全文获取类型
收费全文 | 16701篇 |
免费 | 1630篇 |
国内免费 | 1300篇 |
专业分类
化学 | 17841篇 |
晶体学 | 147篇 |
力学 | 7篇 |
综合类 | 49篇 |
数学 | 152篇 |
物理学 | 647篇 |
综合类 | 788篇 |
出版年
2023年 | 139篇 |
2022年 | 266篇 |
2021年 | 383篇 |
2020年 | 669篇 |
2019年 | 495篇 |
2018年 | 440篇 |
2017年 | 394篇 |
2016年 | 611篇 |
2015年 | 558篇 |
2014年 | 658篇 |
2013年 | 1155篇 |
2012年 | 1649篇 |
2011年 | 823篇 |
2010年 | 698篇 |
2009年 | 828篇 |
2008年 | 946篇 |
2007年 | 1083篇 |
2006年 | 887篇 |
2005年 | 806篇 |
2004年 | 772篇 |
2003年 | 766篇 |
2002年 | 524篇 |
2001年 | 466篇 |
2000年 | 437篇 |
1999年 | 418篇 |
1998年 | 362篇 |
1997年 | 361篇 |
1996年 | 375篇 |
1995年 | 372篇 |
1994年 | 265篇 |
1993年 | 212篇 |
1992年 | 193篇 |
1991年 | 124篇 |
1990年 | 83篇 |
1989年 | 66篇 |
1988年 | 65篇 |
1987年 | 51篇 |
1986年 | 40篇 |
1985年 | 34篇 |
1984年 | 33篇 |
1983年 | 13篇 |
1982年 | 27篇 |
1981年 | 14篇 |
1980年 | 17篇 |
1979年 | 12篇 |
1978年 | 7篇 |
1977年 | 7篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 609 毫秒
71.
Dávid Szegvári Romána Zelkó Péter Horváth András Gergely 《Journal of inclusion phenomena and macrocyclic chemistry》2007,57(1-4):169-172
Enantioselective solubility of rac-norgestrel was found in the presence of γ-cyclodextrin or hydroxypropyl-γ-cyclodextrin.
In both cases the efficacious enantiomer was dissolved in greater extent. Calculating the molar absorptivity and molar ellipticity
spectra of the γ- and hydroxypropyl-γ-cyclodextrin aqueous complexes, a simple and rapid direct circular dichroism (CD) spectrometric
method was obtained for the determination of the enantiomer ratio in aqueous solutions. 相似文献
72.
73.
1 Results In addition to single wall and multiwall carbon nanotubes[1], several structures,which are more or less related to fullerenes,including carbon nanohorns[2a], carbon nanospheres[2b] and onion like carbon structures[2c] have been reported.A new simple straight forward method to access some of these structures is the solid-state pyrolysis of different organometallic complexes in a sealed vessel,which led so far to carbon nanotubes[3a,b], carbon nanocables[3c] and onions[3d]. 相似文献
74.
Perdigón-Melón J. A. Auroux A. Bonnetot B. 《Journal of Thermal Analysis and Calorimetry》2003,72(2):443-451
As supported palladium oxide catalysts present the best performances in methane combustion in lean conditions, microcalorimetric
studies of the interaction between methane and palladium oxide or metallic palladium supported on Al2O3, ZrO2 and BN have been performed at 673 K. At this temperature methane reduced the palladium oxide, and the heat of reduction of
palladium oxide was shown to depend on the dispersion and on the support. The lowest heats of reduction corresponded to the
highest rates of methane combustion. Moreover methane reforming occurred on metallic palladium, producing hydrogen, and again
methane decomposition was shown to depend on the support.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
75.
Investigation on ultrafast thrid—order optical nonlinearity of metal(dmit)2/mnt)2 Charge transfer complexes
下载免费PDF全文
![点击此处可从《中国物理》网站下载免费的PDF全文](/ch/ext_images/free.gif)
We have investigated the transient third-order optical nonlinearity of the solutions of Metal(dmit)2/(mnt)2 salts in acetone by employing femtosecond optical Kerr gate measurement at 830nm wavelength.An order of enhancement on the second-order hyperppolarizability is found for the above salts with central atoms of Cu and Ni.We have suggested an explanation for the enhancement based on the extension of electronic conjugation by the entring Cu or Ni atom. 相似文献
76.
Jean-Marc Kern Jean-Pierre Sauvage Gerard Bidan Bernadette Divisia-Blohorn 《Journal of polymer science. Part A, Polymer chemistry》2003,41(22):3470-3477
This article provides an overview of the fundamental principles of the synthesis of metallocatenanes and metallorotaxanes. It also describes the synthesis and properties of electronic conducting polymers—polypyrrole and polythiophene—built around metallocatenanes and metallorotaxanes. The particular properties of this new class of polymers, including the possibility of transmetallation reactions being performed with them and the observation of electronic coupling between the metal centers and the conducting matrix, are discussed. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3470–3477, 2003 相似文献
77.
Lanthanide Complexes for Oligomerization of Phenyl Isocyanate 总被引:1,自引:0,他引:1
IntroductionThestudyonthereactivitiesoflanthanidecomplexesto wardisocyanateshasattractedmuchattention .Ithasbeenre portedthatlanthanidealkoxides,1anddivalentdiaza pentadi enyllanthanidecomplexes2 canbeusedasthesinglecompo nentinitiatorsforisocyanatespolymerization .Recentlyourre searchgrouphasalsofoundthatlanthanoceneamide ,3diva lentaryloxideofsamarium4 ,5anddivalentsamarocene6 areallactivefortheoligomerizationofphenylisocyanate,andtheactivespeciesforthesethreesystemswereallsuccessfullyisolat… 相似文献
78.
《Magnetic resonance in chemistry : MRC》2003,41(1):61-64
Palladium(II) dichloride reacts with 1,10‐bis(2‐pyrrolyl)‐2,5,9‐triaza‐1,9‐decadiene to give a [Pd(C15H20N5)]Cl complex in which the ligand is four‐coordinated, leaving one pyrrole group dangling. By using COSY, gHSQC, gHMBC connectivities and NOE experiments it has been concluded that one linkage isomer exists in DMSO solution, in spite of the fact that different sets of N atoms of potentially pentadentate ligand might be involved in coordination, and that the three chelate rings in the complex cation are arranged in a sequence: five‐membered, six‐membered, five‐membered which is different from that (5–5–6) found by x‐ray studies on the related [Ni(C15H20N5)]Cl compound. NMR studies allowed an unambiguous assignment of all 1H and 13C NMR resonances for the complex. Results of x‐ray structural analysis of [Pd(C15H20N5)](CH3COO)H2O supported the five‐membered, six‐membered, five‐membered ring sequence in the [Pd(C15H20N5)]+ complex cation and show an E (trans) orientation of the dangling pyrrole group with respect to the metal center. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
79.
80.
N. A. Anikin A. S. Mendkovich M. B. Kuzminskiy A. M. Andreev 《Russian Chemical Bulletin》2008,57(2):428-430
A new fast computational method for mass calculations of docking complexes by the AM1/PM3 semiempirical methods is proposed.
The computation time is shortened by at least an order of magnitude compared to alternative schemes of quantum chemical calculations.
The root-mean-square deviation of the AM1 calculated energies of formation of complexes from the results obtained by conventional
diagonalization procedure is at most 0.4 kcal mol−1.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 418–420, February, 2008. 相似文献