全文获取类型
收费全文 | 4085篇 |
免费 | 143篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 32篇 |
综合类 | 5篇 |
化学工业 | 909篇 |
金属工艺 | 53篇 |
机械仪表 | 73篇 |
建筑科学 | 116篇 |
矿业工程 | 9篇 |
能源动力 | 93篇 |
轻工业 | 295篇 |
水利工程 | 23篇 |
石油天然气 | 20篇 |
无线电 | 273篇 |
一般工业技术 | 586篇 |
冶金工业 | 1254篇 |
原子能技术 | 27篇 |
自动化技术 | 461篇 |
出版年
2023年 | 38篇 |
2022年 | 88篇 |
2021年 | 135篇 |
2020年 | 73篇 |
2019年 | 76篇 |
2018年 | 67篇 |
2017年 | 74篇 |
2016年 | 57篇 |
2015年 | 79篇 |
2014年 | 86篇 |
2013年 | 149篇 |
2012年 | 145篇 |
2011年 | 165篇 |
2010年 | 138篇 |
2009年 | 130篇 |
2008年 | 161篇 |
2007年 | 146篇 |
2006年 | 126篇 |
2005年 | 93篇 |
2004年 | 96篇 |
2003年 | 101篇 |
2002年 | 73篇 |
2001年 | 83篇 |
2000年 | 68篇 |
1999年 | 74篇 |
1998年 | 275篇 |
1997年 | 169篇 |
1996年 | 155篇 |
1995年 | 105篇 |
1994年 | 96篇 |
1993年 | 75篇 |
1992年 | 37篇 |
1991年 | 48篇 |
1990年 | 43篇 |
1989年 | 45篇 |
1988年 | 54篇 |
1987年 | 39篇 |
1986年 | 29篇 |
1985年 | 57篇 |
1984年 | 36篇 |
1983年 | 27篇 |
1982年 | 36篇 |
1981年 | 32篇 |
1980年 | 20篇 |
1979年 | 24篇 |
1978年 | 24篇 |
1977年 | 42篇 |
1976年 | 55篇 |
1974年 | 22篇 |
1973年 | 19篇 |
排序方式: 共有4229条查询结果,搜索用时 16 毫秒
171.
Joao Henrique da Silva Rego ;Antonio Alberto Nepomucenol ;Enio Pazini Figueiredo ;Nicole Pagan Hasparyk 《土木工程与建筑:英文版》2014,(11):1396-1402
In several countries, the residual RHA (rice husk ash) has been produced in rice processing industries or in thermoelectric plants that use rice husk to generate heat and/or electrical energy, usually without burning process control. This causes a reduction in the amorphous silica content of residual RHA, which distinguishes them from the RHA produced according to controlled burning process, which is totally amorphous and considered a highly reactive pozzolan. In this paper, the hydration products and the porous structure of binders paste were studied by replacing, in weight of 5%, 10% and 20% of Portland cement OPC (ordinary Portland cement), by residual RHAs named A and B, which have high and low content of amorphous silica, respectively, using microstructure evaluation techniques as XRD (X-ray diffraction), TG (thermogravimetric) tests and MIP (mercury intrusion porosimetry). A reducing the size of the pores of the pastes was observed according to the increase of content replacement of RHA A and RHA B. 相似文献
172.
From early 2004, Lake Maracaibo (northwest Venezuela) experienced an unprecedented invasion of duckweed Lemna obscura. Recurrent blooms of the plant in the past 2 years illustrate the need for an automatic monitoring method to follow the plant cover with time and to plan contingency measures. We present an approach that allows the cover of the duckweed to be quantified through the classification of MODIS 250 m RGB composite images available from the internet. The method improves the accuracy of the results of the Support Vector Machine (SVM) algorithm for classification by including a bootstrap step during the training phase. Using only 200 pixels for training (<0.05% of the total), the bootstrapped SVM method allows a better identification of the duckweed class, reducing the number of false negatives by half and improving the KHAT statistic by almost 40% in comparison to the standard SVM method. This method has proved to be a reliable solution in cases where rapid responses are needed and only medium‐resolution, free satellite imagery is available. 相似文献
173.
174.
175.
Long‐term expansion of human induced pluripotent stem cells in a microcarrier‐based dynamic system
下载免费PDF全文
![点击此处可从《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
176.
Themistoklis Diamantopoulos Michael Roth Andreas Symeonidis Ewan Klein 《Language Resources and Evaluation》2017,51(2):495-524
Mapping functional requirements first to specifications and then to code is one of the most challenging tasks in software development. Since requirements are commonly written in natural language, they can be prone to ambiguity, incompleteness and inconsistency. Structured semantic representations allow requirements to be translated to formal models, which can be used to detect problems at an early stage of the development process through validation. Storing and querying such models can also facilitate software reuse. Several approaches constrain the input format of requirements to produce specifications, however they usually require considerable human effort in order to adopt domain-specific heuristics and/or controlled languages. We propose a mechanism that automates the mapping of requirements to formal representations using semantic role labeling. We describe the first publicly available dataset for this task, employ a hierarchical framework that allows requirements concepts to be annotated, and discuss how semantic role labeling can be adapted for parsing software requirements. 相似文献
177.
