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81.
Yutaka Kawahara Atsushi Nakayama Masatoshi Shioya Masaki Tsuji Hideki Yamane Tadahisa Iwata 《Journal of Materials Science》2012,47(4):1887-1892
Structure of poly(dioxanone) (PPDX) fibers produced through a two-step melt-spinning process with an additional short-period
annealing above the melting temperature of PPDX was investigated and the effect of annealing on the degradation behavior was
discussed. The morphological study carried out by etching the fibers using a phosphate or permanganate solution suggested
that the fibers take a skin–core structure, and both the skin layer and the core region consist of a bundle of microfibrils.
The micro-beam X-ray diffraction analysis revealed that the short-period annealing in the production process only slightly
promotes the crystallization in the skin layer but contributes to increasing the packing of amorphous chains near the skin,
which seems to be the controlling factor of the hydrolytic degradation behavior of the fibers. 相似文献
82.
Wonsang Kwon Yecheol Rho Kensuke Kamoshida Kyung Ho Kwon Youn Cheol Jeong Jonghyun Kim Hideki Misaka Tae Joo Shin Jehan Kim Kwang‐Woo Kim Kyeong Sik Jin Taihyun Chang Heesoo Kim Toshifumi Satoh Toyoji Kakuchi Moonhor Ree 《Advanced functional materials》2012,22(24):5194-5208
Low‐temperature anionic ring‐opening homopolymerizations and copolymerizations of two glycidol derivatives (allyl glycidyl ether (AGE) and ethoxyethyl glycidyl ether (EEGE)) are studied using a metal‐free catalyst system, 3‐phenyl‐1‐propanol (PPA) (an initiator) and 1‐tert‐butyl‐4,4,4‐tris(dimethylamino)‐2,2‐bis[tris‐(dimethylamino)phosphoranylidenamino]‐2Λ5,4Λ5‐catenadi(phosphazene) (t‐Bu‐P4) (a promoter) in order to obtain well‐defined functional linear polyethers and diblock copolymers. With the aid of the catalyst system, AGE is found to successfully undergo anionic ring‐opening polymerization (ROP) even at room temperature (low reaction temperature) without any side reactions, producing well‐defined linear AGE‐homopolymer in a unimodal narrow molecular weight distribution. Under the same conditions, EEGE also undergoes polymerization, producing a linear EEGE‐homopolymer in a unimodal narrow molecular‐weight distribution. In this case, however, a side reaction (i.e., chain‐transfer reaction) is found to occur at low levels during the early stages of polymerization. The chemical properties of the monomers in the context of the homopolymerization reactions are considered in the design of a protocol used to synthesize well‐defined linear diblock copolyethers with a variety of compositions. The approach, anionic polymerization via the sequential step feed of AGE and EEGE as the first and second monomers, is found to be free from side reactions at room temperature. Each block of the obtained linear diblock copolymers undergoes selective deprotection to permit further chemical modification for selective functionalization. In addition, thermal properties and structures of the polymers and their post‐modification products are examined. Overall, this study demonstrates that a low‐temperature metal‐free anionic ROP using the PPA/t‐Bu‐P4 catalyst system is suitable for the production of well‐defined linear AGE‐homopolymers and their diblock copolymers with the EEGE monomer, which are versatile and selectively functionalizable linear aliphatic polyether platforms for a variety of post‐modifications, nanostructures, and their applications. 相似文献
83.
Hirobumi Shibata Tomoaki Morita Taku Ogura Keishi Nishio Hideki Sakai Masahiko Abe Mutsuyoshi Matsumoto 《Journal of Materials Science》2009,44(10):2541-2547
Mesostructured zirconia particles having monoclinic-type crystalline walls were prepared using a low-temperature crystallization
technique. Crystalline zirconia particles with highly-ordered mesostructures were obtained through the sol–gel process of
zirconium sulfate tetrahydrate at 333 K in the presence of molecular self-assemblies of cetyltrimethylammonium bromide (CTAB)
or mixtures of CTAB and anionic molecules such as sodium dodecyl sulfate and sodium p-toluenesulfonate. Variations in the molar ratios of CTAB and the chemical species of anionic molecules led to the variations
in the periods of highly-ordered zirconia having crystalline walls. Calcination of the mesostructured zirconia particles prepared
using templates consisting solely of CTAB yielded crystalline mesoporous zirconia particles. 相似文献
84.
