全文获取类型
收费全文 | 17379篇 |
免费 | 1839篇 |
国内免费 | 1369篇 |
专业分类
电工技术 | 1008篇 |
技术理论 | 1篇 |
综合类 | 2052篇 |
化学工业 | 2290篇 |
金属工艺 | 742篇 |
机械仪表 | 1054篇 |
建筑科学 | 2203篇 |
矿业工程 | 1042篇 |
能源动力 | 922篇 |
轻工业 | 790篇 |
水利工程 | 924篇 |
石油天然气 | 799篇 |
武器工业 | 187篇 |
无线电 | 1180篇 |
一般工业技术 | 3126篇 |
冶金工业 | 725篇 |
原子能技术 | 427篇 |
自动化技术 | 1115篇 |
出版年
2024年 | 35篇 |
2023年 | 165篇 |
2022年 | 330篇 |
2021年 | 397篇 |
2020年 | 522篇 |
2019年 | 436篇 |
2018年 | 457篇 |
2017年 | 524篇 |
2016年 | 668篇 |
2015年 | 616篇 |
2014年 | 902篇 |
2013年 | 1181篇 |
2012年 | 1212篇 |
2011年 | 1280篇 |
2010年 | 1008篇 |
2009年 | 1087篇 |
2008年 | 959篇 |
2007年 | 1132篇 |
2006年 | 1123篇 |
2005年 | 928篇 |
2004年 | 768篇 |
2003年 | 672篇 |
2002年 | 558篇 |
2001年 | 533篇 |
2000年 | 467篇 |
1999年 | 399篇 |
1998年 | 345篇 |
1997年 | 260篇 |
1996年 | 243篇 |
1995年 | 248篇 |
1994年 | 196篇 |
1993年 | 129篇 |
1992年 | 143篇 |
1991年 | 91篇 |
1990年 | 84篇 |
1989年 | 65篇 |
1988年 | 55篇 |
1987年 | 57篇 |
1986年 | 34篇 |
1985年 | 57篇 |
1984年 | 63篇 |
1983年 | 33篇 |
1982年 | 55篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1979年 | 11篇 |
1965年 | 3篇 |
1964年 | 3篇 |
1959年 | 17篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
Lucía Beltrn-Camacho Marta Rojas-Torres M
Carmen Durn-Ruiz 《International journal of molecular sciences》2021,22(5)
Critical limb ischemia (CLI) constitutes the most severe form of peripheral arterial disease (PAD), it is characterized by progressive blockade of arterial vessels, commonly correlated to atherosclerosis. Currently, revascularization strategies (bypass grafting, angioplasty) remain the first option for CLI patients, although less than 45% of them are eligible for surgical intervention mainly due to associated comorbidities. Moreover, patients usually require amputation in the short-term. Angiogenic cell therapy has arisen as a promising alternative for these “no-option” patients, with many studies demonstrating the potential of stem cells to enhance revascularization by promoting vessel formation and blood flow recovery in ischemic tissues. Herein, we provide an overview of studies focused on the use of angiogenic cell therapies in CLI in the last years, from approaches testing different cell types in animal/pre-clinical models of CLI, to the clinical trials currently under evaluation. Furthermore, recent alternatives related to stem cell therapies such as the use of secretomes, exosomes, or even microRNA, will be also described. 相似文献
2.
Ryszard Żywica Monika Modzelewska-Kapituła Katarzyna Tkacz 《International Journal of Food Properties》2018,21(1):1386-1394
The aim of the present study was to determine mathematical relationships between pH changes in beef 24 h post-slaughter and changes in the intensity of electrical current flowing through bull and heifer carcasses during high-voltage electrical stimulation. The electrical stimulation was applied 40 min postmortem for 120 s. The pH values of m. longissimus thoracis et lumborum were analyzed in the function of electrical current intensity changes and its change during electrical stimulation. Mathematical linear correlations of the y = ax ± b type were demonstrated between pH values at 2, 6, and 24 h postmortem and the initial (Ii) and ultimate (Iu) electrical current intensity values, the difference between them and the initial pH values determined before electrical stimulation. High multiple correlation coefficients (R2 = 0.416, α ≤ 0.001) between Iu and pH values 24 h post-slaughter enabled concluding that there is a possibility to predict a pH value of stimulated carcass with high accuracy, and thus also beef quality, based merely on the ultimate electrical current intensity values. 相似文献
3.
This work is devoted to the stress–strain state of isotropic double curved shell with defect system. The construction is weakened by two non-through thickness (internal) cracks of different length and by a circular hole located between cracks. In this study we use the line-spring model. Within the framework of this model cracks are modeled as mathematical cuts of shell’s middle surface. This leads to a two-dimensional problem. The problem is reduced to a system of eight boundary integral equations. To ensure the uniqueness of solution an additional equation is added. In the numerical solution of the problem special quadrature formulas for singular integrals of Cauchy type and the finite difference method are applied. The influence of defects on each other for double curved shell has been investigated. The given theoretical results can be used for the calculation of structural elements with holes, cracks on the strength and fracture toughness in various branches of engineering. 相似文献
4.
