全文获取类型
收费全文 | 6306篇 |
免费 | 252篇 |
国内免费 | 54篇 |
专业分类
化学 | 3715篇 |
晶体学 | 62篇 |
力学 | 245篇 |
综合类 | 2篇 |
数学 | 1424篇 |
物理学 | 1164篇 |
出版年
2023年 | 52篇 |
2022年 | 161篇 |
2021年 | 173篇 |
2020年 | 173篇 |
2019年 | 198篇 |
2018年 | 186篇 |
2017年 | 166篇 |
2016年 | 270篇 |
2015年 | 200篇 |
2014年 | 277篇 |
2013年 | 448篇 |
2012年 | 427篇 |
2011年 | 460篇 |
2010年 | 252篇 |
2009年 | 284篇 |
2008年 | 339篇 |
2007年 | 286篇 |
2006年 | 217篇 |
2005年 | 200篇 |
2004年 | 198篇 |
2003年 | 167篇 |
2002年 | 152篇 |
2001年 | 94篇 |
2000年 | 91篇 |
1999年 | 53篇 |
1998年 | 41篇 |
1997年 | 52篇 |
1996年 | 71篇 |
1995年 | 61篇 |
1994年 | 49篇 |
1993年 | 53篇 |
1992年 | 46篇 |
1991年 | 46篇 |
1990年 | 42篇 |
1989年 | 27篇 |
1988年 | 38篇 |
1987年 | 45篇 |
1986年 | 43篇 |
1985年 | 37篇 |
1984年 | 48篇 |
1983年 | 28篇 |
1982年 | 43篇 |
1981年 | 34篇 |
1980年 | 32篇 |
1979年 | 42篇 |
1978年 | 35篇 |
1977年 | 34篇 |
1976年 | 35篇 |
1975年 | 24篇 |
1974年 | 24篇 |
排序方式: 共有6612条查询结果,搜索用时 15 毫秒
901.
Kuo-Chih Hung 《Journal of Mathematical Analysis and Applications》2011,375(1):294-309
We study bifurcation diagrams of positive solutions for the p-Laplacian Dirichlet problem
902.
Nguyen Thi Thu Hang 《Journal of Mathematical Analysis and Applications》2011,376(2):656-674
A well-known result of Nevanlinna states that for two nonconstant meromorphic functions f and g on the complex plane C and for four distinct values aj∈C∪{∞}, if νf−aj=νg−aj for all 1?j?4, then g is a Möbius transformation of f. In 1983, Gundersen generalized the result of Nevanlinna to the case where the above condition is replaced by: min{νf−aj,1}=min{νg−aj,1} for j=1,2 and νf−aj=νg−aj for j=3,4. In this paper, we prove that the theorem of Gundersen remains valid to the case where min{νf−aj,1}=min{νg−aj,1} for j=1,2, and min{νf−aj,2}=min{νg−aj,2} for j=3,4. Furthermore, we work on the case where {aj} are small functions. 相似文献
903.
In this paper, we start with the consideration of direct collocation-based Runge-Kutta-Nyström (RKN) methods with continuous output formulas for solving nonstiff initial-value problems (IVPs) for systems of special second-order differential equations y″(t) = f(t, y(t)). At nth step, the continuous output formulas can be used for calculating the step values at (n + 2)th step and the integration processes can be proceeded twostep-by-twostep. In this case, we obtain twostep-by-twostep RKN methods with continuous output formulas (continuous TBTRKN methods). Furthermore, we consider a parallel predictor-corrector (PC) iteration scheme using the continuous TBTRKN methods as corrector methods with predictor methods defined by the continuous output formulas. The resulting twostep-by-twostep parallel-iterated RKN-type PC methods with continuous output formulas (twostep-by-twostep continuous PIRKN-type PC methods or TBTCPIRKN methods) give us a faster integration processes. Numerical comparisons based on the solution of a few widely-used test problems show that the new TBTCPIRKN methods are much more efficient than the well-known PIRKN methods, the famous nonstiff sequential ODEX2, DOP853 codes and comparable with the CPIRKN methods. 相似文献
904.
