全文获取类型
收费全文 | 448篇 |
免费 | 19篇 |
国内免费 | 1篇 |
专业分类
化学 | 293篇 |
晶体学 | 1篇 |
力学 | 4篇 |
数学 | 12篇 |
物理学 | 158篇 |
出版年
2023年 | 3篇 |
2022年 | 8篇 |
2021年 | 7篇 |
2020年 | 25篇 |
2019年 | 15篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2016年 | 13篇 |
2015年 | 9篇 |
2014年 | 15篇 |
2013年 | 19篇 |
2012年 | 23篇 |
2011年 | 28篇 |
2010年 | 12篇 |
2009年 | 15篇 |
2008年 | 28篇 |
2007年 | 22篇 |
2006年 | 13篇 |
2005年 | 19篇 |
2004年 | 13篇 |
2003年 | 8篇 |
2002年 | 8篇 |
2001年 | 15篇 |
2000年 | 8篇 |
1999年 | 6篇 |
1998年 | 3篇 |
1997年 | 5篇 |
1996年 | 9篇 |
1994年 | 13篇 |
1993年 | 9篇 |
1992年 | 8篇 |
1991年 | 3篇 |
1990年 | 5篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1975年 | 7篇 |
1974年 | 2篇 |
1973年 | 5篇 |
1967年 | 4篇 |
1936年 | 2篇 |
1888年 | 2篇 |
排序方式: 共有468条查询结果,搜索用时 78 毫秒
401.
D. Kaczmarek S. Shaqiri B. Atakan T. Kasper 《Proceedings of the Combustion Institute》2021,38(1):233-241
Methane based polygeneration processes in piston engines offer the possibility of a controllable and flexible conversion of energy, to up-convert low value chemicals and to store energy. These processes preferably take place under fuel-rich conditions and at high pressures. Under fuel-rich conditions, there was one experimental report that a distinctive negative temperature coefficient (NTC) behavior occurs in methane oxidation (Petersen et al., 1999). To design a polygeneration process, reliable kinetic models are required to capture the impact of pressure and equivalence ratio variations on reactivity of the gas mixtures. Here, the experimental basis for methane oxidation is expanded to high pressures and very fuel-rich conditions and compared to literature models, both with special emphasis on the NTC behavior. The oxidation of methane/oxygen mixtures at 2 ≤ Φ≤ 20 and pressures ranging from 1 to 20 bar is investigated. The literature reaction mechanisms are assessed with respect to their ability to predict this phenomenon and used to identify reaction pathways. It is found that NTC behavior occurs in a temperature range between 700 and 1000 K and at pressures higher than 5 bar. The lower temperature limit is slightly shifted towards higher temperatures with decreasing equivalence ratio. In addition, the higher the equivalence ratio, the broader the pressure range, in which the NTC behavior is observed. In general, predictions of some models are in good agreement with the experimental data. Reaction path analyses reveal that the competition between oxidation and recombination pathways are responsible for the NTC region in methane oxidation. 相似文献
402.
Dr. Christian Kofoed Dr. Shunliang Wu Dr. Kasper K. Sørensen Tuule Treiberg Dr. Johnny Arnsdorf Dr. Sara P. Bjørn Dr. Tanja L. Jensen Bjørn G. Voldborg Dr. Mikkel B. Thygesen Prof. Knud J. Jensen Dr. Sanne Schoffelen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(15):e202200147
Chemical modification of proteins has numerous applications, but it has been challenging to achieve the required high degree of selectivity on lysine amino groups. Recently, we described the highly selective acylation of proteins with an N-terminal Gly-His6 segment. This tag promoted acylation of the N-terminal Nα-amine resulting in stable conjugates. Herein, we report the peptide sequences Hisn-Lys-Hism, which we term Lys-His tags. In combination with simple acylating agents, they facilitate the acylation of the designated Lys Nϵ-amine under mild conditions and with high selectivity over native Lys residues. We show that the Lys-His tags, which are 7 to 10 amino acids in length and still act as conventional His tags, can be inserted in proteins at the C-terminus or in loops, thus providing high flexibility regarding the site of modification. Finally, the selective and efficient acylation of the therapeutic antibody Rituximab, pure or mixed with other proteins, demonstrates the scope of the Lys-His tag acylation method. 相似文献
403.
Dr. Sergio Sanz Helen M. O'Connor Eufemio Moreno Pineda Dr. Kasper S. Pedersen Dr. Gary S. Nichol Dr. Ole Mønsted Dr. Høgni Weihe Dr. Stergios Piligkos Prof. Eric J. L. McInnes Dr. Paul J. Lusby Prof. Euan K. Brechin 《Angewandte Chemie (International ed. in English)》2015,54(23):6761-6764
[CrIII8MII6]12+ (MII=Cu, Co) coordination cubes were constructed from a simple [CrIIIL3] metalloligand and a “naked” MII salt. The flexibility in the design proffers the potential to tune the physical properties, as all the constituent parts of the cage can be changed without structural alteration. Computational techniques (known in theoretical nuclear physics as statistical spectroscopy) in tandem with EPR spectroscopy are used to interpret the magnetic behavior. 相似文献
404.
405.
