė Leonas Naruškevičius Loreta Tamašauskaitė Tamašiūnaitė Vidas Pakštas Algis Selskis 《Journal of Solid State Electrochemistry》2010,14(2):203-212
The electrochemical behavior of Bi2S3 coatings in Watts nickel plating electrolyte was investigated using the cyclic voltammetry, electrochemical quartz crystal
microbalance, X-ray diffraction, and energy dispersive X-ray analysis methods. During the bismuth sulfide coating reduction
in Watts background electrolyte in the potential region from −0.4 to −0.6 V, the Bi2S3 and Bi(III) oxygen compounds are reduced to metallic Bi, and the decrease in coating mass is related to the transfer of S2− ions from the electrode surface. When the bismuth sulfide coating is reduced in Watts nickel plating electrolyte, the observed
increase in coating mass in the potential region −0.1 to −0.4 V is conditioned by Ni2+ ions reduction before the bulk deposition of Ni, initiated by Bi2S3. In this potential region, the reduction of Bi(III) oxygen compounds can occur. After the treatment of as-deposited bismuth
sulfide coating in nickel plating electrolyte at E = −0.3 V, the sheet resistance of the layer decreases from 1013 to 500–700 Ω cm. A metal-rich mixed sulfide Ni3Bi2S2–parkerite is obtained when as-deposited bismuth sulfide coating is treated in Watts nickel plating electrolyte at a potential
close to the equilibrium potential of the Ni/Ni2+ system and then annealed at temperatures higher than 120 °C. 相似文献
93.
This paper extends the works of Kang and Ramanan (2010) and Kaspi and Ramanan (2011), removing the hypothesis of absolute continuity of the service requirement and patience time distributions. We consider a many-server queueing system in which customers enter service in the order of arrival in a non-idling manner and where reneging is considerate. Similarly to Kang and Ramanan (2010), the dynamics of the system are represented in terms of a process that describes the total number of customers in the system as well as two measure-valued processes that record the age in service of each of the customers being served and the “potential” waiting times. When the number of servers goes to infinity, fluid limit is established for this triple of processes. The convergence is in the sense of probability and the limit is characterized by an integral equation. 相似文献
94.
Dušan Repovš Witold Rosicki Žiga Virk Andreas Zastrow 《Topology and its Applications》2012,159(10-11):2609-2620
This paper shows that a construction, which was introduced by Piotr Minc in connection with a problem that came from Helly type theorems and that allows to replace three PL-arcs with a “sheltered middle path”, can in the case of general (non-PL) paths result in the topologist?s sine curve. 相似文献
95.
Simon Štampar Saša Sokolič Gorazd Karer Alenka Žnidaršič Igor Škrjanc 《Mathematical and Computer Modelling》2011,53(5-6):637-645
This paper deals with the development of a batch-reactor model with a theoretical and a locally affine fuzzy model. The batch reactor is used in the pharmaceutical industry for the production of drugs, where a rapid and precise temperature control is necessary. The model has to be built to include all the main features necessary for the purposes of modelling. The development of the model for the reactor is designed for further control development and simulation purposes, without doing any further experiments on the real process. In our case we use the model for simulating the reactor’s jacket temperature and the reactor’s core temperature. The theoretical model describes all the nonlinearities of the process of heating and cooling the content of the batch reactor. The main contribution of the theoretical model is in the modelling of the heat transfer between the reactor’s jacket and the reactor’s core, mainly caused by the change in the overall heat transfer, which also covers the main nonlinearity. Because of the complexity of the theoretical model a locally affine fuzzy model is also developed. 相似文献
96.
Katsuhiro Inomata Yoichi Sasaki Takuhei Nose 《Journal of Polymer Science.Polymer Physics》2002,40(17):1904-1912
We have investigated the morphology and packing manner of graft copolymers consisting of rigid‐rod‐like poly(γ‐benzyl L ‐glutamate) (PBLG) main chains and grafted diblock copolymers of amorphous poly(propylene glycol) (PPG) and crystalline poly(ethylene glycol) (PEG). The results of differential scanning calorimetry and wide‐angle X‐ray scattering measurements for graft copolymers with higher side‐chain volume fractions suggest that the rodlike main chains and crystallized PEG chains exist in segregated domains. Small‐angle X‐ray scattering profiles for these samples show diffraction intensity maxima accompanied by higher order peaks, the positions of which suggest the formation of an ordered layered structure. From these observations, the graft copolymers are estimated to form repeated layered structure consisting of segregated PBLG, PPG, and PEG layers. A proposed model for molecular packing of the graft copolymers is consistent with the experimental observation that the repeating distance for the layered structure decreases with an increase in the volume fraction of side chains. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1904–1912, 2002 相似文献
97.
V. J. Žigman 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1992,22(3):611-618
The results of viscosity cross sections evaluations for elastic electron-atom scattering from rare gases krypton and xenon, carried out in the energy interval from 0.1 to 54.4 eV are presented and discussed. The evaluations are based on four independent sets of partialwave phaseshifts, one theoretical and three experimental, taken from literature. An analytical estimate for the contribution of all the terms not included in the summation, for truncation at any chosen value of the electron angular momentum, is derived. The validity of assumption of isotropic angular scattering is investigated in the energy range considered. The present results invariably show significant deviations from the values calculated with this assumption. 相似文献
98.
99.
100.