全文获取类型
收费全文 | 483387篇 |
免费 | 7506篇 |
国内免费 | 2523篇 |
专业分类
电工技术 | 9683篇 |
技术理论 | 5篇 |
综合类 | 1335篇 |
化学工业 | 73460篇 |
金属工艺 | 19308篇 |
机械仪表 | 14276篇 |
建筑科学 | 12009篇 |
矿业工程 | 2453篇 |
能源动力 | 12288篇 |
轻工业 | 43306篇 |
水利工程 | 4828篇 |
石油天然气 | 8532篇 |
武器工业 | 258篇 |
无线电 | 57894篇 |
一般工业技术 | 93119篇 |
冶金工业 | 91910篇 |
原子能技术 | 9771篇 |
自动化技术 | 38981篇 |
出版年
2021年 | 4430篇 |
2020年 | 3115篇 |
2019年 | 3881篇 |
2018年 | 6325篇 |
2017年 | 6304篇 |
2016年 | 6768篇 |
2015年 | 4803篇 |
2014年 | 8059篇 |
2013年 | 21677篇 |
2012年 | 13079篇 |
2011年 | 17674篇 |
2010年 | 14192篇 |
2009年 | 15667篇 |
2008年 | 16814篇 |
2007年 | 16825篇 |
2006年 | 14832篇 |
2005年 | 12998篇 |
2004年 | 12026篇 |
2003年 | 11931篇 |
2002年 | 11464篇 |
2001年 | 11952篇 |
2000年 | 11060篇 |
1999年 | 11535篇 |
1998年 | 28013篇 |
1997年 | 19950篇 |
1996年 | 15236篇 |
1995年 | 11453篇 |
1994年 | 10422篇 |
1993年 | 10235篇 |
1992年 | 7557篇 |
1991年 | 7271篇 |
1990年 | 7176篇 |
1989年 | 6943篇 |
1988年 | 6678篇 |
1987年 | 5698篇 |
1986年 | 5619篇 |
1985年 | 6225篇 |
1984年 | 5905篇 |
1983年 | 5579篇 |
1982年 | 5026篇 |
1981年 | 5118篇 |
1980年 | 4818篇 |
1979年 | 4839篇 |
1978年 | 4540篇 |
1977年 | 5160篇 |
1976年 | 6889篇 |
1975年 | 3953篇 |
1974年 | 3776篇 |
1973年 | 3755篇 |
1972年 | 3226篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
171.
Abraham G. Alvarado Rosaura Hernández-Montelongo Martin Rabelero Lourdes A. Pérez-Carrillo Jorge E. Puig Francisco López-Serrano 《Polymer Engineering and Science》2020,60(2):223-232
A simple but comprehensive model considering homogeneous and micellar nucleation, coagulation, entry of radicals to particles and to micelles and radicals' exit from particles, is presented. The model is validated, in a starved semicontinuous heterophase polymerization of ethyl methacrylate, at three monomer addition rates. The model accurately describes the overall and instantaneous conversion, the average particle density and diameter, and the number and weight average molar masses evolutions over time. It is found that even though the average number of radicals is much smaller than 0.5, the system is not 0-1. An empirical function was used to describe the gel effect. The homogeneous nucleation was the prevailing mechanism for particle formation and large exit rates of radicals were observed. POLYM. ENG. SCI., 60: 223–232, 2019. © 2019 Society of Plastics Engineers 相似文献
172.
Detailed study on fusion characteristics of rigid poly(vinyl chloride) nanocomposites: The comparison of using multiple regression analysis and artificial neural network
下载免费PDF全文
![点击此处可从《乙烯基与添加剂工艺杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Fusion behavior of poly(vinyl chloride) (PVC) compounds plays an important role in the development of physical properties of processed material. The fusion characteristics in PVC processing are governed by material variables that affect the fusion with some interactions. In this research, the aim was to characterize the effects of formulation ingredients on fusion characteristics of PVC. Four material parameters, including the contents of nanoclay (NC), azodicarbonamide, calcium stearate, and processing aid, are proposed as affecting variables. The fusion time (FT) as well as fusion factor (FF) are considered fusion indicators and are experimentally determined in some different levels of affecting parameters. The multivariable regression analysis (MRA) and the Artificial Neural Network (ANN) modeling are considered as two analytical methods. The regression analysis result for the FT denotes, in part, significant linear and quadratic effects of NC and also its significant interactions with azodicarbonamide and calcium stearate, whereas that of FF indicates only a linear effect of NC. ANN modeling is performed with a three‐layer (input, hidden, and output) neural network. The results of the comparison of the MRA and ANN predictions with experimental values are reported as the correlation coefficient (R2), mean‐square error, and mean absolute percentage error for both FF and FT parameters. The obtained values clearly denote that the ANN results are more precise and especially more general than those of MRA. However, in the case of FT, improvement of the ANN modeling is much greater than that of FF. J. VINYL ADDIT. TECHNOL., 21:147–155, 2015. © 2014 Society of Plastics Engineers 相似文献
173.
Neural Computing and Applications - With an increase in online longitudinal users’ interactions, capturing users’ precise preferences and giving accurate recommendations have become an... 相似文献
174.
L. Bolzoni 《Metal Powder Report》2019,74(6):308-313
175.
Medel Manuel L. Zulueta Donala Janreddy Shang-Cheng Hung 《Israel journal of chemistry》2015,55(3-4):347-359
In recent years, there has been rapid expansion of glycan synthesis, fueled by the recognition that the structural complexity of sugars translates to a myriad of biological functions. Such chemical syntheses involve many challenges, mostly due to the regio- and stereochemical aspects of glycosidic bond formation. One-pot strategies were developed to assist in attaining faster and more economical access to the glycan constructs. In this front, achievements in protecting group manipulation, glycosylation, and combinations of these have been reported. Protecting group manipulations in one pot take advantage of the reaction compatibility of commonly used transformations, many of which occur in high regioselectivity. Sequential glycosylations, on the other hand, rely on leaving group orthogonalities and reactivity tuning, as well as the preactivation technique. Altogether, these approaches offer attractive means to the much needed glycan structures and, consequently, help usher in advances in glycoscience. 相似文献
176.
177.
178.
179.
Jonathan K. Dozier Mark D. Distefano 《International journal of molecular sciences》2015,16(10):25831-25864
The use of proteins as therapeutics has a long history and is becoming ever more common in modern medicine. While the number of protein-based drugs is growing every year, significant problems still remain with their use. Among these problems are rapid degradation and excretion from patients, thus requiring frequent dosing, which in turn increases the chances for an immunological response as well as increasing the cost of therapy. One of the main strategies to alleviate these problems is to link a polyethylene glycol (PEG) group to the protein of interest. This process, called PEGylation, has grown dramatically in recent years resulting in several approved drugs. Installing a single PEG chain at a defined site in a protein is challenging. Recently, there is has been considerable research into various methods for the site-specific PEGylation of proteins. This review seeks to summarize that work and provide background and context for how site-specific PEGylation is performed. After introducing the topic of site-specific PEGylation, recent developments using chemical methods are described. That is followed by a more extensive discussion of bioorthogonal reactions and enzymatic labeling. 相似文献
180.