全文获取类型
收费全文 | 1951篇 |
免费 | 25篇 |
国内免费 | 1篇 |
专业分类
化学 | 1635篇 |
晶体学 | 6篇 |
力学 | 9篇 |
数学 | 47篇 |
物理学 | 280篇 |
出版年
2021年 | 12篇 |
2020年 | 10篇 |
2019年 | 17篇 |
2016年 | 15篇 |
2015年 | 9篇 |
2014年 | 24篇 |
2013年 | 21篇 |
2012年 | 28篇 |
2011年 | 37篇 |
2010年 | 21篇 |
2009年 | 13篇 |
2008年 | 33篇 |
2007年 | 27篇 |
2006年 | 14篇 |
2005年 | 19篇 |
2004年 | 19篇 |
2003年 | 16篇 |
2002年 | 16篇 |
2001年 | 16篇 |
2000年 | 24篇 |
1999年 | 18篇 |
1998年 | 17篇 |
1997年 | 17篇 |
1996年 | 38篇 |
1995年 | 42篇 |
1994年 | 28篇 |
1993年 | 39篇 |
1992年 | 30篇 |
1991年 | 9篇 |
1990年 | 8篇 |
1988年 | 13篇 |
1987年 | 15篇 |
1986年 | 7篇 |
1985年 | 9篇 |
1984年 | 10篇 |
1982年 | 8篇 |
1980年 | 7篇 |
1977年 | 6篇 |
1976年 | 9篇 |
1974年 | 12篇 |
1973年 | 6篇 |
1967年 | 77篇 |
1966年 | 166篇 |
1965年 | 130篇 |
1964年 | 148篇 |
1963年 | 122篇 |
1962年 | 122篇 |
1961年 | 146篇 |
1960年 | 127篇 |
1959年 | 61篇 |
排序方式: 共有1977条查询结果,搜索用时 15 毫秒
121.
Härdle H. Weiss G. Hunklinger S. Baumann F. 《Zeitschrift für Physik B Condensed Matter》1987,65(3):291-297
We have studied the elastic properties of thin films of amorphous water (a-H2O), prepared at 4.4 K by quench condensation. At low temperatures acoustic anomalies are observed, which are characteristic for amorphous solids. Annealing, even at moderate temperatures, reduces the number of tunneling states. A strong increase of the acoustic absorption is observed in the vicinity of the annealing temperatures. This indicates that structural rearrangements are possible in quenched condensed films at temperatures well below the glass transition. 相似文献
122.
123.
Markus Bacher Karl Baumann Hermann Knapp Andrea Steck Sigrid Teibl 《Magnetic resonance in chemistry : MRC》2009,47(1):71-83
The complete 1H and 13C NMR data of 27 pravastatin derivatives are presented. Assignment was achieved by use of 1D and 2D NMR experiments (selective 1D NOE, COSY, NOESY, HSQC, HMBC). Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
124.
Theodore F. Baumann Ticora V. Jones Thomas Wilson Andrew P. Saab Robert S. Maxwell 《Journal of polymer science. Part A, Polymer chemistry》2009,47(10):2589-2596
We report the synthesis and characterization of novel elastomeric nanocomposites containing polyhedral oligomeric silsesquioxanes (POSS) as both the cross‐linker and filler within a polydimethylsiloxane (PDMS) polymer matrix. These polymer composites were prepared through the reaction of octasilane‐POSS (OS‐POSS) with vinyl‐terminated PDMS chains using hydrosilylation chemistry. In addition, larger super‐POSS cross‐linkers, consisting of two pendant hepta(isobutyl)POSS molecules attached to a central octasilane‐POSS core, were also used in the fabrication of the PDMS composites. The chemical incorporation of these POSS cross‐linkers into the PDMS network was verified by solid‐state 1H magic angle spinning NMR. Based on dynamic mechanical analysis, the PDMS nanocomposites prepared with the octafunctional OS‐POSS cross‐linker exhibited enhanced mechanical properties relative to polymer systems prepared with the tetrafunctional TDSS cross‐linker at equivalent loading levels. The observed improvements in mechanical properties can be attributed to the increased dimensionality of the POSS cross‐linker. The PDMS elastomers synthesized from the larger super‐POSS molecule showed improved mechanical properties relative to both the TDSS and OS‐POSS composites due to the increased volume‐fraction of POSS filler in the polymer matrix. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2589–2596, 2009 相似文献
125.
