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121.
B. K. Sarkar A. S. Verma R. C. Gupta K. Singh 《International Journal of Thermophysics》2010,31(3):620-629
Using photoacoustic spectroscopy, the composition-dependent absorption coefficient (α), thermal diffusivity (σ), and optical bandgap (E
g) of Zn1−x
Mn
x
Te diluted magnetic semiconductor have been measured. For higher Mn compositions, the absorption spectrum of the Zn–Mn–Te
system consists of three regions, viz., the high absorption region, the exponential region, and the weak absorption tail.
The bandgap follows a nonlinear variation with composition, showing a downward bowing with a minimum around x = 0.31 as a consequence of the electro-negativity difference between the substituted atoms. The composition-dependent band-edge
effective mass of the carriers does not show the bowing behavior indicating that the momentum matrix is not the same for all
the Zn1−x
Mn
x
Te alloys due to different lattice constants. The absorption spectra show that the transition is allowed and direct. 相似文献
122.
Prof. Dr.-Ing. F. Taegen Prof. Dr.-Ing. S. P. Verma Prof. Dr.-Ing. R. Walczak 《Electrical Engineering (Archiv fur Elektrotechnik)》1990,73(5):293-298
Übersicht Zur Ermittlung der wichtigsten Radialkraftwellen wird anhand der in Teil 1 ausgeführten Feldberechnung eine Übersicht über die Polpaarzahlen und Frequenzen der Oberfelder erstellt. Das sich hieraus ergebende Tonfrequenzspektrum wird mit experimentellen Untersuchungen an einem 22kW-Reluktanzmotor verglichen. Die ungleichmäßige Nutteilung des Dämpferkäfigs ergibt ein dichtes Frequenzspektrum, das in Verbindung mit mechanischen Eigenfrequenzen zu hohen Geräuschpegeln führt.
Teil 1 erschien Arch. Elektrotech. 73 (1990) 253–260 相似文献
Electromagnetic noise of reluctance machines with segmental-rotor. Part 2: Radial electromagnetic force waves and noise
Contents A survey is made on the basis of the field calculation performed in part 1 of the numbers of pole-pairs and frequencies of the harmonic magnetic fields in order to find out the most important radial force waves. The resulting audio frequency spectrum is compared to experimental investigations of a 22 kW-reluctance motor. The unequal slot pitch of the squirrel-cage damper results in a dense frequency spectrum which, in connection with the mechanical natural frequencies, causes high noise levels.
Teil 1 erschien Arch. Elektrotech. 73 (1990) 253–260 相似文献
123.
Seema Verma S. D. Pradhan Renu Pasricha S. R. Sainkar P. A. Joy 《Journal of the American Ceramic Society》2005,88(9):2597-2599
Nanosized NiZn ferrite powder is synthesized by a low-temperature method, using a unique combination of citric acid and glycine. An appropriate molar ratio of both citric acid and glycine offers a low-temperature synthetic route by incorporating the complexation behavior of citric acid and the combustion nature of glycine. Thermal decomposition/controlled autocatalytic combustion of the composite gel occurs at a low temperature of around 175°C, with the evolution of a large amount of gases. Transmission electron microscopic studies showed that the average particle size of the ferrite obtained is ∼2.5 nm, with a narrow size distribution. Uniformly distributed fine-grained microstructure with low porosity is obtained for a sample sintered at 1000°C. 相似文献
124.
Using the principle of geochemistry of fluoride, green and cost effective anion adsorbents were developed for the removal of F? from water systems. The scheme was further applied for the removal of NO3? also. Carboxymethylated starch functionalized through network formation with acrylamide was used as adsorbent, and the resultant hydrogels were loaded with Fe2+ ions to generate anchorage for the anions. Sorption of Fe2+ was studied as a function of different factors such as time, temperature, pH, and ion strength. The network having the highest Fe2+ uptake was loaded with the Fe2+ ions under optimum conditions and used for the sorption of F? and NO3?. High efficiency has been observed for F?, as even up to 100% uptake has been observed within just 10 minutes. The support shows high selectivity for NO3?, which was used as anion reference. Thermodynamics of sorption confirms low order and low energy processes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 相似文献
125.
126.
