全文获取类型
收费全文 | 173190篇 |
免费 | 16890篇 |
国内免费 | 12072篇 |
专业分类
化学 | 92682篇 |
晶体学 | 1814篇 |
力学 | 11897篇 |
综合类 | 666篇 |
数学 | 43439篇 |
物理学 | 51654篇 |
出版年
2024年 | 223篇 |
2023年 | 1998篇 |
2022年 | 2291篇 |
2021年 | 3394篇 |
2020年 | 4110篇 |
2019年 | 3868篇 |
2018年 | 13087篇 |
2017年 | 12640篇 |
2016年 | 10389篇 |
2015年 | 5452篇 |
2014年 | 6062篇 |
2013年 | 7822篇 |
2012年 | 12656篇 |
2011年 | 19324篇 |
2010年 | 11920篇 |
2009年 | 11961篇 |
2008年 | 12900篇 |
2007年 | 14252篇 |
2006年 | 5771篇 |
2005年 | 5885篇 |
2004年 | 5093篇 |
2003年 | 4817篇 |
2002年 | 3622篇 |
2001年 | 2454篇 |
2000年 | 2226篇 |
1999年 | 2198篇 |
1998年 | 1921篇 |
1997年 | 1700篇 |
1996年 | 1745篇 |
1995年 | 1460篇 |
1994年 | 1304篇 |
1993年 | 1081篇 |
1992年 | 944篇 |
1991年 | 834篇 |
1990年 | 694篇 |
1989年 | 556篇 |
1988年 | 430篇 |
1987年 | 391篇 |
1986年 | 387篇 |
1985年 | 307篇 |
1984年 | 229篇 |
1983年 | 188篇 |
1982年 | 166篇 |
1981年 | 116篇 |
1980年 | 105篇 |
1979年 | 68篇 |
1978年 | 56篇 |
1973年 | 42篇 |
1914年 | 45篇 |
1909年 | 41篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
991.
992.
Gap length (GL) of reading head is one of the most critical parameters for high-density magnetic recording systems. A novel method is proposed for quantitative evaluation of the GL fluctuation among a batch of magneto-resistive/giant magneto-resistive heads with same structure design. The method works at head-gimbal assembly level and the evaluation can be done with any read/write analysis equipment. The testing process is based on harmonic analysis of the readback signal. The testing system consists of a selected reference head and sample heads for evaluation. A GL variation function is introduced for the evaluation of GL deviation between the reference head and sample head. This method proved to be easy for implementation and results suggest that variation of GL is considerable and has obvious effect on recording performance in high recording density systems. 相似文献
993.
Z.J. Liu H.H. Long W.C. Ye X.X. Zou Z.L. Qin E.P. Li J.S. Chen 《Journal of magnetism and magnetic materials》2006
In this paper, specific issues related to high-density perpendicular magnetic recording processes, such as transition noise properties and cross-track correlation lengths, were investigated with the help of micromagnetic analysis. The effects of media parameters were taken into consideration, including intergranular exchange coupling, and exchange distribution, irregular grain shapes, magnetization saturation distribution, and anisotropy distribution. The micromagnetic simulation results showed that the effect of anisotropy distribution on transition noise is more significant than magnetization saturation distribution, and it is crucial to reduce this effect to achieve a high signal-to-noise ratio. Additionally, a new method to further estimate the partial erasure threshold was proposed to approximate the partial erasure effects, and the relation between the microtrack jitter and total track jitter was investigated. 相似文献
994.
995.
In this paper, we study the growth of solutions of a first order linear differential equation. From this we verify that a
conjecture given by Brück is true under the restriction of the hyper order less than 1/2, and obtain some uniqueness theorems
of a nonconstant entire function and its first derivative sharing a nonzero constant CM. The results in this paper also improve
some known results. Some examples show that the results in this paper are best possible.
Project supported by the NSFC (NO. A0324617) and the RFDP (NO. 20060422049).
Received: 20 April 2006 Revised: 4 February 2007 相似文献
996.
Axel Ruhe 《BIT Numerical Mathematics》2007,47(2):239-240
997.
利用富铈混合稀土改善工业纯铝中富铁相形貌的研究 总被引:1,自引:0,他引:1
利用金相分析方法研究了富Ce混合稀土变质对含不同Fe量的工业纯铝的组织和其中富铁相形貌的影响。试验结果表明,随着Fe含量的增加,富铁相由弥散细小的颗粒状向短棒状、长针状转变;富Ce混合稀土变质使铝中的富铁相由长针状变为弥散细小的颗粒状。随着稀土含量的增加,-αAl晶粒逐渐细化,富铁相尺寸及数量逐渐减小。添加0.5%稀土时,-αAl晶粒细化效果最佳,而且富铁相呈细小颗粒状均匀分布在-αAl基体的晶界处。本文还对稀土改善富铁相的机制进行了分析。 相似文献
998.
A number of generalized metric spaces have been defined or characterized in terms of g-functions. Symmetric g-functions are discussed by C. Good, D. Jennings and A. M. Mohamad. In this paper, some questions about symmetric g-functions are answered, particularly it is shown that every sym-wg-space is expandable.
The project is supported by the NNSF (10571151) and NSF (2006J0397) of Fujian Province of China. 相似文献
999.
We demonstrate that the 3-power torsion points of the Jacobians of the principal modular curves X(3n) are fixed by the kernel of the canonical outer Galois representation of the pro-3 fundamental group of the projective line
minus three points. The proof proceeds by demonstrating the curves in question satisfy a two-part criterion given by Anderson
and Ihara. Two proofs of the second part of the criterion are provided; the first relies on a theorem of Shimura, while the
second uses the moduli interpretation.
Received: 30 September 2005 相似文献
1000.
In this paper we present several results about local MV-algebras, extending existing results given for MV-chains. The role
of local MV-algebras in sheaf representation and weak boolean product is stressed and the relationship of local MV-algebras
with varieties of MV-algebras is analyzed.
Presented by S. Pulmannova.
Received November 11, 2005; accepted in final form December 20, 2005. 相似文献