全文获取类型
收费全文 | 19487篇 |
免费 | 3441篇 |
国内免费 | 1987篇 |
专业分类
化学 | 13332篇 |
晶体学 | 248篇 |
力学 | 1285篇 |
综合类 | 140篇 |
数学 | 2238篇 |
物理学 | 7672篇 |
出版年
2024年 | 30篇 |
2023年 | 420篇 |
2022年 | 577篇 |
2021年 | 712篇 |
2020年 | 833篇 |
2019年 | 780篇 |
2018年 | 666篇 |
2017年 | 616篇 |
2016年 | 1004篇 |
2015年 | 949篇 |
2014年 | 1115篇 |
2013年 | 1371篇 |
2012年 | 1805篇 |
2011年 | 1756篇 |
2010年 | 1319篇 |
2009年 | 1212篇 |
2008年 | 1245篇 |
2007年 | 1048篇 |
2006年 | 1097篇 |
2005年 | 891篇 |
2004年 | 626篇 |
2003年 | 523篇 |
2002年 | 478篇 |
2001年 | 364篇 |
2000年 | 353篇 |
1999年 | 383篇 |
1998年 | 328篇 |
1997年 | 326篇 |
1996年 | 303篇 |
1995年 | 264篇 |
1994年 | 232篇 |
1993年 | 176篇 |
1992年 | 164篇 |
1991年 | 154篇 |
1990年 | 121篇 |
1989年 | 107篇 |
1988年 | 90篇 |
1987年 | 63篇 |
1986年 | 72篇 |
1985年 | 53篇 |
1984年 | 38篇 |
1983年 | 35篇 |
1982年 | 24篇 |
1981年 | 21篇 |
1980年 | 18篇 |
1976年 | 11篇 |
1975年 | 16篇 |
1973年 | 12篇 |
1972年 | 13篇 |
1965年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
A Bayesian approach is used to analyze the seismic events with magnitudes at least 4.7 on Taiwan. Following the idea proposed
by Ogata (1988,Journal of the American Statistical Association,83, 9–27), an epidemic model for the process of occurrence times given the observed magnitude values is considered, incorporated
with gamma prior distributions for the parameters in the model, while the hyper-parameters of the prior are essentially determined
by the seismic data in an earlier period. Bayesian inference is made on the conditional intensity function via Markov chain
Monte Carlo method. The results yield acceptable accuracies in predicting large earthquake events within short time periods. 相似文献
62.
Precise measurement of magnetic moment of short-lived β-emitting nuclei12B ( I π=1+, T 1/2=20.18 ms)
Zhou Dongmei Zheng Yongnan Du Enpeng Xu Yongjun Zhu Jiazheng Yuan Daqing Wang Zhiqiang Luo Hailong Zuo Yi Ma Ruigang Duan Xiao M. Mihara M. Fukuda K. Matsuta T. Minamisono Zhu Shengyun 《中国科学G辑(英文版)》2004,47(5):531-539
The spin polarized β-emitting nuclei12B (I
π=1+,T
1/2=20.18 ms) were produced by the nuclear reaction11B(d, p)12B and by the selection technique of the incident deuteron energy and the12B recoil angle following the nuclear reaction. The nuclear magnetic moment of the short-lived nuclei12B was measured by β-NMR with the β-NMR and β-NQR setup established for the first time in China. The nuclear magnetic moment
of12B was determined to be μ=0.99993±0.00048 nm org=0.99993±0.00048 after the precise correction of the Knight shift. 相似文献
63.
64.
Fan Chung 《Annals of Combinatorics》2005,9(1):1-19
We consider Laplacians for directed graphs and examine their eigenvalues. We introduce a notion of a circulation in a directed graph and its connection with the Rayleigh quotient. We then define a Cheeger constant and establish the Cheeger inequality for directed graphs. These relations can be used to deal with various problems that often arise in the study of non-reversible Markov chains including bounding the rate of convergence and deriving comparison theorems.Received September 8, 2004 相似文献
65.
Tunable microlens arrays using polymer network liquid crystal 总被引:1,自引:0,他引:1
A tunable-focus microlens array based on polymer network liquid crystal (PNLC) is demonstrated. The PNLC was prepared using an ultraviolet (UV) light exposure through a patterned photomask. The photocurable monomer in each of the UV exposed spot forms an inhomogeneous centro-symmetrical polymer network which acts as a lens when a homogeneous electric field is applied to the cell. The focal length of the microlens arrays is tunable with the applied voltage. 相似文献
66.
L. J. Qin X. L. Meng Ch. L. Du L. Zhu B. Ch. Xu H. Zh. Xu F. Y. Jiang Z. Sh. Shao 《Optics & Laser Technology》2004,36(1):47-50
We have demonstrated a passively Q-switched operation of Nd:GdVO4 laser in which a GaAs crystal is used as the saturable absorber for the first time as far as we know. A maximum average output power of 1.64 W was obtained at an incident pump power of 12 W, the corresponding optical conversion efficiency and peak power were 13.7% and 116.8 W, respectively. The maximum peak energy obtained in the experiment by 50% transmission couple was 19 μJ. 相似文献
67.
68.
Summary Vezetéknév 相似文献
69.
Through arylsulfonyl activation of thiourea, efficient synthesis of oligomeric guanidines can be achieved in either solution or solid-phase. Incorporation of TFA-sensitive arylsulfonyl groups, such as Pbf, during the synthesis greatly simplifies deprotection procedures for obtaining the final oligomeric guanidine products. 相似文献
70.
We prove that a locally compact ANR-space X is a Q-manifold if and only if it has the Disjoint Disk Property (DDP), all points of X are homological Z
∞-points and X has the countable-dimensional approximation property (cd-AP), which means that each map f: K → X of a compact polyhedron can be approximated by a map with the countable-dimensional image. As an application we prove that
a space X with DDP and cd-AP is a Q-manifold if some finite power of X is a Q-manifold. If some finite power of a space X with cd-AP is a Q-manifold, then X
2 and X × [0, 1] are Q-manifolds as well. We construct a countable family χ of spaces with DDP and cd-AP such that no space X ∈ χ is homeomorphic to the Hilbert cube Q whereas the product X × Y of any different spaces X, Y ∈ χ is homeomorphic to Q. We also show that no uncountable family χ with such properties exists.
This work was supported by the Slovenian-Ukrainian (Grant No. SLO-UKR 04-06/07) 相似文献