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91.
The diffusion coefficients at zero penetrant concentration, D0, of n-heptane, n-heptane, n-octane, n-decane, and 2,2,4-trimethylpentane (TMP) in LDPE were obtained in the range of 25–50°C, using the desorption method. The dependence of D0 on the size and shape of the penetrant is reported. It was found that D0 decreases with increasing penetrant molecule size. The activation energies of diffusion in the temperature range of 25–50°C increase with increasing penetrant molecule size and are independent of temperature. The results are interpreted in terms of the free volume theory and semiquantitative estimates of the free volume parameters are reported. 相似文献
92.
This paper discusses a rapid GC-FID technique for the simultaneous quantitative analysis of FFA, MAG, DAG, TAG, sterols, and
squalene in vegetable oils, with special reference to palm oil. The FFA content determined had a lower SE compared with a
conventional titrimetric method. Squalene and individual sterols, consisting of β-sitosterol, stigmasterol, campesterol, and
cholesterol, were accurately quantified without any losses. This was achieved through elimination of tedious conventional
sample pretreatments, such as saponification and preparative TLC. With this technique, the separation of individual MAG, consisting
of 16∶0, 18∶0, and 18∶1 FA, and the DAG species, consisting of the 1,2(2,3)- and 1,3-positions, was sufficient to enable their
quantification. This technique enabled the TAG to be determined according to their carbon numbers in the range of C44 to C56. Comparisons were made with conventional methods, and the results were in good agreement with those reported in the literature. 相似文献
93.
Anti-Nutritional Components, Fibre, Sinapine and Glucosinolate Content, in Australian Canola (Brassica napus L.) Meal 总被引:1,自引:0,他引:1
Rodney J. Mailer Amanda McFadden Jamie Ayton Bob Redden 《Journal of the American Oil Chemists' Society》2008,85(10):937-944
Canola meal is highly regarded as a component of animal feed with a high protein content and a desirable amino acid profile.
The presence of some components, in particular glucosinolates, sinapine and fibre, affects the value of the meal and reduces
the amount that can be used in animal feed formulations. Glucosinolates in traditional cultivars (rapeseed) had very high
amounts and this severely limited the usefulness of the meal. Canola breeding programs have successfully reduced glucosinolate
content to trace amounts. However sinapine remains at levels sufficiently high to cause problems, particularly in poultry
feed. The relatively high fibre level in canola also reduces the value of the product for animal feed. This study has determined
the level of sinapine, glucosinolates and fibre in current cultivars of canola in Australia to illustrate advances made by
breeding programs and limitations which still remain to raise the usefulness of a potentially valuable feedstock. Although
glucosinolate levels in meal were shown to have been reduced to 11 μmol/g in some cases, sinapine remained at traditional
levels of about 12–15 g/kg and neutral detergent fibre levels were about 30–40%. These issues are important priorities for
canola breeders. 相似文献
94.
美国经济2009年1月正处于衰退期,而2010年似乎已进入了扩张期,这意味着经济衰退已经结束。2009年第3季度美国国内生产总值实现了自2008年第1季度以来首次增长。另外,申请失业救济人数和可用房源数量都呈下降趋势,预示着经济复苏的积极向好。美国国家经济研究局称,这也有可能是经济扩张中经济活动的短期逆转。 相似文献
95.
Bob R. Powell Vadim Rezhets Michael P. Balogh Richard A. Waldo 《JOM Journal of the Minerals, Metals and Materials Society》2002,54(8):34-38
The micro structural analysis of die-cast AE42 reveals a correlation between micro structure and creep strength. A lamellar-phase
Al11RE3, which dominates the interdendritic microstructure of the alloy, partly decomposes above 150‡C into Al2RE and Al (forming Mg17Al12). The increased solubility of aluminum in magnesium at higher temperatures may also promote the decomposition of Al11RE3. The creep strength decreases sharply with these phase changes. A mechanism for the decrease in creep strength of AE42 is
proposed whereby the reduced presence of lamellar Al111RE3 and/or the presence of Mg17Al12 contribute to the observed poor creep strength at higher temperatures. 相似文献
96.
