全文获取类型
收费全文 | 1238篇 |
免费 | 100篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 9篇 |
化学工业 | 443篇 |
金属工艺 | 19篇 |
机械仪表 | 26篇 |
建筑科学 | 33篇 |
能源动力 | 36篇 |
轻工业 | 295篇 |
水利工程 | 8篇 |
石油天然气 | 4篇 |
无线电 | 52篇 |
一般工业技术 | 178篇 |
冶金工业 | 83篇 |
原子能技术 | 9篇 |
自动化技术 | 145篇 |
出版年
2024年 | 4篇 |
2023年 | 16篇 |
2022年 | 58篇 |
2021年 | 103篇 |
2020年 | 40篇 |
2019年 | 43篇 |
2018年 | 36篇 |
2017年 | 39篇 |
2016年 | 51篇 |
2015年 | 52篇 |
2014年 | 53篇 |
2013年 | 99篇 |
2012年 | 69篇 |
2011年 | 88篇 |
2010年 | 73篇 |
2009年 | 80篇 |
2008年 | 72篇 |
2007年 | 48篇 |
2006年 | 35篇 |
2005年 | 26篇 |
2004年 | 30篇 |
2003年 | 21篇 |
2002年 | 15篇 |
2001年 | 19篇 |
2000年 | 12篇 |
1999年 | 13篇 |
1998年 | 13篇 |
1997年 | 9篇 |
1996年 | 7篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 12篇 |
1992年 | 10篇 |
1991年 | 9篇 |
1990年 | 9篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 8篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 9篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1971年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有1340条查询结果,搜索用时 250 毫秒
211.
Helen Sheldon John Alexander Esther Bridges Lucia Moreira Svetlana Reilly Koon Hwee Ang Dian Wang Salwa Lin Syed Haider Alison H. Banham Adrian L. Harris 《International journal of molecular sciences》2021,22(20)
ELTD1 is expressed in endothelial and vascular smooth muscle cells and has a role in angiogenesis. It has been classified as an adhesion GPCR, but as yet, no ligand has been identified and its function remains unknown. To establish its role, ELTD1 was overexpressed in endothelial cells. Expression and consequently ligand independent activation of ELTD1 results in endothelial-mesenchymal transistion (EndMT) with a loss of cell-cell contact, formation of stress fibres and mature focal adhesions and an increased expression of smooth muscle actin. The effect was pro-angiogenic, increasing Matrigel network formation and endothelial sprouting. RNA-Seq analysis after the cells had undergone EndMT revealed large increases in chemokines and cytokines involved in regulating immune response. Gene set enrichment analysis of the data identified a number of pathways involved in myofibroblast biology suggesting that the endothelial cells had undergone a type II EMT. This type of EMT is involved in wound repair and is closely associated with inflammation implicating ELTD1 in these processes. 相似文献
212.
Amitesh Maiti William L. Shaw Samantha M. Clarke Christie Fox Lucia A. Ke William N. Cheung Mark A. Burton Graham D. Kosiba Christian D. Grant Richard H. Gee 《Propellants, Explosives, Pyrotechnics》2024,49(2):e202300253
While most performance metrics of high-explosive (HE) based devices like detonation velocity, detonation pressure, and energy output are expected to degrade over time, the evolution of initiation threshold appears less clear, with claims of both increasing and decreasing trends in threshold having been made in the literature. This work analyzes D-optimally designed sequential binary test data for a few thermally conditioned porous-powder and polymer-bonded HE initiator systems using a Bayesian likelihood method employing the probit regression model. We find that in most cases the initiation threshold decreases (i. e., sensitivity increases) upon accelerated thermal conditioning. However, such results are nuanced and influenced by factors like the contact area of initiating stimulus, HE characteristics like density and specific surface area, as well as possible thermally induced changes to other materials and interfaces involved. 相似文献
213.
Lucia M. Ruiz-Perera Anna L. Hving Kazuko E. Schmidt Sule Cenan Max Wohllebe Johannes F. W. Greiner Christian Kaltschmidt Matthias Simon Cornelius Knabbe Barbara Kaltschmidt 《International journal of molecular sciences》2021,22(17)
Neuroprotection from oxidative stress is critical during neuronal development and maintenance but also plays a major role in the pathogenesis and potential treatment of various neurological disorders and neurodegenerative diseases. Emerging evidence in the murine system suggests neuroprotective effects of blood plasma on the aged or diseased brain. However, little is known about plasma-mediated effects on human neurons. In the present study, we demonstrate the neuroprotective effect mediated by human plasma and the most abundant plasma–protein human serum albumin against oxidative stress in glutamatergic neurons differentiated from human neural crest-derived inferior turbinate stem cells. We observed a strong neuroprotective effect of human plasma and human serum albumin against oxidative stress-induced neuronal death on the single cell level, similar to the one mediated by tumor necrosis factor alpha. Moreover, we detected neuroprotection of plasma and human serum albumin against kainic acid-induced excitatory stress in ex vivo cultured mouse hippocampal tissue slices. The present study provides deeper insights into plasma-mediated neuroprotection ultimately resulting in the development of novel therapies for a variety of neurological and, in particular, neurodegenerative diseases. 相似文献
214.
