全文获取类型
收费全文 | 2311篇 |
免费 | 127篇 |
国内免费 | 3篇 |
专业分类
化学 | 1706篇 |
晶体学 | 11篇 |
力学 | 44篇 |
数学 | 185篇 |
物理学 | 495篇 |
出版年
2024年 | 8篇 |
2023年 | 20篇 |
2022年 | 50篇 |
2021年 | 98篇 |
2020年 | 79篇 |
2019年 | 111篇 |
2018年 | 109篇 |
2017年 | 83篇 |
2016年 | 111篇 |
2015年 | 98篇 |
2014年 | 103篇 |
2013年 | 125篇 |
2012年 | 186篇 |
2011年 | 195篇 |
2010年 | 126篇 |
2009年 | 74篇 |
2008年 | 128篇 |
2007年 | 139篇 |
2006年 | 143篇 |
2005年 | 123篇 |
2004年 | 95篇 |
2003年 | 58篇 |
2002年 | 56篇 |
2001年 | 19篇 |
2000年 | 10篇 |
1999年 | 9篇 |
1998年 | 11篇 |
1997年 | 9篇 |
1996年 | 14篇 |
1995年 | 2篇 |
1994年 | 11篇 |
1993年 | 8篇 |
1992年 | 7篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 4篇 |
1983年 | 1篇 |
1981年 | 2篇 |
1977年 | 2篇 |
1976年 | 1篇 |
排序方式: 共有2441条查询结果,搜索用时 31 毫秒
991.
992.
Jussi Isokuortti Kim Kuntze Matti Virkki Zafar Ahmed Elina Vuorimaa-Laukkanen Mikhail A. Filatov Andrey Turshatov Timo Laaksonen Arri Priimagi Nikita A. Durandin 《Chemical science》2021,12(21):7504
Developing azobenzene photoswitches capable of selective and efficient photoisomerization by long-wavelength excitation is an enduring challenge. Herein, rapid isomerization from the Z- to E-state of two ortho-functionalized bistable azobenzenes with near-unity photoconversion efficiency was driven by triplet energy transfer upon red and near-infrared (up to 770 nm) excitation of porphyrin photosensitizers in catalytic micromolar concentrations. We show that the process of triplet-sensitized isomerization is efficient even when the sensitizer triplet energy is substantially lower (>200 meV) than that of the azobenzene used. This makes the approach applicable for a wide variety of sensitizer-azobenzene combinations and enables the expansion of excitation wavelengths into the near-infrared spectral range. Therefore, indirect excitation via endothermic triplet energy transfer provides efficient and precise means for photoswitching upon 770 nm near-infared light illumination with no chemical modification of the azobenzene chromophore, a desirable feature in photocontrollable biomaterials.Triplet energy transfer enables efficient Z-to-E photoswitching of azobenzenes even with near-infrared light. Ultrafast intersystem crossing of azobenzene makes the process entropy-driven and enables the use of endothermic sensitizer-azobenzene pairs. 相似文献
993.
Shiryayev A Pagan DL Gunton JD Rhen DS Saxena A Lookman T 《The Journal of chemical physics》2005,122(23):234911
The properties of the solvent affect the behavior of the solution. We propose a model that accounts for the contribution of the solvent free energy to the free energy of globular proteins in solution. For the case of an attractive square-well potential, we obtain an exact mapping of the phase diagram of this model without solvent to the model that includes the solute-solvent contribution. In particular we find for appropriate choices of parameters upper critical points, lower critical points, and even closed loops with both upper and lower critical points similar to those found before [Macromolecules 36, 5843 (2003)]. In the general case of systems whose interactions are not attractive square wells, this mapping procedure can be a first approximation to understand the phase diagram in the presence of solvent. We also present simulation results for both the square-well model and a modified Lennard-Jones model. 相似文献
994.
Natalya V. Shvedene Inna A. Nazarova Andrey A. Formanovsky Denis S. Otkidach Igor V. Pletnev 《Electrochemistry communications》2002,4(12):767
Ionophoric, extraction, acidic and hydrophobic properties of 3-(4-tolylazo)phenylboronic acid (TAPBA) were studied. Determined Kd value equals to 36±2, pKa equals to 8.6±0.5. TAPBA extracts dobutamine from water into chloroform and transports it across a bulk chloroform membrane. The recovery is 83% (pH=7.5), the transport rate – (6.5±0.5)×10−7 mol/h. 1H and 13C NMR data confirm the formation of an 1:1 complex between arylboronic acid and catecholamine. TAPBA was used as electrode-active component of plasticized membrane electrodes with cationic and anionic responses to catecholamines and phenolic acids, respectively. For the diethyl sebacate-plasticized membrane, a slope of electrode function to dobutamine is 56±2 mV/decade; the detection limit is 1.3×10−5 mol/l; the linear range – 5×10−5–1×10−2 mol/l; the working pH-range – 4.8–7.6; the response time – 5–10 s. ISE gives incomplete cationic function to less lipophilic catecholamines. The membrane with cationic additive shows an anionic response to caffeic acid in wide pH range. 相似文献
995.
