全文获取类型
收费全文 | 16974篇 |
免费 | 1343篇 |
国内免费 | 647篇 |
专业分类
电工技术 | 966篇 |
技术理论 | 2篇 |
综合类 | 1118篇 |
化学工业 | 3115篇 |
金属工艺 | 855篇 |
机械仪表 | 1034篇 |
建筑科学 | 1398篇 |
矿业工程 | 553篇 |
能源动力 | 430篇 |
轻工业 | 1087篇 |
水利工程 | 275篇 |
石油天然气 | 1007篇 |
武器工业 | 90篇 |
无线电 | 1929篇 |
一般工业技术 | 2154篇 |
冶金工业 | 813篇 |
原子能技术 | 292篇 |
自动化技术 | 1846篇 |
出版年
2024年 | 68篇 |
2023年 | 297篇 |
2022年 | 407篇 |
2021年 | 567篇 |
2020年 | 475篇 |
2019年 | 462篇 |
2018年 | 472篇 |
2017年 | 518篇 |
2016年 | 432篇 |
2015年 | 619篇 |
2014年 | 796篇 |
2013年 | 937篇 |
2012年 | 988篇 |
2011年 | 1008篇 |
2010年 | 898篇 |
2009年 | 986篇 |
2008年 | 892篇 |
2007年 | 889篇 |
2006年 | 949篇 |
2005年 | 785篇 |
2004年 | 601篇 |
2003年 | 549篇 |
2002年 | 563篇 |
2001年 | 528篇 |
2000年 | 452篇 |
1999年 | 535篇 |
1998年 | 372篇 |
1997年 | 353篇 |
1996年 | 351篇 |
1995年 | 283篇 |
1994年 | 258篇 |
1993年 | 162篇 |
1992年 | 125篇 |
1991年 | 91篇 |
1990年 | 73篇 |
1989年 | 66篇 |
1988年 | 50篇 |
1987年 | 34篇 |
1986年 | 20篇 |
1985年 | 15篇 |
1984年 | 8篇 |
1983年 | 8篇 |
1982年 | 7篇 |
1981年 | 5篇 |
1980年 | 8篇 |
1979年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
提高高校图书馆的管理效益和水平,必须使高校图书馆的管理观念从科学管理转为信息资源管理;管理模式的体制、结构、服务内容、操作以及人员知识结构必须适当改变,以适应信息资源的要求。 相似文献
132.
Twelve samples derived from different locations in south central area of China are treated by enrichment and spread-plate
technique for initial screening. Seven chitinase-producing strains are isolated. The chitinase present in the culture supernatant
of strain CS-01 possesses the maximum activity of 0.118 U/mL. Analysis of the morphological feature and the ITS rDNA sequence
reveals that strain CS-01 belongs to Aspergillus fumigatus. Production of the chitinase is regulated by a inducible way and the maximum activity appears at 36 h in colloidal chitin
culture. Purification of the chitinase is carried out by salting out, gel filtrate chromatography and anion exchange chromatography
sequentially. Native-PAGE and SDS-PAGE indicate that the chitinase from A. fumigatus CS-01 is a monomer with the relative molecular mass estimated to be 4.50×104. Its maximum activity appears at pH 5 and 55 °C. The chitinase is stable at pH 4.0–7.5 and below 45 °C.
Foundation item: Projects(50621063, 50674101) supported by the National Natural Science Foundation of China 相似文献
133.
Mixed microorganisms with elevated activity of chalcocite-leaching were screened by mutation methods. The original microorganisms
collected from acid mine drainage of different sites were mixed and then treated with mutagens NO2−, diethyl sulfate (DES), UV and their combinations, respectively. Five groups of mixed microorganisms with much stronger ore-leaching
ability were obtained by screening on the leaching media. Among them, group E of mixed microorganisms (treated with 1% DES
for 60 min) with the best performance on chalcocite-leaching, increases the content of Cu2+ by 101.4% in 20 d of leaching compared with the control culture. In addition, group E is more tolerant to Cu2+ in media than the control without mutation treatment. Analysis for the diversity of microbial clones indicates that half
of operational taxonomic units (OTUs) in group E are Acidithiobacillus ferrooxidans. These observations suggest that group E might have potentials for industrial application.
Foundation item: Project(50321402) supported by the National Natural Science Foundation of China; Project(2004CB619201) supported by the Major
State Basic Research and Development Program of China 相似文献
134.
Identification and fermentation optimization of protopectinase-overproducing strain Aspergillus niger CD-01 for pectin production 总被引:1,自引:1,他引:0
In order to solve the citrus peel resource waste problem and minimize the drawbacks of chemical extraction of pectin, a protopectinase-overproducing
strain CD-01 for pectin production was isolated from a pit soil dumped with perished orange in Changde City, Hunan Province
of China. The strain CD-01 had the same morphology and 28S rRNA gene sequence (FJ184995) as that of Aspergillus niger (ATCC 64028). It was thus identified and named as Aspergillus niger CD-01. The fermentation condition was optimized based on L9(34) orthogonal experimental design and the variances analyses. The results show that the optimal condition for producing pectin
is as follows: time 36 h, temperature 35 °C, pH 5, and urea as the nitrogen source. Under this condition, the pectin yield
can reach up to 24.5%. This shows a great potential of Aspergillus niger CD-01 in pectin extraction from citrus.
