全文获取类型
收费全文 | 81905篇 |
免费 | 7155篇 |
国内免费 | 4266篇 |
专业分类
电工技术 | 5855篇 |
技术理论 | 6篇 |
综合类 | 6611篇 |
化学工业 | 13731篇 |
金属工艺 | 7865篇 |
机械仪表 | 4470篇 |
建筑科学 | 8546篇 |
矿业工程 | 2507篇 |
能源动力 | 4979篇 |
轻工业 | 5341篇 |
水利工程 | 2645篇 |
石油天然气 | 3925篇 |
武器工业 | 703篇 |
无线电 | 6243篇 |
一般工业技术 | 8761篇 |
冶金工业 | 5763篇 |
原子能技术 | 1425篇 |
自动化技术 | 3950篇 |
出版年
2024年 | 340篇 |
2023年 | 1164篇 |
2022年 | 2226篇 |
2021年 | 2713篇 |
2020年 | 2819篇 |
2019年 | 2262篇 |
2018年 | 2112篇 |
2017年 | 2742篇 |
2016年 | 2900篇 |
2015年 | 2985篇 |
2014年 | 4999篇 |
2013年 | 5192篇 |
2012年 | 5963篇 |
2011年 | 6367篇 |
2010年 | 4537篇 |
2009年 | 4675篇 |
2008年 | 4130篇 |
2007年 | 5388篇 |
2006年 | 4941篇 |
2005年 | 4006篇 |
2004年 | 3537篇 |
2003年 | 2977篇 |
2002年 | 2507篇 |
2001年 | 2195篇 |
2000年 | 1801篇 |
1999年 | 1422篇 |
1998年 | 1115篇 |
1997年 | 981篇 |
1996年 | 843篇 |
1995年 | 663篇 |
1994年 | 572篇 |
1993年 | 397篇 |
1992年 | 396篇 |
1991年 | 331篇 |
1990年 | 259篇 |
1989年 | 173篇 |
1988年 | 147篇 |
1987年 | 86篇 |
1986年 | 88篇 |
1985年 | 75篇 |
1984年 | 62篇 |
1983年 | 52篇 |
1982年 | 51篇 |
1981年 | 19篇 |
1980年 | 26篇 |
1979年 | 22篇 |
1977年 | 10篇 |
1961年 | 5篇 |
1959年 | 15篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
21.
G. SAID 《Fatigue & Fracture of Engineering Materials & Structures》2006,29(8):606-614
Costs of ASTM E399 and ASTM E1921 tests, which were developed to determine the fracture toughness (KIc) and the ductile–brittle transition temperature of ferritic steels, respectively, are considered high and the procedures are also very complicated. In this study, a method, which is more cost‐effective and easier to carry out, is proposed. 相似文献
22.
23.
The role of gas phase CH3 radicals in the oxidative coupling of CH4 over 1 wt% Sr/La2O3 is supported by the observations that (i) this is a very effective catalyst for the generation of CH3 · radicals and (ii) the concentration of CH3 · radicals increases with temperature over the range of 450 °C–800 °C. 相似文献
24.
Baudilio Coto Carmen Martos Jos L. Pea Juan J. Espada María D. Robustillo 《Fuel》2008,87(10-11):2090-2094
Wax precipitation is one of the most important flow assurance problems. Unfortunately, experimental data are very scarce to confirm existing models for prediction of such precipitation problem. This work reports a new experimental method. Multistage fractional wax precipitation was carried out by decreasing the temperature of crude oil. No solvent dilution was used, so the effect of solvent on temperature wax precipitation was avoided. The reproducibility of the method was tested with comparable results. The precipitation curve and the wax appearance temperature were obtained for two crude oils with different chemical nature using the reported method. 相似文献
25.
Degumming of hemp fiber by high temperature alkali cooking was investigated, and the effect of temperature and dosage of alkali on the constituents, structure, and thermal degradation of hemp fiber was also discussed in this work. The morphology, structure, and thermal degradation of hemp fiber after high temperature cooking were investigated through SEM, FTIR, WAXD, and TG analysis. The results indicated that the high temperature cooking process was effective for removing hemicelluloses and lignin and could also improve the thermal stability of cellulose. Crystallinity index of the treated hemp fiber was increased, which was related to the cooking temperature and NaOH dosage. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
26.
The radical copolymerization of acyclic terpene namely geraniol [GER] with acrylonitrile [AN] in DMF at (70 ± 0.1)°C for 1 h, using benzoylperoxide (BPO) as an initiator has been carried out under inert atmosphere of nitrogen. The kinetic expression for reaction is Rp ∝ [BPO]0.5 [AN]1.0 [GER]1.0. The IR spectrum of the copolymer shows bands at 3432 and at 2244 cm?1 due to ? OH group of GER and ? CN group of AN, respectively. The 13C‐NMR spectrum shows peaks at 73–75 δ ppm and 116–120 δ ppm due to ? OH group of GER and ? CN group of AN, respectively. The thermogravimetric analysis and differential scanning calorimetry study shows that copolymer is thermally stable up to 407°C and has glass transition temperatures (Tg) 56°C. The reactivity ratios r1 (AN) and r2 (GER) have been calculated as 0.05 and 0.005, respectively. The Alfrey‐Price Q‐e parameter for GER has been calculated as 0.094 and ?2.0, respectively. The molecular weights of the copolymers have been evaluated by gel‐permeation chromatography. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
27.
The thermal stress on building‐integrated photovoltaic modules (BIPV) in Espoo, Finland, was studied with field‐testing of amorphous silicon modules. Based on these results, the thermal stress at two other European locations (Paris and Lisbon) was estimated. The estimation procedure entailed thermal modelling of heat transfer in the façade with meteorological data as input. The results indicate that the thermal stress on BIPV modules in Lisbon is, in this case, approximately 50% higher that in Espoo and between 80 and 200% higher than in Paris, depending on the activation energy of the degradation process. The difference in stress between a BIPV module and a free‐standing module in Espoo was 50–200%. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
28.
Capital cost correlations are given for oil-water separators, equalization basins, primary clarifiers, clarifiers and clarifier mechanisms, reverse osmosis unit, ultrafiltration units, gravity filters and miroscreens. Data are included for raw sewage, intermediate and recirculation pumping stations and for preliminary treatment (or bar screens, grit removal, overflow and bypass chamber and Parshall flume), for grit removal, comminution and gas stripping. The correlations are accurate to ± 30%, expressed in Canadian dollars and adjusted to a Marshall and Swift value of 1000. Details as to what components are included in the cost are given. Data are given for the labour and material costs to create a working process module. For inflation indices, a critique of the Engineering News Record, EPA small city, Marshall and Swift, Chemical Engineering and Southam inflation indices suggested that the Marshall and Swift index is most appropriate for the construction and process equipment studied here. Concerning the currency exchange, for the equipment and processes in this study, equipment costs the same whether expressed directly in US or Canadian dollars. To put the current data into perspective, several hundred sources of cost data were analyzed. The major correlations are compared, on a consistent basis, with current data. 相似文献
29.
30.
本文主要完成了液态金属钠高温沸腾实验回路的应力分析与计算,确定了回路高温区连接管系的布置型式和支吊架系统,是该回路总体设计的重要组成部分。 相似文献