Changhua Cao Yanping Ding Xiuge Yang Jau-Jr Lin Hsin-Ta Wu Verma A.K. Jenshan Lin Martin F. O K.K. 《Solid-State Circuits, IEEE Journal of》2008,43(6):1394-1402
A fully integrated dual-conversion transmitter chain with an on-chip dipole antenna and an integer-N synthesizer operating in the 24-GHz Instrument, Scientific and Medical (ISM) band was fabricated in 0.13-mum CMOS. The choice of 24-GHz operation enables the integration of a 4-mm long antenna on chip. The transmitter chain can support data rate of 100 Mb/s. It provides 6-dBm output power to a 100-Omega load at 22.4 GHz with 152-mW power dissipation including that of a frequency synthesizer. At this output power level, the dual conversion architecture can mitigate the VCO pulling even when an antenna and a power amplifier are integrated on the same substrate as the VCO. The out-of-band emissions due to the modulation side lobes and image have been sufficiently suppressed. The stray emissions of local oscillator can also be reduced using circuit techniques. The signal from the transmitter has been picked up 95 meters away with a horn antenna, which suggests that wireless communications between a single chip radio and a base station 100 meters away is possible. 相似文献
127.
128.
B Das K Ramakrishna G D Verma R S Tiwari O N Srivastava 《Bulletin of Materials Science》1991,14(3):585-592
The second generation of high temperature superconductors typified by Bi2Sr2Ca
n−1Cu
n
O2n+4 and Tl2Ba2Ca
n−1Cu
n
O2n+4 exhibits curious structural properties which have direct relevance to the superconducting behaviour particularly transition
temperature (T
c
). The present paper reports on investigations of structural properties at microlevel in Bi-bearing HTCS. We have found curious
structural characteristics which manifests itself in the form of transformation froma
p
×a
p
×c to (2)1/2
a
p
×(2)1/2
a
p
×c through the loss of calcium atoms and the formation of five-fold modulated phase alongb through the loss of Ca and Sr atoms. We have also found the evidence of high periodicities (n=4) Bi2Sr2Ca3Cu4O12. The microstructural characteristics of HTCS showing the higherT
c
(R=0) ∼ 120 K exhibits unusual characteristics. 相似文献
129.
Rupesh Verma Ravi KumarDevesh M. Pandey Nishith Verma 《Chemical Engineering and Processing: Process Intensification》2010
A hydrodynamic study was carried out on our patented radially cross-flow fluidized bed staged column, with the salt laden water and solid resins flowing counter-currently, to determine the loading/flooding criterion for a stable operation of the column, and also to ascertain the mal-distribution in flow. Residense time distribution measurements were taken to address the latter part of the study. The data collected from the hydrodynamic measurements show a wider range of liquid and solid flowrates that can be used for the stable operation of the column, in comparison to that obtained in the conventional multi-staged column. The extent of mal-distribution or channeling is also relatively smaller in the former. The observations are consistent with the mass-transfer results obtained in our recent study, where the separation of dissolved solids using the radially cross-flow ion exchange column was found to be 40% larger than that in the conventional column. 相似文献
130.
Pradeep Ilayaperumal Praveena Chelladurai Karthik Vairan Pooja Anilkumar Balajothi Balagurusamy 《大分子材料与工程》2023,308(4):2200553
Synthetic polymer materials have been surged to the forefront of research in the fields of tissue engineering, drug delivery, and biomonitoring in recent years. Biodegradable synthetic polymers are increasingly needed as transient substrates for tissue regeneration and medicine delivery. In contrast to commonly used polymers including polyesters, polylactones, polyanhydrides, poly(propylene fumarates), polyorthoesters, and polyurethanes, biodegradable polyphosphazenes (PPZs) hold great potential for the purposes indicated above. PPZ's versatility in the synthetic process has enabled the production of a variety of polymers with various physico-chemical, and biological properties have been produced, making them appropriate for biomedical applications. Biocompatible PPZs are often used as scaffolds in the regeneration of skeleton, bones, and other tissues. PPZs have also received special attention as potential drug vehicles of high-value biopharmaceuticals such as anticancer drugs. Additionally, by incorporating fluorophores into the PPZ backbone to produce photoluminescent biodegradable PPZs, the utility of polyphosphazenes is further expanded as they are used in tracking the regeneration of the target tissue as well as the fate of PPZ based scaffolds or drug delivery vehicles. This review provides a summary of the evolution of PPZ applications in the fields of tissue engineering, drug delivery, and bioimaging in recent 5 years. 相似文献