全文获取类型
收费全文 | 11445篇 |
免费 | 818篇 |
国内免费 | 196篇 |
专业分类
电工技术 | 166篇 |
技术理论 | 1篇 |
综合类 | 934篇 |
化学工业 | 3444篇 |
金属工艺 | 212篇 |
机械仪表 | 155篇 |
建筑科学 | 1439篇 |
矿业工程 | 362篇 |
能源动力 | 362篇 |
轻工业 | 2862篇 |
水利工程 | 385篇 |
石油天然气 | 670篇 |
武器工业 | 14篇 |
无线电 | 119篇 |
一般工业技术 | 456篇 |
冶金工业 | 608篇 |
原子能技术 | 82篇 |
自动化技术 | 188篇 |
出版年
2024年 | 45篇 |
2023年 | 127篇 |
2022年 | 218篇 |
2021年 | 364篇 |
2020年 | 343篇 |
2019年 | 260篇 |
2018年 | 243篇 |
2017年 | 347篇 |
2016年 | 373篇 |
2015年 | 411篇 |
2014年 | 693篇 |
2013年 | 722篇 |
2012年 | 1025篇 |
2011年 | 910篇 |
2010年 | 710篇 |
2009年 | 665篇 |
2008年 | 575篇 |
2007年 | 718篇 |
2006年 | 750篇 |
2005年 | 528篇 |
2004年 | 445篇 |
2003年 | 384篇 |
2002年 | 305篇 |
2001年 | 245篇 |
2000年 | 201篇 |
1999年 | 169篇 |
1998年 | 127篇 |
1997年 | 96篇 |
1996年 | 83篇 |
1995年 | 71篇 |
1994年 | 54篇 |
1993年 | 49篇 |
1992年 | 28篇 |
1991年 | 36篇 |
1990年 | 21篇 |
1989年 | 22篇 |
1988年 | 14篇 |
1987年 | 17篇 |
1986年 | 13篇 |
1985年 | 20篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1974年 | 1篇 |
1959年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Hong Jin Mohammad S. Uddin Yu L. Huang Wah K. Teo 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1994,59(1):67-72
High level expression of recombinant human tumour necrosis factor β (rh TNF-β) in Escherichia coli results in the formation of two portions of protein, namely soluble active protein and insoluble protein which is inactive and aggregates in the form of inclusion bodies (IBs). In this study, a procedure for purification and renaturation of rh TNF-β from inclusion bodies has been designed and verified experimentally with a product purity of more than 90% and a recovery of about 30%. The procedure includes washing of IBs with specific wash buffer (Triton X-100/EDTA/lysozyme/PMSF), their solubilization with 8 mol dm?3 alkaline urea, purification with ion-exchange columns, refolding with renaturation buffer and finally concentration and desalination with an ultrafiltration membrane. The characteristics of the renatured protein were identical with those of purified protein from the soluble fraction as demonstrated by (1) SDS-PAGE, (2) cytotoxic activity on mouse L929 cells, (3) N-terminal amino acid sequence, and (4) gel filtration chromatography. 相似文献
32.
33.
Takaaki Wajima Tomoe Shimizu Yasuyuki Ikegami 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(6):921-927
BACKGROUND: This study aimed to investigate the synthesis of zeolites from paper sludge ash (PSA) with added diatomite to remove both NH4+ and PO43? for water purification. The PSA had low Si and significant Ca contents. Four types of diatomite: white (T‐W) and brown (T‐B) from deposits of marine origin in Takanosu, and white (S‐W) and gray (S‐G) from lacustrine deposits in Shonai, were added to NaOH solution to increase the Si content and thereby synthesize zeolites with high cation exchange capacity (CEC). RESULTS: The order of the amounts of Si extracted from the diatomite to the alkali solution was S‐W > T‐W = T‐B > S‐G, which correlates with the amorphous SiO2 content of diatomite. The original ash without addition of diatomite yielded hydroxysodalite with CEC of about 1.0 mmol g?1. For all samples, the addition of diatomite to the solution yielded zeolite‐P with a higher CEC, but the addition of excess Si inhibited the synthesis of zeolite‐P, and the CEC of the product was low. A product with high CEC including zeolite‐P was obtained in a solution with around 500 mmol L?1 of Si concentration, and had the ability to remove both NH4+ and PO43?. CONCLUSION: Diatomite has the potential for used as an additive for the synthesis of high CEC zeolite from PSA. The product with zeolite‐P exhibited relatively high CEC, capacity for NH4+ uptake, and the ability to remove PO43? by precipitation, which is preferable for water purification applications. Copyright © 2008 Society of Chemical Industry 相似文献
34.
