首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   3147篇
  免费   221篇
  国内免费   4篇
电工技术   62篇
综合类   1篇
化学工业   849篇
金属工艺   42篇
机械仪表   72篇
建筑科学   152篇
矿业工程   1篇
能源动力   103篇
轻工业   244篇
水利工程   10篇
石油天然气   3篇
武器工业   1篇
无线电   289篇
一般工业技术   574篇
冶金工业   124篇
原子能技术   27篇
自动化技术   818篇
  2024年   5篇
  2023年   41篇
  2022年   130篇
  2021年   148篇
  2020年   76篇
  2019年   89篇
  2018年   100篇
  2017年   92篇
  2016年   144篇
  2015年   113篇
  2014年   145篇
  2013年   219篇
  2012年   203篇
  2011年   230篇
  2010年   192篇
  2009年   191篇
  2008年   177篇
  2007年   165篇
  2006年   118篇
  2005年   93篇
  2004年   117篇
  2003年   96篇
  2002年   63篇
  2001年   50篇
  2000年   42篇
  1999年   35篇
  1998年   24篇
  1997年   20篇
  1996年   34篇
  1995年   26篇
  1994年   24篇
  1993年   19篇
  1992年   19篇
  1991年   10篇
  1990年   6篇
  1989年   11篇
  1988年   2篇
  1987年   12篇
  1986年   5篇
  1985年   15篇
  1984年   17篇
  1983年   9篇
  1982年   7篇
  1981年   7篇
  1980年   3篇
  1979年   6篇
  1978年   4篇
  1977年   6篇
  1975年   3篇
  1973年   3篇
排序方式: 共有3372条查询结果,搜索用时 15 毫秒
991.
This paper presents a new algorithm to generate ray-cast CSG animation frames. We consider sequences of frames where only the objects can move; in this way, we take advantage of the high screen area coherence of this kind of animation. A new definition of bounding box allows us to reduce the number of pixels to be computed for the frames after the first. We associate a CSG subtree and two new flags, denoting if the box has changed in the current frame and if it will change in the next frame, with each box. We show with three examples the advantages of our technique when compared with an algorithm which entirely renders each frame of an animation. Intersections with CSG objects may be reduced to about one-fifth, while the rendering may be computed up to four times faster for the test sequences. © 1998 John Wiley & Sons, Ltd.  相似文献   
992.
Interstitial lung diseases represent a heterogeneous and wide group of diseases in which factors leading to disease initiation and progression are not fully understood. Recent evidence suggests that the lung microbiome might influence the pathogenesis and progression of interstitial lung diseases. In recent years, the utilization of culture-independent methodologies has allowed the identification of complex and dynamic communities of microbes, in patients with interstitial lung diseases. However, the potential mechanisms by which these changes may drive disease pathogenesis and progression are largely unknown. The aim of this review is to discuss the role of the altered lung microbiome in several interstitial lung diseases. Untangling the host–microbiome interaction in the lung and airway of interstitial lung disease patients is a research priority. Thus, lung dysbiosis is a potentially treatable trait across several interstitial lung diseases, and its proper characterization and treatment might be crucial to change the natural history of these diseases and improve outcomes.  相似文献   
993.
