全文获取类型
收费全文 | 114篇 |
免费 | 0篇 |
国内免费 | 6篇 |
专业分类
化学 | 90篇 |
晶体学 | 2篇 |
数学 | 9篇 |
物理学 | 19篇 |
出版年
2022年 | 1篇 |
2021年 | 2篇 |
2019年 | 1篇 |
2017年 | 1篇 |
2016年 | 3篇 |
2015年 | 1篇 |
2014年 | 3篇 |
2013年 | 2篇 |
2012年 | 2篇 |
2011年 | 3篇 |
2010年 | 1篇 |
2009年 | 2篇 |
2008年 | 5篇 |
2007年 | 3篇 |
2006年 | 6篇 |
2005年 | 5篇 |
2004年 | 6篇 |
2003年 | 2篇 |
2002年 | 1篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 9篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1971年 | 1篇 |
1970年 | 2篇 |
排序方式: 共有120条查询结果,搜索用时 14 毫秒
1.
Ramaswamy K Saito H Murakami H Shiba K Suga H 《Journal of the American Chemical Society》2004,126(37):11454-11455
Fx3 is an artificial ribozyme with the ability to aminoacylate various tRNAs with phenylalanine and its nonnatural derivatives. Herein we report a simple strategy to build tRNA specificity into the generic Fx3, by appending to its 3'-end a tRNA-specific sequence (TSS), which is complementary to the acceptor stem of the cognate tRNA. This new designer ribozyme, referred to as Fx10, is able to recognize its cognate tRNA via a 10-base-pair interaction that is formed after the invasion of the tRNA acceptor stem by the TSS. We have demonstrated that Fx10 can aminoacylate its cognate tRNA with a high degree of specificity and also discriminate against the noncognate tRNAs. Because the tRNA specificity can be easily programmed into Fx10, it is a custom-made catalyst to generate nonnatural aminoacyl-tRNAs. 相似文献
2.
Kulp JL Shiba K Evans JS 《Langmuir : the ACS journal of surfaces and colloids》2005,21(25):11907-11914
Single-walled carbon nanohorns (SWNHs) are interesting carbon nanostructures that have applications to science and technology. Using M13 phage display technology, polypeptides directed again SWNHs surfaces have been created for a number of nanotechnology and pharmaceutical purposes, yet the molecular mechanism of polypeptide sequence interaction and binding to SWNHs surfaces is not known. Recently, we identified a linear 12-AA M13 phage pIII sequence, NH-12-5-2 (DYFSSPYYEQLF), that binds with high affinity to SWNHs surfaces. To probe the structure of this pIII tail polypeptide further, we investigated the conformation of a model peptide representing the 12 AA NH-12-5-2 sequence. At neutral pH, the NH-12-5-2 model polypeptide is conformationally labile and exhibits two-state conformational exchange involving the D1-S5 N-terminal segment. Simultaneous with this conformational exchange process is the observation that the P6 residue exhibits imido ring conformational variation. In the presence of the structure-stabilizing solvent, TFE, or at pH 2.5, both the exchange process and Pro ring motion phenomena disappear, indicating that the structure of this peptide sequence can be stabilized by extrinsic factors. Interestingly, we observe NMR parameters (ROEs, (3)J coupling constants) for NH-12-5-2 in 90% v/v TFE that are consistent with the presence of a partial helical structure, similar to what was observed at low pH in our earlier CD experiments. We conclude that the NH-12-5-2 model polypeptide sequence possesses an inherent conformational instability that involves the D1-S5 sequence segment and the P6 residue but that this instability can be offset by extrinsic factors (e.g., charge neutralization, imido ring interconversion, and hydrophobic-hydrophobic interactions). These nonbonding interactions may play a role in the recognition and binding of this phage sequence region to SWNHs surfaces. 相似文献
3.
