全文获取类型
收费全文 | 9238篇 |
免费 | 703篇 |
国内免费 | 1013篇 |
专业分类
化学 | 6232篇 |
晶体学 | 79篇 |
力学 | 326篇 |
综合类 | 45篇 |
数学 | 121篇 |
物理学 | 4151篇 |
出版年
2024年 | 13篇 |
2023年 | 193篇 |
2022年 | 262篇 |
2021年 | 265篇 |
2020年 | 337篇 |
2019年 | 299篇 |
2018年 | 226篇 |
2017年 | 364篇 |
2016年 | 435篇 |
2015年 | 420篇 |
2014年 | 518篇 |
2013年 | 562篇 |
2012年 | 583篇 |
2011年 | 672篇 |
2010年 | 540篇 |
2009年 | 619篇 |
2008年 | 588篇 |
2007年 | 623篇 |
2006年 | 469篇 |
2005年 | 392篇 |
2004年 | 406篇 |
2003年 | 326篇 |
2002年 | 267篇 |
2001年 | 178篇 |
2000年 | 187篇 |
1999年 | 172篇 |
1998年 | 179篇 |
1997年 | 145篇 |
1996年 | 100篇 |
1995年 | 94篇 |
1994年 | 87篇 |
1993年 | 67篇 |
1992年 | 59篇 |
1991年 | 65篇 |
1990年 | 39篇 |
1989年 | 27篇 |
1988年 | 23篇 |
1987年 | 12篇 |
1986年 | 18篇 |
1985年 | 11篇 |
1984年 | 11篇 |
1983年 | 7篇 |
1982年 | 11篇 |
1981年 | 19篇 |
1980年 | 12篇 |
1979年 | 7篇 |
1978年 | 11篇 |
1977年 | 6篇 |
1976年 | 9篇 |
1974年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
51.
Two types of optical current transducers (OCTs) have a bulk Faraday sensor inserted into the gap of an iron core and a porcelain
insulator with optical fiber. The sensor consists of Bi12SiO20 (BSO) single crystal, a polarizer, and an analyzer. The OCTs satisfied the target performance requirement for fault location
and metering and demonstrated maintained performance at some power utilities in Japan and the US. We have developed a fault
location system that immediately detects the fault current with the OCTs, there by locating the fault section. The OCT can
easily replace the existing support insulators for the disconnecting switch without any modifications to structure height
or bus-bar. For metering requiring 0.3% class accuracy, use of a BSO with right optical rotatory power combined with BSO with
left optical rotatory power results in a Faraday sensor with improved temperature characteristics. The OCT demonstrated 0.3%
class accuracy for metering described in the current transformer Specifications of IEEE C57–13, 1993. 相似文献
52.
光纤液位传感器检测原理探讨 总被引:1,自引:0,他引:1
叙述光纤液位传感器在贮油罐中的应用,提出实验所采用的方案。推导出液面高度公式,比较实现检测的两种电路的优缺点,同时对实验精度和测量范围进行了讨论。 相似文献
53.
The method of demodulation with two parallel matched fiber Bragg gratings( FBGs)system is introduced to enlarge the range of strain that can be detected by the FBG sensor system. 相似文献
54.
首先将无线传感器网络的路由问题转化成求解最小Steiner树问题,然后给出了求解无线传感器网络路由的蚁群优化算法,并对算法的收敛性进行了证明.最后对找到最优解后信息素值的变化进行了分析.即在限制信息素取值的条件下,当迭代次数充分大时,该算法能以任意接近于1的概率找到最优解,并且当最优解找到后,最优树边上的信息素单调增加,而最优解以外边上的信息素在有限步达到最小值. 相似文献
55.
56.
57.
Chenghang Wang 《Applied Surface Science》2006,253(4):2282-2288
In this paper, thin films of titanium oxide imprinted with O,O-dimethyl-(2,4-dichlorophenoxyacetoxyl)(3′-nitrobenyl) methinephosphonate (Phi-NO2) were prepared via liquid phase deposition (LPD) method on a glassy carbon electrode. The imprinted molecular in the films was removed by treatment with immersion in CH2Cl2. X-ray diffraction (XRD) and electrochemical methods were introduced to show the evidence of the molecular imprinting phenomenon. It was also found that the recognition ability of the sensor depended on the substituents associated with tridimensional structures of the nitro-compounds. Under the optimized condition, the sensor showed better sensitivity, selectivity and reproducibility to the imprinted molecule and the linear relationship between the current and the concentration of analyte in the range of 0.1-50 μM was obtained. LPD proved to be a powerful method for imprinting titanium oxide thin sense films. 相似文献
58.
We use the PCP-SAFT equation of state, which is of the Van der Waals type and has a sound physical basis, to predict mixture properties, such as vapor–liquid and liquid–liquid equilibria, as well as excess enthalpies. We use molecular properties, such as dipole moment, quadrupole moment, polarizability and dispersion interaction coefficients, that have been determined quantum mechanically in Part I of this publication and adjust the remaining three pure compound parameters to pure compound data. We finally present a new combination rule for the dispersion energy parameter ? that is based on the quantum mechanically determined data. The predictions based on quantum mechanically determined pure compound properties along with the new combination rule show an improved performance compared to the original PCP-SAFT combination rule. 相似文献
59.
60.
本文介绍了利用喷油脉宽大小的变化来分析电控发动机电控系统、燃油供给等系统故障的一种方法,在汽车故障检测与诊断中有着广泛的应用。 相似文献