全文获取类型
收费全文 | 258篇 |
免费 | 9篇 |
专业分类
化学 | 222篇 |
晶体学 | 1篇 |
力学 | 1篇 |
数学 | 8篇 |
物理学 | 35篇 |
出版年
2023年 | 2篇 |
2022年 | 2篇 |
2021年 | 6篇 |
2020年 | 3篇 |
2019年 | 4篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 5篇 |
2014年 | 7篇 |
2013年 | 15篇 |
2012年 | 14篇 |
2011年 | 13篇 |
2010年 | 6篇 |
2009年 | 4篇 |
2008年 | 26篇 |
2007年 | 15篇 |
2006年 | 19篇 |
2005年 | 17篇 |
2004年 | 17篇 |
2003年 | 12篇 |
2002年 | 10篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 3篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1994年 | 6篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 7篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1970年 | 2篇 |
1939年 | 1篇 |
排序方式: 共有267条查询结果,搜索用时 15 毫秒
81.
Psilocin analogs having either a formyl group (9-12) or a bromine atom (13-18) at the 5- or 7-position have been prepared for the first time. Syntheses of 5- and 7-bromo derivatives of 4-hydroxy- (23, 24, 28) and 4-benzyloxyindole-3-carbaldehyde (19, 25, 29, 30), 4-benzyloxyindole-3-acetonitriles (20, 31), and 4-benzyloxy-N,N-dimethyltryptamine (32, 34, 35) have also been established. 相似文献
82.
Controlled ring‐opening polymerization of l‐lactide and ε‐caprolactone catalyzed by aluminum‐based Lewis pairs or Lewis acid alone 下载免费PDF全文
Yuushou Nakayama Shunsuke Kosaka Kentaro Yamaguchi Gentaro Yamazaki Ryo Tanaka Takeshi Shiono 《Journal of polymer science. Part A, Polymer chemistry》2017,55(2):297-303
Ring‐opening polymerization of cyclic esters was studied using catalysts composed of bulky Lewis acids (LA) and Lewis bases (LB). Controlled polymerization of l ‐lactide (l ‐Lac) was proceeded by Al(C6F5)3·THF in combination with trimesitylphosphine (Mes3P) or triphenylphosphine (Ph3P) using BnOH as an initiator to produce poly(l ‐Lac) with narrow molecular weight distribution (MWD; Mw/Mn = 1.1). Both the LA and the LB were indispensable to promote the polymerization. The molecular weights of the resulting poly(l ‐Lac)s were controlled by the feed monomer to initiator ratio. ε‐Caprolactone (CL) was rapidly polymerized by Al(C6F5)3·THF with or without Mes3P, although the resulting polymer had rather broad MWD (Mw/Mn = 1.7). The CL polymerization by Al(C6F5)3·THF alone at r.t. gave poly(CL) with relatively narrow MWD (Mw/Mn = 1.2). © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 297–303 相似文献
83.
Daikoku S Ono Y Ohtake A Hasegawa Y Fukusaki E Suzuki K Ito Y Goto S Kanie O 《The Analyst》2011,136(5):1046-1050
An analysis of the glycan processing event is of particular importance to understand the nontemplate dependent synthetic mechanism of the multiple glycosylation reactions taking place in the Golgi apparatus in connection with the post-translational modification of biomolecules. In our efforts to address the issue, we constructed an analysis platform using nano-liquid chromatography (LC), which also worked as a spray tip, with an optical-fiber-based blue (470 nm) light emitting diode (LED)-induced fluorescence (520 nm) detector coupled with a microelectrospray ionization (ESI)-quadrupole ion trap (QIT)-time of flight (TOF) mass spectrometer (MS). This system was designed to enable both quantitative and qualitative analyses of fluorescently tagged molecules such as BODIPY-tagged lactosylceramide. Owing to the zero dead volume after LC separation, an extremely high sensitivity was achieved for the quantitative analysis (260 amol). It was also shown that a simultaneous online structural analysis based on MS could be achieved for the same quantity of analyte. To further demonstrate its potential, an enzymatic reaction of fluorescently tagged lactosylceramide using sialyltransferase was carried out, and the conversion yield was obtained on the basis of fluorescence detection. In addition, the structural details of a product, sialyl lactosylceramide, were obtained by MS and MS/MS analyses. 相似文献
84.