Dr. Masashi Hasegawa Dr. Ken‐ichi Nakamura Saki Tokunaga Yumi Baba Ryota Shiba Prof. Dr. Takashi Shirahata Prof. Dr. Yasuhiro Mazaki Prof. Dr. Yohji Misaki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(29):10090-10101
Understanding the details of the electronic structure in face‐to‐face arranged tetrathiafulvalenes (TTFs) is very important for the design of supramolecular functional materials and superior conductive organic materials. This article is a comprehensive study of the interactions among columnar stacked TTFs using trimeric (trimer) and tetrameric (tetramer) TTFs linked by alkylenedithio groups (‐S(CH2)nS‐, n=1–4) as models of triple‐ and quadruple‐decker TTF arrays. Single‐crystal X‐ray analyses of neutral trimeric TTFs revealed that the three TTF moieties are oriented in a zigzag arrangement. Cyclic voltammetry measurements (CV) reveal that the trimer and tetramer exhibited diverse reversible redox processes with multi‐electron transfers, depending on the length of the ‐S(CH2)nS‐ units and substituents. The electronic spectra of the radical cations, prepared by electrochemical oxidation, showed charge resonance (CR) bands in the NIR/IR region (1630–1850 nm), attributed to a mixed valence (MV) state of the triple‐ and quadruple‐decker TTF arrays. In the trimeric systems, the dicationic state (+2; 0.66 cation per TTF unit) was found to be a stable state, whereas the monocationic state (+1) was not observed in the electronic spectra. In the tetrameric system, substituent‐dependent redox processes were observed. Moreover, π‐trimers and π‐tetramers, which show a significant Davydov blueshift in the spectra, are formed in the tricationic (trimer) and tetracationic (tetramer) state. In addition, these attractive interactions are strongly dependent on the length of the linkage unit. 相似文献
4.
Kulp JL Minamisawa T Shiba K Tejani M Evans JS 《Langmuir : the ACS journal of surfaces and colloids》2007,23(7):3857-3863
Technological advances have facilitated the generation of artificial proteins that possess the capabilities of recognizing and binding to inorganic solids and/or controlling nucleation processes that form inorganic solids. However, very little is known regarding the structure of these interesting polypeptides and how their structure contributes to functionality. To address this deficiency, we report structural investigations of an artificial protein, p288, that self-assembles and controls the nucleation of simple salts and organic compounds into dendrite-like crystals. Under aqueous conditions at low pH and in the presence of high salt, p288 is conformationally labile and exists primarily as a random coil conformer in equilibrium with other undefined secondary structures, including polyproline type II and beta turn. We note that p288 can fold into either a partial beta strand (at neutral pH) or a predominantly alpha helical (in the presence of TFE) conformation. Solid-state 13C-15N NMR experiments also reveal that p288 in the lyophilized, hydrated state possesses some degree of nonrandom coil structure. These results indicate that p288 is conformationally labile but can undergo conformational transitions to a more stable structure when water solvent loss/displacement occurs and protein concentrations increase. We believe that conformational instability and the ability to adopt different structures as a function of different environmental conditions represent important molecular features that impact p288 supramolecular assembly and crystal nucleation processes. 相似文献
5.
M. Imoto S. Kusumoto T. Shiba E.Th. Rietschel C. Galanos O. Lüderitz 《Tetrahedron letters》1985,26(7):907-908
The chemical structure of E. coli lipid A was elucidated to be by determination of the nature of the individual acyl groups bound to the two hydroxyl groups in positions 3,3′ and the two amino groups of the D-glucosamine disaccharide phosphate backbone. 相似文献
6.
Tateaki Wakamiya Keiko Yamanoi Masahiro Nishikawa Tetsuo Shiba 《Tetrahedron letters》1985,26(39):4759-4760
Bulgecinine, a new proline type amino acid in bulgecins, was synthesized stereospecifically by use of D-glucose as a chiral precursor. 相似文献
7.
