全文获取类型
收费全文 | 47718篇 |
免费 | 5642篇 |
国内免费 | 3212篇 |
专业分类
电工技术 | 4214篇 |
综合类 | 4531篇 |
化学工业 | 7767篇 |
金属工艺 | 1135篇 |
机械仪表 | 2176篇 |
建筑科学 | 2822篇 |
矿业工程 | 1024篇 |
能源动力 | 1407篇 |
轻工业 | 5108篇 |
水利工程 | 911篇 |
石油天然气 | 1709篇 |
武器工业 | 644篇 |
无线电 | 5382篇 |
一般工业技术 | 4267篇 |
冶金工业 | 1775篇 |
原子能技术 | 601篇 |
自动化技术 | 11099篇 |
出版年
2024年 | 260篇 |
2023年 | 635篇 |
2022年 | 1166篇 |
2021年 | 1352篇 |
2020年 | 1732篇 |
2019年 | 1621篇 |
2018年 | 1502篇 |
2017年 | 1978篇 |
2016年 | 2084篇 |
2015年 | 2110篇 |
2014年 | 2895篇 |
2013年 | 4305篇 |
2012年 | 3267篇 |
2011年 | 3412篇 |
2010年 | 2475篇 |
2009年 | 2605篇 |
2008年 | 2484篇 |
2007年 | 2959篇 |
2006年 | 2829篇 |
2005年 | 2320篇 |
2004年 | 1914篇 |
2003年 | 1770篇 |
2002年 | 1537篇 |
2001年 | 1370篇 |
2000年 | 1139篇 |
1999年 | 882篇 |
1998年 | 712篇 |
1997年 | 632篇 |
1996年 | 466篇 |
1995年 | 389篇 |
1994年 | 313篇 |
1993年 | 271篇 |
1992年 | 190篇 |
1991年 | 169篇 |
1990年 | 128篇 |
1989年 | 101篇 |
1988年 | 76篇 |
1987年 | 71篇 |
1986年 | 56篇 |
1985年 | 63篇 |
1984年 | 46篇 |
1983年 | 35篇 |
1982年 | 32篇 |
1981年 | 29篇 |
1980年 | 29篇 |
1979年 | 22篇 |
1978年 | 12篇 |
1977年 | 11篇 |
1964年 | 12篇 |
1956年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
VTI介质中弹性参数地震反演方法 总被引:2,自引:2,他引:0
根据地震波在具有垂直对称轴的横向各向同性(VTI)介质中的运动学特征,应用传播时间反演方法,进行了水平层状VTI介质的地层弹性参数反演方法研究。在VTI介质中,P-P波的传播时间曲线不再是双曲线,尤其在长排列情况下,已不能用二项泰勒展式精确地反演P-P波的传播时间,用三项泰勒展式则可以达到更高精度;P-SV波的传播时间也可用三项泰勒展式表达,在中等及短排列长度时可达到一定精神。对P-P波、P-SV波的传播时间进行三项泰勒展开时,它们的系数中包含了地震波的各向异性信息及垂直速度信息,中以为地震波的弹性参数反演提供提供基础,模试验分析及江苏油田某地区的二维多波资料实际反演结果表明,在最大炮间距为1.5倍地层埋深时,可以很精确地得到三项泰勒展式的系数,应用这些系数能精确反演地层弹性参数,包括P波、S波的垂直速度和各向异性参数。图4表1参5(杜丽英摘) 相似文献
82.
ABSTRACT: The effect of post-cooking holding-time on sensory assessment of low (89 g/kg) and high (218 g/kg) fat beefburgers was assessed. Burgers were served to panelists approximately 3 or 18 min after cooking. Fat content influenced fattiness, moistness/juiciness and overall appearance (P < 0.05), overall acceptability and overall texture (P< 0.01) and tenderness and crumbliness (p<0.001). Burgers with the higher fat content had higher scores. Holding-time influenced sensory overall appearance only with lower scores at extended holding times (P < 0.01). Treatment differences were small, mostly less than one sensory scale unit. Higher lightness and yellowness values were found for burgers with higher fat contents. 相似文献
83.
84.
液位定量式灌装机的灌装精度概率模型与可靠度计算模型 总被引:1,自引:0,他引:1
描述了控制液位定量式灌装机的灌装时间与灌装精度的关系,推导出实际灌装时间的理论计算公式。针对实际存在的各种随机变量对灌装时间的影响,建立了灌装时间的概率模型,提出基于灌装时间随机误差的灌状精度以及灌装精度可靠度概念,并相应建立出灌装精度概率模型与灌装精度可靠度计算模型。 相似文献
85.
