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101.
The isotopic exchange has been studied between catalyst radiosulfur and H2S, formed in thiophene hydrodesulfurization (HDS) (named S-displace) on alumina supported molybdena, on CoMoOx, PdMoOx, PtMoOx and on silica–alumina supported NiWOx. S-displace was compared with radiosulfur exchange data between catalyst radiosulfur and gas phase H2S (Sexc) determined previously. The extent of Sexc was higher than that of the S-displace for Mo, CoMo in and NiW, whereas the extent of S-displace from PdMoO and PtMoO was
significantly higher, than that of Sexc. Thiophene HDS product distribution data are discussed in terms of increased C=C hydrogenation and C–C hydrogenolysis activity,
explained by increasing H2S production with longer circulation time of the thiophene/H2 mixture, The C1/C3<1 ratios among C4-hydrogenolysis products indicate some coke formation. The decrease of thiophene HDS activity is presumably a consequence
of increasing site-blocking with the formation of more H2S and coke with longer duration of thiophene treatment. 相似文献
102.
Nitrogen use efficiency by maize as affected by a mucuna short fallow and P application in the coastal savanna of West Africa 总被引:1,自引:0,他引:1
B.?FofanaEmail author A.?Tamélokpo M.?C.?S.?Wopereis H.?Breman K.?Dzotsi R.?J.?Carsky 《Nutrient Cycling in Agroecosystems》2005,71(3):227-237
Maize is the primary food crop grown by farmers in the coastal savanna region of Togo and Benin on degraded (rhodic ferralsols), low in soil K-supplying capacity, and non-degraded (plinthic acrisols) soils. Agronomic trials were conducted during 1999–2002 in southern Togo on both soil types to investigate the impact of N and P fertilization and the introduction of a mucuna short fallow (MSF) on yield, indigenous N supply of the soil, N recovery fraction and internal efficiency of maize. In all plots, an annual basal dose of 100 kg K ha–1 was applied to the maize crop. Maize and mucuna crop residues were incorporated into the soil during land preparation. Treatment yields were primarily below 80% of CERES-MAIZE simulated weather-defined maize yield potentials, indicating that nutrients were more limiting than weather conditions. On degraded soil (DS), maize yields increased from 0.4 t ha–1 to 2.8 t ha–1 from 1999 to 2001, without N or P application, in the absence of MSF, with annual K application and incorporation of maize crop residues. Application of N and P mineral fertilizer resulted in yield gains of 1–1.5 t ha–1. With MSF, additional yield gains of between 0.5 and 1.0 t ha–1 were obtained at low N application rates. N supply of the soil increased from 10 to 42 kg ha–1 from 1999 to 2001 and to 58 kg N ha–1 with MSF. Application of P resulted in significant improvements in N recovery fraction, and greatest gains were obtained with MSF and P application. MSF did not significantly affect internal N efficiency, which averaged 45 kg grain (kg N uptake)–1. On non-degraded soils (NDS) and without N or P application, in the absence of MSF, maize yields were about 3 t ha–1 from 1999 to 2001, with N supply of the soil ranging from 55 to 110 kg N ha–1. Application of 40 kg P ha–1 alone resulted in significant maize yield gains of between 1.0 (1999) and 1.5 (2001) t ha–1. Inclusion of MSF did not significantly improve maize yields and even reduced N recovery fraction as determined in the third cropping year (2001). Results illustrate the importance of site-specific integrated soil fertility management recommendations for the southern regions of Togo and Benin that consider indigenous soil nutrient-supplying capacity and yield potential. On DS, the main nutrients limiting maize growth were N and probably K. On NDS, nutrients limiting growth were mainly N and P. Even on DS rapid gains in productivity can be obtained, with MSF serving as a means to allow farmers with limited financial means to restore the fertility of such soils. MSF cannot be recommended on relatively fertile NDS. 相似文献
103.
The viscosity of an optical fibre over 1000–1150 °C is studied by inscribing an optical fibre Bragg grating that can withstand temperatures up to 1200 °C and monitoring fibre elongation under load through the Bragg wavelength shift. This optical interrogation offers high accuracy and reliability compared with direct measurements of elongation, particularly at lower temperatures, thus avoiding significant experimental error. An excellent Arrhenius fit is obtained from which an activation energy for viscous flow of Ea = 450 kJ mol?1 is extracted; addition of an additional temperature-dependent pre-exponential does not change this value. The log plot of viscosity is found overall to be consistent with that reported in the literature for silica measurements on rods and beams, but substantially higher than past work reported for optical fibres. The annealing and strain temperatures for an optical fibre were derived as 1114 °C and 1010 °C. However, it is shown that, because regenerated gratings already involve a post-annealing process at higher temperature, the structures are equilibrated and much more relaxed compared with normal fibres, making viscosity measurements meaningful. This work highlights the need to stabilize components for operation in harsh environments before their application, despite some mechanical compromise. Given the increasing expectation of all-optical waveguide technologies operating >1000 °C, the need to study the behaviour of glass over the long term brings added significance to the basic understanding of glass in this regime. 相似文献
104.
