全文获取类型
收费全文 | 24904篇 |
免费 | 3958篇 |
国内免费 | 3047篇 |
专业分类
化学 | 13706篇 |
晶体学 | 178篇 |
力学 | 1134篇 |
综合类 | 120篇 |
数学 | 2720篇 |
物理学 | 7492篇 |
无线电 | 6559篇 |
出版年
2024年 | 123篇 |
2023年 | 660篇 |
2022年 | 733篇 |
2021年 | 959篇 |
2020年 | 1036篇 |
2019年 | 946篇 |
2018年 | 819篇 |
2017年 | 805篇 |
2016年 | 1129篇 |
2015年 | 1191篇 |
2014年 | 1342篇 |
2013年 | 1762篇 |
2012年 | 2041篇 |
2011年 | 2079篇 |
2010年 | 1565篇 |
2009年 | 1399篇 |
2008年 | 1585篇 |
2007年 | 1404篇 |
2006年 | 1293篇 |
2005年 | 1174篇 |
2004年 | 900篇 |
2003年 | 854篇 |
2002年 | 926篇 |
2001年 | 771篇 |
2000年 | 601篇 |
1999年 | 583篇 |
1998年 | 475篇 |
1997年 | 409篇 |
1996年 | 436篇 |
1995年 | 355篇 |
1994年 | 294篇 |
1993年 | 216篇 |
1992年 | 212篇 |
1991年 | 203篇 |
1990年 | 143篇 |
1989年 | 105篇 |
1988年 | 68篇 |
1987年 | 68篇 |
1986年 | 76篇 |
1985年 | 53篇 |
1984年 | 38篇 |
1983年 | 29篇 |
1982年 | 19篇 |
1981年 | 15篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1969年 | 1篇 |
1957年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Ionics - Exploration of high-rate lithium-ion batteries (LIBs) still remains a great challenge because of the ineffective charge transfer in electrode materials. In this work, the one-dimensional... 相似文献
992.
A novel imaging tool for hepatic portal system using phase contrast technique with hydrogen peroxide‐generated O2 gas 下载免费PDF全文
Rongbiao Tang Fuhua Yan Wei‐Min Chai Wei Huang Yanan Fu Guo‐Yuan Yang Ke‐Min Chen 《Journal of synchrotron radiation》2015,22(5):1263-1267
The objective of this study was to investigate the potential of hydrogen peroxide‐generated oxygen gas‐based phase contrast imaging (PCI) for visualizing mouse hepatic portal veins. The O2 gas was made from the reaction between H2O2 and catalase. The gas production was imaged by PCI in real time. The H2O2 was injected into the enteric cavity of the lower sigmoid colon to produce O2 in the submucosal venous plexus. The generated O2 gas could be finally drained into hepatic portal veins. Absorption contrast imaging (ACI) and PCI of O2‐filled portal veins were performed and compared. PCI offers high resolution and real‐time visualization of the O2 gas production. Compared with O2‐based ACI, O2‐based PCI significantly enhanced the revealing of the portal vein in vivo. It is concluded that O2‐based PCI is a novel and promising imaging modality for future studies of portal venous disorders in mice models. 相似文献
993.
994.
随着超级计算机硬件和数值算法迅速发展, 使得目前利用密度泛函理论研究上千个原子体系的电子能带和结构等性质变得可行. 数值原子轨道基组由于其基组较小和局域等特性, 可以很好地与电子结构计算中的线性标度算法等的新算法结合, 用来研究较大尺寸的物理体系. 本文详细介绍了一款中国科学技术大学量子信息重点 实验室自主开发的基于数值原子轨道基组的第一性原理计算软件 Atomic-orbital Based Ab-initio Computation at UStc. 大量的测试结果表明: 该软件具有很好的准确性和较高的并行效率, 可以用于包含1000个原子左右的系统的电子结构和原子结构的研究以及分子动力学模拟计算. 相似文献
995.
996.
997.
The reconstruction algebra is a generalization of the preprojective algebra, and plays important roles in algebraic geometry and commutative algebra. We consider the homological property of this class of algebras by calculating the Hochschild homology and Hochschild cohomology. Let Λ t be the Yoneda algebra of a reconstruction algebra of type A 1 over a field k. In this paper, a minimal projective bimodule resolution of Λ t is constructed, and the k-dimensions of all Hochschild homology and cohomology groups of Λ t are calculated explicitly. 相似文献
998.
Uncertain multiobjective traveling salesman problem 总被引:1,自引:0,他引:1
Traveling salesman problem is a fundamental combinatorial optimization model studied in the operations research community for nearly half a century, yet there is surprisingly little literature that addresses uncertainty and multiple objectives in it. A novel TSP variation, called uncertain multiobjective TSP (UMTSP) with uncertain variables on the arc, is proposed in this paper on the basis of uncertainty theory, and a new solution approach named uncertain approach is applied to obtain Pareto efficient route in UMTSP. Considering the uncertain and combinatorial nature of UMTSP, a new ABC algorithm inserted with reverse operator, crossover operator and mutation operator is designed to this problem, which outperforms other algorithms through the performance comparison on three benchmark TSPs. Finally, a new benchmark UMTSP case study is presented to illustrate the construction and solution of UMTSP, which shows that the optimal route in deterministic TSP can be a poor route in UMTSP. 相似文献
999.
1000.