全文获取类型
收费全文 | 34905篇 |
免费 | 4072篇 |
国内免费 | 3062篇 |
专业分类
化学 | 17040篇 |
晶体学 | 296篇 |
力学 | 1449篇 |
综合类 | 242篇 |
数学 | 2678篇 |
物理学 | 9174篇 |
综合类 | 11160篇 |
出版年
2024年 | 146篇 |
2023年 | 635篇 |
2022年 | 992篇 |
2021年 | 1098篇 |
2020年 | 1111篇 |
2019年 | 946篇 |
2018年 | 830篇 |
2017年 | 799篇 |
2016年 | 1183篇 |
2015年 | 1228篇 |
2014年 | 1586篇 |
2013年 | 1950篇 |
2012年 | 2410篇 |
2011年 | 2421篇 |
2010年 | 1701篇 |
2009年 | 1770篇 |
2008年 | 1962篇 |
2007年 | 1930篇 |
2006年 | 1706篇 |
2005年 | 1464篇 |
2004年 | 1189篇 |
2003年 | 1005篇 |
2002年 | 927篇 |
2001年 | 849篇 |
2000年 | 865篇 |
1999年 | 1227篇 |
1998年 | 996篇 |
1997年 | 1019篇 |
1996年 | 922篇 |
1995年 | 800篇 |
1994年 | 754篇 |
1993年 | 658篇 |
1992年 | 588篇 |
1991年 | 543篇 |
1990年 | 492篇 |
1989年 | 377篇 |
1988年 | 317篇 |
1987年 | 211篇 |
1986年 | 179篇 |
1985年 | 95篇 |
1984年 | 39篇 |
1983年 | 41篇 |
1982年 | 37篇 |
1981年 | 21篇 |
1980年 | 8篇 |
1979年 | 6篇 |
1976年 | 1篇 |
1958年 | 1篇 |
1957年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Dr. Naixia Lv Jie Yin Wendi Fu Jinrui Zhang Yujun Li Dr. Ding Jiang Dr. Hongping Li Prof. Wenshuai Zhu 《Chemphyschem》2021,22(2):168-177
The rational design of highly active hexagonal boron nitride (h-BN) catalysts at the atomic level is urgent for aerobic reactions. Herein, a doping impurity atom strategy is adopted to increase its catalytic activities. A series of doping systems involving O, C impurities and B, N antisites are constructed and their catalytic activities for molecular O2 have been studied by density functional theory (DFT) calculations. It is demonstrated that O2 is highly activated on ON and BN defects, and moderately activated on CB and CN defects, however, it is not stable on NB and OB defects. The subsequent application in oxidative desulfurization (ODS) reactions proves the ON and C-doped (CB, CN) systems to be good choice for sulfocompounds oxidization, especially for dibenzothiophene (DBT). While the BN antisite is not suitable for such aerobic reaction due to the extremely stable B−O*−B species formed during the oxidation process. 相似文献
992.
Mary Marshall Zhaoguo Zhu Rachel Harris Prof. Dr. Kit H. Bowen Wei Wang Jie Wang Chu Gong Prof. Dr. Xinxing Zhang 《Chemphyschem》2021,22(1):5-8
Thorium and its compounds have been widely investigated as important nuclear materials. Previous research focused on the potential use of thorium hydrides, such as ThH2, ThH4, and Th4H15, as nuclear fuels. Here, we report studies of the anion, ThH5−, by anion photoelectron spectroscopy and computations. The resulting experimental and theoretical vertical detachment energies (VDE) for ThH5− are 4.09 eV and 4.11 eV, respectively. These values and the agreement between theory and experiment facilitated the characterization of the structure of the ThH5− anion and showed its neutral counterpart, ThH5 to be a superhalogen. ThH5−, which exhibits a C4v structure with five Th−H single bonds, possesses the largest known H/M ratio among the actinide elements, M. The adaptive natural density partitioning (AdNDP) method was used to further analyze the chemical bonding of ThH5− and to confirm the existence of five Th−H single bonds in the ThH5− molecular anion. 相似文献
993.
