全文获取类型
收费全文 | 458篇 |
免费 | 4篇 |
国内免费 | 2篇 |
专业分类
化学 | 382篇 |
晶体学 | 3篇 |
力学 | 3篇 |
数学 | 23篇 |
物理学 | 53篇 |
出版年
2021年 | 3篇 |
2017年 | 3篇 |
2015年 | 2篇 |
2014年 | 6篇 |
2013年 | 18篇 |
2012年 | 12篇 |
2011年 | 21篇 |
2010年 | 12篇 |
2009年 | 13篇 |
2008年 | 17篇 |
2007年 | 23篇 |
2006年 | 25篇 |
2005年 | 21篇 |
2004年 | 15篇 |
2003年 | 18篇 |
2002年 | 20篇 |
2001年 | 5篇 |
2000年 | 9篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 14篇 |
1995年 | 8篇 |
1994年 | 3篇 |
1993年 | 8篇 |
1992年 | 6篇 |
1991年 | 7篇 |
1990年 | 10篇 |
1989年 | 10篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1985年 | 13篇 |
1984年 | 12篇 |
1983年 | 12篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1980年 | 13篇 |
1979年 | 11篇 |
1978年 | 7篇 |
1977年 | 9篇 |
1976年 | 5篇 |
1975年 | 8篇 |
1974年 | 8篇 |
1973年 | 1篇 |
1972年 | 4篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1968年 | 4篇 |
1967年 | 3篇 |
排序方式: 共有464条查询结果,搜索用时 78 毫秒
111.
Ilhyong Ryu Membo Ryang Ilsong Rhee Haruo Omura Shinji Murai Noboru Sonoda 《合成通讯》2013,43(12):1175-1179
An improved and convenient procedure for symmetrical aliphatic ketone synthesis is described, which employs the reaction of alkylmercuric bromides with nickel carbonyl in the presence of potassium iodide. 相似文献
112.
Toya H Okano K Takasu K Ihara M Takahashi A Tanaka H Tokuyama H 《Organic letters》2010,12(22):5196-5199
The enantioselective total synthesis of (-)- and (+)-petrosin is described. The union of two key segments was executed by Suzuki-Miyaura coupling. The quinolizidine rings were stereoselectively constructed via a diastereoselective Mannich reaction and an aza-Michael reaction. The 16-membered ring was constructed by ring-closing metathesis with the second-generation Grubbs catalyst. 相似文献
113.
Ikawa T Hoshino F Matsuyama T Takahashi H Watanabe O 《Langmuir : the ACS journal of surfaces and colloids》2006,22(6):2747-2753
We demonstrate a novel technique for molecular imprinting and immobilization on a surface of a polymer containing azo dyes (azopolymer). The azopolymer was found to be capable of immobilizing micrometer- and nanometer-scale macromolecules (e.g., lambda-DNA, immunoglobulin G (IgG), bacterial protease, and 1-mum polystyrene particles) through photoirradiation with blue-wavelength light. Fluorescence and atomic force microscopy studies revealed that the azopolymer surface deformed along with the shape of the macromolecules, holding them in place after photoirradiation. The desorption of the immobilized macromolecules from the azopolymer surface in an aqueous medium was observed to be very slow, on the time scale of 10 min to weeks, depending on the photoirradiation time. Immunological and enzymatic studies showed that IgG and bacterial protease immobilized on the azopolymer surface retained their original functionality. These results suggest that the azopolymer physically, not chemically, binds the macromolecules because of the increase in contact area between the macromolecules and the azopolymer surface after photoirradiation. 相似文献
114.
Fujita M Hattori W Sano T Baba M Someya H Miyazaki K Kamijo K Takahashi K Kawaura H 《Journal of chromatography. A》2006,1111(2):200-205
We have developed a high-throughput, two-dimensional-mapping (isoelectric point [pI], mass-to-charge ratio [m/z]) method by combining a capillary isoelectric focusing chip sealed with removable resin tape and a matrix-assisted laser desorption/ionization time-of-flight mass spectrometer. Sample proteins are separated in a meandering channel on the chip and immediately frozen. The tape is then removed and the proteins are freeze-dried. The freeze-drying maintains the separation state of the proteins and prevents movement of the sample solution, which can reduce pI resolution. A matrix solution is then applied and mass spectrometry is carried out by laser irradiation. The whole process takes less than 70 min, more than 10 times faster than with two-dimensional, polyacrylamide gel electrophoresis. 相似文献
115.
To build up finely designed patterns on solid surfaces, consecutive vapor-phase assisted surface photo-polymerization (VASP) of methyl methacrylate and styrene was carried out under UV-irradiation through a stripe-patterned photo-mask on Si-wafer and Au-plate surfaces, resulting in the reproduction of designed and multi-layered patterns made of block copolymer chains grafted from the surfaces. 相似文献
116.
