全文获取类型
收费全文 | 890篇 |
免费 | 18篇 |
国内免费 | 11篇 |
专业分类
化学 | 582篇 |
晶体学 | 3篇 |
力学 | 36篇 |
数学 | 105篇 |
物理学 | 193篇 |
出版年
2023年 | 8篇 |
2022年 | 14篇 |
2021年 | 12篇 |
2020年 | 14篇 |
2019年 | 11篇 |
2018年 | 10篇 |
2017年 | 7篇 |
2016年 | 18篇 |
2015年 | 19篇 |
2014年 | 26篇 |
2013年 | 37篇 |
2012年 | 62篇 |
2011年 | 93篇 |
2010年 | 39篇 |
2009年 | 40篇 |
2008年 | 55篇 |
2007年 | 40篇 |
2006年 | 49篇 |
2005年 | 47篇 |
2004年 | 43篇 |
2003年 | 31篇 |
2002年 | 26篇 |
2001年 | 21篇 |
2000年 | 34篇 |
1999年 | 19篇 |
1998年 | 8篇 |
1997年 | 6篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 4篇 |
1993年 | 12篇 |
1992年 | 9篇 |
1991年 | 8篇 |
1990年 | 7篇 |
1989年 | 3篇 |
1988年 | 7篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1976年 | 2篇 |
1974年 | 2篇 |
1935年 | 4篇 |
排序方式: 共有919条查询结果,搜索用时 15 毫秒
71.
Tkaczyk S Tollefson K Tollestrup A Toyoda H Trischuk W de Troconiz JF Tseng J Turini N Ukegawa F Valls J Vejcik S Velev G Vidal R Vilar R Vologouev I Vucinic D Wagner RG Wagner RL Wahl J Wallace NB Walsh AM Wang C Wang CH Wang MJ Watanabe T Waters D 《Physical review letters》2000,84(6):1110-1115
We search for color singlet technirho and technipion production in p&pmacr; collisions at sqrt[s] = 1.8 TeV recorded with the Collider Detector at Fermilab. These exotic technimesons are present in a model of walking technicolor. The signatures studied are lepton plus two jets plus E(T) and multijet final states. No excess of events is seen in either final state. We set an upper limit on the technirho production cross section and exclude a region in the technipion mass versus technirho mass plane. 相似文献
72.
Toyoda H Trischuk W de Troconiz JF Tseng J Turini N Ukegawa F Vaiciulis T Valls J Vejcik S Velev G Vidal R Vilar R Volobouev I Vucinic D Wagner RG Wagner RL Wahl J Wallace NB Walsh AM Wang C Wang CH Wang MJ Watanabe T Waters D Watts T Webb R 《Physical review letters》2000,84(22):5043-5048
We report results from a study of events with a leading antiproton of beam momentum fraction 0.9057 GeV. Using the dijet events, we evaluate the diffractive structure function of the antiproton and compare it with expectations based on results obtained in diffractive deep inelastic scattering experiments at the DESY ep collider HERA. 相似文献
73.
74.
75.
Ing Youn Chen Chih-Yung Tseng Yur-Tsai Lin Chi-Chuan Wang 《International Journal of Multiphase Flow》2009
This study investigates the pressure change and flow pattern subject to the influence of sudden contractions. The air and water mixture flows from small rectangular channels (2 × 4, 2 × 6, 4 × 4 and 4 × 6 mm, respectively) into a 2 mm diameter tube. The total mass flux (G) ranges from 100 to 700 kg/m2 s with gas quality (x) being varied from 0.001 to 0.8. In general the contraction pressure change increases with the rise of mass flux, and gas quality but an unique deflection of contraction pressure change pertaining to liquid vena contracta at a very low gas quality is encountered at a very low gas quality in the 4 ± 6 mm test section. For a low gas quality, elongated bubble prevails after the contraction, yet the size of elongated bubbles is reduced when the aspect ratio is increased. Comparisons amid the pressure change data of this study and available literature data with the predictions of existing model/correlations indicate that none of them can accurately predict the data. It is found that the influence of surface tension and outlet tube size, or equivalently the Bond number plays a major role for the departure of various models/correlations. Among the models/correlations being examined, the homogeneous model shows a little better than the others. Hence by taking account the influences of gas quality, Bond number, Weber number and area contraction ratio into the homogeneous model, a modified homogeneous correlation is proposed that considerably improves the predictive ability over existing correlations with a mean deviation of 30% to all the data. 相似文献
76.
