全文获取类型
收费全文 | 943篇 |
免费 | 12篇 |
国内免费 | 2篇 |
专业分类
化学 | 512篇 |
晶体学 | 28篇 |
力学 | 60篇 |
数学 | 94篇 |
物理学 | 263篇 |
出版年
2022年 | 7篇 |
2021年 | 11篇 |
2020年 | 11篇 |
2019年 | 11篇 |
2018年 | 6篇 |
2016年 | 12篇 |
2014年 | 13篇 |
2013年 | 35篇 |
2012年 | 34篇 |
2011年 | 38篇 |
2010年 | 25篇 |
2009年 | 11篇 |
2008年 | 42篇 |
2007年 | 48篇 |
2006年 | 44篇 |
2005年 | 59篇 |
2004年 | 52篇 |
2003年 | 32篇 |
2002年 | 31篇 |
2001年 | 27篇 |
2000年 | 16篇 |
1998年 | 8篇 |
1996年 | 16篇 |
1995年 | 9篇 |
1994年 | 14篇 |
1993年 | 9篇 |
1992年 | 20篇 |
1991年 | 14篇 |
1990年 | 18篇 |
1989年 | 13篇 |
1988年 | 13篇 |
1987年 | 11篇 |
1986年 | 15篇 |
1985年 | 20篇 |
1984年 | 14篇 |
1983年 | 13篇 |
1982年 | 8篇 |
1981年 | 19篇 |
1980年 | 9篇 |
1979年 | 9篇 |
1978年 | 9篇 |
1977年 | 9篇 |
1976年 | 6篇 |
1975年 | 9篇 |
1974年 | 15篇 |
1973年 | 10篇 |
1971年 | 7篇 |
1970年 | 7篇 |
1969年 | 8篇 |
1967年 | 6篇 |
排序方式: 共有957条查询结果,搜索用时 78 毫秒
951.
Prediction and observation of isostructurality induced by solvent incorporation in multicomponent crystals 总被引:1,自引:0,他引:1
Cruz Cabeza AJ Day GM Motherwell WD Jones W 《Journal of the American Chemical Society》2006,128(45):14466-14467
The crystal structures of two pharmaceutical molecules-carbamazepine and its 10,11-dihydro derivative-with acetic acid have been successfully predicted by computational methods. While the crystalline structure of the former was known a priori, no structural information was available for the latter. Possible crystal structures were generated in silico before any experimental work was performed. Although the crystal structures of the pure drug molecules are very different, incorporation of acetic acid in their crystal lattices results in isomorphic products. 相似文献
952.
The effect of dopant cesium (Cs(I)) over a concentration range from 1 to 10 mol% on the growth process, morphology, thermal and optical properties of tri(thiourea)zinc(II) sulfate (ZTS) single crystals grown by slow evaporation solution growth technique has been investigated. Incorporation of Cs(I) into the crystal lattice was well confirmed by energy dispersive X-ray spectroscopy (EDS). The lattice parameters of the as-grown crystals were obtained by single crystal X-ray diffraction analysis. The reduction in the intensities observed in powder X-ray diffraction patterns of doped specimen and slight shifts in vibrational frequencies in fourier transform infrared spectra (FT-IR) indicate the lattice stress as a result of doping. Thermal studies reveal the purity of the material and no decomposition is observed up to the melting point. High transmittance is observed in the visible region and the cut-off λ is ~280 nm. The surface morphology of the as-grown specimens was studied by scanning electron microscopy (SEM). The second harmonic generation (SHG) efficiency of the host crystal is enhanced greatly in the presence of high concentrations of the dopant. 相似文献
953.
A general theory of economic change, development and policy is presented based on bounded rationality, adaptive economizing in disequilibrium and creative intelligence. The latter perturbs the economic system as in the Schumpeterian theory but is here regarded as a fundamental faculty that both underlies the exercise of rationality and makes possible the imitation of new behavior that is at the basis of socio-economic transformation. Moreover, it generates the institutional innovations that insure continued viability in a globally unstable world. 相似文献
954.
Daniel M. Day Thomas J. Farmer Joe Granelli Janice H. Lofthouse Julie Lynch Con R. McElroy James Sherwood Seishi Shimizu James H. Clark 《Molecules (Basel, Switzerland)》2022,27(23)
Green chemistry places an emphasis on safer chemicals, waste reduction, and efficiency. Processes should be optimized with green chemistry at the forefront of decision making, embedded into research at the earliest stage. To assist in this endeavor, we present a spreadsheet that can be used to interpret reaction kinetics via Variable Time Normalization Analysis (VTNA), understand solvent effects with linear solvation energy relationships (LSER), and calculate solvent greenness. With this information, new reaction conditions can be explored in silico, calculating product conversions and green chemistry metrics prior to experiments. The application of this tool was validated with literature case studies. Reaction performance was predicted and then confirmed experimentally for examples of aza-Michael addition, Michael addition, and an amidation. The combined analytical package presented herein permits a thorough examination of chemical reactions, so that the variables that control reaction chemistry can be understood, optimized, and made greener for research and education purposes. 相似文献
955.
Fei Cong Riccardo S. Mega Jinhong Chen Craig S. Day Prof. Ruben Martin 《Angewandte Chemie (International ed. in English)》2023,62(15):e202214633
Herein, we report a Cu-mediated trifluoromethylation of carbonyl-type compounds and unactivated olefins enabled by visible-light irradiation via σ C(sp3)−C bond-functionalization. The reaction is distinguished by its modularity, mild conditions and wide scope—even in the context of late-stage functionalization—thus offering a complementary approach en route to valuable C(sp3)−CF3 architectures from easily accessible precursors. 相似文献
956.
Dr. Tian Luo Dr. Zi Wang Yinlin Chen Dr. Hengzhao Li Mengqi Peng Dr. Floriana Tuna Prof. Eric J. L. McInnes Dr. Sarah J. Day Prof. Jie An Prof. Martin Schröder Prof. Sihai Yang 《Angewandte Chemie (International ed. in English)》2023,62(48):e202306267
Deuterium labelling of organic compounds is an important process in chemistry. We report the first example of photocatalytic dehalogenative deuteration of both arylhalides and alkylhalides (40 substrates) over a metal–organic framework, MFM-300(Cr), using CD3CN as the deuterium source at room temperature. MFM-300(Cr) catalyses high deuterium incorporation and shows excellent tolerance to various functional groups. Synchrotron X-ray powder diffraction reveals the activation of halogenated substrates via confined binding within MFM-300(Cr). In situ electron paramagnetic resonance spectroscopy confirms the formation of carbon-based radicals as intermediates and reveals the reaction pathway. This protocol removes the use of precious-metal catalysts from state-of-the-art processes based upon direct hydrogen isotope exchange and shows high photocatalytic stability, thus enabling multiple catalytic cycles. 相似文献
957.