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61.
Yuichi Shimauchi Sachiko Ode Tsutomu Yamazaki Yuta Matsushima Kazuyuki Maeda 《Journal of Porous Materials》2010,17(3):305-312
A new vapor phase transport (VPT) technique to prepare an inverse silica replica of an ordered mesoporous carbon was developed.
Tetraethyl orthosilicate (TEOS) was infiltrated in mesoporous carbon CMK-3 as the hard template at 180 °C for 48 h under an
autogenous pressure in an autoclave in the presence of water. The samples obtained by removal of CMK-3 retained structural
regularity of CMK-3 with little shrinkage of framework, which were characterized by SAXRD, N2 adsorption, TG-DTA, and SEM. Influence of preparation temperature on the loading amount of silica was investigated. The multi-step
replication process was monitored by characterizing the replicated materials as well as intermediate composites. 相似文献
62.
Seiji Kumagai Hirotaka Ishizawa Yuta Aoki Yasuhiro Toida 《Chemical engineering journal (Lausanne, Switzerland : 1996)》2010,156(2):270-277
A molded carbon/silica composite with high micro- and mesoporosity, as well as a high bulk density, was fabricated by activating a disk-molded precursor made from carbonized rice husk (RH) and beet sugar (BS) at 875 °C in CO2. The pore structure of the RH- and BS-based carbon/silica composite (RBC) was analysed in relation to the bulk density. An activation time of 2.0 h provided the largest BET specific surface area (1027 m2/g) and total pore volume (0.68 cm3/g) and a low bulk density (0.54 g/cm3). An RBC that was first activated for 1 h was immersed again in BS syrup and then activated in CO2 for 1 h. This two-step activation process provided both a high bulk density (0.69 g/cm3) and a highly textured structure (BET specific surface area, 943 m2/g; total pore volume, 0.56 cm3/g). The immersion in BS syrup was useful for improving the texture without reducing the bulk density, in comparison to one-step activation for 1.0 h. The suspension of the RBCs was basic because of the residual inorganic compounds of potassium and calcium. However, the basicity of the suspension was alleviated by washing the RBCs with water. 相似文献
63.
Akane Samizo Makoto Minohara Naoto Kikuchi Kenta Ando Yuta Mazuka Keishi Nishio 《Journal of the American Ceramic Society》2023,106(2):1540-1546
Sn2Nb2−xTaxO7 (x = 0.0–2.0) with pyrochlore structure is a promising material for p-type oxide semiconductors. A systematic study of its Nb/Ta ratio indicated that the hole–generation efficiency of the Nb end (Sn2Nb2O7) was an order of magnitude lower than that of the Ta end (Sn2Ta2O7). Although this occurs due to differences in oxygen-vacancy formation, the origins of the hole–generation efficiencies remain unclear due to limited information on local and global crystal-structure disorders in pyrochlore Sn2Nb2O7 and Sn2Ta2O7. In this study, the crystal structures of Sn2B2O7 (B = Nb, Ta), composed of BO6 octahedra and Sn4O tetrahedra, were investigated using X-ray absorption spectroscopy and X-ray diffraction. A detailed investigation of the local and global crystal structures indicated a larger amount of disorder in the Sn4O tetrahedra in Sn2Nb2O7 compared to Sn2Ta2O7; disorder in the BO6 octahedra occurred only in Sn2Ta2O7. This study indicates that an appropriate selection of the B-site element is vital for suppressing defect and disorder formation in Sn4O tetrahedra and subsequently improving the hole–carrier–generation efficiency. 相似文献
64.
Weiyuan Lin Yoshiki Hamamoto Yuta Hikima Masahiro Ohshima 《Polymer Engineering and Science》2023,63(1):44-54
Microcellular injection molding is an attractive method. However, their surface imperfections have been a major problem hindering wide industrial applications. Several methods have been proposed to improve the surface appearance of foams. In this study, we proposed a method to improve the surface appearance of polypropylene (PP) foams from the material property perspective, especially with regard to crystallization and viscosity. The basic idea of the surface improvement is to reduce the size of bubbles generated at the flow front, delay the solidification behavior of the polymer at the mold interface, squeeze the bubbles existing at the mold–polymer interface, and redissolve the bubbles into the polymer by holding pressure. Blending a low-modulus PP delays the crystallization of the polymers at the skin layer and solidification, taking enough time to squeeze the bubbles smaller. A sorbitol-based gelling agent, bis-O-([4 methylphenyl]methylene)-D-Glucitol, was used to increase the viscosity at a low strain rate to reduce the size of the bubbles generated at the flow front during the filling stage. The foam injection molding experiments demonstrated that the proposed method effectively improved the surface appearance of the foams. In particular, the surface appearance of the foams became almost equivalent to that of solid samples using low-modulus PP. 相似文献
65.
