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131.
A method has been developed for the extraction of rhenium/VII/ with methylene blue. Nitrobenzene was found to be the most effective extractant for Re/VII/. The stoichiometry of metal to reagent determined by the method of substoichiometric extraction and slope-ratio method was found to be 11. 相似文献
132.
Recently (Nguyen and Bhatia, J. Phys. Chem. C 111:2212–2222, 2007) we have proposed a new algorithm utilising cluster analysis principles to determine pore network accessibility of a disordered
material. The algorithm was applied to determine pore accessibility of the reconstructed molecular structure of a saccharose
char, obtained in our recent work using hybrid reverse Monte Carlo simulation (Nguyen et al., Mol. Simul. 32:567–577, 2006). The method also identifies kinetically closed pores not accessed by adsorbate molecules at low temperature, when their
low kinetic energy cannot overcome the potential barrier at the mouths of pores that can otherwise accommodate them.
In the current work, the results are validated by transition state theory calculations for N2 and Ar adsorption, showing that N2 can equilibrate in narrow micropores at practical time scales at 300 K, but not at 77 K. Large differences between time scales
for micropore entry and exit are predicted at low temperature for N2, the latter being smaller by over three orders of magnitude. For N2 at 77 K the time constant for pore entry exceeds 3 hr., while for exit it is 134 days. At 300 K these values are smaller
than 1 μs, indicating good accessibility at this temperature. These results are verified by molecular dynamics simulations,
which reveal that while N2 molecules enter and leave all pores frequently at 300 K, entry and exit events for apparently inaccessible pores are absent
at 77 K. For Ar at 87 K better accessibility is evident for the saccharose char compared to N2 at 77 K. This finding is now experimentally shown in this work by comparison of pore size distributions obtained from experimental
nitrogen adsorption isotherms of nitrogen and argon at 77 K and 87 K. 相似文献
133.
The hydrolysis and biosynthetic reactions of partially purified Pichia etchellsii β-glucosidase II from recombinant Escherichia coli pBG22:JM109 are described. With 167 mmol/L of initial glucose, the products of synthetic reactions, glucobiose and glucotriose,
accumulated to 18 and 6 mmol/L, respectively. In transglycosylation reactions with 79 mmol/L of initial cellobiose, glucotriose
and glucopentaose were obtained at 4.5 and 2 mmol/L, respectively. The effects of incubation time and substrate concentration
were studied on the yield of synthesized oligosaccharides. In a reaction time of 24 h with 468 mmol/L of initial cellobiose,
glucotriose and glucopentaose levels of 21.6 and 6.6 mmol/L, respectively, were obtained. The addition of dimethyl sulfoxide
(DMSO) further increased the yields of the products by 10%. Detailed kinetic analysis indicated a significant (about twofold)
increase in V
max/K
M
of synthetic reactions in the presence of DMSO. A study of other disaccharides in transglycosylation reactions indicated
biosynthetic activity in the order of sophorose > gentiobiose > cellobiose. 相似文献
134.
Molar excess volume V
E
and enthalpy H
E
data have been measured at 25°C for pyridine A saturated with anhydrous cupric chloride (S) [A(S)]+ B [where B is aniline or o-toluidine (OT) or formamide (FD) or N, N-dimethylformamide (NND)] mixtures on the assumption that while the standard state of B is that of pure components B, the standard state of A(S) is that of A saturated with the salt S. The excess volume or enthalpy data for an equimolar mixture at a given temperature have been utilized to evaluate the interactional parameter X12 of the Sanchez and Lacombe theory of fluid mixtures at that temperature, and the same has been combined with V
E
(x
A
) data for a good prediction not only of the coresponding H
E
(x
A
) data for the mixture but also the extent of unlike interactions between the A(S) and B components of these A(S)+B mixtures. 相似文献
135.
We report here our investigations using Monte Carlo and molecular dynamics (MD) simulations, as well as quasi-elastic neutron
scattering experiments, to study the adsorption and diffusion of H2 and D2 in zeolite Rho. In the simulations, quantum effects are incorporated via the Feynman-Hibbs variational approach. At low temperatures,
we observe a reversal of kinetic molecular sieving in which D2 diffuses faster than H2. Based on fits of bulk data, we suggest new set of potential parameters for hydrogen, with the Feynman-Hibbs variational
approach used for quantum corrections. The transport properties obtained from MD simulations are in excellent agreement with
the experimental results, with both showing significant quantum effects on the transport at low temperature. The MD simulation
results on two different structures of zeolite Rho clearly demonstrate that the quantum effect is very sensitive to pore size.
