全文获取类型
收费全文 | 1796篇 |
免费 | 18篇 |
国内免费 | 3篇 |
专业分类
化学 | 1167篇 |
晶体学 | 27篇 |
力学 | 52篇 |
数学 | 359篇 |
物理学 | 212篇 |
出版年
2024年 | 11篇 |
2023年 | 15篇 |
2022年 | 33篇 |
2021年 | 58篇 |
2020年 | 51篇 |
2019年 | 48篇 |
2018年 | 30篇 |
2017年 | 22篇 |
2016年 | 75篇 |
2015年 | 48篇 |
2014年 | 53篇 |
2013年 | 92篇 |
2012年 | 101篇 |
2011年 | 86篇 |
2010年 | 71篇 |
2009年 | 57篇 |
2008年 | 101篇 |
2007年 | 87篇 |
2006年 | 88篇 |
2005年 | 92篇 |
2004年 | 79篇 |
2003年 | 48篇 |
2002年 | 60篇 |
2001年 | 22篇 |
2000年 | 27篇 |
1999年 | 23篇 |
1998年 | 19篇 |
1997年 | 10篇 |
1996年 | 22篇 |
1995年 | 13篇 |
1994年 | 12篇 |
1993年 | 14篇 |
1992年 | 19篇 |
1991年 | 9篇 |
1990年 | 14篇 |
1989年 | 15篇 |
1988年 | 17篇 |
1987年 | 20篇 |
1986年 | 13篇 |
1985年 | 19篇 |
1984年 | 16篇 |
1983年 | 16篇 |
1982年 | 17篇 |
1981年 | 10篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1976年 | 3篇 |
1887年 | 2篇 |
排序方式: 共有1817条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Salvatore D'Aniello George H Fisher Enza Topo Gabriele Ferrandino Jordi Garcia-Fernàndez Antimo D'Aniello 《BMC neuroscience》2007,8(1):109
Background
NMDA (N-methyl-D-aspartic acid) is a widely known agonist for a class of glutamate receptors, the NMDA type. Synthetic NMDA elicits very strong activity for the induction of hypothalamic factors and hypophyseal hormones in mammals. Moreover, endogenous NMDA has been found in rat, where it has a role in the induction of GnRH (Gonadotropin Releasing Hormone) in the hypothalamus, and of LH (Luteinizing Hormone) and PRL (Prolactin) in the pituitary gland. 相似文献5.
6.
Pier?Paolo?ProsiniEmail author Maria?Carewska Gabriele?Tarquini Fabio?Maroni Agnese?Birrozzi Francesco?Nobili 《Ionics》2016,22(4):515-528
This paper describes the preparation and characterization of a high-voltage lithium-ion battery based on Sn-decorated reduced graphene oxide and LiNi0.5Mn1.5O4 as the anode and cathode active materials, respectively. The Sn-decorated reduced graphene oxide is prepared using a microwave-assisted hydrothermal synthesis method followed by reduction at high temperature of a mixture of (C6H5)2SnCl2 and graphene oxide. The so-obtained anode material is characterized by thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, and electron diffraction spectroscopy. The LiNi0.5Mn1.5O4 is a commercially available product. The two materials are used to prepare composite electrodes, and their electrochemical properties are investigated by galvanostatic charge/discharge cycles at various current densities in lithium cells. The electrodes are then used to assemble a high-voltage lithium-ion cell, and the cell is tested to evaluate its performance as a function of discharge rate and cycle number. 相似文献
7.
Gabriele Oliva Roberto Setola Stefano Panzieri 《The European physical journal. Special topics》2016,225(10):1929-1944
In this paper we develop a data-driven hierarchical clustering methodology to group the economic sectors of a country in order to highlight strongly coupled groups that are weakly coupled with other groups. Specifically, we consider an input-output representation of the coupling among the sectors and we interpret the relation among sectors as a directed graph; then we recursively apply the spectral clustering methodology over the graph, without a priori information on the number of groups that have to be obtained. In order to do this, we resort to the eigengap criterion, where a suitable number of groups is selected automatically based on the intensity and structure of the coupling among the sectors. We validate the proposed methodology considering a case study for Italy, inspecting how the coupling among clusters and sectors changes from the year 1995 to 2011, showing that in the years the Italian structure underwent deep changes, becoming more and more interdependent, i.e., a large part of the economy has become tightly coupled. 相似文献
8.
Jürgen Jung Michael Fricke Gabriele Hampel Jürgen Hesse 《Hyperfine Interactions》1992,68(1-4):275-278
Among the three possible phase structures (bcc, fcc and hep) of iron rich Fe100-cMn c alloys (c Mn <40 at%), the two closed packed structures, fcc and hep, produce poor resolved and similar Mössbauer spectra. Therefore the evaluation of spectra collected on a sample (nominalc Mn =35 at%) with coexisting fcc and hep phases only was possible with the help of the Afans’ev/Tsymbal method of “Mössbauer lines sharpening” introduced recently/1,2,3/. A comparison of the hyperfine field vs. temperature with an FeNi-Invar alloy (c Ni =35 at%) shows a surprising similarity. 相似文献
9.
Angela Giorgia Potortì Alessia Tropea Vito Pellizzeri Asma Belfita Giacomo Dugo 《Natural product research》2020,34(1):167-171
AbstractSpices and aromatic herbs can be contaminated with mycotoxins, since of their preharvest, postharvest, and storage conditions. In this study, 112 samples of different spices and aromatic herbs were evaluated for their mycotoxins content by HPLC-MS/MS in order to highlight their possible risk linked with human use. The results showed that mycotoxins were occasionally detected only in samples of coriander, laurel, mint, rosemary, and verbena. In both geographical origins a different contamination was detected. Among the investigated mycotoxins, AFB2, AFG1, AFG2, T2 and HT2 were detected, whereas none of the samples contained AFB1 and FB1. The co-occurrence of two toxins were observed for some samples of rosemary and verbena. This study indicates that it is essential minimize the toxins in agriculture, industry, and food-product manufacturing for the consumer health protection. 相似文献
10.