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121.
A series of nitrogen‐tethered allenynes (‘5‐aza‐1,2‐dien‐7‐ynes’) 1 were transformed to the corresponding 3‐acyl‐4‐alkenylpyrrolidines 3 when treated with a catalytic amount of PtCl2 in MeOH at 70°. Initial Pt‐promoted cyclization forms a nonclassical carbocationic intermediate. In contrast to the cycloisomerization in toluene, which produced the bicyclic cyclobutenes 2 , the intermediate is intercepted by addition of an oxygen nucleophile to achieve the formal hydrative cyclization. 相似文献
122.
T Yokozawa N Suzuki P D Zheng H Oura I Nishioka 《Chemical & pharmaceutical bulletin》1984,32(11):4506-4513
123.
124.
Tadashi Mochizuki Takanori Akiyoshi Hideo Iwata 《Fresenius' Journal of Analytical Chemistry》1987,327(5-6):474-477
Summary A new interelement correction method has been developed for the X-ray fluorescent determination of chromium in high-alloy steels and nickel-base alloys. The calibration equation which was derived from the JIS (Japanese Industrial Standards) model is applicable over wide ranges of compositions by preparation of only Fe-Cr binary standards.The new approach gave better accuracy than that based on Rasberry-Heinrich correction model. The accuracies (d) were 0.08% for high-alloy steels and 0.14% for nickel-base alloys.
Korrekturmethode für die röntgenfluorescenzspektrometrische Bestimmung von Chrom in hochlegierten Stählen und Nickellegierungen
Zusammenfassung Die Eich-Gleichung für das neue Korrekturverfahren wurde vom JIS-Modell (Japanese Industrial Standards) abgeleitet und ist über einen weiten Bereich von Zusammensetzungen durch Herstellung von lediglich binären Fe-Cr-Standards einsetzbar. Das beschriebene Verfahren bietet eine bessere Genauigkeit als die Methode nach dem Korrekturmodell von Rasberry-Heinrich. Sie betrug 0,08% für hochlegierte Stähle und 0,14% für Nickellegierungen.相似文献
125.
Dr. Toshiichi Soen Dr. Motohide Shimomura Dr. Takanori Uchida Dr. Hiromichi Kawai 《Colloid and polymer science》1974,252(11):933-943
Summary The grain boundary relaxation phenomena, which have been found in the mechanical relaxation of the cast films of a series ofgraft copolymers ofpoly(methyl acrylate) with styrene, are examined again, in order to understand its relaxation mechanism, by using some particular series of heterogeneous systems of two components having different interaction between the two phases and, subsequently, different grain boundary structure; i. e., two series of poly(vinyl acetate) filled with two types of carbon blacks having relatively high and low surface activities, respectively, a series ofmechanical mixtures ofpoly(vinyl acetate) with polystyrene, and a series of styrene-isoprene-styrene tri-block copolymers.The grain boundary relaxation phenomena are again detected for the series of the tri-block copolymers but definitely not for the series of the mechanical mixtures, suggesting that the grain boundary relaxation phenomena must arise not from the heterogeneous structures themselves but from characteristic arrangements of molecular chains at the boundary of the two phases. That is, there must be a considerably strong interaction between the two phases, and there exists an intermediate phase in which the polymer segments of soft component are rigidified while the other polymer segments of hard component are softened. In other words, there must be a cooperative motions of chain segments of the two components to produce a mechanical relaxation under a certain environmental condition, such as temperature and time scale of observation.
