全文获取类型
收费全文 | 1392篇 |
免费 | 38篇 |
国内免费 | 73篇 |
专业分类
化学 | 371篇 |
晶体学 | 1篇 |
力学 | 23篇 |
综合类 | 2篇 |
数学 | 140篇 |
物理学 | 966篇 |
出版年
2022年 | 8篇 |
2021年 | 10篇 |
2020年 | 9篇 |
2019年 | 6篇 |
2018年 | 13篇 |
2017年 | 17篇 |
2016年 | 41篇 |
2015年 | 19篇 |
2014年 | 26篇 |
2013年 | 21篇 |
2012年 | 27篇 |
2011年 | 69篇 |
2010年 | 55篇 |
2009年 | 38篇 |
2008年 | 40篇 |
2007年 | 29篇 |
2006年 | 69篇 |
2005年 | 91篇 |
2004年 | 138篇 |
2003年 | 139篇 |
2002年 | 81篇 |
2001年 | 86篇 |
2000年 | 22篇 |
1999年 | 33篇 |
1998年 | 27篇 |
1997年 | 17篇 |
1996年 | 22篇 |
1995年 | 22篇 |
1994年 | 8篇 |
1993年 | 24篇 |
1992年 | 20篇 |
1991年 | 11篇 |
1990年 | 22篇 |
1989年 | 30篇 |
1988年 | 45篇 |
1987年 | 19篇 |
1986年 | 23篇 |
1985年 | 15篇 |
1984年 | 17篇 |
1983年 | 8篇 |
1982年 | 7篇 |
1981年 | 13篇 |
1980年 | 8篇 |
1979年 | 6篇 |
1977年 | 3篇 |
1919年 | 3篇 |
1911年 | 4篇 |
1910年 | 3篇 |
1909年 | 3篇 |
1907年 | 3篇 |
排序方式: 共有1503条查询结果,搜索用时 15 毫秒
51.
52.
Hang GONG Nian Fa YANG? Wei Jun TANG Qing Hua FAN Li Wen YANG The College of Chemistry Xiangtan University Xiangtan Laboratory of Chemical Biology Center for Molecular Science Institute of Chemistry Chinese Academy of Sciences Beijing 《中国化学快报》2005,16(8)
Among the reactions in which C-C bonds are formed, the Baylis-Hillman coupling of aldehydes with α, β-unsaturated carbonylic compounds is currently attracting much interest due to the atom economy, the mild conditions and the generation of functional groups1,2. Furthermore, compared to the Heck, Suzuki and other palladium catalyzed C-C bond forming reaction3, the Baylis-Hillman reaction can be promoted by using organic bases in the complete absence of any metal4. However, almost all the … 相似文献
53.
DUAN Chun-Ying XIA Xu-Bing ZHU Long-Gen YOU Xiao-Zeng YANG Yao WANG Hua-QinCoordination Chemistry Institute Nanjing University The State Key Laboratory of Coordination Chemistry Nanjing Jiangsu China 《中国化学》1994,(4)
The cobalt, nickel, copper, zinc and cadmium complexes of S-methyl-N-(ferrocenyl-l-methyl-methylidene)-dithiocarbazate (H-LSM) and S-benzyl-N-(ferrocenyl-l-methyl-methylidene)-dithiocarbazate (H-LSB) were synthesized and the crystal structure of Cd[Fe-C(CH3) = NNCSS. (CH3)]2 was solved by X-ray diffraction. The crystal is in the orthorhombic system with space group Pbca, cell parameters a=19.741(3), b=19.924(5), c=15.452(4) A, and the final factors of R=0.032. The study on quenching the luminescence of Ru(bpy)3 by those complexes showed that bimolecular quenching constants obtained from the Stern-Vohner constant and the excited-state lifetime were related to the redox potential of the quencher. Linear relationship is shown in the plot of logkq vs. E1/2(Q+/Q). The main factor which influences the quenching rate constant and the redox potential is the coordinating ability of the metal in the complex. 相似文献
54.
GuoHongLI YueMaoSHEN KeQinZHANG 《中国化学快报》2005,16(3):359-361
A novel saponin was isolated from the transformed products of ginsenoside Rh1 by Bacillus subtilis. It‘s structure was determined to be 3-O-β-D-glucopyranosyl-6-O-β-D-glucopyranosyl-20 (S)-protopanaxatriol on the basis of the spectral data. 相似文献
55.
新型显色剂3,3,5,5''''-四甲基联苯胺分光光度法测定余氯的研究 总被引:2,自引:0,他引:2
本文报道了采用新型氧化还原剂3,3’,5,5’-四甲基联苯胺(TMB)测定水中总余氯的分光光度法,并对其灵敏度、稳定性、准确性作了较为详细的研究,探讨了分析条件,提出了分析方法。在pH≤2时,最大吸收峰为450 nm,表观摩尔吸光系数为6.89×10~4L·mol~(-1)·cm~(-1),可测范围为0.01~2.5 mg/L。与目前使用的传统显色剂邻联甲苯胺(DMB)相比较,具有灵敏度高,显色稳定,重现性好及使用安全等优点。 相似文献
56.
