全文获取类型
收费全文 | 706篇 |
免费 | 35篇 |
国内免费 | 7篇 |
专业分类
化学 | 415篇 |
晶体学 | 8篇 |
力学 | 57篇 |
数学 | 139篇 |
物理学 | 129篇 |
出版年
2023年 | 5篇 |
2022年 | 12篇 |
2021年 | 23篇 |
2020年 | 27篇 |
2019年 | 28篇 |
2018年 | 43篇 |
2017年 | 29篇 |
2016年 | 66篇 |
2015年 | 23篇 |
2014年 | 53篇 |
2013年 | 85篇 |
2012年 | 52篇 |
2011年 | 63篇 |
2010年 | 37篇 |
2009年 | 34篇 |
2008年 | 33篇 |
2007年 | 35篇 |
2006年 | 24篇 |
2005年 | 17篇 |
2004年 | 15篇 |
2003年 | 7篇 |
2002年 | 8篇 |
2001年 | 7篇 |
2000年 | 1篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1996年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1988年 | 1篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1978年 | 1篇 |
排序方式: 共有748条查询结果,搜索用时 46 毫秒
11.
12.
Thermodynamic simulation of performance of a dual cycle with stroke length and volumetric efficiency
This article presents finite-time thermodynamics analysis of an irreversible air standard dual cycle. An irreversible dual cycle model which is more close to practice is established. In this model, the effects of stroke length and volume efficiency by considering the nonlinear relation between the specific heats of working fluid and its temperature, the frictional loss, the internal irreversibility, and heat transfer loss are analyzed. The results show that if compression ratio is less than certain value, the power output increases with increasing stroke length, while if compression ratio exceeds certain value, the power output first increases and then starts to decrease with increasing stroke length. With further increase in compression ratio, the increase of stroke length results in decreasing the power output. The results also show that, throughout the compression ratio range, the power output increases with the increasing volumetric efficiency. The results obtained in this study are of importance to provide good guidance for performance evaluation and improvement of practical internal combustion engines. 相似文献
13.
14.
Let G be a locally compact abelian group with a fixed Haar measure and ω be a weight on G. For 1 < p < ∞, we study uniqueness of uniform and C*-norm properties of the invariant weighted algebra L p (G, ω). 相似文献
15.
This paper derived single-valued neutrosophic graphs from single-valued neutrosophic hypergraphs via strong equivalence relation. We show that any weak single-valued neutrosophic graph is a derived single-valued neutrosophic graph and any linear weak single-valued neutrosophic tree is an extendable linear single-valued neutrosophic tree. 相似文献
16.
Application of a dispersive micro‐solid‐phase extraction method for pre‐concentration and ultra‐trace determination of cadmium ions in water and biological samples
下载免费PDF全文
![点击此处可从《应用有机金属化学》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Mohammad Behbahani Ali Veisi Fariborz Omidi Aminreza Noghrehabadi Ali Esrafili Mohammad Hossein Ebrahimi 《应用有机金属化学》2018,32(3)
A method for the trace determination of cadmium ions in water, human urine and human blood serum samples using ultrasonic‐assisted dispersive micro‐solid‐phase extraction (UA‐D‐μSPE) was developed. Silica‐coated magnetic nanoparticles were coated with polythiophene, and the resulting sorbent was characterized using thermogravimetry, differential thermal analysis, scanning electron microscopy, Fourier transform infrared spectrometry and X‐ray diffraction. Following UA‐D‐μSPE, cadmium ions were quantified using graphite furnace atomic absorption spectrometry. A Box–Behnken design was used for optimization of important sorption and desorption parameters in UA‐D‐μSPE: in the sorption step, pH of solution, sorption amount and sonication time for sorption; in the desorption step, concentration of eluent, volume of eluent and sonication time. The optimum conditions for the method were: pH of solution, 7.5; sonication time for sorption, 3 min; sorption amount, 35 mg; type and concentration of eluent, HCl and 1.1 mol l?1; volume of eluent, 360 μl; sonication time for desorption, 110 s. Under the optimized conditions the limit of detection and relative standard deviation for the detection of cadmium ions by UA‐D‐μSPE were found to be 0.8 ng l?1 and <6%, respectively. 相似文献
17.
18.
19.
Structural Chemistry - Quantum chemical study of the nature of interactions between the boraphosphinine (BP) and alumaphosphinine (AlP) with some of the alkali metal cations (Li+, Na+, K+) and... 相似文献
20.
Structural Chemistry - Ab initio calculations have been performed to study the complexes between the noble gas elements (Ae = Ne, Ar, Kr) with a series of benzene isoelectronic heterocyclic... 相似文献