全文获取类型
收费全文 | 488673篇 |
免费 | 4311篇 |
国内免费 | 1390篇 |
专业分类
化学 | 242150篇 |
晶体学 | 8119篇 |
力学 | 23700篇 |
综合类 | 5篇 |
数学 | 65146篇 |
物理学 | 155254篇 |
出版年
2018年 | 11631篇 |
2017年 | 12370篇 |
2016年 | 9529篇 |
2015年 | 4730篇 |
2014年 | 6294篇 |
2013年 | 17316篇 |
2012年 | 15917篇 |
2011年 | 26001篇 |
2010年 | 16938篇 |
2009年 | 16872篇 |
2008年 | 23058篇 |
2007年 | 26168篇 |
2006年 | 13373篇 |
2005年 | 18050篇 |
2004年 | 14117篇 |
2003年 | 12855篇 |
2002年 | 10882篇 |
2001年 | 11952篇 |
2000年 | 9332篇 |
1999年 | 7183篇 |
1998年 | 5926篇 |
1997年 | 5843篇 |
1996年 | 5781篇 |
1995年 | 5253篇 |
1994年 | 5124篇 |
1993年 | 5101篇 |
1992年 | 5635篇 |
1991年 | 5654篇 |
1990年 | 5417篇 |
1989年 | 5403篇 |
1988年 | 5381篇 |
1987年 | 5278篇 |
1986年 | 4956篇 |
1985年 | 6688篇 |
1984年 | 6921篇 |
1983年 | 5657篇 |
1982年 | 5934篇 |
1981年 | 5847篇 |
1980年 | 5673篇 |
1979年 | 5937篇 |
1978年 | 6275篇 |
1977年 | 5952篇 |
1976年 | 5997篇 |
1975年 | 5559篇 |
1974年 | 5570篇 |
1973年 | 5623篇 |
1972年 | 3826篇 |
1971年 | 3182篇 |
1968年 | 3415篇 |
1967年 | 3392篇 |
排序方式: 共有10000条查询结果,搜索用时 359 毫秒
31.
The health monitoring has been studied to ensure integrity of design of engine structure by detection, quantification, and prediction of damages. Early detection of faults may allow the downtime of maintenance to be rescheduled, thus preventing sudden shutdown of machines. In cylinder pressure developed, vibrations and noise emissions data provide a rich source of information about condition of engines. Monitoring of vibrations and noise emissions are novel non-intrusive methodologies for which positioning of various transducers are important issue. The presented work shows applicability of these diagnosis methodologies adopted in case of diesel engines. The effects of changing various fuel injection parameters was analyzed. Scope of using non-intrusive technique has been analyzed by changing locations of microphone. Novelty of this worklies in exploring signal processing methods for various locations around the engine test set up. Various frequency ranges of contributing noise and vibration sources were identified. Time-Frequency analysis showed the onset of various cyclic. Based on the identification of various frequency bands, it is possible to device suitable filters in order to extract more information. 相似文献
32.
Daulbaev O. Isaenko L. I. Bogdzel’ A. A. Lobanov S. I. Krinitsyn P. G. Milkov V. M. Belushkin A. V. 《Crystallography Reports》2022,67(3):464-469
Crystallography Reports - Two LiInSe2 single crystals, grown under different conditions, have been studied. Characteristics of these crystals for neutron detection have been compared using... 相似文献
33.
Vasile M. Loots H. Vercammen L. Bruggeman M. Verrezen F. 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(8):3349-3357
Journal of Radioanalytical and Nuclear Chemistry - In this paper a study for the selection of an NPE (nonylphenol ethoxylates)—free cocktail is discussed in order to be used for our routine... 相似文献
34.
Ibotov Sh. Kh. Yuldasheva N. K. Mukarramov N. I. Zakirova R. P. Gusakova S. D. 《Chemistry of Natural Compounds》2022,58(4):728-731
Chemistry of Natural Compounds - 相似文献
35.
36.
Crystallography Reports - Some questions related to the establishment, development, and prospects of physical studies using inelastic thermal-neutron scattering are briefly reviewed. The directions... 相似文献
37.
Avrutskiy V. I. Ishkhanyan A. M. Krainov V. P. 《Theoretical and Mathematical Physics》2021,208(3):1201-1206
Theoretical and Mathematical Physics - The fractional derivative method is used to take wave dispersion into account in the wave equation when describing the propagation of gravitational soliton... 相似文献
38.
S. Venkatesan S. Suresh P. Ramu M. Kandasamy J. Arumugam S. Thambidurai K.M. Prabu N. Pugazhenthiran 《印度化学会志》2022,99(5):100436
A facile biosynthesis route was followed to prepare zinc oxide nanoparticles (ZnO NPs) using Euphorbia milii (E. milii) leaf constituents. The SEM images exhibited presence of spherical ZnO NPs and the corresponding TEM images disclosed monodisperse nature of the ZnO NPs with diameter ranges between 12 and 20 nm. The Brunauer–Emmett–Teller (BET) analysis revealed that the ZnO NPs have specific surface area of 20.46 m2/g with pore diameter of 2 nm–10 nm and pore volume of 0.908 cm3/g. The EDAX spectrum exemplified the existence of Zn and O elements and non-appearance of impurities that confirmed pristine nature of the ZnO NPs. The XRD pattern indicated crystalline peaks corresponding to hexagonal wurtzite structured ZnO with an average crystallite size of 16.11 nm. The FTIR spectrum displayed strong absorption bands at 512 and 534 cm?1 related to ZnO. The photocatalytic action of ZnO NPs exhibited noteworthy degradation of methylene blue dye under natural sunlight illumination. The maximum degradation efficiency achieved was 98.17% at an illumination period of 50 min. The reusability study proved considerable photostability of the ZnO NPs during photocatalytic experiments. These findings suggest that the E. milii leaf constituents can be utilized as suitable biological source to synthesis ZnO NPs for photocatalytic applications. 相似文献
39.
Crystallography Reports - Methods of coherent X-ray diffraction imaging of the spatial structure of noncrystalline objects and nanocrystals (nanostructures) are considered. Particular attention is... 相似文献