全文获取类型
收费全文 | 18380篇 |
免费 | 1135篇 |
国内免费 | 1643篇 |
专业分类
化学 | 14135篇 |
晶体学 | 167篇 |
力学 | 412篇 |
综合类 | 53篇 |
数学 | 2428篇 |
物理学 | 3963篇 |
出版年
2023年 | 145篇 |
2022年 | 109篇 |
2021年 | 414篇 |
2020年 | 341篇 |
2019年 | 401篇 |
2018年 | 331篇 |
2017年 | 311篇 |
2016年 | 684篇 |
2015年 | 567篇 |
2014年 | 646篇 |
2013年 | 1347篇 |
2012年 | 1501篇 |
2011年 | 1602篇 |
2010年 | 934篇 |
2009年 | 1172篇 |
2008年 | 1138篇 |
2007年 | 1097篇 |
2006年 | 950篇 |
2005年 | 1006篇 |
2004年 | 1266篇 |
2003年 | 883篇 |
2002年 | 783篇 |
2001年 | 437篇 |
2000年 | 310篇 |
1999年 | 253篇 |
1998年 | 240篇 |
1997年 | 206篇 |
1996年 | 208篇 |
1995年 | 191篇 |
1994年 | 136篇 |
1993年 | 159篇 |
1992年 | 131篇 |
1991年 | 91篇 |
1990年 | 112篇 |
1989年 | 81篇 |
1988年 | 77篇 |
1987年 | 63篇 |
1986年 | 83篇 |
1985年 | 96篇 |
1984年 | 92篇 |
1983年 | 69篇 |
1982年 | 58篇 |
1981年 | 61篇 |
1980年 | 51篇 |
1979年 | 36篇 |
1978年 | 32篇 |
1977年 | 37篇 |
1976年 | 27篇 |
1975年 | 25篇 |
1974年 | 30篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
63.
64.
Juan M. Muñoz-Ocaña Ainouna Bouziane Farzeen Sakina Richard T. Baker Ana B. Hungría Jose J. Calvino Antonio M. Rodríguez-Chía Miguel López-Haro 《Particle & Particle Systems Characterization》2020,37(6):2000070
A novel procedure to optimize the 3D morphological characterization of nanomaterials by means of high angle annular dark field scanning-transmission electron tomography is reported and is successfully applied to the analysis of a metal- and halogen-free ordered mesoporous carbon material. The new method is based on a selection of the two parameters (μ and β) which are key in the reconstruction of tomographic series by means of total variation minimization (TVM). The parameter-selected TVM reconstructions obtained using this approach clearly reveal the porous structure of the carbon-based material as consisting of a network of parallel, straight channels of ≈6 nm diameter ordered in a honeycomb-type arrangement. Such an unusual structure cannot be retrieved from a TVM 3D reconstruction using default reconstruction values. Moreover, segmentation and further quantification of the optimized 3D tomographic reconstruction provide values for different textural parameters, such as pore size distribution and specific pore volume that match very closely with those determined by macroscopic physisorption techniques. The approach developed can be extended to other reconstruction models in which the final result is influenced by parameter choice. 相似文献
65.
Dr. Joaquim Torra Dr. Felipe Viela Dr. Diego Megías Dr. Begoña Sot Prof. Cristina Flors 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(19):e202200026
CRANAD-2 is a fluorogenic curcumin derivative used for near-infrared detection and imaging in vivo of amyloid aggregates, which are involved in neurodegenerative diseases. We explore the performance of CRANAD-2 in two super-resolution imaging techniques, namely stimulated emission depletion (STED) and single-molecule localization microscopy (SMLM), with markedly different fluorophore requirements. By conveniently adapting the concentration of CRANAD-2, which transiently binds to amyloid fibrils, we show that it performs well in both techniques, achieving a resolution in the range of 45–55 nm. Correlation of SMLM with atomic force microscopy (AFM) validates the resolution of fine features in the reconstructed super-resolved image. The good performance and versatility of CRANAD-2 provides a powerful tool for near-infrared nanoscopic imaging of amyloids in vitro and in vivo. 相似文献
66.
