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61.
Th. Braun M. Wohlers T. Belz G. Nowitzke G. Wortmann Y. Uchida N. Pfänder R. Schlögl 《Catalysis Letters》1997,43(3-4):167-173
The influence of fullerenes and related support materials on the structural and catalytic properties of ruthenium was investigated.
Catalysts based on C60, raw fullerene black, extracted fullerene black, cathode deposit and graphite were prepared by an impregnation/activation
procedure with Ru3CO12. The local co-ordination sphere of the resulting highly dispersed X-ray amorphous ruthenium was investigated by means of
EXAFS. The dominating role of the presence of non-six-membered carbon rings on the structure and the stability of the Ru particles
will be illustrated.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
62.
Pekka Manninen Päivi Laakso Heikki Kallio 《Journal of the American Oil Chemists' Society》1995,72(9):1001-1008
This study demonstrates the usefulness of capillary supercritical fluid chromatography (SFC) for the characterization of triacylglycerols
of edible oils and fats. Triacylglycerols were separated according to the acyl carbon number and the degree of unsaturation
on a 25% cyanopropyl/25% phenyl/50% methylpolysiloxane stationary phase. Valuable information concerning the triacylglycerol
composition of berry oils was obtained, despite the overlapping of certain triacylglycerol peaks. Simultaneous analysis of
fat-soluble vitamins and triacylglycerols is not practical by capillary SFC with flame-ionization detection because of the
low concentration of naturally-occurring fat-soluble vitamins in edible oils. Therefore, higher loading of the sample, which
led to overloading of triacylglycerols, was required to get reasonable peaks for fat-soluble vitamins. The method was applied
to the characterization of triacylglycerols and tocopherols in sea buckthorn pulp and seed oil, and cloudberry seed oil without
any sample purification prior to SFC. In addition, the stationary phase proved useful for separating the more complex mixtures
of triacylglycerols found in milk fat and in fish oil. 相似文献
63.
H. Purnama F. Girgsdies T. Ressler J.H. Schattka R.A. Caruso R. Schomäcker R. Schlögl 《Catalysis Letters》2004,94(1-2):61-68
Steam reforming of methanol for production of hydrogen can be carried out over copper based catalyst. In the work presented here, the catalytic properties of a CuO/ZrO2 catalyst (8.5wt%) synthesised by a templating technique were investigated with respect to activity, long term stability, CO formation, and response to oxygen addition to the feed. The results were obtained using a fixed bed reactor and compared to a commercial methanol synthesis catalyst CuO/ZnO/Al2O3. It is shown that, depending on the time on stream, the temporary addition of oxygen to the feed has a beneficial effect on the activity of the CuO/ZrO2 catalyst. After activation, the CuO/ZrO2 catalyst is found to be more active (per copper mass) than the CuO/ZnO/Al2O3 system, more stable during time on stream (measured up to 250h), and to produce less CO. Structural characterisation by means of X-ray powder diffraction (XRD) and X-ray absorption spectroscopy (XAS) reveals that the catalyst (as prepared) consists of crystalline, tetragonal zirconia with small domain sizes (about 60Å) and small/disordered crystallites of CuO. 相似文献
64.
The single NO bond in various ethers derived from 1-hydroxybenzo(d)-1,2,3-triazoles is reduced at mercury cathodes in a 2-electron process giving rise to the non-substituted benzotriazole and a corresponding primary alcohol. Controlled-potential electrolysis actually resulted in isolating the products of the above type eg benzotriazole and 2-piperidinoethanol. Cathodic reduction of non-substituted benzotriazole in acid media proceeds evidently via a chemical reaction between benzotriazole and hydrogen obtained by the catalytic reduction of hydrogen ions at the mercury electrode. 相似文献
65.
Jeannette Aumo Johanna Lilja Päivi Mäki-Arvela Tapio Salmi Mats Sundell Hanna Vainio Dmitry Yu. Murzin 《Catalysis Letters》2002,84(3-4):219-224
A polymer-supported Pd catalyst was investigated in hydrogenation of citral (3,7-dimethyl-2,6-octadienal), which is a stereoisomer with an isolated and a conjugated double bond as well as a carbonyl group. The catalyst was a fibrous polymer-supported catalyst modified with functional groups and immobilized metals. A comparison of the polymer-supported catalyst with conventional catalysts was made. 相似文献
66.
Thomas Bürgi Fachri Atamny Axel Knop‐Gericke Michael Hävecker Thomas Schedel‐Niedrig Robert Schlögl Alfons Baiker 《Catalysis Letters》2000,66(3):109-112
The adsorption of ethyl pyruvate on Pt(111) has been studied by in situ XANES measurements in the presence and absence of
hydrogen. Depending on the hydrogen and ethyl pyruvate pressure, the C and O K‐edge spectra exhibit distinctly different angular
dependence. Without hydrogen ethyl pyruvate is oriented preferentially perpendicular to the surface, indicating bonding via
the O lone pairs. In the presence of hydrogen the mean orientation is more tilted towards the surface. Likely, ethyl pyruvate
also interacts with Pt via its π system under these conditions. The observed angle‐dependent shift of the energy of the π*
and σ* resonances indicates the coexistence of differently adsorbed ethyl pyruvate species. The experimental findings demonstrate
the importance of the in situ approach for unraveling the adsorption mode of ethyl pyruvate in the enantioselective hydrogenation
over cinchona‐alkaloid‐modified Pt.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
67.
