全文获取类型
收费全文 | 63615篇 |
免费 | 8416篇 |
国内免费 | 2856篇 |
专业分类
电工技术 | 2848篇 |
综合类 | 3165篇 |
化学工业 | 13081篇 |
金属工艺 | 2511篇 |
机械仪表 | 2728篇 |
建筑科学 | 4539篇 |
矿业工程 | 1669篇 |
能源动力 | 1238篇 |
轻工业 | 6877篇 |
水利工程 | 1068篇 |
石油天然气 | 1640篇 |
武器工业 | 295篇 |
无线电 | 6365篇 |
一般工业技术 | 6437篇 |
冶金工业 | 2693篇 |
原子能技术 | 588篇 |
自动化技术 | 17145篇 |
出版年
2024年 | 140篇 |
2023年 | 1110篇 |
2022年 | 2272篇 |
2021年 | 3718篇 |
2020年 | 2118篇 |
2019年 | 2113篇 |
2018年 | 2315篇 |
2017年 | 2965篇 |
2016年 | 4127篇 |
2015年 | 4703篇 |
2014年 | 5043篇 |
2013年 | 5151篇 |
2012年 | 3861篇 |
2011年 | 3459篇 |
2010年 | 2689篇 |
2009年 | 2991篇 |
2008年 | 2894篇 |
2007年 | 3983篇 |
2006年 | 4052篇 |
2005年 | 3372篇 |
2004年 | 2279篇 |
2003年 | 2137篇 |
2002年 | 1491篇 |
2001年 | 891篇 |
2000年 | 674篇 |
1999年 | 585篇 |
1998年 | 430篇 |
1997年 | 389篇 |
1996年 | 355篇 |
1995年 | 288篇 |
1994年 | 284篇 |
1993年 | 201篇 |
1992年 | 183篇 |
1991年 | 152篇 |
1990年 | 161篇 |
1989年 | 132篇 |
1988年 | 106篇 |
1987年 | 86篇 |
1986年 | 81篇 |
1985年 | 95篇 |
1984年 | 121篇 |
1983年 | 72篇 |
1982年 | 72篇 |
1981年 | 68篇 |
1980年 | 68篇 |
1979年 | 32篇 |
1966年 | 27篇 |
1964年 | 34篇 |
1962年 | 64篇 |
1955年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Efficient electricity price forecasting plays a significant role in our society. In this paper, a novel influencer-defaulter mutation (IDM) mutation operator has been proposed. The IDM operator has been combined with six well-known optimization algorithms to create mutated optimization algorithms whose performance has been tested on twenty-four standard benchmark functions. Further, the artificial neural network is integrated with mutated optimization algorithms to solve the electricity price prediction problem. The policymakers can identify appropriate variables based on the predicted prices to help future market planning. The statistical results prove the efficacy of the IDM operator on the recent optimization algorithms. 相似文献
2.
益生菌可在肠道定植从而发挥抗炎或抗氧化活性,有利于宿主肠道健康。本实验研究了从新疆传统发酵乳制品中分离得到的8?株植物乳杆菌对大肠杆菌侵袭和过氧化氢刺激肠上皮细胞HT-29的保护作用。结果表明:在8?株植物乳杆菌中,植物乳杆菌35具有最高的黏附能力。植物乳杆菌35可通过取代、竞争、排阻的方式抑制大肠杆菌对HT-29细胞的黏附,抑制率分别为42.60%、59.17%、60.19%。植物乳杆菌35及其多糖可抑制大肠杆菌刺激HT-29细胞产生白细胞介素-8;同时保护HT-29细胞免受过氧化氢的损伤,增加超氧化物歧化酶、谷胱甘肽过氧化物酶活力水平并降低丙二醛含量。结论:植物乳杆菌35及其粗胞外多糖具有抑制大肠杆菌O157诱导的炎症性肠病的潜力。 相似文献
3.
目的:探讨姜黄素的主要肠道代谢物四氢姜黄素(tetrahydrocurcumin,THC)对血小板活化和聚集的影响及其可能的分子机制。方法:在体外实验中,用不同浓度的THC(0、0.5、1、10 μmol/L)提前与健康人纯化血小板共同孵育40 min,然后加入凝血酶激活血小板2 min,用流式细胞术测定血小板表面CD62P和CD63的表达量,用酶联免疫吸附法测定血小板释放血小板因子-4(platelet factor-4,PF4)和趋化因子配体-5(chemokine ligand 5,CCL5)水平,用血小板聚集仪检测血小板释放ATP水平和血小板最大聚集率,用Western blot蛋白免疫印迹法检测血小板磷酸肌醇-3-激酶(phosphoinositide 3-kinase,PI3K)和Akt蛋白的磷酸化水平。结果:与模型组(血小板悬液中加入0.05%二甲基亚砜)相比,THC能抑制凝血酶诱导的血小板表面CD62P和CD63的表达,抑制PF4、CCL5和ATP的释放,降低血小板最大聚集率,下调PI3K和Akt蛋白的磷酸化水平,且呈浓度依赖效应,其中10 μmol/L的浓度下作用效果显著(P<0.01、P<0.001)。PI3K的特异性激动剂740 Y-P可部分逆转THC对PF4和CCL5释放和血小板聚集的抑制作用(P<0.05、P<0.01)。结论:THC具有显著抑制血小板活化和聚集的作用,其机制可能是THC可下调PI3K/Akt介导的信号通路。 相似文献
4.
