全文获取类型
收费全文 | 2153篇 |
免费 | 67篇 |
国内免费 | 4篇 |
专业分类
化学 | 1655篇 |
晶体学 | 4篇 |
力学 | 18篇 |
数学 | 326篇 |
物理学 | 221篇 |
出版年
2023年 | 29篇 |
2022年 | 15篇 |
2021年 | 23篇 |
2020年 | 61篇 |
2019年 | 50篇 |
2018年 | 27篇 |
2017年 | 17篇 |
2016年 | 40篇 |
2015年 | 28篇 |
2014年 | 39篇 |
2013年 | 67篇 |
2012年 | 68篇 |
2011年 | 95篇 |
2010年 | 38篇 |
2009年 | 44篇 |
2008年 | 69篇 |
2007年 | 62篇 |
2006年 | 71篇 |
2005年 | 68篇 |
2004年 | 55篇 |
2003年 | 43篇 |
2002年 | 38篇 |
2001年 | 18篇 |
2000年 | 22篇 |
1999年 | 15篇 |
1998年 | 18篇 |
1996年 | 14篇 |
1995年 | 20篇 |
1994年 | 20篇 |
1991年 | 21篇 |
1990年 | 16篇 |
1987年 | 15篇 |
1986年 | 17篇 |
1985年 | 27篇 |
1984年 | 29篇 |
1983年 | 25篇 |
1982年 | 38篇 |
1981年 | 22篇 |
1980年 | 24篇 |
1979年 | 42篇 |
1978年 | 25篇 |
1977年 | 36篇 |
1976年 | 26篇 |
1975年 | 24篇 |
1974年 | 20篇 |
1973年 | 14篇 |
1967年 | 19篇 |
1959年 | 14篇 |
1956年 | 20篇 |
1934年 | 23篇 |
排序方式: 共有2224条查询结果,搜索用时 15 毫秒
91.
92.
Joerg Max Siebert Grit Baier Katharina Landfester 《Journal of polymer science. Part A, Polymer chemistry》2012,50(1):80-88
A new class of polyurethanes has been designed, containing tertiary carbamate groups in the main chain of the polymer, which enable the resulting polymer to degrade completely under acid and thermal treatment. The decomposition temperatures of the polymers were determined by measuring the evolution of carbon dioxide and other decomposition products using TGA‐MS. Until decomposition of the polymer, no glass transition was found. The polymers exhibit excellent solubility in common organic solvents like chloroform and tetrahydrofuran, making them to suitable materials for film formation. From the obtained polymers, nanoparticles were synthesized by the solvent evaporation method combined with the miniemulsion technique. The resulting nanoparticles can be used as intelligent fillers in films and sensors, since they degrade at temperatures of above 180 °C, which can be detected by a color change reaction with ninhydrin. Polymeric nanocapsules were prepared by an interfacial polyaddition reaction from 2,4‐toluene diisocyanate and tertiary diols performed at the droplet's interface in inverse (water‐in‐oil) miniemulsions. These nanocapsules with an encapsulated photoacid generator can act as a release system, whereby an acidic release through irradiation with ultraviolet light can be triggered. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
93.
Yingshuai Zhao Xiaobo Zhao Zuo-Jun Max Shen 《The Journal of the Operational Research Society》2016,67(9)
A behavioural study on the newsvendor problem without demand distribution knowledge or realized demands is conducted. We configure a censored-information scenario, where only sales data in history are provided. With laboratory experiments, we analyse participants ordering levels and ordering oscillations over time. It is observed that participants perform a significant learning process in the censored-information scenario. Moreover, we find that participants make orders by anchoring on the previous-period sales and adjusting to an adapted inventory level. On the basis of the observations, we propose an exponential-type learning (EXP) model to describe the behaviour of decision makers. Comparing with a chasing model that is popularly used in the full-information scenario, the EXP model is more recommended in the censored-information scenario. 相似文献
94.
