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71.
Li‐Ya Wang En‐Chiuan Chang Mou‐Yung Yeh Yu Hsuan Chung Jiann‐Jyh Huang Fung Fuh Wong 《Heteroatom Chemistry》2014,25(3):171-177
A new series of 1,3,4‐oxadiazole‐based aromatic and heterocyclic/phenylpyrazole derivatives 6a–c , 7a–d , and 8 were synthesized via sequential 1,3‐dipolar cyclization, hydrazidation, benzoylation, dehydrative cyclization, and the Suzuki coupling reaction. Among the derivatives, compounds 7a and 7c with the corresponding 2‐thienyl and 2‐benzo[b]thienyl (Ar) at the phenyl group located at the N‐1 position of pyrazole showed a better conjugation range. 相似文献
72.
K. C. Yung Zhixiang Cai H. S. Choy 《Applied Physics A: Materials Science & Processing》2012,107(2):351-355
In this paper, the feasibility of Ti film coated on glass substrate scribed via a 532 nm picosecond laser is investigated.
Laser irradiations from the film side and from the transparent substrate side are performed for comparison. Optical microscopy,
SEM, surface stylus and contact resistance measurement reveal that the Ti film can be completely removed with no damage to
the glass substrate, using optimized process parameters. The complete removal threshold for the film for front-side scribing
is found at 120 mJ/cm2, while the minimum laser fluence for complete scribing is 70 mJ/cm2 in the case of back-side scribing. The lines scribed from the front side exhibit obvious thermal effects such as heat affected
zones, burr and micro cracks. Back-side scribing exhibits non-thermal behavior, which also can increase the process speed
for the scribing of a Ti film on glass to 1000 mm/s. This makes the back-side laser scribing of Ti film a promising technique. 相似文献
73.
In this paper, we examine the best time to sell a stock at a price being as close as possible to its highest price over a finite time horizon [0, T ], where the stock price is modelled by a geometric Brownian motion and the ’closeness’ is measured by the relative error of the stock price to its highest price over [0, T ]. More precisely, we want to optimize the expression: where (V t ) t≥0 is a geometric Brownian motion with constant drift α and constant volatility σ > 0, M t = max Vs is the running maximum of the stock price, and the supremum is taken over all possible stopping times 0 ≤τ≤ T adapted to the natural filtration (F t ) t≥0 of the stock price. The above problem has been considered by Shiryaev, Xu and Zhou (2008) and Du Toit and Peskir (2009). In this paper we provide an independent proof that when α = 1 2 σ 2 , a selling strategy is optimal if and only if it sells the stock either at the terminal time T or at the moment when the stock price hits its maximum price so far. Besides, when α > 1 2 σ 2 , selling the stock at the terminal time T is the unique optimal selling strategy. Our approach to the problem is purely probabilistic and has been inspired by relating the notion of dominant stopping ρτ of a stopping time τ to the optimal stopping strategy arisen in the classical "Secretary Problem". 相似文献
74.
Wu J Lin W Wang Z Chen S Chang Y 《Langmuir : the ACS journal of surfaces and colloids》2012,28(19):7436-7441
The strong surface hydration layer of nonfouling materials plays a key role in their resistance to nonspecific protein adsorption. Poly(sulfobetaine methacrylate) (polySBMA) is an effective material that can resist nonspecific protein adsorption and cell adhesion. About eight water molecules are tightly bound with one sulfobetaine (SB) unit, and additional water molecules over 8:1 ratio mainly swell the polySBMA matrix, which is obtained through the measurement of T(2) relaxation time by low-field nuclear magnetic resonance (LF-NMR). This result was also supported by the endothermic behavior of water/polySBMA mixtures measured by differential scanning calorimetry (DSC). Furthermore, by comparing both results of polySBMA and poly(ethylene glycol) (PEG), it is found that (1) the hydrated water molecules on the SB unit are more tightly bound than on the ethylene glycol (EG) unit before saturation, and (2) the additional water molecules after forming the hydration layer in polySBMA solutions show higher freedom than those in PEG. These results might illustrate the reason for higher resistance of zwitterionic materials to nonspecific protein adsorptions compared to that of PEGs. 相似文献
75.
