全文获取类型
收费全文 | 4628篇 |
免费 | 175篇 |
国内免费 | 17篇 |
专业分类
化学 | 3797篇 |
晶体学 | 20篇 |
力学 | 57篇 |
数学 | 491篇 |
物理学 | 455篇 |
出版年
2024年 | 3篇 |
2023年 | 37篇 |
2022年 | 139篇 |
2021年 | 203篇 |
2020年 | 121篇 |
2019年 | 151篇 |
2018年 | 124篇 |
2017年 | 102篇 |
2016年 | 177篇 |
2015年 | 168篇 |
2014年 | 148篇 |
2013年 | 313篇 |
2012年 | 351篇 |
2011年 | 354篇 |
2010年 | 231篇 |
2009年 | 177篇 |
2008年 | 283篇 |
2007年 | 319篇 |
2006年 | 269篇 |
2005年 | 226篇 |
2004年 | 196篇 |
2003年 | 163篇 |
2002年 | 130篇 |
2001年 | 47篇 |
2000年 | 50篇 |
1999年 | 39篇 |
1998年 | 45篇 |
1997年 | 29篇 |
1996年 | 35篇 |
1995年 | 17篇 |
1994年 | 23篇 |
1993年 | 20篇 |
1992年 | 19篇 |
1991年 | 13篇 |
1990年 | 9篇 |
1989年 | 4篇 |
1988年 | 8篇 |
1987年 | 8篇 |
1985年 | 6篇 |
1984年 | 14篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1976年 | 5篇 |
1975年 | 2篇 |
1937年 | 1篇 |
排序方式: 共有4820条查询结果,搜索用时 15 毫秒
11.
12.
Demetrio Pitea Laura Bonati Elena Collina Ugo Cosentino Marina Lasagni Giorgio Moro Roberto Todeschini 《Fresenius' Journal of Analytical Chemistry》1994,348(1-2):111-120
Summary The role of multivariate analysis methods in evaluating, rationalizing, and working out complex environmental problems is discussed. The discussion is organized in two sections; a literature analysis of the application of chemometric methods to PCDD/PCDF data interpretation and source correlation and a review of the role of chemometric methods in analysing the results obtained by the Authors studying PCDD/PCDF formation and destruction mechanisms in MSW combustion processes. 相似文献
13.
Marianny Yajaira Combariza Cristian Blanco Tirado Elena Stashenko Takayuki Shibamoto 《Journal of separation science》1994,17(9):643-646
The dependence of the limonene content of lemon (Citrus volkameriana) peel oil on the degree of ripeness of the fruit has been studied by using steam distillation and cold pressing to extract the oils from lemon fruit peel at different stages of maturation (green, greenish-yellow, and yellow-orange peel coloration). Samples of essential oils were analyzed by high resolution GC and GC-MS, using tetradecane as internal standard for quantitation. Forty components were detected; thirty eight were positively identified by comparison of their mass spectra (El, 70 eV) and Kováts retention indexes (determined using a non-logarithmic scale on capillary columns coated with both polar (DB-Wax) and non-polar (DB-1) stationary phases) with those of standards and with data reported in the literature. The limonene concentration reached a maximum level of 79.4% when the fruit was in the intermediate maturation stage characterized by greenish-yellow coloration. 相似文献
14.
The neutrino-electron scattering in a dense degenerate magnetized plasma under the conditions μ
2 > 2eB ≫ μE is investigated. The volume density of the neutrino energy and momentum losses due to this process are calculated. The results
we have obtained demonstrate that plasma in the presence of an external magnetic field is more transparent for neutrino than
for non-magnetized plasma. It is shown that neutrino scattering under conditions considered does not lead to the neutrino
force acting on plasma. 相似文献
15.
Functionalised hydroxylamine derivatives of (S)-prolinol prepared by a Cope elimination have been found to undergo oxidation to the nitrone either in the presence of air or a catalytic quantity of TPAP. These undergo intramolecular cycloaddition to give tricyclic isoxazolidines with high diastereoselectivity. 相似文献
16.
Elena Yu. FursovaVictor I. Ovcharenko Galina V. RomanenkoEugene V. Tretyakov 《Tetrahedron letters》2003,44(34):6397-6399
Reduction of nitronyl nitroxides using hexamethylenetetramine is a very convenient method for preparing the corresponding imino nitroxides and 2-imidazoline N-oxides. 相似文献
17.
In this paper we face the problem of stowing a containership, referred to as the Master Bay Plan Problem (MBPP); this problem
is difficult to solve due to its combinatorial nature and the constraints related to both the ship and the containers. We
present a decomposition approach that allows us to assign a priori the bays of a containership to the set of containers to
be loaded according to their final destination, such that different portions of the ship are independently considered for
the stowage. Then, we find the optimal solution of each subset of bays by using a 0/1 Linear Programming model. Finally, we
check the global ship stability of the overall stowage plan and look for its feasibility by using an exchange algorithm which
is based on local search techniques. The validation of the proposed approach is performed with some real life test cases.
This work has been developed within the research area: “The harbour as a logistic node” of the Italian Centre of Excellence
on Integrated Logistics (CIELI) of the University of Genoa, Italy 相似文献
18.
This paper addresses the problem of determining stowage plans for containers in a ship, that is the so-called master bay plan problem (MBPP). 相似文献
19.
The “true detection limit” CL,true was measured by a method proposed by Boumans et al. for 10 prominent lines of La, Ce, Pr, Nd and Sm, the most abundant rare
earth elements (REEs) in geological samples. It is demonstrated how spectral interferences can increase of CL,true. The spectra were excited in an argon arc plasma jet with evaporation powders of five complex natural samples. The data show
that there is a significant increase of CL,true in real samples containing large concentrations of such elements as Ti, Zr, Cr, Nb, Ta and REEs emitting complex spectra.
Received: 17 June 1997 / Revised: 20 October 1997 / Accepted: 26 October 1997 相似文献
20.
Elena Prestini 《Monatshefte für Mathematik》1988,105(3):207-216
LetfL
p(
n
),n2, be a radial function and letS
Rf be the spherical partial sums operator. We prove that if
thenS
Rf(x)f(x) a.e. asR. The result is false for
and
\frac{{2n}}{{n + 1}}$$
" align="middle" border="0">
.Partially supported by M.P.I. 相似文献