全文获取类型
收费全文 | 34282篇 |
免费 | 4953篇 |
国内免费 | 4495篇 |
专业分类
化学 | 25358篇 |
晶体学 | 526篇 |
力学 | 1898篇 |
综合类 | 416篇 |
数学 | 3988篇 |
物理学 | 11544篇 |
出版年
2024年 | 44篇 |
2023年 | 429篇 |
2022年 | 894篇 |
2021年 | 963篇 |
2020年 | 1076篇 |
2019年 | 1146篇 |
2018年 | 955篇 |
2017年 | 972篇 |
2016年 | 1504篇 |
2015年 | 1492篇 |
2014年 | 1897篇 |
2013年 | 2498篇 |
2012年 | 2904篇 |
2011年 | 3136篇 |
2010年 | 2306篇 |
2009年 | 2201篇 |
2008年 | 2497篇 |
2007年 | 2199篇 |
2006年 | 2130篇 |
2005年 | 1906篇 |
2004年 | 1548篇 |
2003年 | 1289篇 |
2002年 | 1498篇 |
2001年 | 1021篇 |
2000年 | 895篇 |
1999年 | 689篇 |
1998年 | 494篇 |
1997年 | 412篇 |
1996年 | 395篇 |
1995年 | 333篇 |
1994年 | 278篇 |
1993年 | 251篇 |
1992年 | 227篇 |
1991年 | 198篇 |
1990年 | 175篇 |
1989年 | 156篇 |
1988年 | 134篇 |
1987年 | 88篇 |
1986年 | 84篇 |
1985年 | 88篇 |
1984年 | 51篇 |
1983年 | 43篇 |
1982年 | 32篇 |
1981年 | 30篇 |
1980年 | 33篇 |
1979年 | 24篇 |
1978年 | 31篇 |
1977年 | 13篇 |
1976年 | 13篇 |
1974年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
TieYong YangGuangjun 《分析论及其应用》2004,20(1):58-68
In this paper, we construct some continuous but non-differentiable functions defined by quinary decimal, that are Kiesswetter-like functions. We discuss their properties, then investigate the Hausdorff dimensions of graphs of these functions and give a detailed proof. 相似文献
132.
A novel measurement method of temperature based on the phenomena that the phase difference between principle polarization states in the optical retarder is function of temperature is described. The polarization state of optical beam is changed as it passes through the optical retarder, which depends on the temperature. The temperature of optical retarder is determined by comparison of the power difference between principal polarization states. We demonstrate successfully the temperature measurement by using a polarization maintaining fiber as the optical retarder. With a 100 mm length of the fiber optic retarder, the change rate of phase difference on temperature was 0.236 rad/°C and the measurement error was ±0.038°C over the temperature range of −2.6 – +3.4°C. With a 11.5 mm length of the fiber optic retarder, the change rate of phase difference on temperature was 0.021 rad/°C and the measurement error was ±0.79°C over the temperature range of −8.5 – +86.5°C. 相似文献
133.
具有种内互惠作用的Lotka-Volterra互惠共存模型 总被引:1,自引:0,他引:1
对具有种内互惠作用的Lotka-Volterra互惠共存模型进行了完整的全局分析,得到了一些新的结果。 相似文献
134.
A periodic one-dimensional four-state hopping model is proposed. In the model, the substeps betweenarbitrary adjacent states are unequal, and an explicit solution of the master equation is first obtained for the probabilitydistribution as a function of the time and position for any initial distribution with all the transients included. Next, thetransient behaviors in the initial period of time and the characteristic time to reach the steady state for the molecularmotor are discussed. Finally, we compare the steady state results to experiments and illustrate qualitatively the kineticbehaviors of a molecular motor under external load F. 相似文献
135.
This paper is to investigate the approximate confidence limits of the reliability performances (such as failure rate, reliability function and average life) for a cold standby series system. The Bayesian approximate upper confidence limit of failure rate is obtained firstly, and next Bayesian approximate lower confidence limits for reliability function and average life are presented. The expressions for calculating Bayesian lower confidence limits of the reliability function and average life are also obtained, and an illustrative example is examined numerically by means of the Monte-Carlo simulation. Finally, the accuracy of confidence limits is discussed. 相似文献
136.
Jin Cheng Ching-Lung Lin Gen Nakamura 《Proceedings of the American Mathematical Society》2005,133(8):2359-2367
In this paper we prove the following kind of unique continuation property. That is, the zero on each geodesic of the solution in a real analytic hypersurface for second order anisotropic hyperbolic systems with real analytic coefficients can be continued along this curve.
137.
138.
In this paper, we exhibit a unified treatment of the mixed initial boundary value problem for second order (in time) parabolic linear differential equations in Banach spaces, whose boundary conditions are of a dynamical nature. Results regarding existence, uniqueness, continuous dependence (on initial data) and regularity of classical and strict solutions are established. Moreover, several examples are given as samples for possible applications.
139.
用密度泛函B3LYP/ 6 3 1G(d)方法 ,对质子化丙酮分子团簇 (CH3COCH3) nH+ (n =1~ 7)弱相互作用体系进行了全自由度能量梯度优化 ,得到了该系列团簇的稳定结构及其对应的体系能量 .通过对构型的分析得出了质子化丙酮分子团簇 (CH3COCH3) nH+ (n =1~ 7)的生长规律 .计算了中性丙酮分子团簇体系的质子亲合能并总结出其变化趋势 .分析讨论了质子化团簇的红外振动光谱 ,发现质子化团簇的振动光谱普遍较中性环型团簇的振动光谱复杂 ,最强的振动峰来源于质子在溶剂壳中两个氧原子之间的振动 ,而且随着团簇尺寸的增加羰基的伸缩振动峰的数目也随之增多 相似文献
140.
Yong Lee Kazuhiko Hosomi Hiroyuki Uchiyama Toshio Katsuyama Shinya Kominami Tomoyoshi Mishima 《Optical Review》2003,10(1):38-42
An InGaAsP slab-type asymmetric-coupled-waveguide-based dispersion compensator with a mode selector has been designed and fabricated. The mode selector is necessary to select either a symmetric [with a positive group-velocity dispersion (GVD)] or antisymmetric (with a negative GVD) supermode. These supermodes exist simultaneously in the dispersion-compensation region of the device. Pulse-compression experiments were used to test the dispersion compensator, evaluating the function of the mode selector. A theoretical study of the experimental results shows that the mode selector obtains a very strong selectivity (nearly 100%) for the antisymmetric supermode. 相似文献