全文获取类型
收费全文 | 1044篇 |
免费 | 14篇 |
国内免费 | 5篇 |
专业分类
化学 | 744篇 |
晶体学 | 14篇 |
力学 | 10篇 |
数学 | 74篇 |
物理学 | 221篇 |
出版年
2023年 | 7篇 |
2021年 | 7篇 |
2020年 | 6篇 |
2019年 | 14篇 |
2018年 | 7篇 |
2017年 | 5篇 |
2016年 | 15篇 |
2015年 | 11篇 |
2014年 | 15篇 |
2013年 | 44篇 |
2012年 | 35篇 |
2011年 | 51篇 |
2010年 | 24篇 |
2009年 | 33篇 |
2008年 | 43篇 |
2007年 | 59篇 |
2006年 | 78篇 |
2005年 | 70篇 |
2004年 | 41篇 |
2003年 | 45篇 |
2002年 | 38篇 |
2001年 | 25篇 |
2000年 | 24篇 |
1999年 | 19篇 |
1998年 | 11篇 |
1997年 | 11篇 |
1996年 | 16篇 |
1995年 | 20篇 |
1994年 | 11篇 |
1993年 | 9篇 |
1992年 | 24篇 |
1991年 | 9篇 |
1990年 | 19篇 |
1989年 | 13篇 |
1988年 | 17篇 |
1987年 | 15篇 |
1986年 | 11篇 |
1985年 | 10篇 |
1984年 | 16篇 |
1982年 | 14篇 |
1981年 | 7篇 |
1979年 | 15篇 |
1978年 | 19篇 |
1977年 | 18篇 |
1976年 | 6篇 |
1975年 | 5篇 |
1974年 | 8篇 |
1973年 | 5篇 |
1970年 | 5篇 |
1967年 | 5篇 |
排序方式: 共有1063条查询结果,搜索用时 0 毫秒
51.
Daisuke Suzuki Tomoyo Yamagata Koji Horigome Kiyoshi Shibata Akira Tsuchida Tsuneo Okubo 《Colloid and polymer science》2012,290(2):107-117
Influence of the gel size on the morphology, phase diagram, and reflection spectroscopy of the colloidal crystals of thermo-sensitive
gel spheres, poly (N-isopropylacrylamide) (pNIPAm), was discussed by adding the data of two gel samples of pNIPAm(400–5) and pNIPAm(600–5) of
412 nm (at 25 °C) and 220 nm (at 45 °C) and of 517 nm (at 20 °C) and 294 nm (at 45 °C), respectively. Colloidal single crystals
formed, but not so large compared with the giant crystals of small pNIPAm gels reported previously. The suspensions even with
ion-exchange resins were turbid and hard to observe the single crystals clearly with the naked eyes as gel size increased.
The critical concentration of melting decreased sharply as the suspensions were deionized with coexistence of the mixtures
of cation- and anion-exchange resins. The critical concentration increased as the gel size increased and/or dispersion temperature
increased. Density of the gel spheres increased as their size increased. These results demonstrated that the colloidal crystallization
takes place by the extended electrical double layers formed around the gel spheres in addition of the excluded volume effect of the gels. Contribution of the electrical double layers on the crystallization increased sharply as temperature increased
and gel concentration decreased, respectively. The contribution also increased slightly as sphere size increased, when comparison
was made at the same gel concentration in wt.%. The present work clarified that the colloidal interfaces, which are inevitable
for the formation of the electrical double layers, are formed between the water phase and gel spheres, though the gel spheres
contain a lot of water molecules at the inner sphere region. 相似文献
52.
Murai K Nakamura A Matsushita T Shimura M Fujioka H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(27):8448-8453
A method for conducting enantioselective bromolactonization reactions of trisubstituted alkenoic acids, using the C(3)-symmetric trisimidazoline 1 and 1,3-dibromo-5,5-dimethyl hydantoin as a bromine source, has been developed. The process generates chiral δ-lactones that contain a quaternary carbon. The results of studies probing geometrically different olefins show that (Z)-olefins rather than (E)-olefins are favorable substrates for the process. The method is not only applicable to acyclic olefin reactants but can also be employed to transform cyclic trisubstituted olefins into chiral spirocyclic lactones. Finally, the synthetic utility of the newly developed process is demonstrated by its application to a concise synthesis of tanikolide, an antifungal marine natural product. 相似文献
53.