In this paper, a hybrid control based on pulse width modulator (PWM) is proposed to synchronize a class of master–slave chaotic systems with uncertainties. We use the Genetic Algorithm (GA) together with fuzzy logic to tune the switching time of PWM mode controller such that the output response of master–slave chaotic system can be synchronized. Finally, an example, uncertain master–slave Duffing–Holmes chaos system, is proposed to show the proposed method’s effectiveness for chaotic synchronization. 相似文献
905.
We first define the notion of the infimum at infinity of a polynomial function and the notion of stability at infinity near the fiber of the gradient descent system. Then we prove that the gradient descent system is stable at infinity near the fiber of the infimum value at infinity. 相似文献
906.
Nguyen Le Hoang Anh Phan Quoc Khanh 《Nonlinear Analysis: Theory, Methods & Applications》2011,74(6):2358-2379
We develop elements of calculus of variational sets for set-valued mappings, which were recently introduced in Khanh and Tuan (2008) [1] and [2] to replace generalized derivatives in establishing optimality conditions in nonsmooth optimization. Most of the usual calculus rules, from chain and sum rules to rules for unions, intersections, products and other operations on mappings, are established. Direct applications in stability and optimality conditions for various vector optimization problems are provided. 相似文献
907.
Nguyen Van Luong Nguyen Xuan Thuan 《Nonlinear Analysis: Theory, Methods & Applications》2011,74(3):983-992
In this paper, we prove some coupled fixed point theorems for mappings having a mixed monotone property in partially ordered metric spaces. The main results of this paper are generalizations of the main results of Bhaskar and Lakshmikantham [T. Gnana Bhaskar, V. Lakshmikantham, Fixed point theorems in partially ordered metric spaces and applications, Nonlinear Anal. TMA 65 (2006) 1379-1393]. As an application, we discuss the existence and uniqueness for a solution of a nonlinear integral equation. 相似文献
908.
This study is motivated by the paper of Skouri et al. [Skouri, Konstantaras, Papachristos, Ganas, European Journal of Operational Research 192 (1) (2009) 79–92]. We extend their inventory model from ramp type demand rate and Weibull deterioration rate to arbitrary demand rate and arbitrary deterioration rate in the consideration of partial backorder. We demonstrate that the optimal solution is actually independent of demand. That is, for a finite time horizon, any attempt at tackling targeted inventory models under ramp type or any other types of the demand becomes redundant. Our analytical approach dramatically simplifies the solution procedure. 相似文献
909.
In this study, we present a heterogeneous cooperative parallel search that integrates branch-and-bound method and tabu search
algorithm. These two algorithms perform searches in parallel and cooperate by asynchronously exchanging information about
the best solutions found and new initial solutions for tabu search. The rapid production of a good solution from the tabu
search process provides the branch-and-bound process with a better feasible solution to accelerate the elimination of subproblems
that do not contain an optimal solution. The new initial solution produced from the subproblem with a least-cost lower bound
of the branch-and-bound method suggests the best potential area for tabu search to explore. We use a master-slave model to
reduce the complexity of communication and enhance the performance of data exchange. A branch-and-bound process is used as
the master process to control the exchange of information and the termination of computation. Several tabu search processes
are executed simultaneously as the slave processes and cooperate by asynchronously exchanging information on the best solutions
found and the new initial solutions by the master process of branch-and-bound. Based on the computation experiments of solving
traveling salesman problems (TSP), the proposed heterogeneous parallel search algorithm outperforms a conventional parallel
branch-and-bound method and a conventional parallel tabu search. We also present the computational results showing the efficiency
of heterogeneous cooperative parallel search when we use more processors to accelerate search time. Thus, the proposed heterogeneous
parallel search algorithm achieves linear accelerations. 相似文献
910.
Nguyen HT Tran HQ Nguyen TT Chau VM Bui KA Pham QL Nguyen MC Kim YH 《Chemical & pharmaceutical bulletin》2011,59(11):1417-1420
Ten oleanane-type saponins (1-10), including three new compounds, namely bifinosides A-C (1-3), were isolated from the roots of Panax bipinnatifidus SEEM. Their structures were elucidated on the basis of chemical and spectroscopic methods. 相似文献