全文获取类型
收费全文 | 3437篇 |
免费 | 357篇 |
国内免费 | 347篇 |
专业分类
化学 | 2483篇 |
晶体学 | 31篇 |
力学 | 184篇 |
综合类 | 40篇 |
数学 | 323篇 |
物理学 | 1080篇 |
出版年
2025年 | 3篇 |
2024年 | 38篇 |
2023年 | 77篇 |
2022年 | 124篇 |
2021年 | 155篇 |
2020年 | 174篇 |
2019年 | 153篇 |
2018年 | 100篇 |
2017年 | 102篇 |
2016年 | 152篇 |
2015年 | 137篇 |
2014年 | 197篇 |
2013年 | 236篇 |
2012年 | 244篇 |
2011年 | 289篇 |
2010年 | 191篇 |
2009年 | 160篇 |
2008年 | 169篇 |
2007年 | 166篇 |
2006年 | 145篇 |
2005年 | 137篇 |
2004年 | 115篇 |
2003年 | 92篇 |
2002年 | 95篇 |
2001年 | 84篇 |
2000年 | 76篇 |
1999年 | 78篇 |
1998年 | 74篇 |
1997年 | 51篇 |
1996年 | 54篇 |
1995年 | 41篇 |
1994年 | 45篇 |
1993年 | 29篇 |
1992年 | 38篇 |
1991年 | 15篇 |
1990年 | 24篇 |
1989年 | 13篇 |
1988年 | 10篇 |
1987年 | 6篇 |
1986年 | 10篇 |
1985年 | 8篇 |
1984年 | 15篇 |
1983年 | 9篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有4141条查询结果,搜索用时 15 毫秒
101.
102.
103.
104.
Cyclometalated Iridium(III) Complexes as Two‐Photon Phosphorescent Probes for Specific Mitochondrial Dynamics Tracking in Living Cells
下载免费PDF全文

Chengzhi Jin Jiangping Liu Dr. Yu Chen Leli Zeng Ruilin Guan Cheng Ouyang Prof. Liangnian Ji Prof. Dr. Hui Chao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(34):12000-12010
Five cyclometalated iridium(III) complexes with 2‐phenylimidazo[4,5‐f][1,10]phenanthroline derivatives ( IrL1 – IrL5 ) were synthesized and developed to image and track mitochondria in living cells under two‐photon (750 nm) excitation, with two‐photon absorption cross‐sections of 48.8–65.5 GM at 750 nm. Confocal microscopy and inductive coupled plasma‐mass spectrometry (ICP‐MS) demonstrated that these complexes selectively accumulate in mitochondria within 5 min, without needing additional reagents for membrane permeabilization, or replacement of the culture medium. In addition, photobleaching experiments and luminescence measurements confirmed the photostability of these complexes under continuous laser irradiation and physiological pH resistance. Moreover, results using 3D multicellular spheroids demonstrate the proficiency of these two‐photon luminescent complexes in deep penetration imaging. Two‐photon excitation using such novel complexes of iridium(III) for exclusive visualization of mitochondria in living cells may substantially enhance practical applications of bioimaging and tracking. 相似文献
105.
Sen Hou Xin-Xin Li Xiao-Yu Li Xi-Zeng Feng Li Guan Yan-Lian Yang Chen Wang 《Analytical and bioanalytical chemistry》2009,394(8):2111-2117
Controllable cell growth on the defined areas of surfaces is important for potential applications in biosensor fabrication
and tissue engineering. In this study, controllable cell growth was achieved by culturing 293 T fibroblast cells on a mica
surface which had been patterned with collagen strips by a microcontact printing (μCP) technique. The collagen area was designed
to support cell adhesion and the native mica surface was designed to repel cell adhesion. Consequently, the resulting cell
patterns should follow the micro-patterns of the collagen. X-ray photoelectron spectroscopy (XPS), water contact angle (WCA)
measurement, atomic-force microscope (AFM) observation, and force-curve measurement were used to monitor property changes
before and after the collagen adsorption process. Further data showed that the patterned cells were of good viability and
able to perform a gene-transfection experiment in vitro. This technique should be of potential applications in the fields
of biosensor fabrication and tissue engineering.
Figure Controllable cells growth has been achieved by culturing 293T fibroblast cells on the mica surface which had been patterned
with collagen strips by microcontact printing (μCP) technique 相似文献
106.
