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   386篇
  免费   21篇
电工技术   10篇
化学工业   196篇
金属工艺   11篇
机械仪表   12篇
建筑科学   12篇
矿业工程   1篇
能源动力   4篇
轻工业   64篇
石油天然气   4篇
无线电   9篇
一般工业技术   41篇
冶金工业   6篇
原子能技术   1篇
自动化技术   36篇
  2023年   6篇
  2022年   30篇
  2021年   29篇
  2020年   11篇
  2019年   10篇
  2018年   13篇
  2017年   11篇
  2016年   11篇
  2015年   9篇
  2014年   13篇
  2013年   22篇
  2012年   17篇
  2011年   32篇
  2010年   16篇
  2009年   12篇
  2008年   20篇
  2007年   15篇
  2006年   10篇
  2005年   10篇
  2004年   7篇
  2003年   9篇
  2002年   9篇
  2001年   4篇
  2000年   3篇
  1999年   6篇
  1998年   6篇
  1997年   5篇
  1996年   3篇
  1995年   5篇
  1994年   6篇
  1992年   3篇
  1991年   2篇
  1989年   1篇
  1988年   5篇
  1987年   5篇
  1986年   3篇
  1985年   1篇
  1984年   4篇
  1983年   4篇
  1982年   6篇
  1981年   1篇
  1980年   1篇
  1979年   1篇
  1976年   2篇
  1975年   1篇
  1971年   1篇
  1970年   1篇
  1968年   2篇
  1967年   1篇
  1966年   1篇
排序方式: 共有407条查询结果,搜索用时 11 毫秒
101.
The existence of a potential primary central nervous system lymphoma-specific genomic signature that differs from the systemic form of diffuse large B cell lymphoma (DLBCL) has been suggested, but is still controversial. We investigated 19 patients with primary DLBCL of central nervous system (DLBCL CNS) using the TruSeq Amplicon Cancer Panel (TSACP) for 48 cancer-related genes. Next generation sequencing (NGS) analyses have revealed that over 80% of potentially protein-changing mutations were located in eight genes (CTNNB1, PIK3CA, PTEN, ATM, KRAS, PTPN11, TP53 and JAK3), pointing to the potential role of these genes in lymphomagenesis. TP53 was the only gene harboring mutations in all 19 patients. In addition, the presence of mutated TP53 and ATM genes correlated with a higher total number of mutations in other analyzed genes. Furthermore, the presence of mutated ATM correlated with poorer event-free survival (EFS) (p = 0.036). The presence of the mutated SMO gene correlated with earlier disease relapse (p = 0.023), inferior event-free survival (p = 0.011) and overall survival (OS) (p = 0.017), while mutations in the PTEN gene were associated with inferior OS (p = 0.048). Our findings suggest that the TP53 and ATM genes could be involved in the molecular pathophysiology of primary DLBCL CNS, whereas mutations in the PTEN and SMO genes could affect survival regardless of the initial treatment approach.  相似文献   
102.
The fabrication of 45° micromirrors by silicon anisotropic etching in potassium hydroxide (KOH) and tetramethylammonium hydroxide (TMAH) solutions containing organic additives is investigated in this paper. The reflective planes are formed by {110} sidewall planes inclined at 45° towards the Si (100) wafer. Isopropyl alcohol and Triton X-100 surfactant are used as additives, because they are supposed to provide the etch rate ratio R(100)/R(110) > 1, which is necessary for {110} sidewalls development. The fabricated spatial microstructures with 45° sidewalls are examined in terms of the {110} surface roughness and the quality of the {110} sidewall profile. The KOH solution saturated with the alcohol gives the striped {110} surface, though the stripes almost disappear after addition of Triton surfactant to KOH and TMAH etchants. The 45° sidewall profiles fully defined by {110} planes are obtained in KOH as well as TMAH solutions containing additives. The measurements of micromirrors’ reflectivity indicate that replacement of the alcohol by Triton surfactant in the KOH solution reduces the optical power loss caused by the reflection. The achieved reflectivity is comparable with the one obtained by etching in the TMAH solution with surfactant.  相似文献   
103.
104.
Three different bacterial defence mechanisms were identified in the seventeen Lactococcus lactis isolates from starter cultures in three Slovenian dairy plants. Isolates MB18, KR7, PT4, PT13 and PT19 inhibited phage adsorption by means of exopolysaccharides production. The most extensive polysaccharides production was detected in PT19 isolate, which was susceptible only to phage ΦPT19. Eight isolates exhibited nuclease activity, and seven of them were susceptible up to four phages out of thirteen from our collection. Eight isolates possessed the abiB gene, fourteen isolates abiH, two isolates abiJ and one isolate abiQ. Isolates PT27 and PT28 possessed AbiB, AbiH and AbiJ mechanisms as well as inhibition of phage adsorption. Isolate MB18, which was susceptible to one phage only, possessed the abiQ gene, nuclease activity and ability to prevent adsorption of most phages. Isolates PT67 and PT70, possessing only AbiH mechanism, were susceptible to only two phages.  相似文献   
105.
