全文获取类型
收费全文 | 16046篇 |
免费 | 2868篇 |
国内免费 | 1844篇 |
专业分类
化学 | 11395篇 |
晶体学 | 163篇 |
力学 | 1152篇 |
综合类 | 64篇 |
数学 | 1664篇 |
物理学 | 6320篇 |
出版年
2024年 | 56篇 |
2023年 | 353篇 |
2022年 | 605篇 |
2021年 | 597篇 |
2020年 | 639篇 |
2019年 | 601篇 |
2018年 | 558篇 |
2017年 | 501篇 |
2016年 | 859篇 |
2015年 | 755篇 |
2014年 | 954篇 |
2013年 | 1159篇 |
2012年 | 1483篇 |
2011年 | 1445篇 |
2010年 | 982篇 |
2009年 | 921篇 |
2008年 | 1070篇 |
2007年 | 944篇 |
2006年 | 855篇 |
2005年 | 762篇 |
2004年 | 531篇 |
2003年 | 435篇 |
2002年 | 424篇 |
2001年 | 349篇 |
2000年 | 306篇 |
1999年 | 326篇 |
1998年 | 268篇 |
1997年 | 239篇 |
1996年 | 277篇 |
1995年 | 272篇 |
1994年 | 194篇 |
1993年 | 150篇 |
1992年 | 160篇 |
1991年 | 147篇 |
1990年 | 127篇 |
1989年 | 101篇 |
1988年 | 85篇 |
1987年 | 70篇 |
1986年 | 51篇 |
1985年 | 41篇 |
1984年 | 30篇 |
1983年 | 25篇 |
1982年 | 14篇 |
1981年 | 16篇 |
1980年 | 10篇 |
1978年 | 2篇 |
1972年 | 1篇 |
1957年 | 6篇 |
1887年 | 1篇 |
1886年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
993.
Hongsheng Gao Hao Guo Xingliang Zheng Xiaoyu Huang 《Journal of polymer science. Part A, Polymer chemistry》2013,51(5):1099-1106
A series of well‐defined amphiphilic graft copolymer containing hydrophobic polyallene‐based backbone and hydrophilic poly(2‐(diethylamino)ethyl acrylate) (PDEAEA) side chains was synthesized by sequential living coordination polymerization of 6‐methyl‐1,2‐heptadiene‐4‐ol (MHDO) and single electron transfer‐living radical polymerization (SET‐LRP) of 2‐(diethylamino)ethyl acrylate (DEAEA). Ni‐catalyzed living coordination polymerization of MHDO was first performed in toluene to give a well‐defined double‐bond‐containing poly(6‐methyl‐1,2‐heptadiene‐4‐ol) (PMHDO) homopolymer with a low polydispersity (Mw/Mn = 1.10). Next, 2‐chloropropionyl chloride was used for the esterification of pendant hydroxyls in every repeating unit of the homopolymer so that the homopolymer was converted to PMHDO‐Cl macroinitiator. Finally, SET‐LRP of DEAEA was initiated by the macroinitiator in tetrahydrofuran/H2O using CuCl/tris(2‐(dimethylamino)ethyl)amine as catalytic system to afford well‐defined PMHDO‐g‐PDEAEA graft copolymers (Mw/Mn ≤ 1.22) through the grafting‐from strategy. The critical micelle concentration (cmc) was determined by ?uorescence spectroscopy with N‐phenyl‐1‐naphthylamine as probe and the micellar morphology was visualized by transmission electron microscopy. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献
994.
995.
996.
997.
