全文获取类型
收费全文 | 16938篇 |
免费 | 2936篇 |
国内免费 | 2165篇 |
专业分类
电工技术 | 1208篇 |
综合类 | 2222篇 |
化学工业 | 591篇 |
金属工艺 | 173篇 |
机械仪表 | 896篇 |
建筑科学 | 584篇 |
矿业工程 | 173篇 |
能源动力 | 207篇 |
轻工业 | 295篇 |
水利工程 | 323篇 |
石油天然气 | 288篇 |
武器工业 | 276篇 |
无线电 | 2567篇 |
一般工业技术 | 1922篇 |
冶金工业 | 413篇 |
原子能技术 | 94篇 |
自动化技术 | 9807篇 |
出版年
2024年 | 56篇 |
2023年 | 316篇 |
2022年 | 588篇 |
2021年 | 641篇 |
2020年 | 748篇 |
2019年 | 666篇 |
2018年 | 643篇 |
2017年 | 806篇 |
2016年 | 858篇 |
2015年 | 949篇 |
2014年 | 1185篇 |
2013年 | 1341篇 |
2012年 | 1361篇 |
2011年 | 1397篇 |
2010年 | 1063篇 |
2009年 | 1132篇 |
2008年 | 1214篇 |
2007年 | 1182篇 |
2006年 | 1007篇 |
2005年 | 821篇 |
2004年 | 669篇 |
2003年 | 533篇 |
2002年 | 464篇 |
2001年 | 395篇 |
2000年 | 349篇 |
1999年 | 230篇 |
1998年 | 183篇 |
1997年 | 169篇 |
1996年 | 128篇 |
1995年 | 158篇 |
1994年 | 112篇 |
1993年 | 91篇 |
1992年 | 88篇 |
1991年 | 72篇 |
1990年 | 69篇 |
1989年 | 68篇 |
1988年 | 55篇 |
1987年 | 25篇 |
1986年 | 28篇 |
1985年 | 25篇 |
1984年 | 14篇 |
1983年 | 18篇 |
1982年 | 27篇 |
1981年 | 17篇 |
1980年 | 17篇 |
1979年 | 6篇 |
1978年 | 9篇 |
1977年 | 9篇 |
1976年 | 8篇 |
1975年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 20 毫秒
1.
Corey Andrews Yiting Xu Michael Kirberger Jenny J. Yang 《International journal of molecular sciences》2021,22(1)
Calmodulin (CaM) is an important intracellular protein that binds Ca2+ and functions as a critical second messenger involved in numerous biological activities through extensive interactions with proteins and peptides. CaM’s ability to adapt to binding targets with different structures is related to the flexible central helix separating the N- and C-terminal lobes, which allows for conformational changes between extended and collapsed forms of the protein. CaM-binding targets are most often identified using prediction algorithms that utilize sequence and structural data to predict regions of peptides and proteins that can interact with CaM. In this review, we provide an overview of different CaM-binding proteins, the motifs through which they interact with CaM, and shared properties that make them good binding partners for CaM. Additionally, we discuss the historical and current methods for predicting CaM binding, and the similarities and differences between these methods and their relative success at prediction. As new CaM-binding proteins are identified and classified, we will gain a broader understanding of the biological processes regulated through changes in Ca2+ concentration through interactions with CaM. 相似文献
2.
《Journal of dairy science》2022,105(4):3176-3191
Milk concentrates are used in the manufacturing of dairy products such as yogurt and cheese or are processed into milk powder. Processes for the nonthermal separation of water and valuable milk ingredients are becoming increasingly widespread at farm level. The technical barriers to using farm-manufactured milk concentrate in dairies are minimal, hence the suspicion that the practice of on-farm raw milk concentration is still fairly uncommon for economic reasons. This study, therefore, set out to investigate farmers' potential willingness to adopt a raw milk concentration plant. The empirical analysis was based on discrete choice experiments with 75 German dairy farmers to identify preferences and the possible adoption of on-farm raw milk concentration. The results showed that, in particular, farmers who deemed the current milk price to be insufficient viewed on-farm concentration using membrane technology as an option for diversifying their milk sales. We found no indication that adoption would be impeded by a lack of trustworthy information on milk processing technologies or capital. 相似文献
3.
