全文获取类型
收费全文 | 235518篇 |
免费 | 6017篇 |
国内免费 | 3687篇 |
专业分类
化学 | 133817篇 |
晶体学 | 2905篇 |
力学 | 10086篇 |
综合类 | 220篇 |
数学 | 26144篇 |
物理学 | 72050篇 |
出版年
2021年 | 1999篇 |
2020年 | 2480篇 |
2019年 | 2518篇 |
2018年 | 3016篇 |
2017年 | 3023篇 |
2016年 | 4430篇 |
2015年 | 3188篇 |
2014年 | 4481篇 |
2013年 | 10020篇 |
2012年 | 9218篇 |
2011年 | 10970篇 |
2010年 | 7687篇 |
2009年 | 7440篇 |
2008年 | 9923篇 |
2007年 | 9887篇 |
2006年 | 9393篇 |
2005年 | 8532篇 |
2004年 | 7520篇 |
2003年 | 6606篇 |
2002年 | 6526篇 |
2001年 | 7144篇 |
2000年 | 5437篇 |
1999年 | 4101篇 |
1998年 | 3339篇 |
1997年 | 3253篇 |
1996年 | 3116篇 |
1995年 | 2842篇 |
1994年 | 2933篇 |
1993年 | 2717篇 |
1992年 | 2947篇 |
1991年 | 2990篇 |
1990年 | 2767篇 |
1989年 | 2657篇 |
1988年 | 2622篇 |
1987年 | 2514篇 |
1986年 | 2522篇 |
1985年 | 3297篇 |
1984年 | 3342篇 |
1983年 | 2790篇 |
1982年 | 3018篇 |
1981年 | 2783篇 |
1980年 | 2582篇 |
1979年 | 2753篇 |
1978年 | 2972篇 |
1977年 | 3009篇 |
1976年 | 3029篇 |
1975年 | 2776篇 |
1974年 | 2886篇 |
1973年 | 2938篇 |
1972年 | 2301篇 |
排序方式: 共有10000条查询结果,搜索用时 890 毫秒
21.
Daulbaev O. Isaenko L. I. Bogdzel’ A. A. Lobanov S. I. Krinitsyn P. G. Milkov V. M. Belushkin A. V. 《Crystallography Reports》2022,67(3):464-469
Crystallography Reports - Two LiInSe2 single crystals, grown under different conditions, have been studied. Characteristics of these crystals for neutron detection have been compared using... 相似文献
22.
Li Quanxin Li Zheng He Cheng Sun Huilin Tan Shengheng Zhang Hua 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(5):2105-2115
Journal of Radioanalytical and Nuclear Chemistry - The simplified 8-oxide system (SiO2-B2O3-Na2O-Al2O3-CaO-TiO2-MoO3-La2O3) has been prepared under two types of cooling methods, and analyzed with... 相似文献
23.
Vasile M. Loots H. Vercammen L. Bruggeman M. Verrezen F. 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(8):3349-3357
Journal of Radioanalytical and Nuclear Chemistry - In this paper a study for the selection of an NPE (nonylphenol ethoxylates)—free cocktail is discussed in order to be used for our routine... 相似文献
24.
Radiophysics and Quantum Electronics - A well-known simplified model of turbulent convection from local sources of buoyancy and/or momentum acting for a short time has been developed and... 相似文献
25.
Li Jun Zheng Dayong Wei Ning Sun Yunfeng Liu Li Yuan Yuan Jiang Qinghua 《Chemistry of Natural Compounds》2022,58(4):650-652
Chemistry of Natural Compounds - A new quassinoid, dehydrobruceantinol B (1), was isolated from the seeds of Brucea javanica, together with two known compounds, bruceantinol (2) and bruceine A (3).... 相似文献
26.
Ukrainian Mathematical Journal - We establish new criteria of compatibility for a linear system of equations (equivalent to the Kronecker–Capelli theorem) or inequalities (equivalent to the... 相似文献
27.
Restricted testing conditions were considered recently. For the maximal operator, Hytönen, Li and Sawyer [8] first obtained parental testing condition. Later, they [9] showed that it suffices to restrict testing to doubling cubes. Chen and Lacey [3] gave a similar restricted testing condition. In our paper, we discuss a version of the latter in the multilinear setting.
相似文献28.
将有机物2,5-二溴对苯二甲酸(H2L1)和2,2′-联吡啶(L2)作为双配体,使用溶剂热法和七水合硫酸锌(ZnSO4·7H2O)、六水合硝酸钴(Co(NO3)2·6H2O)分别反应,得到配合物[Zn(L1)(L2)(H2O)]n(1)和配合物[Co(L1)(L2)(H2O)]n(2)。采用单晶X射线衍射、元素分析、红外光谱、紫外光谱、荧光光谱、热重分析等测试方法对这两种物质进行分析研究。单晶测试结果表明配合物1是单斜晶系,以Zn2+配位连接L2-1与L2形成一维链状结构,各条链在分子间氢键和π…π共轭作用下有规律地堆叠形成三维网络结构。配合物2是三斜晶系,Co1离子和Co1i离子由H2L1上的羧酸氧原子O4和O4i连接,形成双齿螯合的配位结构单元,以Co2+配位连接 L2-1和L2形成二维网格结构,各层在O—H…O分子间氢键和范德瓦耳斯力作用下有规律的堆叠形成三维网络结构。配合物1和2均含有芳香杂环、羧基杂环和氮杂环,具有良好的荧光性质和热稳定性,最大发射波长分别为345 nm和333 nm。 相似文献
29.
Dzhun I. O. Babaitsev G. V. Kozin M. G. Romashkina I. L. Shanova E. I. Chechenin N. G. 《Physics of the Solid State》2021,63(6):825-831
Physics of the Solid State - The external factors which influence the ferromagnetic resonance (FMR) line width in bilayer (ferromagnet/antiferromagnet) exchange-biased systems are studied. The... 相似文献
30.
Corinne Rondeau-Mouro Mireille Cambert Laurent Blondel Yves Diascorn Léo Mbaya Nor Nadiah Binti Ahmad Nazari Sarah Helary Tiphaine Lucas 《Magnetic resonance in chemistry : MRC》2022,60(7):678-691
A temperature control unit was implemented to vary the temperature of samples studied on a commercial Mobile Universal Surface Explorer nuclear magnetic resonance (MOUSE-NMR) apparatus. The device was miniaturized to fit the maximum MOUSE sampling depth (25 mm). It was constituted by a sample holder sandwiched between two heat exchangers placed below and above the sample. Air was chosen as the fluid to control the temperature at the bottom of the sample, at the interface between the NMR probe and the sample holder, in order to gain space. The upper surface of the sample was regulated by the circulation of water inside a second heat exchanger placed above the sample holder. The feasibility of using such a device was demonstrated first on pure water and then on several samples of bread dough with different water contents. For this, T1 relaxation times were measured at various temperatures and depths and were then compared with those acquired with a conventional compact closed-magnet spectrometer. Discussion of results was based on biochemical transformations in bread dough (starch gelatinization and gluten heat denaturation). It was demonstrated that, within a certain water level range, and because of the low magnetic field strength of the MOUSE, a linear relationship could be established between T1 relaxation times and the local temperature in the dough sample. 相似文献