Bowen Zhu Kexuan Wang Haili Gao Qinhua Wang Xiaofeng Pan Mizi Fan 《Chemphyschem》2021,22(16):1675-1683
The unique physical structure and abundant surface functional groups of MXene make the grafted organic molecules exhibit specific electrical and optical properties. This work reports the results of first-principles calculations to investigate the composite systems formed by different organic molecular monomers, namely acrylic acid (AA), acrylamide (AM), 1-aziridineethanol (1-AD) and glucose, and Ti3C2 MXene saturated with different functional groups, namely −OH, −O and −F. The results show that the interaction between organic molecules and the MXene surface depends on the type of functional groups of the organic molecules, while the strength of the interaction is determined by the type of surface functional groups and the number of hydrogen bonds. The bare Ti3C2 and Ti3C2(OH)2 can readily form strong chemical and hydrogen bonds with AA and AM molecules, leading to strong adsorption energy and a large amount of charge transfer, while the interaction between organic molecules and MXene saturated by −F or −O groups mainly exhibits physical interactions, accompanied by low adsorption energy and a small amount of charge transfer. This research provides theoretical guidance for the synthesis of high-performance MXene organic composite systems. 相似文献
994.
Thermophoresis of charged spheroids has been widely applied in biology and medical science. In this work, we report an analysis of the anisotropic thermophoresis of diluted spheroidal colloids in aqueous media for extremely thin EDL cases. Under the boundary layer approximation, we formulate the thermophoretic velocity, the thermophoretic force, and the thermodiffusion coefficient of a randomly dispersed spheroid. The parametric studies show that under the aforementioned conditions, the thermophoresis is anisotropic and its thermodiffusion coefficient should be considered as a vector, D T. The thermodiffusion coefficient values and directions of D T are strongly related to the aspect ratio and the angle θ between the externally applied temperature gradient and the particle's axis of revolution: The increasing aspect ratio enlarges the thermodiffusion coefficient value DT of prolate (oblate) spheroids to a constant value when θ < 60° (θ > 45°), and it reduces DT of prolate (oblate) spheroids to a constant value when θ > 60° (θ < 45°). The thermodiffusion coefficient direction of both prolate and oblate spheroids deviates slightly from −∇T∞ for a small aspect ratio, and such deviation becomes serious for a large aspect ratio. 相似文献
995.
Makoto Shimizu Takato Kawamura Shinya Fukumoto Isao Mizota Yusong Zhu 《Journal of heterocyclic chemistry》2021,58(3):751-756
The ketene silyl acetal derived from ethyl 2-benzyltetrahydroisoquinoline-1-carboxylate undergoes a rapid oxidation reaction with N-bromosuccinimide to form 3,4-dihydroisoquinolinium ion, which reacts with Grignard reagents to give 1,1-disubstituted tetrahydroisoquinolines in good yields. 相似文献
996.
Jon Babi Linglan Zhu Angela Lin Azalea Uva Hana El-Haddad Atang Peloewetse Helen Tran 《Journal of polymer science. Part A, Polymer chemistry》2021,59(21):2378-2404
Sequence-defined polymers can be programmed to self-assemble into precise nanostructures for applications in biosensing, drug delivery, optics, and molecular computation. Inspired by the natural self-assembly processes present in biological protein and DNA systems, sets of molecular design rules have emerged across materials classes as instructions to build a variety of tunable structures. This review highlights recent advances in self-assembled sequence-defined and sequence-specific polymers across peptides, peptoids, DNA, and non-biological synthetic materials, with a focus on synthesis, assembly processes and overall structure. Specifically, these self-assembled structures are free-floating, as such constructs can potentially serve as a platform for the aforementioned applications. Emphasis is placed on the molecular design of polymers that self-assemble into zero-dimensional, one-dimensional, two-dimensional, or three-dimensional nanostructures. With the development of automated syntheses and increasing control over self-assembly, future work may focus on emerging classes of compatible hybrid materials with exciting directions toward new architectures and applications. 相似文献
997.
