全文获取类型
收费全文 | 13635篇 |
免费 | 363篇 |
国内免费 | 518篇 |
专业分类
电工技术 | 310篇 |
综合类 | 30篇 |
化学工业 | 1611篇 |
金属工艺 | 1324篇 |
机械仪表 | 518篇 |
建筑科学 | 453篇 |
矿业工程 | 20篇 |
能源动力 | 555篇 |
轻工业 | 671篇 |
水利工程 | 99篇 |
石油天然气 | 152篇 |
武器工业 | 1篇 |
无线电 | 1850篇 |
一般工业技术 | 3913篇 |
冶金工业 | 1730篇 |
原子能技术 | 180篇 |
自动化技术 | 1099篇 |
出版年
2023年 | 51篇 |
2022年 | 98篇 |
2021年 | 191篇 |
2020年 | 124篇 |
2019年 | 161篇 |
2018年 | 274篇 |
2017年 | 257篇 |
2016年 | 322篇 |
2015年 | 241篇 |
2014年 | 344篇 |
2013年 | 935篇 |
2012年 | 575篇 |
2011年 | 825篇 |
2010年 | 622篇 |
2009年 | 843篇 |
2008年 | 742篇 |
2007年 | 750篇 |
2006年 | 690篇 |
2005年 | 520篇 |
2004年 | 561篇 |
2003年 | 424篇 |
2002年 | 400篇 |
2001年 | 424篇 |
2000年 | 401篇 |
1999年 | 384篇 |
1998年 | 696篇 |
1997年 | 486篇 |
1996年 | 431篇 |
1995年 | 296篇 |
1994年 | 232篇 |
1993年 | 182篇 |
1992年 | 141篇 |
1991年 | 146篇 |
1990年 | 113篇 |
1989年 | 97篇 |
1988年 | 75篇 |
1987年 | 51篇 |
1986年 | 54篇 |
1985年 | 40篇 |
1984年 | 45篇 |
1983年 | 37篇 |
1982年 | 27篇 |
1981年 | 18篇 |
1980年 | 20篇 |
1979年 | 18篇 |
1978年 | 20篇 |
1977年 | 18篇 |
1974年 | 13篇 |
1973年 | 10篇 |
1970年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Yuan-Cheng Meng Hua-Feng Zhang Xiao-Xiao Pan Nan Chen Hui-Fang Hu Saeed ul Haq Abid Khan Ru-Gang Chen 《International journal of molecular sciences》2021,22(6)
Dehydrins (DHNs) play an important role in abiotic stress tolerance in a large number of plants, but very little is known about the function of DHNs in pepper plants. Here, we isolated a Y1SK2-type DHN gene “CaDHN3” from pepper. To authenticate the function of CaDHN3 in salt and drought stresses, it was overexpressed in Arabidopsis and silenced in pepper through virus-induced gene silencing (VIGS). Sub-cellular localization showed that CaDHN3 was located in the nucleus and cell membrane. It was found that CaDHN3-overexpressed (OE) in Arabidopsis plants showed salt and drought tolerance phenotypic characteristics, i.e., increased the initial rooting length and germination rate, enhanced chlorophyll content, lowered the relative electrolyte leakage (REL) and malondialdehyde (MDA) content than the wild-type (WT) plants. Moreover, a substantial increase in the activities of antioxidant enzymes; including the superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), and lower hydrogen peroxide (H2O2) contents and higher O2•− contents in the transgenic Arabidopsis plants. Silencing of CaDHN3 in pepper decreased the salt- and drought-stress tolerance, through a higher REL and MDA content, and there was more accumulation of reactive oxygen species (ROS) in the CaDHN3-silenced pepper plants than the control plants. Based on the yeast two-hybrid (Y2H) screening and Bimolecular Fluorescence Complementation (BiFC) results, we found that CaDHN3 interacts with CaHIRD11 protein in the plasma membrane. Correspondingly, the expressions of four osmotic-related genes were significantly up-regulated in the CaDHN3-overexpressed lines. In brief, our results manifested that CaDHN3 may play an important role in regulating the relative osmotic stress responses in plants through the ROS signaling pathway. The results of this study will provide a basis for further analyses of the function of DHN genes in pepper. 相似文献
2.
