全文获取类型
收费全文 | 46189篇 |
免费 | 6916篇 |
国内免费 | 1526篇 |
专业分类
电工技术 | 2137篇 |
综合类 | 1989篇 |
化学工业 | 12506篇 |
金属工艺 | 2220篇 |
机械仪表 | 1772篇 |
建筑科学 | 4237篇 |
矿业工程 | 1554篇 |
能源动力 | 955篇 |
轻工业 | 6604篇 |
水利工程 | 982篇 |
石油天然气 | 1537篇 |
武器工业 | 223篇 |
无线电 | 4343篇 |
一般工业技术 | 5155篇 |
冶金工业 | 2575篇 |
原子能技术 | 537篇 |
自动化技术 | 5305篇 |
出版年
2024年 | 94篇 |
2023年 | 924篇 |
2022年 | 1920篇 |
2021年 | 3374篇 |
2020年 | 1651篇 |
2019年 | 1709篇 |
2018年 | 1876篇 |
2017年 | 2402篇 |
2016年 | 3529篇 |
2015年 | 3962篇 |
2014年 | 4061篇 |
2013年 | 3943篇 |
2012年 | 2765篇 |
2011年 | 2080篇 |
2010年 | 1765篇 |
2009年 | 1772篇 |
2008年 | 1672篇 |
2007年 | 2722篇 |
2006年 | 2946篇 |
2005年 | 2472篇 |
2004年 | 1527篇 |
2003年 | 1479篇 |
2002年 | 928篇 |
2001年 | 472篇 |
2000年 | 308篇 |
1999年 | 304篇 |
1998年 | 154篇 |
1997年 | 144篇 |
1996年 | 181篇 |
1995年 | 134篇 |
1994年 | 148篇 |
1993年 | 97篇 |
1992年 | 84篇 |
1991年 | 84篇 |
1990年 | 104篇 |
1989年 | 84篇 |
1988年 | 49篇 |
1987年 | 51篇 |
1986年 | 50篇 |
1985年 | 55篇 |
1984年 | 63篇 |
1983年 | 39篇 |
1982年 | 34篇 |
1981年 | 34篇 |
1980年 | 45篇 |
1966年 | 25篇 |
1964年 | 34篇 |
1962年 | 64篇 |
1959年 | 21篇 |
1955年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 235 毫秒
101.
We propose a Discussion Logic-based Text Analytics (DiLTA) framework, which combines theories developed in social science and text mining fields. The framework extracts features that uncover discussion logic and uses these features in analyzing online discussions. A series of models are proposed including conversation disentanglement, coherence analysis, and visualization. Validation experiments showed that DiLTA achieved significantly superior performance over existing text analytics methods in reconstructing internal structure. A case study using DiLTA-enabled visualization on a healthcare forum illustrates the great potential of DiLTA in assisting comprehension of the internal linkage, structure, and logic of online group discussions. 相似文献
102.
Ehsan Yaghoubi Mahdi M. Disfani Arul Arulrajah Jayantha Kodikara 《Soils and Foundations》2019,59(2):443-457
Despite extensive research on the behavior of unsaturated fine-grained materials, there is still a lack of understanding of the volumetric behavior of unsaturated granular materials. In this research, a model has been developed to predict the fundamental volumetric behavior of unsaturated granular materials through loading and wetting state paths. In this regard, a loading-wetting surface was developed in a space of void ratio-moisture ratio-net stress. A distinctive feature of the proposed model is the relative simplicity in obtaining the model parameters using conventional geotechnical testing equipment. Two types of recycled granular materials, commonly applied in unbound pavements were used, namely, recycled crushed brick (CB) and excavation waste rock (WR). The uniqueness of the developed surface was evaluated by employing a number of loading and wetting state paths. The results indicate that the developed surface is unique in its loading state paths; however, it only shows uniqueness in its wetting state paths for stress levels greater than 2000 kPa. The proposed model seeks to introduce the application of the unsaturated soil mechanics theory, for predicting the behavior of granular materials in the field, by providing a practical and cost-effective methodology. 相似文献
103.
