全文获取类型
收费全文 | 17705篇 |
免费 | 537篇 |
国内免费 | 339篇 |
专业分类
化学 | 11225篇 |
晶体学 | 121篇 |
力学 | 531篇 |
综合类 | 30篇 |
数学 | 2428篇 |
物理学 | 4246篇 |
出版年
2022年 | 180篇 |
2021年 | 216篇 |
2020年 | 212篇 |
2019年 | 217篇 |
2018年 | 200篇 |
2017年 | 174篇 |
2016年 | 398篇 |
2015年 | 347篇 |
2014年 | 433篇 |
2013年 | 955篇 |
2012年 | 775篇 |
2011年 | 897篇 |
2010年 | 635篇 |
2009年 | 610篇 |
2008年 | 848篇 |
2007年 | 870篇 |
2006年 | 738篇 |
2005年 | 770篇 |
2004年 | 746篇 |
2003年 | 711篇 |
2002年 | 758篇 |
2001年 | 495篇 |
2000年 | 442篇 |
1999年 | 354篇 |
1998年 | 273篇 |
1997年 | 256篇 |
1996年 | 258篇 |
1995年 | 260篇 |
1994年 | 263篇 |
1993年 | 214篇 |
1992年 | 190篇 |
1991年 | 202篇 |
1990年 | 206篇 |
1989年 | 179篇 |
1988年 | 151篇 |
1987年 | 151篇 |
1986年 | 143篇 |
1985年 | 250篇 |
1984年 | 268篇 |
1983年 | 181篇 |
1982年 | 209篇 |
1981年 | 182篇 |
1980年 | 190篇 |
1979年 | 167篇 |
1978年 | 140篇 |
1977年 | 199篇 |
1976年 | 179篇 |
1975年 | 154篇 |
1974年 | 136篇 |
1973年 | 126篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
V. Vittoria R. Russo F. De Candia P. L. Magagnini B. Bresci 《Journal of Polymer Science.Polymer Physics》1991,29(9):1163-1168
The transport properties of a side-chain liquid-crystalline polymer forming a smectic A phase have been investigated using dichloromethane as a permeant. Samples differing in the isotropization enthaoly were analyzed. A. Correlation between this thermal parameter and sorption has been found, while the diffusion coefficient is substantially the same in all samples. The results obtained can be explained in terms of a biphasis model in which a disordered permeable phase is present within the liquid-crystalline phase, which is impermeable to the diffusant molecules. 相似文献
102.
A series of hematites with up to 15 mol% Al substitution was converted to maghemites by reduction in the presence of organic matter, followed by slow oxidation. The maghemites formed were studied by Mössbauer spectroscopy in an external field of 60 kOe at 4 K. This technique allows the determination of site occupancy as well as the canting angle. The spectra are in agreement with a model having both vacancies and Al only in the octahedral sites and small canting angles for both sites. A small dipolar field at the tetrahedral sites was required to fit the line shape. The data indicate that about 10 mol% Al may be a solubility limit in maghemite. 相似文献
103.
Improved quantitation of 13-cis- and all-trans-acitretin in human plasma by normal-phase high-performance liquid chromatography. 总被引:1,自引:0,他引:1
E Meyer W E Lambert A P De Leenheer J P Bersaques A H Kint 《Journal of chromatography. A》1991,570(1):149-156
A reliable analytical method has been developed for measurement of 13-cis- and all-trans-acitretin (Neotigason) in human plasma by normal-phase high-performance liquid chromatography, with ultraviolet detection. Human plasma was obtained after centrifugation of whole blood samples and deproteinized by ethanolic denaturation. After liquid-liquid extraction with water-n-hexane, and aliquot ws chromatographed on a silica column using isocratic elution with n-hexane-methylsalicylate-acetic acid (200:18:0.6, v/v). The wavelength was set at 360 nm, and for plasma samples a limit of quantification of 3-4 ng/ml was obtained. All manipulations were carried out under dim light conditions to prevent photoisomerization. 相似文献
104.
Given an integer n ≥ 2, let λ(n) := (log n)/(log γ(n)), where γ(n) = Π
p|n p, stand for the index of composition of n, with λ(1) = 1. We study the distribution function of (λ(n) – 1) log n as n runs through particular sets of integers, such as the shifted primes, the values of a given irreducible cubic polynomial
and the shifted powerful numbers.
Research supported in part by a grant from NSERC.
Research supported by the Applied Number Theory Research Group of the Hungarian Academy of Science and by a grant from OTKA.
Professor M.V. Subbarao passed away on February 15, 2006.
Received: 3 March 2006 Revised: 28 October 2006 相似文献
105.
106.
Alain Lascoux 《Bulletin des Sciences Mathématiques》2006,130(4):354-359
Eliminating the arbitrary coefficients in the equation of a generic plane curve of order n by computing sufficiently many derivatives, one obtains a differential equation. This is a projective invariant. The first one, corresponding to conics, has been obtained by Monge. Sylvester, Halphen, Cartan used invariants of higher order. The expression of these invariants is rather complicated, but becomes much simpler when interpreted in terms of symmetric functions. 相似文献
107.
Yan Shun MA Qing Hua MENG Hong Yu SHI Yuan De LONG Tian Bao HUANG 《中国化学快报》2006,17(6):807-808
Dencichine (β-N-oxalyl-L-α, β-diaminopropionic acid, L-ODAP), a nonprotein amino acid, is a haemostatic agent present in important Chinese medicinal herbs such as Panax notoginseng, as well as other Panax species1. It was first isolated from the seeds … 相似文献
108.
Annals of Combinatorics - We give the Jacobian of any family of complete symmetric functions, or of power sums, in a finite number of variables. 相似文献
109.
Carolina Pereira De Souza Margareth Spangler Andrade Bernardo Ruegger Almeida Neves 《Microscopy and microanalysis》2002,8(6):509-517
In this work, effective, yet simple, recycling mechanisms for used scanning probe microscopy (SPM) tips were implemented. Comprising a tip profile characterization methodology and specific cleaning procedures, which decontaminate SPM tips whether the contamination nature is known or not, such routes were optimized during numerous tests with brand new, previously used, and already discarded categories of SPM tips. The results show that if the used tip suffered contamination only, but no physical damages, during its scanning lifetime, it becomes readily available for reutilization after the cleansing process, characterizing a recycling route. On the other hand, if the tip went through wear and breakages during its utilization, it still can be decontaminated, but may not be directly reutilized due to its inadequate physical profile. Nevertheless, the methodology developed in this work may yet be applied as part of a more complex recycling route. 相似文献
110.