全文获取类型
收费全文 | 1507篇 |
免费 | 42篇 |
国内免费 | 5篇 |
专业分类
化学 | 959篇 |
晶体学 | 10篇 |
力学 | 23篇 |
数学 | 276篇 |
物理学 | 286篇 |
出版年
2021年 | 13篇 |
2020年 | 26篇 |
2019年 | 24篇 |
2018年 | 12篇 |
2016年 | 35篇 |
2015年 | 27篇 |
2014年 | 40篇 |
2013年 | 64篇 |
2012年 | 69篇 |
2011年 | 64篇 |
2010年 | 62篇 |
2009年 | 42篇 |
2008年 | 76篇 |
2007年 | 55篇 |
2006年 | 61篇 |
2005年 | 47篇 |
2004年 | 36篇 |
2003年 | 31篇 |
2002年 | 36篇 |
2001年 | 25篇 |
2000年 | 22篇 |
1999年 | 19篇 |
1998年 | 14篇 |
1997年 | 14篇 |
1996年 | 19篇 |
1995年 | 23篇 |
1994年 | 18篇 |
1993年 | 22篇 |
1992年 | 33篇 |
1991年 | 16篇 |
1990年 | 18篇 |
1989年 | 14篇 |
1988年 | 13篇 |
1986年 | 12篇 |
1985年 | 27篇 |
1984年 | 25篇 |
1983年 | 15篇 |
1982年 | 20篇 |
1981年 | 23篇 |
1980年 | 24篇 |
1979年 | 17篇 |
1978年 | 26篇 |
1977年 | 15篇 |
1976年 | 12篇 |
1975年 | 16篇 |
1974年 | 26篇 |
1971年 | 12篇 |
1970年 | 17篇 |
1969年 | 15篇 |
1967年 | 10篇 |
排序方式: 共有1554条查询结果,搜索用时 15 毫秒
141.
Albrecht M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(19):3485-3489
Dinuclear triple-stranded helicates or meso-helicates are formed by self-assembly of linear ligand strands with appropriate metal ions. Very often this self-assembly proceeds with high diastereoselectivity leading either to the helicate or the meso-helicate. The stereoselectivity of the self-assembly process can be influenced by different factors such as the rigidity of the ligand (-->helicate), the number of methylene units in the alkyl spacers (even number of CH2 units --> helicate; odd number --> meso-helicate), template effects, or chiral substituents. 相似文献
142.
Dannenmuller O Arakawa K Eguchi T Kakinuma K Blanc S Albrecht AM Schmutz M Nakatani Y Ourisson G 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(4):645-654
Several biophysical properties of four synthetic archaeal phospholipids [one polyprenyl macrocyclic lipid A and three polyprenyl double-chain lipids (B, C, D) bearing zero, one or four double bonds in each chain] were studied using differential scanning calorimetry, electron and optical microscopies, stopped-flow/light scattering and solid-state 2H-NMR techniques. These phospholipids gave a variety of self-organized structures in water, in particular vesicles and tubules. These assemblies change in response to simple thermal convection. Some specific membrane properties of these archaeal phospholipids were observed: They are in a liquid-crystalline state over a wide temperature range; the dynamics of their polyprenyl chains is higher than that of n-acyl chains; the water permeability of the membranes is lower than that of n-acyl phospholipid membranes. It was also found that macrocyclization remarkably improves the barrier properties to water and the membrane stability. This may be related to the adaptation of Methanococcus jannaschii to the extreme conditions of the deep-sea hydrothermal vents. 相似文献
143.
Rodríguez G Albrecht M Schoenmaker J Ford A Lutz M Spek AL van Koten G 《Journal of the American Chemical Society》2002,124(18):5127-5138
The reactivity of the bifunctionalized ligand NC(Br)N-I 1 [IC(6)H(2)(CH(2)NMe(2))(2)-3,5-Br-4] has been studied as a versatile synthon for organic and/or organometallic synthesis. Chemoselective metalation (M = Pd, Pt, Li) at the C(aryl)-I or C(aryl)-Br bonds was achieved by choosing the appropriate metal precursors. In this way a series of Pt(II) and Pd(II) complexes were prepared that have a second functional group available for further reactions. These Pt(II) and Pd(II) complexes were subjected to a wide range of organic and organometallic reactions, revealing the remarkable stability of their M-C sigma-bond and opening an easy route for the synthesis of mono- and (hetero)bimetallic building blocks. The scope of the chemistry of such building blocks shows that they are good candidates for use in the synthesis of dendrimers, bioorganometallic systems, or polymetallic materials. The X-ray crystal structures of the most representative complexes (2, 3a, 19, 20, and 24) are also reported. 相似文献
144.