Gehad Abo-Lila Taha Sokkar Eman Seisa Emam Omar 《Microscopy research and technique》2022,85(2):667-684
In this article, an adaptive denoising method is suggested to accurate investigate the optical and structural features of polymeric fibers from noisy phase shifting microinterferograms. The mixed class of noise that may produce in the phase-shifting interferometric techniques is established. To our knowledge, this is an early study considered the mixing noises that may occur in microinterferograms. The suggested method utilized the convolution neural networks to detect the noise class and then denoising, it according to its class. Four convolution neural networks (Googlenet, VGG-19, Alexnet, and Alexnet–SVM) are refined to perform the automatic classification process for the noise class in the established data set. The network with the highest validation and testing accuracy of these networks is considered to apply the suggested method on realistic noisy microinterferograms for polymeric fibers, polypropylene and antimicrobial polyethylene terephthalate)/titanium dioxide, recoded using interference microscope. Also, the suggested method is applied on noisy microinterferograms include crazing and nanocomposite material. The demodulated phase maps and the three-dimensional birefringence profiles are calculated for tested fibers according to the suggested method. The obtained results are compared with the published data for these fibers and found to be in good agreements. 相似文献
5.
Farzaneh Khorasani Morteza Mohammadi Zanjireh Mahdi Bahaghighat Qin Xin 《计算机系统科学与工程》2022,40(3):1085-1098
With a sharp increase in the information volume, analyzing and retrieving this vast data volume is much more essential than ever. One of the main techniques that would be beneficial in this regard is called the Clustering method. Clustering aims to classify objects so that all objects within a cluster have similar features while other objects in different clusters are as distinct as possible. One of the most widely used clustering algorithms with the well and approved performance in different applications is the k-means algorithm. The main problem of the k-means algorithm is its performance which can be directly affected by the selection in the primary clusters. Lack of attention to this crucial issue has consequences such as creating empty clusters and decreasing the convergence time. Besides, the selection of appropriate initial seeds can reduce the cluster’s inconsistency. In this paper, we present a new method to determine the initial seeds of the k-mean algorithm to improve the accuracy and decrease the number of iterations of the algorithm. For this purpose, a new method is proposed considering the average distance between objects to determine the initial seeds. Our method attempts to provide a proper tradeoff between the accuracy and speed of the clustering algorithm. The experimental results showed that our proposed approach outperforms the Chithra with 1.7% and 2.1% in terms of clustering accuracy for Wine and Abalone detection data, respectively. Furthermore, achieved results indicate that comparing with the Reverse Nearest Neighbor (RNN) search approach, the proposed method has a higher convergence speed. 相似文献
6.
Cho-Yi Chen Masaoki Kawasumi Tien-Yun Lan Chi-Lam Poon Yi-Sian Lin Pin-Jou Wu Yao-Chung Chen Bing-Hong Chen Cheng-Hsien Wu Jeng-Fan Lo Rueyhung Roc Weng Yi-Chen Sun Kai-Feng Hung 《International journal of molecular sciences》2021,22(1)
Endoplasmic reticulum (ER) stress response is an adaptive program to cope with cellular stress that disturbs the function and homeostasis of ER, which commonly occurs during cancer progression to late stage. Late-stage cancers, mostly requiring chemotherapy, often develop treatment resistance. Chemoresistance has been linked to ER stress response; however, most of the evidence has come from studies that correlate the expression of stress markers with poor prognosis or demonstrate proapoptosis by the knockdown of stress-responsive genes. Since ER stress in cancers usually persists and is essentially not induced by genetic manipulations, we used low doses of ER stress inducers at levels that allowed cell adaptation to occur in order to investigate the effect of stress response on chemoresistance. We found that prolonged tolerable ER stress promotes mesenchymal–epithelial transition, slows cell-cycle progression, and delays the S-phase exit. Consequently, cisplatin-induced apoptosis was significantly decreased in stress-adapted cells, implying their acquisition of cisplatin resistance. Molecularly, we found that proliferating cell nuclear antigen (PCNA) ubiquitination and the expression of polymerase η, the main polymerase responsible for translesion synthesis across cisplatin-DNA damage, were up-regulated in ER stress-adaptive cells, and their enhanced cisplatin resistance was abrogated by the knockout of polymerase η. We also found that a fraction of p53 in stress-adapted cells was translocated to the nucleus, and that these cells exhibited a significant decline in the level of cisplatin-DNA damage. Consistently, we showed that the nuclear p53 coincided with strong positivity of glucose-related protein 78 (GRP78) on immunostaining of clinical biopsies, and the cisplatin-based chemotherapy was less effective for patients with high levels of ER stress. Taken together, this study uncovers that adaptation to ER stress enhances DNA repair and damage tolerance, with which stressed cells gain resistance to chemotherapeutics. 相似文献
7.
Tomasz Pdzinski Katarzyna Grzyb Konrad Skotnicki Piotr Filipiak Krzysztof Bobrowski Chryssostomos Chatgilialoglu Bronislaw Marciniak 《International journal of molecular sciences》2021,22(9)
Within the reactive oxygen species (ROS) generated by cellular metabolisms, hydroxyl radicals (HO•) play an important role, being the most aggressive towards biomolecules. The reactions of HO• with methionine residues (Met) in peptides and proteins have been intensively studied, but some fundamental aspects remain unsolved. In the present study we examined the biomimetic model made of Ac-Met-OMe, as the simplest model peptide backbone, and of HO• generated by ionizing radiation in aqueous solutions under anoxic conditions. We performed the identification and quantification of transient species by pulse radiolysis and of final products by LC-MS and high-resolution MS/MS after γ-radiolysis. By parallel photochemical experiments, using 3-carboxybenzophenone (CB) triplet with the model peptide, we compared the outcomes in terms of short-lived intermediates and stable product identification. The result is a detailed mechanistic scheme of Met oxidation by HO•, and by CB triplets allowed for assigning transient species to the pathways of products formation. 相似文献
8.
9.
10.