全文获取类型
收费全文 | 249531篇 |
免费 | 4223篇 |
国内免费 | 744篇 |
专业分类
化学 | 138480篇 |
晶体学 | 3069篇 |
力学 | 9240篇 |
综合类 | 9篇 |
数学 | 29226篇 |
物理学 | 74474篇 |
出版年
2018年 | 2026篇 |
2017年 | 1955篇 |
2016年 | 3879篇 |
2015年 | 2993篇 |
2014年 | 3839篇 |
2013年 | 10821篇 |
2012年 | 7873篇 |
2011年 | 9548篇 |
2010年 | 6190篇 |
2009年 | 5855篇 |
2008年 | 8810篇 |
2007年 | 8841篇 |
2006年 | 8348篇 |
2005年 | 7574篇 |
2004年 | 6752篇 |
2003年 | 5867篇 |
2002年 | 5654篇 |
2001年 | 6790篇 |
2000年 | 5340篇 |
1999年 | 4149篇 |
1998年 | 3272篇 |
1997年 | 3309篇 |
1996年 | 3442篇 |
1995年 | 3172篇 |
1994年 | 3114篇 |
1993年 | 3087篇 |
1992年 | 3517篇 |
1991年 | 3132篇 |
1990年 | 3129篇 |
1989年 | 3104篇 |
1988年 | 3014篇 |
1987年 | 3040篇 |
1986年 | 2829篇 |
1985年 | 3927篇 |
1984年 | 3910篇 |
1983年 | 3248篇 |
1982年 | 3361篇 |
1981年 | 3320篇 |
1980年 | 3183篇 |
1979年 | 3329篇 |
1978年 | 3592篇 |
1977年 | 3407篇 |
1976年 | 3278篇 |
1975年 | 3105篇 |
1974年 | 3038篇 |
1973年 | 3048篇 |
1972年 | 1923篇 |
1968年 | 2164篇 |
1967年 | 2402篇 |
1966年 | 2174篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Alawainati F. A. Manaa H. Henari F. Z. Biyiklioglu Z. Arslan T. Jaafar A. 《Journal of Applied Spectroscopy》2021,88(5):951-957
Journal of Applied Spectroscopy - Detailed measurements of nonlinear optical properties and optical limiting for four phthalocyanine (Pc) derivatives (PcCo, PcCu, PcMn, and PcSi) are reported. The... 相似文献
12.
Analysis Mathematica - We introduce and study the k-Hankel Gabor transform. We investigate the localization operators for this transform. In particular, we study their trace class properties and we... 相似文献
13.
14.
Li Y. Shi W. H. Dong L. M. Xu S. X. Huang H. J. Yin J. R. 《Journal of Applied Spectroscopy》2022,89(3):534-541
Journal of Applied Spectroscopy - Sr3B2O6:Dy3+, Eu3+ single-matrix white-light-emitting materials are prepared using the high-temperature solid-state method. The microstructure, emission spectrum,... 相似文献
15.
Vasile M. Loots H. Vercammen L. Bruggeman M. Verrezen F. 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(8):3349-3357
Journal of Radioanalytical and Nuclear Chemistry - In this paper a study for the selection of an NPE (nonylphenol ethoxylates)—free cocktail is discussed in order to be used for our routine... 相似文献
16.
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
17.
18.
In a 2:2 reaction with silver(I) chloride or bromide, 1,5-bis(1-phospholano)pentane ( 1a ) afforded frame-like macrocyclic structures, with intra- ( 2 , Cl) or intermolecular ( 3 , Br) halido bridges. In contrast, 1,7-bis(1-phospholano)heptane ( 1b ) formed coordination polymers 4a (Cl) and 4b (Br) with bridging bis-phospholane and halido ligands. A unique paddle wheel-type metallacryptand structure 5 was obtained from 1a and silver(I) bromide in a 2:3 reaction (M:L). All complexes were fully characterized by NMR, IR spectroscopy, mass spectrometry, and X-ray crystallography. 相似文献
19.
Laurens Kooijman Dr. Matthias Schuster Christian Baumann Simon Jurt Dr. Frank Löhr Dr. Boris Fürtig Prof. Dr. Peter Güntert Prof. Dr. Oliver Zerbe 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(47):21151-21158
To achieve efficient proton pumping in the light-driven proton pump bacteriorhodopsin (bR), the protein must be tightly coupled to the retinal to rapidly convert retinal isomerization into protein structural rearrangements. Methyl group dynamics of bR embedded in lipid nanodiscs were determined in the dark-adapted state, and were found to be mostly well ordered at the cytosolic side. Methyl groups in the M145A mutant of bR, which displays only 10 % residual proton pumping activity, are less well ordered, suggesting a link between side-chain dynamics on the cytosolic side of the bR cavity and proton pumping activity. In addition, slow conformational exchange, attributed to low frequency motions of aromatic rings, was indirectly observed for residues on the extracellular side of the bR cavity. This may be related to reorganization of the water network. These observations provide a detailed picture of previously undescribed equilibrium dynamics on different time scales for ground-state bR. 相似文献
20.
Cavitation erosion is caused in solids exposed to strong pressure waves developing in an adjacent fluid field. The knowledge of the transient distribution of stresses in the solid is important to understand the cause of damaging by comparisons with breaking points of the material. The modeling of this problem requires the coupling of the models for the fluid and the solid. For this purpose, we use a strategy based on the solution of coupled Riemann problems that has been originally developed for the coupling of 2 fluids. This concept is exemplified for the coupling of a linear elastic structure with an ideal gas. The coupling procedure relies on the solution of a nonlinear equation. Existence and uniqueness of the solution is proven. The coupling conditions are validated by means of quasi‐1D problems for which an explicit solution can be determined. For a more realistic scenario, a 2D application is considered where in a compressible single fluid, a hot gas bubble at low pressure collapses in a cold gas at high pressure near an adjacent structure. 相似文献