全文获取类型
收费全文 | 532篇 |
免费 | 10篇 |
国内免费 | 8篇 |
专业分类
化学 | 310篇 |
晶体学 | 7篇 |
力学 | 19篇 |
数学 | 97篇 |
物理学 | 117篇 |
出版年
2022年 | 1篇 |
2021年 | 6篇 |
2020年 | 2篇 |
2019年 | 2篇 |
2018年 | 8篇 |
2017年 | 4篇 |
2016年 | 10篇 |
2015年 | 10篇 |
2014年 | 14篇 |
2013年 | 24篇 |
2012年 | 21篇 |
2011年 | 25篇 |
2010年 | 28篇 |
2009年 | 18篇 |
2008年 | 36篇 |
2007年 | 30篇 |
2006年 | 27篇 |
2005年 | 20篇 |
2004年 | 15篇 |
2003年 | 28篇 |
2002年 | 19篇 |
2001年 | 10篇 |
2000年 | 20篇 |
1999年 | 8篇 |
1998年 | 13篇 |
1997年 | 8篇 |
1996年 | 13篇 |
1995年 | 11篇 |
1994年 | 10篇 |
1993年 | 13篇 |
1992年 | 4篇 |
1991年 | 14篇 |
1990年 | 6篇 |
1989年 | 8篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 8篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1933年 | 1篇 |
排序方式: 共有550条查询结果,搜索用时 171 毫秒
51.
Kleij AW Souto B Pastor CJ Prados P de Mendoza J 《The Journal of organic chemistry》2003,68(22):8711-8714
The selective preparation and complete structural characterization of a small series of 1,2-anti-heterodisubstituted calix[4]arenes has been accomplished. These compounds were obtained in two steps from unsubstituted p-tert-butylcalix[4]arene by tribenzoylation and a subsequent one-pot, two-step sequence involving alkylation with simultaneous partial deacylation, resulting in heterodisubstituted calixarenes carrying an alkyl and an aroyl group. The monoalkyl-tribenzoyl intermediate, prior to in situ deprotection, could also be isolated. 相似文献
52.
Grirrane A Pastor A Galindo A Ienco A Mealli C Rosa P 《Chemical communications (Cambridge, England)》2003,(4):512-513
The compound [Mn(tda)(bipy)] (tda = S(CH2COO)2(2-)) features the first structurally characterized tetra-carboxylate dimanganese antiferromagnetic system with 'copper acetate' core; the binuclear units, completed by bipyridine chelates, are doubly chained by the tda anions that adopt an unprecedented mu,mu'-eta1,eta1,eta1,eta1 coordination mode. 相似文献
53.
For a k-connected graph G, we introduce the notion of a block and construct a block tree. This construction generalizes, for
, the known constructions for blocks of a connected graph. We apply the introduced notions to describe the set of vertices of a k-connected graph G such that the graph remains k-connected after deleting these vertices. We discuss some problems related to simultaneous deleting of vertices of a k-connected graph without loss of k-connectivity. Bibliography: 5 titles. 相似文献
54.
Herranz J Pastor I Castejon F de La Luna E Garcia-Cortes I Barth CJ Ascasibar E Sanchez J Tribaldos V 《Physical review letters》2000,85(22):4715-4718
Fine structures are found in the TJ-II stellarator electron temperature and density profiles, when they are measured using a high spatial resolution Thomson scattering system. These structures consist of peaks and valleys superimposed to a smooth average. Some irregularities remain in an ensemble average of discharges with similar macroscopic parameters such as line density, central temperature, and plasma current. They are found in all the magnetic configurations explored in plasmas heated by electron cyclotron waves. Their characteristics are shown and their possible origin is discussed. 相似文献
55.
Jan Andres Tom Fürst Karel Pastor 《Journal of Mathematical Analysis and Applications》2008,340(2):1132-1144
A full analogy of the celebrated Sharkovsky cycle coexistence theorem is established for lower semicontinuous (multivalued) maps on metrizable linear continua. This result is further extended to triangular maps. 相似文献
56.
Véronique Dupuis Nils Blanc Luis E. Diaz-Sanchez Arnaud Hillion Alexandre Tamion Florent Tournus Gustavo M. Pastor Andrei Rogalev Fabrice Wilhelm 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2013,67(2):1-4
In this paper, the one-way absorption property in one-dimensional dielectric/metal photonic crystal structure with a dielectric defect layer is studied. The effects of incident angle and state of polarization on one-way absorption behaviour of the anti-resonant (AR) mode are investigated. The normally incident wave from left to right propagation is totally allowed to penetrate to the structure but right to left propagation totally reflected at the same wavelength. It is found that, with increasing of the incident angle, the AR mode shifts to the lower wavelengths and its intensity decreases. Simultaneously, another AR mode with reversed one-way property appears at higher wavelength. The one-way behaviour on absorption is observed at the both states of polarizations but is localized on different wavelengths. Those effects, are suggesting that the proposed structure can be used as a direction sense polarization splitter or reflector/antireflector device. 相似文献
57.
We introduce and formalise a scheduling problem that consists in determining an optimum policy (i.e. one that minimises total inventory holding costs) to produce n part-types using a system that is able to share its capacity at all times among these part-types and that switches between an active and an inactive state for pre-known periods of time. Consequently, when active the system must produce enough reserves to meet the demand during the inactive interval. We show that there is always a simple optimum policy in which the production of the part-types is prioritised and, provided the units are properly defined, the optimum priority ordering corresponds to a non-decreasing sequence of the unit holding costs of the part-types. 相似文献
58.
59.
In this paper, we propose an algorithm named BDS (Bound-Driven Search) that combines features of exact and approximate methods.
The proposed procedure may be seen as a local search algorithm that systematically explores (in a branch-and bound sense)
the most promising nodes, thus preventing solutions from being reevaluated. Additionally, it can be regarded as an exact method
as it may be able to guarantee that the solution found is optimal. We present the application of this new algorithm to a specific
problem domain: the permutation flow shop scheduling problem with makespan objective. The subsequent computational experiments
are encouraging, as the algorithm is able to yield exact or near exact solutions to most instances of the problem. Furthermore,
the algorithm outperforms one of the best state-of-the-art algorithms for the problem. 相似文献
60.
Current work has evaluated uncertainty associated to quantification of several organic compounds present in particulate matter of atmospheric aerosols, setting out the stages of analytical procedure that contribute most to the global uncertainty. Several sources of uncertainty have been identified, which were clustered into five main contributions: sampling, extraction, clean-up, derivatization and analysis. A discussion of the main contributions to the overall uncertainty is reported, allowing authors to locate the largest ones and plan future improvements. Combined uncertainties ranged between 10-18% (alkanes), 12-16% (PAHs), 10-18% (alcohols) and 9-21% (acids). The analytical procedure was validated by analysing a standard reference material (SRM1649a, urban dust). Also, the proposed method was applied to the analysis of four samples of particulate matter. 相似文献