全文获取类型
收费全文 | 9306篇 |
免费 | 322篇 |
国内免费 | 27篇 |
专业分类
化学 | 6287篇 |
晶体学 | 69篇 |
力学 | 288篇 |
综合类 | 1篇 |
数学 | 1244篇 |
物理学 | 1766篇 |
出版年
2023年 | 75篇 |
2022年 | 65篇 |
2021年 | 267篇 |
2020年 | 201篇 |
2019年 | 201篇 |
2018年 | 198篇 |
2017年 | 176篇 |
2016年 | 383篇 |
2015年 | 321篇 |
2014年 | 328篇 |
2013年 | 587篇 |
2012年 | 689篇 |
2011年 | 704篇 |
2010年 | 500篇 |
2009年 | 447篇 |
2008年 | 625篇 |
2007年 | 576篇 |
2006年 | 472篇 |
2005年 | 422篇 |
2004年 | 338篇 |
2003年 | 309篇 |
2002年 | 220篇 |
2001年 | 170篇 |
2000年 | 137篇 |
1999年 | 87篇 |
1998年 | 85篇 |
1997年 | 68篇 |
1996年 | 79篇 |
1995年 | 68篇 |
1994年 | 65篇 |
1993年 | 60篇 |
1992年 | 67篇 |
1991年 | 59篇 |
1990年 | 47篇 |
1989年 | 35篇 |
1988年 | 39篇 |
1987年 | 32篇 |
1986年 | 31篇 |
1985年 | 60篇 |
1984年 | 45篇 |
1983年 | 27篇 |
1982年 | 26篇 |
1981年 | 24篇 |
1980年 | 39篇 |
1979年 | 21篇 |
1978年 | 27篇 |
1976年 | 23篇 |
1975年 | 19篇 |
1974年 | 15篇 |
1973年 | 20篇 |
排序方式: 共有9655条查询结果,搜索用时 109 毫秒
1.
2.
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
3.
4.
5.
Annals of Operations Research - The vehicle routing problem is a traditional combinatorial problem with practical relevance for a wide range of industries. In the literature, several specificities... 相似文献
6.
Fernandes Joo Lucas Ribeiro e de Souza Altair Lcio de Faria Geraldo Lcio 《Journal of Thermal Analysis and Calorimetry》2022,147(12):6593-6603
Journal of Thermal Analysis and Calorimetry - The hot coil slump is a recurrent problem in the manufacturing process of medium and high equivalent carbon steel plates. Even with the success of the... 相似文献
7.
Majchrzak-Kucęba Izabela Ściubidło Aleksandra 《Journal of Thermal Analysis and Calorimetry》2019,138(6):4139-4144
Journal of Thermal Analysis and Calorimetry - The paper presents the effect of the tabletting pressure and time on the chemical structure and crystallinity of the CuBTC and MIL-53(Al)... 相似文献
8.
9.
Vanessa R. Machado Louis P. Sandjo Giovanni L. Pinheiro Milene H. Moraes Mario Steindel Moacir G. Pizzolatti 《Natural product research》2018,32(3):275-281
The natural product lupeol 1 was isolated from aerial parts of Vernonia scorpioides with satisfactory yield, which made it viable to be used as starting material in semisynthetic approach. Ten lupeol derivatives 2–11 were prepared by classical procedures. Including, five new esters derivatives 7–11, which were obtained by structural modifications in the isopropylidene fragment. All semisynthetic compounds and lupeol 1–11 were confirmed by 1H NMR, 13C NMR and HRMS. Their antiprotozoal activity was evaluated in vitro against L. amazonensis and T. cruzi. Derivative 6 showed the best antitrypanosomal activity (IC50 = 12.48 μg/mL) and the lowest cytotoxic derivative (CC50 = 161.50 μg/mL). The mechanism of action of the most active derivatives (4, 6 and 11) is not dependent from the enzyme trypanothione reductase. 相似文献
10.
Marianna V. Rodrigues Fbio S. Zanuzzo Joo Fernando A. Koch Carlos Alberto F. de Oliveira Petr Sima Vaclav Vetvicka 《Molecules (Basel, Switzerland)》2020,25(22)
Administration of β-glucans through various routes, including immersion, dietary inclusion, or injection, have been found to stimulate various facets of immune responses, such as resistance to infections and resistance to environmental stress. β-Glucans used as an immunomodulatory food supplement have been found beneficial in eliciting immunity in commercial aquaculture. Despite extensive research involving more than 3000 published studies, knowledge of the receptors involved in recognition of β-glucans, their downstream signaling, and overall mechanisms of action is still lacking. The aim of this review is to summarize and discuss what is currently known about of the use of β-glucans in fish. 相似文献