为了减小传统的最差情况设计方法引入的电压裕量,提出了一种变化可知的自适应电压缩减(AVS)技术,通过调整电源电压来降低电路功耗.自适应电压缩减技术基于检测关键路径的延时变化,基于此设计了一款预错误原位延时检测电路,可以检测关键路径延时并输出预错误信号,进而控制单元可根据反馈回的预错误信号的个数调整系统电压.本芯片采用SMIC180 nm工艺设计验证,仿真分析表明,采用自适应电压缩减技术后,4个目标验证电路分别节省功耗12.4%,11.3%,10.4%和11.6%. 相似文献
5.
High‐intensity sweeteners in espresso coffee: ideal and equivalent sweetness and time–intensity analysis
下载免费PDF全文
![点击此处可从《International Journal of Food Science & Technology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Bruna M. Azevedo Flávio L. Schmidt Helena M. A. Bolini 《International Journal of Food Science & Technology》2015,50(6):1374-1381
The efficient substitution of sucrose by a sweetener in beverages requires the application of some sensory techniques. First, one must determine the concentrations of the sweeteners under study, equivalent in sweetness to the ideal sucrose concentration. In addition, it is fundamental to determine which is most similar to sucrose. The objectives of this study were to determine the ideal sweetness for espresso coffee and the equivalent concentrations in sweetness of different sweeteners, as well as characterise the time–intensity profile of each sweetener in relation to sweetness. The sweeteners evaluated were sucralose, aspartame, neotame, a cyclamate/saccharin mixture (2:1) and stevia. The sucrose concentration considered ideal by consumers was 12.5% (w/v), and the equivalent concentrations of the sweeteners were 0.0159% for sucralose, 0.0549% for aspartame, 0.0016% for neotame, 0.0359% for the cyclamate/saccharin mixture and 0.0998% for stevia. The time–intensity analysis indicated that possibly the sweeteners neotame, aspartame and sucralose would be the best substitutes for sucrose. 相似文献
6.
热轧态中锰TRIP钢首先经650 ℃退火2 h,随后在550 ℃进行等温时效热处理,采用场发射扫描电镜(FE-SEM)研究该钢中P的偏聚和时效析出行为的变化情况。结果表明,中锰TRIP钢中P在晶界的偏聚是一种非平衡偏聚现象,临界时间约为50 h,与理论计算结果48 h较为吻合。在局部偏聚区域内,C与P存在共偏聚的关系,即P偏聚量高的地方,C含量也高。而合金元素Nb具有抑制P偏聚的效果,在20~70 h时效时间内,可以相对降低6.57%~19.5%的最大P偏聚量。根据电子背散射衍射(EBSD)菊池线分析,P偏聚量低于2.28at%时,P为固溶状态,高于2.28at.%时,P为析出状态。 相似文献
7.
Preference for saltiness is learned by oral exposure to salt taste; however, some data suggest a role for bodily sodium and potassium levels on salt taste preferences as well. The objective was to investigate whether encapsulated sodium and potassium supplementation lead to altered salt taste responses among adults with high blood pressure on a low sodium and low potassium diet. Twenty-six participants with untreated upper-range prehypertension or stage 1 hypertension were on a fully controlled low sodium and low potassium diet (both targeted at 2 g/day) for 13 weeks. Participants received capsules with sodium (3 g/d), potassium (3 g/d), or placebo, for 4 weeks each, in randomized order in a double blind crossover design. Sensory evaluation was done before and after each supplementation period and involved ratings of pleasantness and intensity in different salt (NaCl) concentrations in food and water, desire-to-eat salty food, and detection threshold for NaCl. Neither sodium supplementation nor potassium supplementation led to alterations in salt taste responses in food and water, and did not affect detection threshold (P = 0.59). There was no clear role for sodium or potassium supplementation on desire-to-eat salty food. In addition, we did not find effects of reduced oral exposure to salt over weeks, through the sodium-reduced diet, on salt taste preferences, in contrast to earlier studies. In conclusion, the results of this study suggest preference for saltiness is independent of changes in bodily sodium or potassium levels. 相似文献
8.
9.
10.
嵌入式RTOS中任务优先级反转问题研究 总被引:1,自引:0,他引:1
针对嵌入式实时系统任务调度策略的特点,任务在运行的时候可能被更高优先级的任务中断。分析了嵌入式RTOS中的最高就绪任务的查找算法,指出该调度算法存在的不同优先级的反转问题,并且针对这一问题进行研究,给出了相应的优先级继承方案。较好地解决了RTOS中任务调度中的优先级的反转问题。 相似文献