全文获取类型
收费全文 | 86290篇 |
免费 | 1970篇 |
国内免费 | 1356篇 |
专业分类
化学 | 29792篇 |
晶体学 | 871篇 |
力学 | 7402篇 |
综合类 | 66篇 |
数学 | 32996篇 |
物理学 | 18489篇 |
出版年
2023年 | 183篇 |
2022年 | 306篇 |
2021年 | 349篇 |
2020年 | 351篇 |
2019年 | 329篇 |
2018年 | 10662篇 |
2017年 | 10474篇 |
2016年 | 6449篇 |
2015年 | 1256篇 |
2014年 | 757篇 |
2013年 | 946篇 |
2012年 | 4501篇 |
2011年 | 11252篇 |
2010年 | 6146篇 |
2009年 | 6534篇 |
2008年 | 7149篇 |
2007年 | 9181篇 |
2006年 | 727篇 |
2005年 | 1662篇 |
2004年 | 1829篇 |
2003年 | 2205篇 |
2002年 | 1242篇 |
2001年 | 457篇 |
2000年 | 482篇 |
1999年 | 348篇 |
1998年 | 370篇 |
1997年 | 316篇 |
1996年 | 362篇 |
1995年 | 251篇 |
1994年 | 195篇 |
1993年 | 204篇 |
1992年 | 144篇 |
1991年 | 132篇 |
1990年 | 125篇 |
1989年 | 119篇 |
1988年 | 104篇 |
1987年 | 92篇 |
1986年 | 92篇 |
1985年 | 68篇 |
1984年 | 60篇 |
1983年 | 50篇 |
1982年 | 57篇 |
1981年 | 42篇 |
1980年 | 53篇 |
1979年 | 46篇 |
1914年 | 45篇 |
1913年 | 40篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Under the solvo-thermal conditions, two novel CdII mixed-ligand coordination materials with 2,6-(1,2,4-triazole-4-yl)pyridine(L1) and aromatic poly-carboxylic acid co-ligands such as 5-R-isophthalic acid (R = nitro, sulfo), namely [Cd(L1)(NO2-BDC)(H2O)2] · 2H2O ( 1 ) and [Cd(L1)(HSIP)(H2O)] · 4H2O ( 2 ) (NO2-H2BDC = 5-nitroisophthalic acid, H3SIP = 5-sulfobenzene -isophthalic acid) were successfully prepared. These CdII mixed-ligand coordination polymers 1 – 2 have been measured by crystal X-ray analysis, FT-IR spectra and powder X-ray diffraction analyses. In 1 , these seven-coordinate CdII atoms (Cd1) are inter-linked by didentate 5-nitroisophthalic acid ligands forming 1D chain structures. In 2 , these L1 and partially de-pronated HSIP2– are inter-linked by central CdII centers and are arranged into the unique 2D micro-porous metal-organic framework of 2 . Side view of 2 , it is noted that numerous oxygen atoms of un-coordinated carboxylate groups and coordinated SO3 groups protrude out and decorate the 2D framework of 2 . PXRD patterns of 1 and 2 sample is tested, which is consistent with the simulated PXRD diffraction pattern. Photoluminescence studies show that 2 is highly selective and sensitive to trace elements of Eu3+ with excellent Ksv value (7.86 × 104 m –1) and low detection limit (5.56 × 10–2 mM), which also provides a convenient method and platform for real-time detection of Eu3+. 相似文献
992.
Meng Ding Juanjuan Zhou Hongcen Yang Ruya Cao Shouwei Zhang Minghui Shao Xijin Xu 《中国化学快报》2020,31(1):71-76
Graphene-like C3N4/Ag3PO4 photocatalysts are synthesized by calcination and solutions precipitating method.The obtained g-C3N4/Ag3PO4 composites display excellent photocatalytic activity for the degradation of methylene orange(MO),rhodamine B(RhB)and tetracycline(TC)under visible light irradiation.The solutions containing RhB(10 mg/L)and MO(10 mg/L)can be efficiently degraded within15 min and 30 min.Especially,nearly 80%of TC(50 mg/L)is degraded within 20 min.which are much better than those of pure g-C3N4 nanosheets and Ag3PO4,implying that strong interaction and reasonable energy band alignment in the contact interface can effectively transfer the carries.Furthermore,the g-C3N4/Ag3PO4 composites exhibit the improved stability,and only a slight decrease is observed after three recycling runs.Moreover,the impact of inorganic ions and PH values on the degradation performance is rather small.The Z-scheme photocatalytic mechanism of the g-C3N4/Ag3PO4 composites based on the active species trapping experimental is proposed.This work demonstrates the promising applications of the g-C3N4/Ag3PO4 composites in environmental issues. 相似文献
993.
