全文获取类型
收费全文 | 28709篇 |
免费 | 4833篇 |
国内免费 | 3038篇 |
专业分类
化学 | 19126篇 |
晶体学 | 274篇 |
力学 | 1978篇 |
综合类 | 233篇 |
数学 | 3561篇 |
物理学 | 11408篇 |
出版年
2024年 | 110篇 |
2023年 | 606篇 |
2022年 | 1115篇 |
2021年 | 1093篇 |
2020年 | 1152篇 |
2019年 | 1089篇 |
2018年 | 1015篇 |
2017年 | 966篇 |
2016年 | 1409篇 |
2015年 | 1358篇 |
2014年 | 1588篇 |
2013年 | 2151篇 |
2012年 | 2525篇 |
2011年 | 2557篇 |
2010年 | 1707篇 |
2009年 | 1662篇 |
2008年 | 1813篇 |
2007年 | 1554篇 |
2006年 | 1423篇 |
2005年 | 1211篇 |
2004年 | 906篇 |
2003年 | 723篇 |
2002年 | 637篇 |
2001年 | 541篇 |
2000年 | 533篇 |
1999年 | 663篇 |
1998年 | 542篇 |
1997年 | 539篇 |
1996年 | 508篇 |
1995年 | 480篇 |
1994年 | 393篇 |
1993年 | 352篇 |
1992年 | 293篇 |
1991年 | 252篇 |
1990年 | 242篇 |
1989年 | 190篇 |
1988年 | 148篇 |
1987年 | 125篇 |
1986年 | 94篇 |
1985年 | 96篇 |
1984年 | 63篇 |
1983年 | 51篇 |
1982年 | 55篇 |
1981年 | 23篇 |
1980年 | 12篇 |
1979年 | 5篇 |
1976年 | 1篇 |
1959年 | 1篇 |
1957年 | 7篇 |
1936年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
We study a generalization of the notion of the chromatic number of a graph in which the colors assigned to adjacent vertices are required to be, in a certain sense, far apart. © 1993 John Wiley & Sons, Inc. 相似文献
92.
Q.-Y. Shao A.-D. Li J.-B. Cheng H.-Q. Ling D. Wu Z.-G. Liu N.-B. Ming C. Wang H.-W. Zhou B.-Y. Nguyen 《Applied Physics A: Materials Science & Processing》2005,81(6):1181-1185
LaAlO3 (LAO) gate dielectric films were deposited on Si substrates by low-pressure metalorganic chemical vapor deposition. The interfacial structure and composition distribution were investigated by high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), secondary-ion mass spectroscopy (SIMS), and Auger-electron spectroscopy (AES). HRTEM confirms that there exists an interfacial layer between LAO and Si in most samples. AES, SIMS, and XPS analyses indicate that the interfacial layer is compositionally graded La–Al silicate and the Al element is severely deficient close to the Si surface. Electrical properties of LAO films were evaluated. No evident difference in electrical properties between samples with and without native SiO2 layers was observed. The electrical properties are discussed in terms of LAO growth mechanisms, in relation to the interfacial structure. PACS 73.40.Qv; 81.15.Gh; 77.55.+f; 68.35.-p 相似文献
93.
94.
Differential inequality method, bounding function method and topological degree are applied to obtain the existence criterions of at least one solution for the general fourth-order differential equations under nonlinear boundary conditions, and many existing results are complemented. 相似文献
95.
基于一个描述夸克胶子火柱演化的相对论流体力学模型,研究了夸克相、强子相互作用以及非热过程(DrellYan对、粲强子衰变)的中等质量双轻子的产生.发现由于相边对夸克胶子物质演化的影响和RHIC能量核碰撞产生的夸克胶子物质具有高的初始温度,夸克相对双轻子的贡献显著增强,比那些来自强子相互作用的贡献重要,甚至能与来自非热的贡献比较.表明中等质量双轻子的增强是一个在核碰撞中产生了夸克胶子物质的可能信号.
关键词:
夸克-胶子物质
双轻子增强
相对论流体力学模型 相似文献
96.
Jie Xue Liang Chen Li Zhou Zhifeng Jia Yanping Wang Xinyuan Zhu Deyue Yan 《Journal of Polymer Science.Polymer Physics》2006,44(15):2050-2057
α‐Cyclodextrin (α‐CD) has been complexed with various poly(ethylene glycol) (PEG) derivatives in aqueous solution. It has been found that the end groups of PEG derivatives affect the complexation kinetics greatly, but have only a little influence on the thermodynamic behavior. By increasing the hydrophobicity of end groups, the complexation speeds up rapidly. On the other hand, the bulky end groups slow down the threading of polymeric guests into the cavity of CD. By changing the hydrophobicity and the size of end groups, the complexation rate can be adjusted in the range of several orders of magnitudes, which should be quite useful in the design of new supramolecular systems. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2050–2057, 2006 相似文献
97.
98.
Laser driven shocks can lead to a dynamic failure, called film spallation. Here, we use a modified laser spallation set-up
to measure the dynamic adhesion of thin films and we propose a novel diagnostic technology. Based on correlation theory, new
spallation criteria for characterizing the progressive damage at the interface between the film and the substrate are established,
such as interface delamination, film spallation and film expulsion. With the help of the theory, the degree of damage and
the dimension of damage (i.e. fracture), such as the minimum width of delamination radius, the thickness of the film etc.,
are estimated. Experiments are carried out on epoxy/stainless steel and epoxy/Al, and the experimental results show that their
dynamic bonding strengths are about 25 MPa and 20 MPa, respectively. The detailed results, analyses and discussions are presented
in this paper.
Received: 6 February 2001 / Accepted: 3 December 2001 / Published online: 11 February 2002 相似文献
99.
In situ flying height testing technology is becoming more and more important in slider–disk interaction analysis and manufacturing quality control of disk drives and head-related components. Triple harmonic method is a quite promising choice for in situ flying height analysis, compared with other in situ methods reported up to now. This paper reports results of investigations on engineering issues of applying triple harmonic method for in situ flying height analysis. The paper reports results of analysis on the effects of various testing conditions on flying height testing repeatability and accuracy. Results suggest that working at reasonable high channel density and working on the ratio between third and first harmonics will be an advantage in terms of both flying height testing sensitivity and testing repeatability. Comparing with media thickness effect, the gap-length variation among different heads will be important if it is to study flying height difference among different heads and the testing is at high channel density. Also, it is suggested to work at AC erased track, in order to reduce the non-linearity caused by hard transition. 相似文献
100.
合成了一种新型金属杂冠醚配合物[Mn6(4-amashz)6(DMF)6]·12DMF,并用X射线衍射法对其结构进行了表征.研究了该化合物修饰金电极催化氧还原的性质,结果表明,该化合物具有平面碟状结构,对在碱性溶液中的氧有显著的催化还原作用. 相似文献