全文获取类型
收费全文 | 265320篇 |
免费 | 28402篇 |
国内免费 | 17897篇 |
专业分类
电工技术 | 22194篇 |
技术理论 | 7篇 |
综合类 | 23759篇 |
化学工业 | 38294篇 |
金属工艺 | 16947篇 |
机械仪表 | 17884篇 |
建筑科学 | 20882篇 |
矿业工程 | 9148篇 |
能源动力 | 7605篇 |
轻工业 | 24600篇 |
水利工程 | 7773篇 |
石油天然气 | 11648篇 |
武器工业 | 3277篇 |
无线电 | 28801篇 |
一般工业技术 | 26595篇 |
冶金工业 | 10362篇 |
原子能技术 | 3707篇 |
自动化技术 | 38136篇 |
出版年
2024年 | 1054篇 |
2023年 | 4181篇 |
2022年 | 9053篇 |
2021年 | 12066篇 |
2020年 | 8865篇 |
2019年 | 6781篇 |
2018年 | 7229篇 |
2017年 | 8218篇 |
2016年 | 7327篇 |
2015年 | 11095篇 |
2014年 | 13977篇 |
2013年 | 16313篇 |
2012年 | 20057篇 |
2011年 | 20981篇 |
2010年 | 19249篇 |
2009年 | 18739篇 |
2008年 | 18992篇 |
2007年 | 18507篇 |
2006年 | 17123篇 |
2005年 | 14168篇 |
2004年 | 10161篇 |
2003年 | 7532篇 |
2002年 | 7082篇 |
2001年 | 6407篇 |
2000年 | 5806篇 |
1999年 | 4186篇 |
1998年 | 2958篇 |
1997年 | 2450篇 |
1996年 | 2226篇 |
1995年 | 1946篇 |
1994年 | 1548篇 |
1993年 | 1147篇 |
1992年 | 944篇 |
1991年 | 722篇 |
1990年 | 575篇 |
1989年 | 521篇 |
1988年 | 404篇 |
1987年 | 275篇 |
1986年 | 196篇 |
1985年 | 105篇 |
1984年 | 77篇 |
1983年 | 57篇 |
1982年 | 72篇 |
1981年 | 49篇 |
1980年 | 68篇 |
1979年 | 43篇 |
1978年 | 3篇 |
1965年 | 3篇 |
1959年 | 32篇 |
1951年 | 49篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
131.
132.
133.
Simulating the psychological experience of human vision,a road extraction model based on the format tower is proposed to extract the road in the high resolution remote sensing image from the perspective of morphology.Firstly,based on the spectral and texture information,the suspected road targets are extracted by using segmentation technology.Then these targets are classified according to their reliability and extract the road targets for each category.Finally,three types of identified road information are verified and merged,and the continuous smooth road extraction results are obtained.Experiments on real high resolution images show that the results are consistent with the visual perception of the human eye,and the overall classification accuracy is higher,indicating that the algorithm is effective and feasible and has good use value. 相似文献
134.
文章简要介绍了煤矿工业场地的特点和低压配电系统接地方式分类,从安全性、经济性的角度分析了TN接地系统和TT接地系统在道路照明回路中的优缺点。通过对比TN-S系统与TT系统的接地故障电流差异、TN-S接地系统用于道路照明的等电位联结困难程度,总结出煤矿工业场地的道路照明配电系统适宜采用TT接地方式。并且详细阐述了TT接地系统剩余电流动作保护器保护整定方法和灵敏度校验方法,列举了煤矿工业场地道路照明选用TT系统时需要注意的中性线不可重复接地的问题。 相似文献
135.
以二茂铁甲醛和对甲苯磺酰基异氰(TOSMIC)为原料,经过Van Leusen反应,一步合成目标化合物5-二茂铁基噁唑,通过~1HNMR、~(13)CNMR和ESI-MS对其结构进行表征,并对影响收率的主要因素进行考察。结果表明,在物料比n(TOSMIC)∶n(二茂铁甲醛)为1.1∶1、反应溶剂为甲醇、K_2CO_3用量即n(K_2CO_3)∶n(二茂铁甲醛)为2.0∶1、反应温度为65℃、反应时间为8 h的最佳条件下,目标化合物收率达到74.7%。该方法具有原料廉价易得、反应操作简单、收率高等优点,具有一定的应用价值。 相似文献
136.
