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排序方式: 共有237条查询结果,搜索用时 15 毫秒
31.
Yoshihito Naka Norio Nemoto Yihu Song 《Journal of Polymer Science.Polymer Physics》2005,43(12):1520-1531
Simultaneous kinetic measurement of microscopic infrared dichroism, macroscopic stress, and mesoscale strain was used to study the deformation mechanisms of metallocene polypropylene (MPP), ethylene–butylene rubber (EBR), and their blend (MPP/EBR = 80/20 w/w). As with pure MPP, the molecular orientation in the blend is dominated by the necking of the isotactic polypropylene matrix. During the necking passage through the mesoscale sampling area, the molecular orientation of the polypropylene matrix in the blend is smaller than that in the pure polypropylene film at the same level of mesoscale strain. However, the orientation of the EBR dispersed phase in the blend is larger than that in the pure EBR film. This may result from the partial miscibility of the two ingredients in the amorphous phases and their resultant strong interfacial interaction. The large stress supported by the MPP matrix extends to the island of the EBR domain and leads to its large deformation. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1520–1531, 2005 相似文献
32.
Kensuke Naka Adriana Gelover‐Santiago Takashi Uemura Yoshiki Chujo 《Journal of polymer science. Part A, Polymer chemistry》2003,41(5):708-715
Dithiafulvene oligomers ( 3 ) were prepared by cycloaddition polymerization of aldothioketenes with their alkynethiol tautomers derived from 1,4‐diethynylbenzene ( 2 ) with the addition of 1‐ethynyl‐4‐methylbenzene ( 1 ) as a monofunctionalized compound. Different feed ratios of 2 / 1 were used to control the molecular weights of 3 . The structures of 3 were confirmed by IR and 1H NMR spectroscopies in comparison with those of 2‐(4‐tolylidene)‐4‐tolyl‐1,3‐dithiol ( 4 ) as a model compound, which was obtained by the treatment of lithium 2‐tolylethynethiolate with water in Et2O. The number‐average degree of polymerization (DP) and the number‐average molecular weight were measured by gel permeation chromatographic and 1H NMR analysis. DP increased with an increasing feed ratio of 2 / 1 . The ultraviolet–visible spectra of 3 in diluted acetonitrile showed that the absorption maxima of 3 increased with an increasing DP of 3 . These redshifts are ascribed to an effective expansion of the π‐conjugation system in 3 . The oligomers exhibited a maximum conjugation length of seven repeating units. The redox properties of 3 were examined by cyclic voltammetry. The oxidation half‐peak potentials (Ep/2) of 3 were slightly cathodically shifted with increasing DP. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 708–715, 2003 相似文献
33.
Thermal rearrangement of Hauptmann's periplanone-A by GLC gave Persoons's periplanone-A, of which structure was determined through an X-ray crystallographic analysis of the corresponding alcohol. 相似文献
34.
Bang JK Naka H Teruya K Aimoto S Konno H Nosaka K Tatsumi T Akaji K 《The Journal of organic chemistry》2005,70(25):10596-10599
[reaction: see text] The solid-phase Horner-Emmons reaction was successfully applied for the convenient syntheses of olefin-containing protease inhibitors. The isomerization during the solid-phase Horner-Emmons reaction can be minimized simply by the use of an appropriate amount of the base. The synthesized olefin peptides, which have an olefin gamma-amino acid at the scissile site, were found to act as effective inhibitors for the HTLV-1 protease for the first time. 相似文献
35.
Pteridic acid A, a potent plant growth promoter with auxin-like activity, was synthesized enantioselectively by using the Evans asymmetric aldol reaction as the key C-C bond forming step. 相似文献
36.
37.
