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排序方式: 共有467条查询结果,搜索用时 15 毫秒
91.
Dyachenko Alla Ischenko Olena Diyuk Vitaliy Goncharuk Olena Borysenko Mykola Mischanchuk Oleksandr Zakharova Tetiana Pryhunova Olha Sternik Dariush Lisnyak Vladyslav 《Research on Chemical Intermediates》2022,48(6):2607-2625
Research on Chemical Intermediates - Oxide Ni(80)Fe(20)/SiO2, Co(93)Fe(7)/SiO2, and Ni(19)Co(77)Fe(4)/SiO2 nanocomposites (NCs) were prepared using highly dispersed silica. It was modified by... 相似文献
92.
Oleksandr Trotsenko Yuri Roiter Sergiy Minko 《Journal of polymer science. Part A, Polymer chemistry》2010,48(14):1623-1627
In this article, we compare structures of protonated poly(2-vinylpyridine) globules (2D compact coils on the surface) adsorbed on the mica surface from aqueous solution when the shrinking is brought about either by discharging the molecules at an elevated pH or by adding monovalent and polyvalent salts. We study the structure of the PE coils using in situ atomic force microscopy experiments in aqueous solutions in a liquid cell. The abrupt coil-to-globule transition caused by pH changes and the discharge of polymer chains resulted in compact globules. If the pH corresponding to extended coil conformation remains unchanged, the coil shrinks due to the added salt. The size of the globule in the latter case corresponds to the unperturbed dimension of the polymer coil. There is no essential difference in the dimensions of the globules as obtained in the presence of monovalent and multivalent counterions for the studied ionic strength. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1623–1627, 2010 相似文献
93.
Nath KG Ivasenko O Miwa JA Dang H Wuest JD Nanci A Perepichka DF Rosei F 《Journal of the American Chemical Society》2006,128(13):4212-4213
We demonstrate a surprising cooperative adsorption process at the liquid-solid interface, involving self-assembly in which a three-fold hydrogen-bonding unit (trimesic acid, TMA) is forced into a linear pattern by noncovalent interaction with an alcohol. Our work shows that the unexpected linear pattern formed by coadsorption of TMA and alcohols can be modulated in size by choosing alcohols with different chain lengths. 相似文献
94.
We establish Lamperti representations for semi-stable Markov processes in locally compact groups. We also study the particular cases of processes with values in R and C under the hypothesis that they do not visit 0. These Lamperti representations yield some properties of these semi-stable Markov processes. 相似文献
95.
Chatterjee S Pathmasiri W Plashkevych O Honcharenko D Varghese OP Maiti M Chattopadhyaya J 《Organic & biomolecular chemistry》2006,4(9):1675-1686
We here show that the pKa (error limit: 0.01 to 0.03 pKa unit) of a nucleobase in a nucleotide can be modulated by the chemical nature of the 2'-substituent at the sugar moiety. This has been evidenced by the measurement of nucleobase pKa in 47 different model nucleoside 3',5'-bis- and 3'-mono-ethylphosphates. The fact that the electronic character of each of the 2'-substituents (Fig. 1) alters the chemical shift of the H2' sugar proton, and also alters the pKa of the nucleobase in the nucleotides has been evidenced by a correlation plot of pKa of N3 of pyrimidine (T/C/U) or pKa of N7 of 9-guaninyl with the corresponding deltaH2' chemical shifts at the neutral pH, which shows linear correlation with high Pearson's correlation coefficients (R = 0.85-0.97). That this modulation of the pKa of the nucleobase by a 2'-substituent is a through-bond as well as through-space effect has been proven by ab initio determined pKa estimation. Interestingly, experimental pKas of nucleobases from NMR titration and the calculated pKas (by ab initio calculations utilizing closed shell HF 6-31G** basis set) are linearly correlated with R = 0.98. It has also been observed that the difference of ground and protonated/de-protonated HOMO orbital energies (DeltaHOMO, a.u.) for the nucleobases (A/G/C/T/U) are well correlated with their pK(a)s in different 2'-substituted 3',5'-bis-ethylphosphate analogs suggesting that only the orbital energy of HOMO can be successfully used to predict the modulation of the chemical reactivity of the nucleobase by the 2'-substituent. It has also been demonstrated that pKa values of nucleobases in 3',5'-bis-ethylphosphates (Table 1) are well correlated with the change in dipole moment for the respective nucleobases after protonation or de-protonation. This work thus unambiguously shows that alteration of the thermodynamic stability (Tm) of the donor-acceptor complexes [ref. 20], as found with various 2'-modified duplexes in the antisense, siRNA or in triplexes by many workers in the field, is a result of alteration of the pseudoaromatic character of the nucleobases engineered by alteration of the chemical nature of the 2'-substitution. 相似文献
96.
