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991.
Effect of agglomeration during coprecipitation: Delayed spinellization of magnesium aluminate hydrate 总被引:1,自引:0,他引:1
Soumen Pal A. K. Bandyopadhyay S. Mukherjee B. N. Samaddar P. G. Pal 《Bulletin of Materials Science》2010,33(4):451-456
Precipitation of magnesium aluminate hydrate with faster addition of ammonia at desired pH causes agglomeration. Agglomerated
powder, without any further treatment, on calcination forms intermediate compounds at low temperatures (≤ 900°C). The intermediate
compounds on further heat treatment (≥ 1000°C) decompose into MgO, MgAl2O4 and α-Al2O3. Effect of agglomeration and absorption of foreign ions such as Cl−, SO42−, and NH4+ in complex compounds probably cause loss of Al3+ and Mg2+ ions during heat treatment, and stoichiometry changes. Powders prepared by continuous method with better control of process
parameters than batch process yields better spinellization. 相似文献
992.
This paper compares the important mechanical properties and the electrical conductivities from room temperature to 800 °C of four LaCoO3 based cobaltite compositions with 0, 20, 40 and 55% Ca2+ ions substituted on the A site of the perovskite structure respectively. Ca2+ doped lanthanum cobaltite materials are strong candidates for use as cathodes in lower temperature solid oxide fuel cells operating at or below 800 °C. Among these four cobaltite compositions, two (LaCoO3 and La0.8Ca0.2CoO3) were found to be phase pure materials, whereas the remaining two compositions (La0.6Ca0.4CoO3 and La0.45Ca0.55CoO3) contained precipitation of secondary phases such as CaO and Co3O4. The mechanical properties of the four compositions, in terms of Young's modulus, four-point bending strength and fracture toughness measurements, were measured at both room temperature and 800 °C. At room temperature, doping with Ca2+ was found to substantially increase the mechanical properties of the cobaltites, whereas at 800 °C the pure LaCoO3 composition exhibited higher modulus and strength values than La0.8Ca0.2CoO3. All of the four compositions exhibited ferroelastic behavior, as shown by the hysteresis loops generated during uniaxial load-unload compression tests. Electrical conductivity measurements showed the La0.8Ca0.2CoO3 composition to have the highest conductivity among the four compositions. 相似文献
993.
Troy B. Holland Umberto Anselmi-Tamburini Dat V. Quach Tien B. Tran Amiya K. Mukherjee 《Journal of the European Ceramic Society》2012,32(14):3667-3674
Recent investigations regarding the role of applied fields on the grain growth and densification behavior of ionic ceramics are providing strong insights into the efficacy of Field Assisted Sintering Technique (FAST), aka Spark Plasma Sintering (SPS). Explanations of the observed behaviors, such as grain growth suppression and densification enhancement, are based upon the conjectured presence of a Joule heating driven temperature differential between grain interfaces and grain cores. These differentials were thought to be responsible for providing increased densification rates and lower densification temperatures through grain growth suppression and/or increased local kinetics at the forming necks. In this paper, we analyze the energetic, thermal, and practical details of this process in the context of the commonly accepted stages of sintering. 相似文献
994.
Beverley M. Dancy Dr. Nicholas T. Crump Daniel J. Peterson Dr. Chandrani Mukherjee Dr. Erin M. Bowers Dr. Young‐Hoon Ahn Dr. Minoru Yoshida Dr. Jin Zhang Dr. Louis C. Mahadevan Dr. David J. Meyers Dr. Jef D. Boeke Dr. Philip A. Cole 《Chembiochem : a European journal of chemical biology》2012,13(14):2113-2121
Histone acetyltransferase enzymes (HATs) are important therapeutic targets, but there are few cell‐based assays available for evaluating the pharmacodynamics of HAT inhibitors. Here we present the application of a FRET‐based reporter, Histac, in live‐cell studies of p300/CBP HAT inhibition, by both genetic and pharmacologic disruption. shRNA knockdown of p300/CBP led to increased Histac FRET, thus suggesting a role for p300/CBP in the acetylation of the histone H4 tail. Additionally, we describe a new p300/CBP HAT inhibitor, C107, and show that it can also increase cellular Histac FRET. Taken together, these studies provide a live‐cell strategy for identifying and evaluating p300/CBP inhibitors. 相似文献
995.
Jay Prakash Verma Siddhartha Singh Moushumi Ghosh Pramod Kumar Srivastava 《International Journal of Food Science & Technology》2010,45(2):319-326
Limonin is a highly oxygenated triterpene derivative of class of limonoids which causes delayed bitterness in citrus. Pseudomonas putida (P. putida) is able to reduce 47% and 63% of limonin from juice serum extract and standard limonin, respectively. Biochemical studies with P. putida indicate that probably two metabolic pathways viz. 17‐dehydrolimonoid and deoxylimonoid pathway exists in the test organism. Experimental results indicate that the enzyme limonoate dehydrogenase which is found to be localized in periplasmic space of P. putida plays a major role in conversion of limonin to 17‐dehydrolimonoate A‐ring lactone. Enzymatic studies have shown a 72% reduction in limonin. The experimental results show 9 folds reduction in limonin content in presence of NAD as cofactor. The molecular weight of one of its polypeptide is found to be 66 kDa. The optimum pH and temperature for enzyme activity is 8.5 and 30 °C, respectively. 相似文献
996.