Yung Yang Noelia Rosales-Conrado Vanesa Guillén-Casla María Eugenia León-González Luis Vicente Pérez-Arribas Luis María Polo-Díez 《Chromatographia》2012,75(23-24):1365-1375
A heart-cut two-dimensional high-performance liquid chromatography method for enantiomeric determination of salbutamol, salmeterol and atenolol in urine is presented. It involves the use of two separations in a liquid chromatography?Cliquid chromatography achiral?Cchiral coupling. Target compounds were previously separated in a primary column (Kinetex? HILIC, 2.6???m, 150?×?2.1?mm I.D.) with a mixture of MeOH:ACN:ammonium acetate buffer (5?mM, pH 6) 90:5:5 (v/v/v) as mobile phase at a flow rate of 0.40?mL?min?1. Enantiomeric separation was carried out by transferring peak of each compound through a switching valve to a vancomycin chiral column (Chirobiotic? V, 2.6???m, 150?×?2.1?mm I.D.) using MeOH:ammonium acetate buffer (2?mM, pH 4) 97:3 (v/v) as mobile phase at a flow rate of 0.50?mL?min?1. Ultraviolet detection was done at 227?nm. The method was applied to determine target analytes in urine samples after enzymatic hydrolysis with ??-glucuronidase from Helix pomatia, followed by a solid-phase extraction procedure using Isolute? HCX mixed-mode cartridges. Extraction recoveries ranged from 82 to 90?% in urine samples. Detection limits were 0.091?C0.095???g for each enantiomer of atenolol and between 0.058 and 0.076 and 0.18?C0.14???g for enantiomers of salbutamol and salmeterol, respectively (3?mL of urine). Linearity ranges were between 0.5 and 10???g?mL?1. Intraday and interday reproducibilities of enantiomeric ratio and enantiomeric fraction, expressed as relative standard deviation, were between 1.9 and 9.0?%. The optimized method was successfully applied to the analysis of urine samples obtained from excretion studies in volunteers and in freeze-dried urine samples, containing urinary components with MW?<?10,000 and components with MW?>?10,000, spiked with different amounts of studied drugs. 相似文献
76.
Preparation of the enantiomeric pair of 3‐[2‐(3‐benzenesulfonylamino‐7‐oxabicyclo[2.2.1]hept‐2‐yl‐methyl)phenyl] propionic acid, a novel thromboxane antagonist is reported. They are synthesized from either enantiomers of known (1R,2R,3R,4S)‐3‐[2‐(3‐carboxy‐7‐oxabicyclo[2,2,1]hept‐2‐yl‐methyl)phenyl]‐propionic acid methyl ester via epimerization, modified Curtius' rearrangement and sulfonylamino formation. Other derivatives may be prepared similarly. 相似文献
77.
Hung‐Te Chang Kuo‐Chen Chiang Fung Fuh Wong Chun‐Sheng Huang Yang‐Ming Liao Wen‐Fa Kuo Shaw‐Bing Won Mou‐Yung Yeh 《Heteroatom Chemistry》2007,18(4):438-442
The synthesis of potential fluorescent active 4‐(5‐aryl‐1,3,4‐oxadiazol‐2‐yl)phenylhydrazine derivatives was accomplished in three steps. The key step was the dehydration cyclization of 1,2‐diacylhydrazines to form the 1,3,4‐oxadiazole ring by use of acetic anhydride/perchloric acid mixture as the dehydrating agent. The sydnone moiety served as the masked hydrazines, which could be demasked by HCl for further application. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:438–442, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20318 相似文献
78.
79.
The effects of instanton-anti-instanton interactions in high-temperature QCD with colour SU(2) are studied with and without quarks. The instanton potential proves to have no repulsive core, thus creating troubles with the definition of nonperturbative contributions to physical quantities. Also the chiral condensate is calculated, and it is shown to vanish if number of quark flavoursN f≧2, whereas forN f=1 it is nonzero for the arbitrary high temperature. 相似文献
80.
The structural phase transition in tin-modified zirconium titanate was investigated using high-temperature X-ray, DTA, DSC and electrical conductivity. In a dilute solid solution of Sn (x 0.2) in Zr1−xSnxTiO4, we ascribed to the successive phase transition from normal to incommensurate the break of electrical conductivity, thermal anomalies, and specific heat anomalies occurring at temperatures of 1121 °C, 1124 °C and 1125 °C on the heating run, and at temperatures of 1121 °C, 1116 °C and 1117 °C on the cooling run, respectively. Furthermore, the super-lattice reflection intensity was inversely proportional to the Sn content, cooling rate and electrical activation energy. With a composition of Zr0.8Sn0.2TiO4, the phase transition from normal to incommensurate was completely inhibited. 相似文献