首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   3152篇
  免费   118篇
  国内免费   213篇
化学   81篇
力学   101篇
综合类   31篇
数学   2798篇
物理学   472篇
  2024年   3篇
  2023年   38篇
  2022年   20篇
  2021年   50篇
  2020年   37篇
  2019年   81篇
  2018年   63篇
  2017年   68篇
  2016年   58篇
  2015年   76篇
  2014年   151篇
  2013年   273篇
  2012年   103篇
  2011年   152篇
  2010年   122篇
  2009年   203篇
  2008年   249篇
  2007年   218篇
  2006年   173篇
  2005年   139篇
  2004年   110篇
  2003年   118篇
  2002年   134篇
  2001年   83篇
  2000年   102篇
  1999年   82篇
  1998年   63篇
  1997年   79篇
  1996年   56篇
  1995年   48篇
  1994年   37篇
  1993年   29篇
  1992年   30篇
  1991年   14篇
  1990年   30篇
  1989年   16篇
  1988年   13篇
  1987年   21篇
  1986年   11篇
  1985年   18篇
  1984年   14篇
  1983年   6篇
  1982年   17篇
  1981年   18篇
  1980年   7篇
  1979年   12篇
  1978年   17篇
  1977年   13篇
  1976年   3篇
  1975年   2篇
排序方式: 共有3483条查询结果,搜索用时 15 毫秒
1.
In this paper, we define interval‐valued left‐sided and right‐sided generalized fractional double integrals. We establish inequalities of Hermite‐Hadamard like for coordinated interval‐valued convex functions by applying our newly defined integrals.  相似文献   
2.
3.
4.
5.
K-g-框架是将算子K引入到g-框架中的一种特殊框架.采用泛函分析中的技巧和方法,研究K-g-框架的稳定性,并得到了四个K-g-框架在扰动情况下稳定的充分条件.此外,结合算子K和框架算子S衍生出K-g-框架的三个等式,并通过引入参数λ建立关于K-g-框架的一些不等式.  相似文献   
6.
7.
The use of a 20-kHz probe-type sonicator irradiating downward in a 500 mL vessel was optimized for the enhancement of the sonochemical activity in terms of the geometric and operational factors. These factors included the probe immersion depth (the vertical position of the probe), input power, height of the liquid from the bottom, horizontal position of the probe, and thickness of bottom plate The sonochemical oxidation reactions were investigated both quantitatively and qualitatively using calorimetry, KI dosimetry, and luminol (Sonochemiluminescence, SCL) techniques. The sonochemical activity was very positively affected by the vertical boundaries. The highest sonochemical activity was obtained when the probe was placed close to the bottom of the vessel (immersion depth of 60 mm), with a high input power (input power of 75%), and optimal liquid height condition (liquid height of 70 mm). The SCL image analysis showed that the cavitational activity zone gradually expanded around the probe body and changed into a circular shape as the experimental conditions were optimized, and consequently the sonochemical activity increased. The formation of a large bright circular-shaped activity zone could be attributed to the strong reflections of the ultrasound firstly, at the vessel bottom and secondly, at the liquid surface. On the other hand, the cavitational activity zone and the sonochemical activity were negatively affected by the horizontal boundaries when the probe was placed close to the side wall of the vessel. In addition, it was found that the sonochemical activity was also significantly affected by the thickness of the support plate owing to the reflection and transmission of the ultrasound at the boundary between the liquid and the solid media.  相似文献   
8.
ABSTRACT

The Coupled-Cluster (CC) theory is one of the most successful high precision methods used to solve the stationary Schrödinger equation. In this article, we address the mathematical foundation of this theory with focus on the advances made in the past decade. Rather than solely relying on spectral gap assumptions (non-degeneracy of the ground state), we highlight the importance of coercivity assumptions – Gårding type inequalities – for the local uniqueness of the CC solution. Based on local strong monotonicity, different sufficient conditions for a local unique solution are suggested. One of the criteria assumes the relative smallness of the total cluster amplitudes (after possibly removing the single amplitudes) compared to the Gårding constants. In the extended CC theory the Lagrange multipliers are wave function parameters and, by means of the bivariational principle, we here derive a connection between the exact cluster amplitudes and the Lagrange multipliers. This relation might prove useful when determining the quality of a CC solution. Furthermore, the use of an Aubin–Nitsche duality type method in different CC approaches is discussed and contrasted with the bivariational principle.  相似文献   
9.
ABSTRACT

In this paper, we investigate the problem of finding a common solution to a fixed point problem involving demi-contractive operator and a variational inequality with monotone and Lipschitz continuous mapping in real Hilbert spaces. Inspired by the projection and contraction method and the hybrid descent approximation method, a new and efficient iterative method for solving the problem is introduced. Strong convergence theorem of the proposed method is established under standard and mild conditions. Our scheme generalizes and extends some of the existing results in the literature, and moreover, its computational effort is less per each iteration compared with related works.  相似文献   
10.
In this paper, some nonlocal in time differential inequalities of Sobolev type are considered. Using the nonlinear capacity method, sufficient conditions for the nonexistence of nontrivial global classical solutions are provided.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号