全文获取类型
收费全文 | 93235篇 |
免费 | 12150篇 |
国内免费 | 4276篇 |
专业分类
电工技术 | 14014篇 |
技术理论 | 1篇 |
综合类 | 5944篇 |
化学工业 | 14966篇 |
金属工艺 | 4462篇 |
机械仪表 | 6650篇 |
建筑科学 | 5652篇 |
矿业工程 | 2541篇 |
能源动力 | 2195篇 |
轻工业 | 8379篇 |
水利工程 | 1696篇 |
石油天然气 | 3860篇 |
武器工业 | 923篇 |
无线电 | 14264篇 |
一般工业技术 | 8750篇 |
冶金工业 | 3686篇 |
原子能技术 | 1371篇 |
自动化技术 | 10307篇 |
出版年
2024年 | 197篇 |
2023年 | 1376篇 |
2022年 | 2819篇 |
2021年 | 4696篇 |
2020年 | 3025篇 |
2019年 | 2809篇 |
2018年 | 2930篇 |
2017年 | 3933篇 |
2016年 | 5202篇 |
2015年 | 5923篇 |
2014年 | 7028篇 |
2013年 | 6891篇 |
2012年 | 6684篇 |
2011年 | 6148篇 |
2010年 | 4759篇 |
2009年 | 4700篇 |
2008年 | 4519篇 |
2007年 | 6114篇 |
2006年 | 5903篇 |
2005年 | 4998篇 |
2004年 | 3632篇 |
2003年 | 3297篇 |
2002年 | 2398篇 |
2001年 | 1698篇 |
2000年 | 1263篇 |
1999年 | 1113篇 |
1998年 | 784篇 |
1997年 | 697篇 |
1996年 | 665篇 |
1995年 | 539篇 |
1994年 | 501篇 |
1993年 | 378篇 |
1992年 | 283篇 |
1991年 | 221篇 |
1990年 | 248篇 |
1989年 | 200篇 |
1988年 | 119篇 |
1987年 | 95篇 |
1986年 | 86篇 |
1985年 | 89篇 |
1984年 | 94篇 |
1983年 | 63篇 |
1982年 | 64篇 |
1981年 | 43篇 |
1980年 | 52篇 |
1966年 | 26篇 |
1965年 | 23篇 |
1964年 | 36篇 |
1962年 | 68篇 |
1959年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Svetlana Kononova Ekaterina Litvinova Timur Vakhitov Maria Skalinskaya Stanislav Sitkin 《International journal of molecular sciences》2021,22(8)
The growth in the number of chronic non-communicable diseases in the second half of the past century and in the first two decades of the new century is largely due to the disruption of the relationship between the human body and its symbiotic microbiota, and not pathogens. The interaction of the human immune system with symbionts is not accompanied by inflammation, but is a physiological norm. This is achieved via microbiota control by the immune system through a complex balance of pro-inflammatory and suppressive responses, and only a disturbance of this balance can trigger pathophysiological mechanisms. This review discusses the establishment of homeostatic relationships during immune system development and intestinal bacterial colonization through the interaction of milk glycans, mucins, and secretory immunoglobulins. In particular, the role of fucose and fucosylated glycans in the mechanism of interactions between host epithelial and immune cells is discussed. 相似文献
52.
Several studies, including genome wide association studies (GWAS), have strongly suggested a central role for the ATP-binding cassette transporter subfamily A member 7 (ABCA7) in Alzheimer’s disease (AD). This ABC transporter is now considered as an important genetic determinant for late onset Alzheimer disease (LOAD) by regulating several molecular processes such as cholesterol metabolism and amyloid processing and clearance. In this review we shed light on these new functions and their cross-talk, explaining its implication in brain functioning, and therefore in AD onset and development. 相似文献
53.
Anna Stasiowicz Natalia Rosiak Ewa Tykarska Maciej Kozak Jacek Jenczyk Piotr Szulc Joanna Kobus-Cisowska Kornelia Lewandowska Anita Paziska Wojciech Paziski Judyta Cielecka-Piontek 《International journal of molecular sciences》2021,22(8)
Piperine is an alkaloid that has extensive pharmacological activity and impacts other active substances bioavailability due to inhibition of CYP450 enzymes, stimulation of amino acid transporters and P-glycoprotein inhibition. Low solubility and the associated low bioavailability of piperine limit its potential. The combination of piperine with 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) causes a significant increase in its solubility and, consequently, an increase in permeability through gastrointestinal tract membranes and the blood–brain barrier. X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR) were used to characterize interactions between piperine and HP-β-CD. The observed physicochemical changes should be combined with the process of piperine and CD system formation. Importantly, with an increase in solubility and permeability of piperine as a result of interaction with CD, it was proven to maintain its biological activity concerning the antioxidant potential (2,2-diphenyl-1-picryl-hydrazyl-hydrate assay), inhibition of enzymes essential for the inflammatory process and for neurodegenerative changes (hyaluronidase, acetylcholinesterase, butyrylcholinesterase). 相似文献
54.