Because fossil fuels are continuously depleted, valorization of biomass into valuable liquid products and chemicals is of great significance yet it remains challenging. Among many biomass-derived products, lactic acid is one of the most important renewable monomers for preparing the degradable polymer polylactic acid. The use of raw biomass to produce lactic acid through catalytic conversion is an attractive approach. In this work, the catalytic reaction performance and mechanism of different Lewis acids (Y3+, Sc3+, and Al3+) for the production of lactic acid from cellulose were investigated in detail by isotopic nuclear magnetic resonance (NMR) and mass spectrometry. The production of lactic acid from cellulose includes tandem and competing reactions. The order of catalytic activity for the one-pot conversion of cellulose into lactic acid is as follows: Y3+ > Al3+ > Sc3+. The main tandem reactions involve the hydrolysis of cellulose into glucose, the isomerization of glucose into fructose (the order of catalytic activity, the same below: Y3+ > Al3+, Y3+ > Sc3+), the cleavage of fructose via a retro-aldol reaction to glyceraldehyde (GLY) and 1, 3-dihydroxyacetone (DHA) (Sc3+ > Y3+ > Al3+), and the conversion of DHA or GLY to the final product lactic acid (Al3+ > Y3+ > Sc3+). It was found that the process of glucose isomerization to fructose was the key step to the final selectivity of the tandem reaction of cellulose conversion to lactic acid, and it was clarified that the production of lactic acid from DHA underwent a keto-enol (K-E) tautomerization process rather than a classical 1, 2-shift process. First, DHA was transformed into GLY via the isomerization process, then the adjacent hydroxyl group of GLY was removed in the form of water to produce an α, β-unsaturated species. After that, the α, β-unsaturated species underwent K-E tautomerization to generate unsaturated aldehyde-ketone intermediates. Meanwhile, a molecule of water was added to aldehyde-ketone intermediates to obtain a diol product, the hydrogen atom at the methine position was transferred and the lactic acid was finally obtained through the K-E tautomerization process. The in-depth understanding of the reaction mechanism presented in this work will help to design more selective catalysts for cellulose conversion into value-added oxygen-containing small molecule chemicals.
相似文献
107.
内蒙古牧区老年冠心病患者血清Zn,Cu,Ca,Mg的测定及临床意义 总被引:1,自引:0,他引:1
用薄样X射线荧光光谱法测定较区91老年冠心病患者及63名老年健康人血清Zn、Cu、Ca、Mg、四种元素的含量。结果表明:牧区老年冠心病患者血清中Zn、Cu、含量与健康组比较无显著差异,但两者的比值高于对照组,可能与牧区牧民饮食习惯有关;老年冠心病组血清Ca、Mg含量显著低于对照组。 相似文献
108.
中药微量元素含量区间尺最佳分级问题的探讨 总被引:1,自引:0,他引:1
在深入研究中药微量元素含量区间尺的基础上,从统计学角度对区间尺的最佳分级问题作了详细探讨,提出用5级区间尺来衡量中药中不同元素含量间相对高低水平,理论上更合理。 相似文献
109.
Qing-Qing Guan Xiao-Dian Huang Yan-Hua Zeng Chao-Hai Wei Ping Ning Gu Jun-Jie Xin-Sheng Chai 《Chemical Papers》2015,69(5):662-667
This paper reports a headspace analysis technique for the determination of products, i.e., cyclohexanone (CE) and cyclohexanol (CL), of phenol hydrogenation in a supercritical water reaction system (SWRS) with water removal by hydrate formation. An addition of anhydrous calcium chloride leads to water absorption resulting in crystal water; thus, the samples can be quantitatively measured without the influence of water. After achieving equilibrium at 150°C and maintaining it for 5 min, the obtained results showed a relative standard deviation of less than 5.3% and the recovery ranged from 93% to 104%. The presented method is simple and accurate for the analysis of CL, CE and phenol in samples from phenol conversion in SWRS. 相似文献
110.
Gold triangular nanoplates with a uniform size were synthesized by a simple seeds-growth method in a lamellar lyotropic liquid crystal (LLC) medium consisting of F127, n-C4H9OH and H2O. The edge length of gold nanoplates can be adjusted from tens to several hundreds nanometers (and even a few micrometers) by varying the concentration of Au3+ and the seeds solution volume. The optical properties of the synthesized gold nanoplates were studied. The vis-NIR spectra of the synthesized gold nanoplates exhibited a good linear correlation between the in-plane plasmon resonance λmax and the average edge length of the corresponding nanoplates.
相似文献