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71.
72.
To improve water lubrication of ceramics at a lower sliding velocity, the effect of the addition of silane coupling agents was investigated. Si3N4 and Al2O3 were slid against themselves in water with and without the addition of silane coupling agents in amounts ranging from 0.05 to 0.10 mol/l. Silane coupling agents containing one or more amino groups were effective in reducing the friction of Si3N4 and Al2O3 in water. Si3N4 also showed significant wear reduction but not Al2O3. However, the addition of a silane coupling agent containing an epoxy group increased both friction and wear of Si3N4. Improved lubricative characteristics of Si3N4 in water and in silane coupling agent solutions were obtained when Si3N4 contained smaller amounts of sintering additives. The adsorption behaviour of a silane coupling agent on ceramics was examined using both Fourier transform infrared spectroscopy and thin layer chromatography to clarify the interaction between the silane coupling agent and the ceramics. The role of polysiloxane film formation on ceramics is discussed to demonstrate the lubrication properties of ceramics. 相似文献
73.
Kaori Takemura Rina Watanabe Ryuji Kameishi Naoya Sakaguchi Hiroyuki Kamachi Atsushi Kume Ichirou Karahara Yuko T. Hanba Tomomichi Fujita 《Microgravity science and technology》2017,29(6):467-473
The photosynthetic and anatomical responses of bryophytes to changes in gravity will provide crucial information for estimating how these plant traits evolved to adapt to changes in gravity in land plant history. We performed long-term hypergravity experiments at 10g for 4 and 8 weeks using the moss Physcomitrella patens with two centrifuges equipped with lighting systems that enable long-term plant growth under hypergravity with irradiance. The aims of this study are (1) to quantify changes in the anatomy and morphology of P. patens, and (2) to analyze the post-effects of hypergravity on photosynthesis by P. patens in relation to these changes. We measured photosynthesis by P. patens for a population of gametophores (e.g., canopy) in Petri dishes and plant culture boxes. Gametophore numbers increased by 9% for a canopy of P. patens, with 24–27% increases in chloroplast sizes (diameter and thickness) in leaf cells. In a canopy of P. patens, the area-based photosynthesis rate (A canopy) was increased by 57% at 10g. The increase observed in A canopy was associated with greater plant numbers and chloroplast sizes, both of which involved enhanced CO2 diffusion from the atmosphere to chloroplasts in the canopies of P. patens. These results suggest that changes in gravity are important environmental stimuli to induce changes in plant growth and photosynthesis by P. patens, in which an alteration in chloroplast size is one of the key traits. We are now planning an ISS experiment to investigate the responses of P. patens to microgravity. 相似文献
74.
The gaseous products generated by the flaming combustion of ten kinds of synthetic polymers and a kind of wood (cedar) under the same conditions (sample weight, 0.1 g; temperature, 700°C air flow rates, 50 and 100 l./hr) were quantitatively analyzed by infrared spectrophotometry, gas chromatography, and colorimetric tube method. The main hydrocarbons generated were methane, ethylene, and acetylene. The amount of acetylene generated by the flaming combustion of polymers was much larger than the amount of acetylene formed by pyrolysis at 700°C in nitrogen. Acetylene increased in quantity with increasing air. For nitrogen compounds, hydrogen cyanide was generated from every polymer containing nitrogen used, but ammonia was detected only for nylon 66 and polyacrylamide. Nitrogen monoxide and nitrogen dioxide were detected only in small amounts. Nitrous oxide was detected in the gaseous products generated by the nonflaming combustion of urea resin and melamin resin. It was also found that about 70% of the nitrogen in N-66 and PAA was converted into nitrogen gas (N2) by combustion under the conditions described above. 相似文献
75.
The spherulitic morphology in poly(butylene succinate-co-butylene carbonate)/poly(l-lactic acid) (PEC/PLLA) blends was investigated by atomic force microscopy (AFM) to obtain direct evidence for the formation of interpenetrated spherulites (IPS), where the spherulites of PEC penetrate into PLLA spherulites. The observation actually revealed that PEC crystals penetrated into interfibrillar regions of edge-on lamellae in a PLLA spherulite. The penetration process was also investigated by AFM with a temperature controller. An edge-on PLLA lamella or a fibril that ran nearly perpendicular to the growth direction of a PEC spherulite obstructed the growth of PEC spherulite. The PEC crystals filled the blocked space after growing around the PLLA lamella. These results showed that the spherulites of PEC and PLLA grow on the same layer instead of forming a layered structure of two spherulites. All the results supported the formation of IPS. 相似文献
76.
