全文获取类型
收费全文 | 31081篇 |
免费 | 5581篇 |
国内免费 | 3267篇 |
专业分类
化学 | 21984篇 |
晶体学 | 351篇 |
力学 | 1809篇 |
综合类 | 138篇 |
数学 | 2989篇 |
物理学 | 12658篇 |
出版年
2024年 | 135篇 |
2023年 | 692篇 |
2022年 | 1207篇 |
2021年 | 1376篇 |
2020年 | 1395篇 |
2019年 | 1374篇 |
2018年 | 1166篇 |
2017年 | 1049篇 |
2016年 | 1593篇 |
2015年 | 1515篇 |
2014年 | 1946篇 |
2013年 | 2394篇 |
2012年 | 2858篇 |
2011年 | 2868篇 |
2010年 | 1868篇 |
2009年 | 1781篇 |
2008年 | 1992篇 |
2007年 | 1736篇 |
2006年 | 1626篇 |
2005年 | 1282篇 |
2004年 | 979篇 |
2003年 | 766篇 |
2002年 | 756篇 |
2001年 | 589篇 |
2000年 | 468篇 |
1999年 | 596篇 |
1998年 | 512篇 |
1997年 | 504篇 |
1996年 | 496篇 |
1995年 | 427篇 |
1994年 | 343篇 |
1993年 | 281篇 |
1992年 | 281篇 |
1991年 | 226篇 |
1990年 | 202篇 |
1989年 | 153篇 |
1988年 | 92篇 |
1987年 | 79篇 |
1986年 | 104篇 |
1985年 | 73篇 |
1984年 | 37篇 |
1983年 | 44篇 |
1982年 | 28篇 |
1981年 | 22篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1957年 | 4篇 |
1923年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
191.
Hui Shao Xiaonan Gao Zhong‐Tian Wang Ziwei Gao Yu‐Ming Zhao 《Angewandte Chemie (International ed. in English)》2020,59(19):7419-7424
A divergent synthetic approach to six Ganoderma meroterpenoids, namely ganocins A–C, ganocochlearins C and D, and cochlearol T, has been developed for the first time. This synthetic route features a two‐phase strategy which includes early‐stage rapid construction of a common planar tricyclic intermediate followed by highly selective late‐stage transformations into various Ganoderma meroterpenoids. Key to the strategy are a bioinspired intramolecular hetero‐Diels–Alder reaction and Stahl‐type oxidative aromatization, allowing efficient formation of the common tricyclic phenol intermediate. A nucleophilic dearomatization of the phenol unit, combined with a regioselective 1,4‐reduction of the resulting dienone, enabled rapid access to ganocins B and C. Additionally, site‐selective Mukaiyama hydration, followed by an intramolecular oxa‐Michael addition/triflation cascade, served as a key strategic element in the chemical synthesis of ganocin A. 相似文献
192.
Qian Yi Han Haoyue Li Long Qiao Peng Zhao Rongmin Zhang Haiming 《Journal of Thermal Analysis and Calorimetry》2020,142(1):409-423
Journal of Thermal Analysis and Calorimetry - Layered yttrium hydroxides (LYH)- and graphene oxide (GO)-supported layered yttrium hydroxides (GO–LYH) were synthesized by a co-precipitation... 相似文献
193.
Yuan Haifeng Zhao Yan Yang Chan Zhang Cheng Yang Yue Meng Hongmin Huan Shuangyan Song Guosheng Zhang Xiaobing 《中国科学:化学(英文版)》2020,63(7):924-935
For chemotherapy, drug delivery systems often suffer from the inefficient drug loading capability, which usually cause systems toxicity and extra burden to excrete carrier itself. Moreover, the cancer therapeutic efficacy is also greatly limited by the specificity of tumor microenvironment for reactive oxygen species(ROS) based cancer therapeutic strategy(e.g., chemodynamic therapy). Herein, we have developed metal-drug coordination nanoplatform that can not only be responsive to tumor microenvironment but also modulate it, so as to achieve efficient treatment of cancer. Excitingly, by employing small molecule drug(6-thioguanine) as ligand copper ions, we achieve a high drug loading rate(60.1%) and 100% of utilization of metal-drug coordination nanoplatform(Cu-TG). Interestingly, Cu-TG possessed high-efficiently horseradish peroxidase-like, glutathione peroxidase-like and catalase-like activity. Under the tumor microenvironment, Cu-TG exhibited the self-reinforcing circular catalysis that is able to amplify the cellular oxidative stress, inducing notable cancer cellular apoptosis. Moreover, Cu-TG could be activated with glutathione(GSH) and facilitated for GSH triggered 6-TG release, higher selective therapeutic effect toward cancer cells, and GSH activated T_1 weight-magnetic resonance imaging. Based on the above properties, Cu-TG exhibited magnetic resonance imaging(MRI) guiding, efficient and synergistic combination of chemodynamic and chemotherapy with self-reinforcing therapeutic outcomes in vivo. 相似文献
194.
RNA-cleaving DNAzymes possess important roles in DNAzymes and have been widely used in the biosensors,DNA nanomachines owing to their ion-specific dependence.However,there are still challenges in constructing universal but versatile stimuli-responsive strategies of RNA-cleaving DNAzymes.Herein,a stimuli-responsive strategy for RNA-cleaving DNAzyme is proposed by the artful design of hairpin nanostructure,in which the activities of DNAzyme(Pb~(2+) -dependent DNAzyme as a model) in the hairpin's loop are p H-regulated by using the triplex stem as the "lock".Upon introducing the "key",p H values,the DNAzyme will be activated and fragment the substrate of it in the presence of Pb~(2+),accompanied by the turn-on of the fluorescence quenched by fluorescence resonance energy transfer(FRET).The regulation ability of p H can be controlled by the length and sequence of the triplex stem,and the wide p H regulation range may be helpful for the application of DNAzymes in biological medicine delivery systems. 相似文献
195.
