全文获取类型
收费全文 | 24495篇 |
免费 | 1801篇 |
国内免费 | 1308篇 |
专业分类
化学 | 12366篇 |
晶体学 | 479篇 |
力学 | 1375篇 |
综合类 | 110篇 |
数学 | 2483篇 |
物理学 | 10791篇 |
出版年
2023年 | 210篇 |
2022年 | 368篇 |
2021年 | 448篇 |
2020年 | 435篇 |
2019年 | 527篇 |
2018年 | 491篇 |
2017年 | 462篇 |
2016年 | 675篇 |
2015年 | 678篇 |
2014年 | 900篇 |
2013年 | 1376篇 |
2012年 | 1719篇 |
2011年 | 1975篇 |
2010年 | 1472篇 |
2009年 | 1453篇 |
2008年 | 1617篇 |
2007年 | 1535篇 |
2006年 | 1470篇 |
2005年 | 1159篇 |
2004年 | 1025篇 |
2003年 | 781篇 |
2002年 | 736篇 |
2001年 | 1098篇 |
2000年 | 742篇 |
1999年 | 641篇 |
1998年 | 433篇 |
1997年 | 419篇 |
1996年 | 353篇 |
1995年 | 306篇 |
1994年 | 276篇 |
1993年 | 224篇 |
1992年 | 233篇 |
1991年 | 195篇 |
1990年 | 182篇 |
1989年 | 143篇 |
1988年 | 127篇 |
1987年 | 105篇 |
1986年 | 89篇 |
1985年 | 100篇 |
1984年 | 66篇 |
1983年 | 46篇 |
1982年 | 31篇 |
1981年 | 33篇 |
1980年 | 18篇 |
1978年 | 17篇 |
1977年 | 18篇 |
1976年 | 27篇 |
1975年 | 27篇 |
1974年 | 20篇 |
1973年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 593 毫秒
31.
32.
33.
A three-dimensional molecular dynamics (MD) model is utilized to investigate the effect of tool geometry on the deformation process of the workpiece and the nature of deformation process at the atomic-scale. Results show that different states exist between the atomic force microscope (AFM) pin tool and the workpiece surface, i.e. the non-wear state, the ploughing state, the state in which ploughing is dominant and the state in which cutting plays a key role. A relationship between the deformation process of the workpiece and the potential energy variation is presented. The potential energy variation of atoms in different deformed regions in the workpiece such as plastically deformed region, elastically deformed region and the mixed deformation region is different. The features of variations of potential energy are discussed. 相似文献
34.
X. Dong 《Discrete and Computational Geometry》2002,27(1):85-97
We prove that the homotopy types of two naturally defined simplicial complexes are related in the following way: one is homotopy
equivalent to a multiple suspension of the canonical Alexander dual of the other. These simplicial complexes arise in free
resolutions of semigroup rings and modules. The relation between their homotopy types was conjectured by Reiner, and was suggested
by a homological consequence of a result due independently to Danilov and Stanley on canonical modules of normal semigroup
rings. Our proof is purely topological, and gives an alternative proof of their result. We also prove a generalization of
a result of Hochster saying that these rings are Cohen—Macaulay, and indicate a new proof of Ehrhart's reciprocity law for
rational polytopes.
Received October 3, 2000, and in revised form April 2, 2001, and May 10, 2001. Online publication November 7, 2001. 相似文献
35.
根据栅控恒压电晕充电组合反极性电晕补偿充电法的实验结果计算出铁电驻极体的极化强度.结果说明,伴随着薄膜内孔洞气体的Paschen击穿,该铁电体的极化强度随栅压增加而显著上升.利用上述充电方法和热刺激放电(TSD)谱的分析讨论了这类空间电荷型宏观电偶极子,及与其补偿的空间电荷热退极化的电荷动态特性;阐明了这两类俘获电荷的能阱分布,即构成宏观电偶极子的位于孔洞上下介质层内的等值异号空间电荷分别被俘获在深、浅两种能值陷阱内,而位于薄膜表面层的注入空间电荷则被俘获在中等能值陷阱中.
关键词:
反极性电晕补偿充电法
铁电驻极体
充电电流
热刺激放电 相似文献
36.
The results of laser induced deposition of copper on polyimide substrate from copper electrolyte solution are reported. Unlike most work reported in the literatures where CW Ar+ lasers were used, a second harmonic (532 nm wavelength) Q-switch Nd:YAG laser was used for our experiments. The deposition process was conducted by laser-catalyzing of the polyimide surface and subsequent photothermal-accelerated reduction of copper-complex ions in an alkaline reducing environment. The characteristics of the deposited copper line were investigated in terms of laser beam scanning speed, and the number of scans. The surface morphology and chemical composition of the deposited copper were analyzed using field emission scanning electron microscope (FESEM) and energy dispersive spectrometer (EDX). The optimum processing conditions have been identified. The copper deposit was found to adhere well to the substrate. 相似文献
37.
38.
The orientation-selective growth of LaNiO3 films on Si(100) by pulsed laser deposition using a MgO buffer 总被引:4,自引:0,他引:4
X.Y. Chen K.H. Wong C.L. Mak J.M. Liu X.B. Yin M. Wang Z.G. Liu 《Applied Physics A: Materials Science & Processing》2002,75(4):545-549
Highly (100)-oriented, (110)-oriented and polycrystalline LaNiO3 (LNO) films were successfully prepared on Si(100) using an oriented MgO film as a buffer. It was somewhat surprising to find
that that the orientation relation between the LNO film and the corresponding MgO buffer was: LNO(100)\MgO(110), LNO(110)\MgO(111)
and LNO(polycrystalline)\MgO(100). The crystalline quality of the LNO films was shown to be sensitive to the preparation conditions
of the MgO buffer. The film surface was very smooth, without micrometer-sized droplets being observed. All LNO films were
of metallic conductivity, with a room-temperature resistivities of approximately 250, 280 and 420 μΩ cm for the (110)-oriented,
(100)-oriented and polycrystalline LNO, respectively.
Received: 2 April 2001 / Accepted: 23 October 2001 / Published online: 3 June 2002 相似文献
39.
40.
Based on the Collins formula and irradiance moments definition, the propagation of the kurtosis parameter of super-Gaussian beams through a spherically aberrated lens is studied. Detailed numerical results are given. It is shown that, as compared with aberration-free super-Gaussian beams, the profile of spherically aberrated super-Gaussian beams can be leptokurtic, mesokurtic or platykurtic, depending on the aberration and propagation distance. The results for the spherically aberrated Gaussian beams can be dealt with as a special case treated in this paper. Finally, the advantage of our method is pointed out. 相似文献