Lomonaco S Decastelli L Nucera D Gallina S Manila Bianchi D Civera T 《International journal of food microbiology》2009,128(3):516-520
L. monocytogenes represents a primary concern in the production of Gorgonzola, a Protected Designation of Origin (PDO) Italian blue-veined cheese produced only in the Piedmont and Lombardy regions. L. monocytogenes isolates (N=95) obtained from Gorgonzola rinds, paste, and production/ripening environments were serotyped and then genotyped using Pulsed Field Gel Electrophoresis (PFGE). The goal of this study was to investigate the variability of L. monocytogenes PFGE-types across different PDO Gorgonzola manufacturers (N=22). The majority of the strains (88%) were serotyped as 1/2a. PFGE identified 2 major pulse-types grouping 62 strains, detected from different plants and years, suggesting the presence of persistent and niche-adapted L. monocytogenes. In 9 plants, environmental strains shared the same pulse-types with strains from rinds or paste, suggesting a possible transmission pathway. Encouragingly, L. monocytogenes was retrieved from only 1 paste, indicating that production processes were under control in 21 plants. In the remaining plant, un-effective pasteurization or cross-contamination during production processes could be the cause of the contamination. Consequently, it is imperative that producers operate under the total respect of the Good Manufacturing Practices and following the principles of the Hazard Analysis Critical Control Point plans, in order to contain contamination throughout the whole processing. 相似文献
215.
Ana María Zrate Christian Espinosa-Bustos Simn Guerrero Anglica Fierro Felipe Oyarzún-Ampuero Andrew F. G. Quest Lucia Di Marcotullio Elena Loricchio Miriam Caimano Andrea Calcaterra Matías Gonzlez-Quiroz Adam Aguirre Jaime Melndez Cristian O. Salas 《International journal of molecular sciences》2021,22(16)
The Smoothened (SMO) receptor is the most druggable target in the Hedgehog (HH) pathway for anticancer compounds. However, SMO antagonists such as vismodegib rapidly develop drug resistance. In this study, new SMO antagonists having the versatile purine ring as a scaffold were designed, synthesised, and biologically tested to provide an insight to their mechanism of action. Compound 4s was the most active and the best inhibitor of cell growth and selectively cytotoxic to cancer cells. 4s induced cell cycle arrest, apoptosis, a reduction in colony formation and downregulation of PTCH and GLI1 expression. BODIPY-cyclopamine displacement assays confirmed 4s is a SMO antagonist. In vivo, 4s strongly inhibited tumour relapse and metastasis of melanoma cells in mice. In vitro, 4s was more efficient than vismodegib to induce apoptosis in human cancer cells and that might be attributed to its dual ability to function as a SMO antagonist and apoptosis inducer. 相似文献
216.
Schuehle Pfeiffer CE King DA Lucia LM Cabrera-Diaz E Acuff GR Randel RD Welsh TH Oliphint RA Curley KO Vann RC Savell JW 《Meat science》2009,81(2):300-306
To test the influence of transportation stress and temperament on shedding of Escherichia coli O157:H7, cattle (n=150) were classified at various stages of production as Excitable, Intermediate or Calm based on a variety of disposition scores. Presence of E. coli O157:H7 was determined by rectal swabs from live animals and from colons collected postmortem. Percentage of cattle shedding E. coli O157:H7 at arrival at the feedlot was approximately equal among temperament groups. Before shipment to the processing facility, a higher (P=0.03) proportion of cattle from the Calm group shed E. coli O157:H7 compared to the other temperament groups. When pooled across all sampling periods, cattle from the Calm group had a greater percentage test positive for E. coli O157:H7. Neither the acute stressor of transportation nor a more excitable temperament led to increased shedding of E. coli O157:H7 in cattle. 相似文献
217.