Tolerance, bioaccumulation, biotransformation and excretion of arsenic compounds by the fresh–water shrimp (Neocaridina denticulata) and the killifish (Oryzias latipes) (collected from the natural environment) were investigated. Tolerances (LC50) of the shrimp against disodium arsenate [abbreviated as As(V)], methylarsonic acid (MAA), dimethylarsinic acid (DMAA), and arsenobetaine (AB) were 1.5, 10, 40, and 150μg As ml?1, respectively. N. denticulata accumulated arsenic from an aqueous phase containing 1 μg As ml?1 of As(V), 10 μg As ml?1 of MAA, 30 μg As ml?1 of DMAA or 150 μg As ml?1 of AB, and biotransformed and excreted part of these species. Both methylation and demethylation of the arsenicals were observed in vivo. When living N. denticulata accumulating arsenic was transferred into an arsenic–free medium, a part of the accumulated arsenic was excreted. The concentration of methylated arsenicals relative to total arsenic was higher in the excrement than in the organism. Total arsenic accumulation in each species via food in the food chain Green algae (Chlorella vulgaris) → shrimp (N. denticulata) → killifish (O. latipes) decreased by one order of magnitude or more, and the concentration of methylated arsenic relative to total arsenic accumulated increased successively with elevation in the trophic level. Only trace amounts of monomethylarsenic species were detected in the shrimp and fish tested. Dimethylarsenic species in alga and shrimp, and trimethylarsenic species in killifish, were the predominant methylated arsenic species, respectively. 相似文献
38.
Zhaokui Wang Shigeki Naka Hiroyuki Okada 《Applied Physics A: Materials Science & Processing》2010,100(4):1103-1108
We have investigated the performance of organic light-emitting devices (OLEDs) with a rubrene-doped mixed single layer by
using 4,4′-bis[N-(1-napthyl)-N-phenyl- amion] biphenyl (α-NPD) as hole transport layer. Comparing to a conventional heterostructure OLED, equal luminance vs. current density characteristics
were obtained. In addition, maximum power efficiency was threefold improved, and the achieved value was 5.90 lm/W by optimizing
a mixing ratio of hole and electron transport materials. By evaluating the temperature dependence of the
J
–
V
characteristics for electron-injection dominated device, the electron injection from Al/LiF to mixed organic layer is attributed to Schottky thermal emission model. And the barrier height of the electron injection from Al/LiF into mixed single layer was obtained to be 0.62 eV, which is lower
than Al/Alq3 interface. Meanwhile, the mixed single-layer device exhibited superior operational durability at a half-luminance of 2,250 h
under a constant current operation mode. The reliability was improved with a factor of two compared to the heterostructure
device due to the improvement of stability in mixed organic molecules and removal of the heterojunction interface in the mixed
single-layer device. 相似文献
39.
Hiroki Soeda Ryo Towada Yusuke Ogura Tomoyo Mohri Georg Pohnert Shigefumi Kuwahara 《Tetrahedron》2019,75(11):1555-1562
The proposed structure for a moss-produced acetylenic oxylipin (10-keto-type structure) was synthesized from a known glycidol derivative by an 11-step sequence involving epoxide ring opening with a terminal acetylene and enzymatic hydrolysis of a methyl ester intermediate. The NMR spectra of the proposed structure was, however, different from those of the natural oxylipin, which prompted us to synthesize its 9-epi-isomer and two diastereomeric 12-keto-type positional isomers. Comparison of the NMR spectra of the three isomers with those of the natural oxylipin indicated that the natural oxylipin was actually a mixture of the two diastereomeric positional isomers. 相似文献
40.
Ikuo Kawashima Hiroaki Imoto Masatoshi Ishida Hiroyuki Furuta Shunsuke Yamamoto Masaya Mitsuishi Susumu Tanaka Toshiki Fujii Kensuke Naka 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(34):11812-11816
Dibenzo[b,f]arsepins possessing severely distorted cores compared to those of other heteropins were synthesized. These derivatives exhibited dual photoluminescence in the green‐to‐red region (500–700 nm) and the near‐ultraviolet region (<380 nm), which could be attributed to the planarization of the arsepin core in the lowest singlet excited (S1) state. The computational approach for the assessment of the aromatic indices revealed that the dibenzoarsepins studied show aromaticity (8π system) in the S1 states in line with Baird's rule. The lone pair electrons of the arsenic atoms play a crucial role in the aromaticity in the S1 states. 相似文献