全文获取类型
收费全文 | 3067篇 |
免费 | 123篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 27篇 |
化学工业 | 419篇 |
金属工艺 | 70篇 |
机械仪表 | 81篇 |
建筑科学 | 116篇 |
矿业工程 | 3篇 |
能源动力 | 78篇 |
轻工业 | 228篇 |
水利工程 | 35篇 |
石油天然气 | 4篇 |
无线电 | 343篇 |
一般工业技术 | 708篇 |
冶金工业 | 767篇 |
原子能技术 | 13篇 |
自动化技术 | 303篇 |
出版年
2023年 | 15篇 |
2022年 | 28篇 |
2021年 | 46篇 |
2020年 | 34篇 |
2019年 | 44篇 |
2018年 | 85篇 |
2017年 | 79篇 |
2016年 | 57篇 |
2015年 | 45篇 |
2014年 | 68篇 |
2013年 | 145篇 |
2012年 | 132篇 |
2011年 | 149篇 |
2010年 | 134篇 |
2009年 | 117篇 |
2008年 | 100篇 |
2007年 | 122篇 |
2006年 | 96篇 |
2005年 | 105篇 |
2004年 | 80篇 |
2003年 | 83篇 |
2002年 | 69篇 |
2001年 | 57篇 |
2000年 | 62篇 |
1999年 | 88篇 |
1998年 | 160篇 |
1997年 | 98篇 |
1996年 | 93篇 |
1995年 | 46篇 |
1994年 | 47篇 |
1993年 | 55篇 |
1992年 | 41篇 |
1991年 | 30篇 |
1990年 | 30篇 |
1989年 | 43篇 |
1988年 | 26篇 |
1987年 | 28篇 |
1986年 | 30篇 |
1985年 | 40篇 |
1984年 | 30篇 |
1983年 | 20篇 |
1982年 | 23篇 |
1981年 | 27篇 |
1980年 | 24篇 |
1979年 | 17篇 |
1978年 | 22篇 |
1977年 | 36篇 |
1976年 | 52篇 |
1975年 | 25篇 |
1973年 | 15篇 |
排序方式: 共有3195条查询结果,搜索用时 0 毫秒
101.
In this study, we synthesized a new hybrid material using well-Dawson K6[P2Mo18O62]·nH2O and a room temperature ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]). CHN elemental analysis showed that one mole of [P2Mo18O62]6− reacts with 6 moles of [BMIM]+ to form [BMIM]6P2Mo18O62. FT-IR spectra showed the presence of both 1-butyl-3-methylimidazolium cation and the Dawson anion. TG analysis displayed a relative thermal stability of the hybrid material compared to the parent Dawson POM. The new hybrid material [BMIM]6P2Mo18O62 was immobilized on glassy carbon (GC) electrode and the modified electrode was investigated by cyclic voltammetry and amperometry. Compared to the electrochemical behavior of dissolved [P2Mo18O62]6−, a slight shift in the redox peaks towards negative potentials is observed for the immobilized [BMIM]6P2Mo18O62. The relationship between the peak currents of the deposited [BMIM]6P2Mo18O62 film and scan rate is shown to be linear, which demonstrates a surface-confined electron transfer processes. [BMIM]6P2Mo18O62 modified electrode showed high sensitivities towards pH and shown to be active even at neutral pH. [BMIM]6P2Mo18O62 modified GC electrode was subjected to cyclic voltammetry and amperometry in the presence of ascorbic acid (AA) and found to exhibit a remarkable catalytic activity towards the oxidation of AA. The catalytic oxidation peak of AA at [BMIM]6P2Mo18O62 modified GC electrode occurs at low potential of ∼0 V vs Ag/AgCl at neutral pH and shifts to more positive potentials when pH decreases. Comparison between [BMIM]6P2Mo18O62 and [P2Mo18O62]6− modified GC films towards the oxidation of AA suggests that the significant decrease in the overpotentials recorded with [BMIM]6P2Mo18O62 film is related to the presence of ionic liquid cation in the hybrid material, which probably plays the role of the redox mediator. The resulting AA sensor [BMIM]6P2Mo18O62/GC has a significant sensitivity of ∼63 nA/μM AA, fast response time (<9 s), low detection limit (<0.1 μM), high selectivity towards endogenous interferences such as uric acid, acetaminophen and dopamine, a linear range from 0.1 μM to at least 22 mM AA and was stable for at least 2 weeks. In addition, such AA sensors can operate in a pH range from 0 to at least 7. 相似文献
102.