Klare M. Lazor Junhui Zhou Kristen E. DeMeester Elizabeth A. D'Ambrosio Dr. Catherine L. Grimes 《Chembiochem : a European journal of chemical biology》2019,20(11):1369-1375
The innate immune system's interaction with bacterial cells plays a pivotal role in a variety of human diseases. Carbohydrate units derived from a component of bacterial cell wall, peptidoglycan (PG), are known to stimulate an immune response. Nonetheless, access to modified late-stage peptidoglycan intermediates is limited due to their synthetic complexity. A method to rapidly functionalize PG fragments is needed to better understand the natural host–PG interactions. Here methyl N,O-hydroxylamine linkers are incorporated onto a synthetic PG derivative, muramyl dipeptide (MDP). The modification of MDP maintained the ability to stimulate a nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) immune response dependent on the expression of nucleotide-binding oligomerization domain-containing protein 2 (Nod2). Intrigued by this modification's maintenance of biological activity, several applications were explored. Methyl N,O-hydroxylamine MDP was amendable to N-hydroxylsuccinimide (NHS) chemistry for bioconjugation to fluorophores as well as a self-assembled monolayer for Nod2 surface plasmon resonance analysis. Finally, linker incorporation was applicable to larger PG fragments, both enzymatically generated from Escherichia coli or chemically synthesized. This methodology provides rapid access to PG probes in one step and allows for the installation of a variety of chemical handles to advance the molecular understanding of PG and the innate immune system. 相似文献
104.
Enhancing the earthquake behavioral responses and post-earthquake evacuation preparedness of building occupants is beneficial to increasing their chances of survival and reducing casualties after the mainshock of an earthquake. Traditionally, training approaches such as seminars, posters, videos or drills are applied to enhance preparedness. However, they are not highly engaging and have limited sensory capabilities to mimic life-threatening scenarios for the purpose of training potential participants. Immersive Virtual Reality (IVR) and Serious Games (SG) as innovative digital technologies can be used to create training tools to overcome these limitations. In this study, we propose an IVR SG-based training system to improve earthquake behavioral responses and post-earthquake evacuation preparedness. Auckland City Hospital was chosen as a case study to test our IVR SG training system. A set of training objectives based on best evacuation practice has been identified and embedded into several training scenarios of the IVR SG. Hospital staff (healthcare and administrative professionals) and visitors were recruited as participants to be exposed to these training scenarios. Participants’ preparedness has been measured along two dimensions: 1) Knowledge about best evacuation practice; 2) Self-efficacy in dealing with earthquake emergencies. Assessment results showed that there was a significant knowledge and self-efficacy increase after the training. In addition, participants acknowledged that it was easy, helpful, and engaging to learn best evacuation practice knowledge through the IVR SG training system. 相似文献
105.
Tomonori Waku Ayane Kasai Akio Kobori Naoki Tanaka 《International journal of molecular sciences》2020,21(24)
Self-assembled peptide nanofibers (NFs) obtained from β-sheet peptides conjugated with drugs, including antigenic peptides, have recently attracted significant attention. However, extensive studies on the interactions of β-sheet peptide NFs with model cell membranes have not been reported. In this study, we investigated the interactions between three types of NFs, composed of PEG-peptide conjugates with different ethylene glycol (EG) lengths (6-, 12- and 24-mer), and dipalmitoylphosphatidylcholine (DPPC) Langmuir membranes. When increasing the EG chain length, those interactions significantly decreased considering measurements in the presence of the NFs of: (i) changes in surface pressure of the DPPC Langmuir monolayers and (ii) surface pressure–area (π–A) compression isotherms of DPPC. Because the observed trend was similar to the EG length dependency with regard to cellular association and cytotoxicity of the NFs that was reported previously, the interaction of NFs with phospholipid membranes represented a crucial factor to determine the cellular association and toxicity of the NFs. In contrast to NFs, no changes were observed with varying EG chain length on the interaction of the building block peptide with the DPPC membrane. The results obtained herein can provide a design guideline on the formulation of β-sheet peptide NFs, which may broaden its potential. 相似文献
106.
