全文获取类型
收费全文 | 17119篇 |
免费 | 1615篇 |
国内免费 | 1641篇 |
专业分类
化学 | 3870篇 |
晶体学 | 228篇 |
力学 | 2125篇 |
综合类 | 282篇 |
数学 | 10691篇 |
物理学 | 3179篇 |
出版年
2024年 | 35篇 |
2023年 | 172篇 |
2022年 | 201篇 |
2021年 | 284篇 |
2020年 | 432篇 |
2019年 | 401篇 |
2018年 | 375篇 |
2017年 | 462篇 |
2016年 | 499篇 |
2015年 | 360篇 |
2014年 | 692篇 |
2013年 | 1136篇 |
2012年 | 843篇 |
2011年 | 981篇 |
2010年 | 944篇 |
2009年 | 1051篇 |
2008年 | 1145篇 |
2007年 | 1191篇 |
2006年 | 1029篇 |
2005年 | 930篇 |
2004年 | 836篇 |
2003年 | 887篇 |
2002年 | 863篇 |
2001年 | 608篇 |
2000年 | 580篇 |
1999年 | 507篇 |
1998年 | 467篇 |
1997年 | 366篇 |
1996年 | 309篇 |
1995年 | 272篇 |
1994年 | 224篇 |
1993年 | 164篇 |
1992年 | 166篇 |
1991年 | 132篇 |
1990年 | 117篇 |
1989年 | 84篇 |
1988年 | 78篇 |
1987年 | 60篇 |
1986年 | 67篇 |
1985年 | 71篇 |
1984年 | 53篇 |
1983年 | 27篇 |
1982年 | 64篇 |
1981年 | 49篇 |
1980年 | 37篇 |
1979年 | 27篇 |
1978年 | 20篇 |
1977年 | 15篇 |
1976年 | 17篇 |
1975年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
In this paper, we study the stability conditions of the MMAP[K]/G[K]/1/LCFS preemptive repeat queue. We introduce an embedded Markov chain of matrix M/G/1 type with a tree structure and identify conditions for the Markov chain to be ergodic. First, we present three conventional methods for the stability problem of the queueing system of interest. These methods are either computationally demanding or do not provide accurate information for system stability. Then we introduce a novel approach that develops two linear programs whose solutions provide sufficient conditions for stability or instability of the queueing system. The new approach is numerically efficient. The advantages and disadvantages of the methods introduced in this paper are analyzed both theoretically and numerically. 相似文献
32.
Norikazu Yamaguchi 《Mathematical Methods in the Applied Sciences》2005,28(13):1507-1526
In this paper we are concerned with the initial boundary value problem of the micropolar fluid system in a three dimensional bounded domain. We study the resolvent problem of the linearized equations and prove the generation of analytic semigroup and its time decay estimates. In particular, Lp–Lq type estimates are obtained. By use of the Lp–Lq estimates for the semigroup, we prove the existence theorem of global in time solution to the original nonlinear problem for small initial data. Furthermore, we study the magneto‐micropolar fluid system in the final section. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
33.
本文首先提出逆(反)对策这一新问题,给出了数学模型;探讨了“奇门遁甲”预测理论(术)中的数学问题;通过系统分析“专门遁甲”预测过程,可知它的预测过程隐含着一个特殊的逆(反)对策问题;最后指出逆(反)对策问题的广泛存在并给出案例分析. 相似文献
34.
本文证明了周期单元中带有某些硬相互作用的相对论Boltzmann方程初值问题在初值满足质量、能量和熵有限的条件下具有一个整体温和解. 相似文献
35.
本文用变换群理论对运动水平平板混合对流边界层流动的动量、能量和浓度扩散方程进行了分析,得到了与X4/(7-5n)成正比的壁面温度分布和浓度分布,同时壁面运动速度正比于X(3-n)/(7-5n)时存在相似性解.导出了相似性解方程,用四阶Runge-Kutta方法进行了计算,给出了Pr=0.72 和Sc,K1,K2,K3参数下的速度、温度和浓度分布,得出了各参数对流场、温度场的影响。 相似文献
36.
This paper considers a problem of nonlinear programming in which the objective function is the ratio of two linear functions and the constraints define a bounded and connected feasible region. Using a coordinate transformation, this problem is transformed into a simpler one, whose geometric interpretation is of particular significance. The transformation leads to a characterization of some special vertices of the feasible region from both the theoretical and operational points of view. 相似文献
37.
38.
Existence of positive solution is established for boundary value problems of non-singular for a class quasi-linear ordinary differential equation on the semi-infinite interval. The results are obtained by using the nonlinear alternative of Leray-Schauder method. 相似文献
39.
The gedanken experiment of the clock paradox is solved exactly using the general relativistic equations for a static homogeneous gravitational
field. We demonstrate that the general and special relativistic clock paradox solutions are identical and in particular that
they are identical for finite acceleration. Practical expressions are obtained for proper time and coordinate time by using the destination distance as
the key observable parameter. This solution provides a formal demonstration of the identity between the special and general
relativistic clock paradox with finite acceleration and where proper time is assumed to be the same in both formalisms. By
solving the equations of motion for a freely falling clock in a static homogeneous field elapsed times are calculated for
realistic journeys to the stars.
1 Both authors contributed equally to this paper. 相似文献
40.
Tatsien Li 《Mathematical Methods in the Applied Sciences》2006,29(13):1543-1553
By means of a direct and constructive method based on the theory of semi‐global C2 solution, the local exact boundary observability and an implicit duality between the exact boundary controllability and the exact boundary observability are shown for 1‐D quasilinear wave equations with various boundary conditions. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献