Guillena G Rodríguez G Albrecht M van Koten G 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(23):5368-5376
Arylplatinum(II) complexes have been covalently bonded to the N and C termini and to the alpha-carbon of various amino acid derivatives. These organometallic-functionalized amino acid compounds can be converted into the corresponding free amino acids under both basic and acidic conditions; this demonstrates the excellent stability properties of these biomolecules. Due to the NMR activity displayed by the 195Pt nucleus (natural abundance 33.8%, I = 1/2) these compounds are functional bio-markers. Furthermore, the ability of the arylplatinum functional group to bind SO2 gas, selectively and reversibly as indicated by changes in the spectroscopic properties (1H, 13C, 195Pt NMR and UV spectra) of these compounds, allows for the potential use of these complexes as in vitro biosensors. 相似文献
145.
M Albrecht Y Shang K Hasui V Gossen G Raabe K Tahara Y Tobe 《Dalton transactions (Cambridge, England : 2003)》2012,41(31):9316-9322
Triangular triscatechol ligands are prepared in facile reaction sequences. The catechol units are either bound to the triangular backbone through their 3- or 4-position. With titanium(IV) ions, the ligands form metallosupramolecular M(4)L(4) tetrahedra which are characterized by ESI MS and proton NMR. Quantum-chemical calculations reveal that connectivity at the catechol in the 3-position results in highly condensed structures while attachment in the 4-position affords container molecules providing huge internal cavities. 相似文献
146.
147.
Dr. Łukasz Albrecht Dr. Hao Jiang Prof. Dr. Karl Anker Jørgensen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(2):358-368
This Concept article summarizes recent progress in the field of hydrogen‐bonding aminocatalysis using proline‐derived systems. The aminocatalysts available in the literature are categorized by the incorporated hydrogen‐bonding scaffold and its mode of recognition. Both mono‐ and double‐hydrogen‐bonding motifs are discussed and examples of their application in asymmetric synthesis are given. 相似文献
148.
Sensing of Phosphates by Using Luminescent EuIII and TbIII Complexes: Application to the Microalgal Cell Chlorella vulgaris 下载免费PDF全文
Sandeep Nadella Jashobanta Sahoo Dr. Palani S. Subramanian Abhishek Sahu Dr. Sandhya Mishra Prof. Dr. Markus Albrecht 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(20):6047-6053
Phenanthroline‐based chiral ligands L1 and L2 as well as the corresponding EuIII and TbIII complexes were synthesized and characterized. The coordination compounds show red and green emission, which was explored for the sensing of a series of anions such as F?, Cl?, Br?, I?, NO3?, NO2?, HPO42?, HSO4?, CH3COO?, and HCO3?. Among the anions, HPO42? exhibited a strong response in the emission property of both europium(III) and terbium(III) complexes. The complexes showed interactions with the nucleoside phosphates adenosine triphosphate (ATP), adenosine diphosphate (ADP), and adenosine monophosphate (AMP). Owing to this recognition, these complexes have been applied as staining agents in the microalgal cell Chlorella vulgaris. The stained microalgal cells were monitored through fluorescence microscopy and scanning electron microscopy. Initially, the complexes bind to the outer cell wall and then enter the cell wall through holes in which they probably bind to phospholipids. This leads to a quenching of the luminescence properties. 相似文献
149.
150.
Carbazole Dendrimers as Solution‐Processable Thermally Activated Delayed‐Fluorescence Materials 下载免费PDF全文
Assist. Prof. Ken Albrecht Assist. Prof. Kenichi Matsuoka Assoc. Prof. Katsuhiko Fujita Prof. Kimihisa Yamamoto 《Angewandte Chemie (International ed. in English)》2015,54(19):5677-5682
Recently, thermally activated delayed fluorescence (TADF) materials have received increasing attention as effective emitters for organic light‐emitting diodes (OLEDs). However, most of them are usually employed as dopants in a host material. In this report, carbazole dendrimers with a triphenyl‐s‐triazine core are reported, which are the first solution‐processable, non‐doped, high‐molecular‐weight TADF materials. The dendrimers were obtained by a new and facile synthetic route using the tert‐butyldimethylsilyl moiety as a protecting group. All dendrimers showed TADF in toluene. Measurements of the temperature‐dependent luminescence lifetime revealed that spin‐coated neat films also showed TADF with moderate quantum yields. OLED devices incorporating these dendrimers as spin‐coated emitting layers gave external quantum efficiencies of up to a 3.4 %, which suggests that this device is harvesting triplet excitons. This result indicates that carbazole dendrimers with attached acceptors are potential TADF materials owing to their polarized electronic structure (with HOMO–LUMO separation). 相似文献