全文获取类型
收费全文 | 1804篇 |
免费 | 34篇 |
国内免费 | 4篇 |
专业分类
化学 | 1174篇 |
晶体学 | 11篇 |
力学 | 27篇 |
数学 | 347篇 |
物理学 | 283篇 |
出版年
2022年 | 16篇 |
2021年 | 15篇 |
2020年 | 18篇 |
2019年 | 21篇 |
2018年 | 19篇 |
2017年 | 28篇 |
2016年 | 25篇 |
2015年 | 17篇 |
2014年 | 36篇 |
2013年 | 92篇 |
2012年 | 90篇 |
2011年 | 87篇 |
2010年 | 55篇 |
2009年 | 56篇 |
2008年 | 116篇 |
2007年 | 97篇 |
2006年 | 90篇 |
2005年 | 78篇 |
2004年 | 73篇 |
2003年 | 51篇 |
2002年 | 61篇 |
2001年 | 24篇 |
2000年 | 19篇 |
1999年 | 13篇 |
1997年 | 14篇 |
1996年 | 29篇 |
1995年 | 17篇 |
1994年 | 21篇 |
1993年 | 18篇 |
1992年 | 25篇 |
1991年 | 14篇 |
1990年 | 16篇 |
1989年 | 20篇 |
1988年 | 25篇 |
1987年 | 19篇 |
1986年 | 9篇 |
1985年 | 31篇 |
1984年 | 35篇 |
1983年 | 22篇 |
1982年 | 41篇 |
1981年 | 29篇 |
1980年 | 23篇 |
1979年 | 20篇 |
1978年 | 29篇 |
1977年 | 18篇 |
1976年 | 23篇 |
1974年 | 18篇 |
1973年 | 32篇 |
1972年 | 14篇 |
1971年 | 13篇 |
排序方式: 共有1842条查询结果,搜索用时 93 毫秒
941.
Abraham Berman 《Linear algebra and its applications》2006,419(1):1-7
The purpose of this note is to address the computational question of determining whether or not a square nonnegative matrix (over the reals) is completely positive and finding its CP-rank when it is. We show that these questions can be resolved by finite algorithms and we provide (non-polynomial) complexity bounds on the number of arithmetic/Boolean operations that these algorithms require. We state several open questions including the existence of polynomial algorithms to resolve the above problems and availability of algorithms for addressing complete positivity over the rationals and over {0, 1} matrices. 相似文献
942.
U. German A. Abraham M. Weinstein Z. B. Alfassi 《Journal of Radioanalytical and Nuclear Chemistry》2007,273(3):729-732
Second readouts of TLD 100 crystals exposed to radiation are used to reassess high doses. When the second readout is performed
by a regular readout cycle of 13.3 s, the accuracy of the estimations is too low to be practical for low doses in the 10–100
mSv range. A simple and efficient method was studied, which consists of expanding the heating time to 30 s. The efficiency
relative to a 13.3 readout time is about three timesbetter, and also the background is lower, thus the reassessment efficiency
is significantly improved. 相似文献
943.
H. Durchschlag C. Fochler K. Abraham B. Kulawik 《Radiation Physics and Chemistry》1999,55(5-6):691-697
The most important water-soluble components of the vertebrate eye (lens proteins, aqueous humor, vitreous, hyaluronic acid, ascorbic acid) have been investigated in aqueous solution, after preceding X- or UV-irradiation. Spectroscopic, chromatographic, electrophoretic, hydrodynamic and analytic techniques have been applied, to monitor several radiation damages such as destruction of aromatic and sulfur-containing amino acids, aggregation, crosslinking, dissociation, fragmentation, and partial unfolding. Various substances were found which were able to protect eye components effectively against radiation, some of them being also of medical relevance. 相似文献
944.
