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71.
Summary The ring-opening polymerization of 2-phenyl-1,3,-6,2-trioxaphosphocane (4), an eight-membered cyclic phosphonite, has been investigated. Cationic initiators of PhCH2-Cl and MeOTf gave polymers, whereas anionic and radical initiators did not yield polymer. The structure of polymer was examined by IR, 1H, 31P, and 31C NMR spectroscopy of polymers and elemental analysis as well as the alkaline hydrolysis products. The polymer consisted of two different units, i.e., the major part is the normal phosphinate structure 5 and the minor part is the isomerized unit 6 in 7% with PhCH2Cl initiation and in 34% with MeOTf initiator. The difference in nature of propagating species from these two initiators are discussed in connection with their reactivities.On leave from the Institute of Chemistry, Academia Sinica, Beijing, China 相似文献
72.
Summary The ring-opening polymerization of deoxophostone 5, a five-membered cyclic phosphinite, has been studied. Some cationic initiators gave polymer whereas anionic and radical initiators as well as metal chloride (Lewis acid) catalysts did not yield polymer. The polymer consisted of a phosphine oxide repeating unit 6. The polymerization proceeded via the Arbuzov-type reaction. The reduction of polymer 6 with a HSiCl3/Et3N system gave polyphosphine 7. 相似文献
73.
Takashi Mitamura Hiroyuki Ogino Hidehiko Kobayashi Toshiyuki Mori Hiroshi Yamamura 《Journal of the American Ceramic Society》1993,76(8):2127-2128
Preparation of BaLa2 O4 , Ba3 ,Y4 O9 , Ba ,In2 O5 , and Ba3 Ga2 O6 powders and their sintering were investigated in Ar or air. These sintered bodies with perovskite-related structure were synthesized by reaction sintering, using mixed powders in the atomic ratios of Ba/La = 1, Ba/Y = 0.75, Ba/In = 1, and Ba/Ga = 1.5. The order-disorder transition temperatures of the BaLa2 O4 , Ba3 Y4 O9 , Ba2 In2 O5 , and Ba3 Ga2 O6 sintered bodies were 270°, 350°, 880°, and 123Oo C, respectively. It was found that the temperatures were influenced by the ionic radius of cations in B sites, and the transition temperatures decreased with increasing ionic radius. 相似文献
74.
Masaaki Suzuki Yoshihisa Hasegawa Masayuki Aizawa Yoshinori Nakata Takeshi Okutani Kohei Uosaki 《Journal of the American Ceramic Society》1995,78(1):83-89
The structure of silicon carbide–silicon nitride (SiC–Si3 N4 ) composite particles synthesized using a CO2 laser was studied by magic angle spinning nuclear magnetic resonance (MAS-NMR) and electron spin resonance (ESR). The structure around Si atoms changed by introducing N. C atoms around Si were substituted by N atoms, and N-rich configurations around Si atoms increased stepwise as the N content increased. The low N content composite particles consisted of mainly SiC phase containing dissolved N. N atoms were partly present in β-SiC microcrystal and partly in the grain boundary layer in the particle. N atoms were tetrahedrally surrounded by four Si atoms in β-SiC microcrystal and were trivalent state bonded to three Si atoms in the grain boundary layer. The high N content particles consisted of SiC, Si3 N4 , and amorphous phases, whose amount depended on N content. 相似文献
75.
Summary Glow discharge polymerizations of allyltrimethylsilane (ATMS) and trimethylvinyloxysilane (TMVOS) were investigated by elemental analysis and infrared spectroscopy. The formed polymers were far different in elemental composition from the starting materials, and possessed high carbon and hydrogen contents. There was less difference in an infrared-spectral sense between the two polymers from ATMS and TMVOS. A polymer-forming process in a discharge state is discussed. 相似文献
76.
77.
Atsushi Takahashi Isao Nakamura Masaaki Haneda Tadahiro Fujitani Hideaki Hamada 《Catalysis Letters》2006,106(3-4):133-138
Catalytic hydrogenation of naphthalene to decalin was studied over a carbon-supported rhodium catalyst in supercritical carbon
dioxide solvent at 333 K, and the results were compared with those in an organic solvent. cis-, trans-Decalin and tetralin were formed from the beginning of the reaction in supercritical carbon dioxide. Higher concentration
of hydrogen in carbon dioxide solvent and on the active site, and also the suppression of desorption of partially hydrogenated
tetralin molecules from the active site would be responsible for higher selectivity to cis-decalin in supercritical carbon dioxide than that in an organic solvent. 相似文献
78.
Motoi Takahashi Toshiyuki Mori Fei Ye Ajayan Vinu Hidehiko Kobayashi John Drennan 《Journal of the American Ceramic Society》2007,90(4):1291-1294
A Pt on nano-sized CeO2 particles that in turn are supported on carbon black (CB) was synthesized using the co-impregnation method. This potential anode material for fuel cell applications was synthesized in a stepwise process. The pure CeO2 was synthesized using an ammonium carbonate precipitation method, and the Pt particles dispersed on the CeO2 in such a way that a uniform dispersion with the CB was obtained (Pt–CeO2 /CB). The electrochemical activity of the methanol (CH3 OH) oxidation reaction on the Pt–CeO2 /CB was investigated using cyclic voltammetry and chronoamperometry experimentation. The onset potential of CH3 OH oxidation reaction on the Pt–CeO2 /CB anode was shifted to a lower potential as compared with that on commercially available Pt–Ru/carbon (C) alloy anode. In addition, the activation energy of the Pt–CeO2 /CB anode was much lower than that of the Pt–Ru/C alloy anode. Moreover, the current density of the Pt–CeO2 /CB anode was much higher than that of the Pt–Ru/C alloy anode at temperatures between 28° and 60°C. These results suggest that the anode performance of the Pt–CeO2 /CB anode at the operating temperature of typical fuel cells (80°C) is superior to that of the more usual Pt–Ru/C alloy anode. Importantly, the rare metal, Ru, is not required in the present anode material and the amount of Pt required is also significantly reduced. As a consequence, we report a promising candidate Pt–CeO2 /CB composite anode for application in the development of direct methanol fuel cells. 相似文献
79.
A Sm(III) exchanged NaY zeolite prepared from aqueous SmCl3 was modified with various amounts of fluorine using NH4F. These fluorinated zeolites exhibit enhanced catalytic activity for the dealkylation of cumene. The evaluation of acid sites by infrared spectroscopy and pyridine adsorption was correlated with fluorine content. 相似文献
80.
Shigeki Habaue Momoko AsaiMasatake Morita Yoshio OkamotoHiroshi Uyama Shiro Kobayashi 《Polymer》2003,44(18):5195-5200
α-Methylenemacrolides having various groups, such as aromatic, ether, and amine, were enzymatically, anionically, and radically polymerized. The polymerization with the lipase catalyst successfully afforded polymers only through the ring-opening process, whereas the vinyl polymerizations selectively proceeded by using anionic and radical initiators. The polyesters obtained by the enzymatic polymerization have a polymerizable methacrylic methylene group in the main-chain, in addition to the aromatic and polar groups, and were further radically polymerized to quantitatively produce a cross-linked polymer gel. 相似文献