全文获取类型
收费全文 | 1166篇 |
免费 | 35篇 |
国内免费 | 5篇 |
专业分类
化学 | 831篇 |
晶体学 | 6篇 |
力学 | 29篇 |
数学 | 193篇 |
物理学 | 147篇 |
出版年
2022年 | 20篇 |
2021年 | 16篇 |
2020年 | 27篇 |
2019年 | 30篇 |
2018年 | 11篇 |
2017年 | 15篇 |
2016年 | 21篇 |
2015年 | 24篇 |
2014年 | 40篇 |
2013年 | 43篇 |
2012年 | 70篇 |
2011年 | 81篇 |
2010年 | 40篇 |
2009年 | 42篇 |
2008年 | 48篇 |
2007年 | 78篇 |
2006年 | 67篇 |
2005年 | 60篇 |
2004年 | 61篇 |
2003年 | 50篇 |
2002年 | 56篇 |
2001年 | 14篇 |
2000年 | 21篇 |
1999年 | 15篇 |
1998年 | 7篇 |
1997年 | 15篇 |
1996年 | 13篇 |
1995年 | 25篇 |
1994年 | 21篇 |
1993年 | 11篇 |
1992年 | 13篇 |
1991年 | 7篇 |
1990年 | 9篇 |
1988年 | 6篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 9篇 |
1984年 | 9篇 |
1983年 | 12篇 |
1982年 | 7篇 |
1981年 | 13篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1975年 | 8篇 |
1974年 | 4篇 |
1973年 | 4篇 |
1969年 | 4篇 |
排序方式: 共有1206条查询结果,搜索用时 93 毫秒
121.
122.
123.
Next‐Generation o‐Nitrobenzyl Photolabile Groups for Light‐Directed Chemistry and Microarray Synthesis 下载免费PDF全文
Nicole Kretschy Ann‐Katrin Holik Prof. Veronika Somoza Dr. Klaus‐Peter Stengele Prof. Mark M. Somoza 《Angewandte Chemie (International ed. in English)》2015,54(29):8555-8559
Light as an external trigger is a valuable and easily controllable tool for directing chemical reactions with high spatial and temporal accuracy. Two o‐nitrobenzyl derivatives, benzoyl‐ and thiophenyl‐NPPOC, undergo photo‐deprotection with significantly improved efficiency over that of the commonly used NPPOC group. The two‐ and twelvefold increase in photo‐deprotection efficiency was proven using photolithograph synthesis of microarrays. 相似文献
124.
Nannocystin A: an Elongation Factor 1 Inhibitor from Myxobacteria with Differential Anti‐Cancer Properties 下载免费PDF全文
Philipp Krastel Silvio Roggo Markus Schirle Nathan T. Ross Francesca Perruccio Peter Aspesi Jr. Thomas Aust Kathrin Buntin David Estoppey Brigitta Liechty Felipa Mapa Klaus Memmert Howard Miller Xuewen Pan Ralph Riedl Christian Thibaut Jason Thomas Trixie Wagner Eric Weber Xiaobing Xie Esther K. Schmitt Dr. Dominic Hoepfner 《Angewandte Chemie (International ed. in English)》2015,54(35):10149-10154
Cultivation of myxobacteria of the Nannocystis genus led to the isolation and structure elucidation of a class of novel cyclic lactone inhibitors of elongation factor 1. Whole genome sequence analysis and annotation enabled identification of the putative biosynthetic cluster and synthesis process. In biological assays the compounds displayed anti‐fungal and cytotoxic activity. Combined genetic and proteomic approaches identified the eukaryotic translation elongation factor 1α (EF‐1α) as the primary target for this compound class. Nannocystin A ( 1 ) displayed differential activity across various cancer cell lines and EEF1A1 expression levels appear to be the main differentiating factor. Biochemical and genetic evidence support an overlapping binding site of 1 with the anti‐cancer compound didemnin B on EF‐1α. This myxobacterial chemotype thus offers an interesting starting point for further investigations of the potential of therapeutics targeting elongation factor 1. 相似文献
125.
