全文获取类型
收费全文 | 17274篇 |
免费 | 1615篇 |
国内免费 | 2127篇 |
专业分类
化学 | 8437篇 |
晶体学 | 163篇 |
力学 | 2138篇 |
综合类 | 200篇 |
数学 | 5950篇 |
物理学 | 4128篇 |
出版年
2024年 | 60篇 |
2023年 | 283篇 |
2022年 | 428篇 |
2021年 | 442篇 |
2020年 | 577篇 |
2019年 | 549篇 |
2018年 | 495篇 |
2017年 | 598篇 |
2016年 | 710篇 |
2015年 | 539篇 |
2014年 | 772篇 |
2013年 | 1374篇 |
2012年 | 902篇 |
2011年 | 1066篇 |
2010年 | 912篇 |
2009年 | 1106篇 |
2008年 | 1100篇 |
2007年 | 1182篇 |
2006年 | 928篇 |
2005年 | 788篇 |
2004年 | 757篇 |
2003年 | 662篇 |
2002年 | 614篇 |
2001年 | 504篇 |
2000年 | 491篇 |
1999年 | 472篇 |
1998年 | 402篇 |
1997年 | 326篇 |
1996年 | 282篇 |
1995年 | 270篇 |
1994年 | 229篇 |
1993年 | 189篇 |
1992年 | 149篇 |
1991年 | 159篇 |
1990年 | 94篇 |
1989年 | 78篇 |
1988年 | 64篇 |
1987年 | 51篇 |
1986年 | 53篇 |
1985年 | 51篇 |
1984年 | 49篇 |
1983年 | 30篇 |
1982年 | 37篇 |
1981年 | 41篇 |
1980年 | 35篇 |
1979年 | 28篇 |
1978年 | 19篇 |
1977年 | 21篇 |
1976年 | 16篇 |
1974年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
An inverse problem of the reconstruction of the right-hand side of the Euler-Darboux equation is studied. This problem is equivalent to the Volterra integral equation of the third kind with the operator of multiplication by a smooth nonincreasing function. Numerical solution of this problem is constructed using an integral representation of the solution of the inverse problem, the regularization method, and the method of quadratures. The convergence and stability of the numerical method is proved. 相似文献
62.
本文讨论了一类Rosenbrock方法求解比例延迟微分方程,y′(t)=λy(t) μy(qt),λ,μ∈C,0 相似文献
63.
In this paper, we are concerned with the problem of stabilization for autonomous dynamical systems. We use theories in Liapunov stability and Lasalle stability theory and show that system (H) is stabilizable. 相似文献
64.
CuX(X=Al, Ga, In)分子的势能函数与稳定性的密度泛函研究 总被引:5,自引:3,他引:2
刘风丽 《原子与分子物理学报》2006,23(5):838-842
根据原子分子反应静力学原理导出了CuX(X=Al,Ga,In) 分子基态电子状态及其离解极限,并在B3LYP/LANL2DZ水平上计算了平衡几何、振动频率和解离能.利用Murrell-Sorbie 函数拟合出了解析势能函数,并计算出光谱参数和力常数.计算结果表明该分子体系是稳定存在的,其稳定性排序为 CuAl>CuGa>CuIn. 相似文献
65.
66.
CRT显示器稳定性实验研究 总被引:4,自引:1,他引:3
用屏幕色度计对一台SONY-G520显示器的显色特性进行了测量,研究了其开机稳定性和短、中、长期内的色差及色度偏差。实验结果表明,开机后,显示器的亮度Y和色度x,y分别可在2h,30min和1h达到相对稳定状态,且在达到相对稳定后,在短、中、长期内的平均色差分别为0.0611,0.1469和1.2536CIELAB色差单位;在中期内,Y,x,y,L,a,b的平均偏差分别为0.0663,0.0008,0.0015,0.0695,0.4740和0.1766。通过对显示器稳定性的测量,为在对比度敏感测量和色貌模型、图像质量、图像感知模型评价等研究领域中用显示器进行实验研究奠定了基础。 相似文献
67.
68.
Alain Adenier Eva Cabet-Deliry Sophie Griveau Florence Mercier Christine Vautrin-Ul 《Surface science》2006,600(21):4801-4812
This study investigates the spontaneous grafting of different para-substituted phenyl groups on carbon and metallic surfaces from diazonium salts solutions. Glassy carbon, nickel, zinc and iron plates were allowed to react with an acetonitrile solution of aryldiazonium tetrafluoroborate salt by simple dipping. The surfaces were characterized before and after their immersion by XPS and AFM to evidence the formation of a coating on the different materials. The results are indicative of the presence of substituted phenyl groups on all the investigated surfaces. This study also aims at correlating grafting efficiency with metal reactivities and diazonium salt electronic properties by means of AFM and FT-IRRAS. For this purpose, zinc and nickel were chosen due to their opposite reducing properties and two diazonium salts were selected with electron-donor or -withdrawing para-substituents. The results tend to indicate that redox properties of both partners (diazonium + metal) are of prime importance for grafting to occur. 相似文献
69.
CHENDAOQI 《高校应用数学学报(英文版)》1994,9(1):35-43
In this paper, the normative matrices and their double LR transformation with origin shifts are defined, and the essential relationship between the double LR transformation of a normative matrix and the QR transformation of the related symmetric tridiagonal matrix is proved. We obtain a stable double LR algorithm for double LR transformation of normative matrices and give the error analysis of our algorithm. The operation number of the stable double LR algorithm for normative matrices is only four sevenths of the rational QR algorithm for reed symmetric tridiagonal matrices. 相似文献
70.
The Randi? index R(G) of a (chemical) graph G is also called connectivity index. Hansen and Mélot [Variable neighborhood search for extremal graphs 6: analyzing bounds for the connectivity index, J. Chem. Inf. Comput. Sci. 43 (2003) 1-14] in their paper, characterized the chemical trees of given order and number of pendent vertices which have the minimum and maximum Randi? index, respectively. In this note, we point out the mistakes in the proofs of their results Theorems 8 and 10, while we still believe that the two theorems are true, and then we give their corrected proofs. 相似文献