High transport flux selectivity is noted at low temperatures, suggesting feasibility of kinetic isotope separation. 相似文献
136.
Mathew Mendalin Narayana Badiadka Sreekumar Naracham Veedu Vipin Kuttamath 《Mikrochimica acta》2004,144(4):291-295
A rapid and sensitive spectrophotometric method is described for the determination of trace amounts of cerium using Variamine Blue (VB) as a chromogenic reagent. The proposed method is based on the reaction of cerium with potassium iodide in acidic medium to liberate iodine, which oxidizes Variamine Blue to give a violet colored species with an absorption maximum at 560nm. Beers law was obeyed in the range 2–10µg mL–1 of cerium. The molar absorptivity and Sandells sensitivity are found to be 1.65×104L mol–1cm–1 and 8.48×10–3µgcm–2, respectively. The proposed method has been successfully applied to the determination of cerium in alloy and synthetic mixtures. 相似文献
137.
Bhanja R Joseph R Tuli SK Beri SB Bhatia VS Kaur G Kaur M Mittra IS Bhalla KB Bharti A Lokanathan S Gupta SK Gupta VK Kaul GL Kumar V Mangotra LK Prakash Y Rao NK Sankhydhar S Satti S Claesson G Garpman S Herrström NY Jakobsson B Lund I Norén B Oskarsson A Otterlund I Persson S Sherif MM Söderström K 《Physical review letters》1985,54(8):771-774
138.
139.
A series of eight N1-(β-D-ribofuranosyl)-C4-(coumarin-4′′-yl)-1,2,3-triazoles have been synthesized by Cu(I)-catalyzed click reaction of 1-azido-1-deoxy-2,3,5-tri-O-benzoyl-β-D-ribofuranose with differently substituted 4-ethynylcoumarins followed by debenzoylation of the resulted N1-(2′,3′,5′-tri-O-benzoyl-β-D-ribofuranosyl)-C4-(coumarin-4″-yl)-1,2,3-triazoles in 71 to 89% overall yields. The structures of all the synthesized compounds were established on the basis of their spectral data analysis that was further confirmed by X-ray data analysis of one of the model benzoylated compounds, i.e. N1-(2′,3′,5′-tri-O-benzoyl-β-D-ribofuranosyl)-C4-(7″-isopropoxycoumarin-4″-yl)-1,2,3-triazole. 相似文献
140.
Tapan Behl Amit Gupta Mohammed Albratty Asim Najmi Abdulkarim M. Meraya Hassan A. Alhazmi Md. Khalid Anwer Saurabh Bhatia Simona Gabriela Bungau 《Molecules (Basel, Switzerland)》2022,27(18)
The main characteristic feature of diabetes mellitus is the disturbance of carbohydrate, lipid, and protein metabolism, which results in insulin insufficiency and can also lead to insulin resistance. Both the acute and chronic diabetic cases are increasing at an exponential rate, which is also flagged by the World Health Organization (WHO) and the International Diabetes Federation (IDF). Treatment of diabetes mellitus with synthetic drugs often fails to provide desired results and limits its use to symptomatic treatment only. This has resulted in the exploration of alternative medicine, of which herbal treatment is gaining popularity these days. Owing to their safety benefits, treatment compliance, and ability to exhibit effects without disturbing internal homeostasis, research in the field of herbal and ayurvedic treatments has gained importance. Medicinal phytoconstituents include micronutrients, amino acids, proteins, mucilage, critical oils, triterpenoids, saponins, carotenoids, alkaloids, flavonoids, phenolic acids, tannins, and coumarins, which play a dynamic function in the prevention and treatment of diabetes mellitus. Alkaloids found in medicinal plants represent an intriguing potential for the inception of novel approaches to diabetes mellitus therapies. Thus, this review article highlights detailed information on alkaloidal phytoconstituents, which includes sources and structures of alkaloids along with the associated mechanism involved in the management of diabetes mellitus. From the available literature and data presented, it can be concluded that these compounds hold tremendous potential for use as monotherapies or in combination with current treatments, which can result in the development of better efficacy and safety profiles. 相似文献