全文获取类型
收费全文 | 103035篇 |
免费 | 1387篇 |
国内免费 | 1214篇 |
专业分类
电工技术 | 1938篇 |
综合类 | 139篇 |
化学工业 | 10533篇 |
金属工艺 | 5458篇 |
机械仪表 | 3187篇 |
建筑科学 | 2039篇 |
矿业工程 | 162篇 |
能源动力 | 2964篇 |
轻工业 | 6080篇 |
水利工程 | 711篇 |
石油天然气 | 668篇 |
武器工业 | 19篇 |
无线电 | 15978篇 |
一般工业技术 | 21777篇 |
冶金工业 | 25246篇 |
原子能技术 | 1386篇 |
自动化技术 | 7351篇 |
出版年
2022年 | 459篇 |
2021年 | 726篇 |
2020年 | 555篇 |
2019年 | 676篇 |
2018年 | 1129篇 |
2017年 | 1093篇 |
2016年 | 1174篇 |
2015年 | 925篇 |
2014年 | 1490篇 |
2013年 | 4668篇 |
2012年 | 2569篇 |
2011年 | 3840篇 |
2010年 | 3097篇 |
2009年 | 3722篇 |
2008年 | 3894篇 |
2007年 | 4081篇 |
2006年 | 3690篇 |
2005年 | 3328篇 |
2004年 | 3180篇 |
2003年 | 3028篇 |
2002年 | 2673篇 |
2001年 | 2969篇 |
2000年 | 2719篇 |
1999年 | 3078篇 |
1998年 | 9439篇 |
1997年 | 6154篇 |
1996年 | 4762篇 |
1995年 | 3163篇 |
1994年 | 2787篇 |
1993年 | 2723篇 |
1992年 | 1628篇 |
1991年 | 1593篇 |
1990年 | 1518篇 |
1989年 | 1322篇 |
1988年 | 1171篇 |
1987年 | 861篇 |
1986年 | 887篇 |
1985年 | 916篇 |
1984年 | 803篇 |
1983年 | 698篇 |
1982年 | 699篇 |
1981年 | 681篇 |
1980年 | 568篇 |
1979年 | 476篇 |
1978年 | 414篇 |
1977年 | 533篇 |
1976年 | 958篇 |
1975年 | 299篇 |
1974年 | 276篇 |
1973年 | 256篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Levon S. Atabekyan Alexandra Y. Freidzon Dmitry S. Ionov Vyacheslav N. Nuriev Alexey V. Medvedko Sergey Z. Vatsadze Sergey P. Gromov Alexander K. Chibisov 《International journal of molecular sciences》2022,23(23)
Photoprocesses in 1,4-diazadistyrylbenzene (1) and 1,3-diazadistyrylbenzene derivative (2) diperchlorates in MeCN were studied by absorption, luminescence, and kinetic laser spectroscopies. For compound 1, trans-cis-photoisomerization and intersystem crossing to a triplet state are observed. For compound 2, photoelectrocyclization is suggested. Quantum chemical calculations of diazadistyrylbenzene structures in the ground and excited states were carried out. The schemes for photoreactions were proposed. 相似文献
22.
Rumana Yasmeen Quynhchi Pham Naomi K. Fukagawa Thomas T. Y. Wang 《International journal of molecular sciences》2022,23(20)
Adipose stem cells (ASCs) are reported to play a role in normal physiology as well as in inflammation and disease. The objective of this work was to elucidate inter-individual differences in growth, gene expression and response to inflammatory stimuli in ASCs from different donors. Human ASC1 (male donor) and ASC2 (female donor) were purchased from Lonza (Walkersville, MD). Cell proliferation was determined by the sulforhodamine B assay. After time-dependent treatment of ASCs with or without bacterial lipopolysaccharide (LPS), marker gene mRNAs for proliferation, steroid hormones, and xenobiotic and immune pathways were determined using RT-PCR, and secreted cytokine levels in media were measured using the Bio-Plex cytokine assay kit. ASCs from both donors expressed androgen receptors but not estrogen receptors. ASC2 had a 2-fold higher proliferation rate and a 6-fold higher level of proliferation marker Ki67 mRNA than ASC1. ASC2 exhibited significantly greater fold induction of TNF-α and CCL2 by LPS compared to ASC1. TNF-α and GM-CSF protein levels were also significantly higher in the LPS-induced ASC2 media, but IL-6 secretion was higher in the LPS-induced ASC1 media. Our findings suggest that inter-individual variability and/or possible sex differences exist in ASCs, which may serve as a key determinant to inflammatory responses of ASCs. 相似文献
23.
24.
