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121.
Marioara Nechifor 《Designed Monomers and Polymers》2016,19(2):161-171
Two novel diacid-based monomers have been synthesized by anchoring a benzylideneacetophenone (chalcone) moiety through an amide or ester bridge at the fifth position of the isophthalic acid ring. Two series of new polyamides bearing chalcone side chains were prepared by direct polycondensation reaction of the aforementioned dicarboxylic acids and various aromatic diamines in N-methyl-2-pyrrolidinone, using triphenyl phosphite and pyridine as condensing agents. Their molecular structure and the basic properties were investigated by nuclear magnetic resonance, Fourier-transform IR and UV–vis spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and wide-angle X-ray diffraction. The inherent viscosity, molecular weights measurements (by gel permeation chromatography), water uptake, and solubility tests completed the research study. Introduction of the rigid and bulky chalcone units into the polymer side chains improved remarkably the solubility of the aromatic polyamides, endowed them with an amorphous nature, good thermal stability, and photosensitivity. The resulting polymers were obtained in good yields, inherent viscosities varied between 0.49 and 0.86 dL/g, and their relative high molecular weights conferred them film-forming properties. They were soluble in amide-type polar solvents, such as N,N-dimethylformamide, dimethyl sulfoxide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone. These polyamides had glass transition temperatures between 219 and 264 °C, and 10% weight loss temperatures in the range of 394–436 °C and around 50% residue at 700 °C in nitrogen atmosphere. The polyamides underwent a [2 + 2] photocycloaddition reaction upon UV light irradiation both in solution and film state in the absence of a photoinitiator or photosensitizer. The polymer films became insoluble in solvents as a result of the crosslinking . 相似文献
122.
文中应用煤岩学方法 ,对霍林河煤田具代表性的 17号煤层的显微煤岩特征进行了系统研究 ,阐述了不同组分分布特征及其变化规律 ,并指出了煤的加工利用方向 相似文献
123.
In this study, the synthesis, morphology, and thermal properties of new poly(ether imide)/titania nanohybrid films were investigated. The novel diamine containing functional nitrile groups was prepared in two steps by the nucleophilic substitution reaction and it was fully characterized by different techniques. Reaction of this diamine with pyromellitic dianhydride and 4-aminobenzoic acid gave poly(ether imide) with carboxylic acid end groups. This acid functionalized poly(ether imide) was condense with different amount of TiO2 nanoparticles to provide organic-inorganic bonding, and the flexible films of these hybrid were prepared. The obtained materials were characterized by Fourier transform-infrared spectroscopy, thermogravimetry analysis (TGA), differential scanning calorimetry, X-ray powder diffraction, UV–Vis spectroscopy, field emission-scanning electron microscopy, and transmission electron microscopy (TEM) techniques. TEM of the nanohybrid films with 12% of TiO2 contents confirms well dispersion of nanoparticles in the polymer matrix. TGA data indicated that the thermal behavior of the hybrid materials was increased with an increasing the content of TiO2 nanoparticles. The tensile stress–strain of the hybrids was investigated and the resulting nanocomposites showed good mechanical properties. The permeability and selectivity of the PEI/TiO2 membranes as a function of the titania weight percentage were study and the results indicated that the permeabilities of CO2 and N2 increase with increasing the titania content. 相似文献
124.
The novel solid acid with both sulfonic and carbonyl acid groups has been synthesized from 3-((2-sulfoethoxy) carbonyl)acrylic acid and tetraethyl orthosilicate (TEOS). The catalytic activities were investigated through the acetalization. The results showed that the novel solid acid was very efficient for the reactions with the high yields. The high acidity, high stability and reusability were the key feature of the novel solid acid. Moreover, the sulfonic and carbonyl acid groups could cooperate during the catalytic process, which improved its catalytic activities. The catalyst shows recyclability, and hold great potential for replacement of homogeneous catalysts. 相似文献
125.
采用溶液缩聚法将活性端基为TPC的液晶聚合物与对羟基偶氮苯磺酸反应制得端基为磺酸基的遥爪主链液晶离聚物.利用红外光谱分析对其结构进行了表征,采用偏光显微镜、示差扫描量热仪和广角X射线衍射等手段对其液晶性能进行了表征.结果表明:各离聚物与原没有加入离子单体的聚合物具有相同的织构,均为向列型液晶.对于同一链段长度的聚合物,当引入离子单体的含量增加时,液晶性逐渐消失;各液晶离聚物的介晶转变温度Tc和熔点Tm随着离子加入量的增加略有增加,但Tg降低. 相似文献
126.
从分析IPTV频道切换时间的制约因素出发,研究了IPTV的网络结构和使用协议,并提出了通过对接入网结构的改造:WDM-PON混合组网方式,IGMP协议的修改,以及相邻组播组加入/离开方式,达到对IPTV频道切换时间的改进. 相似文献
127.
目前,测定柴油十六烷值的试验机价格较高,现有十六烷指数预测精度低,为满足炼油厂生产柴油在线调合的需要,迫切需要建立预测精度高的柴油十六烷值预测模型。基于450个具有代表性的柴油样本,建立了柴油理化性质、烃族组成与十六烷值数据库;进而采用逐步回归分析方法,应用统计产品和服务解决方案(SPSS)软件,建立了基于柴油理化性质的十六烷值预测模型和基于柴油烃族组成的十六烷值预测模型。采用F检验、T检验、残差分析验证了上述模型的有效性,并通过计算均方根误差,比较了上述两个模型的精度,结果表明,两种预测模型均有效,基于理化性质模型的预测精度优于基于烃族组成的模型。 相似文献
128.
129.
节杆菌LF-Tou2葡萄糖基转移酶是控制絮凝剂聚糖合成的酶。通过对细胞超声破碎使酶释放,经Sephadex G200凝胶色谱和DEAE-Sepharose Fast Flow离子交换色谱对酶进行了纯化。对酶学特性进行了分析,并用5种化学修饰剂对酶分子中5种不同氨基酸残基与催化活性之间的关系进行了研究。结果表明:该酶的分子质量为14315Da;样品中w(α-螺旋)=31.7%,w(β-转角)=34.1%,w(无规卷曲)=34.2%。Km为2.752μmol,Vmax为58.056μmol/min;Mn2 是酶活性强有力的激活剂,Fe2 次之。酪氨酸和二硫键是酶分子的结构基团,色氨酸、巯基和组氨酸是酶活力的必需基团,在必需基团中色氨酸最关键。 相似文献
130.