全文获取类型
收费全文 | 30170篇 |
免费 | 5010篇 |
国内免费 | 3409篇 |
专业分类
化学 | 21110篇 |
晶体学 | 399篇 |
力学 | 1917篇 |
综合类 | 281篇 |
数学 | 3381篇 |
物理学 | 11501篇 |
出版年
2024年 | 225篇 |
2023年 | 672篇 |
2022年 | 1080篇 |
2021年 | 1147篇 |
2020年 | 1347篇 |
2019年 | 1196篇 |
2018年 | 1021篇 |
2017年 | 1001篇 |
2016年 | 1441篇 |
2015年 | 1409篇 |
2014年 | 1646篇 |
2013年 | 2149篇 |
2012年 | 2599篇 |
2011年 | 2584篇 |
2010年 | 1799篇 |
2009年 | 1732篇 |
2008年 | 1901篇 |
2007年 | 1716篇 |
2006年 | 1637篇 |
2005年 | 1341篇 |
2004年 | 1083篇 |
2003年 | 868篇 |
2002年 | 782篇 |
2001年 | 630篇 |
2000年 | 613篇 |
1999年 | 686篇 |
1998年 | 528篇 |
1997年 | 473篇 |
1996年 | 475篇 |
1995年 | 421篇 |
1994年 | 369篇 |
1993年 | 354篇 |
1992年 | 293篇 |
1991年 | 246篇 |
1990年 | 247篇 |
1989年 | 171篇 |
1988年 | 140篇 |
1987年 | 92篇 |
1986年 | 114篇 |
1985年 | 83篇 |
1984年 | 52篇 |
1983年 | 49篇 |
1982年 | 56篇 |
1981年 | 27篇 |
1980年 | 15篇 |
1979年 | 17篇 |
1978年 | 8篇 |
1976年 | 8篇 |
1975年 | 7篇 |
1957年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Laihao Ding Guan-Huei Duh Guanghui Wang Tsai-Lien Wong Jianliang Wu Xiaowei Yu Xuding Zhu 《Discrete Mathematics》2019,342(1):279-284
A graph is -choosable if the following holds: For any list assignment which assigns to each vertex a set of real numbers, and assigns to each edge a set of real numbers, there is a total weighting such that for , and for every edge . This paper proves that if is a connected graph of maximum degree , then is -choosable. 相似文献
2.
Chiral cyclic [n]spirobifluorenylenes consisting of helically arranged quaterphenyl rods, illustrating partial units of woven patterns, were designed and synthesized as a new family of carbon nanorings. The synthesis was accomplished by the Ni(0)-mediated Yamamoto-coupling of chiral spirobifluorene building blocks. The structures of the cyclic 3-, 4-, and 5-mers were determined by X-ray crystallographic analysis. These carbon nanorings exhibited a strong violet colored emission with high quantum yields in solution (95%, 93%, and 94% for 3-, 4-, and 5-mer, respectively). Other spectroscopic properties, including their chiroptical properties, were also investigated. The g-values for circularly polarized luminescence were found to be in the order of 10−3. Characteristic spiroconjugation induced by multiple (≧3) bifluorenyl units, for example the even-odd effect of the number of units in the matching of the signs of the orbitals, was also indicated by DFT calculations.Chiral cyclic [n]spirobifluorenylenes consisting of helically arranged quaterphenyl rods, illustrating partial units of woven patterns, were designed and synthesized as a new family of carbon nanorings. 相似文献
3.
Xin Pan Yajie Lu Weixing Zhou Wenyu Zhang Ling Yang Chaoyuan Zhu Sheng-Hsien Lin 《中国化学会会志》2023,70(3):737-746
Since the concept of aggregation-induced emission (AIE) was proposed by Benzhong Tang's research group in 2001, the exploration of the mechanism of AIE and the development of new high-performance AIE materials have been the focus and goal of this field. On the basis of a large number of experiment results, AIE mechanism has been well explained by lots of works, such as restricted intramolecular motion (RIM), J-aggregate et al. As tetraphenylethlene (TPE) molecules are stacked, the rotation of the benzene ring rotor is blocked, and the energy attenuation is released in the form of radiation, showing the AIE effect. In order to further explore the AIE effect of TPE, we performed electronic structure, spectrum simulation, and AIE mechanism calculations of the anthryl-tetraphenylethene (TPE-an) monomer and dimer in the gas phase, tetrahydrofuran (THF), and aqueous solutions at the B3LYP/6-31G** level. The calculation results show that TPE-an molecule is in a propeller-like configuration, and its fluorescence intensity is weak; compared with the monomer, the fluorescence intensity of the dimer increases by 87% in aqueous solution; the fluorescence intensity in the gas phase, THF solution, and aqueous solution gradually enhances with the increase of the degree of aggregation, which are consistent with the experimental results. The enhancement of fluorescence intensity is caused by the change of molecular structure caused by aggregation. This detailed AIE luminescence mechanism will provide theoretical guidance for AIE material design. 相似文献
4.