Reactions of a,ß‐unsaturated N‐benzenesulfonyl Imine – N‐[(2E)‐3‐phenyl‐2‐propen‐1‐ylidene]benzenesulfonamide with Methyllithium 下载免费PDF全文
α,β‐Unsaturated N‐benzenesulfonyl imine 1 was treated with 1.1 eq methyllithium to afford 1,2‐addition adduct as a sole product. However, when compound 1 was treated with 2 eq MeLi, 1,2‐addition product, benzenesulfonamide derivative 3 and 2H‐1,2‐benzothiazine 1,1‐dioxide derivatives 4 and 5 were isolated. 相似文献
126.
127.
Tran AB Melly GC Doucette R Ashcraft B Sebren LJ Havko N Young JC O'Neil GW 《Organic & biomolecular chemistry》2011,9(22):7671-7674
A convergent and scalable synthesis of the archazolid western hemisphere has been completed. The V-ATPase inhibitory activity of this compound along with a previously prepared eastern domain was then tested using a convenient Arabidopsis-based V-ATPase assay. 相似文献
128.
Text
Over a period of sixteen years elliptic curve cryptography went from being an approach that many people mistrusted or misunderstood to being a public key technology that enjoys almost unquestioned acceptance. We describe the sometimes surprising twists and turns in this paradigm shift, and compare this story with the commonly accepted Ideal Model of how research and development function in cryptography. We also discuss to what extent the ideas in the literature on “social construction of technology” can contribute to a better understanding of this history.Video
For a video summary of this paper, please visit http://www.youtube.com/watch?v=HHFFvfDoTK4. 相似文献129.
This study took place at a mid‐sized, Midwestern university located in a mid‐sized town. The researchers developed the BAR model to teach mathematics methods both in the classroom and in the field. The preservice teachers took Enochs, Smith, and Huinker's Mathematics Teaching Efficacy Beliefs Instrument (MTEBI) on the first and last day of class. A total of 297 responses were collected from the pre‐ and posttests, with 280 matching responses, which were then used for data analysis. Mixed methods were used to analyze qualitative and quantitative data. The researchers sought to determine if the specific teaching methods from the BAR model led to positive changes in preservice teacher efficacy beliefs. They also explored if efficacy beliefs changed as a result of field experiences. Preservice teachers' efficacy scores changed positively on every item on the MTEBI. The researchers also determined that there was an increase in preservice teachers' outputs as a result of their field experiences. 相似文献
130.
D'Autry W Wolfs K Hoogmartens J Adams E Van Schepdael A 《Journal of chromatography. A》2011,1218(26):4034-4038
Gas chromatography-mass spectrometry is a well established analytical technique. However, mass spectrometers with electron ionization sources may suffer from signal drifts, hereby negatively influencing quantitative performance. To demonstrate this phenomenon for a real application, a static headspace-gas chromatography method in combination with electron ionization-quadrupole mass spectrometry was optimized for the determination of residual dichloromethane in coronary stent coatings. Validating the method, the quantitative performance of an original stainless steel ion source was compared to that of a modified ion source. Ion source modification included the application of a gold coating on the repeller and exit plate. Several validation aspects such as limit of detection, limit of quantification, linearity and precision were evaluated using both ion sources. It was found that, as expected, the stainless steel ion source suffered from signal drift. As a consequence, non-linearity and high RSD values for repeated analyses were obtained. An additional experiment was performed to check whether an internal standard compound would lead to better results. It was found that the signal drift patterns of the analyte and internal standard were different, consequently leading to high RSD values for the response factor. With the modified ion source however, a more stable signal was observed resulting in acceptable linearity and precision. Moreover, it was also found that sensitivity improved compared to the stainless steel ion source. Finally, the optimized method with the modified ion source was applied to determine residual dichloromethane in the coating of coronary stents. The solvent was detected but found to be below the limit of quantification. 相似文献