Glioblastoma multiforme (GBM) is a brain tumor with a very poor prognosis. For this reason, researchers worldwide study the impact of the tumor microenvironment in GBM, such as the effect of chemokines. In the present study, we focus on the role of the chemokine CCL18 and its receptors in the GBM tumor. We measured the expression of CCL18, CCR8 and PITPNM3 in the GMB tumor from patients (16 men and 12 women) using quantitative real-time polymerase chain reaction. To investigate the effect of CCL18 on the proliferation and migration of GBM cells, experiments were performed using U-87 MG cells. The results showed that CCL18 expression was higher in the GBM tumor than in the peritumoral area. The women had a decreased expression of PITPNM3 receptor in the GBM tumor, while in the men a lower expression of CCR8 was observed. The hypoxia-mimetic agent, cobalt chloride (CoCl2), increased the expression of CCL18 and PITPNM3 and thereby sensitized U-87 MG cells to CCL18, which did not affect the proliferation of U-87 MG cells but increased the migration of the test cells. The results indicate that GBM cells migrate from hypoxic areas, which may be important in understanding the mechanisms of tumorigenesis.  相似文献   
106.
The role of the environment in amyloid formation based on the fuzzy oil drop model (FOD) is discussed here. This model assumes that the hydrophobicity distribution within a globular protein is consistent with a 3D Gaussian (3DG) distribution. Such a distribution is interpreted as the idealized effect of the presence of a polar solvent—water. A chain with a sequence of amino acids (which are bipolar molecules) determined by evolution recreates a micelle-like structure with varying accuracy. The membrane, which is a specific environment with opposite characteristics to the polar aquatic environment, directs the hydrophobic residues towards the surface. The modification of the FOD model to the FOD-M form takes into account the specificity of the cell membrane. It consists in “inverting” the 3DG distribution (complementing the Gaussian distribution), which expresses the exposure of hydrophobic residues on the surface. It turns out that the influence of the environment for any protein (soluble or membrane-anchored) is the result of a consensus factor expressing the participation of the polar environment and the “inverted” environment. The ratio between the proportion of the aqueous and the “reversed” environment turns out to be a characteristic property of a given protein, including amyloid protein in particular. The structure of amyloid proteins has been characterized in the context of prion, intrinsically disordered, and other non-complexing proteins to cover a wider spectrum of molecules with the given characteristics based on the FOD-M model.  相似文献   
107.
A systematic measurement of ions and 2H/1H, 7Li/6Li, 11B/10B, 18O/ 16O, and 87Sr/86Sr isotopes in feed-waters, permeates, and brines from commercial reverse osmosis (RO) desalination plants in Israel (Ashkelon, Eilat, and Nitzana) and Cyprus (Larnaca) reveals distinctive geochemical and isotopic fingerprints of fresh water generated from desalination of seawater (SWRO) and brackish water (BWRO). The degree of isotope fractionation during the passage of water and solutes through the RO membranes depends on the medium (solvent-water vs. solutes), chemical speciation of the solutes, their charge, and their mass difference. O, H, and Sr isotopes are not fractionated during the RO process. 7Li is preferentially rejected in low pH RO, and B isotope fractionation depends on the pH conditions. Under low pH conditions, B isotopes are not significantly fractionated, whereas at high pH, RO permeates are enriched by 20 per thousand in 11B due to selective rejection of borate ion and preferential permeation of 11B-enriched boric acid through the membrane. The specific geochemical and isotopic fingerprints of SWRO provide a unique tool for tracing "man-made" fresh water as an emerging recharge component of natural water resources.  相似文献   
108.
Neuroinflammation and microglial activation, common components of most neurodegenerative diseases, can be imitated in vitro by challenging microglia cells with Lps. We here aimed to evaluate the effects of agmatine pretreatment on Lps-induced oxidative stress in a mouse microglial BV-2 cell line. Our findings show that agmatine suppresses nitrosative and oxidative burst in Lps-stimulated microglia by reducing iNOS and XO activity and decreasing O2 levels, arresting lipid peroxidation, increasing total glutathione content, and preserving GR and CAT activity. In accordance with these results, agmatine suppresses inflammatory NF-kB, and stimulates antioxidant Nrf2 pathway, resulting in decreased TNF, IL-1 beta, and IL-6 release, and reduced iNOS and COX-2 levels. Together with increased ARG1, CD206 and HO-1 levels, our results imply that, in inflammatory conditions, agmatine pushes microglia towards an anti-inflammatory phenotype. Interestingly, we also discovered that agmatine alone increases lipid peroxidation end product levels, induces Nrf2 activation, increases total glutathione content, and GPx activity. Thus, we hypothesize that some of the effects of agmatine, observed in activated microglia, may be mediated by induced oxidative stress and adaptive response, prior to Lps stimulation.  相似文献   
109.
Misfolded amyloid beta (Aβ) peptides aggregate and form neurotoxic oligomers. Membrane and mitochondrial damages, calcium dysregulation, oxidative stress, and fibril deposits are among the possible mechanisms of Aβ cytotoxicity. Galantamine (GAL) prevents apoptosis induced by Aβ mainly through the ability to stimulate allosterically the α7 nAChRs and to regulate the calcium cytosolic concentration. Here, we examined the cytoprotective effects of two GAL derivatives, namely compounds 4b and 8, against Aβ cytotoxicity on the human neuroblastoma cell line SH-SY5Y. The protective effects were tested at simultaneous administration, pre-incubation and post-incubation, with Aβ. GAL and curcumin (CU) were used in the study as reference compounds. It was found that 4b protects cells in a similar mode as GAL, while compound 8 and CU potentiate the toxic effects of Aβ. Allosteric stimulation of α7 nAChRs is suggested as a possible mechanism of the cytoprotectivity of 4b. These and previous findings characterize 4b as a prospective non-toxic multi-target agent against neurodegenerative disorders with inhibitory activity on acetylcholinesterase, antioxidant, and cytoprotective properties.  相似文献   
110.
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