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71.
This paper describes, from the view of nuclear physics and radiochemistry, the mode of operation in doping semiconductor silicon
with phosphorus by neutron irradiation. In addition to precise control of the irradiation fluence, this includes control of
neutron-flux distribution, self-shielding and radioactive products from the silicon matrix and the surface impurities. The
accuracy of the resistivity values achieved by this method is better than ± 5% at the predicated value. The good homogeneity
of the dopant distribution is shown by the results of location-resolving resistivity measurements as well as by the breakdown
radiation emitted by diodes. Neutron-bombarded homogeneously doped silicon (NBH-silicon) is used for routine manufacture of
multi-diode vidicons and power devices. 相似文献
72.
A study of historical P inputs to Friary Lough, Co. Tyrone, Northern Ireland used a multi-sediment core approach. One of the sediment cores taken from the littoral zone at 2.5m water depth showed exceptionally high P, Fe and Mn concentrations below 20 cm sediment depth. Concentrations increased to 14 mg Pg(-1), 238 mg Feg(-1) and 35 mg Mng(-1) in the sediment profile and compared with deep basin maxima of 7 mg Pg(-1), 70 mg Feg(-1) and 2 mg Mng(-1) in surface sediments at 8.5m water depth. It is proposed that the high concentrations in the littoral zone core are due to post-depositional intrusion of chemical-rich local groundwater from soils in adjacent fields that are excessively fertilised with organic slurry. Soil analyses showed Olsen-P concentrations in these fields up to 125 mgkg(-1) at the soil surface (0-7.5 cm) and 39 mgkg(-1) in the sub-soil at 20 cm depth. We suggest that the mobilisation of P, Fe and Mn is due to leaching following P saturation and/or the loss of P absorbing chemicals due to prolonged reduction and complexing in wet soils. Further work will explore this relationship and the nature of the hydrological pathways through soil. 相似文献
73.
This paper investigated the relationship between the annual variation of the algae population and the physicochemical properties
of the water reservoired in the Gachang Dam in the hopes of serving as a guideline in the production of a clean water supply
to regions of the city of Taegu. Summer thermal stratification was formed in the freshwater reservoired in the Gachang Dam
and thus dissolved oxygen (DO) decreased according to the depth of the water. The pH of epilimnion was much higher than that
of hypolimnion in summer because of the difference in the photosynthesis rate of algae. In July, at the beginning of the rainy
season, the amount of total nitrogen (T-N) in the freshwater reached a maximum of 1.92 mg/L without an increase in the amount
of total phosphorus (T-P). In August, the concentration of T-P in the freshwater increased steeply and reached 0.12 mg/L.Aulacoseira spp. (diatoms) were predominantly distributed in the freshwater throughout the year andSynedra andAsterionella (diatoms) predominantly populated in the spring. However,Anabaena andMicrocystis (blue-green algae), which caused malodor and a bad taste, flourished predominantly in epilimnion in August when the temperature
of the water at the surface region increased to the maximum and the concentration of T-P was sufficiently high. 相似文献
74.
Alessandro Monti Eric R. Hall Mark M. C. van Loosdrecht 《Canadian Metallurgical Quarterly》2007,133(9):899-908
A long-term comparative study on the kinetics of enhanced biological phosphorus removal (EBPR) was carried out in pilot scale membrane-assisted and conventional biological phosphorus removal processes, by monitoring system performance, phosphorus mass balances, and maximum specific rates in off-line batch tests. The two systems exhibited similar performance in the removal of soluble phosphorus (P) from the influent wastewater, in the specific P release observed in the anaerobic zone, and in the maximum specific P release and volatile fatty acid (VFA) uptake rates. However, when the VFA in the influent was limiting, the conventional EBPR (CEBPR) process performed significantly better than the membrane (MEBPR) counterpart, and this behavior was also reflected in the kinetics of P release. Denitrifying dephosphatation was observed to be significant in both processes during periods of satisfactory P removal. When the aerobic recycle ratio was reduced to a minimum level, the anoxic P uptake activity in the CEBPR sludge was lower than that of the MEBPR sludge. Finally, the biomass decay rates of the two sludge types were estimated to be comparable, with significant reduction of the decay under unaerated conditions. 相似文献
75.