Flow characteristics at Re = 660–3000 in a serpentine channel are measured. A scale-up model whose channel hydraulic diameter is 50 times as large as that for a proton exchange membrane fuel cell (PEMFC) is used for the measurements. The flow conditions correspond to operating conditions for PEMFCs of 25–40 cm2 at current density of 1–3 A/cm2 when the fuel utilisation ratio is 0.75 and air is used for the O2 supply. Two different porous media are used to simulate the gas diffusion layer (GDL). The results suggest that although the leakage flow rate is rather insensitive to the total flow rate, it increases significantly depending on the increase of the GDL permeability. Increasing the flow rate or the permeability enhances the sectional secondary flows and is expected to enhance mass transfer on the GDL. It is confirmed that the flow becomes turbulent around the bend even at Re = 660. 相似文献
66.
67.
Yuta Nabatame Tsuyoshi Matsumoto Yuki Ichige Takashi Komine Ryuji Sugita Masayuki Murata Yasuhiro Hasegawa 《Journal of Electronic Materials》2013,42(7):2172-2177
In this study, we have numerically analyzed the transport properties of Bi-Sb nanowires, taking into account wire boundary scattering. Wire boundary scattering slightly decreased the Seebeck coefficient of Bi-Sb nanowires. This effect is due to the observation that boundary scattering and the mobility ratio of L-point electrons to T-point holes in the nanowires are smaller than those in bulk Bi-Sb because the wire boundary scattering suppresses the mobilities of L-point electrons and heavy holes. The largest Seebeck coefficient for all wire diameters was obtained when the Sb concentration was 5 at.%. The effective mass approached zero near 5 at.% Sb, and the small effective mass led to a large subband shift in each band. Thus, a small effective mass enhances the quantum effect at a fixed wire diameter, even if wire boundary scattering is taken into account. 相似文献
68.
Kubosawa H. Higaki N. Ando S. Takahashi H. Asada Y. Anbutsu H. Sato T. Sakate M. Suga A. Kimura M. Miyake H. Okano H. Asato A. Kimura Y. Nakayama H. Kimoto M. Hirochi K. Saito H. Kaido N. Nakagawa Y. Shimada T. 《Solid-State Circuits, IEEE Journal of》1999,34(11):1619-1626
A four-way very long instruction word (VLIW), 312-MHz geometry processor with peripheral component interconnect/accelerated graphic port bus bridge was implemented in a 0.21-μm, 2.5-V, three-layer-metal CMOS process. We adopted (1) a software bypass mechanism, (2) single-instruction multiple-data stream instructions, (3) four sets of floating-point multiply add and accumulate execution units, (4) special condition code registers and a branch condition generator for a clipping operation, and (5) automatic clock delay tuning methodology. As a result of these features, we achieved a performance of 2.5 GFLOPS and 6.5 million polygons per second for a three-dimensional geometry processor, which is the highest published performance as a single geometry processor. The processor is applicable to computer-aided-design systems that require very high graphics performance 相似文献
69.
Hiroshi Yamamoto Yudai Nakamura Shigemi Moriguchi Yuki Nakamura Yuta Honda Ikumi Tamura Yoshiko Hirata Akihide Hayashi Jun Sekizawa 《Water research》2009,43(2):351-362
We selected eight pharmaceuticals with relatively high potential ecological risk and high consumption—namely, acetaminophen, atenolol, carbamazepine, ibuprofen, ifenprodil, indomethacin, mefenamic acid, and propranolol—and conducted laboratory experiments to examine the persistence and partitioning of these compounds in the aquatic environment. In the results of batch sunlight photolysis experiments, three out of eight pharmaceuticals—propranolol, indomethacin, and ifenprodil—were relatively easily photodegraded (i.e., half-life < 24 h), whereas the other five pharmaceuticals were relatively stable against sunlight. The results of batch biodegradation experiments using river water suggested relatively slow biodegradation (i.e., half-life > 24 h) for all eight pharmaceuticals, but the rate constant was dependent on sampling site and time. Batch sorption experiments were also conducted to determine the sorption coefficients to river sediments and a model soil sample. The determined coefficients (Kd values) were much higher for three amines (atenolol, ifenprodil, and propranolol) than for neutral compounds or carboxylic acids; the Kd values of the amines were comparable to those of a four-ring polycyclic aromatic hydrocarbon (PAH) pyrene. The coefficients were also higher for sediment/soil with higher organic content, and the organic carbon-based sorption coefficient (log Koc) showed a poor linear correlation with the octanol-water distribution coefficient (log Dow) at neutral pH. These results suggest other sorption mechanisms—such as electrochemical affinity, in addition to hydrophobic interaction—play an important role in sorption to sediment/soil at neutral pH. 相似文献
70.
H Eisaki H Takagi S Uchida H Matsubara S Suga M Nakamura K Yamaguchi A Misu H Namatame A Fujimori 《Canadian Metallurgical Quarterly》1990,41(10):7188-7191