全文获取类型
收费全文 | 305篇 |
免费 | 5篇 |
国内免费 | 1篇 |
专业分类
化学 | 212篇 |
晶体学 | 2篇 |
力学 | 22篇 |
数学 | 33篇 |
物理学 | 42篇 |
出版年
2021年 | 5篇 |
2020年 | 4篇 |
2016年 | 5篇 |
2015年 | 4篇 |
2014年 | 3篇 |
2013年 | 7篇 |
2012年 | 14篇 |
2011年 | 8篇 |
2010年 | 8篇 |
2009年 | 8篇 |
2008年 | 9篇 |
2007年 | 15篇 |
2006年 | 16篇 |
2005年 | 17篇 |
2004年 | 10篇 |
2003年 | 11篇 |
2002年 | 8篇 |
2001年 | 2篇 |
2000年 | 11篇 |
1999年 | 2篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 5篇 |
1990年 | 7篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 8篇 |
1984年 | 8篇 |
1983年 | 10篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1975年 | 6篇 |
1974年 | 4篇 |
1973年 | 2篇 |
1972年 | 4篇 |
1970年 | 4篇 |
1969年 | 4篇 |
1968年 | 2篇 |
1967年 | 2篇 |
1930年 | 2篇 |
1925年 | 2篇 |
排序方式: 共有311条查询结果,搜索用时 0 毫秒
1.
Ammar R Ball RC Banerjee S Bhat PC Bosetti P Bromberg C Canough GE Coffin T Dershem TO Dixon RL Fenker HC Ganguli SN Gensch U Girtler P Goshaw AT Grard F Gurtu A Hamilton C Henri VP Hernandez JJ Hrubec J Iori M Jones LW Kuhn D Knauss D Leedom ID Legros P Lemonne J Leutz H Liu X Malhotra PK Marraffino JM Mendez GE Miller R Naumann T Nguyen A Nowak H Pilette P Poirier J Poppleton A Raghavan R Rasner K Reucroft S Robertson WJ Roe BP Roth A Senko M Struczinski W Subramanian A Touboul MC Vonck B 《Physical review letters》1988,61(19):2185-2188
2.
Heterobinuclear oxometalate anions based upon [CrMoO7]2-, [CrWO7]2-, and [MoWO7]2- were generated and transferred to the gas phase by the electrospray process from acetonitrile solutions containing two of the salts (Bu4N)2[MO4] (M = Cr, Mo, W). Their reactivities were examined and compared with those of the related homobinuclear anions based upon [M2O7]2- (M = Cr, Mo, W). Particular emphasis was placed upon reactions relevant to gas-phase catalytic cycles described previously for oxidation of alcohols by [Mo2O6(OH)]- (Waters, T.; O'Hair, R. A. J.; Wedd, A. G. J. Am. Chem. Soc. 2003, 125, 3384-3396). The protonated anions [MM'O6(OH)]- each reacted with methanol with loss of water to form [MM'O6(OCH3)]- at a rate that was intermediate between those of [M2O6(OH)]- and [M'2O6(OH)]-. The butylated anions [MM'O6(OBu)]- were generated by collisional activation of the ion-pairs {Bu4N+ [MM'O7]2-}-. Collisional activation of [MM'O6(OBu)]- resulted in either the loss of butanal (redox reaction) or the loss of butene (elimination reaction), with the detailed nature of the observations depending on the nature of both M and M'. Selective 18O labeling indicated that the butoxo ligands of [CrMoO6(OBu)]- and [CrWO6(OBu)]- were located on molybdenum and tungsten, respectively. This structural insight allowed a more detailed comparison of reactivity with the homobinuclear species, and highlighted the importance of the neighboring metal center in these reactions. 相似文献
3.
Abstract— A haploid respiration-deficient (ρ- ) mutant of Saccharomyces cerevisiae exhibits a lower ability to excise ultraviolet-induced pyrimidine dimers in various post-irradiation treatments as compared to the original respiration-competent wild-type strain. This decrease in excision may account for the inability of ρ- strains to show liquid-holding recovery. 相似文献
4.
McMorris TC Yu J Lira R Dawe R MacDonald JR Waters SJ Estes LA Kelner MJ 《The Journal of organic chemistry》2001,66(18):6158-6163
Many analogues of the antitumor agent irofulven have been readily prepared by replacing the allylic hydroxyl with a variety of nucleophiles. Analogues of acylfulvene (the precursor to irofulven) were also prepared by Michael reaction with acrolein. The toxicity of the analogues was determined, as well as preclinical antitumor activity. Several analogues exhibited good activity in mouse xenografts. Structural requirements for activity are discussed. 相似文献
5.
6.
