全文获取类型
收费全文 | 1711篇 |
免费 | 48篇 |
国内免费 | 23篇 |
专业分类
电工技术 | 36篇 |
综合类 | 5篇 |
化学工业 | 366篇 |
金属工艺 | 57篇 |
机械仪表 | 66篇 |
建筑科学 | 43篇 |
矿业工程 | 3篇 |
能源动力 | 98篇 |
轻工业 | 94篇 |
水利工程 | 26篇 |
石油天然气 | 11篇 |
无线电 | 195篇 |
一般工业技术 | 405篇 |
冶金工业 | 187篇 |
原子能技术 | 25篇 |
自动化技术 | 165篇 |
出版年
2023年 | 28篇 |
2022年 | 70篇 |
2021年 | 97篇 |
2020年 | 77篇 |
2019年 | 56篇 |
2018年 | 65篇 |
2017年 | 73篇 |
2016年 | 63篇 |
2015年 | 41篇 |
2014年 | 68篇 |
2013年 | 118篇 |
2012年 | 69篇 |
2011年 | 87篇 |
2010年 | 64篇 |
2009年 | 78篇 |
2008年 | 78篇 |
2007年 | 53篇 |
2006年 | 51篇 |
2005年 | 22篇 |
2004年 | 22篇 |
2003年 | 28篇 |
2002年 | 17篇 |
2001年 | 17篇 |
2000年 | 23篇 |
1999年 | 27篇 |
1998年 | 53篇 |
1997年 | 32篇 |
1996年 | 41篇 |
1995年 | 22篇 |
1994年 | 16篇 |
1993年 | 26篇 |
1992年 | 13篇 |
1991年 | 22篇 |
1990年 | 11篇 |
1989年 | 20篇 |
1988年 | 11篇 |
1987年 | 19篇 |
1986年 | 8篇 |
1985年 | 15篇 |
1984年 | 18篇 |
1983年 | 7篇 |
1982年 | 12篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 8篇 |
1978年 | 4篇 |
1977年 | 8篇 |
1976年 | 7篇 |
1975年 | 3篇 |
1969年 | 2篇 |
排序方式: 共有1782条查询结果,搜索用时 16 毫秒
991.
Ranjan Bhattacharyya S. C. Pandey S. Chandra S. Kundu Supradip Saha B. L. Mina A. K. Srivastva H. S. Gupta 《Nutrient Cycling in Agroecosystems》2010,86(2):255-268
To date, the sustainability of wheat (Triticum
aestivum)–soybean (Glycine
max) cropping systems has not been well assessed, especially under Indian Himalayas. Research was conducted in 1995–1996 to 2004
at Hawalbagh, India to study the effects of fertilization on yield sustainability of irrigated wheat–soybean system and on
selected soil properties. The mean wheat yield under NPK + FYM (farmyard manure) treated plots was ~27% higher than NPK (2.4 Mg ha−1). The residual effect of NPK + FYM caused ~14% increase in soybean yield over NPK (2.18 Mg ha−1). Sustainable yield index values of wheat and the wheat–soybean system were greater with annual fertilizer N or NPK plots
10 Mg ha−1 FYM than NPK alone. However, benefit:cost ratio of fertilization, agronomic efficiency and partial factor productivity of
applied nutrients were higher with NPK + FYM than NPK, if FYM nutrients were not considered. Soils under NPK + FYM contained
higher soil organic C (SOC), total soil N, total P and Olsen-P by ~10, 42, 52 and 71%, respectively, in the 0–30 cm soil layers,
compared with NPK. Non-exchangeable K decreased with time under all treatments except NPK. Total SOC in the 0–30 cm soil layer
increased in all fertilized plots. Application of NPK + FYM also improved selected soil physical properties over NPK. The
NPK + FYM application had better soil productivity than NPK but was not as economical as NPK if farmers had to purchase manure. 相似文献
992.
