全文获取类型
收费全文 | 9926篇 |
免费 | 1394篇 |
国内免费 | 834篇 |
专业分类
化学 | 2547篇 |
晶体学 | 121篇 |
力学 | 1576篇 |
综合类 | 252篇 |
数学 | 4013篇 |
物理学 | 3645篇 |
出版年
2024年 | 21篇 |
2023年 | 101篇 |
2022年 | 268篇 |
2021年 | 294篇 |
2020年 | 308篇 |
2019年 | 266篇 |
2018年 | 273篇 |
2017年 | 361篇 |
2016年 | 428篇 |
2015年 | 334篇 |
2014年 | 547篇 |
2013年 | 766篇 |
2012年 | 538篇 |
2011年 | 622篇 |
2010年 | 510篇 |
2009年 | 604篇 |
2008年 | 624篇 |
2007年 | 582篇 |
2006年 | 592篇 |
2005年 | 548篇 |
2004年 | 438篇 |
2003年 | 420篇 |
2002年 | 355篇 |
2001年 | 302篇 |
2000年 | 300篇 |
1999年 | 247篇 |
1998年 | 214篇 |
1997年 | 197篇 |
1996年 | 186篇 |
1995年 | 177篇 |
1994年 | 114篇 |
1993年 | 91篇 |
1992年 | 77篇 |
1991年 | 57篇 |
1990年 | 65篇 |
1989年 | 52篇 |
1988年 | 46篇 |
1987年 | 28篇 |
1986年 | 29篇 |
1985年 | 37篇 |
1984年 | 39篇 |
1983年 | 7篇 |
1982年 | 27篇 |
1981年 | 15篇 |
1980年 | 4篇 |
1979年 | 14篇 |
1978年 | 5篇 |
1976年 | 4篇 |
1959年 | 4篇 |
1957年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Yingchun Wu Haipeng Li Xuecheng Wu Gérard Gréhan Lutz Mädler Cyril Crua 《Proceedings of the Combustion Institute》2019,37(3):3211-3218
Droplet evaporation characterization, although of great significance, is still challenging. The recently developed phase rainbow refractometry (PRR) is proposed as an approach to measuring the droplet temperature, size as well as evaporation rate simultaneously, and is applied to a single flowing n-heptane droplet produced by a droplet-on-demand generator. The changes of droplet temperature and evaporation rate after a transient spark heating are reflected in the time-resolved PRR image. Results show that droplet evaporation rate increases with temperature, from ?1.28 m2/s at atmospheric 293 K to a range of (?1.5, ?8) m2/s when heated to (294, 315) K, agreeing well with the Maxwell and Stefan–Fuchs model predictions. Uncertainty analysis suggests that the main source is the indeterminate gradient inside droplet, resulting in an underestimation of droplet temperature and evaporation rate. With the demonstration on simultaneous measurements of droplet refractive index as well as droplet transient and local evaporation rate in this work, PRR is a promising tool to investigate single droplet evaporation in real engine conditions. 相似文献
5.
《Physics letters. A》2019,383(17):2090-2092
In this paper, we have used Monte Carlo (MC) method to simulate and study the temperature and doping effects on the electric conductivity of fullerene (C60). The results show that the band gap has reduced by the doping and the charge carrier transport is facilitated from valence band to conduction band by the temperature where is touched a 300 K. In this case, the conductivity reached a value of . The electric conductivity of C60 can increase by the triphenylmethane dye crystal violet (CV) alkali metal to reach at 303 K. Our results of MC simulation have a good agreement with those extracted from literature [10], [33]. 相似文献
6.
In this paper, we consider a viscoelastic wave equation of variable coefficients in the presence of past history with nonlinear damping and delay in the internal feedback and dynamic boundary conditions. Under suitable assumptions, we establish an explicit and general decay rate result without imposing restrictive assumption on the behavior of the relaxation function at infinity by Riemannian geometry method and Lyapunov functional method. 相似文献
7.
本文是文[1-7]的继续,研究变权综合问题,从确定变权的经验公式入手引出了变权原理,给出了变权的公理化定义,讨论了与之有关的均衡函数及其梯度向量。 相似文献
8.
四气门发动机可变涡流稀薄燃烧特性研究 总被引:1,自引:0,他引:1
本文研究了可变涡流对四气门发动机稀薄燃烧特性的影响情况。在稀薄燃烧情况下,发动机负荷大小对CO和HC排放的影响不大,对NOx排放的影响主要表现在对13~17空燃比范围内NOx排放的影响,负荷越大,NOx排放越大;对空燃比小于13或大于17以后的NOx排放影响较小。阀片位置对发动机排放特性的影响较小,对发动机的燃油经济性存在一定影响,这是因为不同阀片位置的进气涡流比不同所致,同时也表明较强的涡流运动对燃油经济性更有利。涡流运动在不同转速条件下对发动机燃油经济性的影响情况不同,它更有利于改善低速条件下的燃油经济性。 相似文献
9.
The large deviation principle (LDP) which has been effectively used in queueing analysis is the sample path LDP, the LDP in a function space endowed with the uniform topology. Chang [5] has shown that in the discrete-time G/D/1 queueing system under the FIFO discipline, the departure process satisfies the sample path LDP if so does the arrival process. In this paper, we consider arrival processes satisfying the LDP in a space of measures endowed with the weak* topology (Lynch and Sethuraman [12]) which holds under a weaker condition. It is shown that in the queueing system mentioned above, the departure processes still satisfies the sample path LDP. Our result thus covers arrival processes which can be ruled out in the work of Chang [5]. The result is then applied to obtain the exponential decay rate of the queue length probability in an intree network as was obtained by Chang [5], who considered the arrival process satisfying the sample path LDP. 相似文献
10.
浅析二阶齐次线性变系数微分方程的一个可积类型 总被引:1,自引:0,他引:1
姬志飞 《应用数学与计算数学学报》2006,20(1):125-128
本文讨论了二阶齐次线性变系数微分方程的特殊形式,给出了这种微分方程的一个可积类型. 相似文献