Häfliger P Agorastos N Spingler B Georgiev O Viola G Alberto R 《Chembiochem : a European journal of chemical biology》2005,6(2):414-421
The potential of certain Auger electron emitting nuclides for systemic radiotherapeutic applications has recently gained much attention. In particular, the ability of several nuclides, including 111In, 125I, and 123I, to induce DNA double-strand breaks (dsb), a good indicator of cytotoxicity, has been extensively studied. However, this ability has never previously been shown experimentally for 99mTc, which, besides the well-known gamma radiation that is used for diagnostic applications, also emits an average of 1.1 conversion electrons and 4 Auger or Coster-Kronig electrons per decay. Owing to the short range of Auger electrons, the radionuclide needs to be located very close to the DNA for dsb to occur. We synthesized two cationic 99mTcI-tricarbonyl complexes with pendant DNA binders, pyrene and anthraquinone. The X-ray crystal structures of the two complexes could be elucidated. Linear dichroism and UV/Vis spectroscopy revealed that the complex with pyrene intercalates DNA with a stability constant, K, of 1.1 x 10(6) M(-1), while the analogous complex with anthraquinone interacts with DNA in a groove-binding mode and has an affinity value of K=8.9 x 10(4) M(-1). We showed with phiX174 double-stranded DNA that the corresponding 99mTc complexes induce a significant amount of dsb, whereas non-DNA-binding [TcO4]- and nonradioactive Re compounds did not. These results indicate that the Auger electron emitter 99mTc can induce dsb in DNA when decaying in its direct vicinity and this implies potential for systemic radiotherapy with 99mTc complexes. 相似文献
68.
Wey Yang Teoh Frans Denny Rose Amal Donia Friedmann Lutz Mädler Sotiris E. Pratsinis 《Topics in Catalysis》2007,44(4):489-497
A comparative photocatalytic analysis was carried out on TiO2 made in a Flame Spray Pyrolysis (FSP) process and flame-made Degussa P25. Both have similar crystallinity, phase composition,
phase segregation and a non-porous surface. Hence comparison was made based on their difference in specific surface area,
organic adsorption and the amount of OH• generated upon illumination. The photocatalytic activity tests were carried out using
the following series of organic compounds: sucrose, glucose, fructose, maleic acid, glyoxylic acid, oxalic acid, isobutyric
acid, phenol and methanol. FSP-made TiO2 outperformed P25 for saccharides mineralisation, while for phenol and methanol mineralisation P25 was better than FSP-made
TiO2. Similar mineralisation rates were observed for both FSP-made and P25 TiO2 for the mineralisation of carboxylic acids. This shows that the relative performance of the photocatalysts depends on the
type of organic compounds to be degraded. The high surface area and possibly a more efficient interfacial charge transfer
of FSP-made TiO2 provided an efficient pathway for saccharides mineralisation. As for phenol and methanol, the mineralisation rates were higher
when using P25 due to the greater amount of OH• radicals generated by this photocatalyst. The fast mineralisation rates of
carboxylic acids made degradation of these organic compounds to be less affected by the TiO2 photocatalyst properties and conditions tested in this work. 相似文献
69.
Yang Qin Frieder Jäkle 《Journal of Inorganic and Organometallic Polymers and Materials》2007,17(1):149-157
The binding of Lewis bases to organoboron polymeric Lewis acids has been studied and the parameters that determine the complexation
equilibrium have been investigated, which include (i) the strength of the individual Lewis acids and Lewis bases, (ii) concentration,
and (iii) temperature. While the strongly Lewis acidic borane polymers poly(4-bis(pentafluorophenyl)borylstyrene) (PS-BPf) and poly(4-(di-2-thienylboryl)styrene) (PS-BTh) form isolable complexes with strong Lewis bases such as 4-t-butylpyridine (tPy), a temperature dependent equilibrium is established with weaker bases such as THF. Similarly, the weakly Lewis acidic
boronate polymer poly(4-diethoxyborylstyrene) (PS-BOEt) undergoes a temperature dependent equilibrium with the strong Lewis base 4-dimethylaminopyridine (DMAP), while poly(4-pinacolatoborylstyrene)
(PS-BPin) does not significantly bind to pyridine bases. Decomplexation of PS-BTh·
t
Py is achieved by treatment with the stronger Lewis acid, B(C6F5)3, thereby confirming the reversible nature of the polymeric Lewis acid–base adducts.
This paper is dedicated to Professor Ian Manners in gratitude of his guidance throughout the years and recognition of his
scientific accomplishments 相似文献
70.
Engagement in virtual worlds has become pervasive, particularly among the young. At the same time, the number of virtual environments has increased rapidly. Due to intensifying competition, promoting sustained usage, i.e. continuance, has become a top priority for virtual world operators. Prior research has shown that network externalities play a key role in the adoption of communication technologies. However, a small amount of research has examined the role of network externalities in continued IT usage in general or with respect to the virtual world participation in particular. To fill in this gap, we examine how perceived network externalities affect the continuance of social virtual worlds. To this end, we introduce the concept of perceived aggregate network exposure (PANE). We extend the original information systems (IS) continuance model with perceived enjoyment and position PANE as a moderator. We test the model with data collected from 2134 Finnish Habbo Hotel users and employ structural equation modelling in the analysis. The results demonstrate that PANE moderates the influence of motivational factors on continued use intention and satisfaction. 相似文献