This paper outlines the compositional characteristics of wastewater from a low temperature carbonization (LTC), plant manufacturing domestic coke, generating tar and light oil. Wastewater characteristics from this plant show the presence of a variety of pollutants like phenols, ammonia, cyanide, sulphide and thiocyanate in appreciable concentration owing to the absence of byproduct recovery operations. Under suitable conditions, biological treatment of LTC wastewater in a two stage activated sludge process (ASP) mainly results in good removal of BOD (95%) and COD (78%). Concentrations of different phenols and their fate in these treatment units show that the phenols except pyrogallol can be removed efficiently. Ammonia cannot be stabilized to nitrite or nitrate even after maintaining a high sludge retention time (SRT) in the bioreactors. Cyanide removal in these units is very poor. Microbiological status of these units reveals that most of the active biomass is comprised of phenol-utilizing organisms. The system constants for biological unit operations for ASP, like oxygenation capacity of LTC wastewater (a = 0.50 and B = 0.36) and biokinetic constants (Y = 0.13, kd = 0.12 d−1, μmax = 0.59 d−1 and ks = 88.25 mg 1−1), have been evaluated. 相似文献
993.
Rajiv Kumar Pandey S. P. Singh P. Singh 《Journal of Superconductivity and Novel Magnetism》1999,12(2):441-443
In this paper, we have modified the Cooper theory by considering a biexcitonic attractive interaction for high T c superconductors. We have developed an expression for (2Δ/K B T c) as a function of phonon and biexciton mediated coupling constants. For the sake of simplicity, we use a two-square-well potential model (electron–phonon and electron–biexciton). The calculated values of (2Δ/K B T c) show good agreement with experimental values. 相似文献
994.
995.
Silicon - In the present work, the n + source pocket PIN gate all around tunnel FET (PNIN-GAA-TFET) based gas sensor has been proposed. Various analyte gases such as hexane, methanol,... 相似文献
996.
Mayara J. Prado Shripriya Singh Rodrigo Ligabue-Braun Bruna V. Meneghetti Thaiane Rispoli Cristiane Kopacek Karina Monteiro Arnaldo Zaha Maria L. R. Rossetti Amit V. Pandey 《International journal of molecular sciences》2022,23(1)
Deficiency of 21-hydroxylase enzyme (CYP21A2) represents 90% of cases in congenital adrenal hyperplasia (CAH), an autosomal recessive disease caused by defects in cortisol biosynthesis. Computational prediction and functional studies are often the only way to classify variants to understand the links to disease-causing effects. Here we investigated the pathogenicity of uncharacterized variants in the CYP21A2 gene reported in Brazilian and Portuguese populations. Physicochemical alterations, residue conservation, and effect on protein structure were accessed by computational analysis. The enzymatic performance was obtained by functional assay with the wild-type and mutant CYP21A2 proteins expressed in HEK293 cells. Computational analysis showed that p.W202R, p.E352V, and p.R484L have severely impaired the protein structure, while p.P35L, p.L199P, and p.P433L have moderate effects. The p.W202R, p.E352V, p.P433L, and p.R484L variants showed residual 21OH activity consistent with the simple virilizing phenotype. The p.P35L and p.L199P variants showed partial 21OH efficiency associated with the non-classical phenotype. Additionally, p.W202R, p.E352V, and p.R484L also modified the protein expression level. We have determined how the selected CYP21A2 gene mutations affect the 21OH activity through structural and activity alteration contributing to the future diagnosis and management of CYP21A2 deficiency. 相似文献
997.
Anju Raghvendra Singh Yadav Petra Ptschke Jürgen Pionteck Beate Krause Ivo Kuitka Jarmila Vil
kov David koda Pavel Urbnek Michal Machovský Milan Masa Michal Urbnek 《International journal of molecular sciences》2022,23(5)
CuxCo1-xFe2O4 (x = 0.33, 0.67, 1)-reduced graphene oxide (rGO)-thermoplastic polyurethane (TPU) nanocomposites exhibiting highly efficient electromagnetic interference (EMI) shielding were prepared by a melt-mixing approach using a microcompounder. Spinel ferrite Cu0.33Co0.67Fe2O4 (CuCoF1), Cu0.67Co0.33Fe2O4 (CuCoF2) and CuFe2O4 (CuF3) nanoparticles were synthesized using the sonochemical method. The CuCoF1 and CuCoF2 exhibited typical ferromagnetic features, whereas CuF3 displayed superparamagnetic characteristics. The maximum value of EMI total shielding effectiveness (SET) was noticed to be 42.9 dB, 46.2 dB, and 58.8 dB for CuCoF1-rGO-TPU, CuCoF2-rGO-TPU, and CuF3-rGO-TPU nanocomposites, respectively, at a thickness of 1 mm. The highly efficient EMI shielding performance was attributed to the good impedance matching, conductive, dielectric, and magnetic loss. The demonstrated nanocomposites are promising candidates for a lightweight, flexible, and highly efficient EMI shielding material. 相似文献
998.
