全文获取类型
收费全文 | 88226篇 |
免费 | 407篇 |
国内免费 | 383篇 |
专业分类
化学 | 24679篇 |
晶体学 | 803篇 |
力学 | 6750篇 |
数学 | 32042篇 |
物理学 | 15186篇 |
无线电 | 9556篇 |
出版年
2021年 | 44篇 |
2020年 | 33篇 |
2019年 | 35篇 |
2018年 | 11835篇 |
2017年 | 11464篇 |
2016年 | 6978篇 |
2015年 | 933篇 |
2014年 | 387篇 |
2013年 | 415篇 |
2012年 | 4225篇 |
2011年 | 11722篇 |
2010年 | 6875篇 |
2009年 | 6817篇 |
2008年 | 7240篇 |
2007年 | 9661篇 |
2006年 | 280篇 |
2005年 | 1642篇 |
2004年 | 1809篇 |
2003年 | 2214篇 |
2002年 | 1106篇 |
2001年 | 271篇 |
2000年 | 316篇 |
1999年 | 169篇 |
1998年 | 211篇 |
1997年 | 148篇 |
1996年 | 200篇 |
1995年 | 119篇 |
1994年 | 77篇 |
1993年 | 96篇 |
1992年 | 61篇 |
1991年 | 66篇 |
1990年 | 54篇 |
1989年 | 61篇 |
1988年 | 61篇 |
1987年 | 59篇 |
1986年 | 57篇 |
1985年 | 49篇 |
1984年 | 43篇 |
1983年 | 36篇 |
1982年 | 41篇 |
1981年 | 41篇 |
1980年 | 46篇 |
1979年 | 44篇 |
1978年 | 34篇 |
1914年 | 45篇 |
1913年 | 40篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 40篇 |
1907年 | 32篇 |
排序方式: 共有10000条查询结果,搜索用时 2 毫秒
971.
972.
973.
Christian-Robert Raddatz Maria Allers Ansgar T. Kirk Stefan Zimmermann 《International Journal for Ion Mobility Spectrometry》2018,21(3):49-53
Measuring a mixture of acetone and perdeuterated acetone (acetone-d6) with an ultra-high resolution drift time ion mobility spectrometer (resolving power of Rp?=?235) and ultraviolet ionization (10.6 eV) at ambient pressure reveals three separated peaks. Two of the peaks can easily be associated with acetone and perdeuterated acetone. In a former publication several findings indicated an exchange of a methyl group and the formation of a H3COCD3 related peak. In this work the formed ion species were analyzed with a high resolution drift time ion mobility time of flight mass spectrometer. The mass spectra clearly show the formation of three proton-bound dimer peaks whereas the peak between acetone and acetone-d6 is a proton-bound mixed dimer consisting of one acetone and one acetone-d6 molecule. 相似文献
974.
Nivedita Bhadra 《The European Physical Journal B - Condensed Matter and Complex Systems》2018,91(1):13
We show a noise induced transition in Josephson junction with fundamental as well as second harmonic. A periodically modulated multiplicative colored noise can stabilize an unstable configuration in such a system. The stabilization of the unstable configuration has been captured in the effective potential of the system obtained by integrating out the high frequency components of the noise. This is a classical approach to understand the stability of an unstable configuration due to the presence of such stochasticity in the system and our numerical analysis confirms the prediction from the analytical calculation. 相似文献
975.
976.
Seyedeh Hoda Jazayeri Amir Amiri-Yekta Salahadin Bahrami Hamid Gourabi Mohammad Hossein Sanati Mohammad Reza Khorramizadeh 《Applied biochemistry and biotechnology》2018,185(4):986-1003
The rapid growth of global biopharmaceutical market in the recent years has been a good indication of its significance in biotechnology industry. During a long period of time in recombinant protein production from 1980s, optimizations in both upstream and downstream processes were launched. In this regard, one of the most promising strategies is expression vector engineering technology based on incorporation of DNA opening elements found in the chromatin border regions of vectors as well as targeting gene integration. Along with these approaches, cell line engineering has revealed convenient outcomes in isolating high-producing clones. According to the fact that more than 50% of the approved therapeutic proteins is being manufactured in mammalian cell lines, in this review, we focus on several approaches and developments in vector and cell line engineering technologies in mammalian cell culture. 相似文献
977.
Edward R. Adlard 《Chromatographia》2018,81(12):1713-1713
978.
979.
980.
Andrzej Mianowski Izabela Baraniec-Mazurek Rafał Bigda 《Journal of Thermal Analysis and Calorimetry》2012,107(3):1155-1165
For dehydration of CaC2O4·H2O and thermal dissociation of CaCO3 carried out in Mettler Toledo TGA/SDTA-851e/STARe thermobalance similar experimental conditions was applied: 9–10 heating rates, q = 0.2, 0.5, 1, 2, 3, 6, 12, 24, 30, and 36 K min−1, for sample mass 10 mg, in nitrogen atmosphere (100 ml min−1) and in Al2O3 crucibles (70 μl). There were analyzed changes of typical TGA quantities, i.e., T, TG and DTG in the form of the relative
rate of reaction/process intended to be analyzed on-line by formula (10). For comparative purposes, the relationship between experimental and equilibrium conversion degrees was used (for
P = P\ominus P = P^{{\ominus}} ). It was found that the solid phase decomposition proceeds in quasi-equilibrium state and enthalpy of reaction is easily
“obscured” by activation energy. For small stoichiometric coefficients on gas phase side (here: ν = 1) discussed decomposition
processes have typical features of phenomena analyzable by known thermokinetic methods. 相似文献