全文获取类型
收费全文 | 4698篇 |
免费 | 104篇 |
国内免费 | 19篇 |
专业分类
化学 | 2925篇 |
晶体学 | 38篇 |
力学 | 101篇 |
数学 | 809篇 |
物理学 | 948篇 |
出版年
2022年 | 35篇 |
2021年 | 96篇 |
2020年 | 82篇 |
2019年 | 71篇 |
2018年 | 71篇 |
2017年 | 66篇 |
2016年 | 125篇 |
2015年 | 108篇 |
2014年 | 135篇 |
2013年 | 266篇 |
2012年 | 252篇 |
2011年 | 301篇 |
2010年 | 174篇 |
2009年 | 190篇 |
2008年 | 269篇 |
2007年 | 245篇 |
2006年 | 217篇 |
2005年 | 185篇 |
2004年 | 184篇 |
2003年 | 143篇 |
2002年 | 96篇 |
2001年 | 72篇 |
2000年 | 60篇 |
1999年 | 36篇 |
1998年 | 41篇 |
1997年 | 39篇 |
1996年 | 59篇 |
1995年 | 52篇 |
1994年 | 38篇 |
1993年 | 36篇 |
1992年 | 44篇 |
1991年 | 30篇 |
1989年 | 26篇 |
1988年 | 24篇 |
1987年 | 22篇 |
1986年 | 30篇 |
1985年 | 43篇 |
1984年 | 40篇 |
1983年 | 27篇 |
1982年 | 42篇 |
1981年 | 41篇 |
1980年 | 47篇 |
1979年 | 41篇 |
1978年 | 38篇 |
1977年 | 43篇 |
1976年 | 55篇 |
1975年 | 43篇 |
1974年 | 38篇 |
1973年 | 27篇 |
1971年 | 21篇 |
排序方式: 共有4821条查询结果,搜索用时 31 毫秒
1.
da Silva Andre Luis Ferreira Salas Ruben Andres Silva Emilio Carlos Nelli 《Meccanica》2021,56(2):417-437
Meccanica - Fiber reinforced materials are used in assorted engineering application and for this reason, new additive manufacturing technologies have been developed for this type of materials. With... 相似文献
2.
3.
Dmytro Strilets Dr. Shixin Fa Arthur Hardiagon Dr. Marc Baaden Prof. Tomoki Ogoshi Dr. Mihail Barboiu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(51):23413-23419
Artificial water channels mimicking natural aquaporins (AQPs) can be used for selective and fast transport of water. Here, we quantify the transport performances of peralkyl-carboxylate-pillar[5]arenes dimers in bilayer membranes. They can transport ≈107 water molecules/channel/second, within one order of magnitude of the transport rates of AQPs, rejecting Na+ and K+ cations. The dimers have a tubular structure, superposing pillar[5]arene pores of 5 Å diameter with twisted carboxy-phenyl pores of 2.8 Å diameter. This biomimetic platform, with variable pore dimensions within the same structure, offers size restriction reminiscent of natural proteins. It allows water molecules to selectively transit and prevents bigger hydrated cations from passing through the 2.8 Å pore. Molecular simulations prove that dimeric or multimeric honeycomb aggregates are stable in the membrane and form water pathways through the bilayer. Over time, a significant shift of the upper vs. lower layer occurs initiating new unexpected water permeation events through toroidal pores. 相似文献
4.
5.
Ana Carolina de C. Correia Tamyris F. Ferreira Italo Rossi R. Martins Cibério L. Macêdo Fabio de S. Monteiro Vicente Carlos O. Costa 《Natural product research》2015,29(10):980-984
Xylopia langsdorfiana A. St.-Hil. &Tul. (Annonaceae) is popularly known in the northeast of Brazil as ‘pimenteira da terra’, and an essential oil (XL-OE) was extracted from its leaves. Since Xylopia species are cited in folk medicine and diterpenes from X. langsdorfiana have spasmolytic activity, this study aimed to investigate a possible spasmolytic action of XL-OE on smooth muscle models. XL-OE (243 and 729 μg/mL) showed low pharmacologic efficacy on guinea pig trachea and rat aorta and uterus. However, in guinea pig ileum, XL-OE (27–729 μg/mL) inhibited carbachol or histamine-induced phasic contractions (1 μM) in a significant and concentration-dependent manner. In addition, XL-OE (81 μg/mL) reduced fluorescence intensity in ileal myocytes stimulated by histamine, indicating a decrease in cytosolic calcium concentration, which could explain the spasmolytic activity. Thus, XL-OE proved to be a promising natural product to be used in gastrointestinal diseases acting by modulating the cytosolic calcium concentration. 相似文献
6.
The influence of different referencing methods on the accuracy of δ13C value measurement of ethanol fuel by gas chromatography/combustion/isotope ratio mass spectrometry 下载免费PDF全文
7.
8.
9.
10.
Ferreira Willian Hermogenes Andrade Cristina Tristão 《Journal of Thermal Analysis and Calorimetry》2021,143(4):3107-3115
Journal of Thermal Analysis and Calorimetry - In this work, the effect of reduced graphene oxide (rGO) on the thermally induced shape memory properties of poly(lactic acid) (PLA) was studied. rGO... 相似文献