Yanbin Shen Yahao Li Shengjue Deng Guoxiang Pan Qinqin Xiong Xiaokun Ding Yangfan Lu Qi Liu Xinhui Xia Xiuli Wang Jiangping Tu 《中国化学快报》2020,31(3):846-850
High-perfo rmance anodes of sodium ion batteries(SIBs)largely depends on rational architecture design and binder-free smart hybridization.Herein,we report TiC/C core/shell nanowires arrays prepared by a one-step chemical vapor deposition(CVD)method and apply it as the anode of SIBs for the first time.The conductive TiC core is intimately decorated with carbon shell.The as-obtained TiC/C nanowires are homogeneously grown on the substrate and show core/shell heterostructure and porous architecture with high electronic conductivity and reinforced stability.Owing to these merits,the TiC/C electrode displays good rate performance and outstanding cycling performance with a capacity of 135.3 mAh/g at 0.1 A/g and superior capacity retention of 90.14%after 1000 cycles at 2 A/g.The reported strategy would provide a promising way to construct binder-free arrays electrodes for sodium ion storage. 相似文献
994.
中学阶段常用于检验二氧化硫气体的品红溶液分为酸性品红和碱性品红2种。通过设计集演示、对比于一体的绿色环保二氧化硫性质实验装置,优化实验条件,探讨了酸性品红和碱性品红与SO2、酸碱反应的性质差异及褪色机理,并提出鉴别酸性品红和碱性品红的简便办法。 相似文献
995.
Jiancheng Rao Xinrui Liu Xuefei Li Liuqing Yang Lei Zhao Shumeng Wang Junqiao Ding Lixiang Wang 《Angewandte Chemie (International ed. in English)》2020,59(3):1320-1326
Based on a “TADF + Linker” strategy (TADF=thermally activated delayed fluorescence), demonstrated here is the successful construction of conjugated polymers that allow highly efficient delayed fluorescence. Small molecular TADF blocks are linked together using a methyl‐substituted phenylene linker to form polymers. With the growing number of methyl groups on the phenylene, the energy level of the local excited triplet state (3LEb) from the delocalized polymer backbone gradually increases, and finally surpasses the charge‐transfer triplet state (3CT). As a result, the diminished delayed fluorescence can be recovered for the tetramethyl phenylene containing polymer, revealing a record‐high external quantum efficiency (EQE) of 23.5 % (68.8 cd A?1, 60.0 lm W?1) and Commission Internationale de l′Eclairage (CIE) coordinates of (0.25, 0.52). Combined with an orange‐red TADF emitter, a bright white electroluminescence is also obtained with a peak EQE of 20.9 % (61.1 cd A?1, 56.4 lm W?1) and CIE coordinates of (0.36, 0.51). 相似文献
996.
Weidong Nie Guanghao Wu Jinfeng Zhang Li‐Li Huang Jingjing Ding Anqi Jiang Yahui Zhang Yanhong Liu Jingchao Li Kanyi Pu Hai‐Yan Xie 《Angewandte Chemie (International ed. in English)》2020,59(5):2018-2022
Exosomes hold great potential in therapeutic development. However, native exosomes usually induce insufficient effects in vivo and simply act as drug delivery vehicles. Herein, we synthesize responsive exosome nano‐bioconjugates for cancer therapy. Azide‐modified exosomes derived from M1 macrophages are conjugated with dibenzocyclooctyne‐modified antibodies of CD47 and SIRPα (aCD47 and aSIRPα) through pH‐sensitive linkers. After systemic administration, the nano‐bioconjugates can actively target tumors through the specific recognition between aCD47 and CD47 on the tumor cell surface. In the acidic tumor microenvironment, the benzoic‐imine bonds of the nano‐bioconjugates are cleaved to release aSIRPα and aCD47 that can, respectively, block SIRPα on macrophages and CD47, leading to abolished “don't eat me” signaling and improved phagocytosis of macrophages. Meanwhile, the native M1 exosomes effectively reprogram the macrophages from pro‐tumoral M2 to anti‐tumoral M1. 相似文献
997.
