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51.
A. Kamitani T. Takayama A. Tanaka S. Ikuno 《Physica C: Superconductivity and its Applications》2010,470(20):1189-1192
The inductive method for measuring the critical current density jC in a high-temperature superconducting (HTS) thin film has been investigated numerically. In order to simulate the method, a non-axisymmetric numerical code has been developed for analyzing the time evolution of the shielding current density. In the code, the governing equation of the shielding current density is spatially discretized with the finite element method and the resulting first-order ordinary differential system is solved by using the 5th-order Runge–Kutta method with an adaptive step-size control algorithm. By using the code, the threshold current IT is evaluated for various positions of a coil. The results of computations show that, near a film edge, the accuracy of the estimating formula for jC is remarkably degraded. Moreover, even the proportional relationship between jC and IT will be lost there. Hence, the critical current density near a film edge cannot be estimated by using the inductive method. 相似文献
52.
Yoshihiro Abe Hideo Hosono Takayuki Kamae Kouichi Kawashima 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4):113-116
Abstract Protons in alkaline-earth phosphate glasses give much higher mobility than those in silicate glasses. This is caused by the difference in O-H bonding state. Protons in P-OH form a strong hydrogen bonding with oxygen anion, resulting in formation of weak O-H bond. The electrical conductivity of the glasses is proportional to the square of the proton concentration. The activation energy for the conduction is related to νOH, peak wavenumber of infrared absorption band (around~3000 cm?1), due to fundamental O-H stretching vibration. The mobility of protons increases with decreasing νOH, which depends on the species of ions included in the phosphate glasses. 相似文献
53.
Kanako Sekimoto Mitsuo Takayama 《Journal of the American Society for Mass Spectrometry》2013,24(5):780-788
Collision-induced dissociation (CID) experiments were performed on atmospheric ion adducts [M + R]– formed between various types of organic compounds M and atmospheric negative ions R- [such as O2 –, HCO3 –, COO–(COOH), NO2 –, NO3 –, and NO3 –(HNO3)] in negative-ion mode atmospheric pressure corona discharge ionization (APCDI) mass spectrometry. All of the [M + R]– adducts were fragmented to form deprotonated analytes [M – H]– and/or atmospheric ions R–, whose intensities in the CID spectra were dependent on the proton affinities of the [M – H]– and R– fragments. Precursor ions [M + R]– for which R- have higher proton affinities than [M – H]– formed [M – H]– as the dominant product. Furthermore, the CID of the adducts with HCO3 – and NO3 -(HNO3) led to other product ions such as [M + HO]– and NO3 –, respectively. The fragmentation behavior of [M + R]– for each R– observed was independent of analyte type (e.g., whether the analyte was aliphatic or aromatic, or possessed certain functional groups). 相似文献
54.
Yusuke Fukahori Yohei Takayama Takuya Imaoka Dr. Osamu Iwamoto Prof. Dr. Kazuo Nagasawa 《化学:亚洲杂志》2013,8(1):244-250
We present a diastereoselective synthesis of disubstituted cyclopentane 8 having a nitrogen‐containing quaternary carbon center, which is found in axinellamine A ( 5 ) and related compounds. During this work, we found that the 1,3‐dipolar cycloaddition product 24 immediately underwent intramolecular redox reaction at the newly formed morpholin‐2‐one moiety, thus affording disubstituted cyclopentane containing a tertiary amine ( 9 ) stereoselectively in good yield. The amine 9 was successfully converted into guanidine 31 , which corresponds to 8 , through iminium cation–enamine isomerization. 相似文献
55.
Mariko Kitajima Minako Anbe Noriyuki Kogure Sumphan Wongseripipatana Hiromitsu Takayama 《Tetrahedron》2014
Seven new indole alkaloids (aspidofractinine type 1–3, kopsine type 5, strychnos type 6, and vincamine type 7, 8) were isolated from Kopsia jasminiflora (Apocynaceae) collected in Thailand. 5-Oxokopsinic acid (4) was isolated from nature for the first time. The structures of the new alkaloids were determined by spectroscopic analyses and chemical transformation of a known alkaloid. 5,6-Secokopsinine (1) possesses a dialdehyde function that is formed by oxidative cleavage of the C-5–C-6 bond of kopsinine (9). New vincamine-type alkaloid 8 showed potent inhibitory activity toward human cancer cell lines (A549, HT29, HCT116). 相似文献
56.
