全文获取类型
收费全文 | 46867篇 |
免费 | 7468篇 |
国内免费 | 5231篇 |
专业分类
化学 | 32938篇 |
晶体学 | 482篇 |
力学 | 2886篇 |
综合类 | 363篇 |
数学 | 5816篇 |
物理学 | 17081篇 |
出版年
2024年 | 35篇 |
2023年 | 881篇 |
2022年 | 939篇 |
2021年 | 1434篇 |
2020年 | 1802篇 |
2019年 | 1687篇 |
2018年 | 1476篇 |
2017年 | 1370篇 |
2016年 | 2061篇 |
2015年 | 2063篇 |
2014年 | 2603篇 |
2013年 | 3335篇 |
2012年 | 4157篇 |
2011年 | 4330篇 |
2010年 | 2985篇 |
2009年 | 2884篇 |
2008年 | 3134篇 |
2007年 | 2769篇 |
2006年 | 2601篇 |
2005年 | 2096篇 |
2004年 | 1722篇 |
2003年 | 1322篇 |
2002年 | 1209篇 |
2001年 | 1027篇 |
2000年 | 930篇 |
1999年 | 1002篇 |
1998年 | 842篇 |
1997年 | 772篇 |
1996年 | 858篇 |
1995年 | 757篇 |
1994年 | 651篇 |
1993年 | 562篇 |
1992年 | 524篇 |
1991年 | 436篇 |
1990年 | 384篇 |
1989年 | 298篇 |
1988年 | 252篇 |
1987年 | 232篇 |
1986年 | 172篇 |
1985年 | 179篇 |
1984年 | 153篇 |
1983年 | 135篇 |
1982年 | 94篇 |
1981年 | 68篇 |
1980年 | 54篇 |
1979年 | 36篇 |
1978年 | 28篇 |
1976年 | 28篇 |
1975年 | 32篇 |
1974年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
61.
格雷码辅助相移技术可以实现具有较强鲁棒性与抗噪能力的三维(3D)形貌测量。为解决由待测物体不均匀的表面反射率、噪声和物体运动等因素造成的级次边沿误码问题,提出了一种基于错位格雷码的动态3D形貌测量方法。将传统格雷码图案在投影前预先移动半个条纹周期得到错位格雷码图案,再采用传统格雷码解码方法对二值化后的错位格雷码图案解码,可得到与截断相位完全错开的解码结果。对该解码结果进行修正后即可利用得到的正确的相位级次辅助截断相位成功展开。同时,为了提高测量精度,引入了一个虚拟相位平面以进一步拓展投影条纹周期数。实验结果表明,所提方法在使用N帧格雷码图案的情况下,可以编码周期数为2N+1的投影条纹进行3D测量,其无需任何附加图案即可避免级次边沿误码问题,并有效提升了测量精度。复杂动态场景的3D重建结果证明,所提方法能够以2381 frame/s的速率实现高精度、高效率和高速的3D形貌测量。 相似文献
62.
Wu Yitian Zhang Xiaojun Zhou Haoxi Zhang Jinming 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(6):2705-2717
Journal of Radioanalytical and Nuclear Chemistry - Prostate-specific membrane antigen (PSMA)-targeted radiolabeled agents have been developed to diagnose and treat prostate cancer. In this study,... 相似文献
63.
Hussain Imtiaz Ma Xiaofeng Wu Linlin Luo Zhenyang 《Cellulose (London, England)》2022,29(10):5725-5743
Cellulose - Self-healing hydrogels that mimic human skin and have numerous senses of external tension and temperature are a current topic in science. However, getting skin-compatible performance... 相似文献
64.
Xuan Zhang Xianhe Fang Miao Xu Yibo Lei Zibo Wu Xiangdong Hu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(23):7927-7931
Enantioselective total syntheses of pseudopteroxazole ( 1 ) and ileabethoxazole ( 2 ) are presented. The two original stereocenters were constructed in excellent enantioselectivity and good diastereoselectivity through Carreira's asymmetric dual catalytic allylation, which shows potential for accessing diastereoisomers at C2 and C3 of 1 and 2 . Cationic cyclizations of 13 and 24 demonstrated an effective pathway for the construction of the opposite configurations at C1 in 1 and 2 . Additionally, an approach for the introduction of methyl at C4 is a feasible solution for structural modifications at C4 in 1 and 2 . 相似文献
65.