Zhennan Wu Qiaofeng Yao Osburg Jin Huang Chai Nan Ding Wen Xu Shuangquan Zang Jianping Xie 《Angewandte Chemie (International ed. in English)》2020,59(25):9934-9939
Aggregation‐induced emission (AIE) provides an efficient strategy to synthesize highly luminescent metal nanoclusters (NCs), however, rational control of emission energy and intensity of metal NCs is still challenging. This communication reveals the impact of surface AuI‐thiolate motifs on the AIE properties of Au NCs, by employing a series of water‐soluble glutathione (GSH)‐coordinated Au complexes and NCs as a model ([Au10SR10], [Au15SR13], [Au18SR14], and [Au25SR18]?, SR=thiolate ligand). Spectroscopic investigations show that the emission wavelength of Au NCs is adjustable from visible to the near‐infrared II (NIR‐II) region by controlling the length of the AuI‐SR motifs on the NC surface. Decreasing the length of AuI‐SR motifs also changes the origin of cluster luminescence from AIE‐type phosphorescence to Au0‐core‐dictated fluorescence. This effect becomes more prominent when the degree of aggregation of Au NCs increases in solution. 相似文献
998.
Wenjuan Ji Xinjian Ji Qi Zhang Dhanaraju Mandalapu Zixin Deng Wei Ding Peng Sun Qi Zhang 《Angewandte Chemie (International ed. in English)》2020,59(23):8880-8884
Sulfur‐based homolytic substitution (SH reaction) plays an important role in synthetic chemistry, yet whether such a reaction could occur on the positively charged sulfonium compounds remains unknown. In the study of the anaerobic coproporphyrinogen III oxidase HemN, a radical S‐adenosyl‐l ‐methionine (SAM) enzyme involved in heme biosynthesis, we observed the production of di‐(5′‐deoxyadenosyl)methylsulfonium, which supports a deoxyadenosyl (dAdo) radical‐mediated SH reaction on the sulfonium center of SAM. The sulfonium‐based SH reactions were then investigated in detail by density functional theory calculations and model reactions, which showed that this type of reactions is thermodynamically favorable and kinetically competent. These findings represent the first report of sulfonium‐based SH reactions, which could be useful in synthetic chemistry. Our study also demonstrates the remarkable catalytic promiscuity of the radical SAM superfamily enzymes. 相似文献
999.
Shijie Ding Lingyu Kong Yanjuan Jin Jinbao Lin Chao Chang Huaying Li Erqiang Liu Haitao Liu 《先进技术聚合物》2020,31(4):873-884
Fused deposition molding (FDM) is one of the most widely used three‐dimensional (3D) printing technologies. This paper explores the influence of the forming angle on the tensile properties of FDM specimens. Orthogonal layering details were studied through experiments, theory, and finite element simulations. The stiffness and strength of the specimens were analyzed using the classical laminated plate theory and the Tsai–Wu failure criterion. The experimental process was simulated using finite element simulations. Results show that it is feasible to predict the stiffness and strength of FDM specimens using classical laminated plate theory and the Tsai–Wu failure criterion. A molding angle of 45° leads to specimens with maximized tensile properties. Numerical simulations show that changing the molding angle changes the internal stress and deformation fields inside samples, leading to FDM samples with different mechanical properties due to the orthogonal layers at different molding angles. 相似文献
1000.
Lei Jiang Haizhen Ding Siyu Lu Ting Geng Guanjun Xiao Bo Zou Hong Bi 《Angewandte Chemie (International ed. in English)》2020,59(25):9986-9991
Photoactivation in CdSe/ZnS quantum dots (QDs) on UV/Vis light exposure improves photoluminescence (PL) and photostability. However, it was not observed in fluorescent carbon quantum dots (CDs). Now, photoactivated fluorescence enhancement in fluorine and nitrogen co‐doped carbon dots (F,N‐doped CDs) is presented. At 1.0 atm, the fluorescence intensity of F,N‐doped CDs increases with UV light irradiation (5 s–30 min), accompanied with a blue‐shift of the fluorescence emission from 586 nm to 550 nm. F,N‐doped CDs exhibit photoactivated fluorescence enhancement when exposed to UV under high pressure (0.1 GPa). F,N‐doped CDs show reversible piezochromic behavior while applying increasing pressure (1.0 atm to 9.98 GPa), showing a pressure‐triggered aggregation‐induced emission in the range 1.0 atm–0.65 GPa. The photoactivated CDs with piezochromic fluorescence enhancement broadens the versatility of CDs from ambient to high‐pressure conditions and enhances their anti‐photobleaching. 相似文献