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961.
Marcus G Helml W Gu X Deng Y Hartmann R Kobayashi T Strueder L Kienberger R Krausz F 《Physical review letters》2012,108(2):023201
Subfemtosecond bursts of extreme ultraviolet radiation, facilitated by a process known as high-order harmonic generation, are a key ingredient for attosecond metrology, providing a tool to precisely initiate and probe ultrafast dynamics in the microcosms of atoms, molecules, and solids. These ultrashort pulses are always, and as a by-product of the way they are generated, accompanied by laser-induced recollisions of electrons with their parent ions. By using a few-cycle infrared (λ(0)=2.1 μm) driving laser, we were able to directly excite high-energy (~870 eV) inner-shell electrons through laser-induced electron recollision, opening the door to time-resolved studies of core-level and concomitant multielectron dynamics. 相似文献
962.
Andrzej Gzella Urszula Wrzeciono Wolfram Pppel 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(4):462-466
The three title compounds, namely (Z)‐1‐(4,5‐dinitroimidazol‐1‐yl)‐3‐morpholinopropan‐2‐one 2,4‐dinitrophenylhydrazone, C16H17N9O9, (IV), (Z)‐3‐morpholino‐1‐(4‐morpholino‐5‐nitroimidazol‐1‐yl)propan‐2‐one 2,4‐dinitrophenylhydrazone, C20H25N9O8, (Va), and (E)‐3‐morpholino‐1‐(4‐morpholino‐5‐nitroimidazol‐1‐yl)propan‐2‐one 2,4‐dinitrophenylhydrazone tetrahydrofuran solvate, C20H25N9O8·C4H8O, (Vb), have been prepared and their structures determined. In (IV), the C‐4 nitro group is nearly perpendicular to the imidazole ring and the C‐4—NO2 bond length is comparable to the value for a normal single Csp2—NO2 bond. In (IV), (Va) and (Vb), the C‐5 nitro group deviates insignificantly from the imidazole plane and the C‐5—NO2 bond length is far shorter in all three compounds than C‐4—NO2 in (IV). In consequence, the C‐4 nitro group in (IV) is easily replaced by morpholine, while the C‐5 nitro group in (IV), (Va) and (Vb) shows an extraordinary stability on treatment with the amine. The E configuration in (Vb) is stabilized by a three‐centre hydrogen bond. 相似文献
963.
In this paper, we present an integrated environment for validated modeling and simulation of kinematics and dynamics of various classes of mechanical systems SMARTMOBILE ( S imulation and M odeling of dyn A mics in MOBILE: R eliable and T emplate–based) built on top of the non-validated tool MOBILE. We outline the main features of SMARTMOBILE and its applicability area. The functionality of the new tool and the importance of the application of validated techniques are demonstrated. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
964.
965.
Results of polymerization and laser flash photolysis studies concerning the direct and indirect photoinitiation of cationic polymerizations using N-alkoxy pyridinium and N-alkoxy quinolinium salts are presented. The indirect action can be based on (a) the generation of carbocations via the oxidation of photochemically produced free radicals and (b) the generation of radical cations via the reaction of electronically excited sensitizers with pyridinium or quinolinium ions. With respect to (a) substituted vinyl bromides were found be an effective source of oxidizable free radicals (vinyl radicals), and regarding (b) singlet or triplet excited states of thioxanthone, anthracene, perylene and phenothiazine, which, in the ground state, strongly absorb light in the 300 to 400 nm range, were found to react rapidly with pyridinium salts. 相似文献
966.
Wolfram Becker 《Macromolecular Symposia》1993,74(1):225-234
In the standard test methods, the thermal action proceeds even today in most cases under the conditions of the well ventilated fire. The intensity of the thermal action varies widely, however, depending on the designed safety level. In the last few years, the outstanding purpose was to test the behaviour of products under the action of fire, in particular the time to the flash-over. The intensity of the fire action rises accordingly, despite the possibility of further free ventilation, to such a degree that the test conditions in laboratory processes can reflect reality only under certain conditions. This philosophy is drawn from the results of statistical investigations in the U.S. is that the time to the flash-over in a room is equal to the time to untenability, because most of the victims of the fire were not present in the room where the fire broke out. Test methods on a real scale that serve this designed safety level will therefore have to work with the high fire action on the products to be tested. In contrast, however, in some European countries the philosophy underlying the adoption of designed safety levels is that the main purpose is to protect human beings who are present in the room where the fire breaks out. According to this philosophy, a fire development that threatens to become dangerous must always be prevented. Consequently, interest is focused mainly on restricting the spread of fire and thus preventing a flash-over. The test methods to be designed with this purpose in view should, therefore, simulate the conditions of the starting fire or the developing fire. The efficiency of a fire retardant can then be evaluated according to whether the fire spread is restricted or not. Under these conditions, the question of the time to be flash-over is of no significance. With standard tests, it is impossible to make a statement as to how far the fire safety of products can be improved by the use of fire retardants unless the safety-relevant range of application for the test method has been defined. 相似文献
967.
Ivanka G. popovi Lynne Katsikas Sne ana M. Rangelov Jovan S. Veli
kovi
Wolfram Schnabel 《Macromolecular Symposia》1993,74(1):291-294
The non-oxidative thermal degradation kinetics and mechanism of poly(2-monochloro, 2, 2-dichloro and 2, 2, 2, -trichloroethyl methacrylates) were studied. The influence of the antioxidant IRGA-NOX 1010 on the thermal degradation of the monochloroethyl derivative was also investigated. Initial hydrolysis data on the major degradation products, the corresponding monomers, were obtained. 相似文献
968.
969.
970.
Andreas Martin Christoph Tefehne Wolfram Gronski 《Macromolecular rapid communications》1996,17(5):305-311
Liquid-crystalline (LC) block copolymers of lamellar morphology were prepared via anionic polymerization of polystyrene-block-1,2-polybutadiene and subsequent introduction of a deuterated mesogen by polymer analogous reaction. Deuteron NMR measurements show that the first-order nematic/isotropic transition in the block copolymer is changed to a critical behaviour under the influence of shear. In the nematic phase the order parameter is reduced with respect to the homopolymer, and there is no evidence of an isotropic boundary layer of the LC-block at the nematic/isotropic interface. 相似文献