Natalie Smirnova Anna Eremenko Vladimir Gayvoronskij Irina Petrik Yuriy Gnatyuk Galina Krylova Andrey Korchev Alexej Chuiko 《Journal of Sol-Gel Science and Technology》2004,32(1-3):357-362
Titania and silica-based porous coatings have been produced via sol–gel route in the presence of pore-creating agents PEG and viscous solvent -terpineol, or template agents CTAB, as well as triblock copolimer Pluronic P123. Porous titania films were characterised by HR TEM, UV-Vis, XRD, ellipsometry, ARS methods. The dispersion of the refractive index, the porosity (32–39%) and the thickness of the samples were estimated by integrating sphere transmission and reflection spectra with 3D angular resolved light scattering. The catalytic activity of mesoporous TiO2 and TiO2/ZrO2 as well as SiO2-benzophenone films in the process of CrVI to CrIII and Ag+ to Ag0 photoreduction have been studied. 相似文献
996.
997.
Lee J Kovalevsky AY Novozhilova IV Bagley KA Coppens P Richter-Addo GB 《Journal of the American Chemical Society》2004,126(23):7180-7181
Density Functional theoretical calculations confirm the experimental observation that the low-temperature photolysis of (TPP)Fe(NO)(NO2) (as a KBr pellet) results in the generation of linkage isomers involving the axial NO and NO2 groups and suggest the possible formation of the double linkage isomer (TPP)Fe(ON)(ONO). The energy difference between the ground state (porphine)Fe(NO)(NO2) and the double-linkage isomer (porphine)Fe(ON)(ONO) is 1.57 eV, which is comparable to the 1.59 eV calculated previously for the nitrosyl-to-isonitrosyl linkage isomerism in the five-coordinate (porphine)Fe(NO) analogue. 相似文献
998.
Enno LorkRüdiger Mews Makhmut M. ShakirovPaul G. Watson Andrey V. Zibarev 《Journal of fluorine chemistry》2002,115(2):165-168
The first AlkNSNHetF sulfur diimide 6 (Alk=adamant-1-yl, HetF=2,3,5,6-tetrafluoropyrid-4-yl) was prepared by trapping of the corresponding alkylthiazylamide [AlkNSN]−3 with pentafluoropyridine, followed by X-ray structural characterization. For 6, the Z,E configuration was found. From the reaction of 3 with octafluoronaphthalene, hexafluorinated naphthothiadiazole 7 was isolated along with the parent AlkNH2. 相似文献
999.
Fokin AA Schreiner PR Kozhushkov SI Sattelmeyer KW Schaefer HF De Meijere A 《Organic letters》2003,5(5):697-700
Highly symmetric aliphatic hydrocarbons such as D(4h)-[4]rotane do not necessarily have degenerate HOMOs. According to our predictions based on high-level computations, its radical cation should display a highly delocalized D(4h)-symmetric structure, in contrast to its Jahn-Teller distorted cousin, the radical cation of [3]rotane, which exists in two distonic localized forms with C(2v) and C(s) symmetry. 相似文献
1000.
Irina Nikolaevna Topchieva Vasily Vladimirovich Spiridonov Nadezhda Anatol’evna Kataeva Sergey Pavlovich Gubin Sergey Konstantinovich Filippov Andrey Vladimirovich Lezov 《Colloid and polymer science》2006,284(7):795-801
Stabilization of metallic nanoparticles may be achieved by the formation of their adducts with polymers and/or nanotubes of various chemical composition. Here, water-soluble nanotubes based on β-cyclodextrin (β-tubes) were used for entrapping of Fe nanoparticles obtained by the reduction of iron-containing precursors ([Fe3(CO)11H][Et4N] cluster and FeSO4). Using methods of light-scattering, viscometry, and isothermal diffusion measurements, it was shown that the adducts are associated in aqueous solutions. The presence of iron nanoparticles and the shape and size of adducts were verified by transmission electron microscopy. The adducts are long (up to 600 nm and longer), translucent associates consisting of denser walls and transparent cores. The width of nanotubes is ∼150 nm and the thickness of the wall 3–25 nm. Their magnetic properties were demonstrated by electron paramagnetic resonance method. The mechanism of self-assembly of the adducts is discussed. 相似文献