Nicholas P. Petropolis Harrison M. Petropolis Nicole E. MacNeil Taylor M. Doucet D. Gerrard Marangoni 《Journal of surfactants and detergents》2021,24(1):51-66
The critical micelle concentrations (CMC) values and counterion dissociation (α values) have been determined for a number of mixed micellar systems consisting of two typical ionic surfactants and glycol ethers (glymes) as cosurfactants, namely diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether. Conductance experiments were used to determine the CMC and α values of the mixed micelles as a function of glyme concentration in the aqueous mixed solvent. Favorable interactions between sodium dodecyl sulfate micelles and glyme cosurfactants were deduced from the decreases in the CMC values and the large increase in the α values of these systems as a function of increasing glyme concentration in the mixed solvents. In contrast to the anionic surfactant/glyme systems, in general, there appeared to be little favorable interactions between the surfactant and glymes when micelles of the cationic surfactant dodecyltrimethylammonium bromide were formed in water/glyme solvent systems containing an increasing amount of the glymes. The interaction of glymes with the surfactant micelles was examined closely via 13C nuclear magnetic resonance (NMR) chemical shifts for both surfactant and glyme carbons; these chemical shifts changes were interpreted in terms of the distribution and the localization of the glymes in the aggregates. Finally, partition constants, determined from two-dimensional diffusion-oriented spectroscopy (2D-DOSY) experiments, were used to calculate thermodynamic quantities of transfer of the glymes between the bulk phase and the self-assembled aggregates. All these results are interpreted in terms of the key contributions that both the glyme ethoxylated groups and alkyl endgroups make to the hydrophobic interactions. 相似文献
97.
There is considerable variation in the composition of native gold and the nature of minerals co-existing with it, and this reflects differences in the geological environment and chemistry of ore-forming processes. In areas where gold-bearing mineralization is subject to active fluvial erosion, especially in temperate climatic regimes, any discrete grains of native gold pass into alluvial sediment with little modification. The chemical characteristics of alluvial grains and the nature of preserved mineral inclusions provide a signature which points back to the type of source mineralization. This signature may be established using electron probe microanalysis and scanning electron microscopy and can be interpreted to provide information about the original bedrock mineralization. Identification of the type of source mineralization using the technique at an early stage in regional exploration can help focus attention on targets with the most potential economic importance. 相似文献
98.
Neale Harrison Chek Ziu Koo Michael G. Tomlinson 《International journal of molecular sciences》2021,22(13)
The ubiquitously expressed transmembrane protein a disintegrin and metalloproteinase 10 (ADAM10) functions as a “molecular scissor”, by cleaving the extracellular regions from its membrane protein substrates in a process termed ectodomain shedding. ADAM10 is known to have over 100 substrates including Notch, amyloid precursor protein, cadherins, and growth factors, and is important in health and implicated in diseases such as cancer and Alzheimer’s. The tetraspanins are a superfamily of membrane proteins that interact with specific partner proteins to regulate their intracellular trafficking, lateral mobility, and clustering at the cell surface. We and others have shown that ADAM10 interacts with a subgroup of six tetraspanins, termed the TspanC8 subgroup, which are closely related by protein sequence and comprise Tspan5, Tspan10, Tspan14, Tspan15, Tspan17, and Tspan33. Recent evidence suggests that different TspanC8/ADAM10 complexes have distinct substrates and that ADAM10 should not be regarded as a single scissor, but as six different TspanC8/ADAM10 scissor complexes. This review discusses the published evidence for this “six scissor” hypothesis and the therapeutic potential this offers. 相似文献
99.
Bob Sabistina 《中国人造板》2008,15(5):29-30
1 美国硬木资源概况 美国硬木产品已经在整个亚洲广泛使用多年,向东南亚地区出口硬木贸易额从2001年的7700万美元上升至2005年的1亿4000万美元,而在此期间,中国市场的需求从2.3亿美元上升到4.78亿美元.中国家具业年产值达到420亿美元,产品销往国际国内两个市场. 相似文献
100.
Audrey B. Harrison Amanda J. Oliver William T. Slack Nicky M. Faucheux K. Jack Killgore Clifford A. Ochs 《河流研究与利用》2023,39(6):1084-1093
In large rivers, secondary channels occur where the main channel is divided by an instream island, forming one or multiple smaller channels outside the main channel. Secondary channels are highly variable in morphometry, flow characteristics, and degree of connectivity to the main channel. Engineered closing structures at the upstream end of most secondary channels restrict inflow from the main channel, resulting in gradients of flow connectivity among secondary channels that vary with river stage. We investigated the relationship of flow connectivity to benthic macroinvertebrate assemblage richness and structure among a series of secondary channels of the Lower Mississippi River. Samples were collected over 2 years at times of high and low river stages. We discovered (1) macroinvertebrate assemblage structure and taxonomic richness varied along the flow connectivity gradient, and (2) there was a legacy effect of prior connection on assemblage structure that lasted up to a year. We contend that for management and restoration planning aimed at conservation of large river biological diversity, an important consideration are the life history requirements of animals utilizing secondary channel habitats. 相似文献