Satyabati Das Siddhartha Das Karabi Das 《Journal of Materials Engineering and Performance》2013,22(11):3357-3363
The effect of variation of transmission ratio (r) in the pulverisette-4 (P4) ball-milling machine on the synthesis of Y2W3O12 is reported. Y2O3 and WO3 powders have been milled in a P4 planetary ball mill with different r values, i.e., ?1.5, ?1.75, ?2, ?2.25, ?2.75, and ?3, at a disk revolution speed of 300 rpm for 10 h with toluene as the process control agent. Differential thermal analysis results suggest that the reaction temperature of as-mixed powder is 1000 °C. It decreases down to 845 °C with an increase in the r value up to ?2.25. However, a further increase in the r value results in an increase in the reaction temperature. The average particle size for different r values varies in similar manner and it is found to be around 65 nm for r = ?2.25. XRD analysis of 10 h milled powders with the r value of ?2.25, heat treated at different temperatures confirms the formation of Y2W3O12 at 800 °C. The low temperature synthesis leads to retention of finer grain size and hence, helps in good densification and sinterability. The above material shows a negative thermal expansion coefficient of the order of ?7.1 × 10?6/°C in the temperature range 150-650 °C. 相似文献
997.
k-essence scalar field models are usually taken to have Lagrangians of the form L = −V (φ)F(X) with F some general function of X = ▿
μ
φ▿
μ
ϕ. Under certain conditions, this Lagrangian can take the form of that of an oscillator with time-dependent frequency. The
Ermakov invariant for a time-dependent oscillator in a cosmological scenario then leads to an invariant quadratic form involving
the Hubble parameter and a logarithm of the scale factor. In principle, this invariant can lead to further observational probes
for the early Universe. Moreover, if such an invariant can be observationally verified, then the presence of dark energy will
also be indirectly confirmed. 相似文献
998.
We have extended a first principles tight-binding total energy model to include magnetic correlations. We have tested the
validity of the model against ab-initio calculations for bcc and fcc Fe. We find that our model can quantitatively describe the pressure dependence of magnetic moments
and magnetization energy for bcc and fcc Fe. Moreover, in fcc Fe with increasing pressures it is able to capture the transitions
from ferromagnetic to non-collinear spin to antiferromagnetic and finally to the non-magnetic state. PACS numbers: 71.55 Ak,
64.30 +t.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
999.
K. Viswanath Jayanta Mukherjee P. K. Biswas R. N. Pal 《Signal, Image and Video Processing》2010,4(2):129-144
Wavelet to DCT transcoding provides inter-operability between standards using the two transforms for encoding. Transcoding
in transform domain avoids inverse transform and re-transform operations and saves computation. In this paper, we propose
new algorithms for transcoding wavelet coefficients to block DCT coefficients. In the first step, the wavelet coefficients
are transformed into upsampled DCT coefficients. Subsequently, these trans-formed coefficients are synthesized in the block
DCT space for transcoding. The proposed approach restricts all operations in the DCT domain that makes filtering involved
in the synthesis process computationally efficient. The proposed technique could be used by the block DCT based services when
the input is available as wavelet coefficients. 相似文献
1000.
Low-Noise Mid-Wavelength Infrared Avalanche Photodiodes 总被引:1,自引:0,他引:1
Siddhartha Ghosh Shubhrangshu Mallick Koushik Banerjee Christoph Grein Silviu Velicu Jun Zhao Don Silversmith Jean Baptist Rodriguez Elena Plis Sanjay Krishna 《Journal of Electronic Materials》2008,37(12):1764-1769
Mid-wavelength infrared (MWIR) p
+–n
−–n
+ avalanche photodiodes (APDs) were fabricated using two materials systems, one with mercury cadmium telluride (HgCdTe) on
a silicon (Si) substrate and the other with an indium arsenide/gallium antimonide (InAs/GaSb) strained layer superlattice
(SLS). Diode characteristics, avalanche characteristics, and excess noise factors were measured for both sets of devices.
Maximum zero-bias resistance times active area (R
0
A) of 3 × 106 Ω cm2 and 1.1 × 106 Ω cm2 and maximum multiplication gains of 1250 at −10 V and 1800 at −20 V were measured for the HgCdTe and the SLS, respectively,
at 77 K. Gains reduce to 200 in either case at 120 K. Excess noise factors were almost constant with increasing gain and were
measured in the range of 1 to 1.2. 相似文献