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101.
Synthesis of a highly luminescent three-dimensional pyrene dye based on the spirobifluorene skeleton
We have synthesized a highly luminescent (log e > 5.0, F > 0.9) pyrene dye based on a spirobifluorene skeleton [2,2',7,7'-tetrakis(7-tert-butyl-1-pyrenyl)-9,9'-spirobi[9H-fluorene; 4-PySBF]. The use of spirobifluorene prevents fluorescence quenching by intramolecular energy transfer and/or electron transfer among the chromophores in the excited state. The emission spectra of 4-PySBF exhibited a red shift of 20 nm in comparison to a model compound [9,9'-dioctyl-2,7-bis(7-tert-butyl-1-pyrenyl)-9H-fluorene; 2-PyF], but its UV-Vis spectrum remained unchanged. 相似文献
102.
A 1,3,5-substituted benzene platform has been widely used in the fields of supramolecular chemistry and molecular recognition. Here, we show that 1,3,5-tris(2-benzyl-o-carboran-1-yl)benzene 6 exhibits solvent-dependent conformation in the crystalline state. Recrystallization from dichloromethane-n-pentane gave the anti conformation 6-anti, while recrystallization from methanol-acetone gave the syn conformation 6-syn, in which the three benzyl-o-carboranyl moieties are located to one side of the central benzene ring. Interestingly, one acetone molecule is captured in the π-rich space of 6-syn and two complexes facing each other encapsulate two acetone molecules in a π-rich container formed by the eight benzene rings. The inclusion involves several weak interactions, that is, T-shaped C-H···π interactions, and C-H···O and C-H···π interactions. Two C-H···O interactions involving benzylic C-H hydrogens activated by the electron-withdrawing character of the o-carborane cage and the oxygen atom of the acetone seem to be the most important. DFT calculations indicate that the binding energy for entrapment of acetone is 6.6 kcal/mol. Inclusion of acetone is achieved through not only multiple C-H···O interactions but also a number of C-H···π interactions. The third benzyl-o-carborane moiety is fixed in the syn conformation by intramolecular and intermolecular C-H···π interactions. 相似文献
103.
This study examined the relationship between the functions of plant cells and the characteristics of cellulose microfibril
aggregates in the cell walls. For this purpose, the mature bamboo (Phyllostachys pubescens) culm was separated into fiber and parenchyma cells, and then the morphological and physical properties of the cellulose
microfibril aggregates isolated from both cells were compared. SEM observations revealed that both fiber and parenchyma cells
consist of similar microfibril aggregates approximately 15–20 nm in width. Moreover, X-ray analysis and the tensile tests
of the sheets prepared from the microfibril aggregates showed that the cellulose microfibrils isolated from fiber and parenchyma
cells had almost the same cellulose crystallinity and longitudinal Young’s modulus in the dry state. These results suggest
that all the cellulose microfibrils synthesized in the same individual exhibit the same characteristics in the dry state regardless
of cell function. 相似文献
104.
Bending tests and X-ray diffraction studies were conducted on oven-dried wood samples (Picea jezoensis Carr.) treated with various concentrations of aqueous NaOH solution to investigate the influence of alkali treatment on the
longitudinal contraction, bending properties, and cellulose structure. The length of the wood samples decreased and the density
increased at NaOH concentrations greater than 10%. The Young’s modulus and the specific Young’s modulus decreased and the
strain at yield increased for the same concentration range. However, the stress at yield was almost constant for all concentration
ranges. X-ray diffraction analysis showed that lattice transformation from cellulose I to cellulose II did not occur during
alkali treatment and the crystallinity index decreased at NaOH concentrations greater than 10%. The crystallinity index was
linearly correlated with the changes in longitudinal contraction and the bending properties, which indicates that the increase
in the proportion of amorphous components of the cellulose influences the longitudinal contraction and the bending properties
of wood samples during alkali treatment. 相似文献
105.
A convenient synthesis of chiral 3,3′-disubstituted 1,1′-binaphthyl-2,2′-disulfonic acids (BINSA, 1) was developed. The key was directed ortho-lithiation of BINSA methyl ester 2 with n-BuLi and subsequent reaction with an electrophile. Electrophiles such as Br2, I2, Me3SiOTf, and i-PrOB(Pin) reacted smoothly with 3,3′-dilithiated BINSA methyl ester, and the corresponding 3,3′-dihalo-, 3,3′-bis(trimethylsilyl)-, and 3,3′-diboryl-BINSA derivatives were obtained in yields of 21–78%. This simple synthetic method is highly attractive since the ability to prepare 3,3′-disubstituted BINOLs in advance can be useful. 相似文献
106.