Thuro Arnold Kay Großmann Nils Baumann 《Analytical and bioanalytical chemistry》2010,396(5):1641-1653
Biofilms may immobilize toxic heavy metals in the environment and thereby influence their migration behaviour. The mechanisms
of these processes are currently not understood, because the complexity of such biofilms creates many discrete geochemical
microenvironments which may differ from the surrounding bulk solution in their bacterial diversity, their prevailing geochemical
properties, e.g. pH and dissolved oxygen concentration, the presence of organic molecules, e.g. metabolites, and many more,
all of which may affect metal speciation. To obtain such information, which is necessary for performance assessment studies
or the development of new cost-effective strategies for cleaning waste waters, it is very important to develop new non-invasive
methods applicable to study the interactions of metals within biofilm systems. Laser fluorescence techniques have some superior
features, above all very high sensitivity for fluorescent heavy metals. An approach combining confocal laser scanning microscopy
and laser-induced fluorescence spectroscopy for study of the interactions of biofilms with uranium is presented. It was found
that coupling these techniques furnishes a promising tool for in-situ non-invasive study of fluorescent heavy metals within
biofilm systems. Information on uranium speciation and uranium redox states can be obtained. 相似文献
126.
Adare A Afanasiev S Aidala C Ajitanand NN Akiba Y Al-Bataineh H Alexander J Angerami A Aoki K Apadula N Aphecetche L Aramaki Y Asai J Atomssa ET Averbeck R Awes TC Azmoun B Babintsev V Bai M Baksay G Baksay L Baldisseri A Barish KN Barnes PD Bassalleck B Basye AT Bathe S Batsouli S Baublis V Baumann C Bazilevsky A Belikov S Belmont R Bennett R Berdnikov A Berdnikov Y Bhom JH Bickley AA Blau DS Boissevain JG Bok JS Borel H Boyle K Brooks ML Buesching H Bumazhnov V Bunce G Butsyk S Camacho CM 《Physical review letters》2011,107(14):142301
We present measurements of J/ψ yields in d+Au collisions at sqrt[s(NN)]=200 GeV recorded by the PHENIX experiment and compare them with yields in p+p collisions at the same energy per nucleon-nucleon collision. The measurements cover a large kinematic range in J/ψ rapidity (-2.2相似文献
127.
Christian Niedrig Simon TaufallMónica Burriel Wolfgang MenesklouStefan F. Wagner Stefan Baumann 《Solid State Ionics》2011,197(1):25-31
Ba0.5Sr0.5Co0.8Fe0.2O3 - δ (BSCF) is a material with excellent oxygen ionic and electronic transport properties reported by many research groups. In its cubic phase, this mixed ionic-electronic conducting (MIEC) perovskite is a promising candidate for oxygen permeation membranes. For this application, its long-term stability under operating conditions (especially temperature and oxygen partial pressure) is of crucial importance.The present work is focused on the thermal stability of the BSCF cubic phase in the targeted temperature range for applications (700…900 °C) in light of previous studies in literature reporting a reversible transition to a hexagonal phase somewhere below 900 °C.To this end, single phase cubic BSCF powders were annealed at different temperatures over varying periods of time. Phase composition was subsequently analysed by X-ray diffractometry (XRD) in order to determine both the temperature limit and the time-scale for the formation of the hexagonal phase. Additionally, the long-term behaviour of the electrical conductivity was examined on bulk samples at 700 °C, 800 °C and 900 °C over several hundreds of hours, showing a prolonged decrease at 800 °C. The decrease in electrical conductivity at this temperature was also examined on bulk samples with different grain sizes, showing a more pronounced decrease the smaller the average grain size.Coexistence of both phases (cubic and hexagonal) could also be shown for 700 °C, however with a different phase equilibrium than at 800 °C. 相似文献
128.
P. Parrilla P. Kaim E. A. Hogendoorn R. A. Baumann 《Analytical and bioanalytical chemistry》1999,363(1):77-82
In the development of a screening method for the determination of residues of mecoprop in soils involving coupled-column RPLC-UV (228 nm) the cleanup performance of a 5 μm GFF-II internal surface reversed phase (ISRP, Pinkerton) analytical column (50 × 4.6 mm I.D.) as a first column was investigated. In comparison to an analytical C18 column the ISRP column substantially improved the separation between acidic analyte and co-extracted humic substances. Under the selected coupled-column conditions soil extracts obtained after hydrolysis with an aqueous alkaline solution, acidifying and centrifugation could be analyzed directly allowing the determination of mecoprop in soils to a level of about 0.02 mg/kg. A rapid concentration step on a 100 mg C18 solid phase extraction (SPE) cartridge was adopted into the procedure providing a limit of detection (S/N = 3) of 0.01 mg/kg of mecoprop in soil. The method was validated by analyzing freshly spiked soil samples and samples with aged residues. In case of freshly spiked samples the overall recovery was 87% (n = 18, spiked level 0.02–8.0 mg/kg) with a repeatability of 6.8% and a reproducibility of 8.3%. No significant decrease of the recovery was observed for samples with aged residues (n = 15, spiked level 0.1 and 8.0 mg/kg) during a storage of 29 days in the refrigerator at about 4?°C; a storage of 67 days provided a mean recovery of 76% (n = 14, spiked level 8.0 mg/kg). 相似文献
129.
L. v. Udránszky und E. Baumann 《Fresenius' Journal of Analytical Chemistry》1890,29(1):238-239
Ohne Zusammenfassung 相似文献
130.