Afshin Nabiyan Johannes Bernhard Max Dr. Christof Neumann Magdalena Heiland Prof. Dr. Andrey Turchanin Prof. Dr. Carsten Streb Prof. Dr. Felix Helmut Schacher 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(68):16924-16929
An effective strategy to enhance the performance of inorganic semiconductors is moving towards organic-inorganic hybrid materials. Here, we report the design of core–shell hybrid materials based on a TiO2 core functionalized with a polyampholytic (poly(dehydroalanine)-graft-(n-propyl phosphonic acid acrylamide) shell (PDha-g-PAA@TiO2). The PDha-g-PAA shell facilitates the efficient immobilization of the photosensitizer Eosin Y (EY) and enables electronic interactions between EY and the TiO2 core. This resulted in high visible-light-driven H2 generation. The enhanced light-driven catalytic activity is attributed to the unique core–shell design with the graft copolymer acting as bridge and facilitating electron and proton transfer, thereby also preventing the degradation of EY. Further catalytic enhancement of PDha-g-PAA@TiO2 was possible by introducing [Mo3S13]2− cluster anions as hydrogen-evolution cocatalyst. This novel design approach is an example for a multi-component system in which reactivity can in future be independently tuned by selection of the desired molecular or polymeric species. 相似文献
95.
Morgan and Culler proved that a minimal action of a free group on a tree is determined by its translation length function. We prove an analogue of this theorem for 2-dimensional right-angled Artin groups acting on CAT(0) rectangle complexes. 相似文献
96.
97.
We show that an arbitrary infinite graph G can be compactified by its ends plus its critical vertex sets, where a finite set X of vertices of an infinite graph is critical if its deletion leaves some infinitely many components each with neighbourhood precisely equal to X. We further provide a concrete separation system whose ?0‐tangles are precisely the ends plus critical vertex sets. Our tangle compactification is a quotient of Diestel's (denoted by ), and both use tangles to compactify a graph in much the same way as the ends of a locally finite and connected graph compactify it in its Freudenthal compactification. Finally, generalising both Diestel's construction of and our construction of , we show that G can be compactified by every inverse limit of compactifications of the sets of components obtained by deleting a finite set of vertices. Diestel's is the finest such compactification, and our is the coarsest one. Both coincide if and only if all tangles are ends. This answers two questions of Diestel. 相似文献
98.
Pierre Garcia Dr. Yannick Evanno Dr. Pascal George Dr. Mireille Sevrin Dr. Gino Ricci Prof. Dr. Max Malacria Dr. Corinne Aubert Prof. Dr. Vincent Gandon 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(14):4337-4344
An in‐depth study of the cobalt‐catalyzed [2+2+2] cycloaddition between yne‐ynamides and nitriles to afford aminopyridines has been carried out. About 30 nitriles exhibiting a broad range of steric demand and electronic properties have been evaluated, some of which open new perspectives in metal‐catalyzed arene formation. In particular, the use of [CpCo(CO)(dmfu)] (dmfu=dimethyl fumarate) as a precatalyst made possible the incorporation of electron‐deficient nitriles into the pyridine core. Modification of the substitution pattern at the yne‐ynamide allows the regioselectivity to be switched toward 3‐ or 4‐aminopyridines. Application of this synthetic methodology to the construction of the aminopyridone framework using a yne‐ynamide and an isocyanate was also briefly examined. DFT computations suggest that 3‐aminopyridines are formed by formal [4+2] cycloaddition between the nitrile and the intermediate cobaltacyclopentadiene, whereas 4‐aminopyridines arise from an insertion pathway. 相似文献
99.
Eckhard Weissflog Max Schmidt 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3):383-384
Abstract The reaction of bromine with trimeric thioacetic aldehyde leads to the formation of the title compound which may be used as starting material for the synthesis of new methyl-substituted cyclic and linear thioalkanes. 相似文献
100.
Anne-Marie Caminade Fayez El Khatib Antoine Baceiredo Max Koenig 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2-4):365-367
Abstract The ozonization of various halophosphines 1a-j leads with quantitative yields to the corresponding phosphine oxides 2a-j. Ozonization is a convenient method of oxidation, in particular of compounds with bulky ligands (1c, 1d, 1e). 相似文献