全文获取类型
收费全文 | 229篇 |
免费 | 7篇 |
国内免费 | 1篇 |
专业分类
化学 | 183篇 |
晶体学 | 3篇 |
数学 | 15篇 |
物理学 | 36篇 |
出版年
2024年 | 2篇 |
2023年 | 4篇 |
2022年 | 8篇 |
2021年 | 4篇 |
2020年 | 6篇 |
2019年 | 6篇 |
2018年 | 5篇 |
2017年 | 5篇 |
2016年 | 12篇 |
2015年 | 4篇 |
2014年 | 8篇 |
2013年 | 14篇 |
2012年 | 16篇 |
2011年 | 15篇 |
2010年 | 15篇 |
2009年 | 12篇 |
2008年 | 11篇 |
2007年 | 11篇 |
2006年 | 12篇 |
2005年 | 10篇 |
2004年 | 8篇 |
2003年 | 3篇 |
2002年 | 6篇 |
2001年 | 6篇 |
2000年 | 8篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1993年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有237条查询结果,搜索用时 15 毫秒
21.
Věra JandováZdeněk Bastl Jan ŠubrtJosef Pola 《Journal of Analytical and Applied Pyrolysis》2011,92(2):287-291
Pulsed infrared laser-irradiation of titanium monoxide leads to ablation and when carried out in gaseous benzene (1-5 Torr) to simultaneous dielectric breakdown of benzene into low molecular carbonaceous species which allow carbothermal reduction of ablated TiOx particles and their protection by carbonaceous shell. The deposited particles are characterized by Fourier transform infrared Raman and X-ray photoelectron spectroscopy and by electron microscopy and shown to be stable towards oxidation in air. The reported process can find use in protection of gas-phase produced reactive nanoparticles by carbon phase. 相似文献
22.
B. Machura A. ?witlicka D. Tabak J. Polański 《Journal of organometallic chemistry》2011,696(3):731-738
The molecular structure of 7-acetamido-2-methyl-quinoline-5,8-dione has been determined and the reactivity of 7-acetamido-2-methyl-quinoline-5,8-dione (1) and 6-acetamido-2-methyl-quinoline-5,8-dione (2) towards Re(CO)5Cl has been examined. Two novel tricarbonyl rhenium complexes, fac-[Re(CO)3(7-acetamido-2-methyl-quinoline-5,8-dione)Cl]·CHCl3 (3·CHCl3) and fac-[Re(CO)3(6-acetamido-2-methyl-quinoline-5,8-dione)Cl]2·CHCl3 (4·CHCl3), have been synthesized and characterized spectroscopically and structurally. The electronic spectrum of 3 was investigated at the TDDFT level employing B3LYP functional in combination with LANL2DZ. 相似文献
23.
Janz JM Ren Y Looby R Kazmi MA Sachdev P Grunbeck A Haggis L Chinnapen D Lin AY Seibert C McMurry T Carlson KE Muir TW Hunt S Sakmar TP 《Journal of the American Chemical Society》2011,133(40):15878-15881
Cell surface heptahelical G protein-coupled receptors (GPCRs) mediate critical cellular signaling pathways and are important pharmaceutical drug targets. (1) In addition to traditional small-molecule approaches, lipopeptide-based GPCR-derived pepducins have emerged as a new class of pharmaceutical agents. (2, 3) To better understand how pepducins interact with targeted receptors, we developed a cell-based photo-cross-linking approach to study the interaction between the pepducin agonist ATI-2341 and its target receptor, chemokine C-X-C-type receptor 4 (CXCR4). A pepducin analogue, ATI-2766, formed a specific UV-light-dependent cross-link to CXCR4 and to mutants with truncations of the N-terminus, the known chemokine docking site. These results demonstrate that CXCR4 is the direct binding target of ATI-2341 and suggest a new mechanism for allosteric modulation of GPCR activity. Adaptation and application of our findings should prove useful in further understanding pepducin modulation of GPCRs as well as enable new experimental approaches to better understand GPCR signal transduction. 相似文献
24.