Fu Cen-Feng Zhao Chuanyu Zheng Qijing Li Xingxing Zhao Jin Yang Jinlong 《中国科学:化学(英文版)》2020,63(8):1134-1141
The covalent triazine framework CTF-1 as a member of the two-dimensional covalent organic frameworks(COFs) is a category of novel metal-free photocatalysts for water splitting. The large band gap severely restricts its energy conversion efficiency. By means of the first-principles calculations, we proposed the decoration of CTF-1 by anchoring halogen atoms onto benzene moieties for improving the solar-to-hydrogen(STH) efficiency. The electronic structures reveal that the halogen substitution successfully decreases the band gap of CTF-1. Meanwhile, the calculated free energy changes along the reaction pathway indicate that all these COFs can spontaneously drive overall water splitting under light irradiation in a specific acid-base environment. The time-dependent ab initio non-adiabatic molecular dynamics simulations suggest that the electron-hole recombination periods of these COFs fall in a few to tens of nanoseconds. Excitingly, CTF-1 modified by linking six iodine atoms onto the benzene ring in the para-position(CTF-1-6I) shows a quite low band gap of 2.81 eV, indicating that it is a visible-light driven COF for overall photocatalytic water splitting. Correspondingly, CTF-1-6I also exhibits an extraordinarily promising STH efficiency of 3.70%, which is an order magnitude higher than that of the pristine CTF-1. 相似文献
196.
Fluid Dynamics - Both numerical methods and wind tunnel tests were used to reduce skin friction for a hypersonic body. A hypersonic cone was tested under three different free-stream flow... 相似文献
197.
Feng Zhanxia Chang Zongyu Deng Chao Zhao Lin Chen Jia Zhang Jiakun Zheng Zhongqiang 《Nonlinear dynamics》2022,108(3):2007-2022
Nonlinear Dynamics - Wave glider is an unmanned surface vehicle that can directly convert wave energy into forward propulsion and fulfill long-term marine monitoring. A previous study suggested... 相似文献
198.
Ruohan Xu Dongfeng Dang Zhi Wang Yu Zhou Yanzi Xu Yizhen Zhao Xiaochi Wang Zhiwei Yang Lingjie Meng 《Chemical science》2022,13(5):1270
Organic nanocrystals (NCs) with high brightness are highly desirable for biological imaging. However, the preparation of NCs by a facile and fast method is still challenging. Herein, an aggregation-induced emission (AIE) luminogen of 4,4′-(5,6-difluorobenzo[c][1,2,5]thiadiazole-4,7-diyl)bis(N,N-bis(4-methoxyphenyl)aniline) (DTPA-BT-F) in the deep-red region is designed with intensive crystalline features to obtain NCs by kinetically controlled nanoprecipitation. The prepared AIE NCs with high brightness and good photo-stability are then applied in super-resolution imaging via stimulated emission depletion (STED) nanoscopy. As observed, the nanostructures in lysosomes of both fixed and live cells are well visualized with superior lateral resolutions under STED nanoscopy (full width at half maximum values, 107 and 108 nm) in contrast to that in confocal imaging (548 and 740 nm). More importantly, dynamic monitoring and long-term tracking of lysosomal movements in live HeLa cells, such as lysosomal contact, can also be carried out by using DTPA-BT-F NCs at a superior resolution. To the best of our knowledge, this is the first case of AIE NCs prepared by nanoprecipitation for STED nanoscopy, thus providing a new strategy to develop high performance imaging agents for super-resolution imaging.AIE nanocrystals with high brightness in the deep-red region were facilely prepared by kinetically controlled nanoprecipitation. These nanocrystals were then applied in super-resolution cellular imaging via STED nanoscopy. 相似文献
199.
Fei Zhao Xiaosong Zhai Xuemei Liu Meng Lian Guoting Liang Jingxiang Cui Haizhou Dong Wentao Wang 《Molecules (Basel, Switzerland)》2022,27(1)
The purpose of this paper was to investigate the effect of high-intensity ultrasonication (HIU) pretreatment before enzymolysis on structural conformations of walnut protein isolate (WPI) and antioxidant activity of its hydrolysates. Aqueous WPI suspensions were subjected to ultrasonic processing at different power levels (600–2000 W) and times (5–30 min), and then changes in the particle size, zeta (ζ) potential, and structure of WPI were investigated, and antioxidant activity of its hydrolysates was determined. The particle size of the particles of aqueous WPI suspensions was decreased after ultrasound, indicating that sonication destroyed protein aggregates. The ζ-potential values of a protein solution significantly changed after sonication, demonstrating that the original dense structure of the protein was destroyed. Fourier transform infrared spectroscopy indicated a change in the secondary structure of WPI after sonication, with a decrease in β-turn and an increase in α-helix, β-sheet, and random coil content. Two absorption peaks of WPI were generated, and the fluorescence emission intensity of the proteins decreased after ultrasonic treatment, indicating that the changes in protein tertiary structure occurred. Moreover, the degree of hydrolysis and the antioxidant activity of the WPI hydrolysates increased after sonication. These results suggest that HIU pretreatment is a potential tool for improving the functional properties of walnut proteins. 相似文献
200.
Yi Ding Yan Wu Ying Tian Yuzeng Xu Minna Hou Bo Zhou Jingshan Luo Guofu Hou Ying Zhao Xiaodan Zhang 《Journal of Energy Chemistry》2021,(7):48-54
Guanidinium (GA) cations are intentionally introduced in MAPbl3 perovskite by considering its potential capability of stabilizing the material through plenty of... 相似文献