全文获取类型
收费全文 | 346109篇 |
免费 | 9689篇 |
国内免费 | 6985篇 |
专业分类
化学 | 177492篇 |
晶体学 | 4590篇 |
力学 | 17802篇 |
综合类 | 454篇 |
数学 | 51963篇 |
物理学 | 110482篇 |
出版年
2021年 | 2678篇 |
2020年 | 3157篇 |
2019年 | 3357篇 |
2018年 | 12105篇 |
2017年 | 13026篇 |
2016年 | 9227篇 |
2015年 | 5083篇 |
2014年 | 5921篇 |
2013年 | 11848篇 |
2012年 | 15048篇 |
2011年 | 24555篇 |
2010年 | 15867篇 |
2009年 | 15858篇 |
2008年 | 21614篇 |
2007年 | 24522篇 |
2006年 | 10735篇 |
2005年 | 15674篇 |
2004年 | 11420篇 |
2003年 | 10421篇 |
2002年 | 8442篇 |
2001年 | 7753篇 |
2000年 | 6086篇 |
1999年 | 4314篇 |
1998年 | 3517篇 |
1997年 | 3419篇 |
1996年 | 3535篇 |
1995年 | 3002篇 |
1994年 | 3027篇 |
1993年 | 2812篇 |
1992年 | 3002篇 |
1991年 | 3050篇 |
1990年 | 2840篇 |
1989年 | 2710篇 |
1988年 | 2683篇 |
1987年 | 2599篇 |
1986年 | 2609篇 |
1985年 | 3390篇 |
1984年 | 3442篇 |
1983年 | 2884篇 |
1982年 | 3107篇 |
1981年 | 2871篇 |
1980年 | 2675篇 |
1979年 | 2873篇 |
1978年 | 3094篇 |
1977年 | 3051篇 |
1976年 | 3099篇 |
1975年 | 2835篇 |
1974年 | 2942篇 |
1973年 | 3034篇 |
1972年 | 2344篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
21.
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
22.
Wei Yuting Wang Qihua Liu Wei 《Annals of the Institute of Statistical Mathematics》2021,73(3):535-553
Annals of the Institute of Statistical Mathematics - In this paper, a model averaging approach is developed for the linear regression models with response missing at random. It is shown that the... 相似文献
23.
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
24.
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25.
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
26.
Donglei Wei Huili Li Chuanqing Yang Jianmin Fu Hou Chen Liangjiu Bai Wenxiang Wang Huawei Yang Lixia Yang Ying Liang 《Journal of polymer science. Part A, Polymer chemistry》2022,60(10):1588-1594
Acridone as a new kind of visible light photocatalyst has been developed to catalyze metal free atom transfer radical polymerization (ATRP). The photocatalyst possess low excited state potential as can undergo an oxidative quenching pathway to initiate ATRP of vinyl monomers. Kinetic study and light on/off reaction demonstrate the “living”/controlled nature of the polymerization by light. Block copolymers can be achieved by using PMMA as macroinitiator to reinitiate polymerization of other vinyl monomers, which shows highly preserved Br chain-end functionality in the synthesized polymers. Moreover, the polymerization can be conducted under air atmosphere as most photocatalysts need anaerobic condition, which may give inspiration of further application of this kind of photocatalyst. 相似文献
27.
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
28.
Chueshova A. G. Pavlova L. A. Peshcherova S. M. Nepomnyashchikh A. I. 《Crystallography Reports》2021,66(7):1206-1215
Crystallography Reports - The orientation of grains and the special boundaries formed by them in multicrystalline silicon has been studied by electron backscattered diffraction. It is found that... 相似文献
29.
移动加热器法(THM)生长碲锌镉晶体时,界面稳定性对晶体生长的质量有很大影响。本文基于多物理场有限元仿真软件Comsol建立了THM生长碲锌镉晶体的数值模拟模型,讨论了Te边界层与组分过冷区之间的关系,对不同生长阶段的物理场、Te边界层与组分过冷区进行仿真研究,最后讨论了微重力对物理场分布的影响,并对比了微重力与正常重力下的生长界面形貌。模拟结果表明,Te边界层与组分过冷区的分布趋势是一致的,在不同生长阶段,流场中次生涡旋的位置会发生移动,从而导致生长界面的形貌随着生长的进行发生变化,同时微重力条件下形成的生长界面形貌最有利于单晶生长。因此,在晶体生长的中前期,对次生涡旋位置的控制和对组分过冷的削弱,是THM生长高质量晶体的有效方案。 相似文献
30.
Crystallography Reports - Methods of coherent X-ray diffraction imaging of the spatial structure of noncrystalline objects and nanocrystals (nanostructures) are considered. Particular attention is... 相似文献