全文获取类型
收费全文 | 1695篇 |
免费 | 33篇 |
国内免费 | 8篇 |
专业分类
化学 | 1047篇 |
晶体学 | 11篇 |
力学 | 22篇 |
数学 | 354篇 |
物理学 | 302篇 |
出版年
2022年 | 10篇 |
2021年 | 18篇 |
2020年 | 13篇 |
2019年 | 22篇 |
2018年 | 23篇 |
2017年 | 17篇 |
2016年 | 37篇 |
2015年 | 37篇 |
2014年 | 38篇 |
2013年 | 73篇 |
2012年 | 83篇 |
2011年 | 81篇 |
2010年 | 62篇 |
2009年 | 71篇 |
2008年 | 83篇 |
2007年 | 85篇 |
2006年 | 76篇 |
2005年 | 63篇 |
2004年 | 48篇 |
2003年 | 49篇 |
2002年 | 58篇 |
2001年 | 22篇 |
2000年 | 10篇 |
1999年 | 14篇 |
1998年 | 13篇 |
1997年 | 9篇 |
1996年 | 18篇 |
1993年 | 9篇 |
1991年 | 17篇 |
1986年 | 10篇 |
1985年 | 18篇 |
1984年 | 9篇 |
1982年 | 11篇 |
1981年 | 12篇 |
1980年 | 9篇 |
1979年 | 11篇 |
1978年 | 15篇 |
1977年 | 11篇 |
1976年 | 9篇 |
1975年 | 9篇 |
1973年 | 9篇 |
1943年 | 9篇 |
1942年 | 13篇 |
1941年 | 11篇 |
1927年 | 10篇 |
1912年 | 11篇 |
1910年 | 9篇 |
1909年 | 19篇 |
1890年 | 8篇 |
1885年 | 11篇 |
排序方式: 共有1736条查询结果,搜索用时 27 毫秒
1.
2.
Formation of porous polymer morphology by microsyneresis during divinylbenzene polymerization
下载免费PDF全文
![点击此处可从《Journal of Polymer Science.Polymer Physics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Libuše Hanková Ladislav Holub Karel Jeřábek 《Journal of Polymer Science.Polymer Physics》2015,53(11):774-781
This article describes the investigation of the importance of various reaction conditions on microsyneretic pore formation during polymerization of divinylbenzene (DVB) under so‐called “solvothermal” conditions. To induce microsyneretic pore formation, the most important parameter is an unusually high dilution of monomers with a “good” porogen solvating the polymer chains. High dilution and solvation of the growing poly(DVB) chains promote the prolongation of the polymer chains rather than their interconnection by crosslinking. Consequently, when the polymer gel density reaches the point where syneresis starts, the polymer network is geometrically too extensive to be broken up into precipitating entities and, instead, porogen droplets are formed within the continuous polymer gel. The pore geometry created by microsyneresis offers high surface area in wide mesopores and hence, high capacity for supporting functional groups or reactions with much better accessibility than narrow pores between polymer microspheres produced by macrosyneresis in conventional styrenic polymer supports. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 774–781 相似文献
3.
N. Raju T. Špaček J. Ježek I. M. Caminiti F. Leinisch K. Hideg P. Ježek W. E. Trommer 《Applied magnetic resonance》2006,30(3-4):373-383
Electron paramagnetic resonance (EPR) spectroscopy of spin-labeled fatty acids was used to investigate their interaction withEscherichia coli-expressed human mitochondrial uncoupling protein UCP2 refolded from inclusion bodies in nonaethylene glycol monododecyl ether (C12E9) micelles. 5-DOXYL-stearic acid and 4-PROXYL-palmitic acid bound to UCP2 exhibited additional clearly separated h+1I, h?1I “immobile” peaks in the low- and high-field region, respectively, separated by 42 and 44 Gauss, and extensively reduced h+1M, h?1M “mobile” peaks, separated by about 30 G, whereas with 7-DOXYL-stearic acid the I and M peaks were smoothed together into one wide peak. Competition of 4-PROXYL-palmitic acid with added palmitic acid, arachidonic acid, and all-cis-8,11,14-eicosatrienoic acid and of 7-DOXYL-stearic acid with arachidonic acid was indicated by the disappearance of the h+1I, h?1I “immobile” peaks, whereas redistribution in micelles without protein was indicated by the rising of the h+1M, h?1M “mobile” peaks. In conclusion, a competition of palmitic, arachidonic, and eicosatrienoic acid within a putative fatty acid binding site was observed for mitochondrial uncoupling protein UCP2. This finding together with the observation of EPR spectra of highly immobilized probes exclusively in the presence of the recombinant UCP2 suggest the existence of a fatty acid binding site on UCP2 which is a prerequisite of the fatty acid cycling mechanism as previously postulated for UCP1. 相似文献
4.
J. Ježek 《Czechoslovak Mathematical Journal》2004,54(1):233-246
We investigate congruences in one-element extensions of algebras in the variety generated by tournaments. 相似文献
5.
6.
7.
We prove that a finite unary algebra with at least two operation symbols is a homomorphic image of a (finite) subdirectly
irreducible algebra if and only if the intersection of all its subalgebras which have at least two elements is nonempty.
While working on this paper the first and the third authors were partially supported by the Grant Agency of the Czech Republic,
grant #201/02/0594, and by the institutional grant MSM0021620839; the second author was supported by the Ministry of Science,
Technologies and Development of Republic of Serbia, grant no. 1227. 相似文献
8.
During irradiation of liquid samples of 1-vinylimidazole, 2-vinylnaphthalene, 2-vinylpyridine, 4-vinylpyridine and 1,1-diphenylethene
with positive muons, radicals of the type MuCH2ĊHAr (Ar=the appropriate aromatic group), and the MuCH2ĊPh2 radical were observed by transverse field μSR; the muon hyperfine couplings are considered in the context of the effectiveness
of the aryl groups in delocalising the unpaired electron. 相似文献
9.
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
10.
Juan Pablo Trelles Emil Pfender Joachim Heberlein 《Plasma Chemistry and Plasma Processing》2006,26(6):557-575
The dynamics of the electric arc inside a direct current non-transferred arc plasma torch are simulated using a three-dimensional, transient, equilibrium model. The fluid and electromagnetic equations are solved numerically in a fully coupled approach by a multiscale finite element method. Simulations of a torch operating with argon and argon–hydrogen under different operating conditions are presented. The model is able to predict the operation of the torch in steady and takeover modes without any further assumption on the reattachment process except for the use of an artificially high electrical conductivity near the electrodes, needed because of the equilibrium assumption. The results obtained indicate that the reattachment process in these operating modes may be driven by the movement of the arc rather than by a breakdown-like process. It is also found that, for a torch operating in these modes and using straight gas injection, the arc will tend to re-attach to the opposite side of its original attachment. This phenomenon seems to be produced by a net angular momentum on the arc due to the imbalance between magnetic and fluid drag forces. 相似文献