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991.
Marina Huber-Gedert Dr. Michał Nowakowski Dr. Ahmet Kertmen Dr. Lukas Burkhardt Dr. Natalia Lindner Dr. Roland Schoch Dr. Regine Herbst-Irmer Dr. Adam Neuba Lennart Schmitz Tae-Kyu Choi Dr. Jacek Kubicki Prof. Dr. Wojciech Gawelda Prof. Dr. Matthias Bauer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(38):9905-9918
A new base metal iron-cobalt dyad has been obtained by connection between a heteroleptic tetra-NHC iron(II) photosensitizer combining a 2,6-bis[3-(2,6-diisopropylphenyl)imidazol-2-ylidene]pyridine with 2,6-bis(3-methyl-imidazol-2-ylidene)-4,4′-bipyridine ligand, and a cobaloxime catalyst. This novel iron(II)-cobalt(III) assembly has been extensively characterized by ground- and excited-state methods like X-ray crystallography, X-ray absorption spectroscopy, (spectro-)electrochemistry, and steady-state and time-resolved optical absorption spectroscopy, with a particular focus on the stability of the molecular assembly in solution and determination of the excited-state landscape. NMR and UV/Vis spectroscopy reveal dissociation of the dyad in acetonitrile at concentrations below 1 mM and high photostability. Transient absorption spectroscopy after excitation into the metal-to-ligand charge transfer absorption band suggests a relaxation cascade originating from hot singlet and triplet MLCT states, leading to the population of the 3MLCT state that exhibits the longest lifetime. Finally, decay into the ground state involves a 3MC state. Attachment of cobaloxime to the iron photosensitizer increases the 3MLCT lifetime at the iron centre. Together with the directing effect of the linker, this potentially makes the dyad more active in photocatalytic proton reduction experiments than the analogous two-component system, consisting of the iron photosensitizer and Co(dmgH)2(py)Cl. This work thus sheds new light on the functionality of base metal dyads, which are important for more efficient and sustainable future proton reduction systems. 相似文献
992.
Stefan Dix Paul Golz Jonas R. Schmid Prof. Dr. Sebastian Riedel Prof. Matthew N. Hopkinson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(45):11554-11558
Trifluoromethoxylated (hetero)arenes are of great interest for several disciplines, especially in agro- and medicinal chemistry. Radical C−H trifluoromethoxylation of (hetero)arenes represents an attractive approach to prepare such compounds, but the high cost and low atom economy of existing . OCF3 radical sources make them unsuitable for the large-scale synthesis of trifluoromethoxylated building blocks. Herein, we introduce bis(trifluoromethyl)peroxide (BTMP, CF3OOCF3) as a practical and efficient trifluoromethoxylating reagent that is easily accessible from inexpensive bulk chemicals. Using either visible light photoredox or TEMPO catalysis, trifluoromethoxylated arenes could be prepared in good yields under mild conditions directly from unactivated aromatics. Moreover, TEMPO catalysis allowed for the one-step synthesis of valuable pyridine derivatives, which have been previously prepared via multi-step approaches. 相似文献
993.
Dr. Irán Rojas-León Gelen Gómez-Jaimes Dr. Pedro Montes-Tolentino Prof. Dr. Wolf Hiller Dr. Hazem Alnasr Prof. Dr. Braulio Rodríguez-Molina Dr. Irán F. Hernández-Ahuactzi Prof. Dr. Hiram Beltrán Prof. Dr. Klaus Jurkschat Prof. Dr. Herbert Höpfl 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(48):12276-12283
Hydrolysis reactions of di- and trinuclear organotin halides yielded large novel cage compounds containing Sn−O−Sn bridges. The molecular structures of two octanuclear tetraorganodistannoxanes showing double-ladder motifs, viz., [{Me3SiCH2(Cl)SnCH2YCH2Sn(OH)CH2SiMe3}2(μ-O)2]2 [ 1 , Y=p-(Me)2SiC6H4-C6H4Si(Me)2] and [{Me3SiCH2(I)SnCH2YCH2Sn(OH)CH2SiMe3}2(μ-O)2]2 ⋅ 0.48 I2 [ 2⋅ 0.48 I2, Y=p-(Me)2SiC6H4-C6H4Si(Me)2], and the hexanuclear cage-compound 1,3,6-C6H3(p-C6H4Si(Me)2CH2Sn(R)2OSn(R)2CH2Si(Me)2C6H4-p)3C6H3-1,3,6 ( 3 , R=CH2SiMe3) are reported. Of these, the co-crystal 2⋅ 0.48 I2 exhibits the largest spacing of 16.7 Å reported to date for distannoxane-based double ladders. DFT calculations for the hexanuclear cage and a related octanuclear congener accompany the experimental work. 相似文献
994.
