全文获取类型
收费全文 | 2292篇 |
免费 | 147篇 |
国内免费 | 184篇 |
专业分类
化学 | 1163篇 |
晶体学 | 6篇 |
力学 | 157篇 |
综合类 | 43篇 |
数学 | 848篇 |
物理学 | 406篇 |
出版年
2024年 | 3篇 |
2023年 | 12篇 |
2022年 | 22篇 |
2021年 | 45篇 |
2020年 | 45篇 |
2019年 | 49篇 |
2018年 | 52篇 |
2017年 | 57篇 |
2016年 | 64篇 |
2015年 | 46篇 |
2014年 | 129篇 |
2013年 | 194篇 |
2012年 | 107篇 |
2011年 | 102篇 |
2010年 | 84篇 |
2009年 | 114篇 |
2008年 | 134篇 |
2007年 | 115篇 |
2006年 | 125篇 |
2005年 | 141篇 |
2004年 | 103篇 |
2003年 | 106篇 |
2002年 | 109篇 |
2001年 | 82篇 |
2000年 | 64篇 |
1999年 | 68篇 |
1998年 | 63篇 |
1997年 | 42篇 |
1996年 | 48篇 |
1995年 | 35篇 |
1994年 | 38篇 |
1993年 | 30篇 |
1992年 | 34篇 |
1991年 | 21篇 |
1990年 | 22篇 |
1989年 | 18篇 |
1988年 | 18篇 |
1987年 | 11篇 |
1986年 | 7篇 |
1985年 | 5篇 |
1984年 | 10篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1973年 | 1篇 |
排序方式: 共有2623条查询结果,搜索用时 359 毫秒
991.
S. Baron E. Liflyand U. Stadtmüller 《Journal of Mathematical Analysis and Applications》2000,250(2):226
Complementary spaces for Fourier series were introduced by G. Goes and generalized by M. Tynnov. In this paper we investigate a notion of complementary space for double Fourier series of functions of bounded variation. Various applications are given. 相似文献
992.
90年代初 ,Sony技术能源公司首先使LiCoO2 /C锂离子“摇椅”蓄电池[1]商品化 .但由于Co价格较贵 ,生产成本高以及污染环境等缺点 ,限制了Co的使用 .研究和开发用于锂离子电池作正极材料的有LiNiO2 和LiMn2 O4 .LiNiO2 的容量较高 ,毒副作用较小 ,受到人们重视 ,但是制备和纯化十分困难 .尖晶石型LiMn2 O4 [2 ,3]由于资源丰富 ,价格便宜 ,对环境污染小 ,已成为锂离子电池正极材料研究热点之一 .Li1 xMn2 O4 通常的制备方法是固相合成法 ,该法比较简单 ,但焙烧时间长、能耗高、粒度不均匀 .虽然用P… 相似文献
993.
退化时滞微分系统的通解 总被引:11,自引:0,他引:11
本文用D-逆阵给出退化滞后系统的基础解、常数交易公式与通解,确定了这类退化系统的基本理论.它将被广泛地应用于各类退化控制系统. 相似文献
994.
VISAR测速中的信号丢失及丢失条纹数的确定 总被引:5,自引:2,他引:3
论述了VISAR测速中信号频率与被测速度增量的关系和光电倍增管、数字示波器所能响应的最高速度增量。分析了信号丢失的原因,给出了丢失条纹数的确定方法。最后对VISAR应用中如何正确选择条纹常数提出了建议。 相似文献
995.
996.
Summary The CE separation of twelve nucleotides (5′-mono-, di-, triphosphates of adenosine, guanosine, cytidine and uridine) was improved
by adding cadmium ion to the ammonium citrate/citric acid buffer (pH 5, ionic strength 100 mM). Cadmium ion acts as a complexing
agent for some nucleotides (ATP, CTP, GTP, UTP, GDP). In order to accelerate the separation, the electroosmotic flow was reversed
by flushing the fused-silica capillary with 0.2 % aqueous solution of the polycationic surfactant hexadimethrine bromide.
A good separation of the twelve nucleotides studied was then achieved on a dynamically coated capillary in less than 5 min
by using an ammonium citrate/citric acid buffer (pH 5, ionic strength 100 mM) to which 2 mM cadmium ion has been added. High
peak efficiencies were obtained (210 000 theoretical plates) and the resolution between two adjacent peaks was always greater
than 1.5. 相似文献
997.
998.
This paper presents a new estimation procedure for the limit distribution of the maximum of a multivariate random sample. This procedure relies on a new and simple relationship between the copula of the underlying multivariate distribution function and the dependence function of its maximum attractor. The obtained characterization is then used to define a class of kernel-based estimates for the dependence function of the maximum attractor. The consistency and the asymptotic distribution of these estimates are considered. 相似文献
999.
Todd R. Downey Fabrice Meriaudeau Ali Passian Andrew Wig Thomas L. Ferrell 《Optics & Laser Technology》1999,31(4):273
The effect of variation of core and cladding index difference, Δn=ncore−ncladding, on allowable values for the guided mode transverse magnetic propagation constants within a step-index, multi-mode optical fiber is investigated. We use a iterative computational technique to calculate the propagation constants for modes inside and outside the core that satisfy the boundary conditions contained within the characteristic eigen-equation for the TM field components. Evidence of a strong dependence of the allowable propagation constants on changes of Δn is shown. 相似文献
1000.
Ch. Loppacher M. Bammerlin M. Guggisberg F. Battiston R. Bennewitz S. Rast A. Baratoff E. Meyer H. -J. Güntherodt 《Applied Surface Science》1999,140(3-4):287-292
This work presents constant amplitude Dynamic Force Microscopy (DFM) measurements under ultra-high vacuum conditions performed with home-built digital electronics based on the principle of phase locked loop (PLL) techniques. In DFM so-called topography is often measured in constant frequency shift (Δf) mode. This study describes the influence of phase shifts on constant Δf imaging. Therefore, phase variation experiments were acquired, leading to information about the cantilever resonance behaviour close to the surface. As sample, an evaporated thin film of NaCl on a Cu(111) substrate was chosen in order to obtain a heterogeneous system with clean Cu and NaCl areas. The atomic structure of both materials was resolved, which is the first time true atomic resolution was obtained on a metal. Large apparent topography variations are observed on this heterogeneous sample when changing the phase between the excitation and oscillation of the cantilever end. Such artefacts can be explained by comparison with phase variation experiments. 相似文献