107.
ABSTRACTA comprehensive literature review of the existing techniques for removing and repairing of damaged thermal barrier coatings is presented, with the focus on top ceramic coats. The advantages and disadvantages of each technique are compared and assessed. The review shows that there is not a universal method applicable to all coating systems. The selection of the coating removal and repair process must be specific to damaged coating systems, based on their composition, type of damages, and available resources. This review will provide some inside look at various approaches in an effort to meet the different coating repair needs. 相似文献
108.
Nicoletta Pellegrini Paola Vitaglione Daniel Granato Vincenzo Fogliano 《Journal of the science of food and agriculture》2020,100(14):5064-5078
This review summarises 25 years of investigations on antioxidants research in foods and biological fluids and critically analyses the merits and limitations of using the total antioxidant capacity (TAC) measurement in the metabolomic era. An enormous bulk of knowledge was produced regarding the antioxidant capacity of foods and large TAC databases were developed. A direct link between a food TAC value and any health benefit is erroneous and has led to several cases of consumer deception. However, the striking epidemiological evidence associating a high dietary TAC with some disease prevention and the availability of well-constructed TAC databases deserve attention and must be taken into account to establish the usefulness of measuring TAC in both foods and biological samples. The in vivo TAC measurement, usually performed in plasma, is influenced by many external factors, such as dietary habits, as well as environmental and behavioural factors, which are integrated towards homeostatic control by fine physiological mechanisms with high inter-individual variability. Therefore, plasma TAC cannot be considered as a unique biomarker of individual antioxidant status. However, the combined evaluation of plasma TAC with known markers of disease, individual metabolism, inflammation and genetics, as well as with markers of gut microbiota composition and activity, may lead to the identification of populations that are more responsive to food/diet TAC. In this framework, the appropriate use of TAC measurement both in food and in vivo can still provide support for the interpretation of complex phenomena and be a tool for sample screening when making a quick decision toward in-depth research investigations. © 2018 Society of Chemical Industry 相似文献
109.
Loadbearing capacity of infill masonry walls considering the deformation‐based membrane effect 下载免费PDF全文
《Mauerwerk》2018,22(3):151-161
According to currently valid codes, it is not possible to determine the loadbearing capacity of unreinforced infill walls considering the deformation‐based membrane effect by incorporating the exact support conditions. One reason for this is the lack of a validated calculation procedure, which in addition to the equilibrium conditions also realistically represents the compatibility conditions of these systems. In the present paper, therefore, a new non‐linear analytical calculation procedure is presented. The main focus of the analysis of walls subject to area loading is the incorporation of the support conditions and thus the consideration of the deformation‐based membrane compressive force. Through generalised formulation and a standardised notation of the determination equations, different material behaviours and various support conditions can be taken into account with few parameters. On the action side, both lighter loading like wind loads and heavier loading like explosion loads can be considered. Through the implementation of the partial factor concept, it is possible to comply with the requirements of European codes and thus ensure the applicability of the analysis model. 相似文献
110.
自然资源是人类赖以生存的重要资源,随着资源型企业的发展,非再生资源短缺与耗竭状况凸显,环境污染与生态危机非常严峻。京津冀协同发展,必须加强生态环境治理,推进生态文明建设。资源型企业作为京津冀共生体中的基本单元,在京津冀生态文明建设以及产业转型升级中发挥着重要作用。资源型企业生态工程以资源有效利用和环境保护为出发点,重视符合人性化和生态要求的设计,强调经济效益与生态效益之间的协调,旨在提升企业的生命力与综合竞争力。全面推进资源型企业实施生态工程,必须以"绿水青山"理念为引领,树立全员生态责任意识,加强生态工程的科学规划与设计,实现节能减排,提高资源综合利用率,大力推进生态恢复工作,提高生态环境管理水平。 相似文献