全文获取类型
收费全文 | 466篇 |
免费 | 9篇 |
国内免费 | 30篇 |
专业分类
化学 | 71篇 |
力学 | 25篇 |
综合类 | 1篇 |
数学 | 365篇 |
物理学 | 43篇 |
出版年
2023年 | 1篇 |
2022年 | 9篇 |
2021年 | 5篇 |
2020年 | 8篇 |
2019年 | 12篇 |
2018年 | 5篇 |
2017年 | 4篇 |
2016年 | 5篇 |
2015年 | 8篇 |
2014年 | 14篇 |
2013年 | 89篇 |
2012年 | 7篇 |
2011年 | 34篇 |
2010年 | 17篇 |
2009年 | 42篇 |
2008年 | 38篇 |
2007年 | 24篇 |
2006年 | 21篇 |
2005年 | 21篇 |
2004年 | 22篇 |
2003年 | 12篇 |
2002年 | 13篇 |
2001年 | 12篇 |
2000年 | 7篇 |
1999年 | 5篇 |
1998年 | 8篇 |
1997年 | 9篇 |
1996年 | 10篇 |
1995年 | 10篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 4篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1978年 | 2篇 |
排序方式: 共有505条查询结果,搜索用时 15 毫秒
101.
Bing Xu Zhisheng Wu Zhaozhou Lin Chenglin Sui Xinyuan Shi Yanjiang Qiao 《Analytica chimica acta》2012
Ethanol precipitation plays a major role in the pretreatment of Flos Lonicerae Japonicae of Qingkailing injection, and is also one of the most popular purification techniques in Chinese herbal medicines. In order to monitor and have a better understanding of the ethanol precipitation process, a PLS model was built based on NIR spectroscopy and HPLC analysis of chlorogenic acid content within the framework of FDA's PAT initiative. Nevertheless, due to the complex mechanism of and the raw materials’ natural variability introduced into the ethanol precipitation process, it was unable to foresee the variations in new batches which may jeopardize the robustness of the established model. Therefore, based on the simple interval calculation (SIC) theory, a new model expansion updating strategy which could continuously expand the variation coverage of the calibration model along with the batch proceeding of ethanol precipitation process was proposed. Effects of model updating were validated by an individual batch with 60 samples. After two times of updating, the root mean squared error of prediction (RMSEP) decreased from 0.268 mg mL−1 to 0.199 mg mL−1, while the insiders in the object status plot (OSP) increased from 44 to 58, demonstrating the good performance of the proposed approach. 相似文献
102.
Xi Huai Qiang Zhi Hui Gao Xue Chuan Wang Jian Zheng Li Hui Zong Chi Min Du 《中国化学快报》2011,22(8):985-988
Structurally simple salicylaldehyde-based fluoreseent sensors for amino acids have been obtained by one-step or two-step synthesis.These sensors show significant fluorescence enhancement in the presence of many amino acids at concentrations as low as 10~5 mol/L.The reversible reaction of the aldehydes with amino acids to form imines in aqueous solution is proposed to account for the observed fluorescence enhancement. 相似文献
103.
《Discrete Mathematics》2022,345(1):112668
The following optimal stopping problem is considered. The vertices of a graph G are revealed one by one, in a random order, to a selector. He aims to stop this process at a time t that maximizes the expected number of connected components in the graph , induced by the currently revealed vertices. The selector knows G in advance, but different versions of the game are considered depending on the information that he gets about . We show that when G has N vertices and maximum degree of order , then the number of components of is concentrated around its mean, which implies that playing the optimal strategy the selector does not benefit much by receiving more information about . Results of similar nature were previously obtained by M. Lasoń for the case where G is a k-tree (for constant k). We also consider the particular cases where G is a square, triangular or hexagonal lattice, showing that an optimal selector gains cN components and we compute c with an error less than 0.005 in each case. 相似文献
104.
本文讨论了k个独立正态总体的均值和方差同时在简单半序约束下的极大似然估计的求解问题,给出了计算极大估计的迭代算法,且证明该算法收敛。 相似文献
105.
Csaba D. Tth 《Computational Geometry》2000,17(3-4):121-134
It is shown that in any polygonal art gallery of n sides it is possible to place n/3 point guards whose range of vision is 180° so that every interior point of the gallery can be seen by at least one of them. The guards can be stationed at any point of the art gallery. This settles an open problem posed by J. Urrutia. 相似文献
106.
