全文获取类型
收费全文 | 1140篇 |
免费 | 51篇 |
国内免费 | 13篇 |
专业分类
化学 | 737篇 |
晶体学 | 1篇 |
力学 | 13篇 |
数学 | 259篇 |
物理学 | 194篇 |
出版年
2023年 | 12篇 |
2022年 | 6篇 |
2021年 | 19篇 |
2020年 | 23篇 |
2019年 | 29篇 |
2018年 | 29篇 |
2017年 | 18篇 |
2016年 | 42篇 |
2015年 | 26篇 |
2014年 | 43篇 |
2013年 | 66篇 |
2012年 | 84篇 |
2011年 | 84篇 |
2010年 | 63篇 |
2009年 | 59篇 |
2008年 | 73篇 |
2007年 | 74篇 |
2006年 | 59篇 |
2005年 | 73篇 |
2004年 | 58篇 |
2003年 | 33篇 |
2002年 | 46篇 |
2001年 | 16篇 |
2000年 | 17篇 |
1999年 | 22篇 |
1998年 | 14篇 |
1997年 | 7篇 |
1996年 | 21篇 |
1995年 | 10篇 |
1994年 | 16篇 |
1993年 | 7篇 |
1992年 | 9篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 5篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1985年 | 6篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1966年 | 1篇 |
1931年 | 1篇 |
1930年 | 1篇 |
1926年 | 1篇 |
1922年 | 1篇 |
排序方式: 共有1204条查询结果,搜索用时 734 毫秒
101.
Clifford MN Wu W Kirkpatrick J Jaiswal R Kuhnert N 《Rapid communications in mass spectrometry : RCM》2010,24(21):3109-3120
The chlorogenic acids of Gardeniae Fructus used traditionally as a Chinese herbal medicine (zhizi) have been investigated qualitatively by liquid chromatography/multi-stage mass spectrometry (LC/MS(4)). Twenty-nine chlorogenic acids were detected and twenty-five characterised to regioisomer level on the basis of their fragmentation, twenty-four for the first time from this source. Assignment to the level of individual regioisomers was possible for three caffeoylquinic acids, three dicaffeoylquinic acids, three sinapoylquinic acids, four caffeoyl-sinapoylquinic acids, two feruloyl-sinapoylquinic acids, one p-coumaroyl-sinapoylquinic acid, three (3-hydroxy, 3-methyl)glutaroylquinic acids, two (3-hydroxy, 3-methyl)glutaroyl-feruloylquinic acids, one (3-hydroxy, 3-methyl)glutaroyl-dicaffeoylquinic acid, and one (3-hydroxy, 3-methyl)glutaroyl-caffeoyl-feruloylquinic acid. Six (3-hydroxy, 3-methyl)glutaroyl-caffeoylquinic acids were detected and two were tentatively assigned as 3-caffeoyl-4-(3-hydroxy, 3-methyl)glutaroylquinic acid and 3-caffeoyl-5-(3-hydroxy, 3-methyl)glutaroylquinic acid. The (3-hydroxy, 3-methyl)glutaroyl residue modifies the mass spectral fragmentation behavior and elution sequence compared with the chlorogenic acids that contain only a cinnamic acid residue(s). Fourteen of these twenty-nine chlorogenic acids have not previously been reported from any source. 相似文献
102.
Parthey CG Matveev A Alnis J Bernhardt B Beyer A Holzwarth R Maistrou A Pohl R Predehl K Udem T Wilken T Kolachevsky N Abgrall M Rovera D Salomon C Laurent P Hänsch TW 《Physical review letters》2011,107(20):203001
We have measured the 1S-2S transition frequency in atomic hydrogen via two-photon spectroscopy on a 5.8 K atomic beam. We obtain f(1S-2S) = 2,466,061,413,187,035 (10) Hz for the hyperfine centroid, in agreement with, but 3.3 times better than the previous result [M. Fischer et al., Phys. Rev. Lett. 92, 230802 (2004)]. The improvement to a fractional frequency uncertainty of 4.2 × 10(-15) arises mainly from an improved stability of the spectroscopy laser, and a better determination of the main systematic uncertainties, namely, the second order Doppler and ac and dc Stark shifts. The probe laser frequency was phase coherently linked to the mobile cesium fountain clock FOM via a frequency comb. 相似文献
103.
Alexey Pak Matthias Steinhauser Nikolai Zerf 《The European Physical Journal C - Particles and Fields》2011,71(3):1602
We consider the Higgs boson production in the gluon-fusion channel to next-to-next-to-leading order within the Minimal Supersymmetric
Standard Model. In particular, we present analytical results for the matching coefficient of the effective theory and study
its influence on the total production cross section in the limit where the masses of all MSSM particles coincide. For supersymmetric
masses below 500 GeV it is possible to find parameters leading to a significant enhancement of the Standard Model cross section,
the K-factors, however, change only marginally. 相似文献
104.
Nikolai A. Kudryashov Dmitry I. SinelshchikovMaria V. Demina 《Physics letters. A》2011,375(7):1074-1079
The generalized Bretherton equation is studied. The Bäcklund transformations between traveling wave solutions of the generalized Bretherton equation and solutions of polynomial ordinary differential equation are constructed. The classification problem for meromorphic solutions of the latter equation is discussed. Several new families of exact solutions for the generalized Brethenton equation are given. 相似文献
105.
Nikolai Nikolov 《Annali di Matematica Pura ed Applicata》2014,193(6):1595-1605
Estimates for invariant distances of convexifiable, \(\mathbb{C }\) -convexifiable and planar domains are given. 相似文献
106.
Andrey E. Kovtanyuk Alexander Yu. Chebotarev Nikolai D. Botkin Karl-Heinz Hoffmann 《Journal of Mathematical Analysis and Applications》2014
The problem of optimal heat removal from a three-dimensional domain is considered. The specific of the study consist in accounting for the radiative heat transfer. The so-called P1 approximation of the radiative heat transfer equation is used, which reduces the model to a nonlinear elliptic system. A problem of optimal boundary control of this system is considered. The solvability of the control problem is proved, and necessary optimality conditions of first order are derived. Examples of non-singularity of these conditions are given. 相似文献
107.
Let V be a linear space over a field K of dimension n > 1, and let \({G \leq {\rm GL}(V)}\) be an irreducible linear group. In this paper we prove that the group G contains an element g such that rank \({(g - \alpha E_{n}) \geq \frac{n}{2}}\) for every \({\alpha \in K}\) , where E n is the identity operator on V. This estimate is sharp for any \({n = 2^{m}}\) . The existence of such an element implies that the conjugacy class of G in GL(V) intersects the big Bruhat cell \({B\dot{w}_{0}B}\) of GL(V) non-trivially (here B is a fixed Borel subgroup of G). The latter fact is equivalent to the existence of a complete flag \({\mathfrak{F}}\) such that the flags \({g(\mathfrak{F}), \mathfrak{F}}\) are in general position for some g ∈ G. 相似文献
108.
Irena Akhrem Dzhul’etta Avetisyan Lyudmila Afanas’eva Nikolai Kagramanov Pavel Petrovskii Alexander Orlinkov 《Tetrahedron letters》2010,51(6):907-911
A novel ‘alkane-like’ methodology for the direct and very simple one-pot functionalization of amides and an ester of 1-adamantanecarboxylic acid provides access to new and synthetically challenging 1,3-dicarbonyl-containing adamantanoid compounds with the same or different functional groups. 相似文献
109.
110.