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941.
The different excited-state behaviors involved in excited-state proton transfer (ESPT) process of a series of 2-(2-hydroxyphenyl)benzoxazole (HBO) derivatives have been theoretically investigated. The primary bond lengths and bond angles were analyzed. Coupling with the infrared (IR) vibrational spectra, we confirmed that the intramolecular hydrogen bond O–H···N should be strengthened in the S1 state, which might provide the possibility for ESPT reaction, whereas introducing the fused rings may weaken the hydrogen bond in excited state. By investigating the vertical excitation process, the charge redistribution was explored. It is found that the electron-accepting –NO2 and –COOH would facilitate the ESPT reaction. With adding fused rings to HBO, less charge transfer exists in the transition process, which can reasonably explain the weakening hydrogen bond phenomenon in excited states. Via constructing the potential energy curves of both S0 and S1 states, we further confirm that electron-accepting substitutions could promote the ESPT process for HBO systems. And fused rings do inhibit ESPT reaction to a great extent. We believe this work not only elaborates the different excited-state proton transfer behaviors for a series of HBO derivatives but also presents a new harnessing ESPT process through substitutional effects. 相似文献
942.
Guixia Zhai Changting Wei Shulian Chen Xiaomeng Yin Jinchong Xiao Wenming Su 《中国化学快报》2018,29(2):293-296
The single crystal analysis of the as-prepared 8,16-dimesityltetraceno[2,1,12,11-opqra]tetracene (DMTA) suggests that the parent bistetracene backbone is almost in a plane without any intermolecular p-stacking interaction. The fabricated devices based on DMTA as an emitter exhibit a maximum brightness of 632 cd/m2 at 14.7 V with the CIE coordinate of (0.623, 0.349). 相似文献
943.
Dan‐Dan Zhai Xiang‐Yu Zhang Yu‐Feng Liu Lei Zheng Prof. Dr. Bing‐Tao Guan 《Angewandte Chemie (International ed. in English)》2018,57(6):1650-1653
The benzylic functionalization of alkylpyridines is an important pathway for pyridine derivatives synthesis. The reaction partners, however, were mostly limited to highly reactive polar electrophiles. Herein, we report a potassium amide‐catalyzed selective benzylic C?H bond addition of alkylpyridines to styrenes. Potassium bis(trimethylsilyl)amide (KHMDS), a readily available Brønsted base, showed excellent catalytic activity and chemoselectivity. A series of alkylpyridine derivatives, including benzylic quaternary carbon substituted pyridines, were obtained in good to high yield. Preliminary mechanistic studies revealed that the deprotonation equilibrium is probably responsible for the excellent selectivity. 相似文献
944.
绿色化学是新兴的学科交叉领域,了解其知识体系的发展及研究态势,有助于讨论当代学科的发展特点。本文选取该领域的权威期刊《绿色化学》(Green Chemistry)作为研究对象,运用Cite Space与VOSviewer等可视化工具对1999~2016年该刊载文进行了计量分析。研究表明,《绿色化学》自创刊以来,其影响因子与载文量快速增长,学术研究进展较快。目前,该领域的核心地区、机构、研究人员集中在美国、中国、英国、德国、荷兰等国家,国际合作十分频繁。绿色化学领域的研究热点包括离子液体、生物质、催化等主题。 相似文献
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Oh HB Lin C Hwang HY Zhai H Breuker K Zabrouskov V Carpenter BK McLafferty FW 《Journal of the American Chemical Society》2005,127(11):4076-4083
Previous gas-phase methods for infrared photodissociation spectroscopy (IRPD) require sample volatility. Our method instead uses electrospray ionization to introduce even large nonvolatile molecules into a Fourier transform mass spectrometer, where extended (>15 s) ion storage makes possible high sensitivity spectral measurements with an OPO laser over a range of 3050-3800 cm(-1). The spectra of 22 gaseous proton-bound amino acid complexes are generally correlated with the H-stretching frequencies established for O-H and N-H functional groups in solution. For theoretical structure predictions of the Gly2H+ and N-acylated Asp2H+ dimers, IRPD spectra clearly differentiate between the predicted lowest energy conformers. In contrast to solution, in the gas phase the glycine zwitterion is approximately 20 kcal/mol less stable than the neutral; however, glycine is clearly zwitterionic in the gaseous GlyLysH+ dimer. The level of theory is inadequate for the larger Lys2H+ dimer, as all low energy predicted structures have free carboxyl O-H groups, in contrast to the IR spectrum. IRPD appears to be a promising new technique for providing unique information on a broad range of biomolecular and other gaseous ions, especially on noncovalent bonding involving O-H and N-H groups. 相似文献
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950.
Lv Jia-Liang Zhai Shang-Ru Wang Zhen-Zhen Lei Zhi-Min An Qing-Da 《Research on Chemical Intermediates》2016,42(2):839-854
Research on Chemical Intermediates - There is a growing trend to employ agricultural waste/by-products (AWBs) as substrates for the development of dye bio-sorbents, and surface modification plays a... 相似文献