本文系统阐述污水环境下砼腐蚀及耐久性问题,分析了引起砼破坏和腐蚀的各种因素,提出采用高性能砼改善污水环境下砼的耐久性。 相似文献
35.
介绍了宝钢集团上海五钢不锈钢长型材热轧工程浊循环水处理的工艺设计,探讨了采用化学除油工艺、自动反清洗过滤器等技术和设备,处理不锈钢热轧浊环水的技术特点。 相似文献
36.
制盐行业卤水净化都是采用库存药品和人工加药,这种做法劳动强度大,环境恶劣,影响人们健康,又不经济。为此介绍一种新的药品储存和投加工艺及设备。 相似文献
37.
38.
Sandra L. McLellan Erika J. HollisMorgan M. Depas Meredith Van DykeJosh Harris Caitlin O. Scopel 《Journal of Great Lakes research》2007,33(3):566-580
Escherichia coli distribution and persistence in nearshore Lake Michigan were assessed following heavy rains and sanitary sewer overflow (SSO) and combined sewer overflow (CSO) events over a 5-year period, including an 18-day period following 25.4 cm of rainfall in which intensive studies were conducted following multiple CSO and SSO events. E. coli levels in the Milwaukee estuary and harbor following SSO and CSO events ranged from 104 to nearly 105 CFU/100 mL, which were significantly higher (p ≤ 0.05) than levels following rainfall alone. Sites outside of the breakwall but within the contamination plume (e.g., within 2 km of the harbor) were an order of magnitude lower. Locations 2–5 km from the harbor ranged from below detection limits, of < 1 to 5 CFU/100 mL. E. coli levels corrected for dilution based on specific conductivity measurements were lower than what would be expected for loss due to dilution alone, suggesting a combination of die-off and dilution, were responsible for the rapid disappearance of these organisms outside of the harbor. E. coli and fecal coliforms measured concurrently demonstrated that fecal coliforms could be recovered longer than E. coli in the open waters of the lake. E. coli isolated directly from sewage treatment plant influent were found to have a marked increase in antibiotic resistance traits for ten antibiotics commonly used in the human population compared with isolates from two animal sources of fecal pollution. However, E. coli obtained from sewage impacted water (n = 2,513) and from stormwater impacted water (n = 1,465) collected the previous year when there were no sewage overflows, were found to have no significant difference (p < 0.05) in the frequency of resistance when comparing the two conditions. E. coli survival characteristics and population dynamics are most likely influenced by multiple factors in complex systems such as the watershed/estuarine/lake environments of the Great Lakes. 相似文献
39.
Ames试验氯化致突变前体物在净水工艺中的去除研究 总被引:2,自引:1,他引:1
采用水样比活性作为评价指标,从Ames试验结果和致突变前体物性质两方面,探讨了不同单元净水工艺对Ames试验氯化致突变前体物的去除能力,从而为净水工艺的选择提供参考依据 相似文献
40.
针对催化裂化装置汽油和液态烃精制产生的含硫废弃物的碱渣处理,讨论了碱渣提酚、碱渣湿式氧化脱臭两种处理工艺的环境治理效果,并就碱渣湿式氧化脱臭工艺如何降低运行成本、减少污水排放等内容进行了探讨。 相似文献