全文获取类型
收费全文 | 1353篇 |
免费 | 50篇 |
国内免费 | 4篇 |
专业分类
化学 | 1114篇 |
晶体学 | 13篇 |
力学 | 10篇 |
数学 | 65篇 |
物理学 | 205篇 |
出版年
2023年 | 10篇 |
2022年 | 9篇 |
2021年 | 16篇 |
2020年 | 24篇 |
2019年 | 33篇 |
2018年 | 21篇 |
2017年 | 15篇 |
2016年 | 34篇 |
2015年 | 36篇 |
2014年 | 40篇 |
2013年 | 56篇 |
2012年 | 93篇 |
2011年 | 112篇 |
2010年 | 66篇 |
2009年 | 51篇 |
2008年 | 59篇 |
2007年 | 93篇 |
2006年 | 92篇 |
2005年 | 79篇 |
2004年 | 56篇 |
2003年 | 83篇 |
2002年 | 62篇 |
2001年 | 26篇 |
2000年 | 20篇 |
1999年 | 21篇 |
1998年 | 12篇 |
1997年 | 16篇 |
1996年 | 16篇 |
1995年 | 13篇 |
1994年 | 16篇 |
1993年 | 8篇 |
1992年 | 12篇 |
1991年 | 8篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 8篇 |
1984年 | 14篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1978年 | 10篇 |
1977年 | 4篇 |
1974年 | 2篇 |
1971年 | 2篇 |
1968年 | 2篇 |
排序方式: 共有1407条查询结果,搜索用时 15 毫秒
981.
Kaori Miura Hiroaki Matsuno Yuji Iwaoka Hideyuki Ito Akihiro Tai 《Molecules (Basel, Switzerland)》2021,26(15)
Allergy is an excessive immune response to a specific antigen. Type I allergies, such as hay fever and food allergies, have increased significantly in recent years and have become a worldwide problem. We previously reported that an ascorbic acid derivative having palmitoyl and glucosyl groups, 2-O-α-d-glucopyranosyl-6-O-hexadecanoyl-l-ascorbic acid (6-sPalm-AA-2G), showed inhibitory effects on degranulation in vitro and on the passive cutaneous anaphylaxis (PCA) reaction in mice. In this study, several palmitoyl derivatives of ascorbic acid were synthesized and a structure–activity relationship study was performed to discover more potent ascorbic acid derivatives with degranulation inhibitory activity. 6-Deoxy-2-O-methyl-6-(N-hexadecanoyl)amino-l-ascorbic acid (2-Me-6-N-Palm-AA), in which a methyl group was introduced into the hydroxyl group at the C-2 position of ascorbic acid and in which the hydroxyl group at the C-6 position was substituted with an N-palmitoyl group, exhibited much higher inhibitory activity for degranulation in vitro than did 6-sPalm-AA-2G. 2-Me-6-N-Palm-AA strongly inhibit the PCA reaction in mice at lower doses than those of 6-sPalm-AA-2G. These findings suggest that 2-Me-6-N-Palm-AA may be a promising therapeutic candidate for allergic diseases. 相似文献
982.
Transparent thermoplastic polymers that exhibit no birefringence are ideal for optical components such as optical films for liquid crystal displays and various lenses. Copolymerization of a positive birefringent monomer with a negative monomer is an effective technique for obtaining low birefringent polymers, especially zero‐photoelastic birefringence polymers that exhibit no photoelastic birefringence even during elastic deformation. We prepared four types of trifluoromethyl‐substituted polystyrenes. By substituting hydrogens at the ortho or meta positions of the benzene ring of polystyrene, we demonstrated that poly(2‐(trifluoromethyl)styrene), poly(3‐(trifluoromethyl)styrene), and poly(3,5‐bis(trifluoromethyl)styrene) had negative photoelastic coefficients. However, poly(4‐(trifluoromethyl)styrene) had a positive photoelastic coefficient similar to that of polystyrene. Based on these results, we synthesized a zero‐photoelastic birefringence polymer of poly(2‐(trifluoromethyl)styrene‐co‐4‐(trifluoromethyl)styrene) (55/45 wt.) exhibiting no photoelastic birefringence in elastic deformation, in which the positive photoelastic birefringence of the poly(4‐(trifluoromethyl)styrene) unit was compensated for by the negative photoelastic birefringence of the poly(2‐(trifluoromethyl)styrene) unit. The discovery of polymers having negative photoelastic coefficients is valuable for the design and synthesis of zero‐photoelastic birefringence polymers. The four types of trifluoromethyl‐substituted polystyrenes are promising optical materials because they have high transparency (transmittance > 89–92% for 27–34‐µm thickness films) in the visible and near‐infrared regions and a high decomposition temperature of approximately 400°C. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
983.
