全文获取类型
收费全文 | 30138篇 |
免费 | 3801篇 |
国内免费 | 2351篇 |
专业分类
化学 | 21706篇 |
晶体学 | 321篇 |
力学 | 1361篇 |
综合类 | 186篇 |
数学 | 3584篇 |
物理学 | 9132篇 |
出版年
2023年 | 506篇 |
2022年 | 523篇 |
2021年 | 768篇 |
2020年 | 1016篇 |
2019年 | 946篇 |
2018年 | 732篇 |
2017年 | 685篇 |
2016年 | 1209篇 |
2015年 | 1131篇 |
2014年 | 1323篇 |
2013年 | 1869篇 |
2012年 | 2334篇 |
2011年 | 2493篇 |
2010年 | 1614篇 |
2009年 | 1433篇 |
2008年 | 1843篇 |
2007年 | 1817篇 |
2006年 | 1677篇 |
2005年 | 1516篇 |
2004年 | 1141篇 |
2003年 | 950篇 |
2002年 | 951篇 |
2001年 | 611篇 |
2000年 | 597篇 |
1999年 | 632篇 |
1998年 | 523篇 |
1997年 | 519篇 |
1996年 | 467篇 |
1995年 | 428篇 |
1994年 | 456篇 |
1993年 | 377篇 |
1992年 | 310篇 |
1991年 | 310篇 |
1990年 | 269篇 |
1989年 | 188篇 |
1988年 | 150篇 |
1987年 | 157篇 |
1986年 | 113篇 |
1985年 | 155篇 |
1984年 | 137篇 |
1983年 | 89篇 |
1982年 | 127篇 |
1981年 | 107篇 |
1980年 | 89篇 |
1979年 | 95篇 |
1978年 | 86篇 |
1977年 | 78篇 |
1976年 | 87篇 |
1975年 | 65篇 |
1973年 | 56篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Dr. Sebastian Lars Müller Xinglong Zhou Dr. Peter Leonard Oxana Korzhenko Dr. Constantin Daniliuc Prof. Dr. Frank Seela 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(12):3077-3090
Silver-mediated α-dC–Ag+–β-dC hybrid base pairs decorated with 5-iodo- or 5-octadiynyl residues are well accommodated in duplex DNA. A strong Tm increase and favorable thermodynamic data for duplex DNA were observed after addition of silver ions. The phenomenon is particularly obvious when both nucleobases of the base pairs are functionalized. Neither the position of the base pair, nor the type of 5-substituent had a negative influence. On the contrary, functionalization of conventional silver-mediated β-dC–Ag+–β-dC homo base pairs showed a negative impact induced by the bulky substituents. To this end, cytosine modified 12-mer oligodeoxynucleotides were prepared by solid-phase synthesis employing new α-anomeric 2′-deoxycytidine phosphoramidites. A multigram scale synthesis was developed for 5-iodo-α-d -2′-deoxycytidine ( 1 ) employing the direct glycosylation of cytosine with Hoffer's α-d -halogenose followed by separation of anomeric DMT nucleosides. Regarding base-pair stability and functionalization silver-mediated α/β-dC hybrid base pairs were found to be superior to β/β-dC homo pairs. According to their extraordinary properties, they might find applications in DNA diagnostics, material science, or nanotechnology. 相似文献
22.
Prof. Dr. Frank Glorius 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(22):8047-8051
A general and efficient methodology for the direct transition metal free trifluoromethylthiolation of a broad range of biologically relevant N‐heteroarenes is reported employing abundant sodium chloride as the catalyst. This method is operationally simple, exhibits high functional group tolerance, and does not require protecting groups. 相似文献
23.
In this Letter,a novel system for adaptively correcting the phase of a dynamic multimode beam is proposed.While using merely one spatial light modulator,the phase measurement of the first-order diffraction pattern and the correction of the zeroth diffraction order are simultaneously realized.The real-time experimental result is obtained at a control rate of 10 Hz.The power-in-the-bucket value is improved from 38.5%to 61.8%,even with fundamental mode content that is consistently below 30%.To the best of our knowledge,this is the first implementation of real-time adaptive correction of the entire multimode beam. 相似文献
24.
25.
26.
Dr. Masaru Kondo Dr. Shinobu Takizawa Yuzhao Jiang Prof. Dr. Hiroaki Sasai 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(42):9866-9869
The Mills reaction and cyclization of readily available 2-aminobenzyl alcohols and nitrosobenzenes using thionyl bromide provided 2H-indazoles in up to 88 % yields. In the metal-free process, acetic acid played a crucial role for the both Mills reaction and cyclization. A brominated 2H-indazole could also be obtained through the one-pot sequence. 相似文献
27.
28.
29.
Dr. Si-Yong Qin Yan Jiang Dr. Han Sun Han Liu Prof. Ai-Qing Zhang Prof. Xinxiang Lei 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(39):17245-17251
Residual dipolar coupling (RDC), a robust anisotropic NMR parameter for structural elucidation of organic molecules, is only accessible in an anisotropic environment. Herein, we introduce a novel alignment medium based on the molecular self-assembly of oligopeptide amphiphile (OPA). This medium is compatible with different intermediate and polar solvent systems, such as CD3OD, [D6]DMSO, and D2O. The preparation of the OPA-based medium is simple and rapid, while only very weak background signals were observed from OPAs. Furthermore, we show that the purity of OPA has only a minor influence on the quality of the RDC data. These advantages allow RDC measurements of organic molecules with different polarities and solubilities with high efficiency and accuracy. 相似文献
30.