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排序方式: 共有159条查询结果,搜索用时 15 毫秒
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2.
A total internal reflection (TIR)-based biochip utilizing a polymer-filled cavity with a micromirror sidewall has been designed and fabricated. The implementation of the micromirror sidewall cavity facilitates precise alignment of the excitation light beam into the system. The incident angle of illumination can be easily modified by selecting polymers of different indices of refraction while optical losses are minimized. The design enables the hybrid, vertical integration of a laser diode and a CCD camera, resulting in a compact optical system. Brownian motion of fluorescent microspheres and real-time photobleaching of rhodamine 6G molecules is demonstrated. The proposed TIR-based chip simplifies current TIR optical configurations and could potentially be used as an optical-microfluidic platform for an integrated lab-on-a-chip microsystem. 相似文献
3.
Georgia‐Paraskevi Nikoleli Muhammad Q. Israr Nikolaos Tzamtzis Dimitrios P. Nikolelis Magnus Willander Nikolas Psaroudakis 《Electroanalysis》2012,24(6):1285-1295
The present article describes a miniaturized potentiometric urea lipid film based biosensor on graphene nanosheets. Structural characterization of graphene nanosheets for miniaturization of potentiometric urea lipid film based biosensors have been studied through atomic force microscopy (AFM) and transmission electron microscopy (TEM) measurements. UV‐Vis and Fourrier transform IR (FTIR) spectroscopy have been utilized to study the pre‐ and postconjugated surfaces of graphene nanosheets. The presented potentiometric urea biosensor exhibits good reproducibility, reusability, selectivity, rapid response times (~4 s), long shelf life and high sensitivity of ca. 70 mV/decade over the urea logarithmic concentration range from 1×10?6 M to 1×10?3 M. 相似文献
4.
Anastasia Liakakou Apostolis Angelis Dimitrios P. Papachristos Nikolas Fokialakis Antonios Michaelakis Leandros A. Skaltsounis 《Molecules (Basel, Switzerland)》2021,26(11)
The present work describes the use of Centrifugal Partition Chromatography (CPC) for the bio-guided isolation of repellent active volatile compounds from essential oils. Five essential oils (EOs) obtained from three Pinus and two Juniperus species were initially analyzed by gas chromatography–mass spectrometry (GC/MS) and evaluated for their repellent properties against Aedes albopictus. The essential oil from needles of P. pinea (PPI) presented the higher activity, showing 82.4% repellency at a dose of 0.2 μL/cm2. The above EO, together with the EO from the fruits of J. oxycedrus subsp. deltoides (JOX), were further analyzed by CPC using the biphasic system n-Heptane/ACN/BuOH in ratio 1.6/1.6/0.2 (v/v/v). The analysis of PPI essential oil resulted in the recovery of (−)-limonene, guaiol and simple mixtures of (−)-limonene/β-pheladrene, while the fractionation of JOX EO led to the recovery of β-myrcene, germacrene-D, and mixtures of α-pinene/β-pinene (ratio 70/30) and α-pinene/germacrene D (ratio 65/45). All isolated compounds and recovered mixtures were tested for their repellent activity. From them, (−)-limonene, guaiol, germacrene-D as well the mixtures of (−)-limonene/β-pheladrene presented significant repellent activity (>97% repellency) against Ae. albopictus. The present methodology could be a valuable tool in the effort to develop potent mosquito repellents which are environmentally friendly. 相似文献
5.
Rhodium(I)‐Catalyzed Decarbonylative Spirocyclization through CC Bond Cleavage of Benzocyclobutenones: An Efficient Approach to Functionalized Spirocycles 下载免费PDF全文
Dr. Tao Xu Nikolas A. Savage Prof. Dr. Guangbin Dong 《Angewandte Chemie (International ed. in English)》2014,53(7):1891-1895
The rhodium‐catalyzed formation of all‐carbon spirocenters involves a decarbonylative coupling of trisubstituted cyclic olefins and benzocyclobutenones through C? C activation. The metal–ligand combination [{Rh(CO)2Cl}2]/P(C6F5)3 catalyzed this transformation most efficiently. A range of diverse spirocycles were synthesized in good to excellent yields and many sensitive functional groups were tolerated. A mechanistic study supports a hydrogen‐transfer process that occurs through a β‐H elimination/decarbonylation pathway. 相似文献
6.