In process industry, predictive control approaches have been widely used for nonlinear production processes. Practically, the predictor in a predictive controller is extremely important since it provides future states for the optimization problem of controllers. The conventional predictive controller with precise mathematical predictors approximating the state space of physical systems is difficult and time-consuming for nonlinear production processes, and it performs poorly over a wide range of working conditions and with significant disturbances. To address the challenges, the trend of applying artificial intelligence emerges. However, the industrial process-specific knowledge is ignored in most cases. In this study, a predictive controller with a control process knowledge-based random forest (RF) model is proposed. Specifically, working data are clustered at first to handle diverse working conditions. Then, a process knowledge-based forest predictor, namely MIW-RF model with a redesigned cascading RF structure, is proposed to incorporate control process knowledge into modeling. Thus, future states of controlled variables could be more accurately acquired for the optimizer. A simplified version of the predictive model is also developed with quick model training and updating. The proposed predictive methods are finally introduced into the controller design. According to the empirical results, the proposed methods deliver a better control performance against benchmarks, including more accurate anticipated controlled-variable responses, better set-point tracking and disturbance rejection capability. 相似文献
4.
Diagnosing the cardiovascular disease is one of the biggest medical difficulties in recent years. Coronary cardiovascular (CHD) is a kind of heart and blood vascular disease. Predicting this sort of cardiac illness leads to more precise decisions for cardiac disorders. Implementing Grid Search Optimization (GSO) machine training models is therefore a useful way to forecast the sickness as soon as possible. The state-of-the-art work is the tuning of the hyperparameter together with the selection of the feature by utilizing the model search to minimize the false-negative rate. Three models with a cross-validation approach do the required task. Feature Selection based on the use of statistical and correlation matrices for multivariate analysis. For Random Search and Grid Search models, extensive comparison findings are produced utilizing retrieval, F1 score, and precision measurements. The models are evaluated using the metrics and kappa statistics that illustrate the three models’ comparability. The study effort focuses on optimizing function selection, tweaking hyperparameters to improve model accuracy and the prediction of heart disease by examining Framingham datasets using random forestry classification. Tuning the hyperparameter in the model of grid search thus decreases the erroneous rate achieves global optimization. 相似文献
5.
Fang Liu Pengfen Hou Hui Zhang Qingjuan Tang Changhu Xue Robert W. Li 《Comprehensive Reviews in Food Science and Food Safety》2021,20(4):3918-3936
Food additives, often used to guarantee the texture, shelf-life, taste, and appearance of processed foods, have gained widespread attention due to their increased link to the growing incidence of chronic diseases. As one of the most common additives, carrageenans have been used in human diets for hundreds of years. While classified as generally recognized as safe (GRAS) for human consumption, numerous studies since the 1980s have suggested that carrageenans, particularly those with random coil conformations, may have adverse effects on gastrointestinal health, including aggravating intestinal inflammation. While these studies have provided some evidence of adverse effects, the topic is still controversial. Some have suggested that the negative consequence of the consumption of carrageenans may be structure dependent. Furthermore, pre-existing conditions may predispose individuals to varied outcomes of carrageenan intake. In this review, structure–function relationships of various carrageenans in the context of food safety are discussed. We reviewed the molecular mechanisms by which carrageenans exert their biological effects. We summarized the findings associated with carrageenan intake in animal models and clinical trials. Moreover, we examined the interactions between carrageenans and the gut microbiome in the pathogenesis of gastrointestinal disorders. This review argues for personalized guidance on carrageenan intake based on individuals’ health status. Future research efforts that aim to close the knowledge gap on the effect of low-dose and chronic carrageenan intake as well as interactions among food additives should be conducive to the improved safety profile of carrageenans in processed food products. 相似文献
6.
