全文获取类型
收费全文 | 7715篇 |
免费 | 52篇 |
专业分类
电工技术 | 30篇 |
综合类 | 1篇 |
化学工业 | 246篇 |
金属工艺 | 24篇 |
机械仪表 | 24篇 |
建筑科学 | 27篇 |
能源动力 | 33篇 |
轻工业 | 70篇 |
水利工程 | 4篇 |
石油天然气 | 3篇 |
无线电 | 126篇 |
一般工业技术 | 234篇 |
冶金工业 | 6762篇 |
原子能技术 | 15篇 |
自动化技术 | 168篇 |
出版年
2021年 | 13篇 |
2020年 | 9篇 |
2019年 | 19篇 |
2018年 | 14篇 |
2017年 | 23篇 |
2016年 | 26篇 |
2015年 | 15篇 |
2014年 | 29篇 |
2013年 | 41篇 |
2012年 | 23篇 |
2011年 | 54篇 |
2010年 | 38篇 |
2009年 | 30篇 |
2008年 | 37篇 |
2007年 | 52篇 |
2006年 | 34篇 |
2005年 | 45篇 |
2004年 | 30篇 |
2003年 | 44篇 |
2002年 | 21篇 |
2001年 | 25篇 |
2000年 | 22篇 |
1999年 | 228篇 |
1998年 | 2144篇 |
1997年 | 1174篇 |
1996年 | 836篇 |
1995年 | 440篇 |
1994年 | 374篇 |
1993年 | 400篇 |
1992年 | 56篇 |
1991年 | 103篇 |
1990年 | 66篇 |
1989年 | 91篇 |
1988年 | 83篇 |
1987年 | 87篇 |
1986年 | 87篇 |
1985年 | 67篇 |
1984年 | 11篇 |
1983年 | 24篇 |
1982年 | 37篇 |
1981年 | 64篇 |
1980年 | 77篇 |
1979年 | 16篇 |
1978年 | 39篇 |
1977年 | 159篇 |
1976年 | 357篇 |
1975年 | 25篇 |
1974年 | 17篇 |
1970年 | 9篇 |
1969年 | 9篇 |
排序方式: 共有7767条查询结果,搜索用时 15 毫秒
1.
Lissy Z. F. Gross Mariana Sacerdoti Prof. Albrecht Piiper Prof. Stefan Zeuzem Dr. Alejandro E. Leroux Dr. Ricardo M. Biondi 《ChemMedChem》2020,15(18):1682-1690
Angiotensin converting enzyme 2 (ACE2) is the human receptor that interacts with the spike protein of coronaviruses, including the one that produced the 2020 coronavirus pandemic (COVID-19). Thus, ACE2 is a potential target for drugs that disrupt the interaction of human cells with SARS-CoV-2 to abolish infection. There is also interest in drugs that inhibit or activate ACE2, that is, for cardiovascular disorders or colitis. Compounds binding at alternative sites could allosterically affect the interaction with the spike protein. Herein, we review biochemical, chemical biology, and structural information on ACE2, including the recent cryoEM structures of full-length ACE2. We conclude that ACE2 is very dynamic and that allosteric drugs could be developed to target ACE2. At the time of the 2020 pandemic, we suggest that available ACE2 inhibitors or activators in advanced development should be tested for their ability to allosterically displace the interaction between ACE2 and the spike protein. 相似文献
2.
Makrina A. Chairopoulou Fabian Kratzer Roland Gross Michael Herrmann Ulrich Teipel 《化学工程与技术》2020,43(5):904-912
Thermogravimetric analysis of a coccolith-containing biogenic broth showed a three-step degradation process. According to this system behavior, the biogenic broth was heated to specific temperatures and characterized in terms of its morphology, surface chemistry, and crystallinity. The elemental and organic composition of the treated samples was also evaluated and compared to the reference material. The presented results were acquired in an effort to exploit pretreatment scenarios for such a biogenic system that would improve and support a separation process. 相似文献
3.
BF Habbick JL Nanson RE Snyder RE Casey AL Schulman 《Canadian Metallurgical Quarterly》1996,87(3):204-207
Ethers and thioethers of monosaccharides have been synthesised which show potent toxicity to mouse (LD50 > or = 4 g.kg-1 O.W. and 0.2 to 1.5 g.kg-1 I.P.W.). A study of calcium antagonist activity for the full series of compounds indicated that the activity was similar for both O- and S- ethers and maximum activities were observed for monoacetoneglucose ethers possessing carbon chain close to 8 carbons. 相似文献
4.
5.
