全文获取类型
收费全文 | 2122篇 |
免费 | 159篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 30篇 |
化学工业 | 633篇 |
金属工艺 | 31篇 |
机械仪表 | 42篇 |
建筑科学 | 67篇 |
能源动力 | 55篇 |
轻工业 | 373篇 |
水利工程 | 5篇 |
石油天然气 | 15篇 |
无线电 | 184篇 |
一般工业技术 | 331篇 |
冶金工业 | 279篇 |
原子能技术 | 13篇 |
自动化技术 | 228篇 |
出版年
2024年 | 6篇 |
2023年 | 25篇 |
2022年 | 106篇 |
2021年 | 126篇 |
2020年 | 49篇 |
2019年 | 76篇 |
2018年 | 79篇 |
2017年 | 64篇 |
2016年 | 86篇 |
2015年 | 60篇 |
2014年 | 76篇 |
2013年 | 130篇 |
2012年 | 107篇 |
2011年 | 126篇 |
2010年 | 90篇 |
2009年 | 101篇 |
2008年 | 86篇 |
2007年 | 80篇 |
2006年 | 64篇 |
2005年 | 50篇 |
2004年 | 62篇 |
2003年 | 36篇 |
2002年 | 47篇 |
2001年 | 27篇 |
2000年 | 25篇 |
1999年 | 31篇 |
1998年 | 89篇 |
1997年 | 82篇 |
1996年 | 46篇 |
1995年 | 31篇 |
1994年 | 25篇 |
1993年 | 30篇 |
1992年 | 20篇 |
1991年 | 19篇 |
1990年 | 10篇 |
1989年 | 8篇 |
1988年 | 9篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1980年 | 8篇 |
1979年 | 12篇 |
1978年 | 7篇 |
1977年 | 8篇 |
1976年 | 13篇 |
1974年 | 3篇 |
1973年 | 5篇 |
1968年 | 3篇 |
排序方式: 共有2286条查询结果,搜索用时 15 毫秒
101.
The ubiquitous n-Izod test is universal in its use yet condemned by its critics. Rather than criticize the test we have undertaken a course of study to understand it. In this work we report the photographic results taken at short exposure times with various delays after contact is made by the hammer. The photographic studies were made on polycarbonate and on modified and unmodified poly(vinyl chloride) with the notch radius as a variable. These results show that the damage is always contained within the notch. This permits an estimate of the strain rate, which depends on notch diameter. Instrumented n-Izod measurements show that most of the energy is absorbed before little bending takes place, meaning that the sample is primarily in tension. These observations lead to the conclusion that the test is a high speed tensile test whose strain rate can be varied by changing the notch radius. Microscopic measurements show that, when toughening nylon 6, with small (<200 nm) core//shell particles, the matrix suffers large local ductile deformations without particle cavitation. Rubber cavitation does not occur until after the particles have been deformed by the fracture process. 相似文献
102.
103.
Gangliosides are effective biochemical markers of brain pathologies, being also in the focus of research as potential therapeutic targets. Accurate brain ganglioside mapping is an essential requirement for correlating the specificity of their composition with a certain pathological state and establishing a well-defined set of biomarkers. Among all bioanalytical methods conceived for this purpose, mass spectrometry (MS) has developed into one of the most valuable, due to the wealth and consistency of structural information provided. In this context, the present article reviews the achievements of MS in discovery and structural analysis of gangliosides associated with severe brain pathologies. The first part is dedicated to the contributions of MS in the assessment of ganglioside composition and role in the specific neurodegenerative disorders: Alzheimer’s and Parkinson’s diseases. A large subsequent section is devoted to cephalic disorders (CD), with an emphasis on the MS of gangliosides in anencephaly, the most common and severe disease in the CD spectrum. The last part is focused on the major accomplishments of MS-based methods in the discovery of ganglioside species, which are associated with primary and secondary brain tumors and may either facilitate an early diagnosis or represent target molecules for immunotherapy oriented against brain cancers. 相似文献
104.
