全文获取类型
收费全文 | 14920篇 |
免费 | 2463篇 |
国内免费 | 2544篇 |
专业分类
化学 | 11079篇 |
晶体学 | 310篇 |
力学 | 966篇 |
综合类 | 218篇 |
数学 | 1747篇 |
物理学 | 5607篇 |
出版年
2024年 | 29篇 |
2023年 | 207篇 |
2022年 | 423篇 |
2021年 | 484篇 |
2020年 | 501篇 |
2019年 | 562篇 |
2018年 | 492篇 |
2017年 | 527篇 |
2016年 | 716篇 |
2015年 | 772篇 |
2014年 | 848篇 |
2013年 | 1131篇 |
2012年 | 1317篇 |
2011年 | 1348篇 |
2010年 | 986篇 |
2009年 | 1057篇 |
2008年 | 1133篇 |
2007年 | 1037篇 |
2006年 | 1007篇 |
2005年 | 785篇 |
2004年 | 714篇 |
2003年 | 595篇 |
2002年 | 704篇 |
2001年 | 615篇 |
2000年 | 419篇 |
1999年 | 335篇 |
1998年 | 226篇 |
1997年 | 146篇 |
1996年 | 134篇 |
1995年 | 121篇 |
1994年 | 93篇 |
1993年 | 105篇 |
1992年 | 62篇 |
1991年 | 57篇 |
1990年 | 46篇 |
1989年 | 47篇 |
1988年 | 32篇 |
1987年 | 26篇 |
1986年 | 20篇 |
1985年 | 22篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1979年 | 3篇 |
1975年 | 2篇 |
1968年 | 2篇 |
1957年 | 1篇 |
1936年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
分散化供应链的自组织演化机制建模与仿真 总被引:1,自引:0,他引:1
供应链是一个复杂适应系统.提出了分散化供应链演化的自组织机制.在开放结构下,多企业主体为了适应外部环境,在非线性互动中涌现出供应链协作结构和协调模式.借鉴生物系统环境适应能力思想,建立了分散化供应链自组织演化模型,并采用Multi-agent技术进行仿真,证明了分散化供应链的自组织演化机制.外部环境和企业内部机制因素控制着分散化供应链的演化,其演化对初始条件高度敏感,存在着锁定、路径依赖和混沌等自组织系统特性. 相似文献
992.
993.
994.
Gui‐Zhong Yang Xiao‐Lei Chen Lu‐Min Wang Jian‐Gao Shi Chun‐Zhong Li Tianxi Liu 《先进技术聚合物》2009,20(2):104-110
A series of fluorene‐based rod–coil liquid crystal polymers with different lengths of the coil segments on backbones were designed and synthesized by a palladium‐catalyzed Suzuki coupling‐reaction. The thermal stability, the UV–Vis absorption and fluorescence spectra in chloroform solution and thin film, the electrochemical properties, thermal behavior, and morphology of these rod–coil polymers were investigated. The thermal stability of these polymers steadily decreased on increasing the length of the coil segments on the backbone; their optical and electrochemical properties did not exhibit noticeable dependence on the weight fraction of the coil segments. However, the shoulder emission and the full width at the half‐maximum (FWHM) in PL spectra of the films increased, whereas the oxidation onset potentials and the corresponding HOMO energy levels decreased with the increase in the weight fraction of the coil segments, which was assigned to microphase separation and formation of folded chain conformation as the weight fraction of the coil segments increased. These polymers displayed a characteristic liquid crystalline texture. The variation of the weight fraction of the coil segments obviously affected the thermal behavior and morphology of these rod–coil polymers. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
995.
Jing Han Jin Mao Chen Xiao Wen Zhou Yuan Lin Jing Bo Zhang Jian Guang Jia 《中国化学快报》2008,19(8):1004-1007
The screen-printed nanoporous TiO2 thin film was employed to fabricate dye-sensitized solid-state solar cells using CuI as hole-transport materials. The solar cell based on nanoporous TiO2 thin film with large pores formed by the addition of polystyrene balls with diameter of 200 nm to the TiO2 paste exhibits photovoltaic performance enhancement, which is attributed to the good contact of CuI with surface of dye-sensitized thin film due to easy penetration of CuI in the film with large pores. 相似文献
996.
讨论了2维Zakharov方程组的Caucgy问题的爆破解.对径向对称爆破解,证明了原点0是爆破点,并建立了当t→T(爆破时间)时,集中率的下界. 相似文献
997.
In this paper, a kind of optimization problems with nonlinear inequality constraints is discussed. Combined the ideas of norm-relaxed SQP method and strongly sub-feasible direction method as well as a pivoting operation, a new fast algorithm with arbitrary initial point for the discussed problem is presented. At each iteration of the algorithm, an improved direction is obtained by solving only one direction finding subproblem which possesses small scale and always has an optimal solution, and to avoid the Maratos effect, another correction direction is yielded by a simple explicit formula. Since the line search technique can automatically combine the initialization and optimization processes, after finite iterations, the iteration points always get into the feasible set. The proposed algorithm is proved to be globally convergent and superlinearly convergent under mild conditions without the strict complementarity. Finally, some numerical tests are reported. 相似文献
998.
Quasi-interpolation is very useful in the study of the approximation theory and its applications, since the method can yield solutions directly and does not require solving any linear system of equations. However, quasi-interpolation is usually discussed only for gridded data in the literature. In this paper we shall introduce a generalized Strang–Fix condition, which is related to nonstationary quasi-interpolation. Based on the discussion of the generalized Strang–Fix condition we shall generalize our quasi-interpolation scheme for multivariate scattered data, too.
AMS subject classification 41A63, 41A25, 65D10Zong Min Wu: Supported by NSFC No. 19971017 and NOYG No. 10125102. 相似文献
999.
1000.
Noncovalentinteractionsplayadominantroleinmanyforefrontareasofmodemchemistry,frommat6rialsdesigntOmolecularbiology.Recelltly,theK -ninteractionshaveattractedmuchattentionbecauseoftheionseleCtivityinpotaSsiumchannelsl.Inothersystem,Sunneretal.showedthefirsttimebymassspectrometrythatK bindstobenzeneinthegasPhase:.ThisfindingstimulatedthestUdyoftheK -xinteractions.Indeed,theK -ninteractalshavealsobeen,identifiedbyX-raysinglecrystaldistractionanalysisforseveralcompouxtds:Km-be~usor--Phenyl',… 相似文献