全文获取类型
收费全文 | 1513180篇 |
免费 | 32000篇 |
国内免费 | 8316篇 |
专业分类
化学 | 655887篇 |
晶体学 | 20214篇 |
力学 | 74429篇 |
综合类 | 102篇 |
数学 | 240023篇 |
物理学 | 366991篇 |
无线电 | 195850篇 |
出版年
2021年 | 14776篇 |
2020年 | 17373篇 |
2019年 | 17505篇 |
2018年 | 13264篇 |
2016年 | 29639篇 |
2015年 | 21753篇 |
2014年 | 32761篇 |
2013年 | 78607篇 |
2012年 | 39237篇 |
2011年 | 35470篇 |
2010年 | 39317篇 |
2009年 | 44383篇 |
2008年 | 39048篇 |
2007年 | 35901篇 |
2006年 | 43051篇 |
2005年 | 35155篇 |
2004年 | 36710篇 |
2003年 | 34665篇 |
2002年 | 35703篇 |
2001年 | 34495篇 |
2000年 | 30946篇 |
1999年 | 28698篇 |
1998年 | 27356篇 |
1997年 | 27251篇 |
1996年 | 26853篇 |
1995年 | 24681篇 |
1994年 | 24134篇 |
1993年 | 23514篇 |
1992年 | 23093篇 |
1991年 | 23365篇 |
1990年 | 22108篇 |
1989年 | 21723篇 |
1988年 | 20851篇 |
1987年 | 19641篇 |
1986年 | 18438篇 |
1985年 | 25005篇 |
1984年 | 26197篇 |
1983年 | 22169篇 |
1982年 | 23629篇 |
1981年 | 22818篇 |
1980年 | 22064篇 |
1979年 | 21908篇 |
1978年 | 23195篇 |
1977年 | 22742篇 |
1976年 | 22339篇 |
1975年 | 21002篇 |
1974年 | 20607篇 |
1973年 | 21137篇 |
1972年 | 15342篇 |
1967年 | 13118篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Towards a Better Prediction of Cell Settling on Nanostructure Arrays—Simple Means to Complicated Ends 下载免费PDF全文
Nina Buch‐Månson Sara Bonde Jessica Bolinsson Trine Berthing Jesper Nygård Karen L. Martinez 《Advanced functional materials》2015,25(21):3246-3255
Vertical arrays of nanostructures (NSs) are emerging as promising platforms for probing and manipulating live mammalian cells. The broad range of applications requires different types of interfaces, but cell settling on NS arrays is not yet fully controlled and understood. Cells are both seen to deform completely into NS arrays and to stay suspended like tiny fakirs, which have hitherto been explained with differences in NS spacing or density. Here, a better understanding of this phenomenon is provided by using a model that takes into account the extreme membrane deformation needed for a cell to settle into a NS array. It is shown that, in addition to the NS density, cell settling depends strongly on the dimensions of the single NS, and that the settling can be predicted for a given NS array geometry. The predictive power of the model is confirmed by experiments and good agreement with cases from the literature. Furthermore, the influence of cell‐related parameters is evaluated theoretically and a generic method of tuning cell settling through surface coating is demonstrated experimentally. These findings allow a more rational design of NS arrays for the numerous exciting biological applications where the mode of cell settling is crucial. 相似文献
72.
73.
Synthesis of Small‐Sized,Porous, and Low‐Toxic Magnetite Nanoparticles by Thin POSS Silica Coating 下载免费PDF全文
Dr. Swee Kuan Yen D. Prathyusha Varma Wei Mei Guo Dr. Vincent H. B. Ho Dr. Vimalan Vijayaragavan Dr. Parasuraman Padmanabhan Prof. Kishore Bhakoo Prof. Subramanian Tamil Selvan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(10):3914-3918
In this communication, we report the synthesis of small‐sized (<10 nm), water‐soluble, magnetic nanoparticles (MNPs) coated with polyhedral oligomeric silsesquioxanes (POSS), which contain either polyethylene glycol (PEG) or octa(tetramethylammonium) (OctaTMA) as functional groups. The POSS‐coated MNPs exhibit superparamagnetic behavior with saturation magnetic moments (51–53 emu g?1) comparable to silica‐coated MNPs. They also provide good colloidal stability at different pH and salt concentrations, and low cytotoxicity to MCF‐7 human breast epithelial cells. The relaxivity data and magnetic resonance (MR) phantom images demonstrate the potential application of these MNPs in bioimaging. 相似文献
74.
75.
76.
77.
78.
Iodine(III)‐Catalyzed Rearrangements of Imides: A Versatile Route to α,α‐Dialkylated α‐Hydroxy Carboxylamides 下载免费PDF全文
Anna Ulmer Dr. Maciej Stodulski Stefanie V. Kohlhepp Christoph Patzelt Dr. Alexander Pöthig Dr. Wolfgang Bettray Dr. Tanja Gulder 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(4):1444-1448
A tertiary hydroxy group α to a carboxyl moiety comprises a key structural motif in many bioactive substances. With the herein presented metal‐free rearrangement of imides triggered by hypervalent λ3‐iodane, an easy and selective way to gain access to such a compound class, namely α,α‐disubstituted‐α‐hydroxy carboxylamides, was established. Their additional methylene bromide side chain constitutes a useful handle for rapid diversification, as demonstrated by a series of further functionalizations. Moreover, the in situ formation of an iodine(III) species under the reaction conditions was proven. Our findings clearly corroborate that hypervalent λ3‐benziodoxolones are involved in these organocatalytic reactions. 相似文献
79.
80.