全文获取类型
收费全文 | 65555篇 |
免费 | 8647篇 |
国内免费 | 6096篇 |
专业分类
电工技术 | 5128篇 |
技术理论 | 9篇 |
综合类 | 6996篇 |
化学工业 | 3399篇 |
金属工艺 | 840篇 |
机械仪表 | 3853篇 |
建筑科学 | 2643篇 |
矿业工程 | 1544篇 |
能源动力 | 815篇 |
轻工业 | 3404篇 |
水利工程 | 1384篇 |
石油天然气 | 2949篇 |
武器工业 | 801篇 |
无线电 | 9279篇 |
一般工业技术 | 3437篇 |
冶金工业 | 1326篇 |
原子能技术 | 817篇 |
自动化技术 | 31674篇 |
出版年
2024年 | 153篇 |
2023年 | 951篇 |
2022年 | 1879篇 |
2021年 | 2732篇 |
2020年 | 2509篇 |
2019年 | 1984篇 |
2018年 | 1811篇 |
2017年 | 2179篇 |
2016年 | 2468篇 |
2015年 | 2909篇 |
2014年 | 4497篇 |
2013年 | 4178篇 |
2012年 | 4875篇 |
2011年 | 5245篇 |
2010年 | 4045篇 |
2009年 | 4013篇 |
2008年 | 4496篇 |
2007年 | 5009篇 |
2006年 | 4217篇 |
2005年 | 3806篇 |
2004年 | 3229篇 |
2003年 | 2746篇 |
2002年 | 2069篇 |
2001年 | 1585篇 |
2000年 | 1318篇 |
1999年 | 955篇 |
1998年 | 725篇 |
1997年 | 614篇 |
1996年 | 509篇 |
1995年 | 499篇 |
1994年 | 386篇 |
1993年 | 274篇 |
1992年 | 204篇 |
1991年 | 209篇 |
1990年 | 151篇 |
1989年 | 123篇 |
1988年 | 91篇 |
1987年 | 81篇 |
1986年 | 65篇 |
1985年 | 91篇 |
1984年 | 61篇 |
1983年 | 71篇 |
1982年 | 62篇 |
1981年 | 37篇 |
1980年 | 24篇 |
1979年 | 34篇 |
1978年 | 13篇 |
1977年 | 20篇 |
1976年 | 13篇 |
1964年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
To benefit from recent advances in modeling and computational algorithms,as well as the availability of new covariance data,sensitivity and uncertainty analyses are needed to quantify the impact of uncertain sources on the design parameters of small prismatic high-temperature gas-cooled reactors(HTGRs).In particular,the contribution of nuclear data to the keff uncertainty is an important part of the uncertainty analysis of small-sized HTGR physical calculations.In this study,a small-sized HTGR designed by China Nuclear Power Engineering Co.,Ltd.was selected for keff uncertainty analysis during full lifetime burnup calculations.Models of the cold zero power(CZP)condition and full lifetime burnup process were constructed using the Reactor Monte Carlo Code RMC for neutron transport calculation,depletion calculation,and sensitivity and uncertainty analysis.For the sensitivity analysis,the Contribution-Linked eigenvalue sensitivity/Uncertainty estimation via Track length importance Characterization(CLUTCH)method was applied to obtain sensitive infor-mation,and the"sandwich"method was used to quantify the keff uncertainty.We also compared the keff uncertainties to other typical reactors.Our results show that 235U is the largest contributor to keff uncertainty for both the CZP and depletion conditions,while the contribution of 239Pu is not very significant because of the design of low discharge burnup.It is worth noting that the radioactive capture reaction of 28Si significantly contributes to the keff uncer-tainty owing to its specific fuel design.However,the keff uncertainty during the full lifetime depletion process was relatively stable,only increasing by 1.12%owing to the low discharge burnup design of small-sized HTGRs.These numerical results are beneficial for neutronics design and core parameters optimization in further uncertainty prop-agation and quantification study for small-sized HTGR. 相似文献
3.
4.
5.
6.
7.
