全文获取类型
收费全文 | 2494篇 |
免费 | 197篇 |
国内免费 | 174篇 |
专业分类
化学 | 1720篇 |
晶体学 | 49篇 |
力学 | 92篇 |
综合类 | 15篇 |
数学 | 272篇 |
物理学 | 717篇 |
出版年
2023年 | 49篇 |
2022年 | 74篇 |
2021年 | 55篇 |
2020年 | 91篇 |
2019年 | 75篇 |
2018年 | 55篇 |
2017年 | 59篇 |
2016年 | 105篇 |
2015年 | 70篇 |
2014年 | 110篇 |
2013年 | 144篇 |
2012年 | 168篇 |
2011年 | 174篇 |
2010年 | 98篇 |
2009年 | 91篇 |
2008年 | 111篇 |
2007年 | 129篇 |
2006年 | 102篇 |
2005年 | 104篇 |
2004年 | 72篇 |
2003年 | 60篇 |
2002年 | 63篇 |
2001年 | 49篇 |
2000年 | 53篇 |
1999年 | 40篇 |
1998年 | 22篇 |
1997年 | 37篇 |
1996年 | 43篇 |
1995年 | 30篇 |
1994年 | 31篇 |
1993年 | 25篇 |
1992年 | 29篇 |
1991年 | 17篇 |
1990年 | 20篇 |
1989年 | 18篇 |
1988年 | 14篇 |
1987年 | 15篇 |
1986年 | 24篇 |
1985年 | 18篇 |
1983年 | 16篇 |
1982年 | 17篇 |
1981年 | 10篇 |
1980年 | 15篇 |
1979年 | 16篇 |
1978年 | 11篇 |
1977年 | 23篇 |
1976年 | 13篇 |
1975年 | 18篇 |
1972年 | 9篇 |
1971年 | 9篇 |
排序方式: 共有2865条查询结果,搜索用时 15 毫秒
31.
Da-Liang Zhu Qi Wu Prof. Hai-Yan Li Prof. Dr. Hong-Xi Li Prof. Dr. Jian-Ping Lang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(16):3484-3488
Diethyl 2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate (HEH) has been utilized as a visible-light photoredox catalyst for the cross coupling of arylhalides and arylsulfinates without transition metal, sacrificial agent, and mediator. This method is compatible with various functional groups and provides diaryl sulfones in good to high yields. Mechanistic studies indicate that this reaction undergoes the stepwise light irradiation of HE−, single electron transfer (SET) in donor–acceptor complex (DAC) from *HE− to arylhalide, trapping of aryl radical with sulfinate, and SET oxidation of sulfone radical anion by HE. to sulfone by the DAC method. 相似文献
32.
International Journal of Theoretical Physics - Quantum private comparison (QPC) can tell us whether two users’ private data are equal or not by quantum technology without disclosing privacy... 相似文献
33.
Nous présentons un cadre unificateur pour un certain nombre de résultats connus de convergence en loi pour des processus admettant une représentation linéaire par rapport à un bruit blanc faible pour lequel il existe un principe dinvariance faible. Nous montrons que ce principe dinvariance est équivalent à la convergence dune suite de mesures aléatoires spectrales. Ceci permet daffaiblir les hypothèses usuelles et donc dobtenir des résultats nouveaux de convergence en loi, notamment pour des processus à longue portée. 相似文献
34.
35.
Abstract
Highly substituted novel 4H-pyrimido[1,6-a] pyrimidines were prepared by a trifluoromethanesulfonic acid catalyzed one-pot three-component condensation of 4-aminopyrimidines, aldehydes, and β-ketoesters. A preliminary feasibility study was undertaken on these compounds, to assess the potential production of a library of further diversified compounds by nucleophilic replacement of Cl (R1) or by reaction of electrophiles with the NH2 (R2) group. 相似文献36.
H.P. Lang A. Filippi A. Tonin F. Huber N. Backmann J. Zhang Ch. Gerber 《Procedia Chemistry》2009,1(1):208-211
Microfabricated silicon cantilever sensor arrays represent a powerful platform for sensing applications in physics, chemistry, material science, biology and medicine. The sensor response is mechanical bending due to absorption of molecules. In gaseous environment, polymer-coated microcantilevers are used as electronic nose for characterization of vapors, resulting in cantilever bending due to polymer swelling upon exposure. Medical applications involve fast characterization of exhaled patient's breath samples for detection of diseases, based on the presence of certain chemicals in breath. We present a portable, compact, modular microcantilever setup, which uses a micropump for aspiration and a bluetooth interface for remote data acquisition. 相似文献
37.
Dr. Zhen-Zhen Shen Dr. Shuang-Yan Lang Rui-Zhi Liu Dr. Chi Zhou Yao-Zu Zhang Prof. Dr. Bing Liu Prof. Dr. Rui Wen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2024,136(1):e202316781
Lithium–carbon dioxide (Li–CO2) battery technology presents a promising opportunity for carbon capture and energy storage. Despite tremendous efforts in Li–CO2 batteries, the complex electrode/electrolyte/CO2 triple-phase interfacial processes remain poorly understood, in particular at the nanoscale. Here, using in situ atomic force microscopy and laser confocal microscopy-differential interference contrast microscopy, we directly observed the CO2 conversion processes in Li–CO2 batteries at the nanoscale, and further revealed a laser-tuned reaction pathway based on the real-time observations. During discharge, a bi-component composite, Li2CO3/C, deposits as micron-sized clusters through a 3D progressive growth model, followed by a 3D decomposition pathway during the subsequent recharge. When the cell operates under laser (λ=405 nm) irradiation, densely packed Li2CO3/C flakes deposit rapidly during discharge. Upon the recharge, they predominantly decompose at the interfaces of the flake and electrode, detaching themselves from the electrode and causing irreversible capacity degradation. In situ Raman shows that the laser promotes the formation of poorly soluble intermediates, Li2C2O4, which in turn affects growth/decomposition pathways of Li2CO3/C and the cell performance. Our findings provide mechanistic insights into interfacial evolution in Li–CO2 batteries and the laser-tuned CO2 conversion reactions, which can inspire strategies of monitoring and controlling the multistep and multiphase interfacial reactions in advanced electrochemical devices. 相似文献
38.