Tomonari Tanaka Masato Noguchi Masaki Ishihara Atsushi Kobayashi Shin-ichiro Shoda 《Macromolecular Symposia》2010,297(1):200-209
Summary: A cellotetraose-backboned hepta-saccharide (XXXG) (a capital X represents a glucopyranose residue that is substituted with a xylopyranose through an α-1,6 glycosidic bond, and a capital G represents a non-substituted glucopyranose residue) and a nona-saccharide (XLLG) (a capital L represents a glucopyranose residue that is substituted with a galactopyranoseβ(1-2)xylopyranose through an α-1,6 glycosidic bond) have directly been converted to the corresponding 4,6-dimethoxy-1,3,5-triazin-2-yl derivatives (DMT-β-XXXG 1 and DMT-β-XLLG 2 , respectively) by the action of 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methyl morpholinium chloride (DMT-MM). The selective nucleophilic attack of the anomeric hydroxyl group to DMT-MM has been achieved in water without using any protection of the hydroxyl groups. The resulting activated oligosaccharide derivatives ( 1 and 2 ) were found to polymerize catalyzed by an endo-β-1,4-glucanase as catalyst. The polymerization took place in a complete regio- and stereo-selective manner, affording non-natural polysaccharides having a XXXG-repeating unit and a XLLG-repeating unit, respectively, in the main chain. It is extremely difficult to construct such definite repeating structures via the conventional synthetic routes including protection-deprotection procedures. 相似文献
107.
Mitsuru Suda Takuya Hagihara Noriyoshi Suya Tsuyoshi Hamano Masashi Takada Teruaki Konishi Takeshi Maeda Yasushi Ohmachi Shizuko Kakinuma Kentaro Ariyoshi Yoshiya Shimada Hitoshi Imaseki 《Radiation Physics and Chemistry》2009,78(12):1216-1219
We developed a neutron irradiation facility, neutron exposure accelerator system for biological effect experiments (NASBEE) for biological studies in National Institute of Radiological Sciences, Japan. Irradiation field of 2 MeV average neutrons generated by a Be(d–n)B reaction is established. Dose uniformity of 240 mm in diameter irradiation field is producible within ±2.5% with a dose rate of 0.87 Gy/h at sample target distance of 1170 mm. Two irradiation rooms, a specific pathogen-free (SPF) conditioned one and a conventional, are now available. Irradiation protocols for in vitro experiments are now established and demonstrated by obtaining a relative biological effectiveness (RBE) of cell inactivation measured to be 3.54 with 10% survival dose (D10). 相似文献
108.
Shitao Wang Dr. Tomohisa Sawada Dr. Kazuaki Ohara Prof. Dr. Kentaro Yamaguchi Prof. Dr. Makoto Fujita 《Angewandte Chemie (International ed. in English)》2016,55(6):2063-2066
Guest‐induced M18L6–M24L8 capsule–capsule conversion is reported. Both capsules are composed of PdII ethylenediamine units (M) and 1,3,5‐tris(3,5‐pyrimidyl)pyrimidine (L), and form trigonal bipyramidal (M18L6) and octahedral (M24L8) closed‐shell structures with huge hydrophobic inner spaces. The M18L6 trigonal bipyramid is converted to the M24L8 octahedron through encapsulation of large aromatic guests, with the latter capsule possessing a cavity volume three times larger than the former. Despite the dynamic properties of the capsule host, the encapsulated guests are difficult to extract and are thus isolated from the external environment. 相似文献
109.
Application to Photocatalytic H2 Production of a Whole‐Cell Reaction by Recombinant Escherichia coli Cells Expressing [FeFe]‐Hydrogenase and Maturases Genes 下载免费PDF全文
Dr. Yuki Honda Prof. Hidehisa Hagiwara Prof. Shintaro Ida Prof. Tatsumi Ishihara 《Angewandte Chemie (International ed. in English)》2016,55(28):8045-8048
A photocatalytic H2 production system using an inorganic–bio hybrid photocatalyst could contribute to the efficient utilization of solar energy, but would require the development of a new approach for preparing a H2‐forming biocatalyst. In the present study, we constructed a recombinant strain of Escherichia coli expressing the genes encoding the [FeFe]‐hydrogenase and relevant maturases from Clostridium acetobutylicum NBRC 13948 for use as a biocatalyst. We investigated the direct application of a whole‐cell of the recombinant E. coli. The combination of TiO2, methylviologen, and the recombinant E. coli formed H2 under light irradiation, demonstrating that whole cells of the recombinant E. coli could be employed for photocatalytic H2 production without any time‐consuming and costly manipulations (for example, enzyme purification). This is the first report of the direct application of a whole‐cell reaction of recombinant E. coli to photocatalytic H2 production. 相似文献
110.
Highly Efficient Access to Both Geometric Isomers of Silyl Enol Ethers: Sequential 1,2‐Brook/Wittig Reactions 下载免费PDF全文
Prof. Dr. Yuji Matsuya Kentaro Wada Dr. Daishiro Minato Dr. Kenji Sugimoto 《Angewandte Chemie (International ed. in English)》2016,55(34):10079-10082
Novel sequential 1,2‐Brook/Wittig reactions were developed for the preparation of silyl enol ethers. This method enables highly selective preparation of both geometric isomers of glyoxylate silyl enol ethers, using aldehydes (E‐selective) and tosylimines (Z‐selective) as a Wittig electrophile. The salt‐free conditions of this reaction system are likely to be advantageous for switching the selectivity. The optimal reaction conditions and generality of the reaction were investigated, and plausible explanations for the observed selectivity were also discussed. 相似文献