共同购买网络的推荐系统应用越加广泛,仅基于网络内生结构变量研究其共同购买链接的经济意义已有局限,故加入网络口碑这一外生变量,进行更全面的分析。采用了社会网络方法中指数随机图模型进行建模,主要围绕产品销售量、产品入度、差评率和评论数4个方面因素,探究其对共同购买网络中共同购买链接形成的影响。结果显示,销售量、产品入度和评论数对共同购买链接形成的影响呈正比关系,而差评率则会显著地降低产品共同购买的几率。该指数随机图构建出的共同购买网络为在线电商平台管理网络口碑和推荐系统优化设计提供有益参考。 相似文献
7.
随着三网融合的大力推进以及双向互动业务的大力开展,运营商使用原有简单的EPG不足以支撑开展更多的增值业务,不能主动为用户推荐节目,不能为运营商带来新的收入机会。作为重要的创新能力支撑系统,介绍了江苏有线智能导航平台的设计与应用,为相关广电运营商提供一定的设计参考。 相似文献
8.
对于用户泛化和模糊的查询,将Web搜索引擎返回的列表内容聚类处理,便于用户有效查找感兴趣的内容。由于返回的列表由称为片段(snippet)的短文本组成,而传统的单词频率-逆文档频率(TF-IDF)特征选择模型不能适用于稀疏的短文本,使得聚类性能下降。一个有效的方法就是通过一个外部的知识库对短文本进行扩展。受到基于神经网络词表示方法的启发,提出了通过词嵌入技术的Word2Vec模型对短文本扩展,即采用Word2Vec模型的TopN个最相似的单词用于对片段(snippet)的扩展,扩展文档使得TF-IDF模型特征选择得到聚类性能的提高。同时考虑到通用性单词造成的噪声引入,对扩展文档的TF-IDF矩阵进行了词频权重修正。实验在两个公开数据集ODP239和SearchSnippets上完成,将所提方法和纯snippet无扩展的方法、基于Wordnet的特征扩展方法和基于Wikipedia的特征扩展方法进行了对比。实验结果表明,所提方法在聚类性能方面优于对比方法。 相似文献
9.
复杂网络最短路径经典算法的处理效率较低,不适用于大规模复杂网络,而现有近似算法通用性有限,且计算准确率不理想,不能满足规模日益扩大的复杂网络中的最短路径计算需求。针对于此,提出基于[k]-shell的复杂网络最短路径近似算法。算法利用节点的[k]-shell值进行网络划分并引导搜索路径,利用超点聚合处理[k]-shell子网来降低路径搜索中节点和连边的规模,通过在路径搜索过程使用双向搜索树方法提高算法的计算效率和准确率。实验结果表明,算法通用性较好,在现实与仿真大规模复杂网络中均具有较高的计算效率和准确率。 相似文献
10.
An improved cuckoo search algorithm for the problem of electric distribution network reconfiguration
Power loss reduction has an important role in operating electric distribution network system. There are a lot of methods for reduction power loss such as capacitor placement, distributed generation placement and electric distribution network reconfiguration (EDNR). Among these methods, the EDNR is an efficient technique to reduce power loss due to without taking any costs. However, the EDNR problem is a nonlinear, discrete problem and lots of extreme points. Therefore, it is necessary to have efficient methods for solving the EDNR problem. In this paper, an improved cuckoo search algorithm (ICSA) is proposed for solving the EDNR problem. In which, based on disadvantages of exploration and exploitation process of cuckoo search algorithm (CSA) for solving the EDNR problem, a local search mechanism is added to exploit candidate solutions existing around the current best solution. The calculated results on the simple distribution networks to complex distribution networks show that ICSA has ability for finding the global optimal solution with much smaller iterations and better quality of obtained solution compared with CSA and some other improved versions of CSA. The performance comparisons with other existing methods available in previous studies and the software of Power System Simulator/Advanced Distribution Engineering Productivity Tool (PSS/ADEPT) also lead to the better electric distribution network configuration with smaller total power losses. As a result, ICSA is a potential and reliable method for solving the EDNR problems. 相似文献