《Drying Technology》2007,25(1):75-84
This article proposes a multiscale computational model able to calculate energy consumption in a batch lumber kiln. A dual-scale computational model of wood drying deals with the boards/stack interaction and serves as a basis for the present work. A new module was added here that calculates heat losses through kiln walls (convection, condensation) and the energy used by each kiln component (fans, heating elements, humidifier, vacuum pump, etc.). The corresponding mathematical formulation is presented and then theoretical results are compared to those collected in an industrial vacuum kiln. As application example, the effect of air reversal, air velocity, and kiln insulation are exhibited, which depicts the great potential and prospects of this new tool for energy savings in relation to the product quality. 相似文献
86.
《Drying Technology》2007,25(7):1237-1242
Rewarming of fruits and vegetables after cooling is characterized by heat and mass transfer processes, which leads commonly to condensation of water on the produce surface at temperatures below the dew point. This effect may affect the produce quality due to microbial growth at unfavorable environmental conditions. The amount of condensed water is a function of the produce surface temperature and of the surrounding conditions as air temperature, air humidity, and air flow. Under practical conditions, both the warming and the condensation are strongly affected by the packaging system used. Depending on the flow conditions close to the produce surface, parameters of heat and mass transfer under laboratory conditions were measured. A mathematical model was developed for the determination of the amount of condensed water on fruit surfaces, its reevaporation, and its total dwell time dependent on the environment air conditions. The model describes the heat and mass transfer processes on single fruits. The process of diffusion of humidity in air and proceed of surface temperature is the basis for the model. 相似文献
87.
《Drying Technology》2007,25(12):1959-1965
Drying is an important unit operation in processing of foods and other biotechnological products. Vacuum freeze drying is said to be the best drying technology regarding product quality of the end product, but the disadvantages are, among others, expensive operational costs and batch drying. Atmospheric freeze drying was introduced to lower the production costs of high-quality dried foods, and the need of simulation tools became important in estimations of the industrial drying processes.
A simplified mathematical model (AFDsim) is developed based on uniformly retreating ice front (URIF) considerations. The model is used to calculate theoretical drying curves of atmospheric freeze dried foods in a tunnel dryer. Studies of thermal and mass transfer properties during drying are essential for understanding the changes in product quality and for designing and dimensioning the drying process. The model can be used to simulate industrial atmospheric freeze drying of different foodstuff in a tunnel. The results from AFDsim modeling are in good accordance with the experimental results. 相似文献
A simplified mathematical model (AFDsim) is developed based on uniformly retreating ice front (URIF) considerations. The model is used to calculate theoretical drying curves of atmospheric freeze dried foods in a tunnel dryer. Studies of thermal and mass transfer properties during drying are essential for understanding the changes in product quality and for designing and dimensioning the drying process. The model can be used to simulate industrial atmospheric freeze drying of different foodstuff in a tunnel. The results from AFDsim modeling are in good accordance with the experimental results. 相似文献
88.
《Drying Technology》2007,25(7):1193-1201
This work describes how probiotic bacteria can be dried at low temperature in two steps, combining spray drying and vacuum drying, in order to enhance their survival during storage. A sufficient number of dried probiotics survived storage for more than 3 months at 30°C, if an appropriate combination of protein and carbohydrate was selected as carrier and storage conditions were maintained optimal. The use of soy protein and maltodextrin or skim milk and arabic gum resulted in the best survival rates of probiotics during storage. No evident difference was found between different spray dryer configurations, although a cocurrent flow was preferred. 相似文献
89.
Process Variables, Gelatinized Starch and Moisture Effects on Physical Properties of Mungbean Noodles 总被引:2,自引:0,他引:2
The effects of amounts of gelatinized starch and moisture in the final slurry or dough, cooking time, holding time, and holding temperature on physical properties of mungbean noodles were studied. Cooking loss, cutting stress, work to cut, and transparency of noodles were measured. Moisture content of the final slurry or dough, cooking time, and holding temperature were the most important factors that affected physical properties of mungbean noodles. Processing should be done at moisture contents not exceeding 55%, cooking times not longer than 40 set, and holding temperatures not lower than 3° using 5% of total starch as gelatinized starch and holding time of 36 hr. 相似文献
90.
本文重点介绍了方波依赖在音频测量,设备的维护检测及录音均衡自动调节等音频技术中的应用,并通过对方波信号的频谱特性和方波信号通过线性系统的频域特性的分析,简要说明了方波信号在应用电路中的基本工作原理。 相似文献