全文获取类型
收费全文 | 82085篇 |
免费 | 6770篇 |
国内免费 | 5193篇 |
专业分类
化学 | 23673篇 |
晶体学 | 1811篇 |
力学 | 3810篇 |
综合类 | 375篇 |
数学 | 20412篇 |
物理学 | 43967篇 |
出版年
2022年 | 183篇 |
2021年 | 385篇 |
2020年 | 692篇 |
2019年 | 998篇 |
2018年 | 949篇 |
2017年 | 666篇 |
2016年 | 533篇 |
2015年 | 451篇 |
2014年 | 1159篇 |
2013年 | 1921篇 |
2012年 | 1286篇 |
2011年 | 1879篇 |
2010年 | 2443篇 |
2009年 | 7011篇 |
2008年 | 8078篇 |
2007年 | 6566篇 |
2006年 | 5976篇 |
2005年 | 4109篇 |
2004年 | 3887篇 |
2003年 | 4142篇 |
2002年 | 4832篇 |
2001年 | 3774篇 |
2000年 | 3575篇 |
1999年 | 3397篇 |
1998年 | 2826篇 |
1997年 | 1987篇 |
1996年 | 1772篇 |
1995年 | 2240篇 |
1994年 | 2168篇 |
1993年 | 1625篇 |
1992年 | 1125篇 |
1991年 | 849篇 |
1990年 | 701篇 |
1989年 | 621篇 |
1988年 | 589篇 |
1987年 | 424篇 |
1986年 | 204篇 |
1985年 | 969篇 |
1984年 | 631篇 |
1983年 | 497篇 |
1982年 | 658篇 |
1981年 | 802篇 |
1980年 | 725篇 |
1979年 | 562篇 |
1978年 | 589篇 |
1977年 | 543篇 |
1976年 | 549篇 |
1975年 | 319篇 |
1974年 | 358篇 |
1973年 | 467篇 |
排序方式: 共有10000条查询结果,搜索用时 406 毫秒
61.
62.
63.
Johisner Penagos‐Llanos Olimpo García‐Beltrn J. A. Caldern Edgar Nagles J. J. Hurtado 《Electroanalysis》2019,31(4):695-703
The detection of Allura red (AR) by electrochemical reduction using a different electrode from the conventional mercury electrode is presented. A carbon paste with cobalt (II, III) oxide composite electrode (CoOx/CPE) is reported for the first time for the detection of AR. Moreover, others dyes such as tartrazine (TZ), sunset yellow (SY), amaranth (AM), Ponceaut 4‐R (P‐4R), and Sudan (SD) as well as pharmaceutical agents such as paracetamol (PMC) that are present in samples that contained AR did not show a reduced signal between 0.0 and ?0.3 V, which is the potential range where AR reduction was observed. The surface electroactivity was studied using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The presence of CoOX increased the cathodic peak current for AR by more than 50 % and 65 % via CV and square wave voltammetry (SWV), respectively, compared with an unmodified carbon paste electrode. Under the optimal parameters, (pH=3.0, accumulation time (tACC)=60 s and accumulation potential (EACC)=0.50 V), the detection limit for AR was 0.05 μmol L?1. The new sensor was sensitive and stable for the detection of AR. Moreover, it was easily manufactured and very convenient for food samples such as soft and isotonic drinks as well as chili sauce. 相似文献
64.
65.
66.
In 1994, I. Kan constructed a smooth map on the annulus admitting two physical measures, whose basins are intermingled. In this paper, we prove that Kan's map is robustly topologically mixing. 相似文献
67.
In this work we obtain positive singular solutions of where is a sufficiently small perturbation of the cone where has a smooth nonempty boundary and where satisfies suitable conditions. By singular solution we mean the solution is singular at the ‘vertex of the perturbed cone’. We also consider some other perturbations of the equation on the unperturbed cone Ω and here we use a different class of function spaces. 相似文献
68.
69.
Motivated by recent progress in dynamical sampling we prove that every frame which is norm-bounded below can be represented as a finite union of sequences for some bounded operators and elements in the underlying Hilbert space. The result is optimal, in the sense that it turns out to be problematic to replace the collection of generators by a singleton: indeed, for linearly independent frames we prove that we can represent the frame in terms of just one system , but unfortunately this representation often forces the operator T to be unbounded. Several examples illustrate the connection of the results to typical frames like Gabor frames and wavelet frames, as well as generic constructions in arbitrary separable Hilbert spaces. 相似文献
70.