全文获取类型
收费全文 | 12554篇 |
免费 | 668篇 |
国内免费 | 1188篇 |
专业分类
化学 | 9853篇 |
晶体学 | 202篇 |
力学 | 150篇 |
综合类 | 65篇 |
数学 | 1846篇 |
物理学 | 2294篇 |
出版年
2023年 | 89篇 |
2022年 | 205篇 |
2021年 | 237篇 |
2020年 | 211篇 |
2019年 | 597篇 |
2018年 | 321篇 |
2017年 | 550篇 |
2016年 | 344篇 |
2015年 | 352篇 |
2014年 | 422篇 |
2013年 | 808篇 |
2012年 | 647篇 |
2011年 | 765篇 |
2010年 | 563篇 |
2009年 | 778篇 |
2008年 | 856篇 |
2007年 | 775篇 |
2006年 | 704篇 |
2005年 | 620篇 |
2004年 | 643篇 |
2003年 | 548篇 |
2002年 | 518篇 |
2001年 | 360篇 |
2000年 | 315篇 |
1999年 | 273篇 |
1998年 | 242篇 |
1997年 | 212篇 |
1996年 | 222篇 |
1995年 | 207篇 |
1994年 | 177篇 |
1993年 | 148篇 |
1992年 | 160篇 |
1991年 | 96篇 |
1990年 | 73篇 |
1989年 | 44篇 |
1988年 | 50篇 |
1987年 | 41篇 |
1986年 | 23篇 |
1985年 | 24篇 |
1984年 | 38篇 |
1983年 | 7篇 |
1982年 | 17篇 |
1981年 | 28篇 |
1980年 | 19篇 |
1979年 | 22篇 |
1978年 | 13篇 |
1977年 | 7篇 |
1976年 | 9篇 |
1974年 | 9篇 |
1973年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
91.
Andrea Bianco Giacomo Iardino Chiara Bertarelli Luciano Miozzo Giuseppe Zerbi 《Applied Surface Science》2007,253(20):8360-8364
Polyamide 6 (PA6) nanofibers were prepared from formic acid solutions by using electrospinning technique. The fibers were smooth, defects free and with diameters smaller than 200 nm. Small amounts of a perfluorinated acridine were added as dopant to the feed solution to modify the wettability of the fibers. The effect of doping on the contact angle values is well apparent. The contact angle values go from 50° of pure PA6 to 120° when 6% of acridine is added. A comparison between fibers and films of pure and doped polyamide 6 was carried out in order to determine the effect of morphology on wettability. Thermal annealing near the Tg of the polymer promoted the segregation of the molecules to the surface, reaching contact angles of 131° with smaller amounts (4%) of acridine. The surface segregation was also promoted by time aging. 相似文献
92.
A three-dimensional Ising-like model doped with anti-ferromagnetic (AFM) bonds is proposed to investigate the magnetic properties
of a doped triangular spin-chain system by using a Monte-Carlo simulation. The simulated results indicate that a steplike
magnetization behavior is very sensitive to the concentration of AFM bonds. A low concentration of AFM bonds can suppress
the stepwise behavior considerably, in accordance with doping experiments on Ca3Co2O6. The analysis of spin snapshots demonstrates that the AFM bond doping not only breaks the ferromagnetic ordered linear spin
chains along the hexagonal c-axis but also has a great influence upon the spin configuration in the ab-plane.
相似文献
93.
Aiden A. Bruen 《Acta Appl Math》2006,93(1-3):179-196
We survey some applications of finite fields to finite geometries in part A and to combinatorics and error-correcting codes in parts B and C. 相似文献
94.
Much of algebra and representation theory can be formulated in the general framework of tensor categories. The aim of this paper is to further develop this theory for braided tensor categories. Several results are established that do not have a substantial counterpart for symmetric tensor categories. In particular, we exhibit various equivalences involving categories of modules over algebras in ribbon categories. Finally, we establish a correspondence of ribbon categories that can be applied to, and is in fact motivated by, the coset construction in conformal quantum field theory. 相似文献
95.
96.
97.
D. V. R. Raju V. J. Rao S. Badrinarayanan A. B. Mandale S. K. Kulkarni 《Applied Physics A: Materials Science & Processing》1990,50(3):339-342
X-ray photoelectron spectroscopy (XPS) together with argon ion sputtering was used to investigate the interface of the Zn/CdSnAs2 system at various temperatures. The formation of an intermediate compound between Zn and As is proposed. The surface enrichment of Cd and Sn at 200 and 400°C is explained in terms of bond breaking and lattice strain theories.NCL Communication No. 4352 相似文献
98.
Using the ligand pyridazine-3,6-dicarboxylate (H2pzdc), a coordination polymer [Cd2(pzdc)2(H2O)4] was synthesized and characterized by elemental analysis, thermal analysis, IR and single-crystal X-ray diffraction. The complex crystallizes in the tetragonal system with space group I41/a. The crystallographic data are: a=1.470 6(4) nm, c=1.489 8(6) nm, V=3.222 0(19) nm3, Z=16, μ=2.725 mm-1, Dc=2.594 g·cm-3, R1=0.017 8, wR2=0.044 6. In the complex, the cadmium(Ⅱ) ions with the eight-coordinated dodecahedral geometry are linked by the pzdc ligands to generate one-dimensional chains, which are associated into the three-dimensional architecture via O-H…O hydrogen bonding. CCDC: 658853. 相似文献
99.
V anadium髨coordination com pound1is achievedby the hydrotherm al reaction of V2O5and ethyl6-m ethyl-4-hydroxy-3-quinolinecarboxylate(em hq)w ithwater as solvent.X-ray single crystal diffraction studyof com pound1(Fig.1)shows that com pound1crystal-lizes … 相似文献
100.
Cu(phen)22+与6-巯基嘌呤及DNA间的相互作用 总被引:3,自引:0,他引:3
在Tris-NaCl(pH=7.2)缓冲溶液中,应用伏安法、电子吸收光谱分析、溴化乙锭荧光分析、粘度测量和琼脂糖凝胶电泳等技术研究了Cu(phen)2^2+(phen=1,10-邻菲咯啉)与6-巯基嘌呤(6-MP)及DNA间的相互作用。结果表明,Cu(phen)2^2+与6-MP发生了明显的相互作用,其作用产物不仅与小牛胸腺DNA具有更强的相互作用,并且在H2O2和抗坏血酸存在下对质粒pBR322 DNA具有更强的断裂能力,与DNA的作用模式可能为部分插入模式。 相似文献