J. A. Waters George A. Mortimer 《Journal of polymer science. Part A, Polymer chemistry》1972,10(6):1827-1837
Soluble ethylene polymerization catalysts derived from (π-C5H5)2Ti(R)Cl and R ′AlCl2, where R = methyl or phenyl and R ′ = methyl or ethyl, were studied both by polymerization kinetics at 0°C and by diagnostic experiments. It was found that the first insertion of ethylene into the Ti? R bond is difficult when R = methyl or phenyl, and for this reason these catalysts show a different overall behavior than when R = ethyl or higher alkyl. 相似文献
7.
Jessica E. Waters Georg Berger Dr. Andrew J. Peel Dr. Raúl García-Rodríguez Dr. Andrew D. Bond Prof. Dominic S. Wright 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(47):12036-12040
Supramolecular main group chemistry is a developing field which parallels the conventional domain of metallo-organic chemistry. Little explored building blocks in this area are main group metal-based ligands which have the appropriate donor symmetry to build desired molecular or extended arrangements. Tris(pyridyl) main group ligands (E(py)3, E=main group metal) are potentially highly versatile building blocks since shifting the N-donor arms from the 2- to the 3-positions and 4-positions provides a very simple way of changing the ligand character from mononuclear/chelating to multidentate/metal-bridging. Here, the coordination behaviour of the first main group metal tris(4-pyridyl) ligands, E(4-py)3 (E=Sb, Bi, Ph−Sn) is explored, as well as their ability to build metal-organic frameworks (MOFs). The complicated topology of these MOFs shows a marked influence on the counter anion and on the ability of the E(4-py)3 ligands to switch coordination mode, depending on the steric and donor character of the bridgehead. This structure-directing influence of the bridgehead provides a potential building strategy for future molecular and MOF design in this area. 相似文献
8.
A designed 12-residue beta-hairpin peptide with a diagonal tryptophan (Trp) pair was shown to bind ATP in water through a combination of aromatic and electrostatic interactions. The affinity for ATP was 5800 M-1 (DeltaG approximately -5.0 kcal/mol), a remarkable affinity for a short, structured peptide in water, consisting of entirely natural amino acid residues. Proton NMR measurements indicate that the adenine ring of the nucleotide is intercalated between the diagonal tryptophans in the bound state. Delineation of the contributions to ATP binding to the hairpin suggest that aromatic interactions contribute approximately -1.8 kcal/mol, while individual electrostatic interactions involving the ATP phosphates and positively charged side chains of the hairpin contribute approximately -1 kcal/mol each. The designed beta-hairpin receptor presents a novel minimalist system to investigate the energetic contributions to protein-nucleic acid recognition through the surface of a beta-sheet. 相似文献
9.
Lubomír Lap?ík Barbora Lap?íková Ivo Krásny Ivana Kupská Richard W. Greenwood Kristian E. Waters 《Plasma Chemistry and Plasma Processing》2012,32(4):845-858
It was found in this study that the air plasma treatment of particular kaolinite has led to the change of its wettability, which was reflected in the decreased values of water contact angles of wetting from 88.7° for virgin kaolinite to 86.3° for 30?min air plasma treated one. Plasma treated samples show higher average surface energies in the wide range of coverage regimes in comparison to the virgin samples as determined by inverse gas chromatography. Results of these measurements confirmed our assumption, that air plasma treatment activates surface energy of the crystal planes of the kaolinite as reflected in the broadened dispersive surface energy distribution after 10?min treatment time. However with prolonged 30?min treatment time the dispersive surface energy distribution profile was decreased. We assume, that the latter decrease reflects the distorsion of the crystal lattice of the kaolinite as confirmed by FTIR analysis as reflected in changes of Si?CO?CSi and Al2O?CH characteristic absorption bands. Calculated dispersive surface free energy for 24?% surface coverage was increased from original 35?mJ/m2 to 40.3 and 40.8?mJ/m2 for 10 and 30?min treatment times. There were determined yield locus and flow function dependencies at different stress levels for virgin and different time plasma treated samples (flow index??ff c , effective angle of internal friction???? e , unconfined yield strength???? c ). It was found that by plasma treatment the character of the flow was shifting from region of very cohesive (ff c ?=?2.39) to the cohesive (ff c ?=?3.19). For untreated samples effective angle of internal friction was decreased with increasing applied consolidation stress, while for plasma treated kaolinite it was increased. 相似文献
10.
Christopher M. Timperley Matthew J. Waters 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2):423-430
The synthesis and physical properties of the first fluorinated dialkyl phosphoramidates of structure (RCH 2 O) 2 P(O)NHCH 2 R F , where R = CH 3 , CF 3 or CCl 3 and R F = CF 3 or C 2 F 5 , are described. They were obtained by treatment of the respective dialkyl phosphorochloridates with trifluoroethylamine or pentafluoropropylamine in ether in the presence of triethylamine. 相似文献