全文获取类型
收费全文 | 760篇 |
免费 | 31篇 |
国内免费 | 2篇 |
专业分类
化学 | 574篇 |
晶体学 | 3篇 |
力学 | 21篇 |
数学 | 71篇 |
物理学 | 124篇 |
出版年
2024年 | 2篇 |
2023年 | 6篇 |
2022年 | 40篇 |
2021年 | 32篇 |
2020年 | 49篇 |
2019年 | 45篇 |
2018年 | 48篇 |
2017年 | 38篇 |
2016年 | 49篇 |
2015年 | 33篇 |
2014年 | 34篇 |
2013年 | 81篇 |
2012年 | 58篇 |
2011年 | 49篇 |
2010年 | 30篇 |
2009年 | 18篇 |
2008年 | 38篇 |
2007年 | 22篇 |
2006年 | 21篇 |
2005年 | 15篇 |
2004年 | 11篇 |
2003年 | 14篇 |
2002年 | 11篇 |
2001年 | 11篇 |
2000年 | 1篇 |
1999年 | 5篇 |
1997年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 6篇 |
1991年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1964年 | 1篇 |
1950年 | 1篇 |
1926年 | 1篇 |
1924年 | 2篇 |
1921年 | 2篇 |
排序方式: 共有793条查询结果,搜索用时 15 毫秒
81.
Mona M. Naim Nouf F. Al-harby Mervette El Batouti Mahmoud M. Elewa 《Molecules (Basel, Switzerland)》2022,27(5)
Dyes are a major class of organic pollutants that are well-known for their harmful impact on aquatic life and humans. Several new strategies for removing colours from industrial and residential effluents have recently emerged, with adsorption being the best option. The current study looked at the recovery of direct dyes from aqueous streams for reuse using macro-reticular ion exchange resins (IERs). The investigation includes dyeing single jersey cotton grey textiles with direct dyes from the Isma dye Company in Kafr El Dawar, Egypt. After centrifuging and separating the supernatant liquid, solutions from thirteen different dyes, produced at an average concentration between the wasted and soaping liquor concentrations, were calculated spectrophotometrically from the first dyeing trials. Kinetic data were well fitted with pseudo-second-order rate kinetics. The amounts of dye retained by the anion exchangers increased with a rise in temperature in the case of Strong Base Resin (SBR) and vice versa for Weak Base Resin (WBR). Batch adsorption experiments with SBR and WBR were conducted for each dye, and both Freundlich and Langmuir isotherms were constructed. It was found that adsorption obeyed both isotherms, that monolayer adsorption took place, and that the dye molecular weight, structure, and solubility, as well as the type of anionic resin used, had varying effects on the extent of absorption. The monolayer sorption capacities Q0 determined from the Langmuir isotherm model for the strongly and weakly basic anion exchangers were found to be 537.6 and 692 mg/g for Direct Yellow RL, respectively. As a result, Yellow RL exhibited the greatest adsorption on both SBR and WBR. Orange GRLL, Blue 3B, and Congo Red, on the other hand, were the poorest colours absorbed by the IERs, whereas Blue RL demonstrated good adsorption by SBR and accelerated adsorption by WBR. Most of the dyes may be recovered and reused in this manner. 相似文献
82.
The structural and thermodynamic properties of a confined hard ellipse fluid are studied using Monte Carlo simulation. The angular, average number densities and order parameters of hard ellipses confined between hard parallel walls are obtained for various bulk densities, aspect ratios and wall separations. The results show that the effect of the existence of the wall on the molecular fluid structure, either on their directions or their locations, with respect to the bulk, especially close to the walls, is significant. For this system the pressure is also obtained and it is shown that the average density at the wall is proportional to the pressure, βP=〈ρw〉. Our simulation results show that the order parameters depend on the number of the particles in the box unless it exceeds thousand. 相似文献
83.
Qamar Salamat Yadollah Yamini Morteza Moradi Abolfazl Farahani Neda Feizi 《Journal of separation science》2019,42(8):1620-1628
In the present study, a supramolecular solvent was formed from reverse micelle aggregates of octanol. The proposed supramolecular solvent was used for rapid extraction of some antidepressants drugs including amitriptyline, imipramine, desipramine, maprotiline, sertraline, and doxepin from biological samples. Alkanol‐based supramolecular solvents have a unique array of physicochemical properties, making them a very attractive alternative to replace organic solvents in analytical extractions. The parameters affecting the extraction of target analytes (i.e., the volume of tetrahydrofuran and octanol as the major components comprising the supramolecular solvent, chain length of alkanols, sample solution pH, salt addition, and ultrasonic time) were investigated and optimized by factor by factor optimization method. Under the optimum conditions, preconcentration factors of 470, 490, 460, 385, 370, and 430 were obtained for amitriptyline, doxepin, imipramine, desipramine, maprotiline, and sertraline, respectively. The linear ranges and coefficients of determination (R2) were obtained in the range of 0.01–100 μg/L and 0.9974–0.9991, respectively. Also the limits of detection (S/N = 3) of 0.003–0.03 μg/L, and precisions (n = 5) of 4.9–8.9% were calculated. Finally, the method was successfully applied for the extraction of antidepressant drugs in biological samples, and relative recoveries in the range of 91–102% were obtained. 相似文献
84.
