全文获取类型
收费全文 | 40409篇 |
免费 | 396篇 |
国内免费 | 164篇 |
专业分类
化学 | 17981篇 |
晶体学 | 679篇 |
力学 | 1614篇 |
综合类 | 2篇 |
数学 | 3571篇 |
物理学 | 13146篇 |
无线电 | 3976篇 |
出版年
2022年 | 304篇 |
2021年 | 359篇 |
2020年 | 334篇 |
2019年 | 342篇 |
2018年 | 556篇 |
2017年 | 470篇 |
2016年 | 769篇 |
2015年 | 428篇 |
2014年 | 778篇 |
2013年 | 1685篇 |
2012年 | 1573篇 |
2011年 | 1924篇 |
2010年 | 1456篇 |
2009年 | 1539篇 |
2008年 | 1713篇 |
2007年 | 1826篇 |
2006年 | 1627篇 |
2005年 | 1371篇 |
2004年 | 1314篇 |
2003年 | 1137篇 |
2002年 | 1093篇 |
2001年 | 1496篇 |
2000年 | 1120篇 |
1999年 | 935篇 |
1998年 | 709篇 |
1997年 | 688篇 |
1996年 | 605篇 |
1995年 | 563篇 |
1994年 | 530篇 |
1993年 | 519篇 |
1992年 | 559篇 |
1991年 | 556篇 |
1990年 | 532篇 |
1989年 | 476篇 |
1988年 | 482篇 |
1987年 | 452篇 |
1986年 | 395篇 |
1985年 | 456篇 |
1984年 | 490篇 |
1983年 | 355篇 |
1982年 | 392篇 |
1981年 | 385篇 |
1980年 | 335篇 |
1979年 | 408篇 |
1978年 | 382篇 |
1977年 | 409篇 |
1976年 | 401篇 |
1975年 | 349篇 |
1974年 | 330篇 |
1973年 | 343篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Cancer is a global issue and a serious threat to human health, one approach to treatment is starvation therapy. Recently, three-dimensional (3D) bioprinted tumor tissue models have been developed; however, whether 3D bioprinted models are good for in vitro study of starvation therapy is unclear. In this study, we studied the state of cells with serum-free medium in both 3D bioprinted scaffold and 2D cell cultures and found that 3D bioprinted cancer cells (3D cells) were more tolerant to serum starvation than 2D cells in terms of cell viability, cell proliferation, and M2 macrophage polarization. Moreover, the ratio of LC3II/I, an index of autophagy, increased much more in 3D cells, and 3D cells showed more autophagosomes than 2D cells after serum starvation, which indicated that the autophagy levels were higher in 3D cells. These results suggested that 3D cells are more tolerant to serum starvation than 2D cells, and autophagy may play an important role in this process. 相似文献
992.
Cycloparaphenylene (CPP) shows modulated photophysical and electronic properties due to its strained structure and radially oriented π-electron system. Incorporation of CPP into metal-organic frameworks (MOFs) could transfer its extensive properties in solution to porous solids. Moreover, with the unique arrangement of the macrocycles and their interactions with the framework, emerging characteristics are anticipated. As an example of “robust dynamics”, we synthesized the first MOF structure (FDM-1001) with CPP precisely anchored to the ordered framework by employing a [8]CPP-containing linear dicarboxylate linker. Metric relationship between the dynamic macrocycles and the robust backbone creates ideal π-π interactions between them, which leads to an essentially directional arrangement of [8]CPP in the three-dimensional space. Furthermore, the MOF with [8]CPP could be successfully oxidized to generate an infinite array of radicals that show enhanced air stability compared to its molecular analogue. 相似文献
993.
Janovszky Dora Sveda Maria Sycheva Anna Kristaly Ferenc Zámborszky Ferenc Koziel Tomasz Bala Piotr Czel Gyorgy Kaptay George 《Journal of Thermal Analysis and Calorimetry》2022,147(13):7141-7157
Journal of Thermal Analysis and Calorimetry - A remarkable number of scientific papers are available in the literature about the bulk amorphous alloys and metallic glasses. Today, DSC is an... 相似文献
994.
High Energy Chemistry - Modification of Polyvinylidene fluoride (PVDF) by radiation grafting is a research hotspot in recent years. In this study, the monomer 2-Hydroxyethyl methacrylate (HEMA) was... 相似文献
995.
Chuprin A. S. Belova S. A. Bugaenko M. G. Vologzhanina A. V. Loktev A. S. Voloshin Ya. Z. Buznik V. M. Dedov A. G. 《Kinetics and Catalysis》2022,63(1):108-116
Kinetics and Catalysis - A new ruthenium(II) cage complex with polar terminal groups in the apical substituents has been synthesized; the molecular design of the complex contributes to the... 相似文献
996.
Temerdashev Z. A. Musorina T. N. Ovsepyan S. K. Korpakova I. G. 《Journal of Analytical Chemistry》2022,77(5):595-603
Journal of Analytical Chemistry - The work is dedicated to the determination of polyaromatic hydrocarbons (PAHs) in soils and bottom sediments by gas chromatography–mass spectrometry using... 相似文献
997.
