全文获取类型
收费全文 | 1814篇 |
免费 | 104篇 |
国内免费 | 4篇 |
专业分类
化学 | 1308篇 |
晶体学 | 18篇 |
力学 | 61篇 |
数学 | 169篇 |
物理学 | 366篇 |
出版年
2023年 | 12篇 |
2022年 | 19篇 |
2021年 | 36篇 |
2020年 | 38篇 |
2019年 | 34篇 |
2018年 | 34篇 |
2017年 | 21篇 |
2016年 | 47篇 |
2015年 | 60篇 |
2014年 | 56篇 |
2013年 | 100篇 |
2012年 | 98篇 |
2011年 | 117篇 |
2010年 | 76篇 |
2009年 | 81篇 |
2008年 | 119篇 |
2007年 | 117篇 |
2006年 | 93篇 |
2005年 | 80篇 |
2004年 | 80篇 |
2003年 | 77篇 |
2002年 | 66篇 |
2001年 | 32篇 |
2000年 | 24篇 |
1999年 | 21篇 |
1998年 | 19篇 |
1997年 | 13篇 |
1996年 | 16篇 |
1995年 | 14篇 |
1994年 | 19篇 |
1993年 | 19篇 |
1992年 | 20篇 |
1991年 | 11篇 |
1990年 | 12篇 |
1989年 | 14篇 |
1988年 | 17篇 |
1987年 | 14篇 |
1986年 | 8篇 |
1985年 | 18篇 |
1984年 | 25篇 |
1983年 | 12篇 |
1982年 | 21篇 |
1981年 | 18篇 |
1980年 | 18篇 |
1979年 | 15篇 |
1978年 | 10篇 |
1977年 | 16篇 |
1976年 | 6篇 |
1975年 | 10篇 |
1973年 | 6篇 |
排序方式: 共有1922条查询结果,搜索用时 31 毫秒
141.
C. Merlatti F.X. Perrin E. Aragon A. Margaillan 《Polymer Degradation and Stability》2008,93(5):896-903
Depth-profiling by Fourier transform infrared (FTIR) spectroscopy, dynamic mechanical analysis (DMA), microhardness and scanning electron microscopy (SEM) observations have been used to monitor degradation chemistries in two-package acrylic–urethane coatings when exposed to different exposure conditions. Three artificial and three natural weathering protocols (QUV, ASTM D5894, ISO20340, Pipady (south of France), Bandol (south of France) and Kure Beach (USA)) were selected for this study. The same chemical events were found to occur under all conditions, particularly under natural and artificial exposures. Both loss of the amide II band at 1520 cm−1 and carbonyl growth occurred but at relatively low rate owing to the presence of hindered-amine light stabilizers in the film. A less typical loss of urea biuret linkages also occurs during all exposures and results in a change in the balance between urethane and urea links across the depth of the film during weathering. The chemical degradation of the polymer matrix involves the formation of species that are readily ablated from the surface and results in loss of gloss, increase in hardness and a rougher topology. The dramatic loss of gloss observed after Pipady and Bandol exposures show that loss of gloss should not be systematically correlated to the advance in chemical degradation. 相似文献
142.
Nawel Cheikh Didier Villemin Nathalie Bar Jean-François Lohier Nourredine Choukchou-Braham Bachir Mostefa-Kara Jana Sopkova 《Tetrahedron》2013,69(3):1234-1247
In the course of our studies on Cerpegin analogues synthesis, a serendipitous reactivity of enaminolactone nitrile has been observed. Instead of expecting iminocerpegins, we have gained new class of substituted 2-aminopyridines. The methodology has been applied on a wide range of primary amines, as aliphatic, aromatic, heteroaromatic and also, diamines, hydrazines and chiral amines. 相似文献
143.
144.
Th. R. Cunningham R. J. Price St. G. Simpson W. C. Schumb P. Klinger O. Schliessmann D. R. Nijk H. Bart G. v. Hevesy R. Hobbie A. Asmanow P. H. M. P. Brinton R. B. Ellestad G. Scagliarini P. Pratesi I. M. Kolthoff J. J. Lingane J. Volmar Mathis J. Perrin E. Bayle R. Fabre H. George H. Gräven G. Canneri und L. Fernandes 《Fresenius' Journal of Analytical Chemistry》1934,99(3-4):113-129
Ohne Zusammenfassung 相似文献
145.
C McGregor C Perrin M Monck P Camilleri A J Kirby 《Journal of the American Chemical Society》2001,123(26):6215-6220
We report a new class of amphiphilic gemini surfactants as vehicles for gene delivery into cells, and the beginnings of a systematic structure-activity study. Preliminary results suggest that combining gemini surfactants with dioleoylphosphatidylethanolamine (DOPE) should allow the preparation of liposomes of various sizes and lipid compositions. Control of such colloidal changes could be as significant as the changes in the molecular composition of the gemini surfactants in delivering optimum gene expression in animal models. 相似文献
146.
A solution to the problem stated in the title is given by treating the porous matrix as a homogeneous material obeying the Gurson-Tvergaard model. As a first application, it is shown that the flow stress under hydrostatic loading of a material containing two populations of voids with very different sizes is almost the same as that of a material with only one population of voids and the same total porosity. As a second application, a self-consistent method is used to derive a value for the parameter introduced by Tvergaard in the original Gurson model to account for the interactions between cavities. Other models are also considered and shown to fail to satisfy the self-consistency requirement, whatever the value chosen for the parameter characterizing interactions between voids. 相似文献
147.
148.
149.
Didier Bresch Benoît Desjardins Emmanuel Grenier 《Journal of Functional Analysis》2008,254(5):1269-1281
In this paper we consider linear Schrödinger operator with double or resonant eigenvalues. The main result is the bound of the measure (in a suitable space of functions) of the potentials leading to such double or resonant eigenvalues. Namely we present measure type estimates evaluating neighborhoods of the so-called double or resonant set. 相似文献
150.
M. Bonesini E. Bonvin R. Bopp L. J. Carroll A. J. Cass D. Cavalli G. Costa S. U. Chung M. Donnat P. A. Dorsaz M. Feliks J. R. Fischer L. Fluri F. Gianotti S. Jack J. N. Jackson M. N. Kienzle-Focacci J. G. Lynch L. Mandelli M. Martin L. Mathys A. Maxwell M. Mazzanti P. J. Negus S. Pensotti-Rancoita L. Perini D. Perrin R. W. Poultney W. H. Range L. Rosselet S. W. Snow A. S. Thompson R. M. Turnbull J. Wells M. Werlen WA Collaboration 《Zeitschrift fur Physik C Particles and Fields》1989,44(1):71-78
The structure of events associated with the production of direct photons in π? p, π+ p andpp reactions of 280 GeV/c has been studied using data from the WA 70 experiment at the CERN SPS. Results are presented on the distributions of the fractional momenta of the colliding partons and on the fragmentation of the recoil jet and a comparison is made with predictions using the structure functions of Duke and Owens in the Lund Monte Carlo with string fragmentation. 相似文献