HS-SPME–GC–MS analysis of Aglianico del Vulture red wine from Southern Italy showed the presence of ethyl acetate, 3-methyl-1-butanol, 3-methylbutyl acetate, ethyl hexanoate, diethyl butanedioate, ethyl octanoate, and ethyl decanoate. Thermal treatment for 24 h in the 20–60 °C range showed that for most of the compounds analysed the simple transition from 20 to 30 °C induces a significant modification on the composition of volatile compounds. A sharp decrease was observed for ethyl acetate, diethyl butanedioate, and 3-methylbutyl acetate; a moderate decrease was observed for ethyl hexanoate, while an increase was observed for 3-methyl-1-butanol, ethyl octanoate, and ethyl decanoate. The temperature of 40 °C induces the maximum evolution of this type of compound. Higher temperatures induce a reduction of volatile compounds in wine. Irradiation of Barolo (red wine, Northern Italy), Amarone (red wine, Northern Italy), and Brunello di Montalcino (red wine, Central Italy), at 20 °C was performed with a 13 W neon lamp. 3-Methyl-1-butanol was affected by the irradiation. In the case of Barolo and Amarone, we observed a moderate increase, while, for Brunello di Montalcino, a decrease was observed. In the same way, esters were degraded during irradiation. In the red wine one or more components (phenols?) are able to protect esters from photodegradation. In diethyl butanedioate and ethyl hexanoate, octanoate, and decanoate we observed an initial increase of the concentration of the esters in some cases. 相似文献
218.
Nicola Della Ca' Bartolo Gabriele Giuseppe Ruffolo Lucia Veltri Tito Zanetta Mirco Costa 《Advanced Synthesis \u0026amp; Catalysis》2011,353(1):133-146
The reactions of propargyl alcohols with carbon dioxide in supercritical carbon dioxide or in acetonitrile with gaseous carbon dioxide in the presence of organic bases as catalysts have been examined. Bicyclic guanidines are effective catalysts for the formation of α‐methylene cyclic carbonates under mild reaction conditions. Oxoalkyl carbonates, oxoalkyl carbamates or α‐methyleneoxazolidinones are obtained in high yields and good selectivities in one‐step starting from propargyl alcohols and an external nucleophile (alcohols or amines) using bicyclic guanidines as catalysts in supercritical carbon dioxide. Propargylic diols under the same reaction conditions underwent a rearrangement process instead of carbon dioxide insertion whereas in the presence of an external nucleophile the formation of oxocarbonates, oxocarbamates or cyclic carbamates was achieved in satisfactory yields. 相似文献
219.
Orazio A. Attanasi Stefano Berretta Lucia De Crescentini Gianfranco Favi Gianluca Giorgi Fabio Mantellini Simona Nicolini 《Advanced Synthesis \u0026amp; Catalysis》2011,353(4):595-605
The zinc(II) triflate‐catalyzed synthesis of highly functionalized pyrroles is described. The sequence involves the preliminary preparation of α‐aminohydrazones by Michael addition of primary amines to 1,2‐diaza‐1,3‐dienes. The treatment of these intermediates with dialkyl acetylenedicarboxylates produces α‐(N‐enamino)‐hydrazones that are converted into the corresponding pyrroles. The substituents on the carbon in position four of 1,2‐diaza‐1,3‐dienes drive the regioselectivity of the ring closure process. Starting from 4‐aminocarbonyl‐1,2‐diaza‐1,3‐dienes only dialkyl 1‐substituted 5‐aminocarbonyl‐1H‐pyrrole‐2,3‐dicarboxylates are achieved by Lewis acid‐catalyzed ring closure. A screening of several Lewis/Brønsted acid catalysts is performed. Zinc(II) triflate is the most efficient catalyst. Under similar reaction conditions, employing 4‐alkoxycarbonyl‐1,2‐diaza‐1,3‐dienes, only 4‐hydroxy‐1H‐pyrrole‐2,3‐dicarboxylates are synthesized. These latter reactions can be accomplished regioselectively also in one pot. Using 4‐aminocarbonyl‐1,2‐diaza‐1,3‐dienes, diamines and dialkyl acetylenedicarboxylates the sequence provides the corresponding α,ω‐di(N‐pyrrolyl)alkanes. 相似文献
220.
Sara Duce Fabio Pesciaioli Lucia Gramigna Luca Bernardi Andrea Mazzanti Alfredo Ricci Giuseppe Bartoli Giorgio Bencivenni 《Advanced Synthesis \u0026amp; Catalysis》2011,353(6):860-864
The first catalytic asymmetric Pictet–Spengler reaction of isatins is presented. BINOL‐derived phosphoric acids were found to be competent catalysts for this transformation, giving challenging spirooxindole structures bearing a quaternary stereocentre with generally good results. The 1,2,3,4‐tetrahydro‐β‐carboline products (spiroindolinones) are the core of some newly discovered anti‐malarial agents. 相似文献