全文获取类型
收费全文 | 826篇 |
免费 | 42篇 |
国内免费 | 4篇 |
专业分类
化学 | 699篇 |
晶体学 | 5篇 |
力学 | 7篇 |
数学 | 108篇 |
物理学 | 53篇 |
出版年
2023年 | 10篇 |
2022年 | 10篇 |
2021年 | 21篇 |
2020年 | 19篇 |
2019年 | 24篇 |
2018年 | 20篇 |
2017年 | 14篇 |
2016年 | 23篇 |
2015年 | 29篇 |
2014年 | 30篇 |
2013年 | 56篇 |
2012年 | 55篇 |
2011年 | 75篇 |
2010年 | 38篇 |
2009年 | 29篇 |
2008年 | 47篇 |
2007年 | 54篇 |
2006年 | 51篇 |
2005年 | 39篇 |
2004年 | 46篇 |
2003年 | 29篇 |
2002年 | 26篇 |
2001年 | 7篇 |
2000年 | 5篇 |
1999年 | 7篇 |
1998年 | 5篇 |
1997年 | 7篇 |
1996年 | 8篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1973年 | 5篇 |
1972年 | 2篇 |
1944年 | 2篇 |
1940年 | 2篇 |
1937年 | 2篇 |
1926年 | 3篇 |
排序方式: 共有872条查询结果,搜索用时 15 毫秒
51.
High water‐content thermoresponsive hydrogels via electrostatic macrocrosslinking of cellulose nanofibrils 下载免费PDF全文
Tobias Ingverud Emma Larsson Guillaume Hemmer Ramiro Rojas Michael Malkoch Anna Carlmark 《Journal of polymer science. Part A, Polymer chemistry》2016,54(21):3415-3424
Atom transfer radical polymerization (ATRP) has been utilized to synthesize tri‐ and star‐block copolymers of poly(di(ethylene glycol)methyl ether methacrylate) (PDEGMA) and quaternized poly(2‐(dimethylamino)ethyl methacrylate) (qPDMAEMA). The block copolymers, all with a minimum of two cationically charged blocks, were sequentially used for electrostatic macrocrosslinking of a dilute dispersion of anionic TEMPO‐oxidized cellulose nanofibrils (CNF, 0.3 wt%), forming free‐standing hydrogels. The cationic block copolymers adsorbed irreversibly to the CNF, enabling the formation of ionically crosslinked hydrogels, with a storage modulus of up to 2.9 kPa. The ability of the block copolymers to adsorb to CNF was confirmed by quartz crystal microbalance with dissipation monitoring (QCM‐D) and infrared spectroscopy (FT‐IR), and the thermoresponsive properties of the hydrogels were investigated by rheological stress and frequency sweep, and gravimetric measurements. This method was shown to be promising for the facile production of thermoresponsive hydrogels based on CNF. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3415–3424 相似文献
52.
Emma Sotelo-Gonzalez María T. Fernandez-ArgüellesJose M. Costa-Fernandez Alfredo Sanz-Medel 《Analytica chimica acta》2012
Quantum dot (QD) nanoparticles (NPs) are increasingly used as highly valuable fluorescent biomarkers and as sensitive (bio)chemical probes. Interestingly, if certain metal impurities are incorporated during the NPs synthesis, phosphorescent QDs with analytical potential can be obtained. 相似文献
53.
54.
55.
56.
[reaction: see text] A short, high-yielding synthesis of the C-glucoside 8,10-di-O-methylbergenin is reported. Key elements of the synthesis are a stereoselective installation of a beta-C-aryl linkage, a palladium(0)-catalyzed aryl carbonylation, and a regioselective lactonization reaction. This pathway should allow access to a host of bergenin analogues. 相似文献
57.
Kubo K Akemoto M Anderson S Aoki T Araki S Bane KL Blum P Corlett J Dobashi K Emma P Frisch J Fukuda M Guo Z Hasegawa K Hayano H Higo T Higurashi A Honda Y Iimura T Imai T Jobe K Kamada S Karataev P Kashiwagi S Kim E Kobuki T Kotseroglou T Kurihara Y Kuriki M Kuroda R Kuroda S Lee T Luo X McCormick DJ McKee B Mimashi T Minty M Muto T Naito T Naumenko G Nelson J Nguyen MN Oide K Okugi T Omori T Oshima T Pei G Potylitsyn A Qin Q Raubenheimer T Ross M Sakai H Sakai I Schmidt F Slaton T Smith H 《Physical review letters》2002,88(19):194801
Electron beams with the lowest, normalized transverse emittance recorded so far were produced and confirmed in single-bunch-mode operation of the Accelerator Test Facility at KEK. We established a tuning method of the damping ring which achieves a small vertical dispersion and small x-y orbit coupling. The vertical emittance was less than 1% of the horizontal emittance. At the zero-intensity limit, the vertical normalized emittance was less than 2.8 x 10(-8) rad m at beam energy 1.3 GeV. At high intensity, strong effects of intrabeam scattering were observed, which had been expected in view of the extremely high particle density due to the small transverse emittance. 相似文献
58.
B.M. Craven C. Cusatis G.L. Gartland E.A. Vizzini 《Journal of Molecular Structure》1973,16(2):331-342
X-ray crystal structure determinations show systematic perturbations of the order of 0.01 Å in the oxopyrimidine rings of twelve barbiturate molecules. They appear to be related to the mode of intermolecular NHβO hydrogen bonding. 相似文献
59.
The regioselectivity of the nitrous acid mediated dealkylation of 4-substituted-N-ethyl-N-methylanilines is a function of the acidity of the reaction mixture. At high acidity deethylation predominates, whereas demethylation is the predominant reaction in nitrosamine formation at pH 2 and above. In some cases the regioselectivity of nitrosative dealkylation changes as the run proceeds. Through the use of the corresponding 4-nitroaniline as the primary substrate, CIDNP, kinetics, kinetic deuterium isotope effects and other transformations involving nitrosations with NO2 or NOBF4 in aprotic solvents, a new mechanism of tertiary amine nitrosation has been deduced and proposed to explain regioselective deethylation. The mechanism involves the oxidation of the substrate to the amine radical cation by NO+. This is followed by the abstraction of a hydrogen atom from the carbon adjacent to the amine nitrogen by NO2 to produce an iminium ion which reacts further to produce the corresponding aldehyde and the nitrosamine. Depending upon the acidity, this process competes with three other mechanistic pathways, two of which give the nitrosamine through the iminium ion, and one leads to the formation of C-nitro compounds. The competing pathways to nitrosamine formation involve NOH elimination from a nitrosammonium ion and deprotonation of the radical cation to give an alpha-amino radical which rapidly oxidized to the iminium ion. Predominant, but not highly regioselective demethylation occurs by these pathways. Nitro compound formation principally arises from the reaction of NO2 with the radical cation followed by deprotonation, but also occurs by para C-nitrosation followed by oxidation. 相似文献
60.