Foundation item: Projects(50621063, 50674101) supported by the National Natural Science Foundation of China 相似文献
135.
136.
<伤逝>围绕着理想与绝望这一人生核心问题,通过涓生与子君人生理想终极悖论的层层设置,不断突围和最终否定,阐释出无论是人生理想、反抗,还是绝望,都应清醒地把握当时的社会现状与自我的人生状况.文本准确地剖析了当时的社会与人生,把人生哲理和当时社会现实紧紧结合在一起,让读者透过时代脉搏的律动,感受人生的真谛. 相似文献
137.
The electronic structures of kinks in the [100](010) and 1/2[111](−110) edge dislocations in bcc iron containing hydrogen
are investigated by means of the first-principles DMol method and the discrete variational method. The effects of hydrogen
on the kinks are discussed. The results show that hydrogen forms weak bonding states with its neighboring host atoms, and
since hydrogen draws charge from its neighboring host atoms, the interactions between most of the host atoms are weakened
compared with those of the corresponding atomic pairs in the clean kinks. This indicates that the migration of kink, i.e.
the motion of dislocation, is easier in the doping hydrogen kink than in the clean kink, which may be the solid solution softening
effect resulting from the impurity hydrogen.
Supported by the National Basic Research Program of China (Grant No. 2006CB605102) and Science Foundation of Central South
University of Forestry & Technology (Grant No. 06y016) 相似文献
138.
Modified Mg(OH)2/polypropylene (PP) composites were prepared by the addition of functionalized polypropylene (FPP); and acrylic acid (AA) and by the formation of in situ FPP. The effects of the addition of FPP and AA and the formation of in situ FPP on the mechanical properties of Mg(OH)2/PP composites were investigated. Experimental results indicated that the addition of Mg(OH)2 markedly reduced the mechanical properties of PP. The extent of reduction in notch impact strength of PP was higher than that in flexural strength and tensile strength. However, tensile modulus and flexural modulus increased with increased Mg(OH)2 content. The addition of FPP facilitated the improvement in the flexural strength and tensile strength of Mg(OH)2/PP composites. The higher the Mg(OH)2 content was, the more significant the effect of FPP was. The incorporation of AA resulted in further increased mechanical properties, in particular the flexural strength, tensile strength, and notch impact strength of Mg(OH)2/PP composites containing high levels of Mg(OH)2. It not only improved mechanical properties but also increased the flame retardance of Mg(OH)2/PP composites. Although the mechanical properties of composites modified by the formation of in situ FPP were lower than those of composites modified by only the addition of AA in the absence of diamylperoxide, the mechanical properties did not decline with increased Mg(OH)2 content. Moreover, the mechanical properties increased with increasing AA content. The addition of an oxidation resistant did not influence the mechanical properties of the modified Mg(OH)2/PP composites. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2139–2147, 2003 相似文献
139.
目的 提出了一个基于流形学习的动作识别框架,用来识别深度图像序列中的人体行为。方法 从Kinect设备获得的深度信息中评估出人体的关节点信息,并用相对关节点位置差作为人体特征表达。在训练阶段,利用LE(Lalpacian eigenmaps)流形学习对高维空间下的训练集进行降维,得到低维隐空间下的运动模型。在识别阶段,用最近邻差值方法将测试序列映射到低维流形空间中去,然后进行匹配计算。在匹配过程中,通过使用改进的Hausdorff距离对低维空间下测试序列和训练运动集的吻合度和相似度进行度量。结果 用Kinect设备捕获的数据进行了实验,取得了良好的效果;同时也在MSR Action3D数据库上进行了测试,结果表明在训练样本较多情况下,本文方法识别效果优于以往方法。结论 实验结果表明本文方法适用于基于深度图像序列的人体动作识别。 相似文献
140.
SEBS的臭氧处理及增韧PA6的研究 总被引:1,自引:0,他引:1
研究了臭氧处理对氢化苯乙烯-丁二烯-苯乙烯嵌段共聚物(SEBS)分子结构及其极性的影响,并对臭氧处理SEBS增韧PA6进行了研究。结果表明,通过臭氧处理可在SEBS分子链上引入羰基含氧基团,臭氧处理的SEBS相对分子质量下降,相对分子质量分布变宽,表面能提高,极性增大。与PA6/SEBS体系相比,PA6/臭氧处理SEBS体系的相容性得到明显改善,其冲击强度和断裂伸长率大幅度提高。 相似文献