全文获取类型
收费全文 | 12000篇 |
免费 | 2164篇 |
国内免费 | 1452篇 |
专业分类
化学 | 8385篇 |
晶体学 | 169篇 |
力学 | 850篇 |
综合类 | 116篇 |
数学 | 1294篇 |
物理学 | 4802篇 |
出版年
2024年 | 25篇 |
2023年 | 293篇 |
2022年 | 345篇 |
2021年 | 482篇 |
2020年 | 525篇 |
2019年 | 524篇 |
2018年 | 430篇 |
2017年 | 388篇 |
2016年 | 640篇 |
2015年 | 588篇 |
2014年 | 705篇 |
2013年 | 843篇 |
2012年 | 1120篇 |
2011年 | 1093篇 |
2010年 | 821篇 |
2009年 | 755篇 |
2008年 | 754篇 |
2007年 | 659篇 |
2006年 | 684篇 |
2005年 | 596篇 |
2004年 | 390篇 |
2003年 | 321篇 |
2002年 | 318篇 |
2001年 | 240篇 |
2000年 | 218篇 |
1999年 | 225篇 |
1998年 | 184篇 |
1997年 | 211篇 |
1996年 | 192篇 |
1995年 | 178篇 |
1994年 | 144篇 |
1993年 | 102篇 |
1992年 | 96篇 |
1991年 | 81篇 |
1990年 | 80篇 |
1989年 | 72篇 |
1988年 | 52篇 |
1987年 | 30篇 |
1986年 | 50篇 |
1985年 | 33篇 |
1984年 | 18篇 |
1983年 | 17篇 |
1982年 | 15篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1975年 | 7篇 |
1973年 | 4篇 |
1972年 | 7篇 |
1965年 | 6篇 |
1964年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
31.
A nanoscale
multivalent platinum drug based on a poly(amidoamine) [PAMAM] dendrimer (generation
4.5, carboxylate surface) has been synthesized and fully characterized using
a variety of spectroscopic, chromatographic and thermal methods. Treatment
of the dendrimer with an aqueous solution containing an excess diaquo(cis-1,2-diaminocyclohexane)platinum(II) produces
a conjugate containing approximately forty (diaminocyclohexane)platinum(II)
moieties at the surface of the dendrimer. This material undergoes smooth two-stage
thermal decomposition to provide residual platinum oxide reflecting the platinum
loading in the drug. 相似文献
32.
On Polynomial Functions over Finite Commutative Rings 总被引:1,自引:0,他引:1
Jian Jun JIANG Guo Hua PENG Qi SUN Qi Fan ZHANG 《数学学报(英文版)》2006,22(4):1047-1050
Let R be an arbitrary finite commutative local ring. In this paper, we obtain a necessary and sufficient condition for a function over R to be a polynomial function. Before this paper, necessary and sufficient conditions for a function to be a polynomial function over some special finite commutative local rings were obtained. 相似文献
33.
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
34.
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
35.
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
36.
Huimin Xie Biao Li Robert Geer Bai Xu James Castracane 《Optics and Lasers in Engineering》2003,40(3):163-177
A focused ion beam (FIB) Moiré method is proposed to measure the in-plane deformation of object in a micrometer scale. The FIB Moiré is generated by the interference between a prepared specimen grating and FIB raster scan lines. The principle of the FIB Moiré is described. The sensitivity and accuracy of deformation measurement are discussed in detail. Several specimen gratings with 0.14 and 0.20 μm spacing are used to generate FIB Moiré patterns. The FIB Moiré method is successfully used to measure the residual deformation in a micro-electro-mechanical system structure after removing the SiO2 sacrificial layer with a 5000 lines/mm grating. The results demonstrate the feasibility of this method. 相似文献
37.
38.
Summary Vezetéknév 相似文献
39.
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
40.
范跃祖,宁文如,刘剑.光纤陀螺随机误差的滤波方案的探讨.数理统计与管理,1997,16(4),29~32.光纤陀螺是新一代的光学陀螺仪,它的性能决定着惯性参照系统的精度。光纤陀螺的误差分为两大类。一类是有规律的,另一类是随机的。本文提出了两种新的用于光纤陀螺随机误差补偿的Kalman滤波方案,考虑了两种随机模型:(Ⅰ)角速度变化为等随机的;(Ⅱ)角速度变化为等随机加速的。仿真结果表明,第二种方案对噪声起到了很好的抑制作用和滤波效果 相似文献