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821.
H. Durchschlag O. Kratky J. W. Breitenbach B. A. Wolf 《Monatshefte für Chemie / Chemical Monthly》1970,101(5):1462-1470
Zusammenfassung Es wurde das Streuverhalten von Polystyrol im thermodynamisch schlechten Lösungsmittel Cyclohexan zwischen Entmischungstemperatur und-Temperatur untersucht. Beim -Punkt und nahe dabei liegt das Verhalten eines statistisch verknäuelten Fadenmoleküls vor. Unterhalb der-Temperatur beginnt eine Aggregation. Knapp oberhalb der Entmischungstemperatur entspricht das Molekulargewicht etwa einer Verhängung zweier Fadenmoleküle. Ein Auftreten von kompakten Polymerknäueln ist bei dieser Temperatur nicht festzustellen. Der Einfluß des Fadenquerschnitts auf die Streukurve ist beträchtlich, da der Querschnitt nicht viel kleiner als die Persistenzlänge ist. Trotzdem läßt sich die Persistenzlänge (a=12,2 Å) aus dem Übergangspunkt zwischen den etwa 1/(2)2 und 1/(2) proportionalen Bereichen bestimmen, da der Knick im Übergangsbereich infolge der großen Anzahl von Persistenzlängen pro Molekül sehr ausgeprägt ist.
Mit 3 Abbildungen
Herrn Prof. Dr.E. Broda zum 60. Geburtstag gewidmet. 相似文献
X-Ray small-angle investigations on solutions of a polystyrene sample with a narrow molecular weight distribution
Investigations were made of the scattering behaviour of polystyrene in the thermodynamically bad solvent cyclohexane between precipitation-temperature and-temperature. At the-point and close to it the behaviour of a statistically coiled chain molecule is found. Below-temperature an aggregation is beginning. Just above precipitation-temperature the molecular weight corresponds to an entanglement of two chain molecules. Appearance of compact polymer coils could not be noted at this temperature. The influence of the chain crosssection upon the scattering curve is considerable as the crosssection is not much smaller than the persistence length. Nevertheless, the persistence length (a=12.2 Å) may be determined from the transition point between the ranges roughly proportional to 1/(2)2 and 1/(2) as the break within the transition range is very distinct on account of the great number of persistence lengths per molecule.
Mit 3 Abbildungen
Herrn Prof. Dr.E. Broda zum 60. Geburtstag gewidmet. 相似文献
822.
O. K. Krasil’nikova A. M. Voloshchuk A. E. Evsyukhin N. Y. Lomovskaya 《Colloid Journal》2006,68(2):182-188
The new template procedure for preparing ultramicro-, micro-, and supermicroporous carbon adsorbents is proposed on the basis
of the use of two polymers with different thermal stabilities as a template matrix and a carbonizable carbon source. The polymeric
template matrix is removed by thermal decomposition in the low-temperature pyrolysis of the polymer mixture, whereas the second
polymer component of a mixture is transformed into a carbonizate. The resultant monolithic carbonizate is the polymeric matrix
replica and represents a molecular-sieve ultramicroporous carbon adsorbent, which adsorbs water vapor at 293 K and does not
adsorb nitrogen vapor at 77 K. The activation of this carbonizate with water vapor leads to a series of micro-and supermicroporous
carbon adsorbents with a broad range of the parameters of a pore structure: BET specific surface area S
BET is 610–2130 m2/g, micropore volume W
0 is 0.20–0.69 cm3/g, micropore half-width x
0 (slit model) is 0.20–0.70 nm, mesopore specific area S
me is 20–1000 m2/g, and characteristic adsorption energy E
0 is 15.6–27.4 kJ/mol.
Original Russian Text ? O.K. Krasil’nikova, A.M. Voloshchuk, A.E. Evsyukhin, N.Y. Lomovsakaya, 2006, published in Kolloidnyi
Zhurnal, 2006, Vol. 68, No. 2, pp. 207–213. 相似文献
823.