76.
采用盆栽实验研究石灰性土壤中磷、镉交互作用对烟草生长的影响,结果表明,磷的添加可减轻镉对烟草的危害。随着向土壤中添加磷浓度的增加,烟草生物量呈增加趋势。而当磷浓度为150mg kg-1时烟草生物量显著增加,地上部分变化比地下部分明显;而烟草中镉的含量呈先下降再增加的趋势。当镉浓度相同条件下,随着向土壤中添加磷浓度的增加,烟草中的镉含量呈现先下降再增加的趋势,高浓度镉尤为明显,在镉浓度为40mg kg-1时最为明显。研究还发现,同一磷浓度下,随着镉浓度的增加植株中磷含量呈逐渐下降趋势,此外,植株中镉含量、磷与土壤环境中磷、镉含量浓度呈显著正相关。 相似文献
77.
用15个上口面积为40m2,底部面积为20m2,深为1m的池塘,在相同的放养水平和投饲水平下,进行氮磷试验研究。本试验共设置五个处理:N/P=1,N/P=5,N/P=10,N/P=20,CK,每个处理设置3个重复。试验结果表明:试验中投放的饵料、肥料分别占氮总输入的30%~46.12%和37.81%~39.52%;占磷总输入的15.44%~74.74%和16.31%~79.12%。在支出项目中,鱼类的收获支出的氮磷占氮磷总输入的52.31%~75.95%和8.98%~40.39%;沉积在底泥中的氮磷分别占氮磷总输入的19.95%~36.3%和35.82%~86.52%;底泥中氮磷的渗漏占其总输入的1.49%~12.66%和1.09%~11.28%,其中氮的损失率对照最低为1.49%,N/P=20的损失最高为12.66%;磷的损失率N/P=10的处理最低为1.09%,对照为最高11.28%。 相似文献
78.
《Journal of Great Lakes research》2023,49(1):268-275
Vital to the Lake Superior food web, the amphipod Diporeia remains the dominant macroinvertebrate in Lake Superior despite drastic population declines throughout the rest of the Laurentian Great Lakes. Diporeia is most abundant in the slope region of the lake at water depths between 30 and 125 m. It has been hypothesized that this depth range is preferred because of elevated primary production and deposition within this zone. This hypothesis of food driving habitat preference has not been directly tested. Here we used 120-hour preference-avoidance trials to record Diporeia choice of sediments from different water depths, seasons, and other treatments. Most preferences were weak to absent; however, Diporeia strongly preferred sediment from 30- and 60-m water depths over deeper or shallower sites. Contrary to the hypothesis about food driving habitat choice, chemical characteristics did not explain this strong preference. Grain size variation was the only measured variable that was consistent between the sites preferred by Diporeia and different from unpreferred sites. Both the 30- and 60-meter sites contained predominantly medium silt but had a wider range in grain sizes. These results indicate that physical habitat characteristics may have a stronger bearing on Diporeia habitat preference than food availability and may account for their distribution in the lake. The results also may imply that the role of dreissenid mussels as ecosystem engineers altering sediment physical characteristics may be important where they are abundant. 相似文献
79.
80.
Phosphorus recovery from the biomass ash: A review 总被引:1,自引:0,他引:1
Biomass ash, generated during the thermal chemical conversion of biomass for energy production, is an industrial by-product which is often recognized as a solid waste, but there are some useful elements in the biomass ash such as phosphorus, etc. So through some technology and methods, the biomass ash can be transferred into a useful resource. The paper mainly includes the following aspects: biomass ash composition characteristics, biomass thermal chemical conversion for phosphorus and phosphorus recovery technology from biomass ash. Through these aspects literature review, not only the whole biomass ash characteristics was made clear, but also we think that the idea of phosphorus from biomass ash is feasible, especially for some high phosphorus ash such as sludge ash, meat and bone meal (MBM) ash, etc. So the review about phosphorus from the biomass ash is very important practical significance for biomass energy, biomass ash disposal and phosphorus resource. 相似文献