全文获取类型
收费全文 | 14965篇 |
免费 | 1304篇 |
国内免费 | 887篇 |
专业分类
电工技术 | 537篇 |
综合类 | 976篇 |
化学工业 | 4693篇 |
金属工艺 | 820篇 |
机械仪表 | 539篇 |
建筑科学 | 372篇 |
矿业工程 | 176篇 |
能源动力 | 422篇 |
轻工业 | 1178篇 |
水利工程 | 100篇 |
石油天然气 | 576篇 |
武器工业 | 76篇 |
无线电 | 1425篇 |
一般工业技术 | 1160篇 |
冶金工业 | 627篇 |
原子能技术 | 342篇 |
自动化技术 | 3137篇 |
出版年
2024年 | 24篇 |
2023年 | 139篇 |
2022年 | 217篇 |
2021年 | 359篇 |
2020年 | 334篇 |
2019年 | 312篇 |
2018年 | 258篇 |
2017年 | 383篇 |
2016年 | 457篇 |
2015年 | 433篇 |
2014年 | 719篇 |
2013年 | 880篇 |
2012年 | 1098篇 |
2011年 | 1187篇 |
2010年 | 1089篇 |
2009年 | 1252篇 |
2008年 | 1083篇 |
2007年 | 1198篇 |
2006年 | 1125篇 |
2005年 | 737篇 |
2004年 | 623篇 |
2003年 | 498篇 |
2002年 | 502篇 |
2001年 | 381篇 |
2000年 | 366篇 |
1999年 | 290篇 |
1998年 | 204篇 |
1997年 | 180篇 |
1996年 | 152篇 |
1995年 | 124篇 |
1994年 | 100篇 |
1993年 | 89篇 |
1992年 | 66篇 |
1991年 | 48篇 |
1990年 | 42篇 |
1989年 | 35篇 |
1988年 | 20篇 |
1987年 | 18篇 |
1986年 | 8篇 |
1985年 | 17篇 |
1984年 | 15篇 |
1983年 | 16篇 |
1982年 | 19篇 |
1981年 | 19篇 |
1980年 | 15篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1975年 | 3篇 |
1974年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Reply to Finley's (1987; see record 1988-00015-001) critique of rational-emotive philosophy, which claims that Ellis's (1981) response to Sharkey's (1981) criticisms of rational-emotive psychology reveals logical and philosophical confusion. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
82.
83.
Lutein and lutein esters in marigold flowers was quantitatively determined by high performance chromatography (HPLC) with ODS-C18 column. A mixture of CH3CN-CH3OH-CH3COOCH2CH2 with volume ratio of 55:1:44 was used as mobile phase at a flow rate of 1.0mL/min and detection was carried out at 480 nm. The column temperature was about 20℃. The contents of lutein and lutein esters were determined by analytical curve of lutein since lutein and lutein esters have the same spectral characteristics. Determination results of hexane extracts and saponified samples of lutein show that the saponification transforms the esters into free lutein. The increase of the content of dipalmitate and palmitate stearate reveals that the reaction includes transesterifications. 相似文献
84.
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
85.
The forming behaviour at high temperature of a modified 9%Cr‐1%Mo (P91) ferritic steel containing B and Ti for elevated temperature service was investigated. The microstructure of the as‐received material is mainly martensite at room temperature, but special etching revealed prior austenite grains of about 25 μm in size. Torsion tests were conducted at temperatures in the range 850 to 1250 °C to simulate the hot rolling process under comparable conditions of temperature, strain rate and strain. The deformation data obtained from these tests were correlated with the Garofalo equation with a stress exponent of 4.6 and an activation energy of 315 kJ/mol. This equation was used to predict the formability behaviour for the rolling process and also to determine the maximum forming efficiency and stability of the steel. A temperature of 1200 °C is recommended to conduct the forming process. 相似文献
86.
介绍了基于CAN总线的分布式果园气象监测系统,重点描述了单片机P87C591的特点及以它为控制核心构成的监测网络节点的实现。 相似文献
87.
采用Tritonx-100为铜、锌、铁、锰的增感剂,对高纯氯化锂中的铜、锌、铁、锰进行了原子吸收光谱分析,结果令人满意。其特征浓度铜为0.018μg.ml-1/1%吸收、锌为0.004μg.ml-1/1%吸收、铁为0.021μg.ml-1/1%吸收,锰为0.011μg.ml-1/1%吸收。 相似文献
88.
综述了粉末冶金温压工艺的研究进展,概述了温压工艺的粉末原料、聚合物、温度、压力、烧结环节对温压工艺的影响和温压工艺的致密化机理。详细介绍了温压工艺的新进展—流动温压、高压温压等,并对其应用前景进行了展望。 相似文献
89.
粉末冶金低合金钢的制备和性能研究进展 总被引:1,自引:0,他引:1
从粉末制备、成形工艺、烧结工艺和组织控制等方面,系统的介绍了国内外粉末冶金低合金钢的制备技术,并对其研究方向和应用前景进行了展望。 相似文献
90.
S. Sarkar P. K. Singha S. Dey M. Mohanty B. Adhikari 《Materials and Manufacturing Processes》2006,21(3):291-296
A polyester urethane was synthesized for use in a biodegradable scaffold. The polyurethane was synthesized in a two-step process: first, ester diol was synthesized from lactic acid and polyethylene glycol 400 (PEG 400), then it was polymerized with toluene diisocyanate using dibutyl tin dilaurate (DBTDL) as a catalyst to form a polyester urethane. Polyester urethane has tensile strength of 51-59 MPa and elongation at fracture of 369-439%. FTIR and XRD were used to confirm the formation and structure of the polymer. Hydrolytic degradation was studied in different alkali solutions and in saline water. In order to assess the cellular response of this material, cytotoxicity analysis was carried out against the cell line. 相似文献