全文获取类型
收费全文 | 283064篇 |
免费 | 4377篇 |
国内免费 | 836篇 |
专业分类
化学 | 150274篇 |
晶体学 | 4255篇 |
力学 | 12311篇 |
综合类 | 1篇 |
数学 | 33815篇 |
物理学 | 87621篇 |
出版年
2021年 | 2134篇 |
2020年 | 2530篇 |
2019年 | 2809篇 |
2018年 | 3688篇 |
2017年 | 3457篇 |
2016年 | 5547篇 |
2015年 | 3935篇 |
2014年 | 5538篇 |
2013年 | 13281篇 |
2012年 | 11200篇 |
2011年 | 13122篇 |
2010年 | 8891篇 |
2009年 | 8435篇 |
2008年 | 11896篇 |
2007年 | 11883篇 |
2006年 | 11099篇 |
2005年 | 10142篇 |
2004年 | 9173篇 |
2003年 | 7946篇 |
2002年 | 7659篇 |
2001年 | 7836篇 |
2000年 | 6039篇 |
1999年 | 4712篇 |
1998年 | 3935篇 |
1997年 | 3818篇 |
1996年 | 3784篇 |
1995年 | 3328篇 |
1994年 | 3298篇 |
1993年 | 3415篇 |
1992年 | 3532篇 |
1991年 | 3638篇 |
1990年 | 3374篇 |
1989年 | 3308篇 |
1988年 | 3313篇 |
1987年 | 3190篇 |
1986年 | 3020篇 |
1985年 | 4169篇 |
1984年 | 4327篇 |
1983年 | 3409篇 |
1982年 | 3714篇 |
1981年 | 3620篇 |
1980年 | 3487篇 |
1979年 | 3583篇 |
1978年 | 3674篇 |
1977年 | 3557篇 |
1976年 | 3702篇 |
1975年 | 3337篇 |
1974年 | 3370篇 |
1973年 | 3400篇 |
1972年 | 2326篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
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
73.
Herrasti P. Mazarío E. Recio Francisco J. 《Journal of Solid State Electrochemistry》2021,25(1):231-236
Journal of Solid State Electrochemistry - In this work, the use of neodymium electrodes as a basis for the immobilization of magnetite nanoparticles has been carried out. The sensitivity and... 相似文献
74.
This study compares the physicochemical properties of six electrolytes comprising of three salts: LiFTFSI, NaFTFSI and KFTFSI in two solvent mixtures, the binary (3EC/7EMC) and the ternary (EC/PC/3DMC). The transport properties (conductivity, viscosity) as a function of temperature and concentration were modeled using the extended Jones-Dole-Kaminsky equation, the Arrhenius model, and the Eyring theory of transition state for activated complexes. Results are discussed in terms of ionicity, solvation shell, and cross-interactions between electrolyte components. The application of the six formulated electrolytes in symmetrical activated carbon (AC)//AC supercapacitors (SCs) was characterized by cyclic voltammetry (CV), galvanostatic cycling with potential limitation (GCPL), electrochemical impedance spectroscopy (EIS) and accelerated aging. Results revealed that the geometrical flexibility of the FTFSI anion allows it to access and diffuse easily in AC whereas its counter ions (Li+, Na+ or K+) can remain trapped in porosity. However, this drawback was partially resolved by mixing LiFTFSI and KFTFSI salts in the electrolyte. 相似文献
75.
José Luis Olloqui-Sariego Juan José Calvente Rafael Andreu 《Current Opinion in Electrochemistry》2021
Three key challenges are stimulating intensive research in the development of productive direct electron transfer mode enzyme electrodes: proper enzyme orientation, high enzyme loading, and full retention of enzyme activity. In this review, we summarize some significant advances that have been reported in the last years on the design of mesoporous and nanostructured electrodes as enzyme scaffolds and of innovative methodologies for wiring enzymes to electrodes. Particular attention is given to investigations on physical factors that determine a favorable enzyme immobilization, to provide rational guidelines for the design of productive enzymatic electrodes. Finally, some emerging trends focused on the spatial organization of either single enzymes or enzyme cascades are also briefly addressed. 相似文献
76.
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
77.
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
78.
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
79.
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
80.
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