全文获取类型
收费全文 | 54080篇 |
免费 | 7916篇 |
国内免费 | 2116篇 |
专业分类
电工技术 | 2258篇 |
技术理论 | 2篇 |
综合类 | 2643篇 |
化学工业 | 14004篇 |
金属工艺 | 2577篇 |
机械仪表 | 1853篇 |
建筑科学 | 5032篇 |
矿业工程 | 2631篇 |
能源动力 | 1291篇 |
轻工业 | 6746篇 |
水利工程 | 1149篇 |
石油天然气 | 3579篇 |
武器工业 | 227篇 |
无线电 | 4733篇 |
一般工业技术 | 5835篇 |
冶金工业 | 3303篇 |
原子能技术 | 625篇 |
自动化技术 | 5624篇 |
出版年
2024年 | 107篇 |
2023年 | 1067篇 |
2022年 | 2158篇 |
2021年 | 3666篇 |
2020年 | 1985篇 |
2019年 | 1994篇 |
2018年 | 2143篇 |
2017年 | 2700篇 |
2016年 | 3845篇 |
2015年 | 4315篇 |
2014年 | 4550篇 |
2013年 | 4427篇 |
2012年 | 3372篇 |
2011年 | 2651篇 |
2010年 | 2232篇 |
2009年 | 2204篇 |
2008年 | 2068篇 |
2007年 | 3224篇 |
2006年 | 3371篇 |
2005年 | 2859篇 |
2004年 | 1832篇 |
2003年 | 1765篇 |
2002年 | 1151篇 |
2001年 | 673篇 |
2000年 | 502篇 |
1999年 | 446篇 |
1998年 | 281篇 |
1997年 | 259篇 |
1996年 | 296篇 |
1995年 | 226篇 |
1994年 | 224篇 |
1993年 | 161篇 |
1992年 | 147篇 |
1991年 | 129篇 |
1990年 | 145篇 |
1989年 | 102篇 |
1988年 | 64篇 |
1987年 | 59篇 |
1986年 | 58篇 |
1985年 | 67篇 |
1984年 | 66篇 |
1983年 | 41篇 |
1982年 | 38篇 |
1981年 | 36篇 |
1980年 | 50篇 |
1966年 | 25篇 |
1964年 | 34篇 |
1962年 | 64篇 |
1959年 | 21篇 |
1955年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 34 毫秒
991.
Ryan M. Williams Cassandra L. Crihfield Srikanth Gattu Lisa A. Holland Letha J. Sooter 《International journal of molecular sciences》2014,15(8):14332-14347
Widespread use of the chlorotriazine herbicide, atrazine, has led to serious environmental and human health consequences. Current methods of detecting atrazine contamination are neither rapid nor cost-effective. In this work, atrazine-specific single-stranded DNA (ssDNA) molecular recognition elements (MRE) were isolated. We utilized a stringent Systematic Evolution of Ligands by Exponential Enrichment (SELEX) methodology that placed the greatest emphasis on what the MRE should not bind to. After twelve rounds of SELEX, an atrazine-specific MRE with high affinity was obtained. The equilibrium dissociation constant (Kd) of the ssDNA sequence is 0.62 ± 0.21 nM. It also has significant selectivity for atrazine over atrazine metabolites and other pesticides found in environmentally similar locations and concentrations. Furthermore, we have detected environmentally relevant atrazine concentrations in river water using this MRE. The strong affinity and selectivity of the selected atrazine-specific ssDNA validated the stringent SELEX methodology and identified a MRE that will be useful for rapid atrazine detection in environmental samples. 相似文献
992.
Jia-Ying Xin Kai Lin Yan Wang Chun-Gu Xia 《International journal of molecular sciences》2014,15(12):21603-21620
Methanobactin (Mb) is a copper-binding peptide that appears to function as an agent for copper sequestration and uptake in methanotrophs. Mb can also bind and reduce Au(III) to Au(0). In this paper, Au/Al2O3 catalysts prepared by a novel incipient wetness-Mb-mediated bioreduction method were used for glucose oxidation. The catalysts were characterized, and the analysis revealed that very small gold nanoparticles with a particle size <4 nm were prepared by the incipient wetness-Mb-mediated bioreduction method, even at 1.0% Au loading (w/w). The influence of Au loading, calcination temperature and calcination time on the specific activity of Au/Al2O3 catalysts was systematically investigated. Experimental results showed that decomposing the Mb molecules properly by calcinations can enhance the specific activity of Au/Al2O3 catalysts, though they acted as reductant and protective agents during the catalyst preparation. Au/Al2O3 catalysts synthesized by the method exhibited optimum specific activity under operational synthesis conditions of Au loading of 1.0 wt % and calcined at 450 °C for 2 h. The catalysts were reused eight times, without a significant decrease in specific activity. To our knowledge, this is the first attempt at the preparation of Au/Al2O3 catalysts by Mb-mediated in situ synthesis of gold nanoparticles. 相似文献
993.
