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991.
An efficient methodology for the preparation of a series of 2,3-disubstituted-quinazolin-4(3H)-ones is described via a three step reaction from anthranilic acid. The obtained results also reveal that microwave-assisted rapid decomposition of formamide under controlled conditions of power, temperature and time is a very convenient source of ammonia for the synthesis of 2-substituted-quinazolin-4(3H)-ones and other rings. 相似文献
992.
N. Majcen E. Bulska I. Leito Emilia Vassileva Ioannis Papadakis Philip Taylor 《Accreditation and quality assurance》2002,7(10):419-422
In 2000, the European Commission-Joint Research Centre, Institute for Reference Materials and Measurements (EC-JRC-IRMM) set
up a project to improve the scientific basis for metrology in chemistry (MiC) in EU candidate countries. Several activities
were initiated (training, fellowships, sponsoring seminars, conferences and participation in the International Measurement
Evaluation Programme – IMEP). A particular initiative, discussed here, was to assist each of the national measurement institutes
of these countries to write a status report on MiC. Most importantly, the report was intended to be the end-product of a process
to document the current status of MiC. Intentionally, this process involved not only the providers of services in MiC but
all the major stakeholders in this activity (e.g. major field laboratories, accreditation bodies, regulatory bodies, educators,
professional bodies). The status reports are intended to be the first step of the future improvement process. In those countries
where writing of the status reports has been started (Slovenia, Poland, Bulgaria and Estonia) the first signs are that this
process leads to better co-operation and particularly a better understanding of what the future role and activities of each
of these stakeholders should be.
Correspondence to N. Majcen 相似文献
993.
Ioannis Papadakis Lutgart Van Nevel Caroline Harper Yetunde Aregbe Philip D. P. Taylor 《Accreditation and quality assurance》2007,12(2):105-111
The International Measurement Evaluation Programme (IMEP) is an interlaboratory comparison scheme, founded, owned and co-ordinated
by the Institute for Reference Materials and Measurements (IRMM) since 1988. IMEP-12, for the fourth time in the series, focused
on trace elements in water and it was designed specifically to support European Commission directive 98/83/EC. Reference values
for the concentration of ten elements were established with expanded uncertainties according to GUM. In total, 348 laboratories
from 46 countries in five continents participated in the comparison and the degree of equivalence between the results of the
laboratories and the reference values is presented graphically. Samples from the same batch were distributed to ten laboratories
from European Countries, which represented their country in the framework of the EUROMET project 528. Participation in this
comparison was offered to the European Co-operation for Accreditation (EA) for participation of accredited laboratories from
all over Europe in the framework of the collaboration between IRMM and EA and to laboratories from the EU new member states
and acceding countries in the frame of IRMM’s ‘Metrology in Chemistry support program for EU new member states and acceding
countries.’ 相似文献
994.
Ioannis D. Kostas Georgios A. Heropoulos Dimitra Kovala-Demertzi Paras N. Yadav Mavroudis A. Demertzis Giang Vo-Thanh André Loupy 《Tetrahedron letters》2006,47(26):4403-4407
A new air- and moisture-stable palladium complex with salicylaldehyde N(4)-hexamethyleneiminylthiosemicarbazone has been synthesized. According to its crystal structure, the metal is bonded to 2 equiv monoanionic thiosemicarbazone moieties in a N,S-bidentate fashion, forming two five-membered chelate rings, while additional intramolecular bonds stabilize the structure. In contrast to other palladium complexes with thiosemicarbazones, this complex was inactive towards the Suzuki-Miyaura coupling under aerobic conditions, by conventional heating. On the other hand, microwave irradiation promoted the effective catalytic activity of the complex for the coupling of aryl bromides and chlorides with phenylboronic acid in DMF/H2O, under aerobic conditions, with turnover numbers of up to 37,000. 相似文献
995.
Ioannis Karatzas 《Applied Mathematics and Optimization》1981,7(1):175-189
We consider the problem of optimally tracking the random demandx+w
t, w. Brownian motion, by a nondecreasing process. adapted to the Brownian past, so as to minimize the expected lossE
0
T
(x+wt–t)dt. The decision problem is reduced to a free boundary one, and the latter is studied and solved for a large class of cost functions().This research was supported in part by the Air Force Office of Scientific Research, under AF-AFOSR 77-3063. 相似文献
996.
Adam W Bottke N Krebs O Lykakis I Orfanopoulos M Stratakis M 《Journal of the American Chemical Society》2002,124(48):14403-14409
The ene reaction of singlet oxygen ((1)O(2)), triazolinedione (TAD), and nitrosoarene, specifically 4-nitronitrosobenzene (ArNO), with the tetrasubstituted 1,3-allylically strained, chiral allylic alcohol 3,4-dimethylpent-3-en-2-ol (2) leads to the threo-configured ene products in high diastereoselectivity, a consequence of the hydroxy-group directivity. Hydrogen bonding favors formation of the threo-configured encounter complex threo-EC in the early stage of ene reaction. For the analogous twix deuterium-labeled allylic alcohol Z-2-d(3), a hitherto unrecognized dichotomy between (1)O(2) and the ArNO and TAD enophiles is disclosed in the regioselectivity of the tetrasubstituted alcohol: Whereas for ArNO and TAD, hydrogen bonding with the allylic hydroxy group dictates the regioselectivity (twix selectivity), for (1)O(2), the cis effect dominates (twin/trix selectivity). From the interdependence between the twix/twin regioselectivity and the threo/erythro diastereoselectivity, it has been recognized that the enophile also attacks the allylic alcohol from the erythro pi face without assistance by hydrogen bonding with the allylic hydroxy functionality. 相似文献
997.
Olefin metathesis: remote substituents governing the stereoselectivity of 11-membered-ring formation
[reaction: see text] Stereospecific RCM reaction of 7 (R1 = Me) results in the formation of (Z)-11-membered macrocycle 9c. Cascade RCM/ROM/RCM transformation of 7 (R1 = H) affords the thermodynamically more stable spirocycle product 12. 相似文献
998.
999.
1000.
Ioannis K. Argyros 《Journal of Applied Mathematics and Computing》2007,24(1-2):305-312
Using a weaker version of the Newton-Kantorovich theorem [6] given by us in [3], we show how to refine the results given in [8] dealing with the analyzing of the effect of small perturbations in problem data on the solution. The new results are obtained under weaker hypotheses and the same computational cost as in [8]. 相似文献