Dr. Hui Qiu Richard Caldwell Dr. Lesley Liu-Bujalski Dr. Andreas Goutopoulos Reinaldo Jones Justin Potnick Dr. Brian Sherer Dr. Andrew Bender Dr. Roland Grenningloh Dr. Daigen Xu Dr. Anna Gardberg Dr. Igor Mochalkin Dr. Theresa Johnson Dr. Ariele Viacava Follis Jared Head Dr. Federica Morandi 《ChemMedChem》2019,14(2):217-223
Bruton's tyrosine kinase (Btk) is an attractive target for the treatment of a wide array of B-cell malignancies and autoimmune diseases. Small-molecule covalent irreversible Btk inhibitors targeting Cys481 have been developed for the treatment of such diseases. In clinical trials, probe molecules are required in occupancy studies to measure the level of engagement of the protein by these covalent irreversible inhibitors. The result of this pharmacodynamic (PD) activity provides guidance for appropriate dosage selection to optimize inhibition of the drug target and correlation of target inhibition with disease treatment efficacy. This information is crucial for successful evaluation of drug candidates in clinical trials. Based on the pyridine carboxamide scaffold of a novel solvent-accessible pocket (SAP) series of covalent irreversible Btk inhibitors, we successfully developed a potent and selective affinity-based biotinylated probe 12 (2-[(4-{4-[5-(1-{5-[(3aS,4S,6aR)-2-oxo-hexahydro-1H-thieno[3,4-d]imidazol-4-yl]pentanamido}-3,6,9,12-tetraoxapentadecan-15-amido)pentanoyl]piperazine-1-carbonyl}phenyl)amino]-6-[1-(prop-2-enoyl)piperidin-4-yl]pyridine-3-carboxamide). Compound 12 has been used in Btk occupancy assays for preclinical studies to determine the therapeutic efficacy of Btk inhibition in two mouse lupus models driven by TLR7 activation and type I interferon. 相似文献
137.
WENXI GAO QIANQIAN MA CHENYU TANG YUELI ZHAN YINONG DUAN HUIHUA NI YUNZHAO XU 《Biocell》2020,44(4):597-605
Cervical cancer (CESC) is one of the most common cancers and affects the female genital tract. Consistent HPV
infection status has been determined to be a vital cause of tumorigenesis. HPV infection may induce changes to the
immune system and limit the host’s immune response. Immunotherapy is therefore essential to improving the overall
survival of both locally advanced and recurrent CESC patients. Using 304 relevant samples from TCGA, we assessed
immune cell function in CESC patients to better understand the status of both tumor micro-environment cells and
immune cells in CESC. Functional enrichment analysis, pathway enrichment analysis, and PPI network construction
were performed to explore the differentially expressed genes (DEGs). The analysis identified 425 DEGs, which
included 295 up-regulated genes and 130 down-regulated genes. We established that upregulation of CCL5 was
correlated with significantly better survival, meaning that CCL5 expression could serve as a novel prognostic
biomarker for CESC patients. We further focused on CCL5 as a hub gene in CESC, as it had significant correlations
with increased numbers of several types of immune cells. Cell-type fractions of M1 macrophages were significantly
higher in the high-immune-scores group, which was associated with better overall survival. Finally, we concluded that
CCL5 is a promising prognostic biomarker for CESC, as well as a novel chemotherapeutic target. 相似文献
138.
BDI模型能够很好地解决在特定环境下的Agent的推理和决策问题,但在动态和不确定环境下缺少决策和学习的能力。强化学习解决了Agent在未知环境下的决策问题,却缺少BDI模型中的规则描述和逻辑推理。针对BDI在未知和动态环境下的策略规划问题,提出基于强化学习Q-learning算法来实现BDI Agent学习和规划的方法,并针对BDI的实现模型ASL的决策机制做出了改进,最后在ASL的仿真平台Jason上建立了迷宫的仿真,仿真实验表明,在加入Q-learning学习机制后的新的ASL系统中,Agent在不确定环境下依然可以完成任务。 相似文献
139.
Xu Zhi-Zheng Jiang Feng Zhong Chong-Quan Gou Yong-Jie Teng Hong-Fei 《Structural and Multidisciplinary Optimization》2020,61(1):207-223
Structural and Multidisciplinary Optimization - The overall layout optimization design of an orbital propellant depot involves the optimization of shape, size, and positions of propellant tanks in... 相似文献
140.
The smoke suppression of rigid polyurethane foam (RPUF) modified by melamine was investigated based on three sections: the condensed phase, the carbon layer, and the gas phase. In the condensed phase, the results of thermogravimetry, X‐ray photoelectron spectroscopy (XPS) N1S spectrum, and Fourier transform infrared spectroscopy indicated that melamine could suppress the degradation of RPUF by reacting with the aromatic hydrocarbons. It also reduced the smoke generation because the volatilizable aromatic hydrocarbons were the principal smoke precursors in a fire. In the carbon layer, the decrease from 38.50% to 24.76% of the inner layer oxygen content identified by XPS full‐spectrum and C1S spectrum indicated that melamine could prevent oxygen from transferring into the inner foam by the formation of an enhanced surface carbon layer, and the enhanced carbon layer could also block the release of smoke precursors. In the gas phase, the content of total aromatic hydrocarbons declined to 59.12% according to pyrolysis gaseous chromatography mass spectroscopy and indicated that melamine could reduce the smoke precursors. The results of smoke density chamber and cone calorimeter tests revealed that the addition of the melamine could decrease the smoke density of burning RPUF. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献