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排序方式: 共有883条查询结果,搜索用时 31 毫秒
1.
目的:分析血小板源性生长因子(PDGF)/蛋白激酶B(AKT)通路在压力超负荷诱导的心室重构中的作用及机制。方法:选取C57BL/6雌性小鼠55只,建立主动脉弓缩窄模型,成功建模45只,小鼠随机数字表法分为假手术组、DMSO组和实验组,假手术组小鼠开胸后逐层缝合,不进行主动脉缩窄术(TAC),开胸24 h后给予PBS溶液200 μL加DMSO 50 μL,DMSO组TAC术后24 h给予PBS溶液200 μL加DMSO 50 μL,实验组TAC术后24 h给予PBS溶液200 μL加抑制剂AG1296 50 μL,观察小鼠心功能及心肌组织病理形态。慢病毒感染建立PDGF基因不同表达人脐静脉内皮细胞(HUVEC)细胞鉴定和培养,依据细胞不同处理方式分为对照组、PDGF组、shRNA组和PDGF+IMA组,检测p-AKT及t-AKT蛋白在HUVEC细胞内表达情况。结果:DMSO组小鼠左室收缩末期容积(LVESV)、左室舒张末期容积(LVEDV)、左室收缩末期内径(LVESD)及左室舒张末期内径(LVEDD)较假手术组升高,左室射血分数(EF)、左室短轴缩短率(FS)较假手术组降低。实验组LVESV、LVEDV、LVESD及LVEDD较DMSO组降低,EF、FS较DMSO组升高,差异有统计学意义(P<0.05)。假手术组小鼠心肌组织整齐排列,间隙正常;DMSO组小鼠形态不规整,炎性细胞浸润,细胞间隙变大,胞核深染。实验组小鼠膨大或坏死细胞减少,间隙变小,炎性浸润降低。DMSO组小鼠心肌细胞横截面积较假手术组升高,实验组小鼠心肌细胞横截面积较DMSO组降低,差异有统计学意义(P<0.05)。PDGF+IMA组细胞内p-AKT及t-AKT蛋白表达较PDGF组及shRNA组显著降低,差异有统计学意义(P<0.05)。结论:PDGF可加速压力超负荷诱导心室重构,促进形成心肌组织纤维化,而抑制PDGF/AKT通路可改善心肌细胞肥大。 相似文献
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The aim of this research is to evaluate the effect of polyphosphoric acid (PPA) on the mechanical performance of styrene–butadiene–styrene (SBS) and styrene–butadiene–rubber (SBR) modified asphalt. Conventional properties, multiple stress creep recovery (MSCR), bending beam rheometer (BBR), and linear amplitude sweep (LAS) tests were conducted to evaluate the performance characteristics of asphalt at different PPA inclusions. Gel-permeation chromatography (GPC), saturates, aromatics, resins, and asphaltenes (SARA), and Fourier transform infrared (FTIR) were carried to reveal the molecular weight, component and infrared spectra of asphalt. Results showed that PPA hardened the asphalt, improved the rutting and fatigue performances of polymer modified asphalt (PMA) binder, but weakened the anti-cracking performances. Besides, storage stability had a significant improvement as the addition of PPA. The addition of PPA brought more macromolecules into asphalt and led to more high-average molecular weight compounds. Furthermore, PPA changed four component ratios of asphalt. Both PMA with or without PPA have similar absorption peaks. This may be due to absorption peak of PMA covered the changes in PPA modification process as the low content of PPA. 0.8% dosage of PPA may be considered optimum for composite modified binder combining the above experimental results for this binder source. 相似文献
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由于铸造厂制芯机器人的工作环境恶劣,机器人抓取砂芯的稳定性较差,时常出现掉砂芯、夹伤砂芯的问题。针对上述问题建立以夹持器、气压、机械振动的系统数学模型,采用高阶系统极点在[s]平面的分布法来判定该系统的稳定性。在确保高阶系统极点值不变的情况下,通过改变系统的零点值来观察零点值对系统稳定性、振荡衰减时间的影响。用Matlab的pzmap和impulse函数分别对系统的零点、极点分布和零点值的不同对系统响应进行仿真,运用仿真结果与现场试验进行优化参数,结果表明采用一种刚度与柔度各为1/2的夹持器对制芯机器人的稳定性具有较好优化效果。 相似文献
4.
