全文获取类型
收费全文 | 6207篇 |
免费 | 385篇 |
国内免费 | 15篇 |
专业分类
化学 | 4904篇 |
晶体学 | 38篇 |
力学 | 83篇 |
数学 | 705篇 |
物理学 | 877篇 |
出版年
2024年 | 10篇 |
2023年 | 58篇 |
2022年 | 83篇 |
2021年 | 108篇 |
2020年 | 197篇 |
2019年 | 187篇 |
2018年 | 78篇 |
2017年 | 98篇 |
2016年 | 267篇 |
2015年 | 252篇 |
2014年 | 300篇 |
2013年 | 335篇 |
2012年 | 471篇 |
2011年 | 501篇 |
2010年 | 293篇 |
2009年 | 241篇 |
2008年 | 379篇 |
2007年 | 357篇 |
2006年 | 328篇 |
2005年 | 262篇 |
2004年 | 244篇 |
2003年 | 202篇 |
2002年 | 194篇 |
2001年 | 111篇 |
2000年 | 93篇 |
1999年 | 79篇 |
1998年 | 69篇 |
1997年 | 79篇 |
1996年 | 69篇 |
1995年 | 76篇 |
1994年 | 89篇 |
1993年 | 54篇 |
1992年 | 53篇 |
1991年 | 45篇 |
1990年 | 39篇 |
1989年 | 48篇 |
1988年 | 34篇 |
1987年 | 25篇 |
1986年 | 20篇 |
1985年 | 11篇 |
1984年 | 14篇 |
1983年 | 9篇 |
1982年 | 13篇 |
1981年 | 17篇 |
1980年 | 20篇 |
1979年 | 17篇 |
1978年 | 16篇 |
1977年 | 15篇 |
1976年 | 9篇 |
1866年 | 7篇 |
排序方式: 共有6607条查询结果,搜索用时 15 毫秒
21.
Über Sesquiselenide der Lanthanoide: Einkristalle von Ce2Se3 im C‐, Gd2Se3 im U‐ und Lu2Se3 im Z‐Typ
On Sesquiselenides of the Lanthanoids: Single Crystals of C‐type Ce2Se3, U‐type Gd2Se3, and Z‐type Lu2Se3 Single crystals of lanthanoid sesquiselenides (M2Se3; here: M = Ce, Gd, Lu) are accessible through conversion of the elements (lanthanoid and selenium) in molar ratios of 2:3 within seven days at 850 °C from evacuated silica ampoules if equimolar amounts of NaCl serve as a flux. In the case of Ce2Se3 (a = 897.74(6) pm) und Gd2Se3 (a = 872.56(5) pm) the cubic C‐type (I4¯3d, Z = 5.333) forms as dark red beads, whereas the orthorhombic Z‐type (Fddd, Z = 16) emerges for Lu2Se3 (a = 1125.1(1), b = 798.06(8), c = 2387.7(2) pm) as orange‐yellow bricks. Upon oxidation of monochloride hydrides (MClHx or AyMClHx; M = Ce, Gd, Lu; x = 1; A = Li, Na; y = 0.5) with selenium in arc‐welded tantalum ampoules the same main products appear with C‐Ce2Se3 and Z‐Lu2Se3, even with a surplus of NaCl or LiCl as fluxing agent. In the case of Gd2Se3, however, black‐red needles of the orthorhombic U‐type (Pnma, Z = 4; a = 1118.2(1), b = 403.48(4); c = 1097.1(1) pm) are yielded instead of C‐Gd2Se3. C‐Ce2Se3 crystallizes in a cation‐deficient Th3P4‐type structure (Ce2S3 type) according to Ce2.667□0.333Se4 (Z = 4) or with Z = 5.333 for the empirical formula Ce2Se3. Here, Ce3+ is coordinated by eight Se2— anions trigon‐dodecahedrally. In U‐Gd2Se3 (U2S3 type) two crystallographically independent Gd3+ cations with coordination numbers of 7 (Gd1) and 7+1 (Gd2), respectively, are present, exhibiting mono‐ or bicapped trigonal prisms as coordination polyhedra. The crystal structure of Z‐Lu2Se3 (Sc2S3 type) shows two different Lu3+ cations as well, which now both reside in octahedral coordination of six Se2— anions each. 相似文献
22.
23.
24.
M.C. Robinson D.J. Morris P.D. Hayenga J.H. Cho C.D. Richards R.F. Richards D.F. Bahr 《Applied Physics A: Materials Science & Processing》2006,85(2):135-140
Piezoelectric membranes have been fabricated that incorporate a gold bottom electrode with an adhesion layer of titanium–tungsten (10:90 wt. %). For solution-deposited acetic acid based lead zirconate titanate (HoAc-PZT) with a Zr:Ti ratio of 40:60, the film’s average piezoelectric coefficient, e31, is -5.31 C/m2, with a dielectric constant of 814 at 200 Hz, which is similar to values for platinum bottom electrodes. The PZT structure remains columnar on both types of bottom electrodes. Initial fabrication attempts resulted in cracking that initiated in the PZT layer of the structure. X-ray photoelectron spectroscopy was utilized to establish how processing affects diffusion throughout the composite membrane structure. Crack-free membranes were fabricated and tested. This paper discusses the performance properties and piezoelectric fatigue results for these membranes. PACS 77.84.-s; 77.84.Lf 相似文献
25.
26.
27.
28.
29.
30.
The equilibrium phase behavior of a binary mixture of charged colloids and neutral, nonadsorbing polymers is studied within free-volume theory. A model mixture of charged hard-sphere macroions and ideal, coarse-grained, effective-sphere polymers is mapped first onto a binary hard-sphere mixture with nonadditive diameters and then onto an effective Asakura-Oosawa model [S. Asakura and F. Oosawa, J. Chem. Phys. 22, 1255 (1954)]. The effective model is defined by a single dimensionless parameter-the ratio of the polymer diameter to the effective colloid diameter. For high salt-to-counterion concentration ratios, a free-volume approximation for the free energy is used to compute the fluid phase diagram, which describes demixing into colloid-rich (liquid) and colloid-poor (vapor) phases. Increasing the range of electrostatic interactions shifts the demixing binodal toward higher polymer concentration, stabilizing the mixture. The enhanced stability is attributed to a weakening of polymer depletion-induced attraction between electrostatically repelling macroions. Comparison with predictions of density-functional theory reveals a corresponding increase in the liquid-vapor interfacial tension. The predicted trends in phase stability are consistent with observed behavior of protein-polysaccharide mixtures in food colloids. 相似文献