全文获取类型
收费全文 | 317850篇 |
免费 | 4523篇 |
国内免费 | 1171篇 |
专业分类
化学 | 173429篇 |
晶体学 | 4481篇 |
力学 | 13164篇 |
综合类 | 17篇 |
数学 | 36781篇 |
物理学 | 95672篇 |
出版年
2020年 | 2053篇 |
2019年 | 2017篇 |
2018年 | 2033篇 |
2017年 | 1937篇 |
2016年 | 3978篇 |
2015年 | 3351篇 |
2014年 | 4574篇 |
2013年 | 14216篇 |
2012年 | 11003篇 |
2011年 | 13681篇 |
2010年 | 8462篇 |
2009年 | 8405篇 |
2008年 | 12590篇 |
2007年 | 12809篇 |
2006年 | 12441篇 |
2005年 | 11386篇 |
2004年 | 10209篇 |
2003年 | 9007篇 |
2002年 | 8841篇 |
2001年 | 10189篇 |
2000年 | 7809篇 |
1999年 | 6168篇 |
1998年 | 4936篇 |
1997年 | 4769篇 |
1996年 | 4811篇 |
1995年 | 4411篇 |
1994年 | 4162篇 |
1993年 | 3990篇 |
1992年 | 4470篇 |
1991年 | 4320篇 |
1990年 | 4036篇 |
1989年 | 3850篇 |
1988年 | 4144篇 |
1987年 | 3809篇 |
1986年 | 3696篇 |
1985年 | 5339篇 |
1984年 | 5422篇 |
1983年 | 4390篇 |
1982年 | 4778篇 |
1981年 | 4819篇 |
1980年 | 4567篇 |
1979年 | 4699篇 |
1978年 | 4692篇 |
1977年 | 4674篇 |
1976年 | 4616篇 |
1975年 | 4520篇 |
1974年 | 4371篇 |
1973年 | 4533篇 |
1972年 | 2579篇 |
1971年 | 1885篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Yang T. L. Kao C. L. Kuo C. E. Yeh H. C. Li W. J. Li H. T. Chen C. Y. 《Chemistry of Natural Compounds》2022,58(5):825-827
Chemistry of Natural Compounds - A novel bibenzyl derivative, hydrangchinenin (1), was isolated from the stems of Hydrangea chinensis Maxim. (Hydrangeaceae). Its structure was determined on the... 相似文献
2.
Experimental Mechanics - Temperature gradients significantly affect the material fatigue process. A reliable and robust test procedure is needed for quantifying the effects of temperature gradients... 相似文献
3.
Machado J. A. Tenreiro Rocha-Neves J. M. Azevedo Filipe Andrade J. P. 《Nonlinear dynamics》2021,106(2):1525-1555
Nonlinear Dynamics - Given a data-set of Ribonucleic acid (RNA) sequences we can infer the phylogenetics of the samples and tackle the information for scientific purposes. Based on current data and... 相似文献
4.
Kobayashi M. Zhang Y. Ishikawa H. Sun J. Oddershede J. Juul Jensen D. Miura H. 《Experimental Mechanics》2021,61(5):817-828
Experimental Mechanics - The internal strain distribution developing during plastic deformation is important for understanding the mechanical properties of polycrystalline materials. Such... 相似文献
5.
Laguel Yassine Pillutla Krishna Malick Jérôme Harchaoui Zaid 《Set-Valued and Variational Analysis》2021,29(4):967-996
Set-Valued and Variational Analysis - R. Tyrell Rockafellar and his collaborators introduced, in a series of works, new regression modeling methods based on the notion of superquantile (or... 相似文献
6.
A numerical model was developed and validated to investigate the fluid–structure interactions between fully developed pipe flow and core–shell-structured microcapsule in a microchannel. Different flow rates and microcapsule shell thicknesses were considered. A sixth-order rotational symmetric distribution of von Mises stress over the microcapsule shell can be observed on the microcapsule with a thinner shell configuration, especially at higher flow rate conditions. It is also observed that when being carried along in a fully developed pipe flow, the microcapsule with a thinner shell tends to accumulate stress at a higher rate compared to that with a thicker shell. In general, for the same microcapsule configuration, higher flow velocity would induce a higher stress level over the microcapsule shell. The deformation gradient was used to capture the microcapsule's deformation in the present study. The effect of Young's modulus on the microcapsule shell on the microcapsule deformation was investigated as well. Our findings will shed light on the understanding of the stability of core–shell-structured microcapsule when subjected to flow-induced shear stress in a microfluidic system, enabling a more exquisite control over the breakup dynamics of drug-loaded microcapsule for biomedical applications. 相似文献
7.
8.
Li Y. Shi W. H. Dong L. M. Xu S. X. Huang H. J. Yin J. R. 《Journal of Applied Spectroscopy》2022,89(3):534-541
Journal of Applied Spectroscopy - Sr3B2O6:Dy3+, Eu3+ single-matrix white-light-emitting materials are prepared using the high-temperature solid-state method. The microstructure, emission spectrum,... 相似文献
9.
Restricted testing conditions were considered recently. For the maximal operator, Hytönen, Li and Sawyer [8] first obtained parental testing condition. Later, they [9] showed that it suffices to restrict testing to doubling cubes. Chen and Lacey [3] gave a similar restricted testing condition. In our paper, we discuss a version of the latter in the multilinear setting.
相似文献10.
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