全文获取类型
收费全文 | 28127篇 |
免费 | 3438篇 |
国内免费 | 1087篇 |
专业分类
电工技术 | 238篇 |
技术理论 | 2篇 |
综合类 | 1281篇 |
化学工业 | 9395篇 |
金属工艺 | 963篇 |
机械仪表 | 360篇 |
建筑科学 | 1429篇 |
矿业工程 | 330篇 |
能源动力 | 697篇 |
轻工业 | 6382篇 |
水利工程 | 222篇 |
石油天然气 | 1626篇 |
武器工业 | 344篇 |
无线电 | 3293篇 |
一般工业技术 | 5015篇 |
冶金工业 | 548篇 |
原子能技术 | 163篇 |
自动化技术 | 364篇 |
出版年
2024年 | 205篇 |
2023年 | 791篇 |
2022年 | 810篇 |
2021年 | 1182篇 |
2020年 | 1202篇 |
2019年 | 1239篇 |
2018年 | 1099篇 |
2017年 | 1232篇 |
2016年 | 1265篇 |
2015年 | 1160篇 |
2014年 | 1753篇 |
2013年 | 1862篇 |
2012年 | 1884篇 |
2011年 | 2085篇 |
2010年 | 1458篇 |
2009年 | 1520篇 |
2008年 | 1311篇 |
2007年 | 1523篇 |
2006年 | 1460篇 |
2005年 | 1188篇 |
2004年 | 1013篇 |
2003年 | 982篇 |
2002年 | 790篇 |
2001年 | 628篇 |
2000年 | 539篇 |
1999年 | 383篇 |
1998年 | 354篇 |
1997年 | 288篇 |
1996年 | 222篇 |
1995年 | 203篇 |
1994年 | 177篇 |
1993年 | 124篇 |
1992年 | 108篇 |
1991年 | 101篇 |
1990年 | 78篇 |
1989年 | 54篇 |
1988年 | 27篇 |
1987年 | 45篇 |
1986年 | 28篇 |
1985年 | 53篇 |
1984年 | 53篇 |
1983年 | 34篇 |
1982年 | 48篇 |
1981年 | 7篇 |
1980年 | 24篇 |
1979年 | 9篇 |
1978年 | 9篇 |
1975年 | 8篇 |
1974年 | 6篇 |
1951年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Andrea Kunova Luca Palazzolo Fabio Forlani Giorgia Catinella Loana Musso Paolo Cortesi Ivano Eberini Andrea Pinto Sabrina Dallavalle 《International journal of molecular sciences》2021,22(7)
The increasing emergence of fungicide-resistant pathogens requires urgent solutions for crop disease management. Here, we describe a structural investigation of new fungicides obtained by combining strobilurin and succinate dehydrogenase inhibitor pharmacophores. We identified compounds endowed with very good activity against wild-type Pyricularia oryzae, combined in some cases with promising activity against strobilurin-resistant strains. The first three-dimensional model of P. oryzae cytochrome bc1 complex containing azoxystrobin as a ligand was developed. The model was validated with a set of commercially available strobilurins, and it well explains both the resistance mechanism to strobilurins mediated by the mutation G143A and the activity of metyltetraprole against strobilurin-resistant strains. The obtained results shed light on the key recognition determinants of strobilurin-like derivatives in the cytochrome bc1 active site and will guide the further rational design of new fungicides able to overcome resistance caused by G143A mutation in the rice blast pathogen. 相似文献
102.
103.
104.
Zhiwen Lei Qi Qiu Jinlai Shen Xiaohu Ao Bingqi Zhang Yuanfa Guo Jun Wang Yonghong Deng Chaoyang Wang 《大分子材料与工程》2021,306(10):2100336
Solid polymer electrolyte with good thermal stability and flexibility is an excellent candidate for solid-state lithium metal batteries, while its low ionic conductivity caused by high crystallinity limits its application at ambient temperature. Here a metal organic framework (zeolitic imidazolate framework-8, ZIF-8) composited comb-like methoxy poly(ethylene glycol) acrylate polymer electrolyte (MCPE) with high ionic conductivity (9.96 × 10−5 S cm−1 at 30 °C) is prepared by an in situ UV polymerization method. The as-prepared MCPE exhibits improved mechanical property due to the introduction of porous ZIF-8 nanofillers, which is beneficial to suppress the growth of lithium dendrites. Consequently, the LiFePO4||MCPE||Li cells show a high capacity of 116 mAh g−1 at 30 °C and 0.5 C, and maintain 89.4% of initial capacity after 150 cycles with the average Coulombic efficiency of 99.9%. These results demonstrate that the MCPE shows great potential in solid-state lithium metal batteries near room temperature. 相似文献
105.