Akihiro Yokoyama Jinya Kuramochi Ryohei Kiyota Kazuki Kishimoto Kazuto Takaishi Tsutomu Yokozawa 《Journal of polymer science. Part A, Polymer chemistry》2017,55(14):2365-2372
To synthesize ladder‐type polyamides by construction of two amide bonds successively, 2,5‐diaminoterephthalic acid derivatives bearing anthranilic acid ester and isatoic anhydride moieties were synthesized and their polymerization was investigated. Polymerization of the methyl ester monomer proceeded in the presence of lithium hexamethyldisilazide (LiHMDS) as a base in tetrahydrofuran (THF). However, mass spectroscopic analysis of the product suggested that not only the bis(trimethylsilyl)amide anion of LiHMDS but also the methoxide anion eliminated at the second amide‐linkage formation reaction decomposed the isatoic anhydride unit of the growing oligomer by nucleophilic attack to disturb the polymerization. To reduce the nucleophilicity of the eliminated anion, methyl ester of the monomer was changed to phenyl ester and its polymerization was studied. The reaction conditions were optimized, and the best result was obtained when the polymerization was conducted in the presence of 1.0 equivalent of LiHMDS without additives in THF at 50 °C. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2365–2372 相似文献
984.
Takaya Murakami Reiko Ishimaru Eriko Minami Yoshiaki Iwamuro Naoki Takamura Aya Torai Tsutomu Watanabe Akihiro Miki Munehiro Katagi Maiko Kusano Hitoshi Tsuchihashi Kei Zaitsu Satoshi Chinaka 《Journal of separation science》2023,46(3):2200681
Quick, easy, cheap, effective, rugged, and safe extraction strategies are becoming increasingly adopted in various analytical fields to determine drugs in biological specimens. In the present study, we developed two fully automated quick, easy, cheap, effective, rugged, and safe extraction methods based on acetonitrile salting-out assisted liquid-liquid extraction (method 1) and acetonitrile salting-out assisted liquid-liquid extraction followed by dispersive solid-phase extraction (method 2) using a commercially available automated liquid-liquid extraction system. We applied these methods to the extraction of 14 psychotropic drugs (11 benzodiazepines and carbamazepine, quetiapine, and zolpidem) from whole blood samples. Both methods prior to liquid chromatography–tandem mass spectrometry analysis exhibited high linearity of calibration curves (correlation coefficients, > 0.9997), ppt level detection sensitivities, and satisfactory precisions (< 8.6% relative standard deviation), accuracies (within ± 16% relative error), and matrix effects (81–111%). Method 1 provided higher recovery rates (80–91%) than method 2 (72–86%), whereas method 2 provided higher detection sensitivities (limits of detection, 0.003–0.094 ng/mL) than method 1 (0.025–0.47 ng/mL) owing to the effectiveness of its dispersive solid-phase extraction cleanup step. These fully automated extraction methods realize reliable, labor-saving, user-friendly, and hygienic extraction of target analytes from whole blood samples. 相似文献
985.