Maldonado-Bustamante Sara Roxana Mondaca-Fernndez Iram Gortares-Moroyoqui Pablo Berg Alex Balderas-Corts Jos de Jess Meza-Montenegro Mara Mercedes Brown-Bojrquez Francisco Arvayo-Enrquez Hctor 《Cellulose (London, England)》2022,29(13):7151-7161
Cellulose - The present study investigates the organosolv treatment of wheat straw, for the optimization of cellulose delignification, which will serve as raw material for the paper industry. The... 相似文献
67.
Pastor-Belda Marta Arroyo-Manzanares Natalia Campillo Natalia Vias Pilar Guluarte Crystal Angulo Carlos Esteban Mara ngeles 《Chromatographia》2022,85(4):353-363
Chromatographia - Nucleobases, nucleosides and nucleotides can act as chemical markers and immunnostimulants. Ultra-high-performance liquid chromatography with electrospray ionization and... 相似文献
68.
The batch emulsion copolymerization of vinyl acetate with different vinyl silane functional monomers (vinyl trimethoxysilane [VTMS], vinyl triethoxysilane [VTES], and vinyl silanetriol [VSTO]) is studied. The nature of the silane strongly affects the development of the microstructure and crosslinking ability of the latexes. A combination of techniques (Soxhlet extraction, centrifugation, assymetric‐flow field flow fractionation AF4/MALS/RI) shows that the factor controlling the molar mass and crosslinking density is the degree of hydrolysis of the alkoxysilane, producing higher molar masses and degrees of crosslinking when the degree of hydrolysis is high. Thus, the copolymer containing VSTO produced a very crosslinked latex, the one with VTMS produced a latex with a low degree of crosslinking in the wet state that can yield high degrees of crosslinking upon drying, and the latex with VTES do not produce significant amounts of crosslinking neither before nor after drying. 相似文献
69.
Alberto Blzquez-Moraleja Ines Senz-de-Santa María María D. Chiara Delia lvarez-Fernndez Inmaculada García-Moreno Ruth Prieto-Montero Virginia Martínez-Martínez Iigo Lpez Arbeloa Jose Luis Chiara 《Chemical science》2020,11(4):1052
The first fluorescent probes that are actively channeled into the mitochondrial matrix by a specific mitochondrial membrane transporter in living cells have been developed. The new functional probes (BCT) have a minimalist structural design based on the highly efficient and photostable BODIPY chromophore and carnitine as a biotargeting element. Both units are orthogonally bonded through the common boron atom, thus avoiding the use of complex polyatomic connectors. In contrast to known mitochondria-specific dyes, BCTs selectively label these organelles regardless of their transmembrane potential and in an enantioselective way. The obtained experimental evidence supports carnitine–acylcarnitine translocase (CACT) as the key transporter protein for BCTs, which behave therefore as acylcarnitine biomimetics. This simple structural design can be readily extended to other structurally diverse starting F-BODIPYs to obtain BCTs with varied emission wavelengths along the visible and NIR spectral regions and with multifunctional capabilities. BCTs are the first fluorescent derivatives of carnitine to be used in cell microscopy and stand as promising research tools to explore the role of the carnitine shuttle system in cancer and metabolic diseases. Extension of this approach to other small-molecule mitochondrial transporters is envisaged.A BODIPY derivative of carnitine enters mitochondria regardless of their membrane potential and in an enantioselective way through a specific mitochondrial membrane transporter in living cells. 相似文献
70.
Potential Analysis - We prove well-posedness results for the Dirichlet problem in $\mathbb {R}^{n}_{+}$ for homogeneous, second order, constant complex coefficient elliptic systems with boundary... 相似文献