全文获取类型
收费全文 | 6916篇 |
免费 | 232篇 |
国内免费 | 35篇 |
专业分类
化学 | 4861篇 |
晶体学 | 122篇 |
力学 | 113篇 |
综合类 | 1篇 |
数学 | 816篇 |
物理学 | 1270篇 |
出版年
2023年 | 54篇 |
2022年 | 70篇 |
2021年 | 93篇 |
2020年 | 161篇 |
2019年 | 155篇 |
2018年 | 88篇 |
2017年 | 88篇 |
2016年 | 195篇 |
2015年 | 199篇 |
2014年 | 199篇 |
2013年 | 277篇 |
2012年 | 377篇 |
2011年 | 445篇 |
2010年 | 247篇 |
2009年 | 257篇 |
2008年 | 393篇 |
2007年 | 407篇 |
2006年 | 392篇 |
2005年 | 364篇 |
2004年 | 308篇 |
2003年 | 217篇 |
2002年 | 232篇 |
2001年 | 116篇 |
2000年 | 108篇 |
1999年 | 73篇 |
1998年 | 96篇 |
1997年 | 83篇 |
1996年 | 105篇 |
1995年 | 101篇 |
1994年 | 57篇 |
1993年 | 71篇 |
1992年 | 68篇 |
1991年 | 59篇 |
1990年 | 70篇 |
1989年 | 49篇 |
1988年 | 50篇 |
1987年 | 50篇 |
1986年 | 45篇 |
1985年 | 61篇 |
1984年 | 46篇 |
1983年 | 41篇 |
1982年 | 37篇 |
1981年 | 53篇 |
1980年 | 50篇 |
1979年 | 30篇 |
1978年 | 35篇 |
1977年 | 39篇 |
1976年 | 34篇 |
1973年 | 42篇 |
1971年 | 27篇 |
排序方式: 共有7183条查询结果,搜索用时 15 毫秒
1.
Fe(II)--Fe(III) hydroxy-chloride, -sulphate and -carbonate were prepared by oxidation of a ferrous hydroxide precipitate in anion-containing aqueous solutions. The compounds are characterized by monitoring the redox potential Eh and the pH of stochiometric suspension vs time with the appropriate concentration ratios. X-ray diffraction allows us to characterize the crystal structure by distinguishing “green rust one” (GR1) from “green rust two” (GR2). Since green rusts (GRs) are of a pyroaurite-sjögrenite-like structure, i.e., consisting of intercalated foreign anions and water molecules in the interlayers between the brucite-like layers of Fe(OH)2, their chemical formulae can be determined from the Mössbauer spectra. Three quadrupole doublets are observed: D1 and D2 correspond to a ferrous state with isomershift IS of about 1.27 mm s-1 and quadrupole splittings QS of about 2.85 and 2.60 mm s-1, respectively, whereas D3 corresponds to a ferric state with IS and QS of about 0.4 mm s-1. The hyperfine parameters of these doublets are similar from one green rust to another but their intensity ratios vary considerably. Finally, Eh and pH equilibrium diagrams of the Fe species in the presence of chloride, sulphate and carbonate anions contained within the water solution are drawn and the thermodynamic conditions of existence and degrees of oxidation of green rusts are discussed. 相似文献
2.
Simon R. Blackburn 《Journal of Combinatorial Theory, Series A》2006,113(7):1572-1581
The paper contains proofs of the following results. For all sufficiently large odd integers n, there exists a set of 2n−1 permutations that pairwise generate the symmetric group Sn. There is no set of 2n−1+1 permutations having this property. For all sufficiently large integers n with n≡2mod4, there exists a set of 2n−2 even permutations that pairwise generate the alternating group An. There is no set of 2n−2+1 permutations having this property. 相似文献
3.
Journal of Statistical Physics - Let V 0be a real-valued function on [0,∞) and V∈L 1([0,R]) for all R&;gt;0 so that H(V 0)=? $\frac{{d^2 }}{{dx^2 }}$ +V 0in L 2([0,∞))... 相似文献
4.
5.
The existence of a Nash equilibrium in the undiscounted repeated two-person game of incomplete information on one side is
established. The proof depends on a new topological result resembling in some respect the Borsuk-Ulam theorem. 相似文献
6.
We generalize several results on bounded analytic interpolation of Fitzgerald and Horn, which work by majorization by positive
definite kernels, to the cases of several complex variables and operator-valued interpolation. Using a lemma of Kolmogorov,
we complement a simplification due to Szafraniec in the proofs of the theorems.
Received: November 21, 2006. Accepted: August 03, 2007. 相似文献
7.
A. Maignan Ch. Simon V. Caignaert B. Raveau 《Zeitschrift für Physik B Condensed Matter》1995,99(1):305-310
The exploration of the magnetic and transport properties of four series of manganese perovskites, Pr0.7Ca0.34−xAxMnO3−δ (A=Sr, Ba), Pr0.7−xLaxCa0.3 MnO3−δ and Pr0.66Ca0.34−x
SrxMnO3−δ has allowed four phases with colossal magnetoresistive (CMR) properties to be isolated: Pr0.7Ca0.25Sr0.025MnO3−δ and Pr0.66Ca0.26Sr0.08MnO3−δ that exhibit a variation of resistance of 2.5. 107% and 109% at μ0 H=5 T for T=88 K and 50 K respectively, Pr0.58La0.12Ca0.3 MnO3−δ that exhibits a variation of 6.106% for μ0 H=5 T at T=80 K and Pr0.7Ba0.025Ca0.275MnO3−δ for which a resistance variation of 5.109%, at T=50 K, for μ0 H=5 T is evidenced. for each compound of this series except the barium phase, one observes that the temperature Tmax, which corresponds to the resistance maximum on the R(T) curves in zero magnetic field, increases dramatically as the mean
size of the interpolated cations increases, and that the CMR effect correlatively decreases dramatically. The comparison of
the two series Pr0.7Ca0.3−xSrxMnO3−δ and Pr0.66Ca0.34−xSrxMnO3−δ shows also the crucial role of the hole carrier density: for a same mean ionic radius of the interpolated cation Tmax is decreased of about 50 K by introducing 0.034 hole per Mn mole. 相似文献
8.
Simon French 《The Journal of the Operational Research Society》1994,45(11):1341-1341
9.
Simon Thomas 《Archive for Mathematical Logic》1998,37(7):483-493
We study the relationship between the cofinality of the infinite symmetric group and the cardinal invariants and . In particular, we prove the following two results.
Theorem 0.1
It is consistent with
ZFC
that there exists a simple
$P_{\omega_{1}}$
-point and that
$c(Sym(\omega)) = \omega_{2} = 2^{\omega}$
.
Theorem 0.2
If there exist both a simple
$P_{\omega_{1}}$
-point and a
$P_{\omega_{2}}$
-point, then
$c(Sym(\omega)) = \omega_{1}$
.
Received: 7 March 1996 相似文献
10.
P. D. Morley 《Nuclear Physics A》1987,470(3-4):547-557
We compute delta electroproduction in nuclei using a relativistic nuclear model. Iron is predicted to have the largest per nucleon cross section and narrowest width, but the variation in A is no larger than an 18% effect. Predictions are made for the SLAC NPAS NE5 experiment and a recently completed Bates laboratory experiment. 相似文献