105.
Nguyen Tam Nguyen TruongWoo Kyoung Kim Chinho Park 《Solar Energy Materials & Solar Cells》2011,95(1):167-170
The use of inorganic nano-semiconductor/polymer blend as the active layer for organic bulk hetero-junction solar cell is an alternative to change and improve the device characteristics and performance. Effects of CdSe/P3HT composition in the blend and its loading amount in the solvent on the electrical and structural properties of active layers formed were investigated. The results of atomic force microscopy study indicated that the surface roughness of composite active layer could be controlled below 10 nm for the entire range of composite loading amount investigated in this study. The transmission line method experiments have demonstrated that the electrical percolation pathways could be developed at the critical loading amount of CdSe/P3HT composite, resulting in the abrupt decrease of sheet resistance and significant increase in the power conversion efficiency of ITO/PEDOT:PSS/(CdSe/P3HT)/Al solar cell. 相似文献
106.
The feasibility of using graphite foam as a heat sink and heat spreader in optoelectronic packages is assessed. A “supercooler” is designed, fabricated, and tested to verify its cooling capability under high heat flux conditions in a typical optoelectronic package. The supercooler uses graphite foam as a primary heat transfer material. Water is soaked into the graphite foam, and under evacuated pressure, boiling is initiated under the heating region to provide enhanced cooling. Experiments were conducted for a heat flux of up to 400 W/cm2 deposited over a heating area of 0.5 mm × 5 mm. Two-dimensional transient temperature distributions were recorded using a high-speed infrared camera. Data were obtained for steady heating, and for periodic heating with frequency up to 8 Hz. Results show that the supercooler is very efficient in dissipating heat away from the heating region. The average cooling rate during the cooling period exceeds 170 K/s. 相似文献
107.
A-Ping Zhang Bai-Ou Guan Xiao-Ming Tao Hwa-Yaw Tam 《Photonics Technology Letters, IEEE》2002,14(4):489-491
The spectral characteristics of superstructure fiber Bragg gratings are analyzed numerically based on the coupled mode theory, simultaneously taking into account the counterdirectional guided mode coupling, codirectional and counterdirectional claddings mode coupling. The theoretical results were compared with experimental data and very good agreement was obtained 相似文献
108.
Honorine Angue Mintsa Gilles Roy Cong Tam Nguyen Dominique Doucet 《International Journal of Thermal Sciences》2009,48(2):363-371
This paper presents effective thermal conductivity measurements of alumina/water and copper oxide/water nanofluids. The effects of particle volume fraction, temperature and particle size were investigated. Readings at ambient temperature as well as over a relatively large temperature range were made for various particle volume fractions up to 9%. Results clearly show the predicted overall effect of an increase in the effective thermal conductivity with an increase in particle volume fraction and with a decrease in particle size. Furthermore, the relative increase in thermal conductivity was found to be more important at higher temperatures. Obtained results compare favorably with certain data sets and theoretical models found in current literature. 相似文献
109.
Mitsutoshi Miyasaka Hiroyuki Hara Hiroki Takao Simon Tam Rob Payne Prem Rajalingham Satoshi Inoue Tatsuya Shimoda 《Journal of the Society for Information Display》2005,13(3):187-191
Abstract— Thin‐film transistors (TFTs) are field‐effect transistors that can be used to create large‐scale‐integrated (LSI) circuits. The combination of high‐performance TFTs and transfer technology of the TFTs has the potential to foster the rise of a new flexible microelectronics industry. This paper discusses the current status of flexible microelectronics, using a TFT fingerprint sensor (FPS) as an example. Technology used in active‐matrix displays can easily be applied to the TFT FPS. TFT technology should not be confined to the display industry; its use should be expanded into the semiconductor industry. With the result presented in this paper, we declare a new era of flexible microelectronics open. 相似文献
110.
Influence of the thermal effect on the TEM00 mode output power of a laser-diode side-pumped solid-state laser 总被引:11,自引:0,他引:11
A fraction of pump power has been converted to TEM(00) mode laser power for a side-pumped solid-state laser by use of a space-dependent rate equation. We investigated the pump-to-mode (TEM(00)) ratio when scaling laser-diode side-pumped solid-state lasers to high-power levels by including the thermal effect in the space-dependent rate equation. Based on the assumption that Gaussian pump power is the same at any cross section of a laser rod, we resolved the output power with a space-dependent rate equation; temperature distribution in the laser rod was obtained; the optical path difference distribution was derived, and we estimated the diffraction losses that result from thermally induced spherical aberration by use of the Strehl intensity ratio. We determined that thermally induced diffraction losses are strongly dependent on pump power and on the pump-to-mode ratio. 相似文献