In this paper, photoresponsive behavior of multi-bilayered films having precisely controlled layer thickness prepared by stacking an azo-functionalized polymer liquid crystal, PMAzXAc, and polyvinyl alcohol alternatively, PVA, is described. The multi-bilayered films were found to reflect a light of specific wavelength depending on the layer thickness and refractive index, and showed the reversible change in the reflection intensity by irradiation with visible and UV lights. The change in the reflection intensity was brought about by change in the molecular orientation of PMAzXAc between an out-of-plane orientation and a photo-induced isotropic state, and was strongly dependent on the number of methylene spacer of PMAzXAc linking the azobenzene side group with the acrylate polymer main chain. PMAz6Ac with hexa-methylene spacer showed the largest change in the reflection intensity, while smaller change in the reflection intensity was observed for PMAzXAc having shorter or longer methylene spacer than 6. The effect of the methylene spacers on the photochemical change in the molecular orientation of azobenzene chromophores in the multi-bilayered films will be discussed. 相似文献
85.
Kazufumi Tsujimoto Toshinobu Sasa Kenji Nishihara Takakazu Takizuka Hideki Takano 《Progress in Nuclear Energy》2000,37(1-4):339-344
The accelerator-driven transmutation system has been studied at the Japan Atomic Energy Research Institute. This system is a hydrid system which consists of a high intensity accelerator, a spallation target and a subcritical core region. In the conceptual design study, two types of system concepts, sodium cooled and lead-bismuth cooled system, are being studied. In this study, we fucus on our lead-bismuth cooled accelerator-driven transmutation system to investigate basic characteristics. The fuel compositions were optimized for efficient transmutation of minor actinide. The transmutation of long-lived fission products was also considered. 相似文献
86.
87.
Shinzi Kato Hideki Kageyama Kazutaka Takagi Kazuaki Mizoguchi Toshiaki Murai 《Advanced Synthesis \u0026amp; Catalysis》1990,332(6):898-910
A series of sodium selenocarboxylates 2 were isolated from the reaction of diacyl selenides with sodium ethanolate and characterized. A convenient preparation of the sodium salts 2 by the direct reaction of acyl chlorides with sodium selenide was also established. The salts are colourless to slightly pale yellow crystals and labile towards moisture. They readily react with alkyl iodides at room temperature to give the corresponding Se-alkyl esters 3 . 相似文献
88.
Hideki Shige Toshitsugu Ishikawa Michio Suzukawa Masato Nishiwaki Takeshi Yamashita Kei Nakajima Toshimitsu Ito Kenji Higashi Makoto Ayaori Atsushi Yonemura Paul Nestel Haruo Nakamura 《Lipids》1998,33(12):1169-1175
The effects of vitamin E on cholesteryl ester (CE) metabolism in 1774 cells were examined. Pretreatment of 1774 cells with
vitamin E at concentrations above 50 μM significantly decreased acetylated low density lipoprotein (LDL)-induced incorporation
of [14C]oleate into CF in cells in a dose-dependent manner. This was partly due to vitamin E Also significantly inhibiting the uptake
of [3H]CE-labeled acetylated LDL by 1774 cells. A trend existed toward suppression of acyl-CoA:cholesterol acyltransferase (ACAT)
activity in the cell lysate at high vitamin E concentration, but there was no effect on hydrolysis of CE. These data indicate
that vitamin E reduces the uptake of modified LDL and suppresses ACAT activity, resulting in less cholesterol esterification
in macrophages; a novel mechanism underlying the antiatherogenic properties of vitamin E. 相似文献
89.
