全文获取类型
收费全文 | 2697篇 |
免费 | 95篇 |
国内免费 | 5篇 |
专业分类
化学 | 2103篇 |
晶体学 | 26篇 |
力学 | 34篇 |
综合类 | 1篇 |
数学 | 102篇 |
物理学 | 531篇 |
出版年
2023年 | 16篇 |
2022年 | 17篇 |
2021年 | 28篇 |
2020年 | 34篇 |
2019年 | 56篇 |
2018年 | 33篇 |
2017年 | 20篇 |
2016年 | 53篇 |
2015年 | 60篇 |
2014年 | 58篇 |
2013年 | 129篇 |
2012年 | 168篇 |
2011年 | 182篇 |
2010年 | 85篇 |
2009年 | 81篇 |
2008年 | 148篇 |
2007年 | 158篇 |
2006年 | 166篇 |
2005年 | 124篇 |
2004年 | 116篇 |
2003年 | 114篇 |
2002年 | 117篇 |
2001年 | 64篇 |
2000年 | 57篇 |
1999年 | 32篇 |
1998年 | 21篇 |
1996年 | 24篇 |
1995年 | 15篇 |
1994年 | 30篇 |
1993年 | 26篇 |
1992年 | 26篇 |
1991年 | 27篇 |
1990年 | 26篇 |
1989年 | 19篇 |
1988年 | 25篇 |
1987年 | 33篇 |
1986年 | 22篇 |
1985年 | 40篇 |
1984年 | 29篇 |
1983年 | 15篇 |
1982年 | 20篇 |
1981年 | 16篇 |
1980年 | 18篇 |
1979年 | 26篇 |
1978年 | 28篇 |
1977年 | 22篇 |
1976年 | 20篇 |
1975年 | 27篇 |
1974年 | 25篇 |
1973年 | 21篇 |
排序方式: 共有2797条查询结果,搜索用时 31 毫秒
991.
Shoichi Okouchi Pariya Thanatuksorn Shiego Ikeda Hisashi Uedaira 《Journal of solution chemistry》2011,40(5):775-785
The 17O-NMR spin-lattice relaxation times (T
1) of water molecules in aqueous solutions of n-alkylsulfonate (C1 to C6) and arylsulfonic anions were determined as a function of concentration at 298 K. Values of the dynamic hydration number,
(S-) = nh - (tc- /tc0 - 1)(\mathrm{S}^{-}) = n_{\mathrm{h}}^{ -} (\tau_{\mathrm{c}}^{-} /\tau_{\mathrm{c}}^{0} - 1), were determined from the concentration dependence of T
1. The ratios (tc -/tc0\tau_{\mathrm{c}}^{ -}/\tau_{\mathrm{c}}^{0}) of the rotational correlation times (tc -\tau_{\mathrm{c}}^{ -} ) of the water molecules around each sulfonate anion in the aqueous solutions to the rotational correlation time of pure water
(tc0\tau_{\mathrm{c}}^{0}) were obtained from the n
DHN(S−) and the hydration number (nh -n_{\mathrm{h}}^{ -} ) results, which was calculated from the water accessible surface area (ASA) of the solute molecule. The tc -/tc0\tau_{\mathrm{c}}^{ -}/\tau_{\mathrm{c}}^{0} values for alkylsulfonate anions increase with increasing ASA in the homologous-series range of C1 to C4, but then become approximately constant. This result shows that the water structures of hydrophobic hydration near large
size alkyl groups are less ordered. The rotational motions of water molecules around an aromatic group are faster than those
around an n-alkyl group with the same ASA. That is, the number of water–water hydrogen bonds in the hydration water of aromatic groups
is smaller in comparison with the hydration water of an n-alkyl group having the same ASA. Hydrophobic hydration is strongly disturbed by a sulfonate group, which acts as a water
structure breaker. The disturbance effect decreases in the following order: $\mbox{--} \mathrm{SO}_{3}^{-} > \mbox{--} \mathrm{NH}_{3}^{ +} > \mathrm{OH}> \mathrm{NH}_{2}$\mbox{--} \mathrm{SO}_{3}^{-} > \mbox{--} \mathrm{NH}_{3}^{ +} > \mathrm{OH}> \mathrm{NH}_{2}. The partial molar volumes and viscosity B
V
coefficients for alkylsulfonate anions are linearly dependent on their n
DHN(S−) values. 相似文献
992.
Masaaki Kobata Igor Píš Hiroshi Nohira Hideo Iwai Keisuke Kobayashi 《Surface and interface analysis : SIA》2011,43(13):1632-1635
A laboratory hard X‐ray photoelectron spectroscopy (HXPS) system at 5.4‐keV excitation energy was used to measure the angle dependence of a silicon oxide overlayer on a Si(0 0 1) substrate with overlayer thickness ranging from 4 to 25 nm. The thickness values of the SiO2 overlayers were determined by utilizing a focused monochromatized Cr Kα source and a high‐energy hemispherical analyzer with an angle‐resolved wide acceptance angle objective lens. The modulation of the photoemission intensity due to photoelectron diffraction, which deteriorates high‐precision thickness determination, was suppressed significantly by continuous sample rotation around the sample's normal during the measurements. The resultant thickness values very well agree with those determined by ellipsometry in the same sample set. To demonstrate merits of the large information depth measurements, profiling of a wedged SiO2 layer buried in a gate stack model structure with Ir (8 nm) and HfO2 (2 nm) overlayers was performed. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
993.
994.