S. Ganesan B. Muthuraaman Vinod Mathew M. Kumara Vadivel P. Maruthamuthu M. Ashokkumar S. Austin Suthanthiraraj 《Electrochimica acta》2011,(24):8811
A novel method of introducing a synthesized organic nitrogenous compound 2,6 (N-pyrazolyl)isonicotinic acid (BNIN) and its effect on the conduction behavior of poly(vinylidene fluoride) (PVdF)–poly(ethylene oxide) (PEO) polymer-blend electrolyte with potassium iodide (KI) and iodine (I2) and the corresponding performance of the dye-sensitized solar cells (DSSCs) were studied. A systematic investigation of the blends using FTIR provides evidence of interaction of BNIN with the polymer. Differential scanning calorimetry (DSC) study proves the miscibility of these polymers. Due to the coordinating and plasticizing effects of BNIN, the ionic conductivity of polymer blend electrolytes is enhanced. The efficiency of DSSC using BNIN doped polymer blend electrolyte was 7.3% under an illumination of 60 mW cm−2 were observed for the best performance of a solar cell in this work. 相似文献
103.
The effect of an ultraviolet generated ozone treatment (UV/O3), on the surface and near surface functionality and structure of polyacrylonitrile based carbon fibres has been studied using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy, and Raman spectroscopy. Results were compared to electrochemically treated fibres. The UV/O3 treated fibres showed increased levels of oxygen functionalities. Levels of oxygen comparable to a high level electrochemical shear treatment were achieved within 5 min of treatment (O/C 0.11 ± 0.03 for both treatments). XPS O1s/C1s ratios as high as 0.3 were produced, with saturation occurring at approximately 40 min exposure. The main functional groups introduced were, in addition to hydroxyl species, alkoxides (ca. 286.5 eV), carbonyl (288.0 eV), and carboxyl (289.5 eV). Examination of the full width half maximum of the graphite peak from XPS C1s showed some disorder was introduced to the first few layers of the fibre with treatment but the effect was not evident in the Raman, i.e. in the bulk of the fibre. 相似文献
104.
A three-dimensional mathematical model of the combustion of pulverized coal and coke is developed. The model is applied to the region of lance-blowpipe-tuyere-raceway-coke bed to simulate in-furnace phenomena of pulverized coal injection in an ironmaking blast furnace. The model integrates not only pulverized coal combustion model in the blowpipe-tuyere-raceway-coke bed but also coke combustion model in the coke bed. The model is validated against the measurements under different conditions. The comprehensive in-furnace phenomena are investigated in the raceway and coke bed, in terms of flow, temperature, gas composition, and coal burning characteristics. The underlying mechanisms for the in-furnace phenomena are also analysed. The simulation results indicate that it is important to include recirculation region in the raceway and the coke bed reactions for better understanding in-furnace phenomena. The model provides a cost-effective tool for understanding and optimizing the in-furnace flow-thermo-chemical characteristics of the PCI operation in full-scale blast furnaces. 相似文献
105.
Naoko Kobayashi Eric A. Noel Austin Barnes Julian Rosenberg Concetta DiRusso Paul Black George A. Oyler 《Lipids》2013,48(10):1035-1049
Triacylglycerol (TAG) analysis and quantification are commonly performed by first obtaining a purified TAG fraction from a total neutral lipid extract using thin-layer chromatography (TLC), and then analyzing the fatty acid composition of the purified TAG fraction by gas chromatography (GC). This process is time-consuming, labor intensive and is not suitable for analysis of small sample sizes or large numbers. A rapid and efficient method for monitoring oil accumulation in algae using high performance liquid chromatography for separation of all lipid classes combined with detection by evaporative light scattering (HPLC–ELSD) was developed and compared to the conventional TLC/GC method. TAG accumulation in two Chlamydomonas reinhardtii (21 gr and CC503) and three Chlorella strains (UTEX 1230, CS01 and UTEX 2229) grown under conditions of nitrogen depletion was measured. The TAG levels were found to be 3–6 % DW (Chlamydomonas strains) and 7–12 % DW (Chlorella strains) respectively by both HPLC–ELSD and TLC/GC methods. HPLC–ELSD resolved the major lipid classes such as carotenoids, TAG, diacylglycerol (DAG), free fatty acids, phospholipids, and galactolipids in a 15-min run. Quantitation of TAG content was based on comparison to calibration curves of trihexadecanoin (16:0 TAG) and trioctadecadienoin (18:2 TAG) and showed linearity from 0.2 to 10 μg. Algal TAG levels >0.5 μg/g DW were detectable by this method. Furthermore TAG content in Chlorella kessleri UTEX 2229 could be detected. TAG as well as DAG and TAG content were estimated at 1.6 % DW by HPLC–ELSD, while it was undetectable by TLC/GC method. 相似文献
106.
