全文获取类型
收费全文 | 1554篇 |
免费 | 29篇 |
国内免费 | 17篇 |
专业分类
化学 | 1042篇 |
晶体学 | 11篇 |
力学 | 23篇 |
数学 | 308篇 |
物理学 | 216篇 |
出版年
2023年 | 5篇 |
2022年 | 23篇 |
2021年 | 37篇 |
2020年 | 22篇 |
2019年 | 28篇 |
2018年 | 27篇 |
2017年 | 25篇 |
2016年 | 56篇 |
2015年 | 33篇 |
2014年 | 50篇 |
2013年 | 104篇 |
2012年 | 89篇 |
2011年 | 97篇 |
2010年 | 69篇 |
2009年 | 86篇 |
2008年 | 93篇 |
2007年 | 92篇 |
2006年 | 96篇 |
2005年 | 72篇 |
2004年 | 74篇 |
2003年 | 41篇 |
2002年 | 54篇 |
2001年 | 20篇 |
2000年 | 28篇 |
1999年 | 16篇 |
1998年 | 18篇 |
1997年 | 16篇 |
1996年 | 19篇 |
1995年 | 18篇 |
1994年 | 8篇 |
1993年 | 15篇 |
1992年 | 12篇 |
1991年 | 7篇 |
1990年 | 16篇 |
1989年 | 10篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1986年 | 8篇 |
1985年 | 13篇 |
1984年 | 15篇 |
1983年 | 12篇 |
1982年 | 14篇 |
1981年 | 10篇 |
1980年 | 9篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1973年 | 6篇 |
1966年 | 2篇 |
排序方式: 共有1600条查询结果,搜索用时 6 毫秒
111.
Point defects on oxide surfaces are presumed to be preferential nucleation sites for supported metal clusters. Under typical growth conditions, dimers constitute the first step in island nucleation. First-principles calculations on the formation of Pd dimers on regular and defect sites of the MgO(100) surface show that nucleation occurs with large dimer binding energies at divacancies and charged oxygen vacancies (F+ centers), while it is less favorable on steps and neutral F centers. The extensive database of defect trapping/attachment properties gives a firm basis to rationalize recent atomic-force microscopy findings and provides guidelines valid, in general, for ionic substrates. 相似文献
112.
113.
Pettus BJ Kroesen BJ Szulc ZM Bielawska A Bielawski J Hannun YA Busman M 《Rapid communications in mass spectrometry : RCM》2004,18(5):577-583
Normal-phase high-performance liquid chromatography (NP-HPLC) coupled to atmospheric pressure ionization mass spectrometry (APCI-MS) allows quantitative analysis of endogenous ceramide and dihydroceramide species from crude lipid extracts. Qualitative information for the species comes from observation of differences in chromatographic and mass spectrometric behavior between species (Pettus et al. Rapid Commun. Mass Spectrom. 2003; 17: 1017-1026). Quantitative analysis is achieved by (1) use of a synthetic internal standard as an extraction and injection control, (2) lack of salt adduction, ion suppression, or other matrix effects in APCI mode, and (3) consistent fragmentation and ionization of external standards across the physiologically relevant concentration range found in endogenous lipid samples. Application to the analysis and quantitation of ceramide and dihydroceramide from various cell lines is demonstrated. The results from APCI-MS analysis corroborate and enhance information acquired from use of the diacylglycerol kinase assay for total ceramide measurement. This technique readily allows simultaneous quantitation of ceramide and dihydroceramide species. 相似文献
114.
Stuart?ClaryEmail author Jacek?FabrykowskiEmail author 《Czechoslovak Mathematical Journal》2004,54(4):915-927
In this paper we establish the distribution of prime numbers in a given arithmetic progression p l for which ap + b is squarefree. 相似文献
115.
GSH and L-His are abundant biomolecules and likely biological ligands for Zn(II) under certain conditions. Potentiometric titrations provide evidence of formation of ternary Zn(II) complexes with GSH and L-His or D-His with slight stereoselectivity in favour of L-His (ca. 1 log unit of stability constant). The solution structure of the ZnH(GSH)(L-His)(H2O) complex at pH 6.8, determined by NMR, includes tridentate L-His, monodentate (sulfur) GSH, and weak interligand interactions. Calculations of competitivity of this complex for Zn(II) binding at pH 7.4 indicate that it is likely to be formed in vivo under conditions of GSH depletion. Otherwise, GSH alone emerges as a likely Zn(II) carrier. 相似文献
116.
117.
We consider natural exponential families of Lévy processes with randomized parameter. Such processes are Markov, and under suitable assumptions, pairs of such processes with shared randomization can be “stitched together” into a single harness. The stitching consists of deterministic reparametrization of the time for both processes, so that they run on adjacent time intervals, and of the choice of the appropriate law at the boundary. 相似文献
118.
Jacek Polewczak 《Journal of statistical physics》2000,100(1-2):327-362
Existence of global-in-time, spatially inhomogeneous, and L
1-renormalized solutions is proven for the model of simple reacting spheres under the assumptions that initially the system has a finite total mass, energy, and entropy. 相似文献
119.
Jacek Lubczak 《国际化学动力学杂志》2010,42(9):550-561
To establish the mechanism of reaction of formation of oligoetherols with perhydro‐1,3,5‐triazine ring, the kinetics of reaction of isocyanuric acid and 1,3,5‐tris(2‐hydroxyetyl) isocyanurate with ethylene carbonate resulting in formation of polyetherols in the presence of diazabicyclo[2.2.2]octane as a catalyst has been investigated. The kinetic and mechanistic studies revealed that the initial step of reaction is zero order related to ethylene carbonate and the reaction is inhibited by imide groups of isocyanuric acid. The mechanism of reaction was confirmed by spectroscopic and electrochemical methods. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 550–561, 2010 相似文献
120.
Krystyna Wejroch Jerzy Lange Anna Kielak Janina Karolak‐Wojciechowska Jacek Sonicki Tadeusz Jagodziski 《Journal of heterocyclic chemistry》2001,38(4):877-884
Bis(ethoxycarbonyl)alkylidene derivatives 4 and 5 of the respective title hydrazones were obtained in the reactions with diethyl oxomalonate, diethyl oxosuccinate, diethyl 2‐oxoglutarate, and diethyl oxalo‐propionate as mixtures of geometric isomers with high predominance of one of them. On heating at 160‐200° without any solvent or on refluxing in ethanol 4 cyclized to yield the corresponding pyri‐dazino[6, 1‐c]triazines 6 , whereas heating of 5 gave, depending on the chain length, the corresponding pyra‐zolylpyridazines 8b and 8d or the pyridazinylpyridazine 8c . X‐ray analysis was used to determine the structures of 6 and 8 ; the unit cell of 6c was found to accommodate 16 molecules representing four conforma‐tional varieties. The different behavior of 4 and 5 in the cyclization reactions was interpreted in terms of the tautomeric equilibrium which was shifted towards the enamine form in 4 , and towards the imine form, in 5 . Transmission of a long‐range chirality effect in 4d and 5a‐d manifested itself in the 1H nmr spectra as the magnetic non‐equivalence of the CH2 protons in one or both ester ethyl groups. 相似文献