全文获取类型
收费全文 | 57218篇 |
免费 | 2491篇 |
国内免费 | 194篇 |
专业分类
电工技术 | 874篇 |
综合类 | 93篇 |
化学工业 | 10857篇 |
金属工艺 | 2070篇 |
机械仪表 | 3065篇 |
建筑科学 | 1244篇 |
矿业工程 | 52篇 |
能源动力 | 2179篇 |
轻工业 | 4105篇 |
水利工程 | 255篇 |
石油天然气 | 210篇 |
武器工业 | 1篇 |
无线电 | 10129篇 |
一般工业技术 | 11468篇 |
冶金工业 | 5817篇 |
原子能技术 | 630篇 |
自动化技术 | 6854篇 |
出版年
2024年 | 206篇 |
2023年 | 602篇 |
2022年 | 840篇 |
2021年 | 1503篇 |
2020年 | 1131篇 |
2019年 | 1009篇 |
2018年 | 1333篇 |
2017年 | 1326篇 |
2016年 | 1650篇 |
2015年 | 1302篇 |
2014年 | 2032篇 |
2013年 | 3480篇 |
2012年 | 3193篇 |
2011年 | 3904篇 |
2010年 | 2970篇 |
2009年 | 3163篇 |
2008年 | 2917篇 |
2007年 | 2461篇 |
2006年 | 2242篇 |
2005年 | 1937篇 |
2004年 | 1848篇 |
2003年 | 1699篇 |
2002年 | 1650篇 |
2001年 | 1290篇 |
2000年 | 1204篇 |
1999年 | 1182篇 |
1998年 | 2194篇 |
1997年 | 1436篇 |
1996年 | 1203篇 |
1995年 | 961篇 |
1994年 | 724篇 |