全文获取类型
收费全文 | 30629篇 |
免费 | 9685篇 |
国内免费 | 14710篇 |
专业分类
化学 | 21251篇 |
晶体学 | 1608篇 |
力学 | 4246篇 |
综合类 | 1140篇 |
数学 | 4819篇 |
物理学 | 21960篇 |
出版年
2024年 | 278篇 |
2023年 | 950篇 |
2022年 | 978篇 |
2021年 | 1199篇 |
2020年 | 955篇 |
2019年 | 1181篇 |
2018年 | 810篇 |
2017年 | 1158篇 |
2016年 | 1318篇 |
2015年 | 1472篇 |
2014年 | 2966篇 |
2013年 | 2405篇 |
2012年 | 2306篇 |
2011年 | 2576篇 |
2010年 | 2615篇 |
2009年 | 2704篇 |
2008年 | 2980篇 |
2007年 | 2415篇 |
2006年 | 2687篇 |
2005年 | 2524篇 |
2004年 | 2459篇 |
2003年 | 2352篇 |
2002年 | 1901篇 |
2001年 | 1690篇 |
2000年 | 1330篇 |
1999年 | 1191篇 |
1998年 | 1014篇 |
1997年 | 966篇 |
1996年 | 885篇 |
1995年 | 872篇 |
1994年 | 796篇 |
1993年 | 610篇 |
1992年 | 603篇 |
1991年 | 524篇 |
1990年 | 454篇 |
1989年 | 501篇 |
1988年 | 131篇 |
1987年 | 80篇 |
1986年 | 61篇 |
1985年 | 38篇 |
1984年 | 24篇 |
1983年 | 23篇 |
1982年 | 28篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1959年 | 7篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
94.
A sample of 1233 events is used to study the general characteristics of {}^{16}O-Em interactions at 4.5 A GeV/c. Multiplicity and angular distributions of slow particles and correlations among them are discussed. The present data are compared with the corresponding results from the interactions of other projectiles at the same energy and also the same projectile at different energies. The results indicate that black particle production is independent of the energy and mass of the projectile, but for grey particles it is dependent on the mass of projectile. 相似文献
95.
Zuo LIU Zhen De WU 《数学学报(英文版)》2005,21(5):997-1000
Let κ be non-negative integer. The unoriented bordism classes, which can be represented as [RP(ξ^κ)] where ξ^κ is a k-plane bundle, form an ideal of the unoriented bordism ring MO.. A group of generators of this ideal expressed by a base of MO. and a necessary and sufficient condition for a bordism class to belong to this ideal are given. 相似文献
96.
The Langevin equation is used to simulate the fission process of ^112Sn ^112Sn and ^116Sn ^116Sn. The mass distribution of the fission fragments are given by assuming the process of symmetric fission or asymmetric fission with the Gaussian probability sampling. The isoscaling behaviour has been observed from the analysis of fission fragments of both the reactions, and the isoscaling parameter α seems to be sensitive to the width of fission probability and the beam energy. 相似文献
97.
Singlet-Triplet Transition in Quantum Dots Confined by Triangular and Bowl-Like Potentials: the Effect of Electric Fields 下载免费PDF全文
We theoretically investigate the energy spectra of two-electron two-dimensional (2e 2D) quantum dots (QDs) confined by triangular potentials and bowl-like potentials in a magnetic field by exact diagonalization in the framework of effective mass theory. An in-plane electric field is found to contribute to the singlet-triplet transition of the ground state of the 2e 2D QDs confined by triangular or bowl-like potentials in a perpendicular magnetic field. The stronger the in-plane electric field, the smaller the magnetic field for the total spin of the ground states in the dot systems to change from S = 0 to S = 1. However, the influence of an in-plane electric field on the singlettriplet transition of the ground state of two electrons in a triangular QD modulated by a perpendicular magnetic field is quite small because the triangular potential just deviates from the harmonic potential well slightly. We find that the strength of the perpendicular magnetic field needed for the spin singlet-triplet transition of the ground state of the QD confined by a bowl-like potential is reduced drastically by applying an in-plane electric field. 相似文献
98.
采用时域有限差分方法(FDTD)进行元件表面微结构电磁场分布的数值模拟;同时实验分析了化学湿法刻蚀对光学元件表面面形及粗糙度、激光损伤阈值等的影响。 相似文献
99.
强冲击载荷下自由表面的粒子喷射现象还没有被清楚认识,很难从理论上给以准确的计算模型,因而从实验测定材料在冲击载荷下自由面面喷射物质的分布和粒子尺寸大小就显得非常重要。测量微粒场的脉冲激光同轴全息技术,具有在纳秒或更在短时间内“固化”运动微粒场、测量精度高、景深长、光路简单和获得的信息量大等优点。这些优势使得脉冲激光同轴全息技术成为研究微喷射场的重要测试手段之一。 相似文献
100.
A G 4.0 dendrimer-like poly (amido amine) (PAMAM) based on silica nanoparticles was fabricated via a divergent approach.It was built from γ-aminopropyi silica nanoparfides (APSN) core via repetitive addition of acrylate (MA) and hexylenediamine (HDA). FT-IR and EA were used to monitor the progress of dendrimer during each step. The amino group content of the resulting product increased from 0.49 to 3.72 mmol/g after the 4th generation. In addition, the percentage of grafting increased with increasing generation and reached to 65.9% after 4th generation. It was found that the resulting silica nanoparticles could be dispersed in methanol with a mean hydrodynamic particle diameter of 152.7 nm although the silica nanoparticles had agglomerated during the storage period. 相似文献