Partial degradation and biological activities of an antitumor polysaccharide from rice bran. 总被引:8,自引:0,他引:8
Y Tanigami S Kusumoto S Nagao S Kokeguchi K Kato S Kotani T Shiba 《Chemical & pharmaceutical bulletin》1991,39(7):1782-1787
A rice bran polysaccharide designated RON was subjected either to partial hydrolysis with formic acid or to partial degradation by ultrasonic irradiation. A significant change in the molecular size was also observed during simple chromatography of RON on a strongly acidic ion exchange resin, although the apparent molecular weight of RON had been assumed to be more than 1 x 10(6) daltons (Da). This fact indicates that RON exists as molecular aggregates, presumably mediated by metal cations. Degradation products with average molecular weights above ca. 1 x 10(4) Da which were obtained by any of the three methods still retained the following activities of RON: in vivo antitumor activity against Meth-A fibrosarcoma in mice by oral administration, and in vitro macrophage stimulatory effects to induce tumoricidal activity and interleukin 1 production. This molecular size was proven to be the minimum requisite for these activities because smaller fragments were scarcely active. The aggregation was characteristic of RON but not essential for its antitumor activity because definite, though slightly reduced, activity was exhibited even by the smaller fragments obtained after the ion exchange resin treatment. 相似文献
8.
T Kusama T Soga Y Ono E Kumazawa E Shioya Y Osada S Kusumoto T Shiba 《Chemical & pharmaceutical bulletin》1991,39(8):1994-1999
Two novel analogs of a biosynthetic precursor of lipid A (2) were synthesized. The one analog (3) has acyl groups identical to those of 2, and the other (4) has tetradecanoyl groups in place of the (R)-3-hydroxytetradecanoyl groups of 2. Both 3 and 4 possess an alpha-glycosidically-bound phosphonooxyethyl group in place of the alpha-glycosyl phosphate group of 2. Compounds 3 and 4 exhibited definite antitumor activity against Meth A fibrosarcoma and low toxicity in rabbits, as the original compound 2 does. The replacement of the hydroxytetradecanoyl groups with tetradecanoyl groups barely affected the antitumor activity, but slightly enhanced the toxicity in rabbits. 相似文献
9.
For an integer N greater than 5 and a triple \({\mathfrak{a}}=[a_{1},a_{2},a_{3}]\) of integers with the properties 0<a i ≤N/2 and a i ≠a j for i≠j, we consider a modular function \(W_{\mathfrak{a}}(\tau)=\frac{\wp (a_{1}/N;L_{\tau})-\wp (a_{3}/N;L_{\tau})}{\wp (a_{2}/N;L_{\tau})-\wp(a_{3}/N;L_{\tau})}\) for the modular group Γ 1(N), where ?(z;L τ ) is the Weierstrass ?-function relative to the lattice L τ generated by 1 and a complex number τ with positive imaginary part. For a pair of such triples \({\mathfrak{A}}=[{\mathfrak{a}},{\mathfrak{b}}]\) and a pair of non-negative integers F=[m,n], we define a modular function \(T_{{\mathfrak{A}},F}\) for the group Γ 0(N) as the trace of the product \(W_{\mathfrak{a}}^{m}W_{\mathfrak{b}}^{n}\) to the modular function field of Γ 0(N). In this article, we study the integrality of singular values of the functions \(W_{\mathfrak{a}}\) and \(T_{{\mathfrak{A}},F}\) by using their modular equations. We prove that the functions \(T_{{\mathfrak{A}},F}\) for suitably chosen \({\mathfrak{A}}\) and F generate the modular function field of Γ 0(N), and from Shimura reciprocity and Gee–Stevenhagen method we obtain that singular values \(T_{{\mathfrak{A}},F}(\tau)\) for suitably chosen \({\mathfrak{A}}\) and F generate ring class fields. Further, we study the class polynomial of \(T_{{\mathfrak{A}},F}\) for Schertz N-system. 相似文献
10.
A lithium isotope separation was performed using a laser isotope separation method. It was found that the lithium atoms with a natural isotopic abundance enhanced its6Li concentration up to over 90% by tuning the laser wavelength to the2
P
1/2 of6Li. Too high power, however, leads to a loss of enrichment due to the power broadening effect which was analysed by the equation of motion of density matrices. 相似文献