Event-related desynchronization (ERD) was studied in 10 young (mean age = 19.1) and 10 older (mean age = 62.8) subjects during a verbal recognition task. The attention load of the task varied according to the difficulty of discriminating between targets and distractors. EEG recorded from 29 electrodes was used to compute ERD from 14 source derivations in 125 ms intervals. Thereafter, it was displayed as spatiotemporal maps. The results show that attention influences the characteristics of EEG desynchronization. In young subjects, ERD is more pronounced and more widespread when the attentional load is high. In the elderly, differences between the two attention conditions are less marked. ANOVA reveals main effects of attention and time. The significant 'attention x time x age group' interaction confirms the presence of different brain activation patterns in the two age groups in relation to attention load. 相似文献
6.
JJ Jiménez-Nácher N de Alonso B Vega A del Río JL Moya V Barrios A Hurtado 《Canadian Metallurgical Quarterly》1993,193(6):290-292
Pericardial effusion (PE) as a hypothyroidism associated sign, is something that can be found with relative frequency; nevertheless, cardiac tamponade (CT) as the first sign of this disease may be considered exceptional especially in young patients. We report a 31 years old woman with clinical symptoms and signs of CT that in the forward workshop was diagnosed of primary hypothyroidism as cause of the CT. We shortly describe the case and review the literature, emphasizing the importance of the knowledge of CT trigger factors in myxedematous PE, as well as its usual benign evolution with hormonal treatment, without recurrences of the CT after pericardiocentesis is performed. This justify a conservative approach, in spite of the slow resolution of the PE what can take as long as 1.5 years. 相似文献
7.
JM Rodríguez J Arias Díaz C García Carreras J Torres Melero JL Balibrea 《Canadian Metallurgical Quarterly》1994,9(5):304-310
Reaction of bacterial adhesins with complementary receptors on the surfaces of mucosal respiratory, gastrointestinal and genitourinary cells leads to bacterial adhesion to the human body. This is the first step in the sequence of events leading to infection. It has been observed that subinhibitory concentrations (sub-MICs) of some antibiotics are able to reduce bacterial adhesion. The pharmacokinetic curves of antibiotics show that these sub-MICs are present in tissues during a typical course of therapy. This study investigated the ability of sub-MICs of seven macrolides and four fluoroquinolones to reduce adhesiveness of Staphylococcus aureus to human buccal cells. The literature generally reports data for only one antibiotic at a time. To obtain an overall view of the findings of eleven antibiotics together, the data have been normalized according to the molecular weight of each antibiotic and the dose-effect curves determined. 相似文献
8.
QY Liu AE Schaffner YH Chang K Vaszil JL Barker 《Canadian Metallurgical Quarterly》1997,33(6):848-864
Embryonic rat hippocampal neurons were cultured in a serum-free defined medium (MEM/N3) either directly on poly-D-lysine (PDL) or on a confluent monolayer of postnatal cortical astrocytes, C6 glioma cells, or Rat2 fibroblasts. Neurons on PDL were grown in MEM/N3 or in MEM/N3 conditioned for 24 h by astrocytes or C6 cells. Membrane capacitance (Cm) and gamma-aminobutyric acid (GABA)-, glycine-, kainate-, and N-methyl-D-aspartate (NMDA)-induced currents were quantified using whole-cell patch-clamp recordings. Cm as well as the amplitude and the density of these currents in neurons cultured on astrocytes were significantly greater than those in neurons grown on PDL after 24 and 48 h. C6 cells mimicked astrocytes in promoting Cm and GABA-, glycine-, and NMDA-evoked, but not kainate-evoked, currents. Cm and currents in neurons grown on Rat2 cells were comparable to those in neurons on PDL. Astrocytes maintained in culture for 3 months were noticeably less effective than freshly prepared ones just grown to confluence. Suppression of spontaneous cytoplasmic Ca2+ (Ca[c]2+) elevations in astrocytes by 1,2-bis(2-aminophenoxy) ehane-N, N, N, N-tetraacetic acid acetoxymethyl ester (BAPTA-AM) loaded intracellularly blocked the observed modulatory effects. Medium conditioned by either astrocytes or C6 cells mimicked the effects of direct coculture of neurons on these cells in promoting Cm and amino acid-evoked currents. Inclusion of antagonists at GABA and glutamate receptors in coculture experiments blocked the observed effects. Thus, diffusible substances synthesized and/ or secreted by astrocytes in a Ca(c)2+-dependent manner can regulate neuronal growth and aminoacid receptor function, and these effects may involve neuronal GABA and glutamate receptors. 相似文献
9.
10.