全文获取类型
收费全文 | 176136篇 |
免费 | 580篇 |
国内免费 | 442篇 |
专业分类
化学 | 57581篇 |
晶体学 | 2221篇 |
力学 | 13152篇 |
综合类 | 1篇 |
数学 | 53016篇 |
物理学 | 51187篇 |
出版年
2022年 | 107篇 |
2021年 | 145篇 |
2020年 | 142篇 |
2019年 | 172篇 |
2018年 | 17782篇 |
2017年 | 18434篇 |
2016年 | 9260篇 |
2015年 | 1782篇 |
2014年 | 682篇 |
2013年 | 899篇 |
2012年 | 8052篇 |
2011年 | 21922篇 |
2010年 | 12534篇 |
2009年 | 12995篇 |
2008年 | 16985篇 |
2007年 | 22306篇 |
2006年 | 1012篇 |
2005年 | 8966篇 |
2004年 | 5418篇 |
2003年 | 5648篇 |
2002年 | 2663篇 |
2001年 | 842篇 |
2000年 | 947篇 |
1999年 | 415篇 |
1998年 | 407篇 |
1997年 | 322篇 |
1996年 | 478篇 |
1995年 | 327篇 |
1994年 | 271篇 |
1993年 | 245篇 |
1992年 | 209篇 |
1991年 | 232篇 |
1990年 | 206篇 |
1989年 | 200篇 |
1988年 | 196篇 |
1987年 | 176篇 |
1986年 | 164篇 |
1985年 | 185篇 |
1984年 | 191篇 |
1983年 | 160篇 |
1982年 | 175篇 |
1981年 | 172篇 |
1980年 | 175篇 |
1979年 | 169篇 |
1978年 | 184篇 |
1976年 | 104篇 |
1975年 | 91篇 |
1973年 | 132篇 |
1969年 | 88篇 |
1968年 | 117篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
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
2.
3.
4.
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
5.
Martin Obst 《Aequationes Mathematicae》2018,92(1):135-163
Measuring angles in the Euclidean plane is a well-known topic, but for general normed planes there exists a variety of different concepts. These can be of a special kind, e.g. also preserving special orthogonality types. But these concepts are no angle measures in the sense of measure theory since they are not additive. This motivates us to define a new angle measure for normed planes that is in fact a measure in the sense of measure theory. Furthermore, we look at related types of rotation and reflection. 相似文献
6.
Achieving tunable band gaps in a structure by external stimuli is of great importance in acoustic applications. This paper aims to investigate the tunability of band gaps in square-lattice-like elastic periodic structures that are usually not featured with notable band gaps.Endowed with chirality, the periodic structures here are able to undergo imperfection-insensitive large deformation under extension or compression. The influences of geometric parameters on band gaps are discussed via the nonlinear finite element method. It is shown that the band gaps in such structures with curved beams can be very rich and, more importantly, can be efficiently and robustly tuned by applying appropriate mechanical loadings without inducing buckling. As expected, geometry plays a more significant role than material nonlinearity does in the evolution of band gaps. The dynamic tunability of band gaps through mechanical loading is further studied. Results show that closing, opening, and shifting of band gaps can be realized by exerting real-time global extension or compression on the structure. The proposed periodic structure with well-designed chiral symmetry can be useful in the design of particular acoustic devices. 相似文献
7.
We analyze isolated resonance curves (IRCs) in single-degree-of-freedom systems possessing nonlinear damping. Through the combination of singularity theory and the averaging method, the onset and merging of IRCs, which coincide to isola and simple bifurcation singularities, respectively, can be analytically predicted. Numerical simulations confirm the accuracy of the analytical developments. Another important finding of this paper is that we unveil a geometrical connection between the topology of the damping force and IRCs. Specifically, we demonstrate that extremas and zeros of the damping force correspond to the appearance and merging of IRCs. Considering a damping force possessing several minima and maxima confirms the general validity of the analytical result. It also evidences a very complex scenario for which different IRCs are created, co-exist and then merge together to form a super IRC which eventually merges with the main resonance peak. 相似文献
8.
9.
10.
Arkadiusz Lewandowski 《Archiv der Mathematik》2018,111(5):503-511
We give the parameter version of a localization theorem for the Bergman metric near the boundary points of strictly pseudoconvex domains. The approximation theorem for square integrable holomorphic functions on such domains in the spirit of Graham-Kerzman is proved in the hereby paper, as well. 相似文献