With 6 figures and 13 tables
Presented at the 20th Annual Symposium on Rheology, Japan, Fukui, Oct. 18, 1972. 相似文献
Zusammenfassung Die Korngrenzenrelaxationsphänomene, die in der mechanischen Relaxation einer Serie von aus Graft-Copolymeren von Polymethylacrylat mit Styrol gefunden wurden, wurden erneut geprüft, um den Relaxations-mechanismus zu verstehen, unter Verwendung einer besonderen Serie von heterogenen Systemen zweier Komponenten, die verschiedene Wechselwirkungen zwischen den zwie Phasen besitzen und deshalb verschiedene Korgrenzenstrukturen. Das heißt, wir verwendeten zwei Serien von Polyvinylacetaten, gefüllt mit zwei Rußtypen von vergleichsweise hoher und niedriger Oberflächenaktivität, eine Serie von mechanischen Mischungen aus Polyvinylacetat mit Polystyrol und eine Serie von Styrol-Isopren-Dreiblockcopolymeren. Die Korngrenzenrelaxationsphänomene, wurden für die Serie der Dreiblockcopolymeren wiederum festgestellt, aber definitiv nicht für die Serie der mechanischen Mischungen. Das läßt vermuten, daß Korngrenzenrelaxation nicht von heterogenen Strukturen selbst, sondern von charakteristischen Anordnungen der molekularen Kette an der Grenze von zwei Phasen herrührt. Das heißt, es muß eine beträchtlich strenge Wechselwirkung zwischen den zwei Phasen bestehen, und es muß eine Zwischenphase existieren, in welcher die Polymersegmente der weichen Komponente versteift werden, während die anderen Polymersegmente der harten Komponente erweicht werden. Mit anderen Worten, es müssen cooperative Bewegungen von Kettensegmenten der zwei Komponenten vorhanden sein, um eine mechannische Relaxation unter gewissen Umgebungsbedingungenzuerzeugen, Umgebungsbedingungen wie Temperatur und Zeitskala der Beobachtungen.
With 6 figures and 13 tables
Presented at the 20th Annual Symposium on Rheology, Japan, Fukui, Oct. 18, 1972. 相似文献
126.
127.
Proton spin-lattice relaxation times of solvent molecules were measured on ternary mixtures of a polymer and two solvents by the adiabatic rapid-passage method. The selective adsorption of a good solvent was verified by this experimental technique for the systems benzene—cyclohexane—polystyrene(PS), benzene—carbon tetrachloride—poly(methyl methacrylate)(PMMA), and chloroform—carbon tetrachloride—PMMA. The number of molecules of adsorbed benzene per monomeric unit of PS was estimated to be about four, which is almost identical with that determined previously by thermodynamic measurements. The number of molecules of benzene and chloroform adsorbed on PMMA were also determined to be about five and four, respectively. It was found that the interaction between chloroform and PMMA has the greatest effect on the molecular motion of the solvent, whereas the benzene—PS interaction is weak. 相似文献
128.
Reaction profiles and energetics for the reactions of substituted benzaldehydes with a series of different simple metal hydrides (BH(3), BMeH(2), BMe(2)H, AlH(3), and AlMe(2)H) are examined computationally. B3LYP/6-31G optimizations and MP2/6-311G single point energy calculations revealed that the Al reagents are more reactive than B reagents. Replacement of H with Me on BH(3) or AlH(3) makes the reduction transition state (TS) less stable. Accordingly the overall reactivity is in the order AlH(3) > AlMe(2)H > BH(3) > BMe(2)H. The Hammett rho value for substituted benzaldehydes (BAs) is negative for the initial complex formation and positive for the hydride-transfer step. The size and the sign of the apparent rho value depend on the relative stabilities of the separated reactants and the complex. The TS structures vary according to the Hammond postulate for substituted BAs and the variation is reflected in carbonyl-carbon and aldehyde-deuterium isotope effects. Comparison of the reaction profiles of the monomer and dimer reagents reveals that the real reacting species is the monomer in the gas phase for BH(3) but the dimer for BMe(2)H. 相似文献
129.
Akine S Taniguchi T Saiki T Nabeshima T 《Journal of the American Chemical Society》2005,127(2):540-541
Ca2+-selective recognition was achieved by using the site-selective transmetalation of homotrinuclear metallohost [L1Zn3]2+ containing a linear tetraoxime ligand. The selectivity (log(KCa/KMg) > 5.1) is comparable to those of the excellent Ca2+ receptors or sensors such as BAPTA, Quin2, and K23E1. X-ray crystallography revealed that the Ca2+ complex [L1Zn2Ca]2+ has a helical structure. On the other hand, the larger analogue H6L2 gave a mixture of [L2Zn4]2+ isomers, which selectively recognizes Ba2+ to give a single tetranuclear complex, [L2Zn3Ba]2+. 相似文献
130.
Ir-catalyzed enantioselective [2 + 2 + 2] cycloaddition of tetraynes or an octayne with monoalkynes proceeded to give helically-chiral quinquearyl and noviaryl compounds, which respectively have four and eight consecutive axial chiralities, in an almost enantiomerically pure form. 相似文献