全文获取类型
收费全文 | 373篇 |
免费 | 6篇 |
国内免费 | 4篇 |
专业分类
化学 | 215篇 |
晶体学 | 5篇 |
力学 | 13篇 |
数学 | 61篇 |
物理学 | 89篇 |
出版年
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 8篇 |
2020年 | 7篇 |
2019年 | 3篇 |
2018年 | 6篇 |
2017年 | 6篇 |
2016年 | 12篇 |
2015年 | 4篇 |
2014年 | 17篇 |
2013年 | 19篇 |
2012年 | 14篇 |
2011年 | 33篇 |
2010年 | 17篇 |
2009年 | 18篇 |
2008年 | 25篇 |
2007年 | 23篇 |
2006年 | 19篇 |
2005年 | 30篇 |
2004年 | 24篇 |
2003年 | 16篇 |
2002年 | 14篇 |
2001年 | 4篇 |
2000年 | 9篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 8篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有383条查询结果,搜索用时 0 毫秒
61.
We reveal the non-metric geometry underlying ω→0 Brans–Dicke theory by unifying the metric and scalar field into a single geometric structure. Taking this structure seriously as the geometry to which matter universally couples, we show that the theory is fully consistent with solar system tests. This is in striking contrast with the standard metric coupling, which grossly violates post-Newtonian experimental constraints. 相似文献
62.
The interaction between cells and biomaterials has been mimicked using nylon microparticles as pseudo-cells and PLMA and PIBMA as biomaterial model acrylate polymers. The shift of fundamental resonance frequencies was negative for both polymers, indicating mass-coupling to the sensor surface. The shifts of the 3rd, 5th and 7th overtone frequencies were initially positive for both polymers, indicating a particle slip or wobbling on the surface. The QCM technique could discriminate between the two different polymers, showing increased interaction between microparticle and PLMA. The dissipation shift was positive for all overtones on both polymers, but again with faster and more prominent response for PLMA. 相似文献
63.
Bombelli C Bernardini C Elemento G Mancini G Sorrenti A Villani C 《Journal of the American Chemical Society》2008,130(9):2732-2733
Chiral recognition was observed in a biomembrane model. Micellar aggregates formed by enantiopure N-alkyl-N,N-dimethyl-N-(1-phenyl)ethylammonium bromide were in fact able to convert the racemic mixture of bilirubin-IXalpha into an enantiomerically enriched mixture. The stereochemical preference and the extent of enantiomeric enrichment depend on the length of the hydrophobic portion of the surfactant and on the concentration conditions, and changes in the stereochemical bias are reversible. 相似文献
64.
Butanol, a promising biofuel, can be produced by ABE (acetone, butanol and ethanol) fermentation using e.g. Clostridium acetobutylicum. However, the butanol concentration in the resulting broth is limited to only ca. 20 g/L due to the toxicity for the microorganisms. This low product concentration demands an efficient recovery process for successful commercialization of this process. In this study, a structured adsorbent in the form of steel monolith coated with a silicalite-1 film was prepared using the in situ growth method. The adsorbent was carefully characterized by SEM and XRD. The performance of the adsorbent was evaluated by performing breakthrough experiments at room temperature using model ABE fermentation broths and the performance was compared with that of traditional adsorbents in the form of beads. The structured silicalite-1 adsorbent showed less saturation loading time as compared to commercial binder free silicalite-1 beads, reflecting the different dimensions of the columns used, set by experimental constraints. Studies of the desorption process showed that by operating at appropriate conditions, butanol with high concentration i.e. up to 95.2 wt% for butanol–water model system and 88.5 wt% for ABE fermentation broth can be obtained using the structured silicalite-1 adsorbent. Commercial silicalite-1 beads also showed good selectivity but the concentration of butanol in the desorbed product was limited to 70 % for the butanol–water model system and 69 % for ABE fermentation broth, probably as a result of entrained liquid between the beads. 相似文献
65.
66.
Bitton R Berglin M Elwing H Colin C Delage L Potin P Bianco-Peled H 《Macromolecular bioscience》2007,7(12):1280-1289
Adhesive materials extracted from the brown algae Fucus Serratus were studied. These adhesives are composed of cross-linked alginate and polyphenols oxidized in the presence of KI or KBr. All formulations were capable of adhering to a variety of surfaces, however the adhesion properties were influenced by the halide used. SAXS and TEM experiments revealed that oxidized polyphenols self-assemble into chain-like objects, irrespective of the oxidation conditions. Yet, slight differences in the aggregate size were detected. QCM-D results showed that the kinetics of the oxidation was faster with iodide than with bromide. Moreover, oxidation with iodide generates stiffer networks, suggesting that the interaction between the alginate and the polyphenol could be the cause of the reduced adhesion. 相似文献
67.
Camille Descour Tibor Macko Dario Cavallo Matthew Parkinson Gerhard Hubner Anne Spoelstra Maurizio Villani Robbert Duchateau 《Journal of polymer science. Part A, Polymer chemistry》2014,52(10):1422-1434
Stereoblock polypropylenes comprising of iPP and sPP segments are synthesized by polymerization of the following binary system of metallocenes: the Cs‐symmetric [2,7‐t‐Bu2(Flu)2Ph2C(Cp)ZrCl2] and the C2‐symmetric rac‐Me2Si(2‐Me‐4‐Ph‐Ind)2ZrCl2. Blends of samples made either by each catalyst individually (solution blend) with materials obtained with the mixed catalyst system (reactor blend) are compared. The simultaneous presence of MAO and DEZ, enhancing fast and reversible transfer of the growing chains between the two active centers, leads to the formation of a stereoblock microstructure. In this case, low molecular weight polymers are obtained. The junction between the blocks is qualitatively observed in 13C NMR. When made in toluene, the stereoblock material consists of a majority of syndiotactic sequences, whereas the ratio is more equilibrated when the polymerization was conducted in the more polar chlorobenzene. This is confirmed by the results obtained with 13C NMR, CRYSTAF, HT HPLC, DSC, SSA, WAXD, and optical microscopy. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1422–1434 相似文献
68.
69.
70.
In this paper we will report the results obtained by femtosecond Pulsed Laser Deposition on vanadium carbide. These results, compared with those obtained for another group 5 carbide, tantalum carbide, evidence large analogies between the two systems. Optical emission spectroscopy shows in both cases the presence of particles in the secondary plume and in both cases the films are formed by nanoparticles and present a stoichiometry corresponding to the hemicarbide. 相似文献