全文获取类型
收费全文 | 2726篇 |
免费 | 106篇 |
国内免费 | 17篇 |
专业分类
化学 | 1712篇 |
晶体学 | 10篇 |
力学 | 115篇 |
数学 | 403篇 |
物理学 | 609篇 |
出版年
2023年 | 13篇 |
2022年 | 20篇 |
2021年 | 43篇 |
2020年 | 60篇 |
2019年 | 51篇 |
2018年 | 30篇 |
2017年 | 38篇 |
2016年 | 93篇 |
2015年 | 65篇 |
2014年 | 65篇 |
2013年 | 134篇 |
2012年 | 157篇 |
2011年 | 190篇 |
2010年 | 119篇 |
2009年 | 105篇 |
2008年 | 145篇 |
2007年 | 131篇 |
2006年 | 95篇 |
2005年 | 112篇 |
2004年 | 104篇 |
2003年 | 80篇 |
2002年 | 75篇 |
2001年 | 53篇 |
2000年 | 46篇 |
1999年 | 36篇 |
1998年 | 34篇 |
1997年 | 26篇 |
1996年 | 46篇 |
1995年 | 31篇 |
1994年 | 28篇 |
1993年 | 28篇 |
1992年 | 28篇 |
1991年 | 43篇 |
1990年 | 25篇 |
1989年 | 26篇 |
1988年 | 25篇 |
1987年 | 19篇 |
1986年 | 15篇 |
1985年 | 30篇 |
1984年 | 35篇 |
1983年 | 31篇 |
1982年 | 30篇 |
1981年 | 23篇 |
1980年 | 29篇 |
1978年 | 32篇 |
1977年 | 15篇 |
1976年 | 21篇 |
1975年 | 21篇 |
1973年 | 12篇 |
1972年 | 15篇 |
排序方式: 共有2849条查询结果,搜索用时 15 毫秒
101.
102.
103.
104.
Dr. Steffen Bähring Dr. Luis Martín‐Gomis Gunnar Olsen Prof. Dr. Kent A. Nielsen Dr. Dong Sub Kim Dr. Troels Duedal Prof. Dr. Ángela Sastre‐Santos Prof. Dr. Jan O. Jeppesen Prof. Dr. Jonathan L. Sessler 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(6):1958-1967
Supramolecular polymers are a class of macromolecules stabilized by weak non‐covalent interactions. These self‐assembled aggregates typically undergo stimuli‐induced reversible assembly and disassembly. They thus hold great promise as so‐called functional materials. In this work, we present the design, synthesis, and responsive behavior of a short supramolecular oligomeric system based on two hetero‐complementary subunits. These “monomers” consist of a tetrathiafulvalene‐functionalized calix[4]pyrrole (TTF‐C[4]P) and a glycol diester‐linked bis‐2,5,7‐trinitrodicyanomethylenefluorene‐4‐carboxylate (TNDCF), respectively. We show that when mixed in organic solvents, such as CHCl3, CH2ClCH2Cl, and methylcyclohexane, supramolecular aggregation takes place to produce short oligomers stabilized by hydrogen bonding and donor–acceptor charge‐transfer (CT) interactions. The self‐associated materials were characterized by 1H NMR and UV/Vis/NIR absorption spectroscopy, as well as by concentration‐ and temperature‐dependent absorption spectroscopy and dynamic light scattering (DLS) analyses of both the monomeric and oligomerized species. The self‐associated system produced from TTF‐C[4]P and TNDCF exhibits a concentration‐dependent aggregation behavior typical of supramolecular polymers. Further support for the proposed self‐assembly came from theoretical calculations. The fluorescence emitting properties of TNDCF are quenched under conditions that promote the formation of supramolecular aggregates containing TTF‐C[4]P and TNDCF. This quenching effect has been utilized as a probe for the detection of substrates in the form of anions (i.e., chloride) and nitroaromatic explosives (i.e., 1,3,5‐trinitrobenzene). Specifically, the addition of these substrates to mixtures of TTF‐C[4]P and TNDCF produced a fluorescence “turn‐on” response. 相似文献
105.
106.
Steffen Lewitzka 《Annals of Pure and Applied Logic》2019,170(2):218-250
In previous work [15], we presented a hierarchy of classical modal systems, along with algebraic semantics, for the reasoning about intuitionistic truth, belief and knowledge. Deviating from Gödel's interpretation of IPC in S4, our modal systems contain IPC in the way established in [13]. The modal operator can be viewed as a predicate for intuitionistic truth, i.e. proof. Epistemic principles are partially adopted from Intuitionistic Epistemic Logic IEL [4]. In the present paper, we show that the S5-style systems of our hierarchy correspond to an extended Brouwer–Heyting–Kolmogorov interpretation and are complete w.r.t. a relational semantics based on intuitionistic general frames. In this sense, our S5-style logics are adequate and complete systems for the reasoning about proof combined with belief or knowledge. The proposed relational semantics is a uniform framework in which also IEL can be modeled. Verification-based intuitionistic knowledge formalized in IEL turns out to be a special case of the kind of knowledge described by our S5-style systems. 相似文献
107.
Katharina Zielke Ondřej Kováč Michael Winter Dr. Jiří Pospíšil Prof. Mario Waser 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(34):8163-8168
The first highly asymmetric catalytic synthesis of densely functionalized dihydrobenzofurans is reported, which starts from ortho-hydroxy-containing para-quinone methides. The reaction relies on an unprecedented formal [4+1]-annulation of these quinone methides with allenoates in the presence of a commercially available chiral phosphine catalyst. The chiral dihydrobenzofurans were obtained as single diastereomers in yields up to 90 % and with enantiomeric ratios up to 95:5. 相似文献
108.
109.
110.
Redox‐Active Tetraruthenium Macrocycles Built from 1,4‐Divinylphenylene‐Bridged Diruthenium Complexes
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Stefan Scheerer Dr. Michael Linseis Dr. Evelyn Wuttke Sabrina Weickert Prof. Dr. Malte Drescher Dr. Oliver Tröppner Prof. Dr. Ivana Ivanović‐Burmazović Andreas Irmler Prof. Dr. Fabian Pauly Prof. Dr. Rainer F. Winter 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(28):9574-9590
Metallamacrocylic tetraruthenium complexes were generated by treatment of 1,4‐divinylphenylene‐bridged diruthenium complexes with functionalized 1,3‐benzene dicarboxylic acids and characterized by HR ESI‐MS and multinuclear NMR spectroscopy. Every divinylphenylene diruthenium subunit is oxidized in two consecutive one‐electron steps with half‐wave potential splittings in the range of 250 to 330 mV. Additional, smaller redox‐splittings between the +/2+ and 0/+ and the 3+/4+ and 2+/3+ redox processes, corresponding to the first and the second oxidations of every divinylphenylene diruthenium entity, are due to electrostatic effects. The lack of electronic coupling through bond or through space is explained by the nodal properties of the relevant molecular orbitals and the lateral side‐by‐side arrangement of the divinylphenylene linkers. The polyelectrochromic behavior of the divinylphenylene diruthenium precursors is retained and even amplified in these metallamacrocyclic structures. EPR studies down to T=4 K indicate that the dications 1‐H2+ and 1‐OBu2+ are paramagnetic. The dications and the tetracation of macrocycle 3‐H display intense (dications) or weak ( 3‐H4+ ) EPR signals. Quantum chemical calculations indicate that the four most stable conformers of the macrocycles are largely devoid of strain. Bond parameters, energies as well as charge and spin density distributions of model macrocycle 5‐HMe were calculated for the different charge and spin states. 相似文献