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971.
972.
Christopher A. Nolph Daniel E. Sievers Sujaree Kaewgun Courtney J. Kucera Daniel H. McKinney John P. Rientjes Jamie L. White Radhika Bhave Burtrand I. Lee 《Catalysis Letters》2007,117(3-4):102-106
Nanocrystalline titania of different phases were produced by ambient condition sol process with phase control originating
from alterations in experimental variables. The produced titania photocatalysts were characterized by use of x-ray diffraction,
BET surface area, transmission electron microscopy and related to methyl orange degradation. The results showed that the photocatalytic
activity of brookite and anatase phase titania samples to be greater than that of Degussa P-25 and rutile phase titania sample.
In addition, brookite, due to surface area considerations, appears to be the most photocatalytically active phase of titania. 相似文献
973.
在光促进温和条件下,以甲酸甲酯为C1源,研究了非贵金属钴盐、铜盐催化二卤代烷烃(1,6-二溴己烷和1-氯-6-溴己烷)的羰基化反应。实验表明,1,6-二溴己烷和1-氯-6-溴己烷都是发生单羰基化反应,而且是C-Br键发生反应,分别得到的卤代羧酸甲酯为Br(CH2)6CO2CH3和Cl(CH2)6CO2CH3。 相似文献
974.
Interpenetrating polymer networks (IPNs) of polydimethylsiloxane (PDMS) and poly(2‐hydroxyethyl methacrylate) (PHEMA) were prepared by sequential method. The dynamic mechanical parameters of obtained IPNs and their variations with the structural composition were evaluated. The results for the IPNs were compared with corresponding physically blended systems. The tensile properties and damping factor (tan δ) were assessed by stress–strain measurement and dynamic mechanical thermal analysis (DMTA), respectively. The glass–rubber transition temperature (Tg) was assessed by DMTA and differential scanning calorimetry (DSC). The results showed higher tensile strength and elongation at break for IPNs than those for physical blends. The shifts of Tg for that two components that make up the IPNs were greater than those for corresponding blends. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3480–3485, 2002 相似文献
975.
Preparation and properties of ethoxylated fatty methyl ester nonionics 总被引:11,自引:0,他引:11
Ehthylene oxide (EO) cannot react directly with fatty methyl esters that have no active hydrogen. We developed a new synthetic
method, which directly inserts EO into fatty methyl esters (RCOOCH3) to give [RCO(OCH2CH2)nOCH3]. This was achieved by the use of a novel solid catalyst modified by metal cations. Ethoxylates of fatty methyl esters obtained
by this method were homogeneous monoesters and had good properties as nonionic surfactants.
Presented at the AOCS Annual Meeting & Expo in Anaheim, California, April 1993. 相似文献
976.
Summary A catalytic process for synthesis of new polyesters with methacrylate pendant groups is presented. Thus, zinc succinate catalyzed
reaction of succinic anhydride with glycidyl methacrylate (GMA) in dimethoxyethane gives linear oligoesters with low molecular
weights (1380-2400 Da). The polyester formation takes place via simultaneous ring opening of the cyclic anhydride and oxirane
units.
GMA component can be partially replaced with cyclohexeneoxide to obtain polyesters with methacrylate pendant groups in various
percentages. Nearly colorless waxy polymers are obtained in excellent yields (69–97%) within 48–60 h. at 90 °C. In the study
structure of the polymers have been elucidated by conventional spectroscopic techniques and photo-crosslinking of ability
of their thin films have been tested by monitoring intensity of methacrylate double bonds, using IR-spectrometry methodology. 相似文献
977.