3.
4.
5.
Dr. Jiayao Y. Wang Dr. Jiaqi Q. Li Prof. Dr. Yumei M. Xiao Prof. Dr. Bin Fu Prof. Dr. Zhaohai H. Qin 《ChemMedChem》2020,15(5):404-410
Mitochondrial oxidative damage and dysfunction contribute to a wide range of human diseases. Considering the limitation of conventional antioxidants and that mitochondria are the main source of reactive oxygen species (ROS) which induce oxidative damage, mitochondria-targeted antioxidants which can selectively block mitochondrial oxidative damage and prevent various types of cell death have been widely developed. As a lipophilic cation, triphenylphosphonium (TPP) has been commonly used in designing mitochondria-targeted antioxidants. Conjugated with the TPP moiety, antioxidants can achieve more than 1000-fold higher mitochondrial concentration depending on cell membrane potentials and mitochondrial membrane potentials. Herein we discuss the deficiencies of conventional antioxidants and the advantages of mitochondrial targeting, and review various types of TPP-based mitochondria-targeted antioxidants. These provide theoretical and background support for the design of new anti-oxidant. 相似文献
6.
7.
Slim Salhi Jihen Mahfoudh Souhir Abid Leonard‐Ionut Atanase Marcel Popa Christelle Delaite 《Polymer International》2020,69(11):1161-1168
A series of random polyesteramides (PEAs) with a range of molar composition from 90/10 to 50/50 were synthesized by direct melt polycondensation of ε‐caprolactone and l ‐alanine. Their structure was fully characterized by Fourier transform IR and NMR spectroscopy. The resulting copolymers are completely amorphous with the exception of PEA‐90/10 which possesses a semicrystalline structure. These PEAs present increasing glass transition temperatures at increasing l ‐alanine contents and exhibit fairly good thermal stability with 10% mass loss temperatures reaching 315 °C. © 2020 Society of Industrial Chemistry 相似文献
8.
A novel dual-rotation bobbin tool friction stir welding (DBT-FSW) was developed, in which the upper shoulder (US) and lower shoulder (LS) have different rotational speeds. This process was tried to weld 3.2 mm thick aluminum-lithium alloy sheets. The metallographic analysis and torque measurement were carried out to characterize the weld formability. Experimental results show that compared to conventional bobbin tool friction stir welding, the DBT-FSW has an excellent process stability, and can produce the defect-free joints in a wider range of welding parameters. These can be attributed to the significant improvement of material flow caused by the formation of a staggered layer structure and the unbalanced force between the US and LS during the DBT-FSW process. 相似文献
9.
A new constitutive equation of thermoelasticity for crystals is presented based on the interatomic potential and solid mechanics at finite temperature. Using the new constitutive equation, the calculations for crystal copper and graphene are carried out under different loading paths at different temperatures. The calculated results are in good agreement with those of the previous thermoelasticity constitutive equation based on quantum mechanics, which clearly indicates that our new constitutive equation of thermoelasticity is correct. A lot of comparisons also show that the present theory is more concise and efficient than the previous thermal stress theory in the practical application. 相似文献
10.
Alum sludge refers to the by-product from the processing of drinking water in water treatment works. In this study, groups of batch experiments were designed to identify the characteristics of dewatered alum sludge for phosphorus adsorption. Air-dried alum sludge (moisture content 10.2%), which was collected from a water treatment works in Dublin, was subjected to artificial P-rich wastewater adsorption tests using KH2PO4 as a model P source. Adsorption behaviours were investigated as a function of amount and particle size of alum sludge, pH of solution and adsorption time. The results have shown that pH plays a major role not only in the adsorption process but also in the adsorption capacity. With regard to adsorption capacity, this study reveals the Langmuir adsorption isotherm being the best fit with experimental data (R2 = 0.98-0.99). The maximum adsorption capacities range from 0.7 to 3.5 mg-P/g when the pH of the synthetic P solution was varied from 9.0 to 4.3, accordingly. The outcome of this study indicated that alum sludge is suitable for use as an adsorbent for removal of phosphate from wastewater. 相似文献