Liangcong Hu Xudong Xie Hang Xue Tiantian Wang Adriana C. Panayi Ze Lin Yuan Xiong Faqi Cao Chengcheng Yan Lang Chen Peng Cheng Kangkang Zha Yun Sun Guodong Liu Chenyan Yu Yiqiang Hu Ranyang Tao Wu Zhou Bobin Mi Guohui Liu 《Experimental & molecular medicine》2022,54(7):961
MicroRNAs (miRNAs) broadly regulate normal biological functions of bone and the progression of fracture healing and osteoporosis. Recently, it has been reported that miR-1224-5p in fracture plasma is a potential therapy for osteogenesis. To investigate the roles of miR-1224-5p and the Rap1 signaling pathway in fracture healing and osteoporosis development and progression, we used BMMs, BMSCs, and skull osteoblast precursor cells for in vitro osteogenesis and osteoclastogenesis studies. Osteoblastogenesis and osteoclastogenesis were detected by ALP, ARS, and TRAP staining and bone slice resorption pit assays. The miR-1224-5p target gene was assessed by siRNA-mediated target gene knockdown and luciferase reporter assays. To explore the Rap1 pathway, we performed high-throughput sequencing, western blotting, RT-PCR, chromatin immunoprecipitation assays and immunohistochemical staining. In vivo, bone healing was judged by the cortical femoral defect, cranial bone defect and femoral fracture models. Progression of osteoporosis was evaluated by an ovariectomy model and an aged osteoporosis model. We discovered that the expression of miR-1224-5p was positively correlated with fracture healing progression. Moreover, in vitro, overexpression of miR-1224-5p slowed Rankl-induced osteoclast differentiation and promoted osteoblast differentiation via the Rap1-signaling pathway by targeting ADCY2. In addition, in vivo overexpression of miR-1224-5p significantly promoted fracture healing and ameliorated the progression of osteoporosis caused by estrogen deficiency or aging. Furthermore, knockdown of miRNA-1224-5p inhibited bone regeneration in mice and accelerated the progression of osteoporosis in elderly mice. Taken together, these results identify miR-1224-5p as a key bone osteogenic regulator, which may be a potential therapeutic target for osteoporosis and fracture nonunion.Subject terms: Translational research, Cell signalling 相似文献
39.
Watari M Galbraith J Lang HP Sousa M Hegner M Gerber C Horton MA McKendry RA 《Journal of the American Chemical Society》2007,129(3):601-609
Free-standing cantilevers, which directly translate specific biochemical reactions into micromechanical motion, have recently attracted much attention as label-free biosensors and micro/nano robotic devices. To exploit this mechanochemical sensing technology, it is essential to develop a fundamental understanding of the origins of surface stress. Here we report a detailed study into the molecular basis of stress generation in aqueous environments focusing on the pH titration of model mercaptohexadecanoic acid self-assembled monolayers (SAMs), using in situ reference cantilevers coated with nonionizable hexadecanethiol SAMs. Semiautomated data analysis and a statistical model were developed to quantify cyclic deprotonation/protonation reactions on multiple arrays. In-plane force titrations were found to have the sensitivity to detect ionic hydrogen bond formation between protonated and nonprotonated carboxylic acid groups in the proximity of the surface pK1/2, which generated a mean tensile differential surface stress of +1.2 +/- 0.3 mN/m at pH 6.0, corresponding to 1 pN attractive force between two adjacent MHA molecules. Conversely, the magnitude of compressive differential surface stress was found to increase progressively with pH >/= 7.0, reaching a maximum of -14.5 +/- 0.5 mN/m at pH 9.0, attributed to enhanced electrostatic repulsion between deprotonated carboxylic acid groups. However, striking differences were observed in the micromechanical responses to different ionic strength and ion species present in the aqueous environment, highlighting the critical role of counter- and co-ions on surface stress. Our findings provide fundamental insights into the molecular mechanisms of in-plane mechanochemistry, which may be exploited for biosensing and nanoactuation applications. 相似文献
40.
Xu Qing-Feng Lang Jian-Ping Wei Qiao-Hua Chen Zhong-Ning 《Transition Metal Chemistry》2004,29(5):483-487
A novel heterobimetallic sulfide cluster [(
5-C5Me5)WS3Au(dppms)][dppms = bis(diphenylphosphino)methane monosulfide] was prepared by the reaction of [PPh4][(
5-C5Me5)WS3] with AuI and dppm [dppm = bis(diphenylphosphino)methane] in MeCN. The title compound was fully characterized by elemental analysis, i.r., u.v.–vis., 1H-n.m.r. spectra, and by single crystal X-ray crystallography. In the molecular structure, the Au atom is trigonally coordinated by two bridging S atoms of a [(
5-C5Me5)WS3]– anion and a P atom of the dppms molecule. The formation mechanism for this compound is discussed. 相似文献