Y. C. Chu J. R. Chen J. M. Tseng L. C. Tsai C. M. Shu 《Journal of Thermal Analysis and Calorimetry》2011,106(1):227-234
Di-tert-butyl peroxide (DTBP) is an organic peroxide (OP) which has widespread use in the various chemical industries. In the past,
thermal runaway reactions of OPs have been caused by their general thermal instability or by reactive incompatibility in storage
or operation, which can create potential for thermal decomposition reaction. In this study, differential scanning calorimetry
was applied to measure the heat of decomposition reactions, which can contribute to understand the reaction characteristics
of DTBP. Vent sizing package 2 was also employed to evaluate rates of increase for temperature and pressure in decomposition
reactions, and then the thermokinetic parameters of DTBP were estimated. Finally, hazard characteristics of the gassy system
containing DTBP, specifically with respect to thermal criticality, were clearly identified. 相似文献
77.
Chen‐Rui Tseng Hsin‐Yi Lee Feng‐Chih Chang 《Journal of Polymer Science.Polymer Physics》2001,39(17):2097-2107
We investigated the effects of montmorillonite (clay) on the crystallization kinetics of syndiotactic polystyrene (sPS) with isothermal differential scanning calorimetry analyses. The clay was dispersed into the sPS matrix via melt blending on a scale of 1–2 nm or up to about 100 nm, depending on the surfactant treatment. For a crystallization temperature of 240 °C, the isothermal crystallization data were fitted well with the Avrami crystallization equation. Crystallization data on the kinetic parameters (i.e., the crystallization rate constant, Avrami exponent, clay content, and clay/surfactant cation‐exchange ratio) were also investigated. Experimental results indicated that the crystallization rate constant of the sPS nanocomposite increased with increasing clay content. The clay played a vital role in facilitating the formation on the thermodynamically more favorable all‐β‐form crystal when the sPS was melt‐crystallized. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2097–2107, 2001 相似文献
78.
Ying‐Ling Liu Min‐Chi Tseng Meng‐Han Fangchiang 《Journal of polymer science. Part A, Polymer chemistry》2008,46(15):5157-5166
Thermally induced polymerization of multifunctional methylmethacrylate POSS (MMA‐POSS) was studied in this work for preparation of polymer/POSS nanocomposites. The polymerization of MMA‐POSS could be promoted with benzoyl peroxide (BPO). Self‐assembly of POSS into a layer‐by‐layer structure in the MMA‐POSS polymer (TP‐MMA‐POSS) is observed with a transmission electron microscopy. An ultra‐low‐k value of about 1.85 is measured with TP‐MMA‐POSS. In addition, polyimide‐POSS nanocomposites are also prepared. These nanocomposites demonstrate good homogeneity and enhanced mechanical properties. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5157–5166, 2008 相似文献
79.
The feasibility of using spirulina as adsorbent for the treatment of low-level liquid radwaste is studied. The experimental results indicate that the sorption capacity of spirulina is good for the di- and trivalent metallic ions at pH 3-7, but rather poor for the mono-valent metallic ions and non-metallic ions. Some factors affecting metal ion uptake by spirulina such as the content of detergent, sodium ion in liquid radwaste and the stability of spirulina under gamma irradiation were also investigated. 相似文献
80.
Octasubstituted phthalocyanines bearing bulky (cyclopentyl)methyl- and (cyclohexyl)methyl-substituents in non-peripheral positions are prepared and characterised. The synthesis of the precursor phthalonitriles is achieved through nickel-catalysed cross-coupling employing alkylzinc reagents. In the case of the (cyclopentyl)methyl derivative the formal precursor is 5-hexenyl bromide which yields the cyclised material exclusively on formation of the zinc reagent and subsequent cross-coupling. 相似文献