全文获取类型
收费全文 | 1837篇 |
免费 | 77篇 |
国内免费 | 5篇 |
专业分类
化学 | 956篇 |
晶体学 | 25篇 |
力学 | 116篇 |
数学 | 453篇 |
物理学 | 369篇 |
出版年
2023年 | 21篇 |
2022年 | 25篇 |
2021年 | 26篇 |
2020年 | 50篇 |
2019年 | 58篇 |
2018年 | 67篇 |
2017年 | 58篇 |
2016年 | 103篇 |
2015年 | 71篇 |
2014年 | 94篇 |
2013年 | 306篇 |
2012年 | 79篇 |
2011年 | 83篇 |
2010年 | 69篇 |
2009年 | 65篇 |
2008年 | 55篇 |
2007年 | 57篇 |
2006年 | 67篇 |
2005年 | 26篇 |
2004年 | 45篇 |
2003年 | 22篇 |
2002年 | 28篇 |
2001年 | 31篇 |
2000年 | 19篇 |
1999年 | 27篇 |
1998年 | 23篇 |
1997年 | 28篇 |
1996年 | 21篇 |
1995年 | 19篇 |
1994年 | 23篇 |
1993年 | 15篇 |
1992年 | 11篇 |
1990年 | 9篇 |
1989年 | 8篇 |
1988年 | 13篇 |
1987年 | 9篇 |
1985年 | 15篇 |
1984年 | 12篇 |
1983年 | 11篇 |
1982年 | 8篇 |
1981年 | 15篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1975年 | 10篇 |
1974年 | 5篇 |
1973年 | 5篇 |
1971年 | 5篇 |
1927年 | 5篇 |
排序方式: 共有1919条查询结果,搜索用时 203 毫秒
991.
Özalp VC 《The Analyst》2011,136(23):5046-5050
A quartz crystal microbalance with a dissipation monitoring (QCM-D) sensor was developed for highly sensitive and specific detection of adenosine-5'-triphosphate (ATP) by using an aptamer. The binding of ATP molecules on the aptamer films could be calculated as accurate mass changes using multiple frequency and dissipation measurements. The detection is achieved by calculating the mass changes from conformational rearrangements of the sensor surface upon interaction with the target. The sensor was demonstrated to respond to changes in ATP concentrations in real time suitable for continuous monitoring applications. This sensor showed excellent selectivity toward ATP compared with other chemically similar nucleotide GTP. The feasibility of the sensor was demonstrated by analyzing ATP concentrations in cell culture media with serum. The maximum frequency change was about -2 Hz after injection of 500 μM ATP. The affinity constant of the aptamer was determined to be 49 ± 7.59 μM. The proposed sensor can extend the application of the QCM-D system in medical diagnosis, and could be adopted for the detection of other small molecules with the use of specific aptamers. 相似文献
992.
Dr. Sevi Öz Ingrid Svoboda Raif Kurtaran Mecit Aksu Musa Sari Melike Kunduraci Orhan Atakol 《无机化学与普通化学杂志》2011,637(2):257-262
Nine CuII complexes ( I – IX ) containing the azide ion and bis‐2,6‐(pyrazol‐1‐yl)pyridine (pp), bis‐2,6‐(pyrazol‐1‐yl)pyridine (dmpp), and 2‐(pyrazol‐1‐yl)‐6‐(3,5‐dimethylpyrazol‐1‐yl)pyridine (mpp), which are derivatives of pyrazolylpyridine, were prepared in nonaqueous medium. These complexes were characterized by elemental analyses and IR spectroscopy. Crystals of one of these complexes [CumppClN3 ( VII )] were prepared in suitable size, and a molecular structure of this complex was obtained with X‐ray diffraction method. Complexes were examined by thermogravimetry and differential scanning calorimetry methods. Thermal decomposition was observed in complexes including two azide groups similar to that seen in explosives. In the complexes containing one azide group, formation of the CuI complexes was observed after thermal decomposition of the azide group. 相似文献
993.
Faruk Yigit 《Applied mathematics and computation》2011,217(14):6541-6555
A finite difference method is used to solve a one-dimensional solidification problem with a periodic boundary condition prescribed at the bottom of the mold of finite thickness. The temperature distributions in the solidified shell and mold, the position of the moving freezing front, and its velocity are evaluated. Analytical results are obtained for the limiting cases and then compared with the numerical predictions to establish the validity of the model and the numerical approach. Interactive effects of the process parameters such as Stefan number of the solidified shell material, the mold thickness, the thermal conductivity and thermal diffusivity between the shell and mold materials on the evolution of the freezing front and its velocity are investigated in detail. The results show that the solidified materials with larger Stefan number grow slower than those with relatively smaller Stefan number. The impact of oscillating mold temperature boundary on the growth of shell thickness is particularly significant at earlier stages of the process and more pronounced for smaller Stefan numbers. Increasing mold thickness or thermal conductivity ratio between the shell and mold materials slows down the evolution of the shell thickness. 相似文献
994.
Fixed points of <Emphasis Type="Italic">IA</Emphasis>-endomorphisms of a free metabelian Lie algebra
Let L be a free metabelian Lie algebra of finite rank at least 2. We show the existence of non-trivial fixed points of an IA-endomorphism of L and give an algorithm detecting them. In particular, we prove that the fixed point subalgebra Fix φ of an IA-endomorphism φ of L is not finitely generated. 相似文献
995.
996.
997.
998.
The use of a low finesse enhancement cavity resonant with a low average power (<1 W) and a high repetition rate (78 MHz) pump source is shown to achieve 55% conversion efficiency into signal and idler from the coupled pump in an optical parametric process, whereas an equivalent amount of pump power in a single-pass configuration leads to negligible conversion. Careful comparison of the intracavity conversion process to the single-pass case is performed to assess the underlying impedance matching that yields the high conversion results. 相似文献
999.
1000.
Kärkäs MD Johnston EV Karlsson EA Lee BL Åkermark T Shariatgorji M Ilag L Hansson Ö Bäckvall JE Åkermark B 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(28):7953-7959
The new Ru complex 8 containing the bio-inspired ligand 7 was successfully synthesized and characterized. Complex 8 efficiently catalyzes water oxidation using Ce(IV) and Ru(III) as chemical oxidants. More importantly, this complex has a sufficiently low overpotential to utilize ruthenium polypyridyl-type complexes as photosensitizers. 相似文献