Fang Chen Hongwei Huang Lin Guo Yihe Zhang Tianyi Ma 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(30):10164-10176
Semiconductor photocatalysis as a desirable technology shows great potential in environmental remediation and renewable energy generation, but its efficiency is severely restricted by the rapid recombination of charge carriers in the bulk phase and on the surface of photocatalysts. Polarization has emerged as one of the most effective strategies for addressing the above‐mentioned issues, thus effectively promoting photocatalysis. This review summarizes the recent advances on improvements of photocatalytic activity by polarization‐promoted bulk and surface charge separation. Highlighted is the recent progress in charge separation advanced by different types of polarization, such as macroscopic polarization, piezoelectric polarization, ferroelectric polarization, and surface polarization, and the related mechanisms. Finally, the strategies and challenges for polarization enhancement to further enhance charge separation and photocatalysis are discussed. 相似文献
66.
Cu‐doped Ni‐based metal–organic frameworks (MOFs) nanomaterials fabricated through a one‐pot hydrothermal reaction were characterized, and their performance as supercapacitor electrode materials was further studied for the first time. The results indicated that the doping of foreign metals and the introduction of K3[Fe(CN)6] in the KOH electrolyte significantly improve the performance of the supercapacitor. The results indicated that the Ni2.6Cu0.4 MOFs material shows the highest specific capacitance (1282 F g?1 at 1 A g?1 in mixed 2 M KOH and 0.1 M K3[Fe(CN)6]) and optimal capacitance retention (85.7% after 2000 cycles). This work provides a feasible optimization strategy for the construction of MOFs‐based supercapacitor electrode materials with excellent performance, and also provides a reliable experimental and theoretical basis for practical industrial production. 相似文献
67.
Blossoms of Inula nervosa Wall. (BINW) are traditionally used as an analgesic and antitussive in China. In this study, in vitro anticomplementary activities of crude extract from BINW in 21 batches and of extracts of four monomeric compounds were evaluated by the classical pathway. The effect of the region of origin on the quality of BINW was evaluated by fingerprint analysis for the first time. Furthermore, chemometric methods including similarity analysis and principal component analysis were employed to evaluate the quality of BINW. The nine major monomeric compounds were quantitated by ultra‐high‐performance liquid chromatography. All nine analytes demonstrated excellent linearity with recoveries ranging from 97.25% to 102.76%. The limits of detection and quantification were 0.07–12.20 μg/mL and 0.22–40.27 μg/mL, respectively. Results indicate that different regions of origin have a significant effect on the quality of BINW. Fingerprint analysis in combination with chemometrics and multi‐ingredient determination is an efficient and reliable approach for quality evaluation. The BINW samples from Yunnan had the highest ratio of 1,5‐dicaffeoylquinic acid and thymol; they also exhibited significantly higher anticomplementary activity than those from three other areas. This study successfully established a rapid and efficient method to evaluate the quality and biological activity of BINW. 相似文献
68.
Wei Wang Dr. Parthasarathi Subramanian Oscar Martinazzoli Jun Wu Prof. Dr. Lutz Ackermann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(45):10585-10589
Late-stage C−H glycosylations of structurally complex amino acids and peptides were accomplished by means of racemization-free manganese(I)-catalyzed C−H activation. Thus, glycosylative modifications proved to be viable by a linch-pin approach, featuring chemo- and site-selective C−H transformations. The peptide–saccharide conjugation provided modular access to structurally complex glycopeptides, likewise enabling the assembly of fluorescent-labelled glycopeptides. 相似文献
69.
Potapenko Anna V. Wu Mengqiang Kirillov Sviatoslav A. 《Journal of Solid State Electrochemistry》2019,23(12):3383-3389
Journal of Solid State Electrochemistry - Lithium-manganese-rich–lithiated nickel-manganese-cobalt oxides are advantageous for using in lithium-ion batteries due to low toxicity and high... 相似文献
70.
Jiangyu Wu Meimei Feng Guansheng Han Benyu Yao Xiaoyan Ni 《Comptes Rendus Mecanique》2019,347(1):62-89
Investigating the dilatancy, acoustic emission and failure characteristics of fissured rock are significant to ensure their geotechnical stability. In this paper, the uniaxial and triaxial compression experiments with AE monitoring under different loading rates were carried out on fissured rock specimens with the same geometrical distribution of two pre-existing flaws. The dilatancy and AE activity of these specimens were discussed, and the effects of the confining pressure and loading rate on the mechanical parameters and failure characteristics were analyzed. The results show that the exponential strength criterion is more suitable than the Mohr–Coulomb strength criterion to characterize the strength characteristics of fissured rock. The crack evolution and failure characteristics of fissured rock specimens are more complicated than those of intact rock specimens. The failure characteristics of the fissured rock follow the tensile shear coalescence model, crack branching occurs with increasing the loading rate, and the multi-section coalescence model is verified with increasing the confining pressure. The phenomena of stress drop and yield platform usually occur after the dilatancy onset, the specimen does not fail instantaneously, and the propagation and coalescence of cracks cause a sharp increase in the AE signals, circumferential strain, and volumetric strain. 相似文献