W. O. Hofer K. Besocke B. Stritzker 《Applied Physics A: Materials Science & Processing》1983,30(2):83-86
The temperature dependence of the sputtering yield was measured for lOOkeV per atom bombardment of silver with molecular and atomic antimony ions. No exponential increase of the yield was found in the temperature range from 25° to 775 °C, although a pronounced nonlinear effect is observed when the yield of these projectiles is compared,Y(Sb 2 + )≈ 1.5×[2Y(Sb+)]. We conclude that there is no influence of the lattice temperature on collision spikes. 相似文献
824.
Resonance-enhanced multiphoton ionization (REMPI) of the \(\tilde B\) and \(\tilde C'\) states of NH3 in a pulsed supersonic molecular beam was observed at 304–340 nm, using the multiphoton-ionization mass-spectrometer system described herein. The observed features are the result of a 2+1 MPI process and correspond quite well with the reported 3+1 MPI of NH3 in the literature from the ground state of opposite parity. 相似文献
825.
B. G. Bazarov R. F. Klevtsova Ts. T. Bazarova L. A. Glinskaya K. N. Fedorov Zh. G. Bazarova O. D. Chimitova 《Russian Journal of Inorganic Chemistry》2006,51(5):794-799
Systems Tl2MoO4-E(MoO4)2 (E = Zr, Hf) are studied using X-ray powder diffraction, DTA, and IR spectroscopy. Compounds Tl8E(MoO4)6 and Tl2E(MoO4)2 are found in these systems. T-x diagrams for the Tl2MoO4-Zr(MoO4)2 system are designed. Single crystals are grown and structure is solved for Tl8Hf(MoO4)6. The compound crystallizes in a monoclinic structure with the unit cell parameters a = 9.9688(6) Å, b = 18.830(1) Å, c = 7.8488(5) Å, β = 108.538(1)°, Z = 2, space group C2/m. The main structural fragment is a [HfMo6O24]8? isle group. Three crystallographically independent types of Tl polyhedra uniformly fill spaces between [HfMo6O24]8? fragments to form a three-dimensional framework. 相似文献
826.
R. O. Kochkanyan S. S. Radkova N. L. Klyuev L. Yu. Petrovskaya S. N. Baranov 《Chemistry of Heterocyclic Compounds》1978,14(12):1372-1375
Previously undescribed pyrimidine betaines with cycloammonium and triphenylphosphonium cations were obtained. A study of the UV, IR, PMR, and mass spectra made it possible to draw a conclusion regarding the noncyclic structure of betaines stabilized by an intramolecular donor-acceptor interaction of the charge-transfer complex (CTC) type.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1687–1690, December, 1978. 相似文献
827.
Bromodichloroacetaldehyde was synthesized by two methods. The first synthesis started from chloral, which was allowed to react with Ph3P and the resultant compound brominated and hydrolyzed to give bromodichloroacetaldehyde in an overall yield of 60%. Purification by repeated distillation from P2O5 gave polymerization grade bromodichloroacetabldehyde. Bromodichloroacetaldehyde could also be synthesized by bromination of dichloroacetaldehyde diethyl acetal. The yields of this synthesis were only 20–30%, and the aldehyde could not be purified readily to give polymerization grade monomer. Bromodichloroacetaldehyde could be homopolymerized at ?30°C with anionic and also some cationic initiators to a polymer which was insoluble and did not melt but degraded to monomer above 200°C. The ceiling temperature of the polymerization was ?15°C in 1M solution. Bromodichloroacetaldehyde could also be copolymerized with isocyanates, primarily aryl isocyanates, and also with chloral. 相似文献
828.
Abstract— We have studied the influence of the heavy metal ions Ag+ and Hg2+ on the photoinactivation and photodimerization of transforming DNA and of bacteriophage. The rate of inactivation of Haemophilus influenzae transforming DNA by ultraviolet (UV) radiation was enhanced by a factor of 30 when it was complexed with Ag+ . This enhancement was correlated with a comparable increase in the rate of thymine dimerization. In contrast, mercuric ions led to a reduction in the rates of both inactivation and dimerization. When we examined the effects of these metal ions on the photobiology of bacteriophage, we again found that Ag+ enhanced and Hg2+ reduced the rate of ultraviolet inactivation. These results demonstrate that heavy metals may be useful tools for studying the photochemistry and photobiology of nucleic acids. 相似文献
829.
830.
The total synthesis of rhodoxanthin according to the scheme C14 + C12 + C14 is reported. 相似文献