全文获取类型
收费全文 | 274860篇 |
免费 | 4324篇 |
国内免费 | 1576篇 |
专业分类
化学 | 147314篇 |
晶体学 | 3239篇 |
力学 | 12550篇 |
综合类 | 94篇 |
数学 | 30644篇 |
物理学 | 86919篇 |
出版年
2020年 | 2481篇 |
2019年 | 2701篇 |
2018年 | 3455篇 |
2017年 | 3439篇 |
2016年 | 4985篇 |
2015年 | 3128篇 |
2014年 | 4809篇 |
2013年 | 11402篇 |
2012年 | 8962篇 |
2011年 | 10890篇 |
2010年 | 7698篇 |
2009年 | 7521篇 |
2008年 | 9944篇 |
2007年 | 10062篇 |
2006年 | 9377篇 |
2005年 | 8495篇 |
2004年 | 7742篇 |
2003年 | 7001篇 |
2002年 | 6899篇 |
2001年 | 7516篇 |
2000年 | 5862篇 |
1999年 | 4558篇 |
1998年 | 4064篇 |
1997年 | 4030篇 |
1996年 | 3452篇 |
1995年 | 3425篇 |
1994年 | 3546篇 |
1993年 | 3200篇 |
1992年 | 3656篇 |
1991年 | 3650篇 |
1990年 | 3591篇 |
1989年 | 3439篇 |
1988年 | 3500篇 |
1987年 | 3426篇 |
1986年 | 3228篇 |
1985年 | 4304篇 |
1984年 | 4590篇 |
1983年 | 3820篇 |
1982年 | 3945篇 |
1981年 | 3857篇 |
1980年 | 3838篇 |
1979年 | 3809篇 |
1978年 | 4140篇 |
1977年 | 4060篇 |
1976年 | 4128篇 |
1975年 | 3799篇 |
1974年 | 3862篇 |
1973年 | 4005篇 |
1972年 | 2822篇 |
1971年 | 2350篇 |
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
1.
Journal of Fluorescence - This report describes a combined immunofluorescence and fluorescence viability stain applied as one staining solution for rapid detection of live Legionella... 相似文献
2.
Kinetics and Catalysis - The catalytic properties of a nickel phosphide catalyst supported on silica gel in the reductive amination of carbonyl compounds were studied in a flow reactor using... 相似文献
3.
Chuprin A. S. Belova S. A. Bugaenko M. G. Vologzhanina A. V. Loktev A. S. Voloshin Ya. Z. Buznik V. M. Dedov A. G. 《Kinetics and Catalysis》2022,63(1):108-116
Kinetics and Catalysis - A new ruthenium(II) cage complex with polar terminal groups in the apical substituents has been synthesized; the molecular design of the complex contributes to the... 相似文献
4.
Automotive proton exchange membrane fuel cell stacks need to meet manufacturer specified rated beginning-of-life (BOL) performance before being assembled into vehicles and shipped off to customers. The process of “breaking-in” of a freshly assembled stack is often referred to as “conditioning.” It has become an intensely researched area especially in automotive companies, where imminent commercialization of fuel cell electric vehicles (FCEVs) demands a short, energy- and cost-efficient, and practical conditioning protocol. Significant advances in reducing the conditioning time from 1 to 2 days to as low as 4h or less, in some cases without the use of additional inert gases such as nitrogen, and with minimal use of hydrogen, and specialized test stations will be discussed. 相似文献
5.
Nonlinear Dynamics - The perovskite solar cell (PSC) is one of the most promising photovoltaic candidates along with the highly increasing demand for green electricity. One of the main concerns... 相似文献
6.
Sakhautdinova G. F. Sakhautdinov I. M. Mustafin A. G. Yunusov M. S. 《Chemistry of Natural Compounds》2022,58(1):185-186
Chemistry of Natural Compounds - 相似文献
7.
Chemistry of Natural Compounds - O- and N-propylamino-derivatives of betulin and betulonic acid oxime and methyl ester were synthesized. Their antitumor activity against a panel of 60 human cancer... 相似文献
8.
Romanenko G. V. Fokin S. V. Bogomyakov A. S. Zueva E. M. Ovcharenko V. I. 《Journal of Structural Chemistry》2022,63(3):441-450
Journal of Structural Chemistry - The structures of Ni(II), Cu(II), and Zn(II) complexes with anions of 2,5-pyrrolyl-disubstituted nitronyl nitroxide (L1) and iminonitroxide (L2) diradicals (HL1 is... 相似文献
9.
Saqib Kamal Arif I. Inamdar Kuan-Ru Chiou Batjargal Sainbileg Muhammad Usman Jenq-Wei Chen Tzuoo-Tsair Luo Michitoshi Hayashi Chen-Hsiung Hung Wen-Feng Liaw Kuang-Lieh Lu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(30):e202103905
The dielectric properties of coordination polymers has been a topic of recent interest, but the role of different functional groups on the dielectric properties of these polymers has not yet been fully addressed. Herein, the effects of electron-donating (R=NH2) and electron-withdrawing (R=NO2) groups on the dielectric behavior of such materials were investigated for two thermally stable and guest-free Zn-based coordination polymers, [Zn(L1)(L2)]n ( 1 ) and [Zn(L1)(L3)]n ( 2 ) [L1=2-(2-pyridyl) benzimidazole (Pbim), L2=5-aminoisophthalate (Aip), and L3=5-nitroisophthalate (Nip)]. The results of dielectric studies of 1 revealed that it possesses a high dielectric constant (κ=65.5 at 1 kHz), while compound 2 displayed an even higher dielectric constant (κ=110.3 at 1 kHz). The electron donating and withdrawing effects of the NH2 and NO2 substituents induce changes in the polarity of the polymers, which is due to the inductive effect from the aryl ring for both NO2 and NH2. Theoretical results from density functional theory (DFT) calculations, which also support the experimental findings, show that both compounds have a distinct electronic behavior with diverse wide bandgaps. The significance of the current work is to provide information about the structure-dielectric property relationships. So, this study promises to pave the way for further research on the effects of different functional groups on coordination polymers on their dielectric properties. 相似文献
10.
Cellulose - In this research, the production of levoglucosan (LG) and levoglucosenone (LGO) was improved from acid-impregnated cellulose via fast pyrolysis. Thermogravimetric and kinetic analysis... 相似文献