Penicillium digitatum is a widespread pathogen responsible for the postharvest decay of citrus, one of the most economically important crops worldwide. Currently, chemical fungicides are still the main strategy to control the green mould disease caused by the fungus. However, the increasing selection and proliferation of fungicide-resistant strains require more efforts to explore new alternatives acting via new or unexplored mechanisms for postharvest disease management. To date, several non-chemical compounds have been investigated for the control of fungal pathogens. In this scenario, understanding the molecular determinants underlying P. digitatum’s response to biological and chemical antifungals may help in the development of safer and more effective non-chemical control methods. In this work, a proteomic approach based on isobaric labelling and a nanoLC tandem mass spectrometry approach was used to investigate molecular changes associated with P. digitatum’s response to treatments with α-sarcin and beetin 27 (BE27), two proteins endowed with antifungal activity. The outcomes of treatments with these biological agents were then compared with those triggered by the commonly used chemical fungicide thiabendazole (TBZ). Our results showed that differentially expressed proteins mainly include cell wall-degrading enzymes, proteins involved in stress response, antioxidant and detoxification mechanisms and metabolic processes such as thiamine biosynthesis. Interestingly, specific modulations in response to protein toxins treatments were observed for a subset of proteins. Deciphering the inhibitory mechanisms of biofungicides and chemical compounds, together with understanding their effects on the fungal physiology, will provide a new direction for improving the efficacy of novel antifungal formulations and developing new control strategies.  相似文献   
994.
Glycogen storage disease type Ia (GSDIa) is an inherited metabolic disorder caused by mutations in the enzyme glucose-6-phosphatase-α (G6Pase-α). Affected individuals develop renal and liver complications, including the development of hepatocellular adenoma/carcinoma and kidney failure. The purpose of this study was to identify potential biomarkers of the evolution of the disease in GSDIa patients. To this end, we analyzed the expression of exosomal microRNAs (Exo-miRs) in the plasma exosomes of 45 patients aged 6 to 63 years. Plasma from age-matched normal individuals were used as controls. We found that the altered expression of several Exo-miRs correlates with the pathologic state of the patients and might help to monitor the progression of the disease and the development of late GSDIa-associated complications.  相似文献   
995.
Hepatocellular carcinoma (HCC) is one of the major causes of cancer-related death. Although the burden of alcohol- and NASH-related HCC is growing, chronic viral hepatitis (HBV and HCV) remains a major cause of HCC development worldwide. The pathophysiology of viral-related HCC includes liver inflammation, oxidative stress, and deregulation of cell signaling pathways. HBV is particularly oncogenic because, contrary to HCV, integrates in the cell DNA and persists despite virological suppression by nucleotide analogues. Surveillance by six-month ultrasound is recommended in patients with cirrhosis and in “high-risk” patients with chronic HBV infection. Antiviral therapy reduces the risks of development and recurrence of HCC; however, patients with advanced chronic liver disease remain at risk of HCC despite virological suppression/cure and should therefore continue surveillance. Multiple scores have been developed in patients with chronic hepatitis B to predict the risk of HCC development and may be used to stratify individual patient’s risk. In patients with HCV-related liver disease who achieve sustained virological response by direct acting antivirals, there is a strong need for markers/scores to predict long-term risk of HCC. In this review, we discuss the most recent advances regarding viral-related HCC.  相似文献   
996.
The analysis of the free-edge stress distributions in composite laminates under uniaxial tension is approached by a finite element technique based on a multi-layer higher-order laminate theory. Several finite elements corresponding to different through-thickness assumed distributions of the displacement unknowns are developed. Numerous stacking sequences are examined in the applications. The results are compared with the ones obtained by various investigators with other modelling approaches. The use of the proposed technique is demonstrated to be simple and effective both for the analysis of in-plane and out-of-plane distributions of intralaminar and, noticeably, interlaminar stress components. © 1998 John Wiley & Sons, Ltd.  相似文献   
997.
