全文获取类型
收费全文 | 8216篇 |
免费 | 368篇 |
国内免费 | 42篇 |
专业分类
化学 | 5725篇 |
晶体学 | 20篇 |
力学 | 208篇 |
数学 | 1430篇 |
物理学 | 1243篇 |
出版年
2023年 | 77篇 |
2022年 | 115篇 |
2021年 | 136篇 |
2020年 | 190篇 |
2019年 | 191篇 |
2018年 | 117篇 |
2017年 | 117篇 |
2016年 | 357篇 |
2015年 | 319篇 |
2014年 | 300篇 |
2013年 | 477篇 |
2012年 | 565篇 |
2011年 | 663篇 |
2010年 | 381篇 |
2009年 | 329篇 |
2008年 | 522篇 |
2007年 | 468篇 |
2006年 | 447篇 |
2005年 | 416篇 |
2004年 | 352篇 |
2003年 | 317篇 |
2002年 | 290篇 |
2001年 | 169篇 |
2000年 | 122篇 |
1999年 | 120篇 |
1998年 | 94篇 |
1997年 | 102篇 |
1996年 | 103篇 |
1995年 | 85篇 |
1994年 | 59篇 |
1993年 | 62篇 |
1992年 | 53篇 |
1991年 | 36篇 |
1990年 | 36篇 |
1989年 | 29篇 |
1988年 | 34篇 |
1987年 | 26篇 |
1986年 | 31篇 |
1985年 | 24篇 |
1984年 | 22篇 |
1983年 | 14篇 |
1982年 | 22篇 |
1981年 | 16篇 |
1980年 | 18篇 |
1979年 | 10篇 |
1978年 | 21篇 |
1977年 | 13篇 |
1975年 | 11篇 |
1974年 | 13篇 |
1970年 | 8篇 |
排序方式: 共有8626条查询结果,搜索用时 0 毫秒
981.
982.
983.
Stefan Bergmann 《Mathematische Zeitschrift》1926,24(1):641-669
Ohne Zusammenfassung 相似文献
984.
Ohne Zusammenfassung 相似文献
985.
Stefan Bergmann 《Mathematische Annalen》1931,104(1):611-636
Ohne Zusammenfassung 相似文献
986.
987.
Schlapak R Armitage D Saucedo-Zeni N Latini G Gruber HJ Mesquida P Samotskaya Y Hohage M Cacialli F Howorka S 《Langmuir : the ACS journal of surfaces and colloids》2007,23(17):8916-8924
Indium tin oxide (ITO) substrates were modified with a layer of poly(amidoamine) (PAMAM) dendrimers to change their surface properties and, in particular, the substrates' work function. The functionalization procedure involved the electrostatic adsorption of positively charged PAMAM dendrimers of generation five onto negatively polarized ITO surfaces. Three different PAMAM dendrimers were used: PAMAM-NH2 and PAMAM-OH with terminal amine and hydroxyl groups, respectively, as well as Q-PAMAM-NH2, which had been prepared from PAMAM-NH2 by quaternization of the dendrimer's terminal and internal amine groups with methyl iodide. The resulting organic films were analyzed by contact angle goniometry, X-ray photoelectron spectroscopy, ellipsometry, and Kelvin probe force microscopy to confirm the presence of a dense layer. A Langmuir isotherm was derived from surface densities of fluorescence-labeled PAMAM-NH2 dendrimers from which we deduced an equilibrium binding constant, K(eq), of (1.3 +/- 0.3) x 10(5) M(-1). Kelvin probe measurements of the contact potential difference revealed a high reduction of the work function from 4.9 eV for bare ITO to 4.3 eV for ITO with a dense film of PAMAM-NH2 of generation five. PAMAM-OH and Q-PAMAM-NH2 resulted in slightly smaller work function changes. This study illustrates that the work function of ITO can be tuned by adlayers composed of PAMAM dendrimers. 相似文献
988.
989.
Heterobimetallic Phosphanido-bridged Dinuclear Complexes - Syntheses of cis-rac-[(η-C5H4R)2Zr{μ-PH(2,4,6-iPr3C6H2)}2M(CO)4] (R?Me, M?Cr, Mo; R?H, M?Mo) The zirconocene bisphosphanido complexes [(η-C5H4R)2Zr{PH(2,4,6-iPr3C6H2)}2] (R?Me, H) react with [(NBD)M(CO)4] (NBD?norbornadiene, M?Cr, Mo) to give only one diastereomer of the phosphanido-bridged heterobimetallic dinuclear complexes cis-rac-[(η-C5H4R)2Zr{μ-PH(2,4,6-iPr3C6H2)}2M(CO)4] [R?Me, M?Cr ( 1 ), Mo ( 2 ); R?H, M?Mo ( 3 )]. However, no reaction was observed between [(η-C5H5)2Zr{PH(2,4,6-tBu3 C6H2)}2] and [Pt(PPh3)4]. 1—3 were characterised spectroscopically. For 1—3 , the presence of the racemic isomer was shown by NMR spectroscopy. No reaction was observed at room temperature for 3 and CS2, (NO)BF4, Me3NO or PH(2,4,6-Me3C6H2)2. With Et2AlH or PhC?CH decomposition of 3 was observed. 相似文献
990.
The heats of combustion of trans-9,10-bis-hydroxymethyl-9,10-dihydrophenanthrene, trans-5-hydroxymethyl-5,6-dihydro-7H-dibenzo[a,c]cyclohepten-6-ol, 5-hydroxymethyl-5,6-dihydro-7H-di-benzo[a,c]cycloheptene, 6-hydroxymethyl-5,6-dihydro-7H-dibenzo[a,c]cycloheptene, 5H-dibenzo-[a,d]cyclohepten-5-ol and 5H-10,11-dihydrodibenzo[a,d]cyclohepten-5-ol were measured by means of a Gallenkamp adiabatic bomb calorimeter. Uncertainties in the determination of the heats of combustion ranged between 0.2 and 0.3%. The enthalpies of formation and atomization for the six compounds were derived. The experimental values of the heats of atomization were compared with those calculated using the Allen–Skinner bond energy scheme. Conclusions about energetic contributions which stabilize the structure of the investigated compounds were drawn. 相似文献