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671.
Patil VS Padalkar VS Phatangare KR Gupta VD Umape PG Sekar N 《The journal of physical chemistry. A》2012,116(1):536-545
ESIPT-inspired benzimidazolyl substituted fluorescein dyes were synthesized. PH-sensitivity was determined by the photophysical property measured at a physiological possible pH range. Fluorescence quantum efficiency values were calculated independently at two different emissions. A rational relationship is defined between fluorescence quantum efficiency and calculated HOMO energy. 相似文献
672.
Wendy Zhong Jiong Yang Bruce D. Hilton Gary E. Martin Jianguo Yin Kiran Muppalla Weidong Tong Xiaoyong Fu 《Journal of heterocyclic chemistry》2012,49(5):1163-1168
A highly colored impurity formed at low levels during the preparation of 3‐amino N,N‐dimethyl salicylamide was isolated and identified as 2‐amino‐N,N,N′,N′‐tetramethyl‐3‐oxo‐3H‐phenoxazin‐4,6‐dicarboxamide using mass spectrometry and two‐dimensional NMR methods that included long‐range 1H‐15N heteronuclear chemical shift correlation data to assemble the proton‐deficient “right‐half” of the 2‐aminophenoxazin‐3‐one nucleus. The structure was independently confirmed using computer‐assisted structure elucidation methods and by synthesis. 相似文献
673.
Gore KR Nawale GN Harikrishna S Chittoor VG Pandey SK Höbartner C Patankar S Pradeepkumar PI 《The Journal of organic chemistry》2012,77(7):3233-3245
The linear syntheses of 4'-C-aminomethyl-2'-O-methyl uridine and cytidine nucleoside phosphoramidites were achieved using glucose as the starting material. The modified RNA building blocks were incorporated into small interfering RNAs (siRNAs) by employing solid phase RNA synthesis. Thermal melting studies showed that the modified siRNA duplexes exhibited slightly lower T(m) (~1 °C/modification) compared to the unmodified duplex. Molecular dynamics simulations revealed that the 4'-C-aminomethyl-2'-O-methyl modified nucleotides adopt South-type conformation in a siRNA duplex, thereby altering the stacking and hydrogen-bonding interactions. These modified siRNAs were also evaluated for their gene silencing efficiency in HeLa cells using a luciferase-based reporter assay. The results indicate that the modifications are well tolerated in various positions of the passenger strand and at the 3' end of the guide strand but are less tolerated in the seed region of the guide strand. The modified siRNAs exhibited prolonged stability in human serum compared to unmodified siRNA. This work has implications for the use of 4'-C-aminomethyl-2'-O-methyl modified nucleotides to overcome some of the challenges associated with the therapeutic utilities of siRNAs. 相似文献
674.
G. Sreevidya Varma M.S.R.N. Kiran D.V.S. Muthu U. Ramamurty A.K. Sood S. Asokan 《Journal of Non》2012,358(23):3103-3108
Nanoindentation studies on Ge15Te85 ? xInx glasses indicate that the hardness and elastic modulus of these glasses increase with indium concentration. While a pronounced plateau is seen in the elastic modulus in the composition range 3 ≤ x ≤ 7, the hardness exhibits a change in slope at compositions x = 3 and x = 7. Also, the density exhibits a broad maximum in this composition range. The observed changes in the mechanical properties and density are clearly associated with the thermally reversing window in Ge15Te85 ? xInx glasses in the composition range 3 ≤ x ≤ 7. In addition, a local minimum is seen in density and hardness around x = 9, the chemical threshold of the system. Further, micro-Raman studies reveal that as-quenched Ge15Te85 ? xInx samples exhibit two prominent peaks, at 123 cm? 1 and 155 cm? 1. In thermally annealed samples, the peaks at 120 cm? 1 and 140 cm? 1, which are due to crystalline Te, emerge as the strongest peaks. The Raman spectra of polished samples are similar to those of annealed samples, with strong peaks at 123 cm? 1 and 141 cm? 1. The spectra of lightly polished samples outside the thermally reversing window resemble those of thermally annealed samples; however, the spectra of glasses with compositions in the thermally reversing window resemble those of as-quenched samples. This observation confirms the earlier idea that compositions in the thermally reversing window are non-aging and are more stable. 相似文献
675.
