全文获取类型
收费全文 | 209篇 |
免费 | 3篇 |
专业分类
化学 | 108篇 |
力学 | 3篇 |
数学 | 22篇 |
物理学 | 79篇 |
出版年
2023年 | 2篇 |
2019年 | 2篇 |
2018年 | 2篇 |
2017年 | 3篇 |
2016年 | 3篇 |
2015年 | 3篇 |
2014年 | 3篇 |
2013年 | 6篇 |
2012年 | 8篇 |
2011年 | 8篇 |
2010年 | 4篇 |
2009年 | 2篇 |
2008年 | 3篇 |
2007年 | 11篇 |
2006年 | 6篇 |
2005年 | 3篇 |
2004年 | 6篇 |
2003年 | 7篇 |
2002年 | 12篇 |
2001年 | 14篇 |
2000年 | 6篇 |
1999年 | 7篇 |
1998年 | 9篇 |
1996年 | 5篇 |
1995年 | 6篇 |
1992年 | 5篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1981年 | 4篇 |
1977年 | 5篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1971年 | 2篇 |
1970年 | 3篇 |
1968年 | 2篇 |
1965年 | 1篇 |
1962年 | 1篇 |
1939年 | 1篇 |
1928年 | 1篇 |
1927年 | 1篇 |
1881年 | 1篇 |
1879年 | 3篇 |
1876年 | 1篇 |
1873年 | 2篇 |
1872年 | 2篇 |
1867年 | 1篇 |
排序方式: 共有212条查询结果,搜索用时 547 毫秒
61.
Perfluoromethyl Element Ligands. XLIII [1] Novel Synthetic Routes to Binuclear Complexes of the Type MM′(CO)8ER2X (M/M′ = Mn/Mn, Mn/Re, Re/Re; E = P, As; R = CF3, Me; X = Hal, ) Mn(CO)5I reacts with compounds of the type (CF3)2EAsMe2 (E = P, As) as with the symmetric E2(CF3)4 ligands in the first step with cleavage of the E‐As bond to yield the pro ducts (CO)5MnE(CF3)2 and Me2AsI. Reaction of the mononuclear complexes with excess of Mn(CO)5I leads in good yields to the known dinuclear compounds (CO)4Mn[E(CF3)2, I]Mn(CO)4 and CO. Me2AsI, the second product of the EAs cleavage, attacks the starting compound Mn(CO)5I giving cis‐Mn(CO)4I(AsMe2I) and CO. This result encouraged us to thoroughly investigate the preparation of cis‐M(CO)4X(EMe2Y) complexes with most of the possible combinations of M = Mn, Re; E = P, As and X, Y = Cl, Br, I. An alternative route to these compounds was opened by the cleavage of the dinuclear manganese or rhenium halides M2(CO)8X2 with the halophosphanes or ‐arsanes Me2EY. This route was found to be especially advantageous for the preparation of the rheniumcarbonyl precursors, since milder conditions than for the CO‐substitution in Re(CO)5X compounds are sufficient for the halogen‐bridged dinuclear complexes. Cis‐M(CO)4X(EMe2Y) complexes were used as precursors for the synthesis of novel homo‐ and heterodinuclear complexes of the type (CO)4M(EMe2, X)M′(CO)4 by reacting the EY function with transition metal carbonylates Kat[M′(CO)5] (Kat = Na, Bu4N, Ph4As). Thus the preparation of a wide range of complexes was possible, which before had been successfully prepared by the direct reaction of Mn2(CO)10 with Me2EX only in few cases, e. g. with Me2AsI. Spectroscopic investigations, using the CO valence frequencies and the 1H‐NMR data of the ligands EMe2Y or of the Me2E bridges, were applied to study the influence of the variables M, M′, E, X, Y and Kat on the reactivity of the mononuclear complexes and the bonding situation in both the mono‐ and the dinuclear systems. The new compounds were characterized by spectroscopic (IR, NMR, MS) and analytic methods (C, H). 相似文献
62.
63.
64.
-1 (for 0.25 mJ/cm2). The response function of the total experimental setup is derived from the optoacoustic signal of a black absorber, which
is necessary to correct theoretical calculations with regard to the finite time response of the detection system. In the case
of homogeneous samples, the theory of optoacoustic signal generation is verified, qualitative results are achieved with layered
samples.
Received: 14 October 1998 / Published online: 24 February 1999 相似文献
65.