In plant grana thylakoid membranes Photosystem II (PSII) associates with a variable number of antenna proteins (LHCII) to form different types of supercomplexes (PSII-LHCII), whose organization is dynamically adjusted in response to light cues, with the C2S2 more abundant in high-light and the C2S2M2 in low-light. Paired PSII-LHCII supercomplexes interacting at their stromal surface from adjacent thylakoid membranes were previously suggested to mediate grana stacking. Here, we present the cryo-electron microscopy maps of paired C2S2 and C2S2M2 supercomplexes isolated from pea plants grown in high-light and low-light, respectively. These maps show a different rotational offset between the two supercomplexes in the pair, responsible for modifying their reciprocal interaction and energetic connectivity. This evidence reveals a different way by which paired PSII-LHCII supercomplexes can mediate grana stacking at diverse irradiances. Electrostatic stromal interactions between LHCII trimers almost completely overlapping in the paired C2S2 can be the main determinant by which PSII-LHCII supercomplexes mediate grana stacking in plants grown in high-light, whereas the mutual interaction of stromal N-terminal loops of two facing Lhcb4 subunits in the paired C2S2M2 can fulfil this task in plants grown in low-light. The high-light induced accumulation of the Lhcb4.3 protein in PSII-LHCII supercomplexes has been previously reported. Our cryo-electron microscopy map at 3.8 Å resolution of the C2S2 supercomplex isolated from plants grown in high-light suggests the presence of the Lhcb4.3 protein revealing peculiar structural features of this high-light-specific antenna important for photoprotection.  相似文献   
998.
The increasing requirement for more sustainability in the transport sector, which is responsible for more than 25% of CO2 emissions worldwide and consumes almost 50% of the world's oil production, creates a growing demand for technological advancement in this field. Cellulosic ethanol, produced from agricultural residues, is an advanced biofuel that meets these needs: it offers excellent greenhouse gas savings based on renewable raw materials that are already available in large quantities worldwide. This essay will outline challenges and opportunities for using advanced biofuels, in this particular case, cellulosic ethanol, to reduce the usage and dependency of fossil fuels and cut greenhouse gas emissions in the transport sector, showcasing Clariant's sunliquid® process technology.  相似文献   
999.
In spite of their value as genetically encodable reporters for imaging in living systems, fluorescent proteins have been used sporadically for stimulated emission depletion (STED) super-resolution imaging, owing to their moderate photophysical resistance, which does not enable reaching resolutions as high as for synthetic dyes. By a rational approach combining steady-state and ultrafast spectroscopy with gated STED imaging in living and fixed cells, we here demonstrate that F99S/M153T/V163A GFP (c3GFP) represents an efficient genetic reporter for STED, on account of no excited state absorption at depletion wavelengths <600 nm and a long emission lifetime. This makes c3GFP a valuable alternative to more common, but less photostable, EGFP and YFP/Citrine mutants for STED imaging studies targeting the green-yellow region of the optical spectrum.  相似文献   
1000.
The COVID-19 pandemic has evidenced the urgent need for the discovery of broad-spectrum antiviral therapies that could be deployed in the case of future emergence of novel viral threats, as well as to back up current therapeutic options in the case of drug resistance development. Most current antivirals are directed to inhibit specific viruses since these therapeutic molecules are designed to act on a specific viral target with the objective of interfering with a precise step in the replication cycle. Therefore, antimicrobial peptides (AMPs) have been identified as promising antiviral agents that could help to overcome this limitation and provide compounds able to act on more than a single viral family. We evaluated the antiviral activity of an amphibian peptide known for its strong antimicrobial activity against both Gram-positive and Gram-negative bacteria, namely Temporin L (TL). Previous studies have revealed that TL is endowed with widespread antimicrobial activity and possesses marked haemolytic activity. Therefore, we analyzed TL and a previously identified TL derivative (Pro3, DLeu9 TL, where glutamine at position 3 is replaced with proline, and the D-Leucine enantiomer is present at position 9) as well as its analogs, for their activity against a wide panel of viruses comprising enveloped, naked, DNA and RNA viruses. We report significant inhibition activity against herpesviruses, paramyxoviruses, influenza virus and coronaviruses, including SARS-CoV-2. Moreover, we further modified our best candidate by lipidation and demonstrated a highly reduced cytotoxicity with improved antiviral effect. Our results show a potent and selective antiviral activity of TL peptides, indicating that the novel lipidated temporin-based antiviral agents could prove to be useful additions to current drugs in combatting rising drug resistance and epidemic/pandemic emergencies.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号