全文获取类型
收费全文 | 13247篇 |
免费 | 2477篇 |
国内免费 | 1341篇 |
专业分类
化学 | 8993篇 |
晶体学 | 126篇 |
力学 | 992篇 |
综合类 | 126篇 |
数学 | 1705篇 |
物理学 | 5123篇 |
出版年
2024年 | 24篇 |
2023年 | 269篇 |
2022年 | 301篇 |
2021年 | 466篇 |
2020年 | 548篇 |
2019年 | 510篇 |
2018年 | 463篇 |
2017年 | 415篇 |
2016年 | 659篇 |
2015年 | 645篇 |
2014年 | 738篇 |
2013年 | 1002篇 |
2012年 | 1142篇 |
2011年 | 1214篇 |
2010年 | 846篇 |
2009年 | 756篇 |
2008年 | 897篇 |
2007年 | 745篇 |
2006年 | 736篇 |
2005年 | 566篇 |
2004年 | 451篇 |
2003年 | 381篇 |
2002年 | 367篇 |
2001年 | 314篇 |
2000年 | 287篇 |
1999年 | 319篇 |
1998年 | 254篇 |
1997年 | 268篇 |
1996年 | 243篇 |
1995年 | 205篇 |
1994年 | 173篇 |
1993年 | 164篇 |
1992年 | 119篇 |
1991年 | 96篇 |
1990年 | 94篇 |
1989年 | 72篇 |
1988年 | 53篇 |
1987年 | 40篇 |
1986年 | 49篇 |
1985年 | 32篇 |
1984年 | 25篇 |
1983年 | 19篇 |
1982年 | 18篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1975年 | 5篇 |
1957年 | 5篇 |
1913年 | 4篇 |
1909年 | 4篇 |
1908年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Tian Jie Yang Weifeng Chen Min Zheng Minfang Chen Ding Qiu Yusheng 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(2):1039-1049
Journal of Radioanalytical and Nuclear Chemistry - This study presents a time-efficient method of analysing 210Pb, 210Bi, and 210Po in natural waters. The optimum pH (1.00), temperature... 相似文献
2.
Yujie Xiong 《中国科学:化学(英文版)》2022,65(1):5-6
Photoelectrochemical(PEC)technique represents a promising approach to chemical transformation by harvesting sustainable solar energy.Despite the wide applications of PEC systems such as environmental remediation and solar energy conversion,the reported PEC reactions are dominated by the radical-based processes that are initiated by the single electron transfer between photo-induced carriers and adsorbed species on photoelectrode surface[1,2].For instance,hydroxyl radicals are often involved in the PEC oxidation reactions.As well known,it is a grand challenge to control the formation and evolution rates of radicals,which inevitably leads to the unsatisfactory product selectivity of PEC reactions.Naturally,such a circumstance brings about a question to the research community whether a different mechanism can be established to sustain efficient and selective oxygenation.Recently,based on their previous findings on PEC water oxidation[3,4],Zhao and coworkers[5]reported that many substrates can be oxidized in an oxygen atom transfer(OAT)pathway,a non-radical two electron process,to oxygenated products byα-Fe2O3 photoanodes. 相似文献
3.
A (di)graph is supereulerian if it contains a spanning eulerian sub(di)graph. This property is a relaxation of hamiltonicity. Inspired by this analogy with hamiltonian cycles and by similar results in supereulerian graph theory, we analyze a number of sufficient Ore type conditions for a digraph to be supereulerian. Furthermore, we study the following conjecture due to Thomassé and the first author: if the arc‐connectivity of a digraph is not smaller than its independence number, then the digraph is supereulerian. As a support for this conjecture we prove it for digraphs that are semicomplete multipartite or quasitransitive and verify the analogous statement for undirected graphs. 相似文献
4.
5.
CongZhan Liu YiFei Zhang XuFang Li XueFeng Lu Zhi Chang ZhengWei Li AiMei Zhang YongJie Jin HuiMing Yu Zhao Zhang MinXue Fu YiBao Chen JianFeng Ji YuPeng Xu JingKang Deng RenCheng Shang GuoQing Liu FangJun Lu ShuangNan Zhang YongWei Dong TiPei Li Mei Wu YanGuo Li HuanYu Wang BoBing Wu YongJie Zhang Zhi Zhang ShaoLin Xiong Yuan Liu Shu Zhang HongWei Liu YiJung Yang Fan Zhang 《中国科学:物理学 力学 天文学(英文版)》2020,(4):20-34
The Insight-Hard X-ray Modulation Telescope(Insight-HXMT) is a broadband X-ray and γ-ray(1-3000 ke V) astronomy satellite. One of its three main telescopes is the High Energy X-ray telescope(HE). The main detector plane of HE comprises 18 Na I(Tl)/Cs I(Na) phoswich detectors, where Na I(Tl) is used as the primary detector to measure ~ 20-250 ke V photons incident from the field of view(FOV) defined by collimators, and Cs I(Na) is used as the active shielding detector to Na I(Tl) by pulse shape discrimination. Additionally, Cs I(Na) is used as an omnidirectional γ-ray monitor. The HE collimators have a diverse FOV,i.e. 1.1°×5.7°(15 units), 5.7°×5.7°(2 units), and blocked(1 unit). Therefore, the combined FOV of HE is approximately5.7°×5.7°. Each HE detector has a diameter of 190 mm resulting in a total geometrical area of approximately 5100 cm2, and the energy resolution is ~15% at 60 ke V. For each recorded X-ray event by HE, the timing accuracy is less than 10 μs and the deadtime is less than 10 μs. HE is used for observing spectra and temporal variability of X-ray sources in the 20-250 ke V band either by pointing observations for known sources or scanning observations to unveil new sources. Additionally, HE is used for monitoring the γ-ray burst in 0.2-3 Me V band. This paper not only presents the design and performance of HE instruments but also reports results of the on-ground calibration experiments. 相似文献
6.
Yin Pengpeng Liu Chang Wang Ying Guan Lei Chen Xian Xiong Xuejia Jin Hongzhe 《Russian Journal of General Chemistry》2021,91(5):897-903
Russian Journal of General Chemistry - A dinuclear Tb complex, Tb2(H2L)3(phen)2 (1), and two similar N-donor coordination complexes, Fe(phen)3·HL (2), Fe(bipy)3·HL·5H2O (3) (Na2H2L =... 相似文献
7.
Peng-Yan Gui Xiao-Hui Yan Wen-Juan Yuan Yuan-Liang Ma Xiao Ding Shuai Liu 《Natural product research》2019,33(19):2830-2836
A new A, D-seco limonoid, named 12-acetyloxyperforatin (1), along with three known ones, were isolated from the leaves of Harrisonia perforata. Their structures were elucidated on the basis of spectroscopic analysis, including extensive NMR techniques and computational modelling. These compounds showed no inhibitory activity against the 11β-HSD1 enzyme. 相似文献
8.
Nonlinear Dynamics - Conventional tuned liquid column dampers (TLCDs) are deficient in multidirectionality. In contrast, toroidal TLCDs are designed to extend the application to multidirectional... 相似文献
9.
Science China Chemistry - 相似文献
10.
Ding Q. Yao M. Wu Sh. Zeng M. Xue N. Wu D. Xu J. 《Journal of Applied Spectroscopy》2022,89(4):712-718
Journal of Applied Spectroscopy - Based on partial least squares (PLS) analysis, the effects of different smoothing points and different preprocessing methods on the accuracy and precision of the... 相似文献