Wenju Zhu Mingyang Yang Qing Wang Xiaohan Zhang Dongxiang Li Zelong Xu Shuixia Liu Zhao Dai 《中国化学会会志》2023,70(2):159-170
The chelating ligands of boric acid and amino trimethyl phosphonate prepared a novel flame retardant (BAP) for the cotton fabric. A stable chemical and coordination bond was formed on the surface of the cotton fibers by a simple three-curing finishing process to make the fabric exhibits excellent durable flame retardancy. Cotton fabrics' tensile strength and whiteness got substantially retained after BAP treatment. 90 g/L BAP-treated samples (3 curing times, 50 laundry cycles) showed good flame retardancy and durability, holding the largest limit oxygen index, 29.7%, and the shortest damage length, 61 mm. A condensed phase and gas phase synergistic flame retardant mechanism was concluded by thermogravimetric, cone calorimeter tests, and thermogravimetric infrared analysis. 相似文献
5.
Ming Li Dr. Xuanpeng Wang Jisong Hu Jiexin Zhu Prof. Chaojiang Niu Dr. Huazhang Zhang Cong Li Buke Wu Prof. Chunhua Han Prof. Liqiang Mai 《Angewandte Chemie (International ed. in English)》2023,62(8):e202215552
The corrosion, parasitic reactions, and aggravated dendrite growth severely restrict development of aqueous Zn metal batteries. Here, we report a novel strategy to break the hydrogen bond network between water molecules and construct the Zn(TFSI)2-sulfolane-H2O deep eutectic solvents. This strategy cuts off the transfer of protons/hydroxides and inhibits the activity of H2O, as reflected in a much lower freezing point (<−80 °C), a significantly larger electrochemical stable window (>3 V), and suppressed evaporative water from electrolytes. Stable Zn plating/stripping for over 9600 h was obtained. Based on experimental characterizations and theoretical simulations, it has been proved that sulfolane can effectively regulate solvation shell and simultaneously build the multifunctional Zn-electrolyte interface. Moreover, the multi-layer homemade modular cell and 1.32 Ah pouch cell further confirm its prospect for practical application. 相似文献
6.
Dr. Shiyan Chen Lingwei Feng Lixia Peng Xiang Gao Yongfa Zhu Dr. Liulin Yang Prof. Dafa Chen Prof. Kai Zhang Prof. Xugang Guo Prof. Fei Huang Prof. Haiping Xia 《Angewandte Chemie (International ed. in English)》2023,62(32):e202305489
The development of conjugated polymers especially n-type polymer semiconductors is powered by the design and synthesis of electron-deficient building blocks. Herein, a strong acceptor building block with di-metallaaromatic structure was designed and synthesized by connecting two electron-deficient metallaaromatic units through a π-conjugated bridge. Then, a double-monomer polymerization methodology was developed for inserting it into conjugated polymer scaffolds to yield metallopolymers. The isolated well-defined model oligomers indicated polymer structures. Kinetic studies based on nuclear magnetic resonance and ultraviolet–visible spectroscopies shed light on the polymerization process. Interestingly, the resulted metallopolymers with dπ–pπ conjugations are very promising electron transport layer materials which can boost photovoltaic performance of an organic solar cell, with power conversion efficiency up to 18.28 % based on the PM6 : EH-HD-4F non-fullerene system. This work not only provides a facile route to construct metallaaromatic conjugated polymers with various functional groups, but also discovers their potential applications for the first time. 相似文献
7.