Yoshiaki Tanaka Koki Ueno Keita Mizuno Kaori Takeuchi Tetsuya Asano Akihiro Sakai 《Angewandte Chemie (International ed. in English)》2023,62(13):e202217581
All-solid-state batteries (ASSBs) with inorganic solid electrolytes (SEs) have attracted significant interest as next-generation energy storage. Halides such as Li3YCl6 are promising candidates for SE because they combine high oxidation stability and deformability. However, the ionic conductivities of halide SEs are not as high as those of other SEs, especially sulfides. Here, we discover new lithium-metal-oxy-halide materials, LiMOCl4 (M=Nb, Ta). They exhibit extremely high ionic conductivities of 10.4 mS cm−1 for M=Nb and 12.4 mS cm−1 for M=Ta, respectively, even in cold-pressed powder forms at room temperature, which are comparable to or surpass those of organic liquid electrolytes used in lithium-ion batteries. Bulk-type ASSB cells using the oxyhalides as the cathode SE demonstrate an outstanding rate capability with a capacity retention of 80 % at 5 C/0.1 C. We believe that the proposed oxyhalides are promising SE candidates for the practical applications of ASSBs. 相似文献
986.
Mun Hong Loo Yuta Nakagawa Soo Hyeon Kim Akihiro Isozaki Keisuke Goda 《Electrophoresis》2022,43(3):477-486
Droplet microfluidics has emerged as a powerful tool for a diverse range of biomedical and industrial applications such as single-cell analysis, directed evolution, and metabolic engineering. In these applications, droplet sorting has been effective for isolating small droplets encapsulating molecules, cells, or crystals of interest. Recently, there is an increased interest in extending the applicability of droplet sorting to larger droplets to utilize their size advantage. However, sorting throughputs of large droplets have been limited, hampering their wide adoption. Here, we report our demonstration of high-throughput fluorescence-activated droplet sorting of 1 nL droplets using an upgraded version of the sequentially addressable dielectrophoretic array (SADA), which we reported previously. The SADA is an array of electrodes that are individually and sequentially activated/deactivated according to the speed and position of a droplet passing nearby the array. We upgraded the SADA by increasing the number of driving electrodes constituting the SADA and incorporating a slanted microchannel. By using a ten-electrode SADA with the slanted microchannel, we achieved fluorescence-activated droplet sorting of 1 nL droplets at a record high throughput of 1752 droplets/s, twice as high as the previously reported maximum sorting throughput of 1 nL droplets. 相似文献
987.
Nobuhiko Fujii Akihiro Nakamura Ray Redheffer 《Proceedings of the American Mathematical Society》1999,127(6):1815-1818
For let be complex numbers such that is bounded. For define , where . Then the excesses in the sense of Paley and Wiener satisfy .
988.
Shoji Shinoda 《Discrete Applied Mathematics》1980,2(4):349-351
The characteristic polynomial of the adjacency matrix of the subdivision graph G is related to the characteristic polynomials of the adjacency matrices of g and its line graph. 相似文献
989.
Miyakoshi R Yokoyama A Yokozawa T 《Journal of the American Chemical Society》2005,127(49):17542-17547
We studied the mechanism of the chain-growth polymerization of 2-bromo-5-chloromagnesio-3-hexylthiophene (1) with Ni(dppp)Cl2 [dppp = 1,3-bis(diphenylphosphino)propane], in which head-to-tail poly(3-hexylthiophene) (HT-P3HT) with a low polydispersity is obtained and the M(n) is controlled by the feed ratio of the monomer to the Ni catalyst. Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectra showed that the HT-P3HT uniformly had a hydrogen atom at one end of each molecule and a bromine atom at the other. The reaction of the polymer with aryl Grignard reagent gave HT-P3HT with aryl groups at both ends, which indicates that the H-end was derived from the propagating Ni complex. The degree of polymerization and the absolute molecular weight of the polymer could be evaluated from the 1H NMR spectra of the Ar/Ar-ended HT-P3HT, and it was found that one Ni catalyst molecule forms one polymer chain. Furthermore, by reaction of 1 with 50 mol % Ni(dppp)Cl2, the chain initiator was found to be a bithiophene-Ni complex, formed by a coupling reaction of 1 followed by insertion of the Ni(0) catalyst into the C-Br bond of the dimer. On the basis of these results, we propose that this chain-growth polymerization involves the coupling reaction of 1 with the polymer via the Ni catalyst, which is transferred intramolecularly to the terminal C-Br bond of the elongated molecule. We call this mechanism "catalyst-transfer polycondensation". 相似文献
990.