Methyl Salicylate,a Soybean Aphid-Induced Plant Volatile Attractive to the Predator <Emphasis Type="Italic">Coccinella septempunctata</Emphasis> 总被引:5,自引:0,他引:5
Induced volatiles provide a signal to foraging predatory insects about the location of their prey. In Iowa, early in the growing season of soybean, Glycine max, many predacious seven-spotted lady beetles, Coccinella septempunctata, were observed on plants with heavy infestations of soybean aphid, Aphis glycines. We studied whether the attraction of this beetle is caused by the release of specific volatile compounds of soybean plants infested by aphids. Volatile compounds emitted by soybean plants infested by aphids were compared with those of undamaged, uninfested, and artificially damaged plants. Gas chromatography–mass spectrometry analyses revealed consistent differences in the profiles of volatile compounds between aphid-infested soybean plants and undamaged ones. Significantly more methyl salicylate was released from infested plants at both the V1 and V2 plant growth stages. However, release patterns of two other induced plant volatiles, (d)-limonene and (E,E)-α-farnesene, differed between the two plant growth stages. Gas chromatographic–electroantennographic detection of volatile extracts from infested soybean plants showed that methyl salicylate elicited significant electrophysiological responses in C. septempunctata. In field tests, traps baited with methyl salicylate were highly attractive to adult C. septempunctata, whereas 2-phenylethanol was most attractive to the lacewing Chrysoperla carnea and syrphid flies. Another common lady beetle, the multicolored Asian lady beetle, Harmonia axyridis, showed no preference for the compounds. These results indicate that C. septempunctata may use methyl salicylate as the olfactory cue for prey location. We also tested the attractiveness of some selected soybean volatiles to alate soybean aphids in the field, and results showed that traps baited with benzaldehyde caught significantly higher numbers of aphids. 相似文献
978.
Yomi?WatanabeEmail author Praphan?Pinsirodom Toshihiro?Nagao Takashi?Kobayashi Yutaka?Nishida Yoshiaki?Takagi Yuji?Shimada 《Journal of the American Oil Chemists' Society》2005,82(11):825-831
Acid oil is a by-product in the neutralization step of vegetable oil refining and is an alternative source of biodiesel fuel.
A model substrate of acid oil, which is composed of TAG and FFA, was used in experiments on the conversion to FAME by immobilized
Candida antarctica lipase. FFA in the mixture of TAG/FFA were efficiently esterified with methanol (MeOH), but the water generated by the esterification
significantly inhibited methanolysis of TAG. We thus attempted to convert a mixture of TAG/FFA to FAME by a two-step process
comprising methyl esterification of FFA and methanolysis of TAG by immobilized C. antarctica lipase. The first reaction was conducted at 30°C in a mixture of TAG/FFA (1∶1, wt/wt) and 10 wt% MeOH using 0.5 wt% immobilized
lipase, resulting in efficient esterification of FFA. The reaction mixture after 24 h was composed of 49.1 wt% TAG, 1.3 wt%
FFA, 49.1 wt% FAME, and negligible amounts of DAG and MAG (<0.5 wt%). The reaction mixture was then dehydrated and used as
a substrate for the second reaction, which was conducted at 30°C in a solution of the dehydrated mixture and 5.5 wt% MeOH
using 6 wt% immobilized lipase. The activity of the lipase increased gradually when the reaction was repeated by transferring
the enzyme to a fresh substrate mixture. The activity reached a maximum after 6 cycles, and the content of FAME achieved was
>98.5 wt% after a 24-h reaction. The immobilized lipase was very stable in the first-and second-step reactions and could be
used for >100 d without significant loss of activity. 相似文献
979.
Several pervaporation membranes, cellulose acetate (CA), polyvinylbutyral (PVB), poly(MMA-co-AA), MMA-AA-BA, CA/PVB blend and CA/poly(MMA-co-AA) blend, were prepared, and their pervaporation properties were evaluated by separation of methanol/C5 or methanol/MTBE (methyl tert-butyl ether). The results shows that the CA composite membrane has a high separation performance (flux Jmenthanol =350g.m-2.h-1 and separation factor a > 400) for methanol/C5 mixtures, and the pervaporation characteristics of MMA-AA-BA copolymer membranes changes with the ratio of copolymer. For CA/poly(MMA-co-AA) blend membrane, the pervaporation performance is improved in comparison with CA or poly(MMA-co-AA) membrane. From the experiment of CA/PVB blend membranes for methanol/MTBE mixture, it is found that the compatibility of blends may affect the separation features of blend membrane. 相似文献
980.
In specimens of high molecular weight poly(methyl methacrylate) the microregion at the crack tip has been investigated during fatigue crack propagation by applying the optical interference method in a specially constructed experimental set-up. Thus, in the frequency range of 0.4 to 50 Hz the size and contour of the craze zone were directly measured at upper and lower load of the cycles. In contrast to previous assumptions it is established that the maximum craze width at the crack tip and hence the maximum length of stretched fibrils increases strongly with crack propagation rate. The directly measured craze data and also the material parameters indirectly derived by the aid of the Dugdale model are related to those data which have been measured during continuous crack propagation under quasi-static tensile load. The spacings of the fatigue striations on the fracture surfaces are compared with the lengths of the craze zones. 相似文献