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991.
双氧水改性二氧化钛的光催化性能研究 总被引:1,自引:0,他引:1
研究了用微乳法制备纳米二氧化钛粉末的工艺,以及在紫外光照射下,TiO2和H2O2分别以及两者结合对于甲基橙溶液的降解作用。结果表明用微乳法可以制备粒度为23.2nm的纳米TiO2粉末;在紫外光照射下,H2O2可以有效地降解甲基橙溶液;当H2O2浓度从1mmol/L增加到10mmol/L,甲基橙的吸光度直线下降;当H2O2浓度达到10mmol/L时,降解率可以达到99%;TiO2也可以有效地降解甲崔橙溶液,当TiO2的浓度为0.50~0.75g/L时,降解率最大;用H2O2对TiO2进行改性后,可以有效地降解甲基橙溶液,固定TiO2的量为0.5g/L时,当H202浓度为4mmol/L时,甲基橙溶液的吸光度达到最低;当H2O2浓度处于10mmol/L以上时,甲基橙溶液的吸光度却出现无规则的变化。 相似文献
992.
993.
针对目前存在的一些对焊接残余应力形成机制和消除原理传统理论的质疑和不同观点,采用两端拘束杆件和长板各焊接的一维简化模型,分析比较了经受加热与冷却热循环以及直接从高温冷却下来时的应变历史和残余应力产生的机制。结果表明,前者存在残余压缩塑性应变,后者存在残余热收缩应变。两者对产生残余应力的作用完全是等价的,为了统一概念,建议引入固有应变理论。固有应变包括焊接过程中产生的塑性应变,热应变和相变应变,残余应力是在固有应变源作用下构件自动平衡的结果,消除焊接残余应力必须去除固有应变源,此外对若干容易混淆的问题进行了讨论。 相似文献
994.
纳米CeO2单晶的制备与热处理对粒径的影响 总被引:1,自引:0,他引:1
以Ce(NO3)3·6H2O为铈源、NH3·H2O为沉淀剂,用化学沉淀法通过对陈化时间的控制,制备了单分散的单晶纳米CeO2粒子,并用XRD、TEM、ED、BET、TG-DTA等测试手段对产物的物相结构、形貌和纳米尺度进行了表征.XRD分析表明,制得的纳米CeO2粒子为萤石结构且晶型比较完整. 通过控制热处理的温度和陈化时间可以控制粒子的大小.TEM和ED分析表明产物颗粒基本为球形,分散性较好且为单晶. 通过TG-DTA结果可以断定所制备的前驱体结构式为CeO2·1/2H2O. 相似文献
995.
996.
Lead-based paints and primers have long been used to protect steel structures from corrosion, but are now recognized as environmental
hazards. During lead-based paint removal via abrasive blasting, federal, state and local environmental requirements mandate
the use of containment structures to prevent contamination of air, soil, or water. The thermal spray vitrification (TSV) process
was developed and optimized in laboratory experiments to remove hazardous lead-based paint. TSV consists of thermal spraying
a molten glass onto the painted surface. As the glass strikes the substrate, it reacts with the paint, and organic components
are pyrolyzed, while lead ions are trapped on the glass surface. Quenching stresses in the glass cause it to crack and spall
off the substrate. The resulting glass fragments are collected, and further remelted to completely immobilize lead (Pb) ions
in the glassy iron (Fe) silicate matrix. The glass waste is thus rendered non-hazardous, as determined by the Toxicity Characteristic
Leaching Procedure (TCLP). The TSV process was field tested on a fire hydrant, using minimal personal protective equipment
and without using a containment structure. The lead-containing paint was removed, without producing hazardous waste, leaving
de-painted surfaces suitable for repainting. 相似文献
997.
998.
Attila Diószegi 《中国铸造》2007,4(3):210-214
The thermal conductivity or diffusivity of pearlitic grey irons with various carbon contents is investigated by the laser flash method. The materials are cast in controlled thermal environments and produced in three dissimilar cooling rates. The cooling rate together with the carbon content largely influence the thermal conductivity of grey iron. Linear relationships exist between the thermal conductivity and the carbon content, the carbon equivalent and the fraction of former primary solidified austenite transformed into pearlite. The work shows that optimal thermal transport properties are obtained at medium cooling rates. Equations describing the thermal conductivity of pearlite,solidified as pre-eutectic austenite, and the eutectic of grey iron are derived. The thermal conductivity of pearlitic grey iron is modeled at both room temperature and elevated temperature with good accuracy. 相似文献
999.
Five new heat treatment processes were designed, which were divided into three groups by their characteristics. The microstructures and mechanical properties of the alloy after the five heat treatments and thermal exposure at 500, 550℃ for 100 h were tested. The results indicate that a little differences exist in the performance of mechanical properties at room-temperature after the five heat treatments, and the thermal stability is the key factor for determining heat treatment process. Among the three groups of heat treatment processes, the best thermal stability is achieved after the first group of heat treatment. After annealing treatment at intermediate temperature, some defects and uneven grain boundaries are remained, which leads to the reduction fractions of precipitations on unit grain boundary and the harmful effect of precipitations on grain boundary is weakened. The process of annealing at 650 ℃for 4 h is recommended the best heat treatment process for Ti40 alloy. 相似文献
1000.
W.F. Wu Y.H. Feng X.X. Zhang 《金属学报(英文版)》2006,19(4):244-250
A mathematical model has been built to numerically predict the thermal history of thin slab during CSP (compact strip process) rolling. To estimate the temperature distribution in the slab mare accurately, the mathematical model combines heat transfer in the slab, in the roll, and at the roll-slab interface during bite. The numerical results agree with on-site running data, which proves the reliabili~, of the mathematical model. The results show that roll chilling has a significant effect on the temperature distribution in the slab. 相似文献