全文获取类型
收费全文 | 1668篇 |
免费 | 215篇 |
国内免费 | 155篇 |
专业分类
化学 | 125篇 |
晶体学 | 6篇 |
力学 | 203篇 |
综合类 | 25篇 |
数学 | 1181篇 |
物理学 | 498篇 |
出版年
2024年 | 8篇 |
2023年 | 19篇 |
2022年 | 38篇 |
2021年 | 41篇 |
2020年 | 43篇 |
2019年 | 35篇 |
2018年 | 45篇 |
2017年 | 53篇 |
2016年 | 62篇 |
2015年 | 42篇 |
2014年 | 74篇 |
2013年 | 124篇 |
2012年 | 77篇 |
2011年 | 92篇 |
2010年 | 76篇 |
2009年 | 101篇 |
2008年 | 101篇 |
2007年 | 110篇 |
2006年 | 107篇 |
2005年 | 93篇 |
2004年 | 62篇 |
2003年 | 91篇 |
2002年 | 80篇 |
2001年 | 52篇 |
2000年 | 50篇 |
1999年 | 53篇 |
1998年 | 53篇 |
1997年 | 47篇 |
1996年 | 24篇 |
1995年 | 30篇 |
1994年 | 24篇 |
1993年 | 23篇 |
1992年 | 16篇 |
1991年 | 8篇 |
1990年 | 18篇 |
1989年 | 9篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 7篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1983年 | 1篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1979年 | 1篇 |
1978年 | 9篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 2篇 |
排序方式: 共有2038条查询结果,搜索用时 15 毫秒
1.
Katarzyna Sujka Grayna Cacak-Pietrzak Alicja Suek Karolina Murgrabia Dariusz Dziki 《Molecules (Basel, Switzerland)》2022,27(13)
This work aimed to evaluate the effect of partial replacement of semolina with 0, 1, 5, 10, 15, and 20% of ground buckwheat hull (BH) on the chemical composition, antioxidant properties, color, cooking characteristics, and sensory properties of wheat pasta. Pasta samples were prepared by dough lamination (tagliatelle shape) and dried at 55 °C until the moisture content was 11–12% (wet basis). Analyses of samples showed that the addition of BH caused an increase in fiber content in pasta from 4.31% (control pasta) to 14.15% (pasta with 20% of BH). Moreover, the brightness and yellowness of BH-enriched products were significantly decreased compared to the control sample, and the total color difference ranged from 23.84 (pasta with 1% of BH) to 32.56 (pasta with 15% BH). In addition, a decrease in optimal cooking time, as well as an increased weight index and cooking loss, was observed in BH-enriched pasta samples. Furthermore, BH-enriched cooked pasta had significantly higher total phenolic content and antioxidant activity but an unpleasant smell and taste, especially if the level of BH was higher than 10%. 相似文献
2.
Sarvesh Kumar Jos Romero Michael Probst Thana Maihom Gustavo García Paulo Limo-Vieira 《Molecules (Basel, Switzerland)》2022,27(15)
The geometrical effect of chlorine atom positions in polyatomic molecules after capturing a low-energy electron is shown to be a prevalent mechanism yielding Cl2−. In this work, we investigated hexachlorobenzene reduction in electron transfer experiments to determine the role of chlorine atom positions around the aromatic ring, and compared our results with those using ortho-, meta- and para-dichlorobenzene molecules. This was achieved by combining gas-phase experiments to determine the reaction threshold by means of mass spectrometry together with quantum chemical calculations. We also observed that Cl2− formation can only occur in 1,2-C6H4Cl2, where the two closest C–Cl bonds are cleaved while the chlorine atoms are brought together within the ring framework due to excess energy dissipation. These results show that a strong coupling between electronic and C–Cl bending motion is responsible for a positional isomeric effect, where molecular recognition is a determining factor in chlorine anion formation. 相似文献
3.
Two types of low-light-level image sensors have been investigated for use in low distortion recording: an SIT-vidicon (Silicon-Intensifier Target), and a sensor consisting of a newvicon and two stage proxifier. The results are compared and discussed. In addition, a triggerable video frame store is described. 相似文献
4.
5.
V. I. Arnold 《Functional Analysis and Its Applications》2003,37(3):177-190
We study the graph each of whose edges connects an element of a given ring with the square of itself. For a finite commutative group (e.g., for the multiplicative group of coprime residue classes modulo a positive integer), we describe this graph explicitly: each of its connected components is an oriented attracting cycle equipped with identical
-vertex rooted trees of special form whose roots reside on the cycle. We also compute the graphs of permutation groups on not too many elements and of the subgroups of even permutations; the connected components of these graphs are also uniformly equipped cycles. 相似文献
6.
Andr Goldman Pierre Calka 《Annales de l'Institut Henri Poincaré (B) Probabilités et Statistiques》2003,39(6):90-1082
Denote by (t)=∑n1e−λnt, t>0, the spectral function related to the Dirichlet Laplacian for the typical cell
of a standard Poisson–Voronoi tessellation in
. We show that the expectation E(t), t>0, is a functional of the convex hull of a standard d-dimensional Brownian bridge. This enables us to study the asymptotic behaviour of E(t), when t→0+,+∞. In particular, we prove that the law of the first eigenvalue λ1 of
satisfies the asymptotic relation lnP{λ1t}−2dωdj(d−2)/2d·t−d/2 when t→0+, where ωd and j(d−2)/2 are respectively the Lebesgue measure of the unit ball in
and the first zero of the Bessel function J(d−2)/2. 相似文献
7.
Periodica Mathematica Hungarica - 相似文献
8.
The finiteness is proved of the set of isomorphism classes of potentially abelian geometric Galois representations with a given set of data. This is a special case of the finiteness conjecture of Fontaine and Mazur. 相似文献
9.
We investigate analytical properties of a measure geometric Laplacian which is given as the second derivative w.r.t. two atomless finite Borel measures μ and ν with compact supports supp μ ? supp ν on the real line. This class of operators includes a generalization of the well‐known Sturm‐Liouville operator as well as of the measure geometric Laplacian given by . We obtain for this differential operator under both Dirichlet and Neumann boundary conditions similar properties as known in the classical Lebesgue case for the euclidean Laplacian like Gauß‐Green‐formula, inversion formula, compactness of the resolvent and its kernel representation w.r.t. the corresponding Green function. Finally we prove nuclearity of the resolvent and give two representations of its trace. 相似文献
10.
证券价格按几何布朗运动变化的微观解释 总被引:9,自引:1,他引:9
杨智元 《数学的实践与认识》2003,33(3):52-55
金融市场研究中经常不加解释地假设证券价格按几何布朗运动变化 .本文通过假定投资者要求来自证券的期望收益率与证券价格无关 ,在理想市场的前提条件下 ,对证券价格运动将遵循有漂移率的几何布朗运动给予严格的证明 . 相似文献