全文获取类型
收费全文 | 105440篇 |
免费 | 18119篇 |
国内免费 | 10173篇 |
专业分类
化学 | 71327篇 |
晶体学 | 1218篇 |
力学 | 6920篇 |
综合类 | 533篇 |
数学 | 11912篇 |
物理学 | 41822篇 |
出版年
2024年 | 369篇 |
2023年 | 2134篇 |
2022年 | 3647篇 |
2021年 | 3881篇 |
2020年 | 4251篇 |
2019年 | 4143篇 |
2018年 | 3551篇 |
2017年 | 3295篇 |
2016年 | 5187篇 |
2015年 | 4952篇 |
2014年 | 6027篇 |
2013年 | 7788篇 |
2012年 | 9437篇 |
2011年 | 9774篇 |
2010年 | 6458篇 |
2009年 | 6170篇 |
2008年 | 6557篇 |
2007年 | 6011篇 |
2006年 | 5504篇 |
2005年 | 4597篇 |
2004年 | 3404篇 |
2003年 | 2671篇 |
2002年 | 2416篇 |
2001年 | 1984篇 |
2000年 | 1765篇 |
1999年 | 2072篇 |
1998年 | 1848篇 |
1997年 | 1722篇 |
1996年 | 1890篇 |
1995年 | 1504篇 |
1994年 | 1459篇 |
1993年 | 1165篇 |
1992年 | 1070篇 |
1991年 | 984篇 |
1990年 | 791篇 |
1989年 | 563篇 |
1988年 | 464篇 |
1987年 | 382篇 |
1986年 | 374篇 |
1985年 | 318篇 |
1984年 | 241篇 |
1983年 | 154篇 |
1982年 | 142篇 |
1981年 | 106篇 |
1980年 | 76篇 |
1979年 | 44篇 |
1978年 | 34篇 |
1976年 | 36篇 |
1975年 | 33篇 |
1974年 | 45篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
162.
讨论了浅海中波导的声波散射问题,我们将该问题归结为一个第一类边界积分方程,利用正同化方法求解,并证明了该方法的收敛性,数值例子表明了该方法的简单与有效性。 相似文献
163.
基于无穷维空间中的生存定理,我们研究了集值映象的不动点,得到了一个新的不动点定理,推广和改进了[1]和[5]中的相应结果。 相似文献
164.
A technique for the characterization of an interior crack perpendicular to the surface of the plates is presented. A time-harmonic line load is applied on the upper surface of the plate. The scattered displacement field is calculated by using the strip element method. It is found that there are additional superimposed oscillations in the curve of the absolute values of the displacement in the region between the load and the crack. The mean value of the peaks of the additional oscillations increases with the crack length, and is less dependent on the distance from the load to the crack. The crack position is determined from the displacement distribution curve and the crack length is determined from the mean value of the peaks of the additional oscillations. Approximate polynomial formula of degree four for predicting the length of interior vertical cracks in isotropic homogeneous plates is also proposed. Numerical examples are given to demonstrate the present technique. 相似文献
165.
166.
Lizeng Wang Chengsong Ma Xiaoli Zhang Yibing Ren Yong Yu 《Fresenius' Journal of Analytical Chemistry》1995,351(7):689-691
The electrochemical behavior of the copper-tyrosine complex has been studied by linear-sweep adsorption voltammetry. In 0.02 mol/L Na2HPO4 buffer solution (pH=9.6), the complex can be adsorped on a hanging mercury drop electrode and reduced at a peak potential of about –0.42 V (vs. SCE). The secondary derivative peak height is linear proportional to the concentration of tyrosine in the range 1.0×10–7–5.0×10–5 mol/L. The detection limit is 5×10–8 mol/L.Project supported by the Provincial Science Foundation of Shandong Province 相似文献
167.
Many biological and medical studies have as a response of interest the time to occurrence of some event, such as the occurrence of a particular symptom or disease, remission, relapse, death due to some specific disease, or simply death. In this paper we study the problem of assessing the effect of potential risk factors on the outcome event of interest through a parametric or semi-parametric frailty model where the lifetimes have a reason to be considered dependent. This dependence may arise because of multiple endpoints within the same individual or because, when studying a single endpoint, there are natural groupings between study subjects. The objective of this paper is to extend both parametric and semi-parametric approaches to regression analysis in which the lifetimes of individuals in a group are effected by the same random frailty which follows a positive stable distribution. Some comparisons of the properties of this frailty distribution with other frailty distributions are made and an example which assesses the effect of a treatment in a litter-matched tumorigenesis study is presented. 相似文献
168.
169.
By constructing close-one-cochain density Ω^12n in the gauge group space we get the Wess-Zumino-Witten (WZW) effective Lagrangian on high-dimensional noncommutative space.Especially consistent anomalies derived from this WZW effective action in noncommutative four-dimensional space coincide with those obtained by L.Bonora etc.(het-th/0002210). 相似文献
170.