Lee SM Ikeda S Yagi T Harada T Ennaoui A Matsumura M 《Physical chemistry chemical physics : PCCP》2011,13(14):6662-6669
Polycrystalline CuInS(2) films were fabricated by sulfurization of electrodeposited Cu and In metallic precursor films in a Cu-rich composition at 520 °C in H(2)S (5% in Ar). Structural analyses revealed that the adherence of the thus-formed CuInS(2) film to the Mo substrate was strongly dependent on heating profiles of the Cu/In bilayer film: a CuInS(2) film with poor adherence having many crevices was formed when the Cu/In bilayer film was heated monotonously from room temperature to 520 °C in Ar within 25 min followed by sulfurization, whereas CuInS(2) films with good adherence were obtained when the Cu/In films were pretreated at 110 °C in Ar for 10-60 min just before increasing the temperature up to 520 °C for sulfurization. It was also clarified that the CuInS(2) film obtained without 110 °C pretreatment had pinholes inside the film, whereas the CuInS(2) films formed after 110 °C pretreatment showed no notable pinholes. Photoelectrochemical responses of these CuInS(2) films in an electrolyte solution containing Eu(III) indicated that the CuInS(2) films obtained after 110 °C pretreatment had higher external quantum efficiency (EQE) values than those of films obtained without 110 °C pretreatment, mainly due to better adherence of 110 °C pretreated CuInS(2) films to the Mo substrate than the CuInS(2) film obtained without 110 °C pretreatment. The performance of solar cells with an Al:ZnO/Zn(S,O)/CdS/CuInS(2)/Mo structure also depended on the structural characteristics of the CuInS(2) films, i.e., preliminary conversion efficiencies of ca. 5% were obtained for devices based on the CuInS(2) films obtained after 110 °C pretreatment, whereas the device prepared by the CuInS(2) film without 110 °C pretreatment showed the conversion efficiency less than 1.5%. 相似文献
995.
Ogoshi T Demachi K Kitajima K Yamagishi TA 《Chemical communications (Cambridge, England)》2011,47(37):10290-10292
A pillar[5]arene dimer was synthesized by linking a mono-hydroxylated pillar[5]arene with 1,4-bis(bromomethyl)benzene. The pillar[5]arene dimer formed stronger complexes with n-alkanes than did a monomeric pillar[5]arene. 相似文献
996.
Alkenyl alkynyl ketones and ketene silyl acetals (KSAs) undergo regioselective [2+2]-cycloaddition under thermal conditions, triggering domino pericyclic reactions en route to various poly-substituted salicylic acid derivatives. 相似文献
997.
Ishii N Mamiya J Ikeda T Winnik FM 《Chemical communications (Cambridge, England)》2011,47(4):1267-1269
Irradiation at room temperature of α,ω-di-[4-cyanophenyl-4'-(6-hexyloxy)-azobenzene]-poly-(N-isopropylacrylamide) (Az(2)-PNIPAM) solutions in water/1,4-dioxane (6 mol% dioxane) reversibly converts a turbid suspension into a clear solution, demonstrating for the first time that cononsolvency of PNIPAM in mixed aqueous solvents in synergy with preferential chromophore solvation can act as actuators of responsive systems. 相似文献
998.
999.
Noji T Kamidaki C Kawakami K Shen JR Kajino T Fukushima Y Sekitoh T Itoh S 《Langmuir : the ACS journal of surfaces and colloids》2011,27(2):705-713
An oxygen-evolving photosynthetic reaction center complex (PSII) was adsorbed into nanopores in SBA, a mesoporous silica compound. We purified the dimer of PSII complex from a thermophilic cyanobacterium, Thermosynechococcus vulcanus, which grows optimally at 57 °C. The thermally stable PSII dimeric complex has a diameter of 20 nm and a molecular mass of 756 kDa and binds more than 60 chlorophylls. The SBA particles, with average internal pore diameters of 15 nm (SBA(15)) and 23 nm (SBA(23)), adsorbed 4.7 and 15 mg of PSII/g SBA, respectively. Measurement with a confocal laser-scanning microscope indicated the adsorption of PSII to the surface and the inner space of the SBA(23) particles, indicating the adsorption of PSII into the 23 nm silica nanopores. PSII did not bind to the inner pores of SBA(15). PSII bound to SBA(23) showed the high and stable activity of a photosynthetic oxygen-evolving reaction, indicating the light-driven electron transport from water to the quinone molecules added in the outer medium. The PSII-SBA conjugate can be a new material for photosensors and artificial photosynthetic systems. 相似文献
1000.
Yamaguchi M Ikeda K Suzuki M Kiyohara A Kudoh SN Shimizu K Taira T Ito D Uchida T Gohara K 《Langmuir : the ACS journal of surfaces and colloids》2011,27(20):12521-12532
Micropatterning techniques have become increasingly important in cellular biology. Cell patterning is achieved by various methods. Photolithography is one of the most popular methods, and several light sources (e.g., excimer lasers and mercury lamps) are used for that purpose. Vacuum ultraviolet (VUV) light that can be produced by an excimer lamp is advantageous for fabricating material patterns, since it can decompose organic materials directly and efficiently without photoresist or photosensitive materials. Despite the advantages, applications of VUV light to pattern biological materials are few. We have investigated cell patterning by using a template of a microstructured organosilane layer fabricated by VUV lithography. We first made a template of a microstructured organosilane layer by VUV lithography. Cell adhesive materials (poly(d-lysine) and polyethyleneimine) were chemically immobilized on the organosilane template, producing a cell adhesive material pattern. Primary rat cardiac and neuronal cells were successfully patterned by culturing them on the pattern substrate. Long-term culturing was attained for up to two weeks for cardiac cells and two months for cortex cells. We have discussed the reproducibility of cell patterning and made suggestions to improve it. 相似文献