全文获取类型
收费全文 | 19843篇 |
免费 | 3526篇 |
国内免费 | 2530篇 |
专业分类
化学 | 7637篇 |
晶体学 | 298篇 |
力学 | 2042篇 |
综合类 | 242篇 |
数学 | 5030篇 |
物理学 | 10650篇 |
出版年
2024年 | 40篇 |
2023年 | 226篇 |
2022年 | 377篇 |
2021年 | 586篇 |
2020年 | 723篇 |
2019年 | 635篇 |
2018年 | 578篇 |
2017年 | 693篇 |
2016年 | 853篇 |
2015年 | 794篇 |
2014年 | 1178篇 |
2013年 | 1570篇 |
2012年 | 1244篇 |
2011年 | 1310篇 |
2010年 | 1195篇 |
2009年 | 1271篇 |
2008年 | 1292篇 |
2007年 | 1250篇 |
2006年 | 1227篇 |
2005年 | 1096篇 |
2004年 | 1038篇 |
2003年 | 938篇 |
2002年 | 832篇 |
2001年 | 637篇 |
2000年 | 624篇 |
1999年 | 536篇 |
1998年 | 438篇 |
1997年 | 408篇 |
1996年 | 338篇 |
1995年 | 275篇 |
1994年 | 240篇 |
1993年 | 186篇 |
1992年 | 193篇 |
1991年 | 173篇 |
1990年 | 134篇 |
1989年 | 135篇 |
1988年 | 94篇 |
1987年 | 79篇 |
1986年 | 80篇 |
1985年 | 64篇 |
1984年 | 54篇 |
1983年 | 23篇 |
1982年 | 46篇 |
1981年 | 33篇 |
1980年 | 35篇 |
1979年 | 30篇 |
1978年 | 20篇 |
1977年 | 17篇 |
1976年 | 20篇 |
1974年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 644 毫秒
81.
An experimental method is developed to examine the near tip deformation at the mesoscopic scale level. The differential interference contrast (DIC) method is used by application of the Nomarski prism in polarized microscope for measuring the out of surface deformation. The method is very sensitive to small height changes detected by different interference color. Discussed are results for the crack tip deformation field. 相似文献
82.
有限长通电螺线管空间的磁场分布 总被引:2,自引:0,他引:2
本文计算了有限长通电螺线管空间的磁感应强度分布,给出了解析表达式,并绘出了它们的空间分布图。 相似文献
83.
A. N. Logunov 《Journal of Russian Laser Research》2004,25(4):331-348
A physical multidimensional local model of the propagation process of a laser pulse in air having no analogy to famous models in laser physics is constructed. It is based on the representations of classical wave mechanics characteristic of the theory of scalar wave fields. 相似文献
84.
According to a multiphase mixture theory, we have mathematically developed a multiphysical model with chemoelectromechanical coupling considerations, termed the multieffect‐coupling electric‐stimulus (MECe) model, to simulate the responsive behavior of electric‐sensitive hydrogels immersed in a bath solution under an externally applied electric field. For solutions of the MECe model consisting of coupled nonlinear partial differential governing equations, a meshless Hermite–Cloud method with a hierarchical iteration technique has been used for a one‐dimensional steady‐state analysis of a hydrogel strip. The computed results are compared with the experimental data, and there is very good agreement. Simulations within the domains of both hydrogels and surrounding solutions also present distributions of the ionic concentrations and electric potential as well as the hydrogel displacement. The effects of various physical parameters on the response behavior of electric‐stimulus responsive hydrogels are discussed in detail. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1514–1531, 2004 相似文献
85.
86.
半自由声场环境下的声源重建和声场预测研究对声全息技术走向实际应用具有非常重要的意义.在提出基于分布源边界点法的半自由声场全息重建和预测方法的基础上,对此展开了实验研究.并将重建和预测的结果与常规方法重建和预测的结果进行了比较和讨论,说明了重建预测过程中反射声压的影响和考虑反射声压的必要性,证明了所提出方法在解决半自由声场环境下存在地面反射时的声源重建和声场预测时的有效性和准确性.还提出了采用奇异值截断滤波和Tikhonov正则化方法来削弱测量误差的影响,从而进一步优化了重建结果,提高了全息成像的可信度.
关键词:
声全息
半自由场
边界点
声辐射
反射声 相似文献
87.
Some features of software implementation of the Pulay scaling procedure are considered. The advantages of the single value decomposition method for maintaining well-conditionality of the scale factor determination problem are demonstrated. The necessity of using a rational number of scale factors is shown. The possibility of obtaining transferable scale factors with the Pulay method and thus predict the vibrational spectra of related compounds is emphasized. 相似文献
88.
On General Mixed Quasivariational Inequalities 总被引:5,自引:0,他引:5
In this paper, we suggest and analyze several iterative methods for solving general mixed quasivariational inequalities by using the technique of updating the solution and the auxiliary principle. It is shown that the convergence of these methods requires either the pseudomonotonicity or the partially relaxed strong monotonicity of the operator. Proofs of convergence is very simple. Our new methods differ from the existing methods for solving various classes of variational inequalities and related optimization problems. Various special cases are also discussed. 相似文献
89.
Patrick Guidotti 《Mathematische Nachrichten》2004,272(1):32-45
We consider elliptic and parabolic problems in unbounded domains. We give general existence and regularity results in Besov spaces and semi‐explicit representation formulas via operator‐valued fundamental solutions which turn out to be a powerful tool to derive a series of qualitative results about the solutions. We give a sample of possible applications including asymptotic behavior in the large, singular perturbations, exact boundary conditions on artificial boundaries and validity of maximum principles. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
90.
In this paper, a generalized anti–maximum principle for the second order differential operator with potentials is proved. As an application, we will give a monotone iterative scheme for periodic solutions of nonlinear second order equations. Such a scheme involves the Lp norms of the growth, 1 ≤ p ≤ ∞, while the usual one is just the case p = ∞. 相似文献