Da Xiao Xiao Liang Xiwu Gao Jianxiu Yao Kun Yan Zhu 《International journal of molecular sciences》2014,15(4):6880-6896
We identified and characterized the TcLgl gene putatively encoding lethal giant larvae (Lgl) protein from the red flour beetle (Tribolium castaneum). Analyses of developmental stage and tissue-specific expression patterns revealed that TcLgl was constitutively expressed. To examine the role of TcLgl in insect development, RNA interference was performed in early (1-day) larvae, late (20-day) larvae, and early (1-day) pupae. The early larvae injected with double-stranded RNA of TcLgl (dsTcLgl) at 100, 200, and 400 ng/larva failed to pupate, and 100% mortality was achieved within 20 days after the injection or before the pupation. The late larvae injected with dsTcLgl at these doses reduced the pupation rates to only 50.3%, 36.0%, and 18.2%, respectively. The un-pupated larvae gradually died after one week, and visually unaffected pupae failed to emerge into adults and died during the pupal stage. Similarly, when early pupae were injected with dsTcLgl at these doses, the normal eclosion rates were reduced to only 22.5%, 18.0%, and 11.2%, respectively, on day 7 after the injection, and all the adults with abnormal eclosion died in two days after the eclosion. These results indicate that TcLgl plays an essential role in insect development, especially during their metamorphosis. 相似文献
994.
Li Liu Hailun Gu Huimin Liu Yongliang Jiao Keyu Li Yue Zhao Li An Jun Yang 《International journal of molecular sciences》2014,15(4):6925-6940
Resveratrol is a natural polyphenolic compound that prevents inflammation in chondrocytes and animal models of osteoarthritis (OA) via yet to be defined mechanisms. The purpose of this study was to determine whether the protective effect of resveratrol on IL-1β-induced human articular chondrocytes was associated with the TLR4/MyD88/NF-κB signaling pathway by incubating human articular chondrocytes (harvested from osteoarthritis patients) with IL-1β before treatment with resveratrol. Cell viability was evaluated using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and TNFα levels in culture supernatants were measured by ELISA(Enzymelinked immunosorbent assay). The levels of TLR4 and its downstream signaling targets (MyD88 and TRAF6) and IL-1β were assessed by measuring the levels of mRNA and protein expression by real-time RT-PCR and western blot analysis, respectively, in addition to assessing NF-κB activation. In addition, TLR4 siRNA was used to block TLR4 expression in chondrocytes further demonstrating that resveratrol prevented IL-1β-mediated inflammation by TLR4 inhibition. We found that resveratrol prevented IL-1β-induced reduction in cell viability. Stimulation of chondrocytes with IL-1β caused a significant up-regulation of TLR4 and its downstream targets MyD88 and TRAF6 resulting in NF-κB activation associated with the synthesis of IL-1β and TNFα. These IL-1β-induced inflammatory responses were all effectively reversed by resveratrol. Furthermore, activation of NF-κB in chondrocytes treated with TLR4 siRNA was significantly attenuated, but not abolished, and exposure to resveratrol further reduced NF-κB translocation. These data suggested that resveratrol prevented IL-1β-induced inflammation in human articular chondrocytes at least in part by inhibiting the TLR4/MyD88/NF-κB signaling pathway suggesting that resveratrol has the potential to be used as a nutritional supplement to counteract OA symptoms. 相似文献
995.
Dongxia Ge Qing-Song Zhang Jovanny Zabaleta Qiuyang Zhang Sen Liu Brendan Reiser Bruce A. Bunnell Stephen E. Braun Michael J. O’Brien Felix H. Savoie Zongbing You 《International journal of molecular sciences》2014,15(4):6941-6960
Embryonic development of articular cartilage has not been well understood and the role of doublecortin (DCX) in determination of chondrocyte phenotype is unknown. Here, we use a DCX promoter-driven eGFP reporter mouse model to study the dynamic gene expression profiles in mouse embryonic handplates at E12.5 to E13.5 when the condensed mesenchymal cells differentiate into either endochondral chondrocytes or joint interzone cells. Illumina microarray analysis identified a variety of genes that were expressed differentially in the different regions of mouse handplate. The unique expression patterns of many genes were revealed. Cytl1 and 3110032G18RIK were highly expressed in the proximal region of E12.5 handplate and the carpal region of E13.5 handplate, whereas Olfr538, Kctd15, and Cited1 were highly expressed in the distal region of E12.5 and the metacarpal region of E13.5 handplates. There was an increasing gradient of Hrc expression in the proximal to distal direction in E13.5 handplate. Furthermore, when human DCX protein was expressed in human adipose stem cells, collagen II was decreased while aggrecan, matrilin 2, and GDF5 were increased during the 14-day pellet culture. These findings suggest that DCX may play a role in defining chondrocyte phenotype. 相似文献
996.