Deng Pin Liu 《数学学报(英文版)》2015,31(2):319-330
In this paper, we generalize the conception of characteristic function in toric topology and construct many new smooth manifolds by using it. As an application, we classify the Moment-Angle manifolds and the partial quotients manifolds of them over a polygon. In the appendix we give a simple new proof for Orlik–Raymond's theorem in terms of characteristic function which gives the classification for quasitoric manifolds of dimension 4. 相似文献
107.
《代数通讯》2013,41(6):2325-2339
Abstract Order components of a finite group are introduced in Chen [Chen, G. Y. (1996c) On Thompson's conjecture. J. Algebra 185:184–193]. It was proved that PSL(3, q), where q is an odd prime power, is uniquely determined by its order components [Iranmanesh, A., Alavi, S. H., Khosravi, B. (2002a). A characterization of PSL(3, q) where q is an odd prime power. J. Pure Appl. Algebra 170(2–3): 243–254]. Also in Iranmanesh et al. [Iranmanesh, A., Alavi, S. H., Khosravi, B. (2002b). A characterization of PSL(3, q) where q = 2 n . Acta Math. Sinica, English Ser. 18(3):463–472] and [Iranmanesh, A., Alavi, S. H. (2002). A characterization of simple groups PSL(5, q). Bull. Austral. Math. Soc. 65:211–222] it was proved that PSL(3, q) for q = 2 n and PSL(5, q) are uniquely determined by their order components. In this paper we prove that PSL(p, q) can be uniquely determined by its order components, where p is an odd prime number. A main consequence of our results is the validity of Thompson's conjecture for the groups under consideration. 相似文献
108.
The main objective of the present work is enhancement of the performance of gas hydrate kinetic inhibitors in the presence of polyethylene oxide (PEO) and polypropylene oxide (PPO) for simple gas hydrate formation in a flow mini-loop apparatus. PEO and PPO are high molecular weight polymers that are not kinetic inhibitors by their self. For this investigation, a laboratory flow mini-loop apparatus was set up to measure the induction time and rate of gas hydrate formation when a hydrate-forming substance (such as C1, C3, CO2 and i-C4) is contacted with water containing dissolved inhibitor in presence or absence of PEO or PPO under suitable temperature and pressure conditions. In each experiment, water containing inhibitors blend saturated with pure gas is circulated up to a required pressure. Pressure is maintained at a constant value during experimental runs by means of required gas make-up. The effect of PEO and PPO on induction time and gas consumption during hydrate formation is investigated in the presence or absence of PVP (polyvinylpyrrolidone) and l-tyrosine as kinetic inhibitors. Results were shown that the induction time is prolonged in the presence of PEO or PPO compared to the inhibitor only. Inclusion of PPO into a kinetic hydrate inhibitor solution shows a higher enhancement in its inhibiting performance compare to PEO. Thus, the induction time for simple gas hydrate formation in presence of kinetic hydrate inhibitor with PPO is higher, compare to kinetic hydrate inhibitor with PEO. 相似文献
109.
M.R. Darafsheh 《Discrete Applied Mathematics》2009,157(4):833-837
The non-commuting graph ΓG of a non-abelian group G is defined as follows. The vertex set of ΓG is G−Z(G) where Z(G) denotes the center of G and two vertices x and y are adjacent if and only if xy≠yx. It has been conjectured that if G and H are two non-abelian finite groups such that ΓG≅ΓH, then |G|=|H| and moreover in the case that H is a simple group this implies G≅H. In this paper, our aim is to prove the first part of the conjecture for all the finite non-abelian simple groups H. Then for certain simple groups H, we show that the graph isomorphism ΓG≅ΓH implies G≅H. 相似文献
110.
In this paper, the extension of simple games to the vector case is proposed. Games with multiple qualitative criteria and multi-criteria simple games are introduced as a natural tool for modelling voting systems and related social-choice situations. After formally defining these games, the special class of monotonic multi-criteria simple games is characterized. We show that these games enable the formulation and analysis of several collective decision models proposed in the literature. Furthermore, our model can be applied to group-decision problems which cannot be analyzed in the existing frameworks. 相似文献