《International Journal of Hydrogen Energy》2022,47(77):32969-32980
To improve the dehydrogenation/hydrogenation performance of magnesium hydride (MgH2), a nickel-vanadium bimetallic oxide (NiV2O6) was prepared by a simple hydrothermal method using ammonium metavanadate and nickel nitrate as raw materials. This oxide was used to improve the hydrogen storage performance of MgH2. NiV2O6 reacted with Mg to form Mg2Ni and V2O5; Mg2Ni and V2O5 played an important role in improving the hydrogen storage properties of MgH2. The NiV2O6-doped MgH2 had an excellent hydrogen absorption and desorption kinetics performance, and it could absorb 5.59 wt% of hydrogen within 50 min at 150 °C and release about 5.3 wt% of hydrogen within 12 min. The apparent activation energies for the dehydrogenation and hydrogenation of MgH2-NiV2O6 were 92.9 kJ mol?1 and 24.9 kJ mol?1, respectively. These were 21.7% and 66.3% lower than those of MgH2, respectively. The mechanism analysis demonstrated that the improved kinetic properties of MgH2 resulted from the heterogeneous catalysis of vanadium and nickel. 相似文献
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《Journal of Industrial and Engineering Chemistry》2014,20(2):586-590
This study was carried out to develop a carbamide-based dithiocarbamate (CDTC) chelator for the removal of heavy metal ions from wastewater. Its structural properties were characterized by FT-IR, 1H NMR and 13C NMR. Results confirmed the functional groups of HNC(S)S existed. The adsorption isotherms showed CDTC had a high adsorption capability for Zn (119.8 mg/g) and Cu (63.1 mg/g). It exhibited a distinctive selectivity for the removal of metal ions (Cu2+ > Zn2+ > Cr3+ > Pb2+ > Cd2+) as they coexisted. The influence of initial pH of wastewater for the removal efficiency of metal ions was also investigated and a pH > 7 was preferred. 相似文献
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为了增大无人机的减重效果,基于微发泡注塑成型工艺,利用Moldflow仿真软件对无人机机身进行优化分析。基于单因素试验结果,利用正交试验得到最优工艺参数组合。结果表明:单因素试验中,熔体温度、模具温度、保压压力、气体初始浓度对质量的影响较大,适当增加温度、气体初始浓度,减小保压压力可以达到减重效果。通过正交试验优化,当熔体温度为275℃,模具温度为80℃,保压压力为14 MPa,气体初始浓度为1%,无人机机身的质量为21.81 g,相比优化前降低9.58%;无人机机身的翘曲变形量降至0.289 8 mm。 相似文献
10.
To avoid template-like action of polyoxyethylene 20 cetyl ether (Brij-58) in hydrogel matrix, a polymerizable liquid crystal AAc-Brij-58 based acrylic acid (AAc) and Brij-58, and poly(NIPAm-co-AAc-Brij-58) (ACHX) hydrogels based on N-isopropylacrylamide (NIPAm) and AAc-Brij-58 were synthesized by esterification and free-radical polymerization. The chemical structures of resulting ACHX hydrogels were confirmed by FTIR and 1H NMR. The optical property of ACHX pre-polymerization solution was monitored by ultraviolet–visible spectrophotometry (UV/Vis). The pore structure was observed by scanning electron microscopy (SEM). The adsorption and desorption behaviors of Bovine Serum Albumin (BSA) were investigated by temperature-oscillating between 37 °C and 25 °C. The result shows that AAc-Brij-58 and ACHX hydrogels have been successfully synthesized. With increasing mass percent of AAc-Brij-58/NIPAm from 0 to 10 wt%, the transparency of ACH01-10 hydrogel decreases to 0 at 20, 17, 14, 12 and 16 min, respectively. The interior of ACHX hydrogels presents honeycomb structure with thick pore wall with pore size from 120 to 600 μm, but shows vent-like structure on the outer surface after copolymerization by AAc-Brij-58. The adsorption and desorption of ACHX hydrogels exhibit reversible temperature oscillation responsibility between 37 °C and 25 °C. As mass percent of AAc-Brij-58/NIPAm is 1 wt%, ACH01 hydrogel presents highest adsorbed BSA amount, about 1090 ± 24 mg/g at 37 °C. After desorption at 25 °C, columniform BSA aggregates on the surface of ACHX hydrogels were not observed. 相似文献