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排序方式: 共有449条查询结果,搜索用时 562 毫秒
101.
Sadahito Hashidate Yukio Nagasaki Masao Kato Hiro Matsuda Hachiro Nakanishi 《先进技术聚合物》1995,6(9):626-631
Photocrosslinkable second-order nonlinear optical (NLO) polymers were synthesized from cationic copolymerization of a vinyl ether monomer bearing 4′-nitrobiphenyl-4-oxy group as the NLO chromophore with a vinyl ether monomer bearing cinnamoyl group as the photoreactive moiety. To obtain a suitable poling method involving photocrosslinking, which is capable of inducing a higher and more stable second-order nonlinear coefficient, d33, for NLO polymer films, some poling procedures were investigated. An optimized poling method was as follows. Ultraviolet (UV) irradiation is performed for 90 sec during poling at 50°C for 20 min, followed by poling at 150°C for 20 min. By using this poling method NLO polymer films exhibited a higher and considerably stable d33 value at room temperature, even though they had rather lower glass transition temperatures before photocrosslinking. Some photocrosslinking mechanism for NLO polymers investigated here were considered. 相似文献
102.
Although rotaxane chemists have long believed that the tert-butyl group is bulkier than the cavity of dibenzo-24-crown-8-ether (DB24C8), it is essentially smaller than the cavity of DB24C8. The tert-butyl (or 4-tert-butylphenyl) group can actually function as an end-cap of DB24C8-based rotaxanes when the intercomponent interaction is effectively operative. When such attractive interaction is removed, deslippage occurs. [structure: see text] 相似文献
103.
Chihiro Hiraoka Masaaki Matsuda Yuya Suzuki Shigeo Fujieda Mina Tomita Ken-ichi Fuhshuku Rika Obata Shigeru Nishiyama Takeshi Sugai 《Tetrahedron: Asymmetry》2006,17(24):3358-3367
Towards the synthesis of sterically hindered optically active secondary alcohol 2, yeast strains (Candida floricola IAM 13115 and Trichosporon cutaneum IAM 12206) with si-face hydride attack on isopropyl phenylsulfonylmethyl ketone 1 were developed by screening. Strains with complementary re-facial selectivity (Pichia angusta IAM 12895 and Pichia minuta IAM 12215) were also found. Based on the substrate specificity studies of these four strains, microbial reduction was applied to the synthesis of (3S,5S)-2,6-dimethyl-3,5-heptanediol 12a. 相似文献
104.
T. Omori K. Nagasaki E. Watanabe H. Suganuma 《Journal of Radioanalytical and Nuclear Chemistry》1997,220(1):37-40
A new spectrophotometric determination of technetium has been developed by means of the solvent extraction of tris(1,10-phenanthroline)iron(II) ([Fe(phen)3
2+]) with pertechnetate into nitrobenzene. The concentration of technetium can be determined by measuring the characteristic absorbance at 516 nm (=11,700M–1·cm–1) in the organic phase. An important feature of the proposed method is that the concentration of pertechnetate can be determined without complicated processes such as the reduction of pertechnetate and the subsequent formation of a colored chelate. 相似文献
105.
Oxidative Amidation of Nitroalkanes with Amine Nucleophiles using Molecular Oxygen and Iodine 下载免费PDF全文
Jing Li Prof. Dr. Martin J. Lear Yuya Kawamoto Dr. Shigenobu Umemiya Alice R. Wong Prof. Dr. Eunsang Kwon Prof. Dr. Itaru Sato Prof. Dr. Yujiro Hayashi 《Angewandte Chemie (International ed. in English)》2015,54(44):12986-12990
The formation of amides and peptides often necessitates powerful yet mild reagent systems. The reagents used, however, are often expensive and highly elaborate. New atom‐economical and practical methods that achieve such goals are highly desirable. Ideally, the methods should start with substrates that are readily available in both chiral and non‐chiral forms and utilize cheap reagents that are compatible with a wide variety of functional groups, steric encumberance, and epimerizable stereocenters. A direct oxidative method was developed to form amide and peptide bonds between amines and primary nitroalkanes simply by using I2 and K2CO3 under O2. Contrary to expectations, a 1:1 halogen‐bonded complex forms between the iodonium source and the amine, which reacts with nitronates to form α‐iodo nitroalkanes as precursors to the amides. 相似文献
106.
Akio Kobori Taichiro Arai Yuya Sakata Takayuki Sugita Asako Yamayoshi Akira Murakami 《Tetrahedron letters》2018,59(41):3690-3693
Molecular switches controlled by light stimuli can be applicable to the variety of the biological application. In this study, skeletal structures of a chromophore of fluorescent protein were applied as aglycones of newly designed photochromic nucleosides, “Fluorescent protein-inspired nuceloside: FIN”. Phosphoramidite units of the photochromic nucleosides having imidazolinone derivatives with benzylidene or 3-pyridilidene groups were successfully synthesized for FIN-containing ODNs. Thermodynamic studies of the FIN-containing ODNs revealed that photo-irradiation with specific wavelength induced stability change of the duplexes. 相似文献
107.
108.
Masahide Takahashi Masaru Suzuki Yuya Miyagawa Rie Ihara Yomei Tokuda Toshinobu Yoko Takashi Nemoto Seiji Isoda 《Journal of Sol-Gel Science and Technology》2010,54(3):319-324
Photo-curable vinyl modified silicate-phosphate alternating copolymers were prepared by a direct condensation of organochlorosilane
and organophosphoric acid in a solvent-free condition. The obtained copolymers have complete alternating copolymer structure
of silicate and phosphate unit, where the main oxo chain consist of –(Si–O–P–O)
n
-network. They exhibited an excellent solubility of ionic species such as ionic organic dyes. It was also demonstrated the
photo-reduction of Au+ ions to form Au nano particles for plasmonics applications. Micro patterns were also fabricated by soft lithographic processes.
These results indicate that the photo-curable alternating copolymers are one of promising materials for advanced optical information
processing devices. 相似文献
109.
Michihiro Iijima Yukio Nagasaki 《Journal of polymer science. Part A, Polymer chemistry》2006,44(4):1457-1469
Poly[N‐isopropylacrylamide‐g‐poly(ethylene glycol)]s with a reactive group at the poly(ethylene glycol) (PEG) end were synthesized by the radical copolymerization of N‐isopropylacrylamide with a PEG macromonomer having an acetal group at one end and a methacryloyl group at the other chain end. The temperature dependence of the aqueous solutions of the obtained graft copolymers was estimated by light scattering measurements. The intensity of the light scattering from aqueous polymer solutions increased with increasing temperature. In particular, at temperatures above 40°C, the intensity abruptly increased, indicating a phase separation of the graft copolymer due to the lower critical solution temperature (LCST) of the poly(N‐isopropylacrylamide) segment. No turbidity was observed even above the LCST, and this suggested a nanoscale self‐assembling structure of the graft copolymer. The dynamic light scattering measurements confirmed that the size of the aggregate was in the range of several tens of nanometers. The acetal group at the end of the PEG graft chain was easily converted to the aldehyde group by an acid treatment, which was analyzed by 1H NMR. Such a temperature‐induced nanosphere possessing reactive PEG tethered chains on the surface is promising for new nanobased biomedical materials. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1457–1469, 2006 相似文献
110.
The Ramanujan Journal - In this paper, we study a continuity of the “values” of modular functions at the real quadratic numbers which are defined in terms of their cycle integrals along... 相似文献