全文获取类型
收费全文 | 2554篇 |
免费 | 45篇 |
国内免费 | 12篇 |
专业分类
化学 | 1526篇 |
晶体学 | 23篇 |
力学 | 124篇 |
数学 | 430篇 |
物理学 | 508篇 |
出版年
2023年 | 16篇 |
2022年 | 16篇 |
2021年 | 61篇 |
2020年 | 34篇 |
2019年 | 45篇 |
2018年 | 41篇 |
2017年 | 29篇 |
2016年 | 71篇 |
2015年 | 47篇 |
2014年 | 74篇 |
2013年 | 154篇 |
2012年 | 125篇 |
2011年 | 156篇 |
2010年 | 100篇 |
2009年 | 88篇 |
2008年 | 139篇 |
2007年 | 146篇 |
2006年 | 146篇 |
2005年 | 131篇 |
2004年 | 121篇 |
2003年 | 81篇 |
2002年 | 80篇 |
2001年 | 39篇 |
2000年 | 33篇 |
1999年 | 25篇 |
1998年 | 21篇 |
1997年 | 28篇 |
1996年 | 41篇 |
1995年 | 30篇 |
1994年 | 31篇 |
1993年 | 29篇 |
1992年 | 18篇 |
1991年 | 21篇 |
1990年 | 23篇 |
1989年 | 29篇 |
1988年 | 23篇 |
1987年 | 25篇 |
1986年 | 19篇 |
1985年 | 23篇 |
1984年 | 29篇 |
1983年 | 27篇 |
1982年 | 21篇 |
1981年 | 20篇 |
1980年 | 19篇 |
1979年 | 17篇 |
1978年 | 20篇 |
1977年 | 16篇 |
1976年 | 10篇 |
1975年 | 11篇 |
1973年 | 9篇 |
排序方式: 共有2611条查询结果,搜索用时 187 毫秒
1.
Milasi Monica Scopelliti Domenico 《Journal of Optimization Theory and Applications》2021,190(3):879-893
Journal of Optimization Theory and Applications - We introduce a variational approach to study a maximization problem of preferences that cannot be represented by a utility function. In such... 相似文献
2.
A Stable Porphyrin Functionalized Graphite Electrode Used at the Oxygen Evolution Reaction Potential
Gianlorenzo Bussetti Roberto Bernasconi Claudia Filoni Luca Magagnin Alberto Bossi Franco Ciccacci Lamberto Duò 《Electroanalysis》2022,34(7):1227-1236
Many researches have been devoted to rechargeable power generators that can store (but also release) energy. This availability is ensured through (e. g.) the oxygen evolution reaction (OER). However, (i) large values of the overpotentials and (ii) a progressive detriment of the anode (graphite) electrode limit the ultimate device. In view of enhancing the electrode performances, graphite was protected by following different strategies, which oblige to follow precise preparation protocols. Here, we prove that a thin layer of free-base porphyrin molecules is able to protect the underneath graphite electrode from detriment even if many (about 100) electrochemical cycles are performed. 相似文献
3.
QiuHong Wang Abdusalam Abdukerim Wei Chen Xun Chen YunHua Chen XiangYi Cui YingJie Fan DeQing Fang ChangBo Fu LiSheng Geng Karl Giboni Franco Giuliani LinHui Gu XuYuan Guo Ke Han ChangDa He Di Huang Yan Huang YanLin Huang Zhou Huang Peng Ji XiangDong Ji YongLin Ju YiHui Lai Kun Liang HuaXuan Liu JiangLai Liu WenBo Ma YuGang Ma YaJun Mao Yue Meng Parinya Namwongsa KaiXiang Ni JinHua Ning XuYang Ning XiangXiang Ren ChangSong Shang Lin Si AnDi Tan AnQing Wang HongWei Wang Meng Wang SiGuang Wang XiuLi Wang Zhou Wang MengMeng Wu ShiYong Wu JingKai Xia MengJiao Xiao PengWei Xie BinBin Yan JiJun Yang Yong Yang ChunXu Yu Jumin Yuan Dan Zhang HongGuang Zhang Tao Zhang Li Zhao QiBin Zheng JiFang Zhou Ning Zhou XiaoPeng Zhou 《中国科学:物理学 力学 天文学(英文版)》2020,(3):54-63
In dark matter direct detection experiments,neutron is a serious source of background,which can mimic the dark matter-nucleus scattering signals.In this paper,we present an improved evaluation of the neutron background in the PandaX-II dark matter experiment by a novel approach.Instead of fully relying on the Monte Carlo simulation,the overall neutron background is determined from the neutron-induced high energy signals in the data.In addition,the probability of producing a dark-matter-like background per neutron is evaluated with a complete Monte Carlo generator,where the correlated emission of neutron(s)andγ(s)in the(α,n)reactions and spontaneous fissions is taken into consideration.With this method,the neutron backgrounds in the Run 9(26-ton-day)and Run 10(28-ton-day)data sets of PandaX-II are estimated to be(0.66±0.24)and(0.47±0.25)events,respectively. 相似文献
4.