Pedro C Rodriguez Elia Neninger Beatriz García Xitlally Popa Carmen Viada Patricia Luaces Gisela González Agustin Lage Enrique Montero Tania Crombet 《Journal of immune based therapies and vaccines》2011,9(1):1-6
The prognosis of patients with advanced non small cell lung (NSCLC) cancer remains dismal. Epidermal Growth Factor Receptor is over-expressed in many epithelial derived tumors and its role in the development and progression of NSCLC is widely documented. CimaVax-EGF is a therapeutic cancer vaccine composed by human recombinant Epidermal Growth Factor (EGF) conjugated to a carrier protein, P64K from Neisseria Meningitides. The vaccine is intended to induce antibodies against self EGF that would block EGF-EGFR interaction. CimaVax-EGF has been evaluated so far in more than 1000 advanced NSCLC patients, as second line therapy. Two separate studies were compared to assess the impact of high dose vaccination at multiple anatomic sites in terms of immunogenicity, safety and preliminary efficacy in stage IIIb/IV NSCLC patients. In both clinical trials, patients started vaccination 1 month after finishing first line chemotherapy. Vaccination at 4 sites with 2.4 mg of EGF (high dose) was very safe. The most frequent adverse events were grade 1 or 2 injection site reactions, fever, headache and vomiting. Patients had a trend toward higher antibody response. The percent of very good responders significantly augmented and there was a faster decrease of circulating EGF. All vaccinated patients and those classified as good responders immunized with high dose at 4 sites, had a large tendency to improved survival. 相似文献
406.
Michael R. Harpham Son C. Nguyen Zongrui Hou Jeffrey C. Grossman Charles B. Harris Michael W. Mara Andrew B. Stickrath Yosuke Kanai Alexie M. Kolpak Donghwa Lee Di‐Jia Liu Justin P. Lomont Kasper Moth‐Poulsen Nikolai Vinokurov Lin X. Chen K. Peter C. Vollhardt 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2012,124(31):7812-7816
407.
408.
Controlling the reciprocity between chemical reactivity and supramolecular structure is a topic of great interest in the emergence of molecular complexity. In this work, we investigate the effect of a covalent reaction as a trigger to depolymerize a supramolecular assembly. We focus on the impact of an in situ thiol–ene reaction on the (co)polymerization of three derivatives of benzene-1,3,5-tricarboxamide (BTA) monomers functionalized with cysteine, hexylcysteine, and alkyl side chains: Cys-BTA, HexCys-BTA, and a-BTA. Long supramolecular polymers of Cys-BTA can be depolymerized into short dimeric aggregates of HexCys-BTAvia the in situ thiol–ene reaction. Analysis of the system by time-resolved spectroscopy and light scattering unravels the fast dynamicity of the structures and the mechanism of depolymerization. Moreover, by intercalating the reactive Cys-BTA monomer into an unreactive inert polymer, the in situ thiol–ene reaction transforms the intercalator into a sequestrator and induces the depolymerization of the unreactive polymer. This work shows that the implementation of reactivity into supramolecular assemblies enables temporal control of depolymerization processes, which can bring us one step closer to understanding the interplay between non-covalent and covalent chemistry.We report on the controlled depolymerization of supramolecular 1D polymers into well-defined dimers triggered by a covalent reaction on the side chains of the monomer. 相似文献
409.
Maria Quant Andreas Erbs Hillers-Bendtsen Shima Ghasemi Mate Erdelyi Zhihang Wang Lidiya M. Muhammad Nina Kann Kurt V. Mikkelsen Kasper Moth-Poulsen 《Chemical science》2022,13(3):834
Molecular solar-thermal energy storage (MOST) systems are based on photoswitches that reversibly convert solar energy into chemical energy. In this context, bicyclooctadienes (BODs) undergo a photoinduced transformation to the corresponding higher energy tetracyclooctanes (TCOs), but the photoswitch system has not until now been evaluated for MOST application, due to the short half-life of the TCO form and limited available synthetic methods. The BOD system degrades at higher temperature via a retro-Diels–Alder reaction, which complicates the synthesis of the compounds. We here report a cross-coupling reaction strategy that enables an efficient synthesis of a series of 4 new BOD compounds. We show that the BODs were able to switch to the corresponding tetracyclooctanes (TCOs) in a reversible way and can be cycled 645 times with only 0.01% degradation. Half-lives of the TCOs were measured, and we illustrate how the half-life could be engineered from seconds to minutes by molecular structure design. A density functional theory (DFT) based modelling framework was developed to access absorption spectra, thermal half-lives, and storage energies which were calculated to be 143–153 kJ mol−1 (0.47–0.51 MJ kg−1), up to 76% higher than for the corresponding norbornadiene. The combined computational and experimental findings provide a reliable way of designing future BOD/TCO systems with tailored properties.Molecular solar-thermal energy storage (MOST) systems are based on photoswitches that reversibly convert solar energy into chemical energy. 相似文献
410.
D. D. Khalyavin I. O. Troyanchuk N. V. Kasper H. Szymczak 《Journal of Experimental and Theoretical Physics》2001,93(4):805-808
Slowly cooled Nd1 ? x BaxCoO3 ? δ samples were two-phase in the concentration interval 0.3 ≤ x ≤ 0.46. One of the phases had O-orthorhombic lattice distortions (Pbnm) characteristic of ferromagnetic samples with x ≤ 0.3, and the other phase had tetragonal distortions (P4/mmm) characteristic of samples with x ≥ 0.46. Tetragonal distortions were caused by ordering of Nd3+ and Ba2+ ions. Samples with ordered neodymium and barium ions (Nd1 ? y Ba1 + y Co2O6 ? γ at ?0.08 ≤ y ≤ 0.08) experienced metal-dielectric and orientation magnetic phase transitions. 相似文献