全文获取类型
收费全文 | 32214篇 |
免费 | 4152篇 |
国内免费 | 2266篇 |
专业分类
电工技术 | 793篇 |
综合类 | 2179篇 |
化学工业 | 6984篇 |
金属工艺 | 531篇 |
机械仪表 | 1103篇 |
建筑科学 | 398篇 |
矿业工程 | 1254篇 |
能源动力 | 341篇 |
轻工业 | 11255篇 |
水利工程 | 149篇 |
石油天然气 | 877篇 |
武器工业 | 163篇 |
无线电 | 2244篇 |
一般工业技术 | 1138篇 |
冶金工业 | 1326篇 |
原子能技术 | 469篇 |
自动化技术 | 7428篇 |
出版年
2024年 | 246篇 |
2023年 | 610篇 |
2022年 | 1021篇 |
2021年 | 1268篇 |
2020年 | 1448篇 |
2019年 | 1187篇 |
2018年 | 1171篇 |
2017年 | 1303篇 |
2016年 | 1407篇 |
2015年 | 1574篇 |
2014年 | 2024篇 |
2013年 | 2450篇 |
2012年 | 3232篇 |
2011年 | 2844篇 |
2010年 | 1963篇 |
2009年 | 1821篇 |
2008年 | 1714篇 |
2007年 | 2110篇 |
2006年 | 1819篇 |
2005年 | 1384篇 |
2004年 | 1062篇 |
2003年 | 923篇 |
2002年 | 688篇 |
2001年 | 550篇 |
2000年 | 493篇 |
1999年 | 403篇 |
1998年 | 326篇 |
1997年 | 301篇 |
1996年 | 226篇 |
1995年 | 189篇 |
1994年 | 135篇 |
1993年 | 117篇 |
1992年 | 125篇 |
1991年 | 84篇 |
1990年 | 80篇 |
1989年 | 59篇 |
1988年 | 40篇 |
1987年 | 42篇 |
1986年 | 34篇 |
1985年 | 31篇 |
1984年 | 29篇 |
1983年 | 21篇 |
1982年 | 14篇 |
1981年 | 13篇 |
1980年 | 13篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1959年 | 6篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
ABSTRACTThis paper proposes the multiple-hypotheses image segmentation and feed-forward neural network classifier for food recognition to improve the performance. Initially, the food or meal image is given as input. Then, the segmentation is applied to identify the regions, where a particular food item is located using salient region detection, multi-scale segmentation, and fast rejection. Then, the features of every food item are extracted by the global feature and local feature extraction. After the features are obtained, the classification is performed for each segmented region using a feed-forward neural network model. Finally, the calorie value is computed with the aid of (i) food volume and (ii) calorie and nutrition measure based on mass value. The experimental results and performance evaluation are validated. The outcome of the proposed method attains 0.947 for Macro Average Accuracy (MAA) and 0.959 for Standard Accuracy (SA), which provides better classification performance. 相似文献
2.
通过认真学习《细节决定成败》,结合井矿盐开采的实际,分别以生产过程中的三个细节为主,讨论了在采输卤生产技术控制中的细节的重要性。 相似文献
3.
In this paper, we describe a method for increasing the external efficiency of polymer light‐emitting diodes (LEDs) by coupling out waveguided light with Bragg gratings. We numerically model the waveguide modes in a typical LED structure and demonstrate how optimizing layer thicknesses and reducing waveguide absorption can enhance the grating outcoupling. The gratings were created by a soft‐lithography technique that minimizes changes to the conventional LED structure. Using one‐dimensional and two‐dimensional gratings, we were able to increase the forward‐directed emission by 47 % and 70 %, respectively, and the external quantum efficiency by 15 % and 25 %. 相似文献
4.
本文提出了一种基于信息融合的物体三维特征的提取方法,该方法利用两幅互相配准的三维测距图像和灰度图像,来提取多面体的三维特征。首先,通过分析灰度图像中的灰度变化及测距图像中的测距值变化,分别求取各自图像中物体的特征点及特征边;然后,利用两配准图像之间的对应关系,求得所有特征点、面与多边形在三维测距图像中的三维表示;接着,通过分析三维测距图像中所测得的各候选平面上特定点与边处的曲率及法向,验证候选平面 相似文献
5.
本文对芝麻营养保健成分的提取进行了系统的研究。确定了芝麻营养原液的制取工艺。为充分发挥芝麻的营养保健作用开辟了新的途径。 相似文献
6.
本文研究了HPMBP与伯胺N_(1923)的二甲苯溶液,从盐酸介质中协同萃取希土(Ⅲ)的机理。用斜率法、恒摩尔法确定了协萃配合物的组成为:RNH_3Ln(PMBP)_4。求得关于Pr(Ⅲ)协萃反应的平衡常数及协萃配合物的生成常数分别为:logK_(12)=-1.95;logβ_(12)=3.94。实验发现,协萃系数(R)随希土元素的原子序数(Z)递变而呈现“双峰效应”。还研究了协萃配合物的IR,NMR谱。 相似文献
7.
Protein Extraction from Heat-stabilized Defatted Rice Bran: II. The Role of Amylase, Celluclast, and Viscozyme 总被引:1,自引:0,他引:1
ABSTRACT: The effectiveness of 3 carbohydrases for protein extraction from heat-stabilized defatted rice bran (HDRB) was evaluated. Amylase, viscozyme and celluclast extracted a maximum of 45.4, 12.1, and 28.5% protein, respectively. Further study showed that extracted protein ranged from 9.5 to 58.4% under conditions of water to bran ratio (5:1 to 20:1), α-amylase (0 to 110000 units/10 g rice bran), temperature (35 to 55 °C), and time (1 to 8 h). The maximum protein extracted was 58.4% with a water to bran ratio of 17:1, 87637 units amylase, and 50.9 °C. These results suggest that impure food-grade amylase containing protease is more effective than celluclast and viscozyme in protein extraction from HDRB. 相似文献
8.
9.
10.
Tadashi Hano Michiaki Matsumoto Takahisa Kawazu Takaaki Ohtake 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,62(1):60-63
The extraction equilibria of various di- and tripeptides with di-2-ethylhexylphosphoric acid (D2EHPA) were studied at low pH values. The complex extracted to organic phase consisted of one molecule of peptide and two molecules of D2EHPA dimer. The extraction constants of the peptides correlated well with the distribution coefficients of peptides between 1-octanol and water, which is a measure of hydrophobicity. The permeation rates of peptides through an emulsion liquid membrane were examined by using D2EHPA as a carrier, Span 80 as an emulsifier and kerosene as a diluent. The rates varied considerably with peptide type, depending upon the hydrophobicity. 相似文献