全文获取类型
收费全文 | 18091篇 |
免费 | 2186篇 |
国内免费 | 1565篇 |
专业分类
化学 | 11575篇 |
晶体学 | 229篇 |
力学 | 836篇 |
综合类 | 151篇 |
数学 | 3036篇 |
物理学 | 6015篇 |
出版年
2023年 | 248篇 |
2022年 | 378篇 |
2021年 | 428篇 |
2020年 | 591篇 |
2019年 | 545篇 |
2018年 | 548篇 |
2017年 | 549篇 |
2016年 | 905篇 |
2015年 | 888篇 |
2014年 | 943篇 |
2013年 | 1543篇 |
2012年 | 1412篇 |
2011年 | 1526篇 |
2010年 | 1090篇 |
2009年 | 1021篇 |
2008年 | 1105篇 |
2007年 | 912篇 |
2006年 | 760篇 |
2005年 | 645篇 |
2004年 | 489篇 |
2003年 | 426篇 |
2002年 | 424篇 |
2001年 | 312篇 |
2000年 | 299篇 |
1999年 | 243篇 |
1998年 | 172篇 |
1997年 | 176篇 |
1996年 | 155篇 |
1995年 | 155篇 |
1994年 | 126篇 |
1993年 | 127篇 |
1992年 | 107篇 |
1991年 | 100篇 |
1990年 | 88篇 |
1989年 | 83篇 |
1988年 | 104篇 |
1987年 | 79篇 |
1986年 | 87篇 |
1985年 | 102篇 |
1984年 | 93篇 |
1983年 | 87篇 |
1982年 | 82篇 |
1981年 | 78篇 |
1980年 | 95篇 |
1979年 | 91篇 |
1978年 | 99篇 |
1977年 | 91篇 |
1976年 | 69篇 |
1974年 | 73篇 |
1973年 | 79篇 |
排序方式: 共有10000条查询结果,搜索用时 158 毫秒
121.
Kan‐Yi Pu Yi Chen Xiao‐Ying Qi Chun‐Yang Qin Qing‐Quan Chen Hong‐Yu Wang Yun Deng Qu‐Li Fan Yan‐Qin Huang Shu‐Juan Liu Wei Wei Bo Peng Wei Huang 《Journal of polymer science. Part A, Polymer chemistry》2007,45(16):3776-3787
In this contribution, we demonstrate a new effective methodology for constructing highly efficient and durable poly(p‐phenyleneethynylene) (PPE) containing emissive material with nonaggregating and hole‐facilitating properties through the introduction of hole‐transporting blocks into the PPE system as the grafting coils as well as building the energy donor–acceptor architecture between the grafting coils and the PPE backbone. Poly(2‐(carbazol‐9‐yl)ethyl methacrylate) (PCzEMA), herein, is chosen as the hole‐transporting blocks, and incorporated into the PPE system as the grafting coils via atom transfer radical polymerization. The chemical structure of the resultant copolymer, PPE‐g‐PCzEMA, was characterized by NMR and gel permeation chromatography, showing that the desirable copolymer was obtained with the narrow polydispersity. The increased thermal stability of PPE‐g‐PCzEMA was confirmed by thermogravimetric analysis and differential scanning calorimetry along with its macroinitiator. The optoelectronic properties of this copolymer were studied in detail by ultraviolet‐visible absorption, photoluminescence emission and excitation spectra, and cyclic voltammogram (CV). The results indicate that PPE‐g‐PCzEMA exhibits the solid‐state luminescent property dominated by individual lumophores, and also the energy transfer process from the PCzEMA blocks to the PPE backbone with a relatively higher energy transfer efficiency in the solid‐state compared to that of the solution state. Additionally, the hole‐injection property is greatly facilitated due to the presence of PCzEMA, as confirmed by CV profiles. All these data indicate that PPE‐g‐PCzEMA is a good candidate for use in optoelectronic devices. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3776–3787, 2007 相似文献
122.
123.
关于李萨如图形讨论的小结 总被引:4,自引:0,他引:4
对《大学物理》和其它一些刊物上多年来关于李萨如图形的讨论作了归纳和分析。 相似文献
124.
125.
126.
Dragan DJURCIC Aleksandar TORGASEV 《数学学报(英文版)》2006,22(3):689-692
In this paper, we prove some properties of the Seneta sequences and functions, and in particular we prove a representation theorem in the Karamata sense for the sequences from the Seneta class SOc. 相似文献
127.
AN ESTIMATE ON THE DISTRIBUTION AND MOMENTS OF THE LAST EXIT TIME OF AN ELLIPTIC DIFFUSION PROCESS 总被引:1,自引:0,他引:1
Let LB be the last exit time from a compact set B of an elliptic diffusion process X. A moderate estimate for the distribution of LB is obtained, and the sufficient and necessary condition for Ex(LBk)<∞is proved. 相似文献
128.
Marston Conder Aleksander Malnič Dragan Marušič Primž Potočnik 《Journal of Algebraic Combinatorics》2006,23(3):255-294
A list is given of all semisymmetric (edge- but not vertex-transitive) connected finite cubic graphs of order up to 768. This
list was determined by the authors using Goldschmidt's classification of finite primitive amalgams of index (3,3), and a computer
algorithm for finding all normal subgroups of up to a given index in a finitely-presented group. The list includes several
previously undiscovered graphs. For each graph in the list, a significant amount of information is provided, including its
girth and diameter, the order of its automorphism group, the order and structure of a minimal edge-transitive group of automorphisms,
its Goldschmidt type, stabiliser partitions, and other details about its quotients and covers. A summary of all known infinite
families of semisymmetric cubic graphs is also given, together with explicit rules for their construction, and members of
the list are identified with these. The special case of those graphs having K1,3 as a normal quotient is investigated in detail.
Supported in part by N.Z. Marsden Fund (grant no. UOA 124) and N.Z. Centres of Research Excellence Fund (grant no. UOA 201)
Supported in part by “Ministrstvo za šolstvo, znanost in šport Slovenije”, research program no. 101-506.
Supported in part by research projects no. Z1-4186-0101 and no. Z1-3124-0101. The fourth author would like to thank the University
of Auckland for hospitality during his visit there in 2003. 相似文献
129.
Radu Ioan Boţ Ioan Bogdan Hodrea Gert Wanka 《Nonlinear Analysis: Theory, Methods & Applications》2007
Considering a constrained fractional programming problem, within the present paper we present some necessary and sufficient conditions, which ensure that the optimal objective value of the considered problem is greater than or equal to a given real constant. The desired results are obtained using the Fenchel–Lagrange duality approach applied to an optimization problem with convex or difference of convex (DC) objective functions and finitely many convex constraints. These are obtained from the initial fractional programming problem using an idea due to Dinkelbach. We also show that our general results encompass as special cases some recently obtained Farkas-type results. 相似文献
130.
Gašper Jaklič Jernej Kozak Marjeta Krajnc Vito Vitrih Emil Žagar 《Numerical Algorithms》2007,45(1-4):49-60
In this paper, three-pencil lattices on triangulations are studied. The explicit representation of a lattice, based upon barycentric
coordinates, enables us to construct lattice points in a simple and numerically stable way. Further, this representation carries
over to triangulations in a natural way. The construction is based upon group action of S
3 on triangle vertices, and it is shown that the number of degrees of freedom is equal to the number of vertices of the triangulation.
相似文献