55.
Bernette Maria Oosterlaken Heiner Friedrich Gijsbertus de With 《Microscopy research and technique》2022,85(1):412-417
Transmission electron microscopy (TEM) is an important analysis technique to visualize (bio)macromolecules and their assemblies, including collagen fibers. Many protocols for TEM sample preparation of collagen involve one or more washing steps to remove excess salts from the dispersion that could hamper analysis when dried on a TEM grid. Such protocols are not standardized and washing times as well as washing solvents vary from procedure to procedure, with each research group typically having their own protocol. Here, we investigate the influence of washing with water, ethanol, but also methanol and 2-propanol, for both mineralized and unmineralized collagen samples via a protocol based on centrifugation. Washing with water maintains the hydrated collagen structure and the characteristic banding pattern can be clearly observed. Conversely, washing with ethanol results in dehydration of the fibrils, often leading to aggregation of the fibers and a less obvious banding pattern, already within 1 min of ethanol exposure. As we show, this process is fully reversible. Similar observations were made for methanol and propanol. Based on these results, a standardized washing protocol for collagenous samples is proposed. 相似文献
56.
Excessive cross-linking is a major factor in the resistance to the remodelling of the extracellular matrix (ECM) during fibrotic progression. The role of TGFβ signalling in impairing ECM remodelling has been demonstrated in various fibrotic models. We hypothesised that increased ECM cross-linking by TGFβ contributes to skin fibrosis in Systemic Sclerosis (SSc). Proteomics was used to identify cross-linking enzymes in the ECM of primary human dermal fibroblasts, and to compare their levels following treatment with TGFβ-1. A significant upregulation and enrichment of lysyl-oxidase-like 1, 2 and 4 and transglutaminase 2 were found. Western blotting confirmed the upregulation of lysyl hydroxylase 2 in the ECM. Increased transglutaminase activity in TGFβ-1 treated ECM was revealed from a cell-based assay. We employed a mass spectrometry-based method to identify alterations in the ECM cross-linking pattern caused by TGFβ-1. Cross-linking sites were identified in collagens I and V, fibrinogen and fibronectin. One cross-linking site in fibrinogen alpha was found only in TGFβ-treated samples. In conclusion, we have mapped novel cross-links between ECM proteins and demonstrated that activation of TGFβ signalling in cultured dermal fibroblasts upregulates multiple cross-linking enzymes in the ECM. 相似文献
57.
58.
59.
Zeyu He Jiayue Han Xiaoyang Du Luye Cao Jun Wang Caijun Zheng Hui Lin Silu Tao 《Advanced functional materials》2021,31(37):2103988
Emerging graphene/organic phototransistors are eye-catching technologies owing to their unique merits including easy/low-cost fabrication, temperature independent, and achieving various functions. However, their development in the near-infrared (NIR) region is experiencing a bottleneck of inferior sensitivity due to low exciton dissociation efficiency and inefficient charge extraction rate. Here, a novel-design solution-processed graphene/organic NIR phototransistor is reported, that is, creatively introducing electron extraction layer of ZnO on graphene channel and employing organic ternary bulk heterojunction as photosensitive layer, successfully breaking that bottleneck. The phototransistor exhibits a high responsivity of 6.1 × 106 A W−1, a superior detectivity of 2.4 × 1013 Jones, and a remarkable minimum detection power of 1.75 nW cm−2 under 850 nm radiation. Considering its excellent NIR detection performance, a noncontact transmission-type pulse monitoring is carried out with no external circuit support, from which human pulse signal and heart rate can be displayed in real time. The phototransistor, interestingly, can be switched into a photomemory function with a retention time of 1000 s in the atmosphere through a gate voltage of −20 V. The design takes the characteristics of graphene/organic phototransistors to a higher level, beyond the limit of sensitivity, and opens up a novel approach for developing multifunction devices. 相似文献
60.
Amyloid precursor protein (APP) is a type 1 transmembrane glycoprotein, and its homologs amyloid precursor-like protein 1 (APLP1) and amyloid precursor-like protein 2 (APLP2) are highly conserved in mammals. APP and APLP are known to be intimately involved in the pathogenesis and progression of Alzheimer’s disease and to play important roles in neuronal homeostasis and development and neural transmission. APP and APLP are also expressed in non-neuronal tissues and are overexpressed in cancer cells. Furthermore, research indicates they are involved in several cancers. In this review, we examine the biological characteristics of APP-related family members and their roles in cancer. 相似文献