全文获取类型
收费全文 | 594篇 |
免费 | 11篇 |
专业分类
化学 | 338篇 |
晶体学 | 20篇 |
力学 | 8篇 |
数学 | 117篇 |
物理学 | 122篇 |
出版年
2023年 | 5篇 |
2020年 | 10篇 |
2017年 | 6篇 |
2016年 | 15篇 |
2015年 | 12篇 |
2014年 | 9篇 |
2013年 | 23篇 |
2012年 | 16篇 |
2011年 | 30篇 |
2010年 | 11篇 |
2009年 | 16篇 |
2008年 | 28篇 |
2007年 | 10篇 |
2006年 | 13篇 |
2005年 | 21篇 |
2004年 | 18篇 |
2003年 | 18篇 |
2002年 | 18篇 |
2001年 | 21篇 |
2000年 | 13篇 |
1999年 | 8篇 |
1998年 | 9篇 |
1997年 | 9篇 |
1996年 | 14篇 |
1995年 | 5篇 |
1994年 | 7篇 |
1993年 | 8篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 9篇 |
1989年 | 6篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 14篇 |
1984年 | 6篇 |
1983年 | 11篇 |
1982年 | 12篇 |
1981年 | 11篇 |
1980年 | 12篇 |
1979年 | 11篇 |
1978年 | 12篇 |
1977年 | 11篇 |
1976年 | 7篇 |
1975年 | 6篇 |
1974年 | 8篇 |
1973年 | 6篇 |
1972年 | 5篇 |
1970年 | 4篇 |
1927年 | 4篇 |
排序方式: 共有605条查询结果,搜索用时 31 毫秒
1.
A protocol to correct for intra‐ and interspecific variation in tail hair growth to align isotope signatures of segmentally cut tail hair to a common time line 下载免费PDF全文
2.
We prove that a bounded operator on a Banach lattice, satisfying a growth condition, is regular. Also, we prove that the generator of a C
0-semigroup on such a lattice for which such an operator exists is bounded. 相似文献
3.
4.
We consider a class of non-linear mixed integer programs with n integer variables and k continuous variables. Solving instances from this class to optimality is an NP-hard problem. We show that for the cases with
k=1 and k=2, every optimal solution is integral. In contrast to this, for every k≥3 there exist instances where every optimal solution takes non-integral values.
Received: August 2001 / Accepted: January 2002?Published online March 27, 2002 相似文献
5.
6.
E.J Onah L Häußler D Voigt C Froeck H Komber B.I Voit K Lunkwitz 《European Polymer Journal》2003,39(1):127-134
Soluble fluorine containing poly(amide-imide)s, PAI(1-4), were synthesized from diimide-dicarboxylic acid, 2,2-bis[N-(4-carboxyphenyl)-phthalimide-1,4-yl]hexafluoropropane with various diamines by direct polycondensation in N-methyl-2-pyrrolidone (NMP) containing CaCl2 and using triphenyl phosphite and pyridine as condensing agents. The polymers were readily soluble in aprotic polar solvents such as NMP, N,N-dimethylacetamide, dimethyl sulfoxide and tetrahydrofuran. Their Langmuir monolayers were studied at the air/water interface. The monolayers were generally stable at the water surface and could be reproducibly transferred onto solid substrates to build up Langmuir-Blodgett (LB) multilayers. The LB mono- and multilayers were characterized by ultra-violet/visible spectroscopy (UV-Vis), surface plasmon resonance, atomic force microscopy. 相似文献
7.
8.
Using a pump and test beam technique in the frequency domain with pump pulses in the nanosecond time range, the nonlinear transmission properties were investigated at room temperature in photosystem (PS) II membrane fragments and isolated light-harvesting chlorophyll a/b-protein preparations (LHC II preparations). In LHC II preparations and PS II membrane fragments, respectively, pump pulses of 620 nm and 647 nm cause a transmission decrease limited to a wavelength region in the nearest vicinity of the pump pulse wavelength (full width at half maximum ' 0.24 nm). In contrast, at 670 nm neither a transmission decrease nor a narrow band feature were observed. The data obtained for PS II membrane fragments and LHC II preparations at shorter wavelengths (620 nm, 647 nm) were interpreted in terms of excited state absorption of whole pigment-protein clusters within the light-harvesting antenna of photosystem II. The interpretation of the small transmission changes as homogeneously broadened lines led to a transversal relaxation time for chlorophyll in the clusters of about 4 ps. 相似文献
9.
Glass Formation and Properties of Chalcogenide Systems. IX. On the Structure of GeS/GeS2 and GeSe/GeSe2 Glasses Mole volume, glass transition temperature, and coefficient of thermal expansion were measured on glasses prepared by standardized conditions. Near the composition Ge2S3 and Ge2Se3 the properties show a singularity or point of inflexion, respectively. Random models of structure are inconsistent with such a behaviour. A model of higher chemical order is proposed which can explain the observed dependence of the glass properties on composition and is in accordance with radial distribution studies. 相似文献
10.
By means of a vacuum time-lag method, gas transport properties of apolyimide based on 2, 2- bis (3, 4- decarboxyphenyl ) hexafluoropropane dianhydride (6FDA )and meta- phenylenediamine (mPDA ) have been measured as a function of upstream pres-sure and temperature. The results show that no gas-induced plasticization occurs for thispolyimide in the upstream pressure range from 1 atm to 20atm. The temperature depen-dence of P and D can be described by the Arrhenius equations. The activation energiesof permeation and diffusion were obtained for the gas/polymer pair studied and correlatedwith the size of penetrant gas. 相似文献