Yuji Tada Narimasa Moriya Takashi Inoue Atsuko Suzuki Shigeto Koyama 《Phosphorus, sulfur, and silicon and the related elements》2013,188(12):1555-1567
Abstract Novel cyclotriphosphazenes containing cyanato group (PZCN) derivatives were synthesized by a substitution reaction of 4-hydroxyphenoxycyclotriphosphazenes and cyanogen bromide (BrCN) in the presence of triethylamine (TEA). The PZCNs were characterized by FT-IR, liquid chromatography–mass spectrometry (LC-MS), 1H NMR, 13C NMR, and 31P NMR spectroscopy. Curing reactions of the PZCNs were evaluated by FT-IR spectroscopy, thermogravimetry/differential thermal analysis (TG/DTA), and differential scanning, calorimetry (DSC). The PZCNs exhibited an exothermic peak due to curing within the temperature range of 140–300°C by DSC. The PZCNs were completely cured at 220°C. The cured PZCNs exhibited high thermal stability up to 350°C, a high char-forming capability, and electrical properties, such as dielectric constants (Dks) between 2.68 and 2.87, and dissipation factors (Dfs) between 0.008 and 0.013 at 1 MHz. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. 相似文献
85.
Kentaro Kosaka Yoshihiro Ohta Tsutomu Yokozawa 《Macromolecular rapid communications》2015,36(4):373-377
Although water promotes Suzuki–Miyaura coupling reaction, it also induces side reactions such as deboronation and dehalogenation. Therefore, Suzuki–Miyaura polymerization of triolborate halothiophene monomer 1 with tBu3PPd(o‐tolyl)Br ( 2 ) in dry tetrahydrofuran (THF) is investigated. However, the resultant poly(3‐hexylthiophene) (P3HT) shows a broad molecular weight distribution and uncontrolled polymer ends. Model reactions of a number of boron reagents 3 with 2,5‐dibromothiophene ( 4 ) in the presence or absence of water indicate that intramolecular transfer of the catalyst is hardly affected by the boron moiety of 3 , whereas it is hindered in the absence of water. Indeed, polymerization of 1 with 2 in H2O/THF affords P3HT with a narrower molecular weight distribution and controlled tolyl/H ends, as compared to the reaction in dry THF.
86.
Shokichi Tsukamoto Masahiro Takeuchi Takeharu Kawaguchi Emi Togasaki Atsuko Yamazaki Yasumasa Sugita Tomoya Muto Shio Sakai Yusuke Takeda Chikako Ohwada Emiko Sakaida Naomi Shimizu Keigo Nishii Meizi Jiang Koutaro Yokote Hideaki Bujo Chiaki Nakaseko 《Experimental & molecular medicine》2014,46(4):e89
LR11, also known as SorLA or SORL1, is a type-I membrane protein from which a large extracellular part, soluble LR11 (sLR11), is released by proteolytic shedding on cleavage with a disintegrin and metalloproteinase 17 (ADAM17). A shedding mechanism is presumed to have a key role in the functions of LR11, but the evidence for this has not yet been demonstrated. Tetraspanin CD9 has been recently shown to regulate the ADAM17-mediated shedding of tumor necrosis factor-α and intercellular adhesion molecule-1 on the cell surface. Here, we investigated the role of CD9 on the shedding of LR11 in leukocytes. LR11 was not expressed in THP-1 monocytes, but it was expressed and released in phorbol 12-myristate 13-acetate (PMA)-induced THP-1 macrophages (PMA/THP-1). Confocal microscopy showed colocalization of LR11 and CD9 proteins on the cell surface of PMA/THP-1. Ectopic neo-expression of CD9 in CCRF-SB cells, which are LR11-positive and CD9-negative, reduced the amount of sLR11 released from the cells. In contrast, incubation of LR11-transfected THP-1 cells with neutralizing anti-CD9 monoclonal antibodies increased the amount of sLR11 released from the cells. Likewise, the PMA-stimulated release of sLR11 increased in THP-1 cells transfected with CD9-targeted shRNAs, which was negated by treatment with the metalloproteinase inhibitor GM6001. These results suggest that the tetraspanin CD9 modulates the ADAM17-mediated shedding of LR11 in various leukemia cell lines and that the association between LR11 and CD9 on the cell surface has an important role in the ADAM17-mediated shedding mechanism. 相似文献
87.
88.
89.
Hirao A Akiyama T Okujima T Yamada H Uno H Sakai Y Aramaki S Ono N 《Chemical communications (Cambridge, England)》2008,(39):4714-4716
Soluble precursors of 2,3-naphthalocyanine (Nc) and phthalocyanine (Pc) were prepared and were converted into insoluble semiconducting thin films of Pc and Nc by heating after fabrication via spin-coating. 相似文献
90.
A cationic gold(I) complex with a semihollow-shaped trialkynylphosphine catalyzed 5-exo-dig and 6-endo-dig cyclizations of various internal alkynic beta-keto esters, showing a marked advantage over a gold(I)-PPh3 complex with respect to the rates of the reactions and the product yields. It is proposed that the gold-bound alkynic substrate in a catalytic pocket must be somewhat folded and that such a steric effect makes the carbon-carbon bond formation entropically more favorable. 相似文献