Milena Jankovic Ivana Novakovic Dejan Nikolic Jasmina Mitrovic Maksic Slavko Brankovic Ivana Petronic Dragana Cirovic Sinisa Ducic Mirko Grajic Dragana Bogicevic 《International journal of molecular sciences》2021,22(9)
Diabetic neuropathy (DN), the most common chronic and progressive complication of diabetes mellitus (DM), strongly affects patients’ quality of life. DN could be present as peripheral, autonomous or, clinically also relevant, uremic neuropathy. The etiopathogenesis of DN is multifactorial, and genetic components play a role both in its occurrence and clinical course. A number of gene polymorphisms in candidate genes have been assessed as susceptibility factors for DN, and most of them are linked to mechanisms such as reactive oxygen species production, neurovascular impairments and modified protein glycosylation, as well as immunomodulation and inflammation. Different epigenomic mechanisms such as DNA methylation, histone modifications and non-coding RNA action have been studied in DN, which also underline the importance of “metabolic memory” in DN appearance and progression. In this review, we summarize most of the relevant data in the field of genetics and epigenomics of DN, hoping they will become significant for diagnosis, therapy and prevention of DN. 相似文献
8.
9.
Margarita A. Sazonova Vasily V. Sinyov Anastasia I. Ryzhkova Marina D. Sazonova Tatiana V. Kirichenko Victoria A. Khotina Zukhra B. Khasanova Natalya A. Doroschuk Vasily P. Karagodin Alexander N. Orekhov Igor A. Sobenin 《International journal of molecular sciences》2021,22(2)
Chronic stress is a combination of nonspecific adaptive reactions of the body to the influence of various adverse stress factors which disrupt its homeostasis, and it is also a corresponding state of the organism’s nervous system (or the body in general). We hypothesized that chronic stress may be one of the causes occurence of several molecular and cellular types of stress. We analyzed literary sources and considered most of these types of stress in our review article. We examined genes and mutations of nuclear and mitochondrial genomes and also molecular variants which lead to various types of stress. The end result of chronic stress can be metabolic disturbance in humans and animals, leading to accumulation of reactive oxygen species (ROS), oxidative stress, energy deficiency in cells (due to a decrease in ATP synthesis) and mitochondrial dysfunction. These changes can last for the lifetime and lead to severe pathologies, including neurodegenerative diseases and atherosclerosis. The analysis of literature allowed us to conclude that under the influence of chronic stress, metabolism in the human body can be disrupted, mutations of the mitochondrial and nuclear genome and dysfunction of cells and their compartments can occur. As a result of these processes, oxidative, genotoxic, and cellular stress can occur. Therefore, chronic stress can be one of the causes forthe occurrence and development of neurodegenerative diseases and atherosclerosis. In particular, chronic stress can play a large role in the occurrence and development of oxidative, genotoxic, and cellular types of stress. 相似文献
10.
Understanding the mechanisms leading to the rise and dissemination of antimicrobial resistance (AMR) is crucially important for the preservation of power of antimicrobials and controlling infectious diseases. Measures to monitor and detect AMR, however, have been significantly delayed and introduced much later after the beginning of industrial production and consumption of antimicrobials. However, monitoring and detection of AMR is largely focused on bacterial pathogens, thus missing multiple key events which take place before the emergence and spread of AMR among the pathogens. In this regard, careful analysis of AMR development towards recently introduced antimicrobials may serve as a valuable example for the better understanding of mechanisms driving AMR evolution. Here, the example of evolution of tet(X), which confers resistance to the next-generation tetracyclines, is summarised and discussed. Initial mechanisms of resistance to these antimicrobials among pathogens were mostly via chromosomal mutations leading to the overexpression of efflux pumps. High-level resistance was achieved only after the acquisition of flavin-dependent monooxygenase-encoding genes from the environmental microbiota. These genes confer resistance to all tetracyclines, including the next-generation tetracyclines, and thus were termed tet(X). ISCR2 and IS26, as well as a variety of conjugative and mobilizable plasmids of different incompatibility groups, played an essential role in the acquisition of tet(X) genes from natural reservoirs and in further dissemination among bacterial commensals and pathogens. This process, which took place within the last decade, demonstrates how rapidly AMR evolution may progress, taking away some drugs of last resort from our arsenal. 相似文献