全文获取类型
收费全文 | 125622篇 |
免费 | 11932篇 |
国内免费 | 8312篇 |
专业分类
电工技术 | 4952篇 |
技术理论 | 3篇 |
综合类 | 8793篇 |
化学工业 | 27879篇 |
金属工艺 | 9094篇 |
机械仪表 | 6867篇 |
建筑科学 | 7784篇 |
矿业工程 | 3809篇 |
能源动力 | 3773篇 |
轻工业 | 8884篇 |
水利工程 | 2384篇 |
石油天然气 | 5415篇 |
武器工业 | 1825篇 |
无线电 | 15544篇 |
一般工业技术 | 15609篇 |
冶金工业 | 5507篇 |
原子能技术 | 1659篇 |
自动化技术 | 16085篇 |
出版年
2024年 | 461篇 |
2023年 | 2127篇 |
2022年 | 3459篇 |
2021年 | 4201篇 |
2020年 | 3714篇 |
2019年 | 3335篇 |
2018年 | 3100篇 |
2017年 | 3898篇 |
2016年 | 4245篇 |
2015年 | 4242篇 |
2014年 | 6501篇 |
2013年 | 6777篇 |
2012年 | 8181篇 |
2011年 | 9734篇 |
2010年 | 7446篇 |
2009年 | 8071篇 |
2008年 | 7547篇 |
2007年 | 9130篇 |
2006年 | 8361篇 |
2005年 | 7121篇 |
2004年 | 5811篇 |
2003年 | 5045篇 |
2002年 | 4113篇 |
2001年 | 3308篇 |
2000年 | 2979篇 |
1999年 | 2381篇 |
1998年 | 1890篇 |
1997年 | 1512篇 |
1996年 | 1345篇 |
1995年 | 1091篇 |
1994年 | 996篇 |
1993年 | 770篇 |
1992年 | 634篇 |
1991年 | 511篇 |
1990年 | 388篇 |
1989年 | 311篇 |
1988年 | 225篇 |
1987年 | 166篇 |
1986年 | 166篇 |
1985年 | 102篇 |
1984年 | 71篇 |
1983年 | 59篇 |
1982年 | 68篇 |
1981年 | 38篇 |
1980年 | 57篇 |
1979年 | 36篇 |
1977年 | 20篇 |
1976年 | 20篇 |
1975年 | 13篇 |
1974年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
Jakub Drzmisek Daniel Stipl Denisa Petrackova Branislav Vecerek Ana Dienstbier 《International journal of molecular sciences》2021,22(2)
Bacterial pathogens sense specific cues associated with different host niches and integrate these signals to appropriately adjust the global gene expression. Bordetella pertussis is a Gram-negative, strictly human pathogen of the respiratory tract and the etiological agent of whooping cough (pertussis). Though B. pertussis does not cause invasive infections, previous results indicated that this reemerging pathogen responds to blood exposure. Here, omics RNA-seq and LC–MS/MS techniques were applied to determine the blood-responsive regulon of B. pertussis. These analyses revealed that direct contact with blood rewired global gene expression profiles in B. pertussis as the expression of almost 20% of all genes was significantly modulated. However, upon loss of contact with blood, the majority of blood-specific effects vanished, with the exception of several genes encoding the T3SS-secreted substrates. For the first time, the T3SS regulator BtrA was identified in culture supernatants of B. pertussis. Furthermore, proteomic analysis identified BP2259 protein as a novel secreted T3SS substrate, which is required for T3SS functionality. Collectively, presented data indicate that contact with blood represents an important cue for B. pertussis cells. 相似文献
43.
《Journal of the European Ceramic Society》2020,40(14):4792-4798
The multilayer ceramic composites (MLC) consist of two ceramic materials insoluble in each other and sequentially piled in a symmetric manner whereas they can be divided into two groups: multilayer composites with weak interfaces and composites with strong interfaces. The graphene added multilayer ceramic sandwich (GMCS) composite was developed. The multilayer stack of Si3N4 with 5 and 30 wt% graphene addition were stratified in sandwich structure. So formed multilayer stacks with 5 and 7 layers were sintered by hot issostatic pressing (HIP). The homogenity of graphene addition, the effect of layered structures and the position of layers with lower and higher graphene content on the final properties were studied. 相似文献
44.
