全文获取类型
收费全文 | 13854篇 |
免费 | 1342篇 |
国内免费 | 961篇 |
专业分类
化学 | 1384篇 |
晶体学 | 42篇 |
力学 | 667篇 |
综合类 | 215篇 |
数学 | 6874篇 |
物理学 | 1809篇 |
无线电 | 5166篇 |
出版年
2024年 | 39篇 |
2023年 | 125篇 |
2022年 | 194篇 |
2021年 | 221篇 |
2020年 | 305篇 |
2019年 | 300篇 |
2018年 | 305篇 |
2017年 | 420篇 |
2016年 | 477篇 |
2015年 | 419篇 |
2014年 | 722篇 |
2013年 | 1001篇 |
2012年 | 811篇 |
2011年 | 814篇 |
2010年 | 722篇 |
2009年 | 897篇 |
2008年 | 937篇 |
2007年 | 936篇 |
2006年 | 780篇 |
2005年 | 736篇 |
2004年 | 681篇 |
2003年 | 717篇 |
2002年 | 578篇 |
2001年 | 448篇 |
2000年 | 419篇 |
1999年 | 351篇 |
1998年 | 314篇 |
1997年 | 283篇 |
1996年 | 225篇 |
1995年 | 162篇 |
1994年 | 140篇 |
1993年 | 104篇 |
1992年 | 90篇 |
1991年 | 73篇 |
1990年 | 62篇 |
1989年 | 47篇 |
1988年 | 32篇 |
1987年 | 31篇 |
1986年 | 17篇 |
1985年 | 37篇 |
1984年 | 21篇 |
1983年 | 20篇 |
1982年 | 29篇 |
1981年 | 29篇 |
1980年 | 17篇 |
1979年 | 16篇 |
1978年 | 19篇 |
1977年 | 12篇 |
1976年 | 7篇 |
1973年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
101.
本文给出多目标规划有效解适应鞍点准则的一个新的判别法 ,它不使用凸性的几何术语及凸分析中的概念。最后给出单目标规划的一个相应的判别法 相似文献
102.
Marcos Almeida Bezerra Sérgio Mitihiro do Nascimento Maêda Eliane Padua Oliveira Maria de Fátima Batista de Carvalho Ricardo Erthal Santelli 《Spectrochimica Acta Part B: Atomic Spectroscopy》2007
In the present paper a procedure is proposed for the determination of traces of Cd, Co, Mn and Cr in petroleum industry produced water by inductively coupled plasma optical emission spectrometry. The procedure is based on cloud point extraction of these metals, as their dithizonate complexes, into the surfactant-rich phase of octylphenoxypolyethoxyethanol surfactant (Triton X-114). Extractions were carried out in solutions with salinities between 10‰ and 70‰. Since residual salinity in the surfactant-rich phase caused differences in its transport to the plasma, yttrium was used as an internal standard to correct for this effect. The simultaneous metal extraction procedure was optimized by response surface methodology using a Doehlert design and desirability function. Enhancement factors of 21, 21, 9 and 19, along with limits of quantification of 0.093, 0.20, 0.73 and 1.2 μg L− 1, and precision expressed as relative standard deviation (n = 8, 20.0 μg L− 1) of 5.8, 1.2, 1.7 and 5.7% were obtained for Cd, Co, Mn and Cr, respectively. The accuracy was evaluated by spike recovery tests on the high salinity water samples with salinity of 40 and 63‰. 相似文献
103.
Somyot Plubtieng Rattanaporn Punpaeng 《Journal of Mathematical Analysis and Applications》2007,336(1):455-469
In this paper, we introduce two iterative schemes by the general iterative method for finding a common element of the set of an equilibrium problem and the set of fixed points of a nonexpansive mapping in a Hilbert space. Then, we prove two strong convergence theorems for nonexpansive mappings to solve a unique solution of the variational inequality which is the optimality condition for the minimization problem. These results extended and improved the corresponding results of Marino and Xu [G. Marino, H.K. Xu, A general iterative method for nonexpansive mapping in Hilbert spaces, J. Math. Anal. Appl. 318 (2006) 43-52], S. Takahashi and W. Takahashi [S. Takahashi, W. Takahashi, Viscosity approximation methods for equilibrium problems and fixed point problems in Hilbert spaces, J. Math. Anal. Appl. 331 (1) (2007) 506-515], and many others. 相似文献
104.
Yu Zanping Zhou Zheyan School of Math.and Computer Science Fujian Normal University Fuzhou ) Shen Jianhe 《Annals of Differential Equations》2007,23(3):365-372
The paper aims to obtain existence and uniqueness of the solution as well as asymptotic estimate of the solution for singularly perturbed nonlinear third- order Robin boundary value problem with a turning point.In order to achieve this aim,existence and uniqueness of the solution for third-order nonlinear Robin boundary value problem is derived first based on the upper and lower solutions method under relatively weaker conditions.In this manner,the goal of this paper is gained by applying the existence and uniqueness results mentioned above. 相似文献
105.
研究了三包层WⅠ和WⅡ型单模光纤的波导色散特性。结果发现在相同条件下,三包层WⅠ和WⅡ型单模光纤零色散点的调节范围比传统的双包层W型单模光纤明显增大。详细分析了几何参量P、Q和光学参量R1、R2对单模传输时的波导色散特性和低次模截止频率的影响。所得的研究结果为获得更为理想的色散补偿、色散平坦光纤及设计新型无源光器件提供了重要的依据。计算波导色散的方法可推广到多包层光纤。 相似文献
106.
Anna Avallone 《Mathematica Slovaca》2007,57(2):129-140
We prove the existence of separating points for every countable family of nonatomic σ-additive modular measures on a σ-complete lattice ordered effect algebra.
相似文献
107.
Qinghai He 《Journal of Mathematical Analysis and Applications》2007,333(2):1070-1078
In this paper, variational conclusions of set-valued bifunctions on convex subsets of Banach spaces are investigated and several new results are obtained. The results are applied to the fixed point theory and variational inequalities. We obtain two fixed point theorems and existence theorems of solutions of variational inequalities. 相似文献
108.
109.
高阶线性微分方程的解及其解的导数的不动点 总被引:2,自引:0,他引:2
研究了复域齐次和非齐次线性微分方程的解及其解的导数的不动点与超级问题,得到了整函数系数的齐次和非齐次线性微分方程的解及其解的导数的不动点的两个结果,所得结果推广了一些相关结果. 相似文献
110.
Jiqin Deng 《Journal of Mathematical Analysis and Applications》2007,332(1):475-486
In this paper, by using the fixed point theory, under quite general conditions on the nonlinear term, we obtain an existence result of bounded positive solutions of Schrödinger equations in two-dimensional exterior domains. 相似文献