Yao Yun Hu Jing Mei Yin Da Bin Gao Ying Ping Jia Guang Yun Zhou Ying Na Cui Shen Min Li 《中国化学快报》2008,19(5):529-532
Photopromoted carbonylation of 1-bromo-6-chlorohexane with CO catalyzed by CuBr2 and CdI2 has been carried out under ambient conditions. The results indicate that the carbonylation proceeds with the major product of chloroester ClCH2(CH2)5COOCH3 under catalysis of CuBr2. Furthermore, the activity of the carbonylation can be improved by addition of basic additives (NaOAc, Na3PO4 or (n-C4H9)3N). Among these additives, (n-C4H9)3N is the most efficient in terms of the yield of ClCH2(CH2)5COOCH3. However, the methoxycarbonyl substituting chlorine product of BrCH2(CH2)5COOCH3 is not obtained in the presence of CdI2. This is quite different from the carbonylation of monochloroalkane. 相似文献
998.
Based on calculations using density functional theory, we show that C60 can act as a chemical Faraday cage in which a highly magnetic metal cluster with a high chemical reactivity can be encapsulated. As an example, we find that C60 can encapsulate a Fe3 cluster, while it is much less likely to encapsulate a Fe2 cluster. Spin multiplicity (=9) of the Fe3@C60 is very high, being comparable to that (=11) of a free Fe3 cluster. Geometrically, the triangular plane of the cluster is perpendicular to a S6 axis of the fullerene. 相似文献
999.
This paper presents a nonlinear dual transformation method and general complementary energy principle for solving large deformation theory of elastoplasticity governed by nonsmooth constitutive laws. It is shown that by using this method and principle, the nonconvex and nonsmooth total potential energy is dual to a smooth complementary energy functional, and fully nonlinear equilibrium equations in finite deformation problems can be converted into certain tensor equations. The algebraic relation between the first and the second Piola–Kirchhoff stresses are revealed. A closed form solution for general three-dimensional large deformation boundary value problems is obtained. The properties of this general solution are clarified by a triality extremum principle. This triality theory reveals an important phenomenon in nonconvex variational problems. Applications are illustrated by nonlinear, nonsmooth equilibrium problems in Hencky's plasticity, 3D cylindrical structures and post buckling analysis of elastoplastic bar with jumping and hardening effects. The idea and methods presented in this paper can be used and generalized to solve many nonlinear boundary value problems in finite deformation theory.Sommario. Il lavoro presenta un metodo di trasformazione duale nonlineare ed un principio generale di energia complementare per la soluzione di problemi di teoria elastoplastica in grandi deformazioni governati da leggi costitutive con discontinuità. Si mostra come, usando il metodo ed il principio proposti, l' energia potenziale totale discontinua e nonconvessa duale di un funzionale energia complementare continuo, e le equazioni di equilibrio nonlineare in problemi di deformazione finita, possano essere convertite in equazioni tensoriali. Vengono mostrate le relazioni algebriche fra il primo ed il secondo tensore delle tensioni di Piola–Kirchhoff. Si ottiene una soluzione in forma chiusa per problemi al contorno generali tridimensionali in grandi deformazioni. Le proprietà di tale soluzione generale vengono chiarite per mezzo di un principio estremale di trialità. La eoria della trialità evidenzia un fenomeno importante in problemi variazionali nonconvessi. Vengono presentate applicazioni a problemi di equilibrio nonlineare con discontinuità in situazioni di plasticità alla Hencky, strutture cilindriche in 3D, e nell'analisi postcritica di una barra elastoplastica con effetti hardening e di jumping. L'idea ed i metodi presentati in questo lavoro possono essere usati e generalizzati per risolvere molti problemi al contorno nonlineari nella teoria delle deformazioni finite. 相似文献
1000.
In this study, one kind of lithium aluminosilicate-β-quartz glass-ceramic containing Na2O has been chosen, which can be used for low-temperature bonding with a higher bonding rate for the manufacture of microelectronic mechanical systems. The microstructure of the glass-ceramic is analyzed by transmission electron microscopy, high resolution transmission electron microscopy, selected-area diffraction, energy dispersive spectrometry and X-ray diffraction. The influence of the heat treatment process of the glass on the properties and the microstructure of the glass-ceramics is discussed. The microstructure of the glass-ceramic has the continuous glassy region with higher alkali metal ion content, which benefits the low-temperature anodic bonding. 相似文献