全文获取类型
收费全文 | 3447篇 |
免费 | 83篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 47篇 |
综合类 | 2篇 |
化学工业 | 584篇 |
金属工艺 | 106篇 |
机械仪表 | 56篇 |
建筑科学 | 121篇 |
矿业工程 | 27篇 |
能源动力 | 59篇 |
轻工业 | 309篇 |
水利工程 | 23篇 |
石油天然气 | 3篇 |
无线电 | 320篇 |
一般工业技术 | 608篇 |
冶金工业 | 895篇 |
原子能技术 | 39篇 |
自动化技术 | 336篇 |
出版年
2023年 | 17篇 |
2022年 | 28篇 |
2021年 | 58篇 |
2020年 | 34篇 |
2019年 | 52篇 |
2018年 | 58篇 |
2017年 | 55篇 |
2016年 | 53篇 |
2015年 | 40篇 |
2014年 | 69篇 |
2013年 | 156篇 |
2012年 | 107篇 |
2011年 | 147篇 |
2010年 | 112篇 |
2009年 | 105篇 |
2008年 | 110篇 |
2007年 | 95篇 |
2006年 | 110篇 |
2005年 | 87篇 |
2004年 | 72篇 |
2003年 | 81篇 |
2002年 | 80篇 |
2001年 | 73篇 |
2000年 | 65篇 |
1999年 | 78篇 |
1998年 | 265篇 |
1997年 | 177篇 |
1996年 | 141篇 |
1995年 | 81篇 |
1994年 | 89篇 |
1993年 | 79篇 |
1992年 | 45篇 |
1991年 | 34篇 |
1990年 | 35篇 |
1989年 | 52篇 |
1988年 | 37篇 |
1987年 | 28篇 |
1986年 | 33篇 |
1985年 | 27篇 |
1984年 | 26篇 |
1983年 | 22篇 |
1982年 | 16篇 |
1981年 | 24篇 |
1980年 | 16篇 |
1979年 | 21篇 |
1978年 | 29篇 |
1977年 | 31篇 |
1976年 | 65篇 |
1975年 | 27篇 |
1974年 | 21篇 |
排序方式: 共有3535条查询结果,搜索用时 15 毫秒
81.
Dbora Drummond Hauss Monteiro Henrique Limboro Rodrigo Guimares Porto Allyson Nogueira Moreira Wagner Nunes Rodrigues Cludia Silami de Magalhes 《Microscopy research and technique》2020,83(6):597-603
The MeX? software is a useful tool for tridimensional data collection for surface evaluation and could be relevant to evaluate the same specimen in different phases of the study, assuming repeated measures of dental enamel roughness. The aim of this study was to evaluate the influence of sample metallization for dental enamel roughness analysis with 3D images reconstructed using MeX? software from Scanning Electron Microscopy (SEM) images. The influence of 74.98% (%mol/mol) argon?oxygen plasma for carbon layer removal on surface roughness of the metallized specimen was also evaluated. Dental enamel specimens were prepared for SEM analysis with and without carbon metallization using conventional or environmental modes. Argon?oxygen plasma for carbon layer removal was used and surface roughness was re‐evaluated. Roughness obtained by SEM and MeX? reconstructed images, with or without metallization, did not differ. No significant alteration on surface roughness after carbon layer removal using plasma was found. SEM baseline evaluation using conventional mode without sample preparation and in environmental mode were not comparable. Roughness of enamel 3D images reconstructed with MeX? software from SEM images, with or without metallization was similar. The 74.98% (%mol/mol) argon?oxygen plasma removed the carbon layer with no effect on enamel roughness. 相似文献
82.
83.
由于能耗可降低30%,MPS变形机可很容易地将速度提高30%,从而使MPS的构想成为一种用于细旦长丝变形加工的十分经济的方案. 相似文献
84.
A low-voltage 40-GHz complementary VCO with 15% frequency tuning range in SOI CMOS technology 总被引:1,自引:0,他引:1
Neric Fong Jonghae Kim Plouchart J.-O. Zamdmer N. Duixian Liu Wagner L. Plett C. Tarr G. 《Solid-State Circuits, IEEE Journal of》2004,39(5):841-846
The design of a low-voltage 40-GHz complementary voltage-controlled oscillator (VCO) with 15% frequency tuning range fabricated in 0.13-/spl mu/m partially depleted silicon-on-insulator (SOI) CMOS technology is reported. Technological advantages of SOI over bulk CMOS are demonstrated, and the accumulation MOS (AMOS) varactor limitations on frequency tuning range are addressed. At 1.5-V supply, the VCO core and each output buffer consumes 11.25 mW and 3 mW of power, respectively. The measured phase noise at 40-GHz is -109.73 dBc/Hz at 4-MHz offset from the carrier, and the output power is -8 dBm. VCO performance using high resistivity substrate (/spl sim/300-/spl Omega//spl middot/cm) has the same frequency tuning range but 2 dB better phase noise compared with using low resistivity substrate (10 /spl Omega//spl middot/cm). The VCO occupies a chip area of only 100 /spl mu/m by 100 /spl mu/m (excluding pads). 相似文献
85.