比较峰面积归一化法与标准曲线法两种方法分析植物油中脂肪酸百分比含量的差异。利用气相色谱-质谱联用仪(GC-MS)检测10种市售食用植物油中的8种主要脂肪酸,峰面积归一化法和标准曲线法计算脂肪酸的百分比含量。结果表明,标准曲线法与峰面积归一化法相比,肉豆蔻酸、棕榈酸、十七烷酸、硬脂酸和棕榈油酸所占的百分比升高,而油酸、亚油酸和亚麻酸比例降低;饱和脂肪酸比例升高,不饱和脂肪酸百分比降低。利用峰面积归一化法计算植物油中脂肪酸百分比时,降低了饱和脂肪酸比例,升高了不饱和脂肪酸比例,可能对健康有潜在的不利影响。建议使用标准曲线法计算不同植物油中脂肪酸的百分比。 相似文献
995.
通过水相合成法制备了硫鸟嘌呤(TG)修饰的锰掺杂硫化锌量子点(TG-Mn:ZnS QDs)。加入Pt4+后,Pt4+会与硫鸟嘌呤上的氮原子结合形成N-Pt4+配位结构附着在TG-Mn:ZnS QDs的表面,随着Pt4+浓度的增加,TG-Mn:ZnS QDs-Pt4+体系发生电子转移而导致磷光逐渐被猝灭,基于此构建了检测Pt4+的磷光探针。实验中考察了p H、时间对Pt4+猝灭TG-Mn:ZnS QDs磷光强度的影响。在最佳实验条件下,Pt4+浓度在0.06~2.4μg/mL范围内与TG-Mn:ZnS QDs的磷光强度呈良好的线性关系y=0.0884x+0.2319,R2=0.991,方法检出限(3σ/n)为1.3μg/mL。该磷光探针适用于实际样品中Pt4+含量的测定。 相似文献
996.
固态电池以其高安全性和高能量密度而备受关注。石榴石型固体电解质(LLZO)由于具有较高的离子导电性和对锂金属的稳定性,在固态电池中具有应用前景,但陶瓷与锂金属较差的界面接触会导致高的界面阻抗和可能形成的枝晶穿透。我们利用LLZO表层独特的H+/Li+交换反应,提出了一种简便有效的金属盐类水溶液诱发策略,在电解质表面原位构建ZnO亲锂层,界面处LiZn合金化实现紧密连续的接触。引入改性层后,界面阻抗可显著降低至约10Ω·cm2,对称电池能够在0.1mA·cm-2的电流密度下实现长达1000h的长循环稳定性。匹配正极LiFePO4(LFP)或LiNi0.5Co0.2Mn0.3O2(NCM523)的准固态电池在室温下能够稳定循环100次以上。 相似文献
997.
