全文获取类型
收费全文 | 2134篇 |
免费 | 82篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 98篇 |
综合类 | 1篇 |
化学工业 | 557篇 |
金属工艺 | 81篇 |
机械仪表 | 39篇 |
建筑科学 | 43篇 |
能源动力 | 93篇 |
轻工业 | 158篇 |
水利工程 | 10篇 |
石油天然气 | 1篇 |
无线电 | 195篇 |
一般工业技术 | 422篇 |
冶金工业 | 238篇 |
原子能技术 | 74篇 |
自动化技术 | 208篇 |
出版年
2023年 | 8篇 |
2022年 | 7篇 |
2021年 | 54篇 |
2020年 | 19篇 |
2019年 | 27篇 |
2018年 | 48篇 |
2017年 | 27篇 |
2016年 | 46篇 |
2015年 | 47篇 |
2014年 | 63篇 |
2013年 | 156篇 |
2012年 | 84篇 |
2011年 | 135篇 |
2010年 | 97篇 |
2009年 | 128篇 |
2008年 | 89篇 |
2007年 | 98篇 |
2006年 | 88篇 |
2005年 | 74篇 |
2004年 | 63篇 |
2003年 | 74篇 |
2002年 | 53篇 |
2001年 | 49篇 |
2000年 | 32篇 |
1999年 | 47篇 |
1998年 | 103篇 |
1997年 | 54篇 |
1996年 | 50篇 |
1995年 | 42篇 |
1994年 | 35篇 |
1993年 | 38篇 |
1992年 | 20篇 |
1991年 | 24篇 |
1990年 | 19篇 |
1989年 | 29篇 |
1988年 | 21篇 |
1987年 | 29篇 |
1986年 | 12篇 |
1985年 | 13篇 |
1984年 | 19篇 |
1983年 | 12篇 |
1982年 | 15篇 |
1981年 | 10篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1978年 | 9篇 |
1977年 | 5篇 |
1976年 | 10篇 |
1974年 | 4篇 |
1973年 | 4篇 |
排序方式: 共有2218条查询结果,搜索用时 15 毫秒
1.
Vancha Harish Effi Haque Magdalena
miech Hiroaki Taniguchi Sarah Jamieson Devesh Tewari Anupam Bishayee 《International journal of molecular sciences》2021,22(9)
Xanthohumol (XH) is an important prenylated flavonoid that is found within the inflorescence of Humulus lupulus L. (Hop plant). XH is an important ingredient in beer and is considered a significant bioactive agent due to its diverse medicinal applications, which include anti-inflammatory, antimicrobial, antioxidant, immunomodulatory, antiviral, antifungal, antigenotoxic, antiangiogenic, and antimalarial effects as well as strong anticancer activity towards various types of cancer cells. XH acts as a wide ranging chemopreventive and anticancer agent, and its isomer, 8-prenylnaringenin, is a phytoestrogen with strong estrogenic activity. The present review focuses on the bioactivity of XH on various types of cancers and its pharmacokinetics. In this paper, we first highlight, in brief, the history and use of hops and then the chemistry and structure–activity relationship of XH. Lastly, we focus on its prominent effects and mechanisms of action on various cancers and its possible use in cancer prevention and treatment. Considering the limited number of available reviews on this subject, our goal is to provide a complete and detailed understanding of the anticancer effects of XH against different cancers. 相似文献
2.
3.
Taro Shimonosono Yoshihiro Hirata Mubin Changgan Syohei Kamei Rina Tokaiya Soichiro Sameshima Toshifumi Yoshidome Katsuhiko Yamaji 《Ceramics International》2018,44(8):8904-8912
This paper reports the performance of porous Gd-doped ceria (GDC) electrochemical cells with Co metal in both electrodes (cell No. 1) and with Ni metal in the cathode and Co metal in the anode (cell No. 2) for CO2 decomposition, CH4 decomposition, and the dry reforming reaction of a biogas with CO2 gas (CH4 + CO2 → 2H2 + 2CO) or with O2 gas in air (3CH4 +?1.875CO2 +?1.314O2 → 6H2 +?4.875CO +?0.7515O2). GDC cell No. 1 produced H2 gas at formation rates of 0.055 and 0.33?mL-H2/(min?m2-electrode) per 1?mL-supplied gas/(min?m2-electrode) at 600?°C and 800?°C, respectively, by the reforming of the biogas with CO2 gas. Similarly, cell No. 2 produced H2 gas at formation rates of 0.40?mL-H2/(min?m2) per 1?mL-supplied gas/(min?m2) at 800?°C from a mixture of biogas and CO2 gas. The dry reforming of a real biogas with CO2 or O2 gas at 800?°C proceeded thermodynamically over the Co or Ni metal catalyst in the cathode of the porous GDC cell. Faraday's law controlled the dry reforming rate of the biogas at 600?°C in cell No. 2. This paper also clarifies the influence of carbon deposition, which originates from CH4 pyrolysis (CH4 → C + 2H2) and disproportionation of CO gas (2CO → C + CO2), on the cell performance during dry reforming. The dry reforming of a biogas with O2 molecules from air exhibits high durability because of the oxidation of the deposited carbon by supplied air. 相似文献
4.
Eicosapentaenoic acid (EPA) production by an oleaginous fungus Mortierella alpina expressing heterologous the Δ17‐desaturase gene under ordinary temperature 下载免费PDF全文
5.