Laís Reis-das-Mercês Tatiana Vinasco-Sandoval Rafael Pompeu Aline Cruz Ramos Ana K. M. Anaissi Samia Demachki Paulo Pimentel de Assumpo Amanda F. Vidal ndrea Ribeiro-dos-Santos Leandro Magalhes 《International journal of molecular sciences》2022,23(2)
Gastric cancer (GC) is the fifth most common type of cancer and the third leading cause of cancer death in the world. It is a disease that encompasses a variety of molecular alterations, including in non-coding RNAs such as circular RNAs (circRNAs). In the present study, we investigated hsa_circ_0000211, hsa_circ_0000284, hsa_circ_0000524, hsa_circ_0001136 and hsa_circ_0004771 expression profiles using RT-qPCR in 71 gastric tissue samples from GC patients (tumor and tumor-adjacent samples) and volunteers without cancer. In order to investigate the suitability of circRNAs as minimally invasive biomarkers, we also evaluated their expression profile through RT-qPCR in peripheral blood samples from patients with and without GC (n = 41). We also investigated the predicted interactions between circRNA-miRNA-mRNA and circRNA-RBP using the KEGG and Reactome databases. Overall, our results showed that hsa_circ_0000211, hsa_circ_0000284 and hsa_circ_0004771 presented equivalent expression profiles when analyzed by different methods (RNA-Seq and RT-qPCR) and different types of samples (tissue and blood). Further, functional enrichment results identified important signaling pathways related to GC. Thus, our data support the consideration of circRNAs as new, minimally invasive biomarkers capable of aiding in the diagnosis of GC and with great potential to be applied in clinical practice. 相似文献
105.
Lollo PC Cruz AG Morato PN Moura CS Carvalho-Silva LB Oliveira CA Faria JA Amaya-Farfan J 《Journal of dairy science》2012,95(7):3549-3558
Intense physical activity results in a substantial volume of stress and hence a significant probability of immunosuppression in athletes, with milk proteins being, perhaps, the most recommended protein supplements. Consumption of a probiotic cheese can attenuate immune suppression induced by exhausting exercise in rats. A popular Brazilian fresh cheese (Minas Frescal cheese) containing Lactobacillus acidophilus LA14 and Bifidobacterium longum BL05 was fed for 2wk to adult Wistar rats, which then were brought to exhaustion on the treadmill. Two hours after exhaustion, the rats were killed and material was collected for the determination of serum uric acid, total and high-density lipoprotein cholesterol fraction, total protein, triacylglycerols, aspartate aminotransferase, alanine aminotransferase, creatine kinase, and blood cell (monocyte, lymphocyte, neutrophil, and leukocyte) counts. Exercise was efficient in reducing lymphocyte counts, irrespective of the type of ingested cheese, but the decrease in the group fed the probiotic cheese was 22% compared with 48% in the animals fed regular cheese. Monocyte counts were unaltered in the rats fed probiotic cheese compared with a significant decrease in the rats fed the regular cheese. Most importantly, ingestion of the probiotic cheese resulted in a >100% increase in serum high-density lipoprotein cholesterol and a 50% decrease in triacylglycerols. We conclude that probiotic Minas Frescal cheese may be a viable alternative to enhance the immune system and could be used to prevent infections, particularly those related to the physical overexertion of athletes. 相似文献
106.
