全文获取类型
收费全文 | 967篇 |
免费 | 26篇 |
国内免费 | 2篇 |
专业分类
化学 | 684篇 |
晶体学 | 17篇 |
力学 | 9篇 |
数学 | 53篇 |
物理学 | 232篇 |
出版年
2021年 | 12篇 |
2020年 | 17篇 |
2019年 | 14篇 |
2018年 | 9篇 |
2017年 | 13篇 |
2016年 | 15篇 |
2015年 | 15篇 |
2014年 | 20篇 |
2013年 | 50篇 |
2012年 | 51篇 |
2011年 | 56篇 |
2010年 | 25篇 |
2009年 | 33篇 |
2008年 | 56篇 |
2007年 | 45篇 |
2006年 | 42篇 |
2005年 | 41篇 |
2004年 | 37篇 |
2003年 | 43篇 |
2002年 | 49篇 |
2001年 | 17篇 |
2000年 | 18篇 |
1999年 | 10篇 |
1998年 | 15篇 |
1997年 | 15篇 |
1996年 | 23篇 |
1995年 | 14篇 |
1994年 | 12篇 |
1993年 | 15篇 |
1992年 | 18篇 |
1991年 | 5篇 |
1990年 | 7篇 |
1989年 | 5篇 |
1988年 | 8篇 |
1987年 | 8篇 |
1986年 | 7篇 |
1985年 | 20篇 |
1984年 | 15篇 |
1982年 | 12篇 |
1981年 | 13篇 |
1980年 | 9篇 |
1979年 | 11篇 |
1978年 | 10篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1975年 | 5篇 |
1974年 | 6篇 |
1973年 | 9篇 |
1968年 | 5篇 |
1966年 | 4篇 |
排序方式: 共有995条查询结果,搜索用时 15 毫秒
61.
Sato S Komoto T Kanamaru Y Kawamoto N Okada T Kaiho T Mogi K Morimoto S Umehara N Koda T Miyashita A Sakamoto T Niino Y Oka T 《Chemical & pharmaceutical bulletin》2002,50(2):292-297
New muq-opioid receptor (MOR) agonists containing 4-hydroxypiperidine, piperidine and piperazine moieties were synthesized and evaluated to find a peripheral opioid analgesic. Among the synthesized compounds, 12-[1-[3-(N,N-dimethylcarbamoyl)-3,3-diphenylpropyl]-4-hydroxypiperidin-4-yl]phenoxy]acetic acid (8: SS620) having phenoxyacetic acid and 4-hydroxypiperidine moieties showed the highest agonist potency on the MOR in an isolated guinea-pig ileum preparation, and it also had selectivity to the human MOR expressed in Chinese hamster ovary (CHO)-K1 cells compared with the same types of delta- and kappa-opioid receptors (DOR and KOR). In addition, compound 8 showed a 10 times more potent MOR agonist activity than loperamide. Furthermore, compound 8 showed a peripheral analgesic activity in vivo screening on rat. 相似文献
62.
63.
In the presence of catalytic amounts of Cp*Ru(cod)Cl, unsymmetrical 1,6-diynes possessing a variety of functional groups reacted with electron-deficient tricarbonyl compounds at the ketone C=O double bonds to selectively afford dienones via electrocyclic ring opening of the expected alpha-pyrans. The intramolecular Michael addition of the cycloadducts having an acetyl and an alkylidenemalonate moiety gave bicyclo[3.3.0]octenone derivatives. 相似文献
64.
Kubo K Akemoto M Anderson S Aoki T Araki S Bane KL Blum P Corlett J Dobashi K Emma P Frisch J Fukuda M Guo Z Hasegawa K Hayano H Higo T Higurashi A Honda Y Iimura T Imai T Jobe K Kamada S Karataev P Kashiwagi S Kim E Kobuki T Kotseroglou T Kurihara Y Kuriki M Kuroda R Kuroda S Lee T Luo X McCormick DJ McKee B Mimashi T Minty M Muto T Naito T Naumenko G Nelson J Nguyen MN Oide K Okugi T Omori T Oshima T Pei G Potylitsyn A Qin Q Raubenheimer T Ross M Sakai H Sakai I Schmidt F Slaton T Smith H 《Physical review letters》2002,88(19):194801
Electron beams with the lowest, normalized transverse emittance recorded so far were produced and confirmed in single-bunch-mode operation of the Accelerator Test Facility at KEK. We established a tuning method of the damping ring which achieves a small vertical dispersion and small x-y orbit coupling. The vertical emittance was less than 1% of the horizontal emittance. At the zero-intensity limit, the vertical normalized emittance was less than 2.8 x 10(-8) rad m at beam energy 1.3 GeV. At high intensity, strong effects of intrabeam scattering were observed, which had been expected in view of the extremely high particle density due to the small transverse emittance. 相似文献
65.