The differences in distribution of geometric isomers of unsaturated PC hydroperoxides generated by free radical oxidation
were compared, as corresponding hydroxy analogs, in heterogeneous liposomes and in a homogeneous methanol solution by using
HPLC with UV detection due to the presence of conjugated dienes. Identification of fractionated peak components was carried
out by GC-MS. When the oxidation of 1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphocholine, PC(16∶0/18∶2), was initiated in liposomes by a hydrophilic azo radical initiator, and in a methanol
solution by a hydrophobic azo radical initiator, there was no significant difference in the relative percentages of 1-palmitoyl-2-(9-hydroxy-trans-10,trans-12-octadecadienoyl)-sn-glycero-3-phosphocholine (9-t,t-OH PC) and 1-palmitoyl-2-(13-hydroxy-trans-9,trans-11-octadecadienoyl)-sn-glycero-3-phosphocholine (13-t,t-OH PC) between the PC oxidized in liposomes and in the methanol solution. For the oxidation of 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine, PC(16∶0/20∶4), the relative percentage of 1-palmitoyl-2-(5-hydroxy-trans-6,cis-8,11,14-eicosatetraenoyl)-sn-glycero-3-phosphocholine (5-OH PC) was significantly higher (P<0.01) than that of 1-palmitoyl-2-(15-hydroxy-cis-5,8,11,trans-13-eicosatetraenoyl)-sn-glycero-3-phosphocholine (15-OH PC) in liposomes. For the homogeneous methanol solution of PC(16∶0/20∶4), the relative percentage
of 5-OH PC was close to that of 15-OH PC. For the PC(16∶0/20∶4) oxidized in bulk with added pentamethylchromanol, the individual
amount of 15-OH PC, 1-palmitoyl-2-(11-hydroxy-cis-5,8trans-12,cis-14-eicosatetraenoyl)-sn-glycero-3-phosphocholine (11-OH PC), 1-palmitoyl-2-(12-hydroxy-cis-5,8,trans-10,cis-14-eicosatetraenoyl)-sn-glycero-3-phosphocholine (12-OH PC), 1-palmitoyl-2-(8-hydroxy-cis-5,trans-9,cis-11,14-eicosatetraenoyl)-sn-glycero-3-phosphocholine (8-OH PC), 1-palmitoyl-2-(9-hydroxy-cis-5,trans-7,cis-11,14-eicosatetraenoyl)-sn-glycero-3-phosphocholine (9-OH PC), and 5-OH PC were close to each other compared to the corresponding values in liposomes
and in methanol solution. The results obtained by gel permeation chromatography of the PC liposomes containing hydrophilic
2,2′-azobis-2-amidinopropane) dihydrochloride (AAPH) suggest that the AAPH added to the liposomes of PC(16∶0/20∶4) was partitioned
into the water phase and out of the hydrophobic region of the fatty acyl moieties of the PC. These results confirm that the
distance that exists in the bis-allylic carbons of the unsaturated fatty acyl moieties of PC from the interface between the
hydrophilic region of PC and the water phases played an important role in influencing hydrogen abstraction to form a symmetrical
distribution of hydroperoxide isomers in both the heterogeneous liposomes and the homogeneous methanol solution. 相似文献
90.
Kenji Hatanaka Masashi Katsuyama Hideki Takagi 《Journal of the American Ceramic Society》2003,86(1):135-140
The fatigue tests under push-pull completely reversed loading and pulsating loading were performed for silicon nitride ceramics at elevated temperatures. Then the effects of stress wave form, stress rate, and cyclic understressing on fatigue strength, and cyclic straining behavior, were examined. The cycle-number-based fatigue life is found to be shorter under trapezoidal stress wave loading than under triangular stress wave loading, and to become shorter with increasing hold time under the trapezoidal stress wave loading. Meanwhile, the equivalent time-based life curve, which is estimated from the concept of slow crack growth, almost agrees with the static fatigue life curve in the short and intermediate life regions, showing the small cyclic stress effect and the dominant stress-imposing period effect on cyclic fatigue life. The fatigue strength increased in stepwise stress amplitude increasing test, where stress amplitude is increased stepwise every given number of stress cycles, at 1100° and 1200°C. Occurrence of cyclic strengthening was proved through a gradual decrease in strain amplitude during a pulsating loading test at 1200°C in this material, corresponding to the above cyclic understressing effect on fatigue strength. 相似文献