Akihisa?Kaneko Pankaj?Sehgal Hidekazu?DoeEmail author 《Colloid and polymer science》2012,290(4):323-330
The pH dependence of an anionic surfactant, sodium N-dodecanoylsarcosinate (SLAS), has been studied by measuring interfacial tension, fluorescence, dynamic light scattering,
etc., in aqueous solutions with phosphate and borate buffers. The interfacial tension (γ) of SLAS decreases remarkably with a pH decrease and is constant at pH > 7.3. The observed values for the critical micelle
concentration (cmc) and the surfactant concentration at which its γ value is reduced by 20 mN/m from that of pure water (C
20) decrease with a pH decrease, while those also become constant at pH > 6.5 and >7.3, respectively. On the other hand, the
interfacial excess of SLAS increases at pH < 7.3. These interfacial behaviors have been further investigated by the addition
of Tl+ which replaces Na+ of SLAS. The observed γ values of LAS− with the different counter cations are in the order of H+ < Tl+ < Na+. In order to reveal aggregation properties of SLAS, the aggregation number (N
agg), the micropolarity, the hydrodynamic radius (R
h) of micelle, and the fluorescence anisotropy of Rhodamine B (r) have been evaluated at various pHs. The N
agg value shows a decreasing tendency with a pH increase. The I
1/I
3 ratio and the R
h values do not strongly depend on pH. The r value decreases until pH 7 and remains constant at pH > 7.0. These interfacial and micelle properties have been discussed
in detail considering the electrostatic interaction and the molecular structures of the hydrophilic headgroup. 相似文献
54.
Takechi C Kawaguchi T Kaneko F Yamamuro O Akita H Ono M Suzuki M 《The journal of physical chemistry. B》2007,111(33):9706-9710
Dynamical properties of acyl chains in the three polymorphic phases alpha, beta', and beta of tristearin [C(3)H(5)(OCOC(17)H(35))3] have been studied by means of incoherent quasielastic neutron scattering (IQNS) using selectively deuterated samples. The mean square displacement of hydrogen atoms, , was estimated from the scattering vector Q dependence of the elastic scattering component under the harmonic approximation. It was shown that the temperature dependence of was significantly different between the three phases. There was no marked difference in between these phases up to 193 K, and the value increased linearly with temperature. Although the beta phase remained linear up to 293 K, the alpha and beta' phases started to show a nonlinear increase around 200 K, suggesting an anharmonic nature of molecular motions. The alpha phase exhibited the most conspicuous temperature dependence. These characteristics were ascribable to the difference in the lateral packing of acyl chains. Compared with the beta phase which has a tightly packed T// subcell, the beta' and alpha phases have looser O perpendicular and H subcells, respectively. The molecular motion in the alpha phase was analyzed using the model of uniaxial rotational diffusion in a onefold cosine potential. It has been clarified that the rotational fluctuation about the chain axis in the alpha phase is rather restricted compared with that in the rotator phase of n-alkanes. 相似文献
55.
Prof. Dr. Masaichi Saito Tomoki Akiba Misumi Kaneko Toshiaki Kawamura Dr. Minori Abe Prof. Dr. Masahiko Hada Prof. Dr. Mao Minoura 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(50):16946-16953
Plumbacyclopentadienylidenes, in which the lead atoms have divalent states and are coordinated by THF, pyridine and N‐heterocyclic carbene, were synthesized and characterized. The THF‐ and pyridine‐stabilized compounds can be regarded as rare examples of hypervalent 10‐X‐4 species. The equilibrium between the THF adduct and the free plumbacyclopentadienylidene was evidenced by spectroscopic analysis and theoretical calculations. The THF adduct in benzene converted into a plumbylene dimer, where one of the lead centers is coordinated by THF and the other lead atom is coordinated by a divalent lead atom, the dimer gradually decomposing into spiroplumbole. The THF adduct unexpectedly reacted with trifluoroborane and trichlorogallane to afford fluoroborole and chlorogallole, which are the first examples of non‐annulated fluoroborole and gallole, respectively. 相似文献
56.
F. Khoerunnisa D. Minami T. Fujimori S. Y. Hong Y. C. Choi H. Sakamoto M. Endo K. Kaneko 《Adsorption》2014,20(2-3):301-309
We tuned the electronic properties of single wall carbon nanotube (SWCNT) with intercalation of naphthalene derivatives (NDs) having different electron donor or acceptor property in the SWCNT bundles. Characterization of the adsorbed SWCNT with Raman spectroscopy and electrical conductivity measurement clearly indicate the charge transfer interaction of ND molecules with SWCNT. Also X-ray diffraction supports the intercalation of ND molecules in the interstitial spaces and groove sites of SWCNT bundle. Intercalation of ND molecules enhances remarkably the CO2 adsorptivity, which can be ascribed to the key importance of the interaction of the quadrupole moment of CO2 with the local electrical field on the SWCNT induced by the charge transfer interaction. 相似文献
57.
