全文获取类型
收费全文 | 1967篇 |
免费 | 48篇 |
国内免费 | 7篇 |
专业分类
化学 | 1086篇 |
晶体学 | 8篇 |
力学 | 40篇 |
数学 | 251篇 |
物理学 | 637篇 |
出版年
2021年 | 23篇 |
2020年 | 30篇 |
2019年 | 41篇 |
2018年 | 18篇 |
2017年 | 19篇 |
2016年 | 59篇 |
2015年 | 32篇 |
2014年 | 47篇 |
2013年 | 72篇 |
2012年 | 73篇 |
2011年 | 106篇 |
2010年 | 54篇 |
2009年 | 45篇 |
2008年 | 93篇 |
2007年 | 77篇 |
2006年 | 97篇 |
2005年 | 81篇 |
2004年 | 67篇 |
2003年 | 67篇 |
2002年 | 60篇 |
2001年 | 61篇 |
2000年 | 31篇 |
1999年 | 18篇 |
1998年 | 20篇 |
1997年 | 20篇 |
1996年 | 57篇 |
1995年 | 35篇 |
1994年 | 25篇 |
1993年 | 39篇 |
1992年 | 39篇 |
1991年 | 30篇 |
1990年 | 24篇 |
1989年 | 27篇 |
1988年 | 25篇 |
1987年 | 16篇 |
1986年 | 9篇 |
1985年 | 14篇 |
1984年 | 21篇 |
1983年 | 10篇 |
1982年 | 12篇 |
1981年 | 19篇 |
1980年 | 26篇 |
1979年 | 17篇 |
1978年 | 26篇 |
1977年 | 15篇 |
1976年 | 17篇 |
1974年 | 24篇 |
1973年 | 18篇 |
1972年 | 10篇 |
1962年 | 9篇 |
排序方式: 共有2022条查询结果,搜索用时 140 毫秒
1.
2.
3.
4.
He Zhu Dr. Qiang Chen Dr. Igor Rončević Dr. Kirsten E. Christensen Prof. Harry L. Anderson 《Angewandte Chemie (International ed. in English)》2023,62(31):e202307035
π-Conjugated nanoribbons attract interest because of their unusual electronic structures and charge-transport behavior. Here, we report the synthesis of a series of fully edge-fused porphyrin-anthracene oligomeric ribbons (dimer and trimer), together with a computational study of the corresponding infinite polymer. The porphyrin dimer and trimer were synthesized in high yield, via oxidative cyclodehydrogenation of singly linked precursors, using 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and trifluoromethanesulfonic acid (TfOH). The crystal structure of the dimer shows that the central π-system is flat, with a slight S-shaped wave distortion at each porphyrin terminal. The extended π-conjugation causes a dramatic red-shift in the absorption spectra: the absorption maxima of the fused dimer and trimer appear at 1188 nm and 1642 nm, respectively (for the nickel complexes dissolved in toluene). The coordinated metal in the dimer was changed from Ni to Mg, using p-tolylmagnesium bromide, providing access to free-base and Zn complexes. These results open a versatile avenue to longer π-conjugated nanoribbons with integrated metalloporphyrin units. 相似文献
5.
Construction of a New Class of Tetracycline Lead Structures with Potent Antibacterial Activity through Biosynthetic Engineering 下载免费PDF全文
Dr. Urška Lešnik Dr. Tadeja Lukežič Dr. Ajda Podgoršek Dr. Jaka Horvat Dr. Tomaž Polak Dr. Martin Šala Branko Jenko Dr. Kirsten Harmrolfs Dr. Alain Ocampo‐Sosa Prof. Dr. Luis Martínez‐Martínez Dr. Paul R. Herron Dr. Štefan Fujs Dr. Gregor Kosec Prof. Dr. Iain S. Hunter Prof. Dr. Rolf Müller Prof. Dr. Hrvoje Petković 《Angewandte Chemie (International ed. in English)》2015,54(13):3937-3940
Antimicrobial resistance and the shortage of novel antibiotics have led to an urgent need for new antibacterial drug leads. Several existing natural product scaffolds (including chelocardins) have not been developed because their suboptimal pharmacological properties could not be addressed at the time. It is demonstrated here that reviving such compounds through the application of biosynthetic engineering can deliver novel drug candidates. Through a rational approach, the carboxamido moiety of tetracyclines (an important structural feature for their bioactivity) was introduced into the chelocardins, which are atypical tetracyclines with an unknown mode of action. A broad‐spectrum antibiotic lead was generated with significantly improved activity, including against all Gram‐negative pathogens of the ESKAPE panel. Since the lead structure is also amenable to further chemical modification, it is a platform for further development through medicinal chemistry and genetic engineering. 相似文献
6.
Dr. Hans‐Georg Stammler M. Sc. Sebastian Blomeyer Priv.‐Doz. Dr. Raphael J. F. Berger Prof. Dr. Norbert W. Mitzel 《Angewandte Chemie (International ed. in English)》2015,54(46):13816-13820
The charge density distribution of the trimethylaluminum dimer was determined by high‐angle X‐ray diffraction of a single crystal and quantum‐chemical methods and analyzed using the quantum theory of atoms in molecules. The data can be interpreted as Al2Me6 being predominantly ionically bonded, with clear indications of topological asymmetry for the bridging Al? C bonds owing to delocalized multicenter bonding. This interpretation is supported by the calculated magnetic response currents. The data shed new light on the bonding situation in this basic organometallic molecule, which was previously described by contradicting interpretations of bonding. 相似文献
7.
8.
Dr. Samuel M. Meier M. Sc. Dominique Kreutz Dr. Lilli Winter M. Sc. Matthias H. M. Klose M. Sc. Klaudia Cseh M. Sc. Tamara Weiss Dr. Andrea Bileck M. Sc. Beatrix Alte Dr. Johanna C. Mader M. Sc. Samir Jana Dr. Annesha Chatterjee Dr. Arindam Bhattacharyya Michaela Hejl Dr. Michael A. Jakupec Priv.-Doz. Dr. Petra Heffeter Prof. Dr. Walter Berger Prof. Dr. Christian G. Hartinger Prof. Dr. Bernhard K. Keppler Prof. Dr. Gerhard Wiche Prof. Dr. Christopher Gerner 《Angewandte Chemie (International ed. in English)》2017,56(28):8267-8271
Organometallic metal(arene) anticancer agents require ligand exchange for their anticancer activity and this is generally believed to confer low selectivity for potential cellular targets. However, using an integrated proteomics-based target-response profiling approach as a potent hypothesis-generating procedure, we found an unexpected target selectivity of a ruthenium(arene) pyridinecarbothioamide (plecstatin) for plectin, a scaffold protein and cytolinker, which was validated in a plectin knock-out model in vitro. Plectin targeting shows potential as a strategy to inhibit tumor invasiveness as shown in cultured tumor spheroids while oral administration of plecstatin-1 to mice reduces tumor growth more efficiently in the invasive B16 melanoma than in the CT26 colon tumor model. 相似文献
9.
10.
Katharina Röser Bettina Berger Prof. Michael Widhalm Prof. Mario Waser 《ChemistryOpen》2021,10(8):756-759
We herein report an asymmetric protocol to access a series of orthogonally functionalized acyclic chiral target molecules containing a quaternary stereogenic center by carrying out the enantioselective α-alkylation of novel orthogonally functionalized dioxolane-containing cyanoacetates under chiral ammonium salt catalysis. By using just 1 mol % of Maruoka's spirocyclic ammonium salt catalysts enantioselectivities up to e.r.=97.5 : 2.5 could be achieved and further functional group manipulations of the products were carried out as well. 相似文献