Hiroaki Matsumori Toshihisa Shimizu Koushi Takano Hitoshi Ishii 《Electrical Engineering in Japan》2015,190(2):57-71
In recent years, remarkable advancement of new power semiconductor devices, such as SiC and GaN, enables the increase of switching frequency of power converters, and hence the volume of passive components, such as ac filters and transformers, can be reduced. However, temperature rise caused by the inductor loss is increasing, and hence iron loss evaluation of the inductor is one of the most important issues to realize high power density converters. Conventionally, an improved generalized Steinmetz equation (iGSE) has proposed in order to calculate the iron loss under a pulse voltage magnetizing condition. However, accurate iron loss calculation of the ac filter inductor used in a PWM inverter cannot be realized. The authors have proposed two methods of iron loss evaluation of ac filter inductors. The first one is a loss map method which can calculate the iron loss without using a real PWM inverter. Another one is an ILA (Inductor Loss Analyzer) which can measure the iron loss in every switching period in a real PWM inverter. In this paper, comparisons of the iron loss between the ILA and the loss map method on both the single‐phase and three‐phase inverters are studied. It is found that iron loss of the ac filter inductor in the three‐phase PWM inverter which is calculated by the loss map method cause a large error on a specific condition. In order to prevent the calculation error, the authors proposed a revised loss map method and proved the effectiveness of the method. 相似文献
6.
Tomoshige Fujino Taishi Kondo Prof. Dr. Hiroaki Suga Prof. Dr. Hiroshi Murakami 《Chembiochem : a European journal of chemical biology》2019,20(15):1959-1965
Flexizymes are tRNA acylation ribozymes that have been successfully used to facilitate genetic code reprogramming. They are capable of charging acid substrates onto various tRNAs and tRNA analogues. However, their minimal RNA substrate has not been investigated. Here we have designed fluorescently labeled short RNAs corresponding to the four, three, and two bases (4bRNA, 3bRNA, 2bRNA) at the tRNA 3′-end and explored the minimal RNA substrate of flexizymes, dFx and eFx. 3bRNA was the observed minimal RNA substrate of the flexizymes, but the efficiency of acylation of this short RNA was two to three times lower than that of 4bRNA. The efficiency of acylation of 4bRNA was comparable with that of the microhelix, a 22-base RNA conventionally used as a tRNA analogue for analyzing acylation efficiency. We also compared the efficiencies of acylation of the microhelix and 4bRNA with various acid substrates. Thanks to the short length of 4bRNA, its acyl-4bRNA products exhibited larger mobility shifts in gel electrophoresis than those exhibited by acyl-microhelix products with every substrate tested. This indicated that 4bRNA was an ideal RNA substrate for analyzing the efficiency of acylation by flexizymes. 相似文献
7.
Circular data are those for which the natural support is the unit circle and its toroidal extensions. Numerous constructions have been proposed which can be used to generate models for such data. We propose a new, very general, one based on the normalization of the spectra of complex-valued stationary processes. As illustrations of the new construction's application, we study models for univariate circular data obtained from the spectra of autoregressive moving average models and relate them to existing models in the literature. We also propose and investigate multivariate circular models obtained from the high-order spectra of stationary stochastic processes generated using linear filtering with an autoregressive moving average response function. A new family of distributions for a Markov process on the circle is also introduced. Results for asymptotically optimal inference for dependent observations on the circle are presented which provide a new paradigm for inference with circular models. The application of one of the new families of spectra-generated models is illustrated in an analysis of wind direction data. 相似文献
8.
Trans‐fatty acid promotes thrombus formation in mice by aggravating antithrombogenic endothelial functions via Toll‐like receptors 下载免费PDF全文
Kensuke Kondo Tatsuro Ishida Tomoyuki Yasuda Hideto Nakajima Kenta Mori Nobuaki Tanaka Takeshige Mori Tomoko Monguchi Masakazu Shinohara Yasuhiro Irino Ryuji Toh Yoshiyuki Rikitake Kazunobu Kiyomizu Yoshiaki Tomiyama Junichiro Yamamoto Ken‐ichi Hirata 《Molecular nutrition & food research》2015,59(4):729-740
9.
Natsuko Goda Kana Shimizu Yohta Kuwahara Takeshi Tenno Tamotsu Noguchi Takahisa Ikegami Motonori Ota Hidekazu Hiroaki 《International journal of molecular sciences》2015,16(7):15743-15760
Intrinsically disordered proteins (IDPs) that lack stable conformations and are highly flexible have attracted the attention of biologists. Therefore, the development of a systematic method to identify polypeptide regions that are unstructured in solution is important. We have designed an “indirect/reflected” detection system for evaluating the physicochemical properties of IDPs using nuclear magnetic resonance (NMR). This approach employs a “chimeric membrane protein”-based method using the thermostable membrane protein PH0471. This protein contains two domains, a transmembrane helical region and a C-terminal OB (oligonucleotide/oligosaccharide binding)-fold domain (named NfeDC domain), connected by a flexible linker. NMR signals of the OB-fold domain of detergent-solubilized PH0471 are observed because of the flexibility of the linker region. In this study, the linker region was substituted with target IDPs. Fifty-three candidates were selected using the prediction tool POODLE and 35 expression vectors were constructed. Subsequently, we obtained 15N-labeled chimeric PH0471 proteins with 25 IDPs as linkers. The NMR spectra allowed us to classify IDPs into three categories: flexible, moderately flexible, and inflexible. The inflexible IDPs contain membrane-associating or aggregation-prone sequences. This is the first attempt to use an indirect/reflected NMR method to evaluate IDPs and can verify the predictions derived from our computational tools. 相似文献
10.