全文获取类型
收费全文 | 305454篇 |
免费 | 4992篇 |
国内免费 | 833篇 |
专业分类
化学 | 162068篇 |
晶体学 | 4337篇 |
力学 | 12697篇 |
综合类 | 2篇 |
数学 | 39087篇 |
物理学 | 93088篇 |
出版年
2021年 | 2318篇 |
2020年 | 2820篇 |
2019年 | 3038篇 |
2018年 | 4248篇 |
2017年 | 3978篇 |
2016年 | 6406篇 |
2015年 | 4546篇 |
2014年 | 6083篇 |
2013年 | 14741篇 |
2012年 | 12393篇 |
2011年 | 14196篇 |
2010年 | 9651篇 |
2009年 | 9068篇 |
2008年 | 12792篇 |
2007年 | 12678篇 |
2006年 | 11779篇 |
2005年 | 10930篇 |
2004年 | 9848篇 |
2003年 | 8497篇 |
2002年 | 8134篇 |
2001年 | 8326篇 |
2000年 | 6527篇 |
1999年 | 5043篇 |
1998年 | 4227篇 |
1997年 | 4024篇 |
1996年 | 4084篇 |
1995年 | 3552篇 |
1994年 | 3586篇 |
1993年 | 3662篇 |
1992年 | 3812篇 |
1991年 | 3869篇 |
1990年 | 3650篇 |
1989年 | 3527篇 |
1988年 | 3534篇 |
1987年 | 3387篇 |
1986年 | 3201篇 |
1985年 | 4421篇 |
1984年 | 4562篇 |
1983年 | 3628篇 |
1982年 | 3912篇 |
1981年 | 3817篇 |
1980年 | 3651篇 |
1979年 | 3744篇 |
1978年 | 3846篇 |
1977年 | 3723篇 |
1976年 | 3876篇 |
1975年 | 3495篇 |
1974年 | 3534篇 |
1973年 | 3580篇 |
1972年 | 2440篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
In this work, the effect of various properties of materials on vacuum breakdown initiated by laser radiation is considered. Estimating calculations are performed which show that the material of the target electrode distinctly affects the minimum energy of laser radiation needed for igniting a vacuum spark. The experimental studies carried out confirm the estimating calculations, and a number of materials are revealed which can be arranged in order of increase in the energy needed for the formation of breakdown in vacuum by the impact of a laser pulse. 相似文献
82.
83.
Dapeng Liu Binod R. Giri Milán Szőri Béla Viskolcz Et-touhami Es-sebbar Aamir Farooq 《Proceedings of the Combustion Institute》2021,38(1):967-976
NOx mitigation is a central focus of combustion technologies with increasingly stringent emission regulations. NOx can also enhance the autoignition of hydrocarbon fuels and can promote soot oxidation. The reaction between allyl radical (C3H5) and NOx plays an important role in the oxidation kinetics of propene. In this work, we measured the absolute rate coefficients for the redox reaction between C3H5 and NOx over the temperature range of 1000–1252 K and pressure range of 1.5–5.0 bar using a shock tube and UV laser absorption technique. We produced C3H5 by shock heating of C3H5I behind reflected shock waves. Using a Ti:Sapphire laser system with frequency quadrupling, we monitored the kinetics of C3H5 at 220 nm. Unlike low-temperature chemistry, the two target reactions, C3H5 + NO → products (R1) and C3H5 + NO2 → products (R2), exhibited a strong positive temperature dependence for this radical-radical type reaction. However, these reactions did not show any pressure dependence over the pressure range of 1.5–5.0 bar, indicating that the measured rate coefficients are close to the high-pressure limit. The measured values of the rate coefficients resulted in the following Arrhenius expressions (in unit of cm3/molecule/s):To our knowledge, these are the first high-temperature measurements of allyl + NOx reactions. The reported data will be highly useful in understanding the interaction of NOx with resonantly stabilized radicals as well as the mutual sensitization effect of NOx on hydrocarbon fuels. 相似文献
84.
Algebras and Representation Theory - We introduce and study the category of twisted modules over a triangular differential graded bocs. We show that in this category idempotents split, that it... 相似文献
85.
Annals of Operations Research - The vehicle routing problem is a traditional combinatorial problem with practical relevance for a wide range of industries. In the literature, several specificities... 相似文献
86.
JETP Letters - One of the main features of the dusty plasma compared to the conventional plasma (without charged dust particles is anomalous dissipation that is caused by the charging of dust... 相似文献
87.
Kozetozhets I. V. Panasyuk G. P. Semenov E. A. Buzanov G. A. Avdeeva V. V. Danchevskaya M. N. Tsvetov N. S. Shapovalov S. S. Vasilev M. G. 《Russian Journal of General Chemistry》2022,91(1):S98-S105
Russian Journal of General Chemistry - Highly dispersed CaO has been synthesized by heating an aqueous solution of calcium nitrate and D-glucose up to 800°C. Calcium oxide is formed with an... 相似文献
88.
Avramenko Andriy A. Shevchuk Igor V. Dmitrenko Nataliia P. Skitsko Ivan F. 《Journal of Thermal Analysis and Calorimetry》2022,147(22):12709-12719
Journal of Thermal Analysis and Calorimetry - The paper focuses on the analytical analysis of the propagation of a normal shock wave in an adiabatic gas flow with nanoparticles. A modified... 相似文献
89.
Mathematical Notes - 相似文献
90.
Tagouegni Senghor Fotsa-Ngaffo Fernande Kenfack-Jiotsa Aurélien 《Optical and Quantum Electronics》2022,54(3):1-57
Optical and Quantum Electronics - In the past few decades, the academic research and industrial synergy is dramatically accelerating to conceptualize high data rate services. The congestion in the... 相似文献