Metal-center-driven spontaneous resolution of a chiral coordination polymer, [Ni(SDB)(BIX)](n) (1), from achiral precursors has been probed by single-crystal X-ray diffraction and circular dichroism spectroscopy. Enantiomorphs 1P and 1M showed a parallel interpenetrated 2D → 3D chiral framework with (8(2).10) topology. Switching of the metal center under the same reaction parameters resulted in isostructural achiral and noninterpenetrating (4,4) grid-type sql networks [M(SDB)(BIX)](n), where M = Co(II), Zn(II), and Cd(II) for 2-4, respectively. 相似文献
676.
Kumar MK Prabhakar S Kumar MR Vairamani M 《Rapid communications in mass spectrometry : RCM》2006,20(6):1045-1048
677.
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679.
Rajendra Singh Dhayal Kiran Kumar Varma Chakrahari V. Ramkumar Sundargopal Ghosh 《Journal of Cluster Science》2009,20(3):565-572
Abstract Reaction of [(η5-C5Me5Mo)2B5H9], 1 with 5-fold excess of n-BuLi at −70 °C followed by excess of RI (R = n-Bu or Ph) at room temperature yielded B-R inserted metallaboranes [(η5-C5Me5Mo)2B5H8R] (2: R = n-Bu, 5: R = Ph), [(η5-C5Me5Mo)2B5H7R2] (3, 4: R = n-Bu; 6, 7: R = Ph). Isolated yields of mono-alkyl/arylated species are better than di-alkyl/arylated ones. All the new cluster compounds have been characterized by IR, 1H, 11B, 13C NMR and mass spectroscopy as simple substitution derivatives of [(η5-C5Me5Mo)2B5H9] and the structural types of one of these species, 2 was established by X-ray crystallographic analysis.
Graphical Abstract Reaction of [(η5-C5Me5Mo)2B5H9], with 5-fold excess of n-BuLi at −70 °C followed by excess of RI (R = n-Bu or Ph) at room temperature yielded B-R inserted metallaboranes [(η5-C5Me5Mo)2B5H9-nRn] (When R = n-Bu, n = 2, 1; R = Ph, n = 2, 1).
相似文献
680.
Tatapudi Kiran Kumar Bandi Siva Ajay Anand Komati Anusha Satish Mohabe Araveeti Madhusudana Reddy Franoise Le Devehat Ashok Kumar Tiwari Joël Boustie Katragadda Suresh Babu 《Molecules (Basel, Switzerland)》2022,27(19)
In this study, we propose ultra-performance liquid chromatography coupled with quadrupole/time-of-flight mass spectrometry (UPLC-QToF-MS/MS)-guided metabolite isolation as a choice analytical approach to the ongoing structure–activity investigations of chemical isolates from the edible lichen, Ramalina conduplicans Vain. This strategy led to the isolation and identification of a new depside (5) along with 13 known compounds (1–4, 6–14), most of which being newly described in this lichen species. The structures of the isolates were established by detailed analysis of their spectral data (IR, NMR, and Mass). The acetone extract was further analyzed by UPLC-Q-ToF-MS/MS in a negative ionization mode, which facilitated the identification and confirmation of 18 compounds based on their fragmentation patterns. The antioxidant capacities of the lichen acetone extract (AE) and isolates were measured by tracking DPPH and ABTS free radical scavenging activities. Most isolates displayed marked radical scavenging activities against ABTS while moderate activities were observed against DPPH radical scavenging. Except for atranol (14), oxidative DNA damage was limited by all the tested compounds, with a marked protection for the novel isolated compound (5), as previously noted for the acetone extract (p < 0.001). Furthermore, compound (4) and acetone extract (AE) have inhibited intestinal α-glucosidase enzyme significantly (p < 0.01). Although some phytochemical studies were already performed on this lichen, this study provided new insights into the isolation and identification of bioactive compounds, illustrating interest in future novel analytical techniques. 相似文献