The copper-catalyzed reaction between two different isocyanides produces the corresponding heteroaromatization products, imidazoles, in good yields. The reaction proceeds most probably through the activation of the sp3 C-H bond in the isocyanides by a copper catalyst, followed by a [3 + 2] cycloaddition between the cuprioisocyanide intermediates and arylisocyanides. 相似文献
117.
Yui T Kobayashi Y Yamada Y Tsuchino T Yano K Kajino T Fukushima Y Torimoto T Inoue H Takagi K 《Physical chemistry chemical physics : PCCP》2006,8(39):4585-4590
Photochemical Electron Transfer (ET) between an organic dye, the porphyrin derivative TMPyP, and an electron acceptor, methyl viologen MV2+, have been investigated at the interface of two different inorganic films, i.e., layered titania nano-sheets (TNS) and a monolayer film of spherical and mono-dispersed mesoporous silica (sMPS) particles (ca. 0.5 microm). TMPyP ions were intercalated within the sMPS nano-cavities to form (TMPyP-sMPS) while MV2+ ions were intercalated into the TNS interlayers to form (MV2+-TNS). The (TMPyP-sMPS) and (MV2+-TNS) films were then stacked on a silica substrate in this order to form a (MV2+-TNS)/(TMPyP-sMPS) film and, upon UV light irradiation, ET could be induced. However, when this film was stacked inversely, i.e., for the (TMPyP-sMPS)/(MV2+-TNS) films on a silica substrate, no photoinduced ET were observed. Interestingly, however, even for this photo-inactive inversely stacked film, ET could be generated by inserting a gold vapor-deposited layer between the (MV2+-TNS) and (TMPyP-sMPS) films. The conjugation conditions at the interface of the inversely stacked (TMPyP-sMPS)/(MV2+-TNS) hybrid film were, thus, confirmed to strongly affect the photoinduced electron transfers and their efficiencies. 相似文献
118.
Shin Kamijo 《Tetrahedron letters》2010,51(5):872-5931
A regio- and stereoselective acylation of saturated carbocycles has been achieved through two-step reactions involving the Norrish-Yang photocyclization of 1,2-diketones and subsequent ring opening of the α-hydroxy-cyclobutanones. The C-H activation of the carbocycle proceeds regioselectively at vicinal to the diketone moiety resulting in stereoselective formation of cis-fused bicycles. The following C-C cleavage affords vicinally cis-acylated carbocycles. Predictability, generality, and practicality of the present strategy have been demonstrated using variously modified saturated carbocycles. 相似文献
119.
A bimetallic catalyst and dual role catalyst: synthesis of N-(alkoxycarbonyl)indoles from 2-(alkynyl)phenylisocyanates 总被引:1,自引:0,他引:1
3-allyl-N-(alkoxycarbonyl)indoles are synthesized via the reaction of 2-(alkynyl)phenylisocyanates and allyl carbonates in the presence of Pd(PPh(3))(4) (1 mol %) and CuCl (4 mol %) bimetallic catalyst. It is most probable that Pd(0) acts as a catalyst for the formation of a pi-allylpalladium alkoxide intermediate and Cu(I) behaves as a Lewis acid to activate the isocyanate, and the cyclization step proceeds with a cooperative catalytic activity of Pd and Cu. On the other hand, N-(alkoxycarbonyl)indoles are produced via the reaction of 2-(alkynyl)phenylisocyanates and alcohols under a catalytic amount of Na(2)PdCl(4) (5 mol %) or PtCl(2) (5 mol %). Pd(II) or Pt(II) catalyst exhibits dual roles; it acts as a Lewis acid to accelerate the addition of alcohols to isocyanates and as a typical transition-metal catalyst to activate the alkyne for the subsequent cyclization. 相似文献
120.
Sven J. Cyvin Bjørg N. Cyvin Jon Brunvoll Haruo Hosoya Fuji Zhang Douglas J. Klein Rongsi Chen Oskar E. Polansky 《Monatshefte für Chemie / Chemical Monthly》1991,122(6-7):435-444
Summary The Kekulé structure counts (K) for primitive coronoids are treated. TheK formula which involves the trace of a matrix product is recalled and supplemented with new findings. In this way a kind of symmetry in the mathematical formulations is restored. Another general formulation for theK number is provided in terms of polynomials which, for a somewhat mysterious reason, are identified as the matching polynomials of cycles.
Zählung von Kekulé-Strukturen
Zusammenfassung Es werden Kekulé-Strukturzählungen (K) für einfache Coronoide behandelt. Die Formel fürK wird durch neugefundene Eigenschaften ergänzt. So wird eine Art von Symmetrie in den mathematischen Formulierungen erreicht. Eine andere generelle Formulierung derK-Zahlen wird in Form von Polynomen bereitgestellt, welche aus uneinsichtigen Gründen als die passenden Polynome von Cyclen identifiziert wurden.相似文献