Peter Nuhn Ekkehard Schilling Günther Wagner 《Advanced Synthesis \u0026amp; Catalysis》1976,318(2):291-297
Immunosuppressant-Antigen Conjugates. VIII. Preparation of 6-Thiopurine-Protein Conjugates by the Azide Method 6-Carboxymethyl-thiopurine was coupled with human serum albumin (HSA) and bovine serum globuline in the presence of a water soluble carbodiimide. Under these conditions, reaction of HSA with the carbodiimide led to electrophoretically detectable changes. Therefore, further conjugates were prepared by the azide method. The used azides, N-(6-benzylthiopurin- and 6-methylthiopurin-9-yl)-acetyl azide, were obtained from the hydrazides. The prepared conjugates contained upto 4.2% thiopurine, determined by spectrophotometry. It was not possible to obtain an azide from purinyl-(6)-thioacethydrazide. 相似文献
86.
Identification and Structure–Activity Relationship Studies of Small‐Molecule Inhibitors of the Methyllysine Reader Protein Spindlin1 下载免费PDF全文
Dr. Dina Robaa Dr. Tobias Wagner Chiara Luise Dr. Luca Carlino Joel McMillan Dr. Ralf Flaig Prof. Dr. Roland Schüle Prof. Dr. Manfred Jung Prof. Dr. Wolfgang Sippl 《ChemMedChem》2016,11(20):2327-2338
The methyllysine reader protein Spindlin1 has been implicated in the tumorigenesis of several types of cancer and may be an attractive novel therapeutic target. Small‐molecule inhibitors of Spindlin1 should be valuable as chemical probes as well as potential new therapeutics. We applied an iterative virtual screening campaign, encompassing structure‐ and ligand‐based approaches, to identify potential Spindlin1 inhibitors from databases of commercially available compounds. Our in silico studies coupled with in vitro testing were successful in identifying novel Spindlin1 inhibitors. Several 4‐aminoquinazoline and quinazolinethione derivatives were among the active hit compounds, which indicated that these scaffolds represent promising lead structures for the development of Spindlin1 inhibitors. Subsequent lead optimization studies were hence carried out, and numerous derivatives of both lead scaffolds were synthesized. This resulted in the discovery of novel inhibitors of Spindlin1 and helped explore the structure–activity relationships of these inhibitor series. 相似文献
87.
In a Rheotens experiment, the tensile force needed for elongation of an extruded filament is measured as a function of the draw ratio. For thermo-rheologically simple polymer melts, the existence of Rheotens-mastercurves is proven. Rheotens-mastercurves are invariant with respect to changes in melt temperature. Also, for polymer melts with different average molar masses, but similar molar mass distribution and branching structure, Rheotens-mastercurves are invariant to changes in the average molar mass. It is shown, by testing several polyethylenes with different molar mass distribution and different long-chain branching, that Rheotens-mastercurves allow a direct and quantitative assessment of the drawability of polymer melts under actual processing conditions, i.e. under the action of a constant tensile force and including the effects of the rheological prehistory in the extrusion die. 相似文献
88.
This paper demonstrates the usefulness of careful experimental work with model composite materials, such as thin polymeric films in which single fibers are accurately positioned, in at least two respects: to assess the validity of a theory for a given physical property, and to accurately probe the effects of various parameters on the behavior of composites. Working with such model composites has obvious advantages, such as the full control of experimental parameters, the possibility of introducing perturbative effects in a controlled way, and the possibility of verifying theoretical models in the range of low fiber content. Indeed, macroscopic composite materials contain various types of defects and perturbative effects, such as fiber misalignment or slack, fiber-poor regions, voids, etc., which bias any quantitative assessment of mechanical and physical properties, and preclude the accurate verification of theoretical schemes. One difficulty in working with microcomposite models, also recalled here, is the need for an appropriate “scaling-up” procedure to the level of macroscopic composites. 相似文献
89.
Luz Bertoia Jorge R. Wagner Andrés L. Márquez 《Journal of the American Oil Chemists' Society》2020,97(10):1071-1081
The objective was to study the microstructure and freeze–thaw stability of margarine-like emulsions formulated with vegetable fats using differential scanning calorimetry. Emulsions were prepared with 20% w/w dispersed aqueous phase and a continuous lipid phase composed by coconut oil (CO) and/or palm oil (PO) plus polyglycerol polyricinoleate (PGPR) as emulsifier. Mean temperature (TM) and crystallization enthalpy (ΔHc) were obtained from the exothermic peaks corresponding to freezing of aqueous phase. Successive cooling–heating–cooling cycles were applied to analyze changes in the exothermic peak. The emulsion prepared with CO (without PO) and 1% w/w PGPR in lipid phase showed higher water droplets size (TM = −44.8 ± 0.1 °C) and lower quantity of stabilized aqueous phase (ΔHc = 28.9 ± 1.2 J g−1) prior to application of temperature cycles, while coalescence and (presumably) water transfer processes occurred during the treatment. The use of 2% w/w PGPR was sufficient to accomplish full stabilization of aqueous phase (TM = −45.9 ± 0.1 °C; ΔHc = 42.6 ± 0.3 J g−1) before and after the freeze–thaw treatment. The total or partial (50%) substitution of CO by PO in emulsions with 1% w/w PGPR also improved the stability of the system, exhibiting slight microstructural changes. This enhanced stability would be linked to reduced water droplets size because of more rapid crystallization of lipid phase and immobilization of aqueous phase after emulsion preparation. In conclusion, it is possible to obtain margarine-like emulsions prepared with CO and/or PO using relatively low emulsifier concentration and maintaining a desired microstructure after freeze-thawing if the percentage ratio of both fats is controlled. 相似文献
90.