全文获取类型
收费全文 | 1587篇 |
免费 | 42篇 |
国内免费 | 13篇 |
专业分类
化学 | 995篇 |
晶体学 | 2篇 |
力学 | 49篇 |
数学 | 347篇 |
物理学 | 249篇 |
出版年
2023年 | 10篇 |
2022年 | 29篇 |
2021年 | 37篇 |
2020年 | 28篇 |
2019年 | 25篇 |
2018年 | 28篇 |
2017年 | 18篇 |
2016年 | 58篇 |
2015年 | 32篇 |
2014年 | 36篇 |
2013年 | 84篇 |
2012年 | 74篇 |
2011年 | 127篇 |
2010年 | 63篇 |
2009年 | 57篇 |
2008年 | 97篇 |
2007年 | 96篇 |
2006年 | 86篇 |
2005年 | 57篇 |
2004年 | 52篇 |
2003年 | 44篇 |
2002年 | 34篇 |
2001年 | 16篇 |
2000年 | 25篇 |
1999年 | 17篇 |
1998年 | 16篇 |
1997年 | 19篇 |
1996年 | 22篇 |
1995年 | 16篇 |
1994年 | 27篇 |
1993年 | 25篇 |
1992年 | 14篇 |
1991年 | 8篇 |
1990年 | 11篇 |
1987年 | 6篇 |
1986年 | 9篇 |
1985年 | 18篇 |
1984年 | 8篇 |
1983年 | 12篇 |
1982年 | 14篇 |
1981年 | 17篇 |
1980年 | 13篇 |
1979年 | 15篇 |
1978年 | 8篇 |
1977年 | 6篇 |
1976年 | 8篇 |
1975年 | 6篇 |
1974年 | 8篇 |
1973年 | 8篇 |
1858年 | 7篇 |
排序方式: 共有1642条查询结果,搜索用时 0 毫秒
51.
52.
53.
Enrico Dalcanale Giancarlo Antonioli Mauro Ricco Herbert Groothues Friedrich Kremer 《Liquid crystals》2013,40(9):1161-1169
The dynamic and conformational behaviour of four mesogenic resorcinarenes exhibiting columnar mesophases have been studied by a combination of broadband dielectric spectroscopy and deuterium solid state NMR. Broadband dielectric spectroscopy provided evidence for two relaxation processes present both in the mesophase and in the isotropic liquid. The high frequency process II, common to all mesogens, has been assigned to the libration of the carbonyl groups of the ester junctions between the core and the side chains. The low frequency process I, present in conformationally mobile mesogens 1 and 2, has been attributed to the ring inversion process of the macrocyclic core associated with dipole inversion along the columnar axis. Deuterium solid state NMR performed on 4, the deuteriated analogue of 1, confirmed the molecular dynamics attribution for process I, assigning the ring inversion to the interconversion of the two equivalent crown conformations. 相似文献
54.
Enrico Luchinat Letizia Barbieri Matteo Cremonini Alessio Nocentini Claudiu T. Supuran Lucia Banci 《Angewandte Chemie (International ed. in English)》2020,59(16):6535-6539
Structure‐based drug development is often hampered by the lack of in vivo activity of promising compounds screened in vitro, due to low membrane permeability or poor intracellular binding selectivity. Herein, we show that ligand screening can be performed in living human cells by “intracellular protein‐observed” NMR spectroscopy, without requiring enzymatic activity measurements or other cellular assays. Quantitative binding information is obtained by fast, inexpensive 1H NMR experiments, providing intracellular dose‐ and time‐dependent ligand binding curves, from which kinetic and thermodynamic parameters linked to cell permeability and binding affinity and selectivity are obtained. The approach was applied to carbonic anhydrase and, in principle, can be extended to any NMR‐observable intracellular target. The results obtained are directly related to the potency of candidate drugs, that is, the required dose. The application of this approach at an early stage of the drug design pipeline could greatly increase the low success rate of modern drug development. 相似文献
55.
56.
A conversion - temperature - transformation (CTT) diagram was used to analyze several non-isothermal processes of polymer network formation: a) range of heating rates where reliable kinetic information can be obtained; b) a novel process involving part of the cure in the glassy state; c) phase separation in rubber-modified epoxies cured in heated molds. 相似文献
57.
Aurelio Liguori Enrico Armentani Alcide Bertocco Andrea Formato Arcangelo Pellegrino Francesco Villecco 《Entropy (Basel, Switzerland)》2020,22(11)
This article lists some tips for reducing gear case noise. With this aim, a static analysis was carried out in order to describe how stresses resulting from meshing gears affect the acoustic emissions. Different parameters were taken into account, such as the friction, material, and lubrication, in order to validate ideas from the literature and to make several comparisons. Furthermore, a coupled Eulerian–Lagrangian (CEL) analysis was performed, which was an innovative way of evaluating the sound pressure level of the aforementioned gears. Different parameters were considered again, such as the friction, lubrication, material, and rotational speed, in order to make different research comparisons. The analytical results agreed with those in the literature, both for the static analysis and CEL analysis—for example, it was shown that changing the material from steel to ductile iron improved the gear noise, while increasing the rotational speed or the friction increased the acoustic emissions. Regarding the CEL analysis, air was considered a perfect gas, but its viscosity or another state equation could have also been taken into account. Therefore, the above allowed us to state that research into these scientific fields will bring about reliable results. 相似文献
58.
59.
60.