Shigeomi Shimizu Tatsushi Yoshida Masatsune Tsujioka Satoko Arakawa 《International journal of molecular sciences》2014,15(2):3145-3153
Programmed cell death (PCD) is a crucial process required for the normal development and physiology of metazoans. The three major mechanisms that induce PCD are called type I (apoptosis), type II (autophagic cell death), and type III (necrotic cell death). Dysfunctional PCD leads to diseases such as cancer and neurodegeneration. Although apoptosis is the most common form of PCD, recent studies have provided evidence that there are other forms of cell death. One of such cell death is autophagic cell death, which occurs via the activation of autophagy. The present review summarizes recent knowledge about autophagic cell death and discusses the relationship with tumorigenesis. 相似文献
997.
998.
Ming Li Kequan Guo Susumu Ikehara 《International journal of molecular sciences》2014,15(10):19226-19238
Alzheimer’s disease (AD) is a progressive and neurodegenerative disorder that induces dementia in older people. It was first reported in 1907 by Alois Alzheimer, who characterized the disease as causing memory loss and cognitive impairment. Pathologic characteristics of AD are β-amyloid plaques, neurofibrillary tangles and neurodegeneration. Current therapies only target the relief of symptoms using various drugs, and do not cure the disease. Recently, stem cell therapy has been shown to be a potential approach to various diseases, including neurodegenerative disorders, and in this review, we focus on stem cell therapies for AD. 相似文献
999.
Bao Zhang Yue-Hong Xu Shu-Guang Wei Hong-Bo Zhang Dong-Ke Fu Zu-Fei Feng Fang-Lin Guan Yong-Sheng Zhu Sheng-Bin Li 《International journal of molecular sciences》2014,15(11):19406-19416
Schizophrenia (SCZ) is a severe and debilitating mental disorder, and the specific genetic factors that underlie the risk for SCZ remain elusive. The autism susceptibility candidate 2 (AUTS2) gene has been reported to be associated with autism, suicide, alcohol consumption, and heroin dependence. We hypothesized that AUTS2 might be associated with SCZ. In the present study, three polymorphisms (rs6943555, rs7459368, and rs9886351) in the AUTS2 gene were genotyped in 410 patients with SCZ and 435 controls using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and forced PCR-RFLP methods. We detected an association between SCZ and the rs6943555 genotype distribution (odds ratio (OR) = 1.363, 95% confidence interval (CI): 0.848–2.191, p = 0.001). The association remained significant after adjusting for gender, and a significant effect (p = 0.001) was observed among the females. In the present study, rs6943555 was determined to be associated with female SCZ. Our results confirm previous reports which have suggested that rs6943555 might elucidate the pathogenesis of schizophrenia and play an important role in its etiology. 相似文献
1000.
Ruth Blanco-Rojo Laura Toxqui Ana M. López-Parra Carlos Baeza-Richer Ana M. Pérez-Granados Eduardo Arroyo-Pardo M. Pilar Vaquero 《International journal of molecular sciences》2014,15(3):4077-4087
The aim of this study was to investigate the combined influence of diet, menstruation and genetic factors on iron status in Spanish menstruating women (n = 142). Dietary intake was assessed by a 72-h detailed dietary report and menstrual blood loss by a questionnaire, to determine a Menstrual Blood Loss Coefficient (MBLC). Five selected SNPs were genotyped: rs3811647, rs1799852 (Tf gene); rs1375515 (CACNA2D3 gene); and rs1800562 and rs1799945 (HFE gene, mutations C282Y and H63D, respectively). Iron biomarkers were determined and cluster analysis was performed. Differences among clusters in dietary intake, menstrual blood loss parameters and genotype frequencies distribution were studied. A categorical regression was performed to identify factors associated with cluster belonging. Three clusters were identified: women with poor iron status close to developing iron deficiency anemia (Cluster 1, n = 26); women with mild iron deficiency (Cluster 2, n = 59) and women with normal iron status (Cluster 3, n = 57). Three independent factors, red meat consumption, MBLC and mutation C282Y, were included in the model that better explained cluster belonging (R2 = 0.142, p < 0.001). In conclusion, the combination of high red meat consumption, low menstrual blood loss and the HFE C282Y mutation may protect from iron deficiency in women of childbearing age. These findings could be useful to implement adequate strategies to prevent iron deficiency anemia. 相似文献