全文获取类型
收费全文 | 1547篇 |
免费 | 74篇 |
国内免费 | 48篇 |
专业分类
化学 | 165篇 |
力学 | 97篇 |
综合类 | 14篇 |
数学 | 1127篇 |
物理学 | 266篇 |
出版年
2023年 | 30篇 |
2022年 | 36篇 |
2021年 | 25篇 |
2020年 | 48篇 |
2019年 | 44篇 |
2018年 | 20篇 |
2017年 | 34篇 |
2016年 | 50篇 |
2015年 | 37篇 |
2014年 | 86篇 |
2013年 | 115篇 |
2012年 | 77篇 |
2011年 | 91篇 |
2010年 | 83篇 |
2009年 | 95篇 |
2008年 | 100篇 |
2007年 | 88篇 |
2006年 | 71篇 |
2005年 | 53篇 |
2004年 | 49篇 |
2003年 | 29篇 |
2002年 | 51篇 |
2001年 | 43篇 |
2000年 | 24篇 |
1999年 | 27篇 |
1998年 | 37篇 |
1997年 | 27篇 |
1996年 | 15篇 |
1995年 | 15篇 |
1994年 | 29篇 |
1993年 | 24篇 |
1992年 | 12篇 |
1991年 | 8篇 |
1990年 | 11篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 10篇 |
1986年 | 4篇 |
1985年 | 17篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 9篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1973年 | 3篇 |
1970年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有1669条查询结果,搜索用时 15 毫秒
1.
《Operations Research Letters》2022,50(3):274-280
The minimum k-enclosing ball problem seeks the ball with smallest radius that contains at least k of m given points. This problem is NP-hard. We present a branch-and-bound algorithm on the tree of the subsets of k points to solve this problem. Our method is able to solve the problem exactly in a short amount of time for small and medium sized datasets. 相似文献
2.
Thalia Tsiaka Panagiotis Zoumpoulakis Vassilia J. Sinanoglou Constantinos Makris Georgios A. Heropoulos Antony C. Calokerinos 《Analytica chimica acta》2015
High-energy assisted extraction techniques, like ultrasound assisted extraction (UAE) and microwave assisted extraction (MAE), are widely applied over the last years for the recovery of bioactive compounds such as carotenoids, antioxidants and phenols from foods, animals and herbal natural sources. Especially for the case of xanthophylls, the main carotenoid group of crustaceans, they can be extracted in a rapid and quantitative way with the use of UAE and MAE. 相似文献
3.
Lubomír Kubáček 《Applications of Mathematics》2006,51(6):565-582
Some remarks to problems of point and interval estimation, testing and problems of outliers are presented in the case of multivariate
regression model.
This work was supported by the Council of Czech Government J14/98:153100011. 相似文献
4.
5.
6.
We deal with MAXH0-FREE PARTIAL SUBGRAPH. We mainly prove that 3-locally optimum solutions achieve approximation ratio (δ0+1)/(B+2+ν0), where B=maxv∈VdG(v), δ0=minv∈V(H0)dH0(v) and ν0=(|V(H0)|+1)/δ0. Next, we show that this ratio rises up to 3/(B+1) when H0=K3. Finally, we provide hardness results for MAXK3-FREE PARTIAL SUBGRAPH. 相似文献
7.
We present an O(min(Kn,n2)) algorithm to solve the maximum integral multiflow and minimum multicut problems in rooted trees, where K is the number of commodities and n is the number of vertices. These problems are NP-hard in undirected trees but polynomial in directed trees. In the algorithm we propose, we first use a greedy procedure to build the multiflow then we use duality properties to obtain the multicut and prove the optimality. 相似文献
8.
Asymptotic chi-squared test statistics for testing the equality of moment vectors are developed. The test statistics proposed are generalized Wald test statistics that specialize for different settings by inserting an appropriate asymptotic variance matrix of sample moments. Scaled test statistics are also considered for dealing with nonstandard conditions. The specialization will be carried out for testing the equality of multinomial populations, and the equality of variance and correlation matrices for both normal and nonnormal data. When testing the equality of correlation matrices, a scaled version of the normal theory chi-squared statistic is proven to be an asymptotically exact chi-squared statistic in the case of elliptical data. 相似文献
9.
根据生产实际,综合利用并列、赋闲列和拟水平试验设计,运用多重比较进行方差分析,寻找水泥熟料的最佳工艺.不仅解决了不同水平多因素试验问题,同时还可考虑交互作用,大大减少了试验次数,从而提高经济效益. 相似文献
10.
A new sample business survey for agriculture, the REA survey, and a project of integration with the FADN network (RICA in
Italy) have significantly changed the production of statistical information nowadays available with reference to the agricultural
sector. On the basis of this relevant information, new economic analyses are being developed on farms’ performance, agricultural
households’ income and the Common Agricultural Policy (CAP). In this paper the authors estimate the relationship between the
levels of variables of interest and their sampling errors using models in order to improve the accessibility of the information
on estimates accuracy to the final users (agricultural analysts, policy makers).
The paper is the result of a joint research of the three authors. Sections 1–3 and 6 by Pizzoli, Sects. 4 and 5 by Rondinelli,
Sect. 7 by Filiberti, conclusions joint to the three authors. 相似文献