全文获取类型
收费全文 | 1595篇 |
免费 | 96篇 |
国内免费 | 79篇 |
专业分类
化学 | 21篇 |
晶体学 | 1篇 |
力学 | 143篇 |
综合类 | 15篇 |
数学 | 1339篇 |
物理学 | 251篇 |
出版年
2023年 | 15篇 |
2022年 | 10篇 |
2021年 | 28篇 |
2020年 | 64篇 |
2019年 | 70篇 |
2018年 | 52篇 |
2017年 | 52篇 |
2016年 | 69篇 |
2015年 | 33篇 |
2014年 | 86篇 |
2013年 | 211篇 |
2012年 | 37篇 |
2011年 | 68篇 |
2010年 | 62篇 |
2009年 | 80篇 |
2008年 | 81篇 |
2007年 | 75篇 |
2006年 | 67篇 |
2005年 | 63篇 |
2004年 | 75篇 |
2003年 | 68篇 |
2002年 | 74篇 |
2001年 | 36篇 |
2000年 | 35篇 |
1999年 | 34篇 |
1998年 | 47篇 |
1997年 | 42篇 |
1996年 | 18篇 |
1995年 | 16篇 |
1994年 | 13篇 |
1993年 | 12篇 |
1992年 | 9篇 |
1991年 | 8篇 |
1990年 | 2篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 1篇 |
排序方式: 共有1770条查询结果,搜索用时 162 毫秒
991.
Ramiro S. Barbosa J. A. Tenreiro Machado Isabel M. Ferreira 《Nonlinear dynamics》2004,38(1-2):305-321
This paper presents a new strategy for tuning PID controllers based on a fractional reference model. The model is represented as an ideal closed-loop system whose open-loop is given by the Bodes ideal transfer function. The PID controller parameters are determined by the minimization of the integral square error (ISE) between the time responses of the desired fractional reference model and of the system with the PID controller. The resulting closed-loop system (with the PID controller) has the desirable feature of being robust to gain variations with step responses exhibiting an iso-damping property. Several examples are presented that demonstrate the effectiveness and validity of the proposed methodology. 相似文献
992.
We express the real connective K-theory groups
o4k–1(B
Q
) ofthe quaternion group Q
of order = 2
j
8 in terms of therepresentation theory of Q
by showing
o4k–1(B
Q
) =
Sp(S
4k+3/Q
)where is any fixed point free representation of Q
in U(2k + 2). 相似文献
993.
In this paper by Sobolev imbedding theorem and characterization theorem of generalized operators the existence of
4
4
quantum fields as generalized operators is obtained with space cut-off and a rigorous mathematical interpretation of renormalization procedure is given under white noise theory. 相似文献
994.
Let {B
t
,t[0,1]} be a fractional Brownian motion with Hurst parameter H > 1/2. Using the techniques of the Malliavin calculus we show that the trajectories of the indefinite divergence integral
t
0
u
s
B
s
belong to the Besov space
p,q
for all
, provided the integrand u belongs to the space
. Moreover, if u is bounded and belongs to
for some even integer p2 and for some large enough, then the trajectories of the indefinite divergence integral
t
0
u
s
B
s
belong to the Besov space
p,
H
. 相似文献
995.
Peer Christian Kunstmann Zeljko Strkalj 《Proceedings of the American Mathematical Society》2003,131(7):2081-2088
Let be the generator of a symmetric submarkovian semigroup in . In this note we show that on the operator admits a bounded functional calculus on the sector for each \psi_p^*$"> with
This improves a result due to M. Cowling. We apply our result to obtain maximal regularity for parabolic equations and evolutionary integral equations.
This improves a result due to M. Cowling. We apply our result to obtain maximal regularity for parabolic equations and evolutionary integral equations.
996.
Matej Pavšsič 《Foundations of Physics》2003,33(9):1277-1306
A new theory is considered according to which extended objects in n-dimensional space are described in terms of multivector coordinates which are interpreted as generalizing the concept of center of mass coordinates. While the usual center of mass is a point, by generalizing the latter concept, we associate with every extended object a set of r-loops, r=0,1,...,n–1, enclosing oriented (r+1)-dimensional surfaces represented by Clifford numbers called (r+1)-vectors or multivectors. Superpositions of multivectors are called polyvectors or Clifford aggregates and they are elements of Clifford algebra. The set of all possible polyvectors forms a manifold, called C-space. We assume that the arena in which physics takes place is in fact not Minkowski space, but C-space. This has many far reaching physical implications, some of which are discussed in this paper. The most notable is the finding that although we start from the constrained relativity in C-space we arrive at the unconstrained Stueckelberg relativistic dynamics in Minkowski space which is a subspace of C-space. 相似文献
997.
Fabrice?Baudoin Michèle?ThieullenEmail author 《Probability Theory and Related Fields》2003,127(1):1-36
For a given functional Y on the path space, we define the pinning class of the Wiener measure as the class of probabilities which admit the same conditioning given Y as the Wiener measure. Using stochastic analysis and the theory of initial enlargement of filtration, we study the transformations (not necessarily adapted) which preserve this class. We prove, in this non Markov setting, a stochastic Newton equation and a stochastic Noether theorem. We conclude the paper with some non canonical representations of Brownian motion, closely related to our study.Mathematics Subject Classification (2000): 60G44, 60H07, 60H20, 60H30 相似文献
998.
A. Rennie 《K-Theory》2003,28(2):127-165
To deal with technical issues in noncommutative geometry for nonunital algebras, we introduce a useful class of algebras and their modules. These algebras and modules allow us to extend all of the smoothness results for spectral triples to the nonunital case. In addition, we show that smooth spectral triples are closed under the C
functional calculus of self-adjoint elements. In the final section we show that our algebras allow the formulation of Poincaré Duality and that the algebras of smooth spectral triples are H-unital. 相似文献
999.
L. D. Berkovitz 《Journal of Optimization Theory and Applications》1974,14(5):521-528
A lower closure theorem for an abstract control problem is proved. The functional isJ(,u)=
G
f
0(t, (M)(t),u(t))dt and the state equations areN(t)=f(t, (M)(t),u(t)). It is shown that, if {(
k
,u
k)} is a sequence of admissible controlsu
k and corre-sponding trajectories
k
such that lim infJ(
k
,u
k)<+ and such that
k
weakly,M
k
M strongly,N
k
N weakly, and {u
k} is bounded in someL
p norm, then there is a controlu such that (,u) is admissible and lim infJ(
k
,u
k)J(,u).Dedicated to Professor M. R. HestenesThis research was supported by the National Science Foundation, Grant No. GP-33551X. 相似文献
1000.
Aly R Seadawy Muhammad Younis Muhammad Z Baber Syed T R Rizvi Muhammad S Iqbal 《理论物理通讯》2021,73(11):115004
In this study, the (3+1)-dimensional fractional time–space Kadomtsev–Petviashivili (FTSKP) equation is considered and analyzed analytically, which propagates the acoustic waves in an unmagnetized dusty plasma. The fractional derivatives are studied in a confirmable sense. The new modified extended direct algebraic (MEDA) approach is adopted to investigate the diverse nonlinear wave structures. A variety of new families of hyperbolic and trigonometric solutions are obtained in single and different combinations. The obtained results are also constructed graphically with the different parametric choices. 相似文献