全文获取类型
收费全文 | 2490篇 |
免费 | 163篇 |
国内免费 | 57篇 |
专业分类
电工技术 | 8篇 |
综合类 | 107篇 |
化学工业 | 1484篇 |
金属工艺 | 66篇 |
机械仪表 | 33篇 |
建筑科学 | 38篇 |
矿业工程 | 10篇 |
能源动力 | 32篇 |
轻工业 | 199篇 |
水利工程 | 2篇 |
石油天然气 | 37篇 |
武器工业 | 7篇 |
无线电 | 181篇 |
一般工业技术 | 266篇 |
冶金工业 | 146篇 |
原子能技术 | 36篇 |
自动化技术 | 58篇 |
出版年
2024年 | 6篇 |
2023年 | 36篇 |
2022年 | 80篇 |
2021年 | 96篇 |
2020年 | 58篇 |
2019年 | 54篇 |
2018年 | 38篇 |
2017年 | 63篇 |
2016年 | 95篇 |
2015年 | 66篇 |
2014年 | 91篇 |
2013年 | 153篇 |
2012年 | 125篇 |
2011年 | 150篇 |
2010年 | 114篇 |
2009年 | 143篇 |
2008年 | 136篇 |
2007年 | 142篇 |
2006年 | 143篇 |
2005年 | 118篇 |
2004年 | 114篇 |
2003年 | 121篇 |
2002年 | 104篇 |
2001年 | 62篇 |
2000年 | 70篇 |
1999年 | 46篇 |
1998年 | 59篇 |
1997年 | 32篇 |
1996年 | 33篇 |
1995年 | 22篇 |
1994年 | 20篇 |
1993年 | 35篇 |
1992年 | 18篇 |
1991年 | 18篇 |
1990年 | 5篇 |
1989年 | 9篇 |
1988年 | 3篇 |
1987年 | 6篇 |
1985年 | 8篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有2710条查询结果,搜索用时 15 毫秒
161.
豫西熊耳山区是一个在中新生代伸展构造背景中形成的拆离- 变质核杂岩构造。其核部由新太古界太华群变质岩系和燕山期重熔型花岗岩体组成,盖层主要由中元古界熊耳群火山岩系组成。滑脱拆离系包括位于太华群和熊耳群之间的主滑脱拆离带和盖层中一系列次级滑脱断层。区内金银矿化在空间分布上受到变质核杂岩构造的控制,成矿时代与变质核杂岩主要形成期一致,成矿过程和拆离断层的发展过程一致。拆离断层控矿体系可分为6 种基本控矿构造类型,其中以产于拆离带附近的陡倾斜蚀变破碎带和爆破角砾岩筒最重要。根据以上认识,近年来已发现多处具有中大型矿床前景的金银多金属矿产地 相似文献
162.
通过对2-甲基-8-(2-吡啶基)苯并呋喃[2,3-B]吡啶辅助配体进行修饰,在吡啶的4号位引入吸电子基团苯基,并对其进行全氘代,同时对5-甲基-2-对甲苯基吡啶主配体的两个甲基进行全氘代,分别合成了两种铱磷光配合物Ⅳ和Ⅳ-d20,采用元素分析、质谱和核磁共振氢谱对其结构进行了表征与确认。利用UV-Vis 光谱、荧光发射光谱(PL)和循环伏安法对其光物理性质及能级结构进行了研究。结果表明:铱配合物的Ⅳ和Ⅳ-d20光致发光光谱发射波长分别为546.85nm和548nm;它们的HOMO和LUMO能级分别为-5.237ev和-2.645ev、-5.082ev和-2.50ev,都是潜在的黄绿色磷光材料。以铱配合物Ⅳ和Ⅳ-d20为客体,制备了结构为ITO/HT:NDP-9(100nm,2%)/HT(130nm)/EB(10nm)/GH:化合物Ⅳ或Ⅳ-d20(40nm,5%)/HB(10nm)/ ET:Liq(35nm,50%)/Liq(10nm)/Al(150nm)的OLED器件,并研究了它们的器件性能。结果表明:铱配合物Ⅳ-d20表现出更优异的器件性能。电流密度为20mA/cm2时,铱配合物Ⅳ-d20的器件发射波长为552nm,CIE 坐标为 (0.422,0.569),电流效率为 87.00cd/A,外量子效率(EQE)高达23.82%。 相似文献
163.
研究银耳多糖(Tremella fuciformis polysaccharide,TFP)与大豆分离蛋白(soybean protein isolate,SPI)的相互作用,利用浊度、纳米粒度仪、激光共聚焦扫描显微镜、流变仪、荧光光谱法和傅里叶变换红外光谱法等对TFP与SPI的复合凝聚过程进行表征。结果表明:pH值、SPI与TFP质量比和盐离子浓度对凝聚体的形成影响较大,当SPI∶TFP>1时,与复合物形成相关的关键pH值(pHc和pHφ1)向高pH值方向移动。当SPI∶TFP<1时,pHφ1向低pH值方向移动。随着体系中TFP比例的增大,浊度的最大吸收峰逐渐降低(pHopt逐渐减小)。当SPI∶TFP=1∶1时,两者在pH 3.0处的相互作用最强,此时体系总体的黏度最大(约为1.30 Pa·s),形成的聚集体最多且粒径最大。NaCl浓度较低(<20 mmol/L)时能促进SPI-TFP凝聚体形成,NaCl浓度较高(≥20 mmol/L)时由于屏蔽作用会抑制凝聚体的形成。当剪切频... 相似文献
164.