Summary First and second generation chiral dendrimers P-1G1, P-2G1, P-1G2 and P-2G2 containing chiral bisphosphine as a core were synthesized via a reaction of chiral bisphosphine compound (S,S)-1 with benzyl ether dendrons. This is the first example of chiral dendrimers containing chiral phosphorus atoms. To investigate
the effect of chiral phosphorus atoms on their conformations, optically inactive dendrimer P′-2G1 was synthesized as well using optically inactive initiator 1′ which was the mixture of rac-1 ((S,S)-1 and (R,R)-1) and meso-1. Their structures were characterized by 1H, 13C, 31P NMR, and HRMS. According to CD measurement, optically active dendrimers exhibited the Cotton effect induced by the chirality
of phosphorus atoms, while optically inactive dendrimer P′-2G1 showed no Cotton effect. 相似文献
77.
Swelling and phase equilibria of polymer networks in a low molecular mass liquid crystal (LC) have been investigated as a function of network nematicity. LC networks with varying nematicity were prepared by copolymerization of mixtures of mesogenic monomers and non-mesomorphic (styrene) monomers with various compositions. Molar fraction of mesogenic monomer (x) in copolymer network strongly influences the swelling behavior as well as the nematic-isotropic (N-I) transitions in both dry and swollen states. The swollen networks of sufficiently high x with strong nematicity exhibit a sharp N-I transition and simultaneously undergo a discontinuous change in gel volume, i.e. volume phase transition. Meanwhile, the swollen networks of x≤0.8 with less nematicity show a broad N-I transition, and the resulting volume change proceeds continuously over a finite temperature range. When x decreases further down to less than 0.5, the nematicity of the dry networks vanishes. The nematic ordering in the swollen copolymer networks of x<0.5 occurs at the same temperature as the N-I transition temperature of the pure nematic solvent (TNIS), which yields the inflection in the swelling-temperature curve. A mean field theory considering network nematicity as a variable describes the effects of x on volume phase transition such as a shift of TNIG and a change in the magnitude of volume transition, apart from the emergence of continuous volume transition due to the broad N-I transition. The purely isotropic network of x=0 appreciably swells in the nematic solvent. The solvent inside the gel forms the nematic phase at the temperatures below which conflicts with the classical theoretical prediction that nematic ordering of LC solvent in fully swollen isotropic network never occurs. 相似文献
78.
Akihiko Sugai Rie Sakuma Ikuko Fukuda Norio Kurosawa Yuko H. Itoh Kazuo Kon Susumu Ando Toshihiro Itoh 《Lipids》1995,30(4):339-344
The major ether-type lipid structures ofSulfolobus acidocaldarius (ATCC33909) were composed of caldarchaeol and calditoglycerocaldarchaeol. However, the characterization by nuclear magnetic
resonance spectroscopy and mass spectrometry showed that the structure of calditol in calditoglycerocaldarchaeol is not nonitol,
2-(1′,2′,3′-trihydroxypropyl)1,2,3,4,5,6-hexahydroxyhexane, but 2-hydroxymethyl-1-(2,3-dihydroxypropoxy),2,3,4,5-cyclopentanetetraol
with an ether linkage in the molecule. Such an intermolecular ether linkage was resistant, to BCl3 treatment, but nonresistant to 57% HI degradation treatment conducted at 100°C for 60 h, producting 2-hydroxymethyl-1,2,3,4,5-cyclopentanepentaol
from calditol as reaction product. Further, it was confirmed that the structure of calditol is essentially a derivative of
glycerol, and hydrocarbon chains were conjugated to the glycerol-like site in the structure. The calditol with an ether linkage
in the molecule suggested an important role regarding the properties of heat-resistance and acid-resistance observed inSulfolobales.
Presented at the international workshop on “Molecular Biology and Biotechnology of Extremophiles and Archaebacteria,” Wako,
Japan, August 1993. 相似文献
79.
Tumula Venkateshwar Rao Yuko Uchimaru Jun-ichi Sugiyama Kazuhiko Takeuchi 《Polymer》2005,46(23):9736-9741
Treatment of a dihydrosilane (methylphenylsilane, 1) with mixtures of a diyne (p- or m-diethynylbenzene, 2a or 2b) and a triyne (1,3,5-triethynylbenzene, 3a or B,B′,B″-triethynyl-N,N′,N″-trimethylborazine, 3b; 1:2:3=100:95:5, 100:90:10, 100:80:20) in the presence of Pd-PCy3 (Cy=cyclohexyl) catalyst gave new crosslinked silylenedivinylene polycarbosilanes. In TGA the resulting crosslinked polymers tended to show higher Td5 values and higher char yields than the corresponding linear polymers. On the other hand, UV/vis absorption spectra of the crosslinked polymers obtained in the reactions of 2a or 2b with 3a exhibited increased broad peaks around 390 nm for 2a or 360 nm for 2b. Coincidently, their fluorescence spectra showed significant increase of the emission peaks in 400-550 nm. The crosslinked polymer derived from 2a and 3b, however, showed decrease of the absorption peak around 390 nm and profound depression of fluorescence peaks in 400-550 nm. 相似文献
80.