全文获取类型
收费全文 | 1767篇 |
免费 | 83篇 |
国内免费 | 5篇 |
专业分类
化学 | 1197篇 |
晶体学 | 17篇 |
力学 | 47篇 |
数学 | 244篇 |
物理学 | 350篇 |
出版年
2023年 | 18篇 |
2022年 | 40篇 |
2021年 | 53篇 |
2020年 | 31篇 |
2019年 | 39篇 |
2018年 | 32篇 |
2017年 | 29篇 |
2016年 | 64篇 |
2015年 | 54篇 |
2014年 | 61篇 |
2013年 | 100篇 |
2012年 | 80篇 |
2011年 | 92篇 |
2010年 | 59篇 |
2009年 | 53篇 |
2008年 | 79篇 |
2007年 | 106篇 |
2006年 | 93篇 |
2005年 | 65篇 |
2004年 | 81篇 |
2003年 | 58篇 |
2002年 | 51篇 |
2001年 | 37篇 |
2000年 | 26篇 |
1999年 | 22篇 |
1998年 | 23篇 |
1997年 | 21篇 |
1996年 | 20篇 |
1995年 | 24篇 |
1994年 | 21篇 |
1993年 | 23篇 |
1992年 | 18篇 |
1991年 | 18篇 |
1990年 | 17篇 |
1989年 | 16篇 |
1988年 | 11篇 |
1987年 | 20篇 |
1986年 | 13篇 |
1985年 | 17篇 |
1984年 | 11篇 |
1983年 | 9篇 |
1982年 | 14篇 |
1981年 | 14篇 |
1978年 | 16篇 |
1977年 | 14篇 |
1976年 | 9篇 |
1975年 | 7篇 |
1974年 | 13篇 |
1973年 | 8篇 |
1964年 | 5篇 |
排序方式: 共有1855条查询结果,搜索用时 15 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.
3.
4.
Xiaojuan Hao Camilla Nilsson Martin Jesberger Martina H. Stenzel Eva Malmstrm Thomas P. Davis Emma
stmark Christopher Barner‐Kowollik 《Journal of polymer science. Part A, Polymer chemistry》2004,42(23):5877-5890
The synthesis and characterization of novel first‐ and second‐generation true dendritic reversible addition–fragmentation chain transfer (RAFT) agents carrying 6 or 12 pendant 3‐benzylsulfanylthiocarbonylsulfanylpropionic acid RAFT end groups with Z‐group architecture based on 1,1,1‐hydroxyphenyl ethane and trimethylolpropane cores are described in detail. The multifunctional dendritic RAFT agents have been used to prepare star polymers of poly(butyl acrylate) (PBA) and polystyrene (PS) of narrow polydispersities (1.4 < polydispersity index < 1.1 for PBA and 1.5 < polydispersity index < 1.3 for PS) via bulk free‐radical polymerization at 60 °C. The novel dendrimer‐based multifunctional RAFT agents effect an efficient living polymerization process, as evidenced by the linear evolution of the number‐average molecular weight (Mn) with the monomer–polymer conversion, yielding star polymers with molecular weights of up to Mn = 160,000 g mol?1 for PBA (based on a linear PBA calibration) and up to Mn = 70,000 g mol?1 for PS (based on a linear PS calibration). A structural change in the chemical nature of the dendritic core (i.e., 1,1,1‐hydroxyphenyl ethane vs trimethylolpropane) has no influence on the observed molecular weight distributions. The star‐shaped structure of the generated polymers has been confirmed through the cleavage of the pendant arms off the core of the star‐shaped polymeric materials. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5877–5890, 2004 相似文献
5.
6.
B. Pignataro L. Chi S. Gao B. Anczykowski C. Niemeyer M. Adler H. Fuchs 《Applied Physics A: Materials Science & Processing》2002,74(3):447-452
Self-assembled oligomeric nanostructures consisting of bisbiotinylated DNA fragments connected by the protein streptavidin
(STV) are studied by dynamic scanning force microscopy (SFM) operating in air. A comparison of the images taken in repulsive
and attractive regimes is systematically made on DNA and STV structures. Stable and reproducible SFM images are obtained in
the attractive regime by using a special feedback circuit, called Q-control. On the other hand, when SFM is operating in the
repulsive regime, deformation of the structures that reduce the resolution and the image quality are clearly observable. The
heights of both DNA and STV have been measured as a function of the tip/molecule interaction forces. This study offers the
possibility to suggest a different mechanical behavior of DNA with respect to STV.
Received: 24 July 2001 / Accepted: 3 December 2001 / Published online: 4 March 2002 相似文献
7.
8.
Ulf Pindur Ludwig Pfeuffer Manfred Eitel Martina Rogge Manfred Haber 《Monatshefte für Chemie / Chemical Monthly》1991,122(4):291-298
Summary Diels-Alder reactions of 2- and 3-vinylindoles with aryne, 1,4-benzo- and 1,4-naphtho-quinone lead to new six-ring annellated carbazoles. Molecular modeling studies predict that the compounds with coplanar framework are able to intercalate with the B-DNA. 相似文献
9.
We develop the theory of the nonadiabatic geometric phase, in both the Abelian and non-Abelian cases, in quaternionic Hilbert space. 相似文献
10.
M. E. Carlotti S. Sapino R. Cavalli M. Trotta F. Trotta K. Martina 《Journal of inclusion phenomena and macrocyclic chemistry》2007,57(1-4):445-450
This work deals with the formation of inclusion complexes between cinnamaldehyde and two synthetic alkylcarbonates of γ-cyclodextrin, namely ethylcarbonate-γ-CD and octylcarbonate-γ-CD. Complexation was monitored by phase-solubility studies, by FT-IR spectroscopy and by DSC and TG analysis.
The diffusion of cinnamaldehyde through a cellulose membrane was investigated in the absence and in the presence of each of
the two γ-CD alkylcarbonates. Studies on photostability and stability over time were carried out on different cosmetic formulations
containing pure cinnamaldehyde or an equivalent amount of cinnamaldehyde complexed with the two alkylcarbonates.
Phase-solubility diagrams, DSC, FTIR and TGA analysis suggested the formation of inclusion complexes. The diffusion of cinnamaldehyde
through the cellulose membrane decreased in the presence of the two alkylcarbonates confirming the interaction of this molecule
with the inclusion agents.
Moreover the stability of cinnamaldehyde to light and heat resulted increased by complexing this fragrance material with the
two alkylcarbonates. 相似文献