Chiara Fischer Andrey Turchinovich Manuel Feisst Fabian Riedel Kathrin Haßdenteufel Philipp Scharli Andreas D. Hartkopf Sara Y. Brucker Laura Michel Barbara Burwinkel Andreas Schneeweiss Markus Wallwiener Thomas M. Deutsch 《International journal of molecular sciences》2022,23(17)
The extracellular circulating microRNA (miR)-200 regulates epithelial-mesenchymal transition and, thus, plays an essential role in the metastatic cascade and has shown itself to be a promising prognostic and predictive biomarker in metastatic breast cancer (MBC). Expression levels of the plasma miR-200 family were analyzed in relationship to systemic treatment, circulating tumor cells (CTC) count, progression-free survival (PFS), and overall survival (OS). Expression of miR-200a, miR-200b, miR-200c, miR-141, and miR-429, and CTC status (CTC-positive ≥ 5 CTC/7.5 mL) was assessed in 47 patients at baseline (BL), after the first completed cycle of a new line of systemic therapy (1C), and upon the progression of disease (PD). MiR-200a, miR-200b, and miR-141 expression was reduced at 1C compared to BL. Upon PD, all miR-200s were upregulated compared to 1C. At all timepoints, the levels of miR-200s were elevated in CTC-positive versus CTC-negative patients. Further, heightened miR-200s expression and positive CTC status were associated with poorer OS at BL and 1C. In MBC patients, circulating miR-200 family members decreased after one cycle of a new line of systemic therapy, were elevated during PD, and were indicative of CTC status. Notably, increased levels of miR-200s and elevated CTC count correlated with poorer OS and PFS. As such, both are promising biomarkers for optimizing the clinical management of MBC. 相似文献
25.
Veronica Barcelona Yunfeng Huang Billy A. Caceres Kevin P. Newhall Qin Hui Jessica P. Cerdea Cindy A. Crusto Yan V. Sun Jacquelyn Y. Taylor 《International journal of molecular sciences》2022,23(16)
Potentially traumatic experiences have been associated with chronic diseases. Epigenetic mechanisms, including DNA methylation (DNAm), have been proposed as an explanation for this association. We examined the association of experiences of trauma with epigenome-wide DNAm among African American mothers (n = 236) and their children aged 3–5 years (n = 232; N = 500), using the Life Events Checklist-5 (LEC) and Traumatic Events Screening Inventory—Parent Report Revised (TESI-PRR). We identified no DNAm sites significantly associated with potentially traumatic experience scores in mothers. One CpG site on the ENOX1 gene was methylome-wide-significant in children (FDR-corrected q-value = 0.05) from the TESI-PRR. This protein-coding gene is associated with mental illness, including unipolar depression, bipolar, and schizophrenia. Future research should further examine the associations between childhood trauma, DNAm, and health outcomes among this understudied and high-risk group. Findings from such longitudinal research may inform clinical and translational approaches to prevent adverse health outcomes associated with epigenetic changes. 相似文献
26.
A COMPREHENSIVE MODEL OF LASER CLADDING BY POWDER FEEDING 总被引:1,自引:0,他引:1
Y.L.Huang G.Y.Liang J.Y.Su 《金属学报(英文版)》2004,17(1):21-27
A novel model was presented to predict the evolutionary development of cladding layer,and a method based on Lambert-Beer theorem and Mie‘s theory was adopted to treat the interaction between powder stream and laser beam. By using the continuum model and enthalpy-porosity method, the fluid flow and heat transfer in solid-liquid phase change system were simulated. The commercial software PHOENICS, to which several modules were appended, was used to accomplish the simulation. Numerical computation was performed for Stellite 6 cladding on steel, the obtained results are coincident with those measured in experiment basically. 相似文献
27.
28.
T. Yamashita H. Akie Y. Nakano K. Kuramoto N. Nitani T. Nakamura 《Progress in Nuclear Energy》2001,38(3-4):327-330
Intention of the ROX-LWR system research is to provide an option for utilization or disposition of surplus plutonium. Researches on inert matrix materials and irradiation performance shows that the most favorable candidate for the ROX fuel is a particle dispersed fuel where small particles consisted of yttria stabilized zirconia, PuO2 and some additives are homogeneously dispersed in spinel matrix. Reactor safety analyses show that the ROX fueled PWR core has nearly the same performability as the existing UO2 fueled PWR under both reactivity initiated accidents and loss of coolant accidents. 相似文献
29.
30.
Fan Y. Chen 《Mechanism and Machine Theory》1972,7(4):453-460
The present paper deals with the synthesis of a cam profile when the prescribed acceleration pattern is given in numerical form. It is primarily an extension of previous work by the author with a view to upgrading the numerical accuracy of the synthesized cam profile, hence broadening the scope of application to a general class of high-speed cams. The technique is to differentiate the Stirling interpolation formula or the Gregory-Newton interpolation formula, thereby refining the prescribed initial acceleration data so that it will be correct to differences of high order. The effectiveness and the accuracy of this technique is demonstrated by a numerical example. 相似文献