Hisashi Shima Fumiyoshi Takano Hidenobu Muramatsu Masashi Yamazaki Hiroyuki Akinaga Akinori Kogure 《固体物理学:研究快报》2008,2(3):99-101
Kelvin probe force microscopy (KFM) and conductive atomic force microscopy (C‐AFM) together with micro X‐ray photoelectron spectroscopy (XPS) were performed for the stacking structure comprising of the transition metal oxide Co–O and metal electrode, which exhibits large reproducible resistance switching. The application of the external voltage by the C‐AFM cantilever decreases the resistance of Co–O, which well accords with the non‐polar forming process observed in the Pt/Co–O/Pt trilayer, known as the candidate of resistance random access memory (ReRAM). Furthermore, the KFM and micro XPS experimentally revealed that the local reductive reaction of Co–O possibly nucleates the defect related energy levels which dominates the current conduction in the low resistance state. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
66.
Kalina Kostova Annalaura Lorenzi-Riatsch Yoshihiko Nakashita Manfred Hesse 《Helvetica chimica acta》1982,65(1):249-251
Synthesis of Macrocyclic Lactones by Ring Enlargement Reaction Treatment of 3-(1-nitro-2-oxocyclohexyl)propanal ( 1 ) prepared by Michael addition of 2-nitrocyclohexanon and acrylaldehyde with methyltri (2-propoxy)tita-nium yielded a mixture of 2 and 3 which was converted into 6-nitro-9-decanolide ( 4 ). 相似文献
67.
Yoshihiko Onogi James L. White John F. Fellers 《Journal of Polymer Science.Polymer Physics》1980,18(4):663-682
A comparative structural investigation of the characteristics of polymer liquid-crystalline solutions including Kevlar® (PPD-T)/sulfuric acid, poly(Cl-p-phenylene terephthalamide) (Cl-PPD-T)/sulfuric acid, poly(γ-benzyl-L-glutamate) (PγBLG)/dioxane, and hydroxypropyl cellulose (HPC)/water was undertaken. Experimental procedures included polarized light microscopy, light scattering, absorption spectra, and x-ray diffraction on solutions at various concentrations and temperatures. Both the two-phase region at the onset of liquid-crystal formation and the wholly anisotropic phase were investigated. Each solution exhibited distinctive characteristics. The PPD-T and Cl-PPD-T solutions were nematic, and the PγBLG and HPC solutions were cholesteric. In the two-phase region the PPD-T, Cl-PPD-T, and PγBLG (but apparently not the HPC) exhibited negatively birefringent spherulites and aggregates of spherulites. The HPC solutions only exhibited spherulitic structures in the single-phase anisotropic system. The structures and orientations in the anisotropic phase for the various polymer solutions is considered. The helicoidal structural characteristics of the PγBLG and HPC solutions are contrasted. 相似文献
68.
The cationic ruthenium catalyst (Cp*RuCl2)2/AgOTf/Ligand promotes the addition reaction of carboxylic acids across olefins without beta-hydride elimination. 相似文献
69.
Yamamoto Y Arakawa T Ogawa R Itoh K 《Journal of the American Chemical Society》2003,125(40):12143-12160
In the presence of a catalytic amount of Cp*RuCl(cod), 1,6-diynes chemoselectively reacted with monoalkynes at ambient temperature to afford the desired bicyclic benzene derivatives in good yields. A wide variety of diynes and monoynes containing functional groups such as ester, ketone, nitrile, amine, alcohol, sulfide, etc. can be used for the present ruthenium catalysis. The most significant advantage of this protocol is that the cycloaddition of unsymmetrical 1,6-diynes with one internal alkyne moiety regioselectively gave rise to meta-substituted products with excellent regioselectivity. Completely intramolecular alkyne cyclotrimerization was also accomplished using triyne substrates to obtain tricyclic aromatic compounds fused with 5-7-membered rings. A ruthenabicycle complex relevant to these cyclotrimerizations was synthesized from Cp*RuCl(cod) and a 1,6-diyne possessing phenyl terminal groups, and its structure was unambiguously determined by X-ray analysis. The intermediary of such a ruthenacycle intermediate was further confirmed by its reaction with acetylene, giving rise to the expected cycloadduct. The density functional study on the cyclotrimerization mechanism elucidated that the cyclotrimerization proceeds via oxidative cyclization, producing a ruthenacycle intermediate and subsequent alkyne insertion initiated by the formal [2 + 2] cycloaddition of the resultant ruthenacycle with an alkyne. 相似文献
70.
A. Ueda H. Ohta S. Okubo Z. Hiroi M. Okumura M. Takano 《Applied magnetic resonance》2000,19(3-4):399-402
Quasi-one-dimensional (1-D) cupric oxide Ca1?xCuO2 (x = 0.164) is the system with 25–40% hole-doped edge-sharing CuO2 chains. However, the holes are almost localized in Ca1?xCuO2 and its magnetic susceptibility with a peak at 30 K was explained by the model considering both 1-D antiferromagnetic chains and spin dimers (Z. Hiroi, M. Okumura, Y. Nabeshima, T. Yamada, M. Takano: J. Phys. Soc. Jpn.69, 1824, 2000). To clarify the magnetic nature of Ca1?xCuO2, we performed submillimeter-wave electron spin resonance (ESR) measurements on a powder sample of Ca0.83?6CuO2. The resonance above 12 K showed typical powder ESR of Cu2+ and theg-values were determined to be g∥= 2.33 and g⊥ = 2.06 from the analysis. The resonance below 12 K changed completely from ESR. The frequency-field relation of ESR at 1.8 K clearly showed the easy-axis type antiferromagnetic resonance. 相似文献