全文获取类型
收费全文 | 436篇 |
免费 | 11篇 |
国内免费 | 4篇 |
专业分类
化学 | 236篇 |
晶体学 | 3篇 |
力学 | 4篇 |
数学 | 39篇 |
物理学 | 169篇 |
出版年
2024年 | 3篇 |
2023年 | 3篇 |
2022年 | 20篇 |
2021年 | 8篇 |
2020年 | 9篇 |
2019年 | 15篇 |
2018年 | 11篇 |
2017年 | 14篇 |
2016年 | 21篇 |
2015年 | 8篇 |
2014年 | 17篇 |
2013年 | 37篇 |
2012年 | 25篇 |
2011年 | 38篇 |
2010年 | 24篇 |
2009年 | 16篇 |
2008年 | 23篇 |
2007年 | 10篇 |
2006年 | 10篇 |
2005年 | 7篇 |
2004年 | 6篇 |
2003年 | 10篇 |
2002年 | 5篇 |
2001年 | 8篇 |
2000年 | 4篇 |
1999年 | 6篇 |
1998年 | 5篇 |
1997年 | 7篇 |
1996年 | 5篇 |
1995年 | 8篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 7篇 |
1991年 | 2篇 |
1990年 | 6篇 |
1988年 | 2篇 |
1987年 | 8篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1977年 | 3篇 |
1974年 | 2篇 |
1971年 | 1篇 |
1970年 | 2篇 |
1968年 | 1篇 |
1957年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有451条查询结果,搜索用时 0 毫秒
91.
D. T. Khathing S. P. Tripathy R. Mishra B. K. Verma K. K. Dwivedi 《Radiation measurements》2001,34(1-6):305-308
Heavy ion range and energy-loss data provide useful information for designing several nuclear physics experiments where the polymers employed find their use as absorber, in chamber windows and target backings. In the present work, the range and energy-loss rate of 118 MeV 28Si in LR-115 (cellulose nitrate) and polypropylene (PP) have been calculated by track technique where polyallyldiglycol carbonate was used as a backing detector. The mean range of 28Si in LR-115 has been calculated to be 59.4±2 μm and that in PP is calculated to be 74.9±2 μm. The experimentally evaluated range values are in agreement with the theoretical range values derived from some computer codes. The Bragg peak has also been obtained at 1.1 MeV/nucleon for 28Si in both LR-115 and PP. 相似文献
92.
High performance radar transparent materials (RTMs) are important materials for the fabrication of radomes, nosecones, etc. of high velocity aerospace vehicles. RTMs with good mechanical performance and temperature capability are required for such applications. Toward this, fabric reinforced nano‐reinforced matrix composites (FRNCs), using reinforcing E‐glass fabric in Cloisite 30B reinforced polyetherimide (PEI) nanocomposite matrix (GNRPEI), was prepared. The properties of GNRPEI were evaluated and compared with E‐glass fabric reinforced PEI composites (GRPEI) with special reference to their radar transparent character for aerospace applications. Tensile and flexural properties along with interlaminar shear strength of GRPEI were observed to be lower than those of GNRPEI. Thermal behavior of both the composites was similar in differential scanning calorimetry and thermal gravimetric analysis. But, in dynamic mechanical analysis, an increase in storage modulus and decrease in loss tangent were observed in GNRPEI compared to GRPEI. The values of dielectric constant and loss tangent of GNRPEI were lesser than those of GRPEI, but no significant difference was observed in the values of transmission and reflection losses for both the composites at 8–12 GHz frequency. FRNCs, based on organoclay reinforced PEI matrix, hold good promise as high performance RTMs. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
93.
94.
95.
Anjaiah Aitha Satyanarayana Yennam Manoranjan Behera Jaya Shree Anireddy 《Tetrahedron letters》2017,58(6):578-581
The reaction of 1,3,4-oxathiazol-2-one derivative with 2-arylidene-1,3-indandione to furnish novel spiroindene-1,3-dione isothiazoline derivatives by Michael/1,3-dipolar [3+2]-cycloaddition reaction was investigated. The key 1,3-dipolar cycloaddition reaction step was examined in toluene solvent at reflux temperature to obtain mixture of two regioisomers (6a and 6b – 14a and 14b) and single isomers (15–20). The scope of this new reaction was demonstrated with many examples with high reactivity and yields. 相似文献
96.
D. Sinha G.K. Sarker S. Ghosh A. Kulshreshtha K.K. Dwivedi D. Fink 《Radiation measurements》1998,29(6):599-604
Photon induced modifications in Triafol-TN and Triafol-BN polymers have been studied in the dose range of 101–106 Gy at room temperature using a 60Co source. To monitor the chemical and structural changes induced by gamma rays, UV, IR, and ESR studies were carried out. Thermal studies were also conducted for understanding the effects of gamma irradiations on these polymers. Variation of track etching characteristics and activation energy for bulk etching have been studied at different gamma rays doses. The experimental results are presented and discussed. 相似文献
97.
Dev Raj Alok Kumar Rohit Kumar Singh Abhishek Singh Bhadouria A.S.K. Sinha Deepak Dwivedi 《Current Opinion in Electrochemistry》2022
As the application of electrocatalyst continues to expand, envisaging the hidden mechanisms occurring at various length scale affecting the catalytic efficiency became important. To enhance the stability of electrocatalyst and reduce the cost, it is of paramount importance to reveal the active site's dynamics (using in situ techniques for getting the real-time information) which directly affect the reactions such as oxygen evolution reaction, hydrogen evolution reaction, and so on. Since such reactions are crucial for many engineering and scientific applications, in situ characterization techniques are required, which could capture such reactions happening at a different length and time scale. This article analyzes the recent progress made in the field of electrocatalyst's characterization using in situ neutron techniques. The article also paves the future path and has delineated the future challenges involved in multiscale correlative techniques (e.g., neutron techniques in the combination of synchrotron or microscopic techniques) used for getting the multiscale (atomic to micrometer range) mechanistic information about the electrocatalyst's working and degradation. 相似文献
98.
In this paper global asymptotic stability and asymptotic behaviour of solutions of nonlinear delay difference equations has been studied and a few sets of sufficient conditions for global asymptotic stability are derived. 相似文献
99.
In recent years, angular and linear phenoxazines and their derivatives and polymers have attracted much attention due to their great pharmacological and industrial utility. So it becomes imperative to review the work done in this area more frequently. Therefore, various synthetic routes for phenoxazines are reviewed here comprehensively. 相似文献
100.
Considering the Boltzmann response of the plasma ions and electrons and inertial dynamics of the charged dust grains, the
possibility of very weak compressive soliton near the continuum limit of the dust population has been inferred. It is concluded
that the behaviour of such coherent structures could be well described by the numerical analysis of the derived nonlinear
classical energy integral equation for bounded solutions. These seem to be higher order dispersive structures within acoustic
limit of the nonlinear turbulence. It is observed that the dust density enhancement beyond the continuum threshold causes
regular increment in width and amplitude of the soliton structures. It is found that the soliton amplitude sensitively depends
on the massive impurity’s population. These coherent structures could be visualized as weakly charged solitary dust clouds
of finite extension (∼ plasma Debye length) within Boltzmann environment of plasma particles in their local surroundings.
The seeding mechanism of such clouds may be attributed to some plasma instabilities driven by either internal or external
free energy sources. Numerical analysis of the problem concludes that the experimental observations of such clouds could be
possible in low density plasma regime. It is deduced that for plasma density ∼ 106 cm-3 at temperatures of a few electron volts and for micron to l0nm sized dust grains, the observation of such structures could
be possible within wide range variability of the dust population density. 相似文献