Zhaohui Tang Changquan Qiu Jeffrey R. McCutcheon Kyunghwan Yoon Hongyang Ma Dufei Fang Eric Lee Clint Kopp Benjamin S. Hsiao Benjamin Chu 《Journal of Polymer Science.Polymer Physics》2009,47(22):2288-2300
A novel class of high‐flux and low‐fouling thin‐film nanofibrous composite (TFNC) membranes, containing a thin hydrophilic top‐layer coating, a nanofibrous mid‐layer scaffold and a non‐woven microfibrous support, has been demonstrated for nanofiltration (NF) applications. In this study, the issues related to the design and fabrication of a polyethersulfone (PES) electrospun nanofibrous scaffold for TFNC NF membranes were investigated. These issues included the influence of solvent mixture ratio, solute concentration, additives, relative humidity (RH), and solution flow rate on the morphology of an electrospun PES nanofibrous scaffold, the distribution of fiber diameter, the adhesion between the PES scaffold and a typical poly(ethylene terephthalate) (PET) non‐woven support, as well as the tensile properties of the nanofibrous PES/non‐woven PET composite substrates. Uniform and thin nanofibrous PES scaffolds with strong adhesion to the nanofiber‐PET non‐woven are several of the key parameters to optimize the NF performance of TFNC membranes. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2288–2300, 2009 相似文献
66.
67.
C. Kopp 《Fresenius' Journal of Analytical Chemistry》1881,20(1):298
Ohne Zusammenfassung 相似文献
68.
E. Kopp 《Analytical and bioanalytical chemistry》1873,12(1):210-211
69.
Cronin-Hennessey D Kwon Y Lyon AL Thorndike EH Jessop CP Mariske H Perl ML Savinov V Ugolini D Zhou X Coan TE Fadeyez V Maravin Y Narsky I Stroynowski R Ye J Wlodek T Artuso M Ayad R Boulahouache C Bukin K Dambasuren E Karamnov S Kopp S Majumder G Moneti GC Mountain R Schuh S Skwarnicki T Stone S Viehauser G Wang JC Wolf A Wu J Csorna SE Danko I McLean KW Márka S Xu Z Godang R Kinoshita K Lai IC Schrenk S Bonvicini G Cinabro D Perera LP Zhou GJ Eigen G Lipeles E Sharma V 《Physical review letters》2000,85(3):515-519
We have studied charmless hadronic decays of B mesons into two-body final states with kaons and pions and observe three new processes with the following branching fractions: beta(B-->pi(+)pi(-)) = (4.3(+1. 6)(-1.4)+/-0.5)x10(-6), beta(B-->K(0)pi(0)) = (14.6(+5.9+2.4)(-5.1-3. 3))x10(-6), and beta(B-->K(+)/-pi(0)) = (11.6(+3.0+1.4)(-2.7-1.3))x10(-6). We also update our previous measurements for the decays B-->K(+)/-pi(-/+) and B+/--->K(0)pi(+/-). 相似文献
70.
Richichi SJ Severini H Skubic P Undrus A Chen S Fast J Hinson JW Lee J Menon N Miller DH Shibata EI Shipsey IP Pavlunin V Cronin-Hennessey D Kwon Y Lyon AL Thorndike EH Jessop CP Marsiske H Perl ML Savinov V Ugolini D Zhou X Coan TE Fadeyev V Maravin Y Narsky I Stroynowski R Ye J Wlodek T Artuso M Ayad R Boulahouache C Bukin K Dambasuren E Karamnov S Kopp S Majumder G Moneti GC Mountain R Schuh S Skwarnicki T Stone S Viehauser G Wang JC Wolf A Wu J Csorna SE Danko I Zhou GJ 《Physical review letters》2000,85(3):520-524
In a sample of 19 x 10(6) produced B mesons, we have observed the decays B-->eta K(*) and improved our previous measurements of B-->eta'K. The branching fractions we measure for these decay modes are B(B+-->eta K(*+)) = (26.4(+9.6)(-8.2)+/-3.3)x10(-6), B(B(0)-->eta K(*0)) = (13.8(+5.5)(-4.6)+/-1.6)x10(-6), B(B(+)-->eta'K(+) = (80(+10)(-9)+/-7)x10(-6), and B(B(0)-->eta'K0) = (89(+18)(-16)+/-9)x10(-6). We have searched with comparable sensitivity for related decays and report upper limits for these branching fractions. 相似文献