Dr. Michael Peter Mercer Sam Affleck Dr. Edgardo Maximiliano Gavilán-Arriazu Dr. Alana Aragón Zülke Dr. Philip A. Maughan Shivam Trivedi Prof. Maximilian Fichtner Dr. Anji Reddy Munnangi Prof. Ezequiel P. M. Leiva Prof. Harry Ernst Hoster 《Chemphyschem》2022,23(5):e202100748
Sodium-ion batteries (NIBs) utilize cheaper materials than lithium-ion batteries (LIBs) and can thus be used in larger scale applications. The preferred anode material is hard carbon, because sodium cannot be inserted into graphite. We apply experimental entropy profiling (EP), where the cell temperature is changed under open circuit conditions. EP has been used to characterize LIBs; here, we demonstrate the first application of EP to any NIB material. The voltage versus sodiation fraction curves (voltage profiles) of hard carbon lack clear features, consisting only of a slope and a plateau, making it difficult to clarify the structural features of hard carbon that could optimize cell performance. We find additional features through EP that are masked in the voltage profiles. We fit lattice gas models of hard carbon sodiation to experimental EP and system enthalpy, obtaining: 1. a theoretical maximum capacity, 2. interlayer versus pore filled sodium with state of charge. 相似文献
998.
Pascal Rusch Denis Pluta Dr. Franziska Lübkemann Dr. Dirk Dorfs Dr. Dániel Zámbó Prof. Nadja C. Bigall 《Chemphyschem》2022,23(2):e202100755
Employing nanocrystals (NCs) as building blocks of porous aerogel network structures allows the conversion of NC materials into macroscopic solid structures while conserving their unique nanoscopic properties. Understanding the interplay of the network formation and its influence on these properties like size-dependent emission is a key to apply techniques for the fabrication of novel nanocrystal aerogels. In this work, CdSe/CdS dot/rod NCs possessing two different CdSe core sizes were synthesized and converted into porous aerogel network structures. Temperature-dependent steady-state and time-resolved photoluminescence measurements were performed to expand the understanding of the optical and electronic properties of these network structures generated from these two different building blocks and correlate their optical with the structural properties. These investigations reveal the influence of network formation and aerogel production on the network-forming nanocrystals. Based on the two investigated NC building blocks and their aerogel networks, mixed network structures with various ratios of the two building blocks were produced and likewise optically characterized. Since the different building blocks show diverse optical response, this technique presents a straightforward way to color-tune the resulting networks simply by choosing the building block ratio in connection with their quantum yield. 相似文献
999.
Amir Mahgoub Awadelkareem Eyad Al-Shammari Abd Elmoneim O. Elkhalifa Mohd Adnan Arif Jamal Siddiqui Mejdi Snoussi Mohammad Idreesh Khan Z R Azaz Ahmad Azad Mitesh Patel Syed Amir Ashraf 《Molecules (Basel, Switzerland)》2022,27(4)
Eruca sativa Mill. (E. sativa) leaves recently grabbed the attention of scientific communities around the world due to its potent bioactivity. Therefore, the present study investigates the metabolite profiling of the ethanolic crude extract of E. sativa leaves using high resolution-liquid chromatography-mass spectrometry (HR-LC/MS), including antibacterial, antioxidant and anticancer potential against human colorectal carcinoma cell lines. In addition, computer-aided analysis was performed for determining the pharmacokinetic properties and toxicity prediction of the identified compounds. Our results show that E. sativa contains several bioactive compounds, such as vitamins, fatty acids, alkaloids, flavonoids, terpenoids and phenols. Furthermore, the antibacterial assay of E. sativa extract showed inhibitory effects of the tested pathogenic bacterial strains. Moreover, the antioxidant activity of 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydrogen peroxide (H2O2) were found to be IC50 = 66.16 μg/mL and 76.05 μg/mL, respectively. E. sativa also showed promising anticancer activity against both the colorectal cancer cells HCT-116 (IC50 = 64.91 μg/mL) and Caco-2 (IC50 = 83.98 μg/mL) in a dose/time dependent manner. The phytoconstituents identified showed promising pharmacokinetics properties, representing a valuable source for drug or nutraceutical development. These investigations will lead to the further exploration as well as development of E. sativa-based nutraceutical products. 相似文献
1000.
Olha Dzydzan Iryna Brodyak Paulina Strugaa-Danak Angelika Strach Alicja Z. Kucharska Janina Gabrielska Natalia Sybirna 《Molecules (Basel, Switzerland)》2022,27(7)
Although extracts are broadly used in order to support the treatment of numerous diseases, only in a limited number of cases is the process of applying and establishing their mechanisms of action scientifically analyzed. Fruits of Cornelian cherry are an abundant source of iridoids, anthocyanins, flavonols and phenolic acids. The aim of the present study was to evaluate the in vitro bioactivity of red and yellow Cornelian cherry fruits’ extracts. The biological potential of extracts, in a broad sense, involved antioxidant activity in relation to phosphatidylcholine liposomes, inhibitory ability against α-glucosidase and acetylcholinesterase enzymes, as well as interactions with human serum albumin. Studies showed that both extracts were more effective in protecting liposome membranes against free radicals produced by AAPH in an aqueous environment due to the fact that they can be better eliminated by the hydrophilic components of the extracts than those produced by UVB radiation. Extracts exhibited inhibitory activity against acetylcholinesterase and α-glucosidase, wherein loganic acid extract showed noncompetitive inhibition of the enzyme. Moreover, extracts binded to albumin mainly through hydrogen bonds and van der Waals forces. Taken together, red and yellow cherry fruits’ extracts exhibit diverse biological properties and can be exploited as a source of natural therapeutic agents. 相似文献