Jiaqian Zhou Peiran Xie Chao Wang Tieyuan Bian Dr. Jian Chen Dr. Yang Liu Zhu Guo Congcong Chen Xin Pan Prof. Dr. Min Luo Prof. Dr. Jun Yin Prof. Dr. Lingling Mao 《Angewandte Chemie (International ed. in English)》2023,62(35):e202307646
Double perovskites (DP) have attracted extensive attention due to their rich structures and wide application prospects in the field of optoelectronics. Here, we report 15 new Bi-based double perovskite derived halides with the general formula of A2BBiX6 (A=organic cationic ligand, B=K or Rb, X=Br or I). These materials are synthesized using organic ligands to coordinate with metal ions with a sp3 oxygen, and diverse structure types have been obtained with distinct dimensionalities and connectivity modes. The optical band gaps of these phases can be tuned by changing the halide, the organic ligand and the alkali metal, varying from 2.0 to 2.9 eV. The bromide phases exhibit increasing photoluminescence (PL) intensity with decreasing temperature, while the PL intensity of iodide phases changes nonmonotonically with temperature. Because the majority of these phases are non-centrosymmetric, second harmonic generation (SHG) responses are also measured for selected non-centrosymmetric materials, showing different particle-size-dependent trends. Our findings give rise to a series of new structural types to the DP family, and provide a powerful synthetic handle for symmetry breaking. 相似文献
8.
Dr. Chuanzhao Li Renlong Zhu Zhe Yang Jing Lai Dr. Junjun Tan Prof. Yi Luo Prof. Shuji Ye 《Angewandte Chemie (International ed. in English)》2023,62(7):e202214208
We demonstrate that an ordered 2D perovskite can significantly boost the photoelectric performance of 2D/3D perovskite heterostructures. Using selective fluorination of phenyl-ethyl ammonium (PEA) lead iodide to passivate 3D FA0.8Cs0.2PbI3, we find that the 2D/3D perovskite heterostructures passivated by a higher ordered 2D perovskite have lower Urbach energy, yielding a remarkable increase in photoluminescence (PL) intensity, PL lifetime, charge-carrier mobilities (ϕμ), and carrier diffusion length (LD) for a certain 2D perovskite content. High performance with an ultralong PL lifetime of ≈1.3 μs, high ϕμ of ≈18.56 cm2 V−1 s−1, and long LD of ≈7.85 μm is achieved in the 2D/3D films when passivated by 16.67 % para-fluoro-PEA2PbI4. This carrier diffusion length is comparable to that of some perovskite single crystals (>5 μm). These findings provide key missing information on how the organic cations of 2D perovskites influence the performance of 2D/3D perovskite heterostructures. 相似文献
9.
Wenkai Lin Yu Liu Jinhui Wang Zhennan Zhao Kai Lu He Meng Ruiqi Luoliu Xiaojun He Jianliang Shen Zong-Wan Mao Wei Xia 《Angewandte Chemie (International ed. in English)》2023,62(43):e202310158
Despite metal-based photosensitizers showing great potential in photodynamic therapy for tumor treatment, the application of the photosensitizers is intrinsically limited by their poor cancer-targeting properties. Herein, we reported a metal-based photosensitizer-bacteria hybrid, Ir-HEcN , via covalent labeling of an iridium(III) photosensitizer to the surface of genetically engineered bacteria. Due to its intrinsic self-propelled motility and hypoxia tropism, Ir-HEcN selectively targets and penetrates deeply into tumor tissues. Importantly, Ir-HEcN is capable of inducing pyroptosis and immunogenic cell death of tumor cells under irradiation, thereby remarkably evoking anti-tumor innate and adaptive immune responses in vivo and leading to the regression of solid tumors via combinational photodynamic therapy and immunotherapy. To the best of our knowledge, Ir-HEcN is the first metal complex decorated bacteria for enhanced photodynamic immunotherapy. 相似文献
10.
Jian Chen Lifu Wu Yue Zhao Prof. Shaolin Zhu 《Angewandte Chemie (International ed. in English)》2023,62(44):e202311094
Catalytic methods which control multiple stereogenic centers simultaneously are highly desirable in modern organic synthesis and chemical manufacturing. Herein, we report a regio-, enantio-, and diastereoselective NiH-catalyzed hydroalkylation process which proceeds with simultaneous control of vicinal stereocenters originating from two readily accessible partners, prochiral internal alkenes (enamides or enecarbamates) and racemic alkyl electrophiles (α-bromoamides or Katritzky salts). This reaction produces high-value β-aminoamides and their derivatives under mild conditions and with precise selectivity. Preliminary studies of the mechanism indicate that the reaction involves an enantioselective syn-hydronickelation to generate an enantiomerically enriched alkylnickel(II) species. Subsequent enantioconvergent alkylation with a racemic alkyl electrophile generates the desired product as a single stereoisomer. 相似文献