为了开发β受体阻断剂新药(S)-噻吗洛尔半水合物,采用3-吗啉-4-氯-1,2,5-噻二唑为起始原料,经水解反应得到中间体1(3-吗啉-4-羟基-1,2,5-噻二唑)。中间体1与R-环氧氯丙烷发生醚化反应,经后处理及重结晶得到中间体2 {(R)-4-[4-(环氧乙烷-2-基甲氧基)-1,2,5-噻二唑-3-基]吗啉}。中间体2经胺化反应、马来酸成盐及重结晶得到(S)-马来酸噻吗洛尔。(S)-马来酸噻吗洛尔经游离、纯水转晶得到符合药典标准的(S)-噻吗洛尔半水合物,总收率14.05%且e.e.值为99.66%。最终成品经IR、1H-NMR、13C-NMR、MS、TGA、DSC表征,并优化各步反应条件。结果表明:以三乙胺为醚化反应缚酸剂75 ℃反应最佳;以乙醇为胺化反应溶剂46 ℃反应16 h最佳;S-噻吗洛尔的转晶拆分以水作溶剂,比传统不对称合成工艺安全稳定,操作简单,适合工业化生产。 相似文献
45.
Cheese fortification using saturated monoglyceride self‐assembly structures as carrier of omega‐3 fatty acids 下载免费PDF全文
Sonia Calligaris Alexandra Ignat Marialuisa Biasutti Nadia Innocente Maria Cristina Nicoli 《International Journal of Food Science & Technology》2015,50(9):2129-2134
The purpose of this research was to study the capacity of emulsions containing saturated monoglyceride self‐assembly structures to deliver omega‐3 fatty acids in fresh soft cheese. To this aim, fortified emulsions containing different ratios of milk, saturated monoglycerides (MGs) and cod liver oil were added to milk before cheese‐making. These emulsions were characterised by distinct microstructural features observed by polarised light microscopy and apparent viscosity values. The omega‐3 delivery performance of MG emulsions highlighted that this strategy allowed a good retention of the omega‐3‐rich oil in the curd (up to 75%). The fortified cheeses showed yield value and fat content higher than those of control samples. The enriched cheese showed hardness and cohesiveness obtained by texture profile analysis similar to those of the unfortified product. Only a slight decrease in gumminess was detected in fortified cheese. 相似文献
46.
M. R. Thompson 《Drug development and industrial pharmacy》2015,41(8):1223-1231
Twin screw granulation (TSG) is a new process of interest to the pharmaceutical community that can continuously wet granulate powders, doing so at lower liquid concentrations and with better product consistency than found by a high shear batch mixer. A considerable body of research has evolved over the short time since this process was introduced but generally with little comparison of results. A certain degree of confidence has been developed through these studies related to how process variables and many attributes of machinery configuration will affect granulation but some major challenges still lay ahead related to scalability, variations in the processing regimes related to degree of channel fill and the impact of wetting and granulation of complex powder formulations. This review examines the current literature for wet granulation processes studied in twin screw extrusion machinery, summarizing the influences of operational and system parameters affecting granule properties as well as strives to provide some practical observations to newly interested users of the technique. 相似文献
47.
Akira Yamamoto Kentaro Teramura Saburo Hosokawa Tsunehiro Tanaka 《Science and Technology of Advanced Materials》2015,16(2)
The effect of SO2 gas was investigated on the activity of the photo-assisted selective catalytic reduction of nitrogen monoxide (NO) with ammonia (NH3) over a TiO2 photocatalyst in the presence of excess oxygen (photo-SCR). The introduction of SO2 (300 ppm) greatly decreased the activity of the photo-SCR at 373 K. The increment of the reaction temperature enhanced the resistance to SO2 gas, and at 553 K the conversion of NO was stable for at least 300 min of the reaction. X-ray diffraction, FTIR spectroscopy, thermogravimetry and differential thermal analysis, x-ray photoelectron spectroscopy (XPS), elemental analysis and N2 adsorption measurement revealed that the ammonium sulfate species were generated after the reaction. There was a strong negative correlation between the deposition amount of the ammonium sulfate species and the specific surface area. Based on the above relationship, we concluded that the deposition of the ammonium sulfate species decreased the specific surface area by plugging the pore structure of the catalyst, and the decrease of the specific surface area resulted in the deactivation of the catalyst. 相似文献
48.
49.
王学鹏 《电子制作.电脑维护与应用》2015,(6)
CAN-BUS系统自问世以来,已将近30年,当代各品牌车辆纷纷采用,但大部分技术人员对CAN总线系统既熟悉又陌生。经常能听到,但具体操作又显得有些力不从心。本文通过对奇瑞A3品牌轿车CAN总线的巧妙应用,引导大家进一步理解和应用CAN总线。 相似文献
50.