Emad Karrar Isam A. Mohamed Ahmed Muhammad Faisal Manzoor Frederick Sarpong Wei Wei Xingguo Wang 《European Journal of Lipid Science and Technology》2021,123(3):2000104
Cucurbitaceae family seeds are mostly discarded as agro-industrial wastes. Gurum (Citrullus lanatus var. colocynthoide) is an underutilized wild cucurbit plant, closely related to desert watermelon, which is grown abundantly in some African countries. Gurum seeds can play a significant role in health and nutrition due to their high oil content. This review describes the nutritional composition of gurum seeds and their oil profile. Gurum seeds are a good source of oil (27–35.5%), fiber (26–31%), crude protein (15–18%), and carbohydrates (14–17%). Gurum seeds oil is extracted by supercritical CO2 (SFE), screw press, and solvent extraction techniques. The gurum seeds oil is composed of unsaturated fatty acids with a high proportion of linoleic acid (C18:2) and oleic acid (C18:1). Gurum seeds oil contains various bioactive compounds, such as tocopherols, phytosterols, and polyphenols. It is reported that solvent extraction gives a higher yield than the screw press and SFE, but the SFE is preferred due to safety issues. More studies are required for producing better quality gurum seeds oil by using novel extraction techniques that can increase oil yield. 相似文献
106.
简要介绍了日本围绕燃气轮机用关键超高温金属结构材料所展开的研究开发工作,包括Ni基超合金、耐热金属间化合物、Nb基超合金及其复合材料。Ni基超合金仍是当前燃气轮机用超高温结构的主要材料,但其使用温度的上升潜力已经不多,用新的超高温材料替代Ni基超合金是燃气轮机用材的发展趋势,金属材料中耐热金属间化合物和Nb基复合材料是今后关注的焦点。 相似文献
107.
Preparation and electrochemical performance of nanosized Co3O4 via hydrothermal method 总被引:1,自引:0,他引:1
The hydrotalcite-type cobalt compounds were prepared through oxidation of Co(OH)2 gel using NH4OH as precipitating agent and H2O2 as oxidant. These hydrotalcite-type cobalt compounds were transformed into Co3O4 through hydrothermal decomposition with nanostructural deformation. The precursor and product were characterized by Fourier-transform infrared(FT-IR) spectrum, X-ray diffractometry(XRD) and transmission electron microscopy(TEM). The electrochemical performances of as-prepared nanosized Co3O4 as anode materials in lithium-ion batteries were tested by charge-discharge test in the voltage range of 0-3.0 V. The influence of morphology of Co3O4 particle on the capacity and cycling performance was studied. The results show that the shape and size of the final product can be controlled by altering cobalt sources. The irregular cubic Co3O4 with the average particle size of about 10 nm shows the best electrochemical performance. After 10 charge-discharge cycles, the specific charge capacity retains 555 mA.h/g. 相似文献
108.
用攀枝花钛矿和云南钛矿冶炼钛渣工业试验研究 总被引:1,自引:0,他引:1
通过磁性测量和X-射线衍射研究了Gd2(Co,Al)17化合物的结构和磁晶各向异性。当x≤4时,样品具有菱方Th2znl7型结构,x=5时,具有六方CaCu5型结构。随着Al浓度增加,晶格常数和单胞体积单调增大,而居里温度和自发磁化强度近似线性地减小;在x≥l时,观察到Co亚点阵的磁晶各向异性变号,室温易磁化方向由易面转变为易轴,且易轴各向异性场和各向异性常数随Al原子浓度增加出现极大值;基于补偿温度(65K)下自由粉末颗粒的磁化曲线,导出了亚点阵间的分子场系数和Gd-co交换耦合常数,结果表明,Al原子对Gd-Co交换耦合作用的影响较小。根据Al原子在Co亚点阵4种晶位的择优占位,分析了磁晶各向异性的演变。 相似文献
109.
采用高能球磨法研磨出PZT-5纳米粉料,添加外购的纳米有机添加剂,按照传统的固相工艺法制备出了压电陶瓷材料,研究分析纳米粉料和纳米有机添加剂对压电陶瓷性能的影响。通过测试分析可以看出,纳米压电粉料与纳米有机添加剂的综合作用,降低了材料的烧结温度、相对介电常数εr,Qm值和以d31,提高了压电应变常数d333,从而压电电压常数g33、gh、dh成倍提高,这些对制作宽带、高灵敏度的换能器是很有好处的。 相似文献
110.