Noala Vicensoto Moreira Milhan William Chiappim Aline da Graa Sampaio Mariana Raquel da Cruz Vegian Rodrigo Svio Pessoa Cristiane Yumi Koga-Ito 《International journal of molecular sciences》2022,23(8)
The activation of water by non-thermal plasma creates a liquid with active constituents referred to as plasma-activated water (PAW). Due to its active constituents, PAW may play an important role in different fields, such as agriculture, the food industry and healthcare. Plasma liquid technology has received attention in recent years due to its versatility and good potential, mainly focused on different health care purposes. This interest has extended to dentistry, since the use of a plasma–liquid technology could bring clinical advantages, compared to direct application of non-thermal atmospheric pressure plasmas (NTAPPs). The aim of this paper is to discuss the applicability of PAW in different areas of dentistry, according to the published literature about NTAPPs and plasma–liquid technology. The direct and indirect application of NTAPPs are presented in the introduction. Posteriorly, the main reactors for generating PAW and its active constituents with a role in biomedical applications are specified, followed by a section that discusses, in detail, the use of PAW as a tool for different oral diseases. 相似文献
107.
M.S. Callén M.T. de la Cruz S. Marinov R. Murillo M. Stefanova A.M. Mastral 《Fuel Processing Technology》2007
The electron beam technology (EBT), proven treatment for SO2 and NOx removal, is applied to different power stations as hot gas cleaning system. In this paper, an assessment of this technique installed in a Bulgarian power station on organic emissions is analyzed. The Polycyclic Aromatic Hydrocarbons (PAH) content, not only emitted in the gas phase but also trapped in the solid phase, has been carried out before and after the irradiation. The main aim has been to know whether the EBT affects organic emissions, like PAH, as it happens with inorganic pollutants, like SO2 and NOx, studying EBT effects from an organic environmental point of view. 相似文献
108.
An approach to control integrating processes with elevated deadtime using a Smith predictor sliding mode controller is presented. A PID sliding surface and an integrating first-order plus deadtime model have been used to synthesize the controller. Since the performance of existing controllers with a Smith predictor decrease in the presence of modeling errors, this paper presents a simple approach to combining the Smith predictor with the sliding mode concept, which is a proven, simple, and robust procedure. The proposed scheme has a set of tuning equations as a function of the characteristic parameters of the model. For implementation of our proposed approach, computer based industrial controllers that execute PID algorithms can be used. The performance and robustness of the proposed controller are compared with the Matausek-Mici? scheme for linear systems using simulations. 相似文献
109.
Bruno N. Nunes Adriano G. Cruz Jose A.F. Faria Anderson S. Sant Ana Ramon Silva Mirian R.L. Moura 《Food Control》2010,21(1):50-54
The objective of the study was to evaluate the hygienic conditions and practices of commercial foods of plant origin in establishments and street marketed by street vendors in cities in the State of Rio de Janeiro, Brazil. Forty different sales points were evaluated (establishments that prepared and sold fruit juices and street vendors that commercialized fresh coconut water, sugarcane juice and orange juice) using a questionnaire with 12 items, divided into three blocks (salesmen/handlers, operations, installations). The results indicated that the activities related to the commerce of fruit beverages in the cities of São Gonçalo and Rio de Janeiro required the elaboration of a set of actions by the Sanitary Vigilance Agency in order to improve the hygienic and sanitary level and minimize health risk to consumers. Important requirements in the legislation relevant to this type of food are still not followed; adequate packaging and storage of the raw material, obtaining the raw material from registered suppliers, hygiene of the handlers and adequate management of wastes produced during the activities in question are amongst the main items deserving attention. 相似文献
110.
Donald F. Santa 《Natural Gas \u0026amp; Electricity》1987,4(2):23-32
An end user can outperform its traditional supplier if the sum of (a) the price of gas paid to a producer or a marketer, (b) the rate paid for pipeline transportation, (c) the rate paid for distributor transportation (or in the alternative, the cost of bypassing the distributor), and (d) any other costs associated with the transaction, is less than the cost of gas currently paid to a distributor or a pipeline supplier. While an end user traditionally has relied on others to purchase, transport and deliver gas and to guarantee against interruption of supply, an end user in a direct purchase arrangement is sometimes responsible for assembling its own chain of supply and for protecting itself against interruption of supply. If an end user can reduce its purchased gas costs and if the risks inherent in arranging for its own supply are acceptable or can be mitigated suitably, a direct purchase arrangement is worth undertaking. 相似文献