全文获取类型
收费全文 | 6052篇 |
免费 | 439篇 |
国内免费 | 15篇 |
专业分类
化学 | 4840篇 |
晶体学 | 36篇 |
力学 | 74篇 |
数学 | 701篇 |
物理学 | 855篇 |
出版年
2024年 | 10篇 |
2023年 | 58篇 |
2022年 | 83篇 |
2021年 | 107篇 |
2020年 | 197篇 |
2019年 | 187篇 |
2018年 | 77篇 |
2017年 | 98篇 |
2016年 | 268篇 |
2015年 | 252篇 |
2014年 | 301篇 |
2013年 | 327篇 |
2012年 | 466篇 |
2011年 | 499篇 |
2010年 | 289篇 |
2009年 | 242篇 |
2008年 | 376篇 |
2007年 | 352篇 |
2006年 | 320篇 |
2005年 | 261篇 |
2004年 | 245篇 |
2003年 | 200篇 |
2002年 | 194篇 |
2001年 | 109篇 |
2000年 | 86篇 |
1999年 | 75篇 |
1998年 | 70篇 |
1997年 | 79篇 |
1996年 | 68篇 |
1995年 | 73篇 |
1994年 | 89篇 |
1993年 | 51篇 |
1992年 | 49篇 |
1991年 | 43篇 |
1990年 | 36篇 |
1989年 | 45篇 |
1988年 | 30篇 |
1987年 | 24篇 |
1986年 | 19篇 |
1985年 | 12篇 |
1984年 | 14篇 |
1983年 | 10篇 |
1982年 | 12篇 |
1981年 | 15篇 |
1980年 | 20篇 |
1979年 | 13篇 |
1978年 | 17篇 |
1977年 | 14篇 |
1976年 | 8篇 |
1975年 | 3篇 |
排序方式: 共有6506条查询结果,搜索用时 13 毫秒
31.
The π? p→e + e ? n and π+ n→e + e ? p reaction cross sections are calculated below and in the vicinity of the vector-meson (?0,ω) production threshold. These processes are largely responsible for the emission of e +e? pairs in pion-nucleus reactions and contribute to the dilepton spectra observed in relativistic heavy ion collisions. They are dominated by the decay of low-lying baryon resonances into vector-meson-nucleon channels. The vector mesons materialize subsequently into e + e? pairs. Using πN→?0 N and πN→ωN, amplitudes calculated in the center of mass energy interval 1.4 < √s<1.8 GeV, we compute the π? p→e + e ? n and π+ n→e + e ? p reaction cross sections in these kinematics. Below the vector-meson production threshold, the π0?ω interference in the e + e? channel appears largely destructive for the π? p→e + e ? n cross section and constructive for the π+ n→e + e ? p cross section. The pion beam and the HADES detector at GSI offer a unique possibility to measure these effects. Such data would provide strong constraints on the coupling of vector-meson-nucleon channels to low-lying baryon resonances. 相似文献
32.
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
33.
34.
35.
36.
37.
38.
39.
40.
Matthias Gelbrich 《Mathematische Nachrichten》1990,147(1):185-203
For a separable metric space (X, d) Lp Wasserstein metrics between probability measures μ and v on X are defined by where the infimum is taken over all probability measures η on X × X with marginal distributions μ and v, respectively. After mentioning some basic properties of these metrics as well as explicit formulae for X = R a formula for the L2 Wasserstein metric with X = Rn will be cited from [5], [9], and [21] and proved for any two probability measures of a family of elliptically contoured distributions. Finally this result will be generalized for Gaussian measures to the case of a separable Hilbert space. 相似文献