全文获取类型
收费全文 | 3751篇 |
免费 | 259篇 |
国内免费 | 113篇 |
专业分类
化学 | 2500篇 |
晶体学 | 23篇 |
力学 | 132篇 |
数学 | 672篇 |
物理学 | 796篇 |
出版年
2023年 | 38篇 |
2022年 | 32篇 |
2021年 | 54篇 |
2020年 | 72篇 |
2019年 | 81篇 |
2018年 | 59篇 |
2017年 | 58篇 |
2016年 | 104篇 |
2015年 | 108篇 |
2014年 | 120篇 |
2013年 | 228篇 |
2012年 | 198篇 |
2011年 | 190篇 |
2010年 | 139篇 |
2009年 | 113篇 |
2008年 | 182篇 |
2007年 | 174篇 |
2006年 | 139篇 |
2005年 | 142篇 |
2004年 | 118篇 |
2003年 | 107篇 |
2002年 | 110篇 |
2001年 | 70篇 |
2000年 | 61篇 |
1999年 | 47篇 |
1998年 | 48篇 |
1997年 | 52篇 |
1996年 | 54篇 |
1995年 | 40篇 |
1994年 | 41篇 |
1993年 | 47篇 |
1992年 | 51篇 |
1991年 | 35篇 |
1990年 | 46篇 |
1989年 | 35篇 |
1988年 | 48篇 |
1987年 | 43篇 |
1985年 | 56篇 |
1984年 | 45篇 |
1983年 | 54篇 |
1982年 | 53篇 |
1981年 | 41篇 |
1980年 | 54篇 |
1979年 | 51篇 |
1978年 | 44篇 |
1977年 | 49篇 |
1976年 | 47篇 |
1975年 | 33篇 |
1974年 | 41篇 |
1973年 | 34篇 |
排序方式: 共有4123条查询结果,搜索用时 171 毫秒
1.
A nanomaterials-based novel molecular beacon has attracted growing attentions in fluorescent assays as many nanomaterials possess excellent quenching efficiency. In this work, a gold-based nanobeacon probe was established to detect organophosphorus pesticides for the first time. The constructed gold-based nanobeacon acted as a signal indicator and could display the decreasing of the intensity in the presence of targets, which competitively bound to single strand DNA. To achieve a high sensitive probe, some parameters including solution pH, temperature and reaction time were investigated and optimized. The gold-based nanobeacon probe assay was proved to be rapid and sensitive to achieve a detection limit of 0.035 μM for isocarbophos, 0.134 μM for profenofos, 0.384 μM for phorate and 2.35 μM for omethoate, respectively. The prepared nanobeacon effectively reduced the background and improved the detection sensitivity and selectivity. The probe is stable, easy to operate and does not need sophisticated instruments. These features makes the probe feasible for screening trace organophosphorus pesticides in real samples. 相似文献
2.
Vieira Renata Leia Demario Gaglieri Caroline de Oliveira Cristina Soltovski Ferreira Laura Teófilo Schnitzler Egon Bannach Gilbert 《Journal of Thermal Analysis and Calorimetry》2021,144(3):689-697
Journal of Thermal Analysis and Calorimetry - Buckwheat starch is an alternative source to supply the high global demand for starch. The properties of starch can be modified through chemical and... 相似文献
3.
Lithium Insertion Mechanism in Iron-Based Oxyfluorides with Anionic Vacancies Probed by PDF Analysis
Dr. Damien Dambournet Dr. Karena W Chapman Dr. Mathieu Duttine Dr. Olaf Borkiewicz Dr. Peter J Chupas Dr. Henri Groult 《ChemistryOpen》2015,4(4):443-447
The mechanism of lithium insertion that occurs in an iron oxyfluoride sample with a hexagonal–tungsten–bronze (HTB)-type structure was investigated by the pair distribution function. This study reveals that upon lithiation, the HTB framework collapses to yield disordered rutile and rock salt phases followed by a conversion reaction of the fluoride phase toward lithium fluoride and nanometer-sized metallic iron. The occurrence of anionic vacancies in the pristine framework was shown to strongly impact the electrochemical activity, that is, the reversible capacity scales with the content of anionic vacancies. Similar to FeOF-type electrodes, upon de-lithiation, a disordered rutile phase forms, showing that the anionic chemistry dictates the atomic arrangement of the re-oxidized phase. Finally, it was shown that the nanoscaling and structural rearrangement induced by the conversion reaction allow the in situ formation of new electrode materials with enhanced electrochemical properties. 相似文献
4.
Yaping Chen Dr. Kun Rui Prof. Jixin Zhu Prof. Shi Xue Dou Dr. Wenping Sun 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(3):703-713
Developing clean and sustainable energies as alternatives to fossil fuels is in strong demand within modern society. The oxygen evolution reaction (OER) is the efficiency-limiting process in plenty of key renewable energy systems, such as electrochemical water splitting and rechargeable metal–air batteries. In this regard, ongoing efforts have been devoted to seeking high-performance electrocatalysts for enhanced energy conversion efficiency. Apart from traditional precious-metal-based catalysts, nickel-based compounds are the most promising earth-abundant OER catalysts, attracting ever-increasing interest due to high activity and stability. In this review, the recent progress on nickel-based oxide and (oxy)hydroxide composites for water oxidation catalysis in terms of materials design/synthesis and electrochemical performance is summarized. Some underlying mechanisms to profoundly understand the catalytic active sites are also highlighted. In addition, the future research trends and perspectives on the development of Ni-based OER electrocatalysts are discussed. 相似文献
5.
6.
7.
Thorsten Brand Kyle Ratinac Jeffrey V. Castro Robert G. Gilbert 《Journal of polymer science. Part A, Polymer chemistry》2004,42(22):5706-5713
A method was developed for free‐radical polymerization in the confines of a hollow latex particle. Hollow particles were prepared via the dynamic swelling method from polystyrene seed and divinylbenzene and had hollows of 500–1000 nm. So that these hollow poly(divinylbenzene) particles could function as submicrometer reactors, the particles were filled with a monomer (N‐isopropylacrylamide) via the dispersion of the dried particles in the molten monomer. The monomer that was not contained in the hollows was removed by washing and gentle abrasion. Free‐radical polymerization was then initiated by γ radiolysis in the solid state. Transmission electron microscopy showed that poly(N‐isopropylacrylamide) formed in the hollow interior of the particles, which functioned as submicrometer reactors. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5706–5713, 2004 相似文献
8.
Franck D'Agosto Marie‐Thrse Charreyre Christian Pichot Robert G. Gilbert 《Journal of polymer science. Part A, Polymer chemistry》2003,41(9):1188-1195
A method is described for synthesizing latex particles with anchored hairs by the grafting of hydrophilic chains, synthesized by reversible addition–fragmentation chain transfer, onto functionalized latex particles. These have the potential to bind biologically active species. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1188–1195, 2003 相似文献
9.
10.
K A Dowsland M Gilbert G Kendall 《The Journal of the Operational Research Society》2007,58(4):429-438
This paper is concerned with the development of a customized circle packing algorithm for a manufacturer of sprockets for the motor cycle industry. Practical constraints mean that the problem differs somewhat from those tackled elsewhere in the literature. In particular, the layouts need to conform to a given structure. This is achieved by using a local search algorithm with an appropriate starting solution and a series of neighbourhoods designed to preserve the layout structure. Empirical evidence based on real data shows that the quality of the resulting solutions closely matches that of cutting patterns currently produced by human experts. Computation times average around 20–30?s per order as compared to several hours for an equivalent manual solution. 相似文献