Dr. Rahul Kisan Kawade Chaowei Hu Nikolas R. Dos Santos Noelle Watson Dr. Xinsong Lin Dr. Kenneth Hanson Dr. Igor V. Alabugin 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(34):14458-14463
3-Point annulations, or phenalenannulations, transform a benzene ring directly into a substituted pyrene by “wrapping” two new cycles around the perimeter of the central ring at three consecutive carbon atoms. This efficient, modular, and general method for π-extension opens access to non-symmetric pyrenes and their expanded analogues. Potentially, this approach can convert any aromatic ring bearing a -CH2Br or a -CHO group into a pyrene moiety. Depending upon the workup choices, the process can be directed towards either tin- or iodo-substituted product formation, giving complementary choices for further various cross-coupling reactions. The two-directional bis-double annulation adds two new polyaromatic extensions with a total of six new aromatic rings at a central core. 相似文献
7.
Hang Xu Chun‐Shuai Cao Han‐Shi Hu Shi‐Bin Wang Jin‐Cheng Liu Peng Cheng Nikolas Kaltsoyannis Jun Li Bin Zhao 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(18):6083-6088
Assembled from [Th48Ni6] nanocages, the first transition‐metal (TM)‐thorium metal–organic framework (MOF, 1 ) has been synthesized and structurally characterized. 1 exhibits high solvent and acid/base stability, and resistance to 400 kGy β irradiation. Notably, 1 captures ReO4? (an analogue of radioactive 99TcO4?, a key species in nuclear wastes) with a maximum capacity of 807 mg g?1, falling among the largest values known to date. Furthermore, 1 can enrich methylene blue (MB) and can also serve as an effective and recyclable catalyst for CO2 fixation with epoxides; there is no significant loss of catalytic activity after 10 cycles. Theoretical studies with nucleus‐independent chemical shifts and natural bond orbital analysis reveal that the [Th6O8] clusters in 1 have a unique stable electronic structure with (d–p)π aromaticity, partially rationalising 1 ′s stability. 相似文献
8.
Stefan Fischer Nikolas Huwyler Dr. Susanne Wolfrum Prof. Dr. Erick M. Carreira 《Angewandte Chemie (International ed. in English)》2016,55(7):2555-2558
We disclose the syntheses of (+)‐bromodanicalipin A as well as (±)‐fluorodanicalipin A. The relative configuration and ground‐state conformation in solution of both molecules was secured by J‐based configuration analysis which revealed that these are identical to natural danicalipin A. Furthermore, preliminary toxicological investigations suggest that the adverse effect of danicalipin A may be due to the lipophilicity of the halogens. 相似文献
9.
Enzyme stabilization strategies based on electrolytes and polyelectrolytes for biosensor applications 总被引:3,自引:0,他引:3
Chaniotakis NA 《Analytical and bioanalytical chemistry》2004,378(1):89-95
The achievements in the area of enzyme stabilization based on electrolytes, polyelectrolytes and polyols is reviewed, in the context of biosensor applications. Both the storage and operational stabilities of the biosensors can be improved using these stabilizers. The deactivation of the enzymes used for the development of biosensors from thermal shock, proteolytic degradation, and non-specific metal-catalyzed oxidation can be drastically reduced with the use of one or more of these stabilizers. It is attempted to deconvolute the effect of these additives on (a) the storage stability or shelf life, and (b) the operational stabilities of the biosensors. Even though there are a large number of techniques and reports dealing with enzyme stabilization, their application to biosensor technology is still very limited. It is thus concluded that the use of the existing enzyme stabilization techniques will have a drastic effect on the storage and operational stabilities of biosensors in the near future. 相似文献
10.
Carbon nanotube array-based biosensor 总被引:8,自引:0,他引:8
Aligned multi-wall carbon nanotubes (MWNT) grown on platinum substrate are used for the development of an amperometric biosensor. The opening and functionalization by oxidation of the nanotube array allows for the efficient immobilization of the model enzyme, glucose oxidase. The carboxylated open-ends of nanotubes are used for the immobilization of the enzymes, while the platinum substrate provides the direct transduction platform for signal monitoring. It is also shown that carbon nanotubes can play a dual role, both as immobilization matrices and as mediators, allowing for the development of a third generation of biosensor systems, with good overall analytical characteristics. 相似文献