S. L. Bereznitskii D. D. Bogachenko I. V. Gaydaenko O. K. Egorov V. V. Kolesnikov V. F. Turov 《Measurement Techniques》2009,52(1):33-36
Efforts to increase the speed with which microscopic objects are measured are described. These efforts include the modernization
of the MAS-1 automatic scanning microscope and the development of programs to reach an initial point and for carrying out
automatic point-to-point linear transitions with a specified step. The error in realizing a transition to a given point with
specified coordinates is shown to amount to 1 μm.
Translated from Izmeritel’naya Tekhnika, No. 1, pp. 22–24, January, 2009. 相似文献
165.
ABSTRACTIn an effort to improve the solubility of the insoluble drug scutellarin, a novel complexation of scutellarin with β-cyclodextrin (β-CD) was studied. Tetracomponent freeze-dried complex was prepared with scutellarin, β-CD, Hydroxypropyl Methylcellulose (HPMC), and triethanolamine. To confirm complex formation, complex was characterized by Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction, and differential scanning calorimetry (DSC). Phase-solubility analysis suggested the soluble complexes having 1:1 stoichiometry. The β-CD solubilization of scutellarin could be improved significantly by combining water-soluble polymer and pH adjuster. Comparing the binary, ternary solid systems with tetrary systems, tetracomponent freeze-dried complex showed the best effect of solubilization. A maximal solubility of scutellarin (23.65 mg/ml) was achieved with tetracomponent freeze-dried complex, up to 148-fold increase over scutellarin solubility in water, and the solubility of scutellarin is 15.35 ug/ml (up to 6-fold) in simulated gastric fluid. 相似文献
166.
The energy consumption during dewatering and carboxyl concentrations on the surfaces of six different coals were examined. Three stages of dewatering were investigated based on the energy consumption. The water in the spaces between coal particles and large pores, water in progressively smaller capillaries and pores, water clusters around the functional groups, and water directly absorbed by oxygen functional groups were subsequently removed with increasing energy consumption. The moisture present in three forms was significantly affected by carboxyl concentrations. In the first and second stages, the energy consumption at the same residual moisture content was closely related to the carboxyl concentrations. Even at the same ratio of moisture content to carboxyl concentration, energy consumption increased with an increase in carboxyl concentration on coal surface in the second stage. 相似文献
167.
Light olefins dimerization to high quality gasoline components 总被引:4,自引:0,他引:4
New attractive technologies can be designed in the field of light olefins dimerization (C3–C5) in order to obtain products useful as gasoline blending components; the technologies are characterized both by low investment costs and by high product quality. Isobutene dimerization is a powerful alternative to MTBE production whenever the use of the latter will be forbidden in gasoline. Also the dimerization of iso-amylenes and propylene, when properly designed, can give products (both the olefins and the corresponding hydrogenated derivatives) characterized by very high octane numbers. More in general all these technologies can help to debottleneck the FCC downstream when enhanced olefins production is achieved by means of new FCC catalysts and processes. 相似文献
168.
169.
Rare earth organic complexes as down-shifters to improve Si-based solar cell efficiency 总被引:1,自引:0,他引:1
This work reports on the optical and electrical characterization of crystalline silicon based solar modules encapsulated with ethylene-vinyl-acetate layers (that is the encapsulating matrix used nowadays by the photovoltaic industry) doped with a single europium complex whose sensitized region is broadened due to the presence of a co-ligand. Such europium doped EVA layers are able to realize down-shifting of photons with wavelength lower than 460 nm without introducing modifications of the industrial process leading to the fabrication of the photovoltaic modules. This effect has been proven under Air Mass 1.5 conditions (simulating terrestrial applications), where a 2.9% relative increase of the total power delivered by the encapsulated modules has been observed, allowing a reduction in the watt-peak price. 相似文献
170.
A chelating polymer, poly(2,4‐dihydroxy benzophenone hydrazone–formaldehyde) [poly(DHBPH–F)], was synthesized by the polycondensation of 2,4‐dihydroxy benzophenone hydrazone with formaldehyde in the presence of oxalic acid as a catalyst. Poly(DHBPH–F) was characterized by Fourier transform infrared and 1H‐NMR spectral data. The molecular weight of the polymer was determined by gel permeation chromatography. Polychelates were obtained when the dimethylformamide solution of the polymer containing a few drops of ammonia was treated with an aqueous solution of metal ions. Elemental analysis of the polychelates indicated that the metal–ligand ratio was 1 : 2. The IR spectra of the polymer–metal complexes suggested that the metals were coordinated through the oxygen of the phenolic? OH group and the nitrogen of the azomethine group. The electron paramagnetic resonance and magnetic moment data indicated a square planar configuration for Cu(II) chelate and an octahedral structure for Ni(II) chelate. The thermogravimetric analysis, differential scanning calorimetry, and X‐ray diffraction data indicated that the incorporation of the metal ions significantly enhanced the degree of crystallinity. The polymerization initiation, electrical conductivity, and catalytic activity of the polychelates are discussed. Heavy‐metal ions [viz., Cu(II) and Ni(II)] were removed with this formaldehyde resin, and the metal‐ion uptake efficiency at different pH's, the nature and concentration of the electrolyte, and the reusability of the resin were also studied. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献