Daniel Joven-Sancho Dr. Miguel Baya Prof. Dr. Larry R. Falvello Dr. Antonio Martín Dr. Jesús Orduna Dr. Babil Menjón 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(50):12796-12806
The involvement of silver in two-electron AgI/AgIII processes is currently emerging. However, the range of stability of the required and uncommon AgIII species is virtually unknown. Here, the stability of AgIII towards the whole set of halide ligands in the organosilver(III) complex frame [(CF3)3AgX]− (X=F, Cl, Br, I, At) is theoretically analyzed. The results obtained depend on a single factor: the nature of X. Even the softest and least electronegative halides (I and At) are found to form reasonably stable AgIII−X bonds. Our estimates were confirmed by experiment. The whole series of nonradiative halide complexes [PPh4][(CF3)3AgX] (X=F, Cl, Br, I) has been experimentally prepared and all its constituents have been isolated in pure form. The pseudohalides [PPh4][(CF3)3AgCN] and [PPh4][(CF3)3Ag(N3)] have also been isolated, the latter being the first silver(III) azido complex. Except for the iodo compound, all the crystal and molecular structures have been established by single-crystal X-ray diffraction methods. The decomposition paths of the [(CF3)3AgX]− entities at the unimolecular level have been examined in the gas phase by multistage mass spectrometry (MSn). The experimental detection of the two series of mixed complexes [CF3AgX]− and [FAgX]− arising from the corresponding parent species [(CF3)3AgX]− demonstrate that the Ag−X bond is particularly robust. Our experimental observations are rationalized with the aid of theoretical methods. Smooth variation with the electronegativity of X is also observed in the thermolyses of bulk samples. The thermal stability in the solid state gradually decreases from X=F (145 °C, dec.) to X=I (78 °C, dec.) The experimentally established compatibility of AgIII with the heaviest halides is of particular relevance to silver-mediated or silver-catalyzed processes. 相似文献
998.
Grégoire Sieg Quentin Pessemesse Sascha Reith Stefan Yelin Prof. Dr. Christian Limberg Prof. Dr. Dominik Munz Dr. C. Gunnar Werncke 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(67):16760-16767
Carbonyl and iminyl based radical anions are reactive intermediates in a variety of transformations in organic synthesis. Herein, the isolation of ketyl, and more importantly unprecedented ketiminyl and aldiminyl radical anions coordinated to cobalt and iron complexes is presented. Insights into the electronic structure of these unusual metal bound radical anions is provided by X-Ray diffraction analysis, NMR, IR, UV/Vis and Mössbauer spectroscopy, solid and solution state magnetometry, as well as a by a detailed computational analysis. The metal bound radical anions are very reactive and facilitate the activation of intra- and intermolecular C−H bonds. 相似文献
999.
Sebastian Hamer Jan-Simon von Glasenapp Fynn Röhricht Dr. Chao Li Prof. Dr. Richard Berndt Prof. Dr. Rainer Herges 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(69):17452-17458
A set of dipolar molecular rotor compounds was designed, synthesized and adsorbed as self-assembled 2D arrays on Ag(111) surfaces. The title molecules are constructed from three building blocks: (a) 4,8,12-trioxatriangulene (TOTA) platforms that are known to physisorb on metal surfaces such as Au(111) and Ag(111), (b) phenyl groups attached to the central carbon atom that function as pivot joints to reduce the barrier to rotation, (c) pyridine and pyridazine units as small dipolar units on top. Theoretical calculations and scanning tunneling microscopy (STM) investigations hint at the fact that the dipoles of neighboring rotors interact through space through pairs of energetically favorable head-to-tail arrangements. 相似文献
1000.
Avinash Chettri Jan-Hendrik Kruse Keshav Kumar Jha Lara Dröge Dr. Iuliia Romanenko Dr. Christof Neumann Dr. Stephan Kupfer Prof. Dr. Andrey Turchanin Prof. Dr. Sven Rau Prof. Dr. Felix H. Schacher Prof. Dr. Benjamin Dietzek 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(68):17049-17058
Recently, porous photocatalytically active block copolymer membranes were introduced, based on heterogenized molecular catalysts. Here, we report the integration of the photosensitizer, i. e., the light absorbing unit in an intermolecular photocatalytic system into block copolymer membranes in a covalent manner. We study the resulting structure and evaluate the orientational mobility of the photosensitizer as integral part of the photocatalytic system in such membranes. To this end we utilize transient absorption anisotropy, highlighting the temporal reorientation of the transition dipole moment probed in a femtosecond pump-probe experiment. Our findings indicate that the photosensitizer is rigidly bound to the polymer membrane and shows a large heterogeneity of absolute anisotropy values as a function of location probed within the matrix. This reflects the sample inhomogeneity arising from different protonation states of the photosensitizer and different intermolecular interactions of the photosensitizers within the block copolymer membrane scaffold. 相似文献