Abraham Chemtob Valrie Hroguez Yves Gnanou 《Journal of polymer science. Part A, Polymer chemistry》2004,42(5):1154-1163
Latex particles based on 1,4‐polybutadiene were synthesized via dispersion ring‐opening metathesis copolymerization of 1,5‐cyclooctadiene with a α‐norbornenyl poly(ethylene oxide) macromonomer. Stable but polydisperse colloidal dispersions in the 50 nm to 10 μm size range were obtained. In this work, particular attention was paid to the effects of the kinetics of copolymerization on the structure of the graft copolymers formed and on the onset of turbidity. Strategies to prepare monodisperse polybutadiene particles were also designed through the growth of a polybutadiene shell from a well‐defined polynorbornene seed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1154–1163, 2004 相似文献
945.
Abraham F. Jalbout Kostyantyn Y. Pichugin Ludwik Adamowicz 《Theoretical chemistry accounts》2004,111(2-6):358-362
A very diffuse, but spatially confined, electron trapped in a dipole–bound state of a polar molecule provides an excellent target for testing the interaction of a localized electron positioned outside the molecular frame of its host molecule with other atomic or molecular systems. In this work we use ab initio calculations to investigate systems where a dipole–bound electron attached to a uracil molecule is interacting with an N2 molecule and an Ar atom. Neither of the two systems forms a stable anion and in the aducts they form with the dipole–bound electron the electron becomes suspended between the uracil molecule and Ar or N2. Calculations are performed to determine the vertical electron detachment energies of these anions and to determine the molecular rearrangements occurring when the excess electron is removed from them.Contribution to the Jacopo Tomasi Honorary Issue 相似文献
946.
We introduce the lexicographic balanced optimization problem (LBaOP) and show that it can be solved efficiently if an associated lexicographic bottleneck problem can be solved efficiently. For special cases of cuts in a graph and base system of a matroid, improved algorithms are proposed. A generalization of LBaOP is also discussed. 相似文献
947.
S. Ezrahi Ido Nir Abraham Aserin Nick Kozlovich Yuri Feldman Nissim Garti 《Journal of Dispersion Science and Technology》2013,34(1-3):351-378
The hydration behavior of the system polyoxyethylene (10) oleylalcohol [C18:1 (EO)10 or Brij 97]/water/dodecane/butanol (model system B) was investigated along a dilution line for which the respective weight ratio of dodecane:butanol:Brij 97 is 3:3:4. Two experimental methods were applied: time domain dielectric spectroscopy (TDDS) and sub-zero temperature differential scanning calorimetry (SZT-DSC). Two types of bound water (with melting peaks at -25 and -11°C) were detected by SZT-DSC (using the endothermic mode), whereas TDDS revealed only one such type. Nevertheless, roughly the same total amount of bound water was estimated from these two techniques. The average number of bound water molecules per ethylene oxide (EO) group, NW/EO is 2.3 (TDDS data) or 2.5 (SZT-DSC data) in good agreement with the observation that 1–2 water layers are formed in the hydration of ethoxylated surfactants. We have also shown that butanol is involved in the formation of the bound water that melts at -25°C. We suggest that butanol molecules occupy binding sites within the second hydration shell, thereby reducing the expected total bound water content. 相似文献
948.
949.
Abraham Nudelman 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-3):51-94
Abstract The chemistry of optically active sulfur compounds has proven to be one of great interest and challenge as demonstrated by the prolific publications in this area. An ever larger number of different types of compounds with sulfur as center of chirality are being synthesized and it is expected that in future publications additional members of this group will be described. Thus far the following chiral sulfur compounds have been prepared: 相似文献
950.
Shady Farah Wahid Khan Ira Farber Dana Kesler‐Shvero Nurit Beyth Ervin I. Weiss Abraham J. Domb 《先进技术聚合物》2013,24(5):446-452
Quaternary ammonium polyethylenimine (QA‐PEI) nanoparticles were synthesized by PEI crosslinking and alkylation with octyliodide followed by quaternization by methyl iodide. The present study focuses on the reproducibility of particles formation with respect to particle size, positive charge, oxidative, thermal stability and antibacterial activity. The QA‐PEI‐based nanoparticles with particle size in the range of 160–190 nm were synthesized in high reproducibility and showed high chemical stability against environmental changes including exposure to different oxidizers and storage conditions. QA‐PEI nanoparticles incorporated in dental restorative resin composites at 2% w/w demonstrated strong antibacterial activity. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献