Method validation was conducted for an enzyme-linked immunosorbent assay (ELISA) for the determination of domoic acid (DA) toxins, known to give amnesic shellfish poisoning (ASP) symptoms, in shellfish. The calibration curve range of the assay is approximately 10-260 pg/mL, with a dynamic working range for DA toxins in shellfish from 0.01 to at least 250 mg/kg. The ASP ELISA showed no significant cross-reactivity to structural analogs, and proved to be robust to deliberate alterations of the optimal running conditions. The shellfish matrix effects observed with mussels, oysters, and scallops were eliminated by diluting shellfish extracts 1:200 prior to analysis, leading to a limit of detection at 0.003 mg/kg. Thirteen blank shellfish homogenates were spiked with certified mussel material containing DA to levels in the range of 0.1-25 mg DA/kg, and analyzed in quadruplicate on 3 different days. The relative standard deviation (RSD) under intra-assay repeatability conditions ranged from 6.5 to 13.1%, and under interassay repeatability conditions the RSD ranged from 5.7 to 13.4%, with a mean value of 9.3%. The recoveries ranged from 85.5 to 106.6%, with a mean recovery of 102.2%. A method comparison was conducted with liquid chromatography with ultraviolet detection, using naturally contaminated scallop samples (n = 27) with DA levels at 0-244 mg/kg. The overall correlation coefficient was 0.960 and the slope of the regression was 1.218, indicating a good agreement between the methods. 相似文献
85.
Issa Yavari Nargess Hosseini Loghman Moradi Anvar Mirzaei 《Tetrahedron letters》2008,49(27):4239-4241
A mild, convenient, and practical one-pot procedure for direct synthesis of N,N′-dialkyl-N″-dialkylaminocarbothioyl thioureas is described via three-component reaction of cyclic secondary amines, CS2, and N,N′-dialkyl carbodiimides in water at room temperature. 相似文献
86.
Mona Adolf 《Colloid and polymer science》1924,35(6):342-344
Ohne Zusammenfassung
Die ausführliche Mitteilung erscheint in den „Kolloidchemischen Beiheften“ als VI. Mitteilung der Reihe: Physikalische Chemie
der Globuline. 相似文献
87.
Ohne Zusammenfassung 相似文献
88.
Mohamed Hassan Magda A. Barsy Eman A. El Rady Abdullah Sulaiman Al-Ayed Mona Frempong Kamal U. Sadek 《Journal of heterocyclic chemistry》2024,61(4):543-549
An efficient synthesis of novel benzo[f]Chromeno[2,3-d]pyrimidine and unknown benzo[f]chromeno[2,3-d][1,2,4]triazolopyrimidine derivatives is described utilizing ethyl-2-amino-4-phenyl-4H-benzo[f]chromene-3-carboxylate as precursor via aza-Wittig reaction. The process proved to be simple, high-yielding, and efficient. 相似文献
89.
In this article, the effect of the space dimensions on the generalized hydrogen-atom specific heat in the generalized Boltzmann-Gibbs
statistics is studied. The temperature dependence of the specific heat for a few different values of q and for different low space dimensions using Tsallis statistics is numerically calculated. The results indicate that for
a fixed value of q, as the space dimension increases the temperature range where the specific heat has a nonzero value, decreases, while the
general behavior of the specific heat does not show any change. Also, there exits a q-independent quantity related to two specific temperatures of the system which is almost linearly dependent on the space dimensions. 相似文献
90.
Alain Mona 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1964,15(3):292-300
Riassunto I metodi di calcolo presentati daPitts et al. [1] vengono estesi, previa considerazione dei vortici della fusoliera secondoAllen ePerkins [2] e del loro effetto sulle superfici portanti, ad angoli di attacco di media grandezza e applicati ad una serie di razzi in regime supersonico. Il confronto dei risultati teorici con le corrispondenti misurazioni in soffieria mostra che il punto di attacco della forza normale risultante non può essere calcolato con soddisfacente precisione se la fusoliera si estende per un lungo tratto dietro le superfici portanti. Ricerche condotte dall'autore indicano in base ai risultati finora ottenuti, che il calcolo di combinazioni fusoliera-ali può esser migliorato con mezzi relativamente semplici. Una pubblicazione completa è in preparazione.
Vorgetragen an der Tagung der Schweizerischen Physikalischen Gesellschaft am 4. Mai 1963 in Bern. 相似文献
Vorgetragen an der Tagung der Schweizerischen Physikalischen Gesellschaft am 4. Mai 1963 in Bern. 相似文献