Sadananda Das A.K. Pandey Anjali Athawale Virendra Kumar Y.K. Bhardwaj S. Sabharwal V.K. Manchanda 《Desalination》2008,232(1-3):243
The amidoximated macroporous membranes (AO membranes) were prepared by post irradiation grafting of acrylonitrile (AN) onto thermally bonded non-woven matrix of poly(propylene) sheet using electron beams. These precursor membranes were reacted with hydroxylamine to convert AN to AO groups, and conditioned by treating them with 2.5% KOH at 80°C for 1 h. The water uptake capacity in seawater, Na+-exchange capacity, and uranium loading capacity from seawater of AO membranes were found to be 200±10 wt.%, (3.1±0.2)×10−4 mol/g, and (1.60±0.18)×10−3 mol/g, respectively. The expected functional group density based on the degree of AN grafting (125 wt.%) and its subsequent conversion to AO groups (80%) was found to be 7.8×10−3 mol/g. The comparison of the expected functional group density and uranium uptake capacity seems to suggest that UO22+ forms a complex with AO groups in 1:4 proportion. The uranium could be quantitatively desorbed (>90%) from the AO membrane in Na2CO3 and mineral acids like HCl in the equilibration times of 60 min and 40 min, respectively. Alkaline conditioning was found to be necessary for reuse of the membrane equilibrated with acid. However, AO membranes equilibrated with Na2CO3 could be reused without any conditioning for uranium sorption. 相似文献
999.
The ternary blends of acrylate rubber (ACM), poly(butylene terephthalate) (PBT), and liquid crystalline polymer (LCP) were prepared by varying the amount of LCP but fixing the ratio of ACM and PBT, using melt mixing procedure. The influence of interactions on thermal and dynamic mechanical properties of the blends was investigated over the complete composition range. The techniques applied were Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetry (TG), and dynamic mechanical analysis (DMA). The FTIR spectroscopy analysis showed reduction in the intensity of the peak corresponding to epoxy groups of ACM with increasing heating time at 290°C. This implies that there is a chemical reaction between the epoxy and end groups of PBT and LCP. Glass transition temperature (Tg) and melting temperature (Tm) of the blends were affected depending on the LCP weight percent in the ACM/PBT blend, respectively. This further suggests the strong interfacial interactions between the blend components. In presence of ACM, the nucleating effect of LCP was more pronounced for the PBT phase. The thermogravimetric study showed improved thermal stability for the blends with the increasing LCP content. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3904–3912, 2006 相似文献
1000.
Pandey S Rakholiya KD Raval VH Singh SP 《Journal of Bioscience and Bioengineering》2012,114(3):251-256
A haloalkaliphilic bacterium, isolated from Coastal Gujarat (India) was identified as Oceanobacillus sp. (GQ162111) based on 16S rRNA gene sequence. The organism grew and secreted extra cellular protease in presence of various organic solvents. At 30% (v/v) concentration of hexane, heptane, isooctane, dodecane and decane, significant growth and protease production was evident. The alkaline protease was purified in a single step on phenyl sepharose 6 FF with 28% yield. The molecular mass as judged by SDS-PAGE was 30?kDa. The temperature optimum of protease was 50°C and the enzyme retained 70% activity in 10% (v/v) isooctane. Effect of salt and pH was investigated in combination to assess the effect of isooctane. In organic solvents, the enzyme was considerably active at pH 8-11, with optimum activity at pH 10. Salt at 2?M was optimum for activity and enzyme maintained significant stability up to 18?h even at 3?M salt concentration. Patters of growth, protease production, catalysis and stability of the enzyme are presented. The study resumes significance as limited information is available on the interaction of haloalkaliphilic bacteria and their enzymes with organic solvents. 相似文献