How Modifying Third‐Party Information Affects Interpersonal Impressions and the Evaluation of Collaborative Online Media
下载免费PDF全文
![点击此处可从《The Journal of communication》网站下载免费的PDF全文](/ch/ext_images/free.gif)
David C. DeAndrea Brandon Van Der Heide Nicole Easley 《The Journal of communication》2015,65(1):62-78
Previous research has drawn upon warranting theory to help explain how viewers evaluate people and entities online. Extending previous research, this study assesses how the ability of a target to modify third‐party information affects perceptions of warranting value, and in turn, interpersonal impressions and the perceived legitimacy of online media that host evaluations. Additionally, this work explores how the perceived objectivity of a third‐party evaluator affects impressions in online settings. The results provide support for warranting theory and help clarify how impressions are formed in online environments when people have the ability to generate and modify content collectively. The theoretical implications this study has for warranting theory and future research directions are discussed. 相似文献
178.
The purpose of the study was to obtain a composite material with the self‐reinforced structure, which processing provide increased mechanical properties. The composites used in presented work were prepared from the two types of fiber mixtures, both were based on polypropylene fibers, the difference was in used cellulose or wood flour filler. Composites were prepared using the hot compaction method. The presented research describes the effect of the composite composition and processing conditions. The results include the static tension measurements, tensile impact tests and thermal analysis, including: DSC and DMTA. The structure has been studies using the SEM observations. Results of presented studies confirm the self‐reinforcing effect in obtained hybrid composites. It provides in the comparison to the standard wood polymer composites to the higher level of material reinforcement with lower amount of natural filler. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43283. 相似文献
179.
Kai Xu Pavel Hrma Jarrett A. Rice Michael J. Schweiger Brian J. Riley Nicole R. Overman Albert A. Kruger 《Journal of the American Ceramic Society》2016,99(9):2964-2970
The feed‐to‐glass conversion, which comprises complex chemical reactions and phase transitions, occurs in the cold cap during nuclear waste vitrification. To investigate the conversion process, we analyzed heat‐treated samples of a simulated high‐level waste feed using X‐ray diffraction, electron probe microanalysis, leaching tests, and residual anion analysis. Feed dehydration, gas evolution, and borate phase formation occurred at temperatures below 700°C before the emerging glass‐forming melt was completely connected. Above 700°C, intermediate aluminosilicate phases and quartz particles gradually dissolved in the continuous borosilicate melt, which expanded with transient foam. Knowledge of the chemistry and physics of feed‐to‐glass conversion will help us control the conversion path by changing the melter feed makeup to maximize the glass production rate. 相似文献
180.
Antivirulence Isoquinolone Mannosides: Optimization of the Biaryl Aglycone for FimH Lectin Binding Affinity and Efficacy in the Treatment of Chronic UTI
下载免费PDF全文
![点击此处可从《ChemMedChem》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Cassie Jarvis Dr. Zhenfu Han Vasilios Kalas Roger Klein Jerome S. Pinkner Dr. Bradley Ford Jana Binkley Dr. Corinne K. Cusumano Dr. Zachary Cusumano Dr. Laurel Mydock‐McGrane Prof. Scott J. Hultgren Prof. James W. Janetka 《ChemMedChem》2016,11(4):367-373
Uropathogenic E. coli (UPEC) employ the mannose‐binding adhesin FimH to colonize the bladder epithelium during urinary tract infection (UTI). Previously reported FimH antagonists exhibit good potency and efficacy, but low bioavailability and a short half‐life in vivo. In a rational design strategy, we obtained an X‐ray structure of lead mannosides and then designed mannosides with improved drug‐like properties. We show that cyclizing the carboxamide onto the biphenyl B‐ring aglycone of biphenyl mannosides into a fused heterocyclic ring, generates new biaryl mannosides such as isoquinolone 22 (2‐methyl‐4‐(1‐oxo‐1,2‐dihydroisoquinolin‐7‐yl)phenyl α‐d ‐mannopyranoside) with enhanced potency and in vivo efficacy resulting from increased oral bioavailability. N‐Substitution of the isoquinolone aglycone with various functionalities produced a new potent subseries of FimH antagonists. All analogues of the subseries have higher FimH binding affinity than unsubstituted lead 22 , as determined by thermal shift differential scanning fluorimetry assay. Mannosides with pyridyl substitution on the isoquinolone group inhibit bacteria‐mediated hemagglutination and prevent biofilm formation by UPEC with single‐digit nanomolar potency, which is unprecedented for any FimH antagonists or any other antivirulence compounds reported to date. 相似文献