Tomohiro Kuwabara Takahiro Takayama Kenichiro Todoroki Koichi Inoue Jun Zhe Min Toshimasa Toyo’oka 《Analytical and bioanalytical chemistry》2014,406(11):2641-2649
Mass spectrometry has become a popular analytical tool because of its high sensitivity and specificity. The use of a chiral derivatization reagent for the mass spectrometry (MS) detection seems to be efficient for the enantiomeric separation of racemates. However, the number of chiral reagents for the liquid chromatography (LC)–MS/MS analysis is very limited. According to these observations, we are currently in the process of developing novel labeling reagents for chiral molecules in MS/MS analysis. The derivatization reagent that is effective for enhancing not only the electrospray ionization–MS/MS sensitivity but also the reversed-phase LC resolution of carboxylic acid enantiomers should have a highly proton-affinitive moiety and an asymmetric structure near the reactive functional group. Furthermore, the resulting derivative has to provide a characteristic product ion suitable for the selected reaction monitoring. Based upon these considerations, a series of prolylamidepyridines ((S)-N-pyrrolidine-2-carboxylic acid N-(pyridine-2-yl)amide (PCP2), (S)-N-pyrrolidine-2-carboxylic acid N-(pyridine-3-yl)amide, and (S)-N-pyrrolidine-2-carboxylic acid N-(pyridine-4-yl)amide) was synthesized as ideal labeling reagents for the enantioseparation of chiral carboxylic acids and evaluated in terms of separation efficiency and detection sensitivity by ultra-performance LC (UPLC)–MS/MS. Among the synthesized reagents, PCP2 was the most efficient chiral derivatization reagent for the enantioseparation of carboxylic acid. The Rs values and the detection limits of the derivatives of non-steroidal anti-inflammatory drugs, which were selected as the representative carboxylic acids, were in the range of 2.52–6.07 and 49–260 amol, respectively. The sensitive detection of biological carboxylic acids (detection limits, 32–520 amol) was also carried out by the proposed method using PCP2 and UPLC–MS/MS. The PCP2 was applied to the determination of carboxylic acids in human saliva. Several biological carboxylic acids, such as lactic acid (LA), 3-hydroxybutylic acid, maric acid, succinic acid, α-ketoglutalic acid, and citric acid, were clearly identified in the saliva of healthy persons and diabetic patients. Furthermore, the ratio of d-LA in diabetic patients was higher than that in normal subjects. Judging from these results, PCP2 seems to be a useful chiral derivatization reagent for the determination not only of chiral, but also achiral, carboxylic acids in real samples. Figure
Labeling reagent for carboxylic acids in chiral metabolomics study 相似文献
57.
Chalermpong Saenjum Thanawat Pattananandecha Kouichi Nakagawa 《Molecules (Basel, Switzerland)》2021,26(12)
In this study, we investigated the antioxidant and anti-inflammatory phytochemicals and paramagnetic species in dragon fruit using high-performance liquid chromatography (HPLC) and electron paramagnetic resonance (EPR). HPLC analysis demonstrated that dragon fruit is enriched with bioactive phytochemicals, with significant variations between each part of the fruit. Anthocyanins namely, cyanidin 3-glucoside, delphinidin 3-glucoside, and pelargonidin 3-glucoside were detected in the dragon fruit peel and fresh red pulp. Epicatechin gallate, epigallocatechin, caffeine, and gallic acid were found in the dragon fruit seed. Additionally, 25–100 mg × L−1 of dragon fruit pulp and peel extracts containing enrichment of cyanidin 3-glucoside were found to inhibit the production of reactive oxygen species (ROS), reactive nitrogen species (RNS), inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2) in cell-based studies without exerted cytotoxicity. EPR primarily detected two paramagnetic species in the red samples. These two different radical species were assigned as stable radicals and Mn2+ (paramagnetic species) based on the g-values and hyperfine components. In addition, the broad EPR line width of the white peel can be correlated to a unique moiety in dragon fruit. Our EPR and HPLC results provide new insight regarding the phytochemicals and related stable intermediates found in various parts of dragon fruit. Thus, we suggest here that there is the potential to use dragon fruit peel, which contains anthocyanins, as a natural active pharmaceutical ingredient. 相似文献
58.
Takayama K Arakida Y Dixit T Iwashita T Kono T Nakamura E Otsuka K Shimosaki Y Torikai K Wake M 《Physical review letters》2007,98(5):054801
We report an experimental demonstration of the induction synchrotron, the concept of which has been proposed as a future accelerator for the second generation of neutrino factory or hadron collider. The induction synchrotron supports a superbunch and a superbunch permits more charge to be accelerated while observing the constraints of the transverse space-charge limit. By using a newly developed induction acceleration system instead of radio-wave acceleration devices, a single proton bunch injected from the 500 MeV booster ring and captured by the barrier bucket created by the induction step voltages was accelerated to 6 GeV in the KEK proton synchrotron. 相似文献
59.
Kenji Shirokane Takamasa Wada Makoto Yoritate Ryo Minamikawa Nobuaki Takayama Dr. Takaaki Sato Prof. Dr. Noritaka Chida 《Angewandte Chemie (International ed. in English)》2014,53(2):512-516
A chemoselective approach for the total synthesis of (±)‐gephyrotoxin has been developed. The key to success was the utilization of N‐methoxyamides, which enabled the direct coupling of the amide with an aldehyde and selective reductive nucleophilic addition to the amide in the presence of a variety of sensitive and electrophilic functional groups, such as a methyl ester. This chemoselective approach minimized the use of protecting‐group manipulations and redox reactions, which resulted in the most concise and efficient total synthesis of (±)‐gephyrotoxin described to date. 相似文献
60.
Daisuke Saito Dr. Tomohiro Ogawa Dr. Masaki Yoshida Junichi Takayama Dr. Satoshi Hiura Prof. Dr. Akihiro Murayama Dr. Atsushi Kobayashi Prof. Dr. Masako Kato 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(42):18882-18889
A series of assembled PtII complexes comprising N-heterocyclic carbene and cyanide ligands was constructed using different substituent groups, [Pt(CN)2(R-impy)] (R-impyH+=1-alkyl-3-(2-pyridyl)-1H-imidazolium, R=Me ( Pt-Me ), Et ( Pt-Et ), iPr ( Pt- i Pr ), and tBu ( Pt- t Bu )). All the complexes exhibited highly efficient photoluminescence with an emission quantum yield of 0.51–0.81 in the solid state at room temperature, originating from the triplet metal-metal-to-ligand charge transfer (3MMLCT) state. Their emission colors cover the entire visible region from red for Pt-Me to blue for Pt- t Bu . Importantly, Pt- t Bu is the first example that exhibits blue 3MMLCT emission. The 3MMLCT emission was proved and characterized based on the temperature dependences of the crystal structures and emission properties. The wide-range color tuning of luminescence using the 3MMLCT emission presents a new strategy of superfine control of the emission color. 相似文献