全文获取类型
收费全文 | 119968篇 |
免费 | 682篇 |
国内免费 | 478篇 |
专业分类
化学 | 42571篇 |
晶体学 | 1841篇 |
力学 | 8351篇 |
综合类 | 23篇 |
数学 | 26969篇 |
物理学 | 41373篇 |
出版年
2023年 | 97篇 |
2022年 | 160篇 |
2021年 | 165篇 |
2020年 | 193篇 |
2019年 | 221篇 |
2018年 | 9936篇 |
2017年 | 10866篇 |
2016年 | 4764篇 |
2015年 | 1217篇 |
2014年 | 526篇 |
2013年 | 720篇 |
2012年 | 5503篇 |
2011年 | 14591篇 |
2010年 | 8566篇 |
2009年 | 8672篇 |
2008年 | 12423篇 |
2007年 | 16230篇 |
2006年 | 875篇 |
2005年 | 8095篇 |
2004年 | 4280篇 |
2003年 | 4152篇 |
2002年 | 1910篇 |
2001年 | 695篇 |
2000年 | 759篇 |
1999年 | 344篇 |
1998年 | 282篇 |
1997年 | 209篇 |
1996年 | 393篇 |
1995年 | 278篇 |
1994年 | 251篇 |
1993年 | 203篇 |
1992年 | 190篇 |
1991年 | 199篇 |
1990年 | 183篇 |
1989年 | 169篇 |
1988年 | 158篇 |
1987年 | 139篇 |
1986年 | 127篇 |
1985年 | 143篇 |
1984年 | 156篇 |
1983年 | 125篇 |
1982年 | 129篇 |
1981年 | 131篇 |
1980年 | 122篇 |
1979年 | 136篇 |
1978年 | 149篇 |
1976年 | 89篇 |
1973年 | 109篇 |
1969年 | 81篇 |
1968年 | 108篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
Mathematical Programming - In the general equilibrium with incomplete asset markets (GEI) model, the excess demand functions are typically not continuous at the prices for which the assets have... 相似文献
3.
Atopic dermatitis is characterized by leukocyte migration into the skin dermis and typically driven by excessive chemokine production at the site of inflammation. Conventional topical formulations such as gels, creams, and ointments are insufficient for this treatment because of low penetration of drug molecules into the targeted skin tissues. Herein, using a simple, green, sustainable strategy, we have developed novel primary zein nanoparticles embedded in curcumin (Cur) and coated with silk sericin (ZHSCs) for the topical delivery of Cur to penetrate into the dermis and exercise anti-dermatitis effects on the lesion with minimal side-effects. Transdermal delivery experiments and porcine skin fluorescence imaging indicated that ZHSCs facilitate the penetration of Cur across the epidermis layer of skin to reach deep-seated sites. Notably, ZHSCs = 1:0.25 (zein-to-silk sericin mass ratios of 1:0.25) markedly elevated the skin permeability and cumulative turnover of Cur transferred, which were provided a greater than a 3.8-fold increase relative to free Cur. The special nanoparticles of ZHS = 1:0.25 possessed the deepest localization depth and experience a transition of the particle structure and core-shell separation after penetrating into the dermis of skin. In a cell model of dermatitis induced by tumor necrosis factor α/interferon γ co-stimulation, compared with free Cur, Cur-loaded ZHS nanoparticles down-regulated the generation of inflammatory cytokines and chemokines in keratinocytes through suppression of the nuclear translocation of NF-κBp65 and hence exerted an anti-dermatitis effect. This strategy may provide new avenues and direction for the demanding issues of valid topical delivery systems. 相似文献
4.
For an integer , a graph is -hamiltonian if for any vertex subset with , is hamiltonian, and is -hamiltonian connected if for any vertex subset with , is hamiltonian connected. Thomassen in 1984 conjectured that every 4-connected line graph is hamiltonian (see Thomassen, 1986), and Ku?zel and Xiong in 2004 conjectured that every 4-connected line graph is hamiltonian connected (see Ryjá?ek and Vrána, 2011). In Broersma and Veldman (1987), Broersma and Veldman raised the characterization problem of -hamiltonian line graphs. In Lai and Shao (2013), it is conjectured that for , a line graph is -hamiltonian if and only if is -connected. In this paper we prove the following.(i) For an integer , the line graph of a claw-free graph is -hamiltonian if and only if is -connected.(ii) The line graph of a claw-free graph is 1-hamiltonian connected if and only if is 4-connected. 相似文献
5.
K. E. Prikhodko M. M. Dementyeva B. A. Gurovich D. A. Komarov L. V. Kutuzov 《Crystallography Reports》2018,63(2):241-244
The change in the free-electron density in ultrathin (5 nm) superconducting NbN films in the initial state and after irradiation by O+ ions to doses of (0.1–0.9) × 1017 cm–2 has been studied by electron energy-loss spectroscopy (EELS). The analysis has been performed on cross section samples prepared by the focused ion beam method, using plasmon oscillations with energies up to 50 eV. The radiation-induced replacement of nitrogen atoms with oxygen atoms in niobium nitride is found to change the electrical properties of the material, which leads to a decrease in the free-electron density with an increase in the irradiation dose. 相似文献
6.
7.
8.
9.
10.
We summarize the results of our recent work on Bäcklund transformations (BTs), particularly focusing on the relation between BTs and infinitesimal symmetries. We present a BT for an associated Degasperis–Procesi (aDP) equation and its superposition principle and investigate the solutions generated by applying this BT. Following our general methodology, we use the superposition principle of the BT to generate the infinitesimal symmetries of the aDP equation. 相似文献