The relationship between enzyme inactivation and the concentration of oxygen in the reaction environment was studied using glutamine synthetase. Batch incubations of the enzyme were conducted under different oxygen partial pressures in a mixed-function oxidase model system. Enzyme activity was monitored using a transferase reaction assay. Studies showed that oxygen was necessary for inactivation to occur. Furthermore, for oxygen partial pressures up to 61kPa, the rate of inactivation increased linearly with partial pressure. Rates of inactivation ranged from 0.0172+/?0.0038 min-1 at 15 kPa to 0.0591+/?0.0045 min-1 at 61 kPa. However, at partial pressures of 61, 81, and 101 kPa, rates of inactivation were statistically identical. 相似文献
107.
Dr. Raysa Khan Tareque Dr. Storm Hassell-Hart Dr. Tobias Krojer Dr. Anthony Bradley Dr. Srikannathasan Velupillai Dr. Romain Talon Dr. Michael Fairhead Dr. Iain J. Day Kamlesh Bala Dr. Robert Felix Dr. Paul D. Kemmitt Prof. Paul Brennan Prof. Frank von Delft Dr. Laura Díaz Sáez Prof. Kilian Huber Prof. John Spencer 《ChemMedChem》2020,15(24):2513-2520
Combined photochemical arylation, “nuisance effect” (SNAr) reaction sequences have been employed in the design of small arrays for immediate deployment in medium-throughput X-ray protein–ligand structure determination. Reactions were deliberately allowed to run “out of control” in terms of selectivity; for example the ortho-arylation of 2-phenylpyridine gave five products resulting from mono- and bisarylations combined with SNAr processes. As a result, a number of crystallographic hits against NUDT7, a key peroxisomal CoA ester hydrolase, have been identified. 相似文献
108.
Test specimens following ASTM D638 standards are frequently used to measure the tensile properties of reinforced and unreinforced polymers machined with traditional machining and emerging manufacturing methods (additive manufacturing/3D printing). However, designs of large engineering structures may rely on mechanical properties based on ASTM D3039 for fiber-reinforced polymer composites. This parametric study examines the scaling effects present in uniaxial tensile test specimens of molded high-density polyethylene (HDPE), with geometries ranging from Types I to IV of ASTM D638 to ASTM D3039. HDPE is a thermoplastic polymer that is recyclable, can be 3D-printed, and has a wide range of engineering applications, from bottles to pipes to radiation protection shielding. The mechanical properties test results for the molded HDPE samples are validated using a Monte Carlo simulation to estimate uncertainties for the probability distribution of maximum stress at the yield point. A Finite Element study based on the empirical model shows how the proposed approach can be adopted for design purposes. The results of this work are a useful tool to enhance confidence in the tensile mechanical properties of ASTM D638 Types II and IV geometries as statistically similar to those of ASTM D3039 samples, impacting engineering designs with traditional and emerging manufacturing methods. 相似文献
109.
Capt. Courtney Kiggins Austin Skinner Prof. Marino J. E. Resendiz 《Chembiochem : a European journal of chemical biology》2020,21(9):1347-1355
Aptamers are attractive constructs due to their high affinity/selectivity towards a target. Here 7,8-dihydro-8-oxoguanosine (8-oxoG) has been used, due in part to its unique H-bonding capabilities (Watson–Crick or Hoogsteen), to expand the “RNA alphabet”. Its impact on the theophylline RNA aptamer was explored by modifying its binding pocket at positions G11, G25, or G26. Structural probing, with RNases A and T1, showed that modification at G11 leads to a drastic structural change, whereas the G25-/G26-modified analogues exhibited cleavage patterns similar to that of the canonical construct. The recognition properties towards three xanthine derivatives were then explored through thermophoresis. Modifying the aptamer at position G11 led to binding inhibition. Modification at G25, however, changed the selectivity towards theobromine (Kd≈160 μm ), with a poor affinity for theophylline (Kd>1.5 mm ) being observed. Overall, 8-oxoG can have an impact on the structures of aptamers in a position-dependent manner, leading to altered target selectivity. 相似文献
110.
Bradley L. Wing Francis Esmonde‐White John W. Halloran 《Journal of the American Ceramic Society》2016,99(11):3705-3711
Microstress in reaction‐bonded silicon carbide (RBSiC) has been measured using piezo‐Raman spectroscopy. Compressive microstresses as high as 2 GPa exist in the silicon phase and tensile microstresses as high as 2.3 GPa exist in the SiC phase of RBSiC. This is much larger than expected for thermoelastic microstress from coefficient of thermal expansion mismatch would provide. Instead the microstresses arise from the crystallization of liquid silicon. During the reaction bonding process, not all of the silicon reacts to form SiC and there is liquid free silicon. The phase transformation of the free silicon from liquid to solid has a large volume expansion, which results in large residual microstress within the silicon and SiC phases of RBSiC. 相似文献