全文获取类型
收费全文 | 26790篇 |
免费 | 4437篇 |
国内免费 | 4037篇 |
专业分类
化学 | 20610篇 |
晶体学 | 427篇 |
力学 | 1324篇 |
综合类 | 297篇 |
数学 | 2958篇 |
物理学 | 9648篇 |
出版年
2024年 | 95篇 |
2023年 | 492篇 |
2022年 | 932篇 |
2021年 | 993篇 |
2020年 | 1074篇 |
2019年 | 1127篇 |
2018年 | 949篇 |
2017年 | 989篇 |
2016年 | 1290篇 |
2015年 | 1335篇 |
2014年 | 1675篇 |
2013年 | 2076篇 |
2012年 | 2489篇 |
2011年 | 2544篇 |
2010年 | 1947篇 |
2009年 | 1836篇 |
2008年 | 1950篇 |
2007年 | 1803篇 |
2006年 | 1684篇 |
2005年 | 1345篇 |
2004年 | 988篇 |
2003年 | 783篇 |
2002年 | 740篇 |
2001年 | 652篇 |
2000年 | 574篇 |
1999年 | 482篇 |
1998年 | 354篇 |
1997年 | 312篇 |
1996年 | 266篇 |
1995年 | 254篇 |
1994年 | 233篇 |
1993年 | 168篇 |
1992年 | 147篇 |
1991年 | 136篇 |
1990年 | 122篇 |
1989年 | 89篇 |
1988年 | 73篇 |
1987年 | 53篇 |
1986年 | 61篇 |
1985年 | 49篇 |
1984年 | 19篇 |
1983年 | 18篇 |
1982年 | 19篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1978年 | 3篇 |
1971年 | 4篇 |
1957年 | 5篇 |
1936年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Yin Su Zuo‐Chang Chen Han‐Rui Tian Yun‐Yan Xu Qianyan Zhang Su‐Yuan Xie Lan‐Sun Zheng 《中国化学》2021,39(1):93-98
Because of its unsaturated bonds, C60 is susceptible to polymerize into dimers. The implications of nitrogen doping on the geometrical and electronic structure of C60 dimers have been ambiguous for years. A quarter‐century after the discovery of azafullerene dimer (C59N)2, we reported its single crystallographic structure in 2019. Herein, the unambiguous crystal structure information of (C59N)2 is elucidated specifically, revealing that the inter‐cage C—C single bond length of (C59N)2 is comparable with that of an ordinary C(sp3)‐C(sp3) single bond, and that the most stable conformer of (C59N)2 is gauche‐conformer with a dihedral angle of 66°. To amend the structural deviations, geometrical structure of (C59N)2 is optimized by a B3LYP‐D3BJ function, which is proved to be more consistent with its single crystal structure than those by the commonly used B3LYP function. Moreover, the calculation method is also suitable for other representative fullerene dimers, such as (C60)2 and its divalent anion. Additionally, the dissociation of (C59N)2 at 473 K under mass spectrometric conditions suggests the inter‐cage C—C bond is relatively weaker than an ordinary C—C single bond, which can be explained by the interaction energies of inter‐cages. 相似文献
992.
Yaqin Liu Yan Zheng Shaoyuan Li Jinhan Li Xiaoyu Du Yanyun Ma Guofu Liao Qing Wang Xiaohai Yang Kemin Wang 《中国化学快报》2021,31(12):3113-3116
The effect of gold nanoparticle-decorated molybdenum sulfide (AuNP-MoS2) nanocomposites on amyloid-β-40 (Aβ40) aggregation was investigated. The interesting discovery was that the effect of AuNP-MoS2 nanocomposites on Aβ40 aggregation was contradictory. Low concentration of AuNP-MoS2 nanocomposites could enhance the nucleus formation of Aβ40 peptides and accelerate Aβ40 fibrils aggregation. However, although high concentration of AuNP-MoS2 nanocomposites could enhance the nucleus formation of Aβ40 peptides, it eventually inhibited Aβ40 aggregation process. It might be attributed to the interaction between AuNP-MoS2 nanocomposites and Aβ40 peptides. For low concentration of AuNP-MoS2 nanocomposites, it was acted as nuclei, resulting in the acceleration of the nucleation process. However, the structural flexibility of Aβ40 peptides was limited as the concentration of AuNP-MoS2 nanocomposites was increased, resulting in the inhibition of Aβ40 aggregation. These findings suggested that AuNP-MoS2 nanocomposites might have a great potential to design new multifunctional material for future treatment of amyloid-related diseases. 相似文献
993.