Tomoyuki Miyao Hiromasa Kaneko Kimito Funatsu 《Journal of computer-aided molecular design》2016,30(5):425-446
Generating chemical graphs in silico by combining building blocks is important and fundamental in virtual combinatorial chemistry. A premise in this area is that generated structures should be irredundant as well as exhaustive. In this study, we develop structure generation algorithms regarding combining ring systems as well as atom fragments. The proposed algorithms consist of three parts. First, chemical structures are generated through a canonical construction path. During structure generation, ring systems can be treated as reduced graphs having fewer vertices than those in the original ones. Second, diversified structures are generated by a simple rule-based generation algorithm. Third, the number of structures to be generated can be estimated with adequate accuracy without actual exhaustive generation. The proposed algorithms were implemented in structure generator Molgilla. As a practical application, Molgilla generated chemical structures mimicking rosiglitazone in terms of a two dimensional pharmacophore pattern. The strength of the algorithms lies in simplicity and flexibility. Therefore, they may be applied to various computer programs regarding structure generation by combining building blocks. 相似文献
58.
Xiao Zhao Shinobu Takao Takuma Kaneko Yasuhiro Iwasawa 《Chemical record (New York, N.Y.)》2019,19(7):1337-1353
It remains a big challenge to remarkably improve both oxygen reduction reaction (ORR) activity and long‐term durability of Pt?M bimetal electrocatalysts simultaneously in the harsh cathode environment toward widespread commercialization of polymer electrolyte fuel cells (PEFC). In this account we found double‐promotional effects of carbon micro coil (CMC) support on ORR performance and durability of octahedral Pt3Ni nanoparticles (Oh Pt3Ni/CMC). The Oh Pt3Ni/CMC displayed remarkable improvements of mass activity (MA; 13.6 and 34.1 times) and surface specific activity (SA; 31.3 and 37.0 times) compared to those of benchmark Pt/C (TEC10E20E) and Pt/C (TEC10E50E‐HT), respectively. Notably, the Oh Pt3Ni/CMC revealed a negligible MA loss after 50,000 triangular‐wave 1.0–1.5 VRHE (startup/shutdown) load cycles, contrasted to MA losses of 40 % (TEC10E20E) and 21.5 % (TEC10E50E‐HT) by only 10,000 load cycles. It was also found that the SA increased exponentially with the decrease in the CO stripping peak potential in a series of Pt?M/carbon (M: Ni and Co), which predicts a maximum SA at the curve asymptote. Key factors for simultaneous improvements of performance and durability of core‐shell Pt3Ni/carbon electrocatalysts toward superior PEFC is also discussed. 相似文献
59.
Two-dimensional network formation of cardiac myocytes in agar microculture chip with 1480 nm infrared laser photo-thermal etching 总被引:1,自引:0,他引:1
We have developed a new method that enables agar microstructures to be used to cultivate cells and that allows cell network patterns to be controlled. The method makes use of non-contact three-dimensional photo-thermal etching with a 1480 nm infrared focused laser beam, which is strongly absorbed by water and agar gel, to form the shapes of agar microstructures. It allows microstructures to be easily formed in an agar layer within a few minutes, with cell-culture holes formed by the spot heating of a 100 mW laser and tunnels by the tracing of a 100 microm s(-1), 40 mW laser. We cultivated rat cardiac myocytes in adjacent microstructures and observed synchronized beating in them 90 min after they had made physical contact. Our results indicate that the system can make and use microstructures for cell-network cultivation in a minimal amount of time without any expensive microfabrication facilities or complicated procedures. 相似文献
60.
Monolayer properties of irisresorcinol [5-(cis-10-heptadecenyl) resorcinol] were measured at the air/water interface. TheA-T isobars of the monolayers at 10 and 15 mN/m gave two-dimensional thermal expansivities of 1.4 × 10–4/K and 1.3 × 10–4/K at a temperature span from 7–40 C, respectively. The- A isotherms of the material showed only a little dependence on temperature from 5–35 C and onpH except at highpH, where monolayers expanded by ionization of resorcinol headgroups. Some types of saccharose in the subphase exhibited a characteristic interaction with irisresorcinol in monolayers, and there is a possibility that this material will be used for molecular recognition of some saccharoses. 相似文献