全文获取类型
收费全文 | 209533篇 |
免费 | 3589篇 |
国内免费 | 1444篇 |
专业分类
化学 | 115983篇 |
晶体学 | 3767篇 |
力学 | 8429篇 |
综合类 | 64篇 |
数学 | 20315篇 |
物理学 | 66008篇 |
出版年
2020年 | 2018篇 |
2019年 | 2209篇 |
2018年 | 2481篇 |
2017年 | 2607篇 |
2016年 | 3930篇 |
2015年 | 2589篇 |
2014年 | 4073篇 |
2013年 | 9660篇 |
2012年 | 7239篇 |
2011年 | 8769篇 |
2010年 | 6193篇 |
2009年 | 6103篇 |
2008年 | 7653篇 |
2007年 | 7461篇 |
2006年 | 7092篇 |
2005年 | 6417篇 |
2004年 | 5835篇 |
2003年 | 5332篇 |
2002年 | 5087篇 |
2001年 | 6323篇 |
2000年 | 4744篇 |
1999年 | 3703篇 |
1998年 | 2866篇 |
1997年 | 2795篇 |
1996年 | 2701篇 |
1995年 | 2551篇 |
1994年 | 2422篇 |
1993年 | 2222篇 |
1992年 | 2883篇 |
1991年 | 2788篇 |
1990年 | 2740篇 |
1989年 | 2735篇 |
1988年 | 2741篇 |
1987年 | 2743篇 |
1986年 | 2620篇 |
1985年 | 3317篇 |
1984年 | 3327篇 |
1983年 | 2612篇 |
1982年 | 2716篇 |
1981年 | 2773篇 |
1980年 | 2535篇 |
1979年 | 2878篇 |
1978年 | 2862篇 |
1977年 | 2982篇 |
1976年 | 2818篇 |
1975年 | 2554篇 |
1974年 | 2510篇 |
1973年 | 2466篇 |
1972年 | 1702篇 |
1968年 | 1703篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Russian Physics Journal - The process of radiative decay of a Higgs boson into a fermion-antifermion pair $$ H\Rightarrow \overline{ff}\upgamma . $$ is investigated within the framework of the... 相似文献
12.
Journal of Optimization Theory and Applications - We distinguish two kinds of piecewise linear functions and provide an interesting representation for a piecewise linear function between two normed... 相似文献
13.
Differential Equations - Galathea traps for confining plasma in a magnetic field created by current-carrying conductors immersed in the plasma volume constitute a promising class of objects for... 相似文献
14.
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
15.
Journal of Applied Spectroscopy - The elemental composition of one- and two-rupee coins issued in different years by the Reserve Bank of India (RBI) was investigated using laser-induced breakdown... 相似文献
16.
17.
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
18.
A graphic sequence π =(d1, d2,..., dn) is said to be forcibly k-edge-connected if every realization of π is k-edge-connected. In this paper, we obtain a new sufficient degree condition for π to be forcibly k-edgeconnected. We also show that this new sufficient degree condition implies a strongest monotone degree condition for π to be forcibly 2-edge-connected and a conjecture about a strongest monotone degree condition for π to be forcibly 3-edge-connected due to... 相似文献
19.
The molecular geometries and dissociation energies of AnO (An = Bk–Lr) molecules were first obtained at thecoupled-cluster single-, double-, and perturbative triple-excitations [CCSD(T)] level of theory. Four hybrid functionals,B3LYP, M06-2X, TPSSh, and PBE0, were also employed in the calculations for the sake of comparison. In comparison ofthe CCSD(T) results, B3LYP, TPSSh, and PBE0 functionals can obtain more appropriate results than M06-2X and MP2.The analyses on molecular orbitals show that the 7s, 6d, and 5f atomic orbitals of actinide (An) atoms participate in thebonding of An–O bonds. The partial covalent nature between An and O atoms is revealed by QTAIM analyses. 相似文献
20.
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