Mubashir Hussain Zhen Chen Mu Lv Jingyi Xu Xiaohan Dong Jingzhou Zhao Song Li Yan Deng Nongyue He Zhiyang Li Bin Liu 《中国化学快报》2021,31(12):3163-3167
The rapid identification of pathogens is crucial in controlling the food quality and safety. The proposed system for the rapid and label-free identification of pathogens is based on the principle of laser scattering from the bacterial microbes. The clinical prototype consists of three parts: the laser beam, photodetectors, and the data acquisition system. The bacterial testing sample was mixed with 10 mL distilled water and placed inside the machine chamber. When the bacterial microbes pass by the laser beam, the scattering of light occurs due to variation in size, shape, and morphology. Due to this reason, different types of pathogens show their unique light scattering patterns. The photo-detectors were arranged at the surroundings of the sample at different angles to collect the scattered light. The photodetectors convert the scattered light intensity into a voltage waveform. The waveform features were acquired by using the power spectral characteristics, and the dimensionality of extracted features was reduced by applying minimal-redundancy-maximal-relevance criterion (mRMR). A support vector machine (SVM) classifier was developed by training the selected power spectral features for the classification of three different bacterial microbes. The resulting average identification accuracies of E. faecalis,E. coli and S. aureus were 99%, 87%, and 94%, respectively. The overall experimental results yield a higher accuracy of 93.6%, indicating that the proposed device has the potential for label-free identification of pathogens with simplicity, rapidity, and cost-effectiveness. 相似文献
994.
Zhiguo Lu Xiangyu Wang Tianlu Zhang Luyao Zhang Jun Yang Yan Li Jie Shen Jianze Wang Yunwei Niu Zuobing Xiao Guiying Liu Xin Zhang 《中国化学快报》2021,31(12):3139-3142
Silk has been widely used in the clothing industry due to their soft and smooth features, good biocompatibility, good heat dissipation, warmth and ultraviolet resistance. The application of fragrance to silk can significantly improve the performance of silk. However, there are two key scientific problems that need to be solved: slowing down the release rate of fragrances and increasing the scent lasting time of silk. In this study, cationic and temperature-sensitive liposomes were designed and prepared to encapsulate eugenol. These fragrance-loaded liposomes significantly slowed down the release rate of the fragrance and controlled the release rate of the fragrance in a thermo-sensitive manner. The liposomes adhered to the silk through electrostatic adsorption interaction. The positive charge on the fragrance-loaded liposomes neutralized much negative charge on silk and thereby increasing the adhesion efficiency. 相似文献
995.
996.
Tungsten oxide (WO3) films were prepared on indium–tin oxide (ITO) glass by sol–gel method. The influence of annealing temperature on the structural, morphological, optical, electrochemical, and electrochromic properties has been investigated. The film annealed at 250 °C with an amorphous structure exhibits a noticeable electrochromic performance, such as the highest optical modulation of 58.5 % at 550 nm, high electrochemical stability, and excellent reversibility (Q b/Q c?=?96.3 %). An electrochromic (EC) device based on WO3/NiO complementary structure shows improved performance. It exhibits high optical transmittance modulation of 62 % at 550 nm, excellent cycling stability, and relatively fast electrochromic response time (10 s for coloration and 19 s for bleaching). 相似文献
997.
998.
999.
A novel imaging tool for hepatic portal system using phase contrast technique with hydrogen peroxide‐generated O2 gas 下载免费PDF全文
Rongbiao Tang Fuhua Yan Wei‐Min Chai Wei Huang Yanan Fu Guo‐Yuan Yang Ke‐Min Chen 《Journal of synchrotron radiation》2015,22(5):1263-1267
The objective of this study was to investigate the potential of hydrogen peroxide‐generated oxygen gas‐based phase contrast imaging (PCI) for visualizing mouse hepatic portal veins. The O2 gas was made from the reaction between H2O2 and catalase. The gas production was imaged by PCI in real time. The H2O2 was injected into the enteric cavity of the lower sigmoid colon to produce O2 in the submucosal venous plexus. The generated O2 gas could be finally drained into hepatic portal veins. Absorption contrast imaging (ACI) and PCI of O2‐filled portal veins were performed and compared. PCI offers high resolution and real‐time visualization of the O2 gas production. Compared with O2‐based ACI, O2‐based PCI significantly enhanced the revealing of the portal vein in vivo. It is concluded that O2‐based PCI is a novel and promising imaging modality for future studies of portal venous disorders in mice models. 相似文献
1000.
开关技术是影响爆炸箔起爆系统可靠作用、微型化、低能化、集成化的关键技术。电爆炸平面开关是利用强脉冲电流使触发极金属桥箔发生电爆炸,产生高温高压等离子体,使爆炸桥区两侧的电极导通。基于微加工技术,采用Al/CuO复合薄膜材料作为触发电极,设计制造了微型平面复合薄膜电爆炸开关。采用扫描电子显微镜、差示扫描量热法和光谱谱线测温研究了触发极Al/CuO复合薄膜的形貌、反应性和电爆炸等离子体温度,通过放电电流测试研究了开关性能。结果表明,在主回路电压2000V时,开关输出电流峰值约为1938A,上升时间390ns,性能优于仅以铜薄膜为触发电极的电爆炸平面开关。 相似文献