I. V. Ajinenko Y. A. Belokopitov A. A. Borovikov P. V. Chliapnikov Z. C. Garutchava L. N. Gerdyukov S. A. Gumenuk V. V. Kniazev A. I. Kurnosenko L. V. Orekhova L. P. Petrovikh V. N. Riadovikov A. G. Tomaradse V. A. Uvarov A. P. Vorobjev N. S. Amaglobely Ch. S. Chochiachvili M. Barth E. A. De Wolf M. Van Immerseel F. Verbeure CERN - USSR Collaboration 《Zeitschrift fur Physik C Particles and Fields》1984,25(2):103-114
We present final results on inclusive production ofK *+(890),K *+(1430) andK *?(890) in \(\bar K^ + p\) interactions at 32 GeV/c, based on a statistics of ~27 events/μb. Total cross sections,p T -andx-dependence of inclusive distributions are compared with experiments at other energies and with the Lund fragmentation model. Spin density matrix elements of theK *+(890) are also discussed. The results suggest that “recombination” of both initial state valence quarks \(\bar s\) andu of theK + intoK *+(890), responsible in the Lund model for ~45% of theK *+(890) cross section, is strongly suppressed. 相似文献
57.
R. Bailey D. G. Bardsley E. Belau T. Böhringer M. Bosman M. Cerrada V. Chabaud C. Damerell C. Dauin G. De Rijk H. Dijkstra A. Dwurazny A. Gillman R. Gilmore L. Görlich Z. Hajduk C. Hardwick W. Hoogland B. D. Hyams R. Klanner G. Lütjens G. Lutz J. Malos W. Männer G. Polok M. Rozanska K. Rybicki H. J. Seebrunner W. Spierenburg U. Stierlin R. J. Tappel H. G. Tiecke M. Turala J. Vermeulen G. Waltermann P. Weilhammer F. Wickens L. W. Wiggers A. Wylie T. Zeludziewicz ACCMOR Collaboration 《Zeitschrift fur Physik C Particles and Fields》1984,24(2):111-118
The reactions \(K^ - Be \to {}^(\bar K^) *^0 (890)X,\pi ^ - Be \to {}^(\bar K^) *^0 (890)X\) , have been studied in a 175 GeV unseparated hadron beam in the kinematic range 0<x F <1.0 andp T 2 <5 GeV2. Integrated cross-sections and the dependence of the cross-sections on the longitudinal and transverse momentum are presented, together with quark counting rules predictions. The nuclear dependence ofK ? fragmentation intoK *0(890) with respect to Feynmanx is investigated from hydrogen to beryllium. 相似文献
58.
I. V. Ajinenko P. V. Chliapnikov V. P. Falaleev Z. C. Garutchava L. N. Gerdyukov V. V. Kniazev A. I. Kurnosenko T. G. Makharadze V. N. Riadovikov A. M. Rybin A. G. Tomaradze O. G. Tchikilev V. F. Tchunikhin V. A. Uvarov A. P. Vorobjev N. S. Amaglobely Ch. S. Chochiachvili M. D. Tabidze M. Barth E. A. De Wolf M. Van Immerseel F. Verbeure CERN-USSR Collaboration 《Zeitschrift fur Physik C Particles and Fields》1984,23(4):307-331
The production properties ofK s 0 , \(\bar \Lambda\) andK + p interactions at 32 GeV/c are investigated using the final statistics of the experiment. We present total and semi-inclusive cross sections and aver-age multiplicities. Estimates are given of the diffractive dissociation contributions to total and differential cross sections. Thex-,p T ?, and transverse mass dependence of inclusive and semi-inclusive distributions is discussed as well as properties of “prompt”K s 0 's. The ratio of “prompt”K 890 + (K 890 0 ) to “prompt”K 0 cross sections is measured to be 1.03±0.12 (0.98±0.17). From a comparison of \(\bar \Lambda\) production inK ± p interactions at 32 GeV/c, we estimate a strange sea-quark suppression of 0.26 ±0.02. The double differential cross sections ofK s 0 's is studied as a function of Feynman-x andp T 2 , and a Triple-Regge fit performed. The data are compared in detail to versions of the Lund-model for low-p T hadronic collisions. 相似文献
59.
TIAN Yan-Ni YANG PinInstitute of Coordination Chemistry The State Key Laboratory of Coordination Chemistry Nanjing University Nanjing Jiangsu ChinaLI Qing-Shan ZHAO Chun-GuiInstitute of Molecular Science Shanxi University Taiyuan Shanxi China 《中国化学》1996,14(5):428-436
New complexes,of bis(2,2'-diamino-4,4'-bithiazole)sulfate nickel(Ⅱ) and bis(2,2'-diami-no-4,4'-bithiazole)sulfate cobalt(Ⅱ),have been prepared.The complexes were characterized by infrared and UV-Vis spectroscopy,1H NMR,elemental analyses and molar conductivity.The effect of these complexes on the DNA synthesis of sarcoma 180 cells has been studied by the technique of isotopic liquid scintillation.The results indicated that complexes show ability to inhibit DNA synthesis of the tumor cells.In order to provide a molecular basis for understanding the biological effects,the probe,[trana-en2Os(η2-H2)](CF3SO3)2 (en,ethylenediamine) as a monitor was first used to explore interaction of the complexes with 2'-deoxyguanosine-5'-monophosphate (dGMP). 相似文献
60.