Sharma P Ritson DJ Burnley J Moses JE 《Chemical communications (Cambridge, England)》2011,47(38):10605-10607
A synthetic approach towards the structurally complex dimer, kingianin A is reported. The strategy involved a cascade of complexity generating reactions, inspired through biosynthetic speculation. A concise protecting group free synthesis of the proposed monomeric precursor pre-kingianin A has been achieved using a tandem Stille cross-coupling reaction and electrocyclisation process. However, preliminary studies of the key dimerisation reaction have been conducted, which indicate that the process is not spontaneous, raising questions as to the origin of this complex natural product. 相似文献
25.
Heteroaromatic oligomer 5,7,12,14-tetrachloro-6,13-diazapentacene (TCDAP) was characterized and assessed as n-channel material in field-effect transistor applications. A single-crystal transistor based on TCDAP as the channel material exhibits a very high electron mobility of 3.39 cm(2) V(-1) s(-1) and an on/off ratio of ~1.08 × 10(4) respectively. 相似文献
26.
27.
R. Alexandrescu J. Morjan C. Grigoriu I. N. Mihailescu Z. Bastl J. Tlaskal R. Mayer J. Pola 《Applied Physics A: Materials Science & Processing》1988,46(4):275-279
Infrared multiphoton decomposition of monosilane in the presence of methyl methacrylate results in the formation of gaseous methane, acetylene, butenes and carbon monoxide along with a solid polymer whose chemical mechanism of formation is discussed in line of the poly(dimethylsiloxane) structure inferred from ESCA and IR spectral analysis. 相似文献
28.
Madhusudanan KP Kumar B Tiwari P Madhusudan SK Misra AK 《Journal of mass spectrometry : JMS》2005,40(1):25-35
The effect of metal cationization on the tandem mass spectra of glycosyl dithioacetals of glucose, mannose, galactose, rhamnose, arabinose and xylose was studied by electrospray ionization mass spectrometry under ammonium and metal (Li, Na, Ag and Cu) ion cationization conditions. The ammonium-cationized glycosyl dithioacetals fragment by loss of ammonia followed by either two molecules of EtSH or one molecule of EtSH and one molecule of H2O. Lithium cationization leads to additional eliminations such as EtSEt and EtSSEt and C-C cleavages. Elimination of EtSH is not observed under sodium cationization. Silver cationization, on the other hand, leads to additional fragmentations involving the elimination of silver as AgOH and AgSEt. Copper cationization results in adducts where copper has undergone a change of oxidation state from II to I. Li+, Ag+ and Cu+ cationization seem to favour cyclization resulting in elimination of EtSH. However, the mechanisms seem to be differently affected by different metal ions. Li+ and Ag+ cationization appear to be non-specific and favour cyclization involving C2-, C4- and C5-hydroxyl hydrogens, whereas Cu+ cationization seems to favour cyclization involving C4-hydroxyl hydrogen. 相似文献
29.
A total synthesis of the structure corresponding to the novel tricyclic diterpene guanacastepene C has been realized in which a Knoevenagel cyclization serves as a key step to annulate the six-membered C-ring on a stereochemically secured bicyclic hydroazulene precursor. 相似文献
30.
S. Agosteo G.A.P. Cirrone P. Colautti G. Cuttone G. D’Angelo A. Fazzi M.V. Introini D. Moro A. Pola V. Varoli 《Radiation measurements》2010,45(10):1284-1289
A monolithic silicon device consisting of a matrix of micrometric cylindrical diodes (about 2 μm in thickness and 9 μm in diameter) coupled to a residual energy measurement stage E (about 500 μm in thickness) was proposed and studied for assessing the quality of a therapeutic proton beam. The device was placed at different depths inside a polymethyl-methacrylate phantom and irradiated with a modulated 62 MeV proton beam at the Centro di AdroTerapia e Applicazioni Nucleari Avanzate (CATANA) of the Laboratori Nazionali del Sud (LNS, Catania, Italy) of the Istituto Nazionale di Fisica Nucleare (INFN).At each phantom depth, the energy imparted in the two detector stages was measured event-by-event in coincidence mode. The distributions of the energy imparted to the cylindrical diodes were corrected for tissue-equivalence by applying an optimized procedure. In order to perform a comparison with literature data measured with a cylindrical TEPC, the distributions derived with the silicon detector were corrected for shape-equivalence. The agreement with the microdosimetric spectra measured with the TEPC was satisfactory above the detection limit imposed by the electronic noise of the silicon-based system. 相似文献