Zhi-Ling Zhu Xiao-Dan Qiu Shuo Wu Yi-Tong Liu Ting Zhao Zhong-Hao Sun Zhuo-Rong Li Guang-Zhi Shan 《Molecules (Basel, Switzerland)》2021,26(1)
The novel coronavirus disease (2019-nCoV) has been affecting global health since the end of 2019, and there is no sign that the epidemic is abating. Targeting the interaction between the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein and the human angiotensin-converting enzyme 2 (ACE2) receptor is a promising therapeutic strategy. In this study, surface plasmon resonance (SPR) was used as the primary method to screen a library of 960 compounds. A compound 02B05 (demethylzeylasteral, CAS number: 107316-88-1) that had high affinities for S-RBD and ACE2 was discovered, and binding affinities (KD, μM) of 02B05-ACE2 and 02B05-S-RBD were 1.736 and 1.039 μM, respectively. The results of a competition experiment showed that 02B05 could effectively block the binding of S-RBD to ACE2 protein. Furthermore, pseudovirus infection assay revealed that 02B05 could inhibit entry of SARS-CoV-2 pseudovirus into 293T cells to a certain extent at nontoxic concentration. The compoundobtained in this study serve as references for the design of drugs which have potential in the treatment of COVID-19 and can thus accelerate the process of developing effective drugs to treat SARS-CoV-2 infections. 相似文献
998.
Xiaoyu Zhao Aonan Zhu Yaxin Wang Yongjun Zhang Xiaolong Zhang 《Molecules (Basel, Switzerland)》2021,26(4)
In the present study, a sunflower-like nanostructure array composed of a series of synaptic nanoparticles and nanospheres was manufactured through an efficient and low-cost colloidal lithography technique. The primary electromagnetic field contribution generated by the synaptic nanoparticles of the surface array structures was also determined by a finite-difference time-domain software to simulate the hotspots. This structure exhibited high repeatability and excellent sensitivity; hence, it was used as a surface-enhanced Raman spectroscopy (SERS) active substrate to achieve a rapid detection of ultra-low concentrations of Alpha-fetoprotein (AFP). This study demonstrates the design of a plasmonic structure with strong electromagnetic coupling, which can be used for the rapid detection of AFP concentration in clinical medicine. 相似文献
999.
Hao Xu Jie Zhu Xiong Wang Chao Shen Shengshen Meng Kai Zheng Chao Lei Longfeng Zhu 《Molecules (Basel, Switzerland)》2021,26(5)
Developing sustainable routes for the synthesis of zeolites is still a vital and challenging task in zeolite scientific community. One of the typical examples is sustainable synthesis of aluminosilicate EU-1 zeolite, which is not very efficient and environmental-unfriendly under hydrothermal condition due to the use of a large amount of water as solvent. Herein, we report a sustainable synthesis route for aluminosilicate EU-1 zeolite without the use of solvent for the first time. The physicochemical properties of the obtained EU-1 zeolite are characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetry-differential thermal analysis (TG-DTA), N2 sorption, inductively coupled plasma (ICP) analysis, and solid nuclear magnetic resonance (NMR), which show the product has high crystallinity, uniform morphology, large BET surface area, and four-coordinated aluminum species. Moreover, the impact of synthesis conditions is investigated in detail. The sustainable synthesis of aluminosilicate EU-1 zeolite under solvent-free 相似文献
1000.
Yiqun Dai Xiaolong Sun Bohan Li Hui Ma Pingping Wu Yingping Zhang Meilin Zhu Hong-Mei Li Minjian Qin Cheng-Zhu Wu 《Molecules (Basel, Switzerland)》2021,26(6)
Nasopharyngeal carcinoma (NPC) is a common malignant head and neck tumor. Drug resistance and distant metastasis are the predominant cause of treatment failure in NPC patients. Hispidulin is a flavonoid extracted from the bioassay-guided separation of the EtOH extract of Salvia plebeia with strong anti-proliferative activity in nasopharyngeal carcinoma cells (CNE-2Z). In this study, the effects of hispidulin on proliferation, invasion, migration, and apoptosis were investigated in CNE-2Z cells. The [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] (MTT) assay and the colony formation assay revealed that hispidulin could inhibit CNE-2Z cell proliferation. Hispidulin (25, 50, 100 μM) also induced apoptosis in a dose-dependent manner in CNE-2Z cells. The expression of Akt was reduced, and the expression of the ratio of Bax/Bcl-2 was increased. In addition, scratch wound and transwell assays proved that hispidulin (6.25, 12.5, 25 μM) could inhibited the migration and invasion in CNE-2Z cells. The expressions of HIF-1α, MMP-9, and MMP-2 were decreased, while the MMPs inhibitor TIMP1 was enhanced by hispidulin. Moreover, hispidulin exhibited potent suppression tumor growth and low toxicity in CNE-2Z cancer-bearing mice at a dosage of 20 mg/kg/day. Thus, hispidulin appears to be a potentially effective agent for NPC treatment. 相似文献