Pedro Henrique Cavalcanti Franco Saulo Fehelberg Pinto Braga Renata Barbosa de Oliveira Isabela Costa César 《Magnetic resonance in chemistry : MRC》2020,58(1):97-105
Quantitative nuclear magnetic resonance (qNMR) is an analytical technique that offers numerous advantages in pharmaceutical applications including minimum sample preparation and rapid data collection times with no need for response factor corrections, being a powerful tool for assaying drug content in both drug discovery and early drug development. In the present work, we have applied qNMR, using both the internal standard and the electronic reference to access in vivo concentrations 2 calibration methods, to assess the purity of RI76, a novel antifungal drug candidate. NMR acquisition and processing parameters were optimized in order to obtain spectra with intense, well-resolved signals of completely relaxed nuclei. The analytical method was validated following current guidelines, demonstrating selectivity, linearity, accuracy, precision, and robustness. The calibration approaches were statistically compared, and no significant difference was observed when comparing the obtained results and their dispersion in terms of relative standard deviation. The proposed qNMR method may, therefore, be used for both qualitative and quantitative assessments of RI76 in early drug development and for characterization of this compound. 相似文献
5.
AbstractRealistic stochastic modeling is increasingly requiring the use of bounded noises. In this work, properties and relationships of commonly employed bounded stochastic processes are investigated within a solid mathematical ground. Four families are object of investigation: the Sine-Wiener (SW), the Doering–Cai–Lin (DCL), the Tsallis–Stariolo–Borland (TSB), and the Kessler–Sørensen (KS) families. We address mathematical questions on existence and uniqueness of the processes defined through Stochastic Differential Equations, which often conceal non-obvious behavior, and we explore the behavior of the solutions near the boundaries of the state space. The expression of the time-dependent probability density of the Sine-Wiener noise is provided in closed form, and a close connection with the Doering–Cai–Lin noise is shown. Further relationships among the different families are explored, pathwise and in distribution. Finally, we illustrate an analogy between the Kessler–Sørensen family and Bessel processes, which allows to relate the respective local times at the boundaries. 相似文献
6.
7.
Domenico Franco Giovanna Calabrese Salvatore Petralia Giulia Neri Carmelo Corsaro Lucia Forte Stefano Squarzoni Salvatore Guglielmino Francesco Traina Enza Fazio Sabrina Conoci 《Molecules (Basel, Switzerland)》2021,26(4)
Hydroxyapatite (HA) is the main inorganic mineral that constitutes bone matrix and represents the most used biomaterial for bone regeneration. Over the years, it has been demonstrated that HA exhibits good biocompatibility, osteoconductivity, and osteoinductivity both in vitro and in vivo, and can be prepared by synthetic and natural sources via easy fabrication strategies. However, its low antibacterial property and its fragile nature restricts its usage for bone graft applications. In this study we functionalized a MgHA scaffold with gold nanorods (AuNRs) and evaluated its antibacterial effect against S. aureus and E. coli in both suspension and adhesion and its cytotoxicity over time (1 to 24 days). Results show that the AuNRs nano-functionalization improves the antibacterial activity with 100% bacterial reduction after 24 h. The toxicity study, however, indicates a 4.38-fold cell number decrease at 24 days. Although further optimization on nano-functionalization process are needed for cytotoxicity, these data indicated that Au-NRs nano-functionalization is a very promising method for improving the antibacterial properties of HA. 相似文献
8.
Scaramozzino Domenico Lacidogna Giuseppe Piana Gianfranco Carpinteri Alberto 《Meccanica》2019,54(13):1927-1940
Meccanica - Protein mechanical vibrations play a pivotal role in biological activity. In particular, low-frequency (terahertz) modes are related to protein conformational changes, which represent... 相似文献
9.
Marién Abreu Jan Goedgebeur Domenico Labbate Giuseppe Mazzuoccolo 《Journal of Graph Theory》2019,92(4):415-444
A -bisection of a bridgeless cubic graph is a -colouring of its vertex set such that the colour classes have the same cardinality and all connected components in the two subgraphs induced by the colour classes ( monochromatic components in what follows) have order at most . Ban and Linial Conjectured that every bridgeless cubic graph admits a -bisection except for the Petersen graph. A similar problem for the edge set of cubic graphs has been studied: Wormald conjectured that every cubic graph with has a -edge colouring such that the two monochromatic subgraphs are isomorphic linear forests (ie, a forest whose components are paths). Finally, Ando conjectured that every cubic graph admits a bisection such that the two induced monochromatic subgraphs are isomorphic. In this paper, we provide evidence of a strong relation of the conjectures of Ban-Linial and Wormald with Ando's Conjecture. Furthermore, we also give computational and theoretical evidence in their support. As a result, we pose some open problems stronger than the above-mentioned conjectures. Moreover, we prove Ban-Linial's Conjecture for cubic-cycle permutation graphs. As a by-product of studying -edge colourings of cubic graphs having linear forests as monochromatic components, we also give a negative answer to a problem posed by Jackson and Wormald about certain decompositions of cubic graphs into linear forests. 相似文献
10.