全文获取类型
收费全文 | 1056篇 |
免费 | 20篇 |
国内免费 | 7篇 |
专业分类
化学 | 713篇 |
晶体学 | 24篇 |
力学 | 24篇 |
数学 | 174篇 |
物理学 | 148篇 |
出版年
2021年 | 5篇 |
2020年 | 5篇 |
2018年 | 11篇 |
2017年 | 7篇 |
2016年 | 10篇 |
2015年 | 12篇 |
2014年 | 13篇 |
2013年 | 37篇 |
2012年 | 61篇 |
2011年 | 56篇 |
2010年 | 30篇 |
2009年 | 32篇 |
2008年 | 59篇 |
2007年 | 55篇 |
2006年 | 53篇 |
2005年 | 46篇 |
2004年 | 41篇 |
2003年 | 47篇 |
2002年 | 51篇 |
2001年 | 17篇 |
2000年 | 27篇 |
1999年 | 19篇 |
1998年 | 22篇 |
1997年 | 19篇 |
1996年 | 26篇 |
1995年 | 20篇 |
1994年 | 14篇 |
1993年 | 20篇 |
1992年 | 10篇 |
1991年 | 13篇 |
1990年 | 14篇 |
1989年 | 10篇 |
1988年 | 15篇 |
1987年 | 10篇 |
1986年 | 10篇 |
1985年 | 14篇 |
1984年 | 12篇 |
1983年 | 12篇 |
1982年 | 7篇 |
1981年 | 13篇 |
1980年 | 13篇 |
1979年 | 13篇 |
1978年 | 7篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1975年 | 5篇 |
1969年 | 7篇 |
1967年 | 5篇 |
1966年 | 8篇 |
1928年 | 4篇 |
排序方式: 共有1083条查询结果,搜索用时 15 毫秒
101.
Martin Giera Jon S. B. de Vlieger Henk Lingeman Hubertus Irth Wilfried M. A. Niessen 《Rapid communications in mass spectrometry : RCM》2010,24(10):1439-1446
Structural elucidation of six regioisomers of mono‐N‐octyl derivatized neomycin is achieved using MSn (up to n = 4) on an ion trap time‐of‐flight (IT‐TOF) instrument equipped with electrospray ionization. The mixture of six derivatized neomycin analogues was generated by reductive amination in a shotgun synthetic approach. In parallel to the liquid chromatography/mass spectrometry (LC/MS) detection, the antibacterial activity of the neomycin regioisomers was tested by post‐column addition of buffer and bacterial inocula, subsequent microfractionation of the resulting mixture, incubation, and finally a chemiluminescence‐based bioactivity measurement based on the production of bacterial ATP. The MS‐based high‐resolution screening approach described can be applied in medicinal chemistry to help in designing and producing new antibiotic substances, which is particularly challenging due to the high functionality of most antibiotic substances, therefore requiring advanced (hyphenated) separation and detection techniques for compound mixtures. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
102.
103.
Quality management of laboratory medicine has become a hot topic at many conferences. Also, many national and international
organizations have created working groups and committees with the task of working out standards, guidelines or recommendations
for quality management of medical laboratories. We have observed that there is a great deal of interest not only from professional
and scientific organizations directly involved in medical laboratory tests, but also from accreditation and certification
bodies, from test laboratories in general, from in vitro diagnostic devices (IVD) manufacturers and their associations, and
from other medical laboratory suppliers. However, we found that all these parties were discussing from their own point of
view, without taking into account the position of other involved partners and that there was a need for creating a discussion
forum for quality management in clinical laboratories. So in 1995, we started the Antwerp conferences on quality (r)evolution
in clinical laboratories. The aim was to bring together all concerned partners and to establish a forum for brainstorming,
independently of any pressure group. The leitmotif for the Antwerp conferences (Fig. 1) is a chain model showing the interfaces
and relationships between all the partners involved in laboratory tests. During the conferences, this chain model has been
examined from different angles and a summary of the concepts evolving from the discussions can be found in the conference
abstracts and conference review reports in this journal. A Selection of ideas emerging from these conferences are presented
below.
Received: 5 October 1998 · Accepted: 20 October 1998 相似文献
104.
MartinHenk GeorgeA.Tsintsifas 《数学进展》2007,36(4):441-446
对于一个给定椭球,本文给出了它的任一全等椭球都包含一个整点的一个充分必要条件. 相似文献
105.
Henk D.L Hollmann János Körner Simon Litsyn 《Journal of Combinatorial Theory, Series A》1997,80(2):388-393
We show that if the collection of all binary vectors of lengthnis partitioned intokspheres, then eitherk2 orkn+2. Moreover, such partitions withk=n+2 are essentially unique. 相似文献
106.
107.
Henk A. Van Doren Ralph Van Der Geest Cornelis F. De Ruijter Richard M. Kellogg Hans Wynberg 《Liquid crystals》1990,8(1):109-121
A short review of the scope and limitations of liquid-crystalline behaviour in carbohydrate derivatives is presented. In order to investigate the influence of structure variations on the thermal behaviour of monosaccharide amphiphiles, six homologous series of D-glucose and 2-deoxy-D-glucose derivatives with an aminolinked n-alkyl chain were prepared. The observed thermal behaviour could be readily explained with the aid of a refinement of the qualitative model that was presented earlier [1]. All compounds were found to be mesogenic, and the observed mesophase was smectic Ad (i.e. a partially overlapping bilayer structure) in all cases. 相似文献
108.
109.
Methoxyethyliron complexes [Cp(CO)(L)Fe(CH2CHROMe)] (L = CO, P(OPh)3; R = H, Me) insert SO2 into the C---O single bond wih formation of metalated sulphonic acid esters [Cp(CO)(L)Fe(CH2-CHRSO2OMe)]. the insertion is stereospecific wih retention of configuration at carbon. The complexes [Cp(CO)3M(CH2CHRSO2OMe)] (M = Mo, W; R = H, Me) are obtained analogously. Oxidation of [Cp(CO)3W(CH2CH2SO2OMe)] wih iodine gives the ionic tungsten(IV) alkyl complex [Cp(CO)3(I)W(CH2CH2SO 2OMe)]+. Triphenylphosphine converts [Cp(CO)3Mo(CH2CHRSO2OMe)] into acyl complexes [Cp(CO)2(Ph3P)Mo(C(O)CH2CHRSO 2OMe)] (R = H, Me), which upon oxidation with CeIV in MeOH yield the diesters MeOC(O)CH2CHRSO2OMe. 相似文献
110.
Dynamical instability is studied in a deterministic dynamical system of Hamiltonian type composed of a tracer particle in a fluid of many particles. The tracer and fluid particles are hard balls (disks, in two dimensions, or spheres, in three dimensions) undergoing elastic collisions. The dynamical instability is characterized by the spectrum of Lyapunov exponents. The tracer particle is shown to dominate the Lyapunov spectrum in the neighborhoods of two limiting cases: the Lorentz-gas limit in which the tracer particle is much lighter than the fluid particles and the Rayleigh-flight limit in which the fluid particles have a vanishing radius and form an ideal gas. In both limits, a gap appears in the Lyapunov spectrum between the few largest Lyapunov exponents associated with the tracer and the rest of the Lyapunov spectrum. 相似文献