Oliver Supplie Oleksandr Romanyuk Christian Koppka Matthias Steidl Andreas Nägelein Agnieszka Paszuk Lars Winterfeld Anja Dobrich Peter Kleinschmidt Erich Runge Thomas Hannappel 《Progress in Crystal Growth and Characterization of Materials》2018,64(4):103-132
The integration of III–V semiconductors with Si has been pursued for more than 25 years since it is strongly desired in various high-efficiency applications ranging from microelectronics to energy conversion. In the last decade, there have been tremendous advances in Si preparation in hydrogen-based metalorganic vapor phase epitaxy (MOVPE) environment, III–V nucleation and subsequent heteroepitaxial layer growth. Simultaneously, MOVPE itself took off in its triumphal course in solid state lighting production demonstrating its power as industrially relevant growth technique. Here, we review the recent progress in MOVPE growth of III–V-on-silicon heterostructures, preparation of the involved interfaces and fabrication of devices structures. We focus on a broad range of in situ, in system and ex situ characterization techniques. We highlight important contributions of density functional theory and kinetic growth simulations to a deeper understanding of growth phenomena and support of the experimental analysis. Besides new device concepts for planar heterostructures and the specific challenges of (001) interfaces, we also cover nano-dimensioned III–V structures, which are preferentially prepared on (111) surfaces and which emerged as veritable candidates for future optoelectronic devices. 相似文献
97.
Nazar Dovhaniuk Dr. Oleksandr P. Blahun Bohdan Sosunovych Mykhailo O. Redka Bohdan V. Vashchenko Prof. Dr. Oleksandr O. Grygorenko 《European journal of organic chemistry》2023,26(3):e202201226
A novel efficient method for the synthesis of licochalcone C in good yield on up to 30 g scale was developed. The reaction sequence included relied on the directed ortho-metalation (DOM) of bis-O-MOM-protected resorcinol for the regioselective C-prenylation, followed by metalation-formylation, selective O-deprotection of a hydroxyl group located between the formyl and prenyl groups, its methylation, and aldol reaction with p-hydroxyacetophenone. Synthesis of structurally related retrochalcones, i.e., licoagrochalcones B, C, and D, was also proposed. 相似文献
98.
99.
A.?V.?AtanovEmail author A.?V.?Loboda V.?I.?Sukovykh 《Proceedings of the Steklov Institute of Mathematics》2017,296(1):13-18
We study the problem of optimal recovery of a function analytic in a doubly connected domain from its approximately given values on one of the two components of the boundary. An optimal recovery method is obtained in the case when the error is an integer power of the modulus of the doubly connected domain. 相似文献
100.
Sergey Holovach Dr. Kostiantyn P. Melnykov Artem Skreminskiy Maksym Herasymchuk Olha Tavlui Danylo Aloshyn Dr. Petro Borysko Prof. Dr. Alexander B. Rozhenko Prof. Dr. Sergey V. Ryabukhin Prof. Dr. Dmitriy M. Volochnyuk Prof. Dr. Oleksandr O. Grygorenko 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(19):e202200331
Physico-chemical properties important to drug discovery (pKa, LogP, and aqueous solubility), as well as metabolic stability, were studied for a series of functionalized gem-difluorinated cycloalkanes and compared to those of non-fluorinated and acyclic counterparts to evaluate the impact of the fluorination. It was found that the influence of the CF2 moiety on the acidity/basicity of the corresponding carboxylic acids and amines was defined by inductive the effect of the fluorine atoms and was nearly the same for acyclic and cyclic aliphatic compounds. Lipophilicity and aqueous solubility followed more complex trends and were affected by the position of the fluorine atoms, ring size, and even the nature of the functional group present; also, significant differences were found for the acyclic and cyclic series. Also, gem-difluorination either did not affect or slightly improved the metabolic stability of the corresponding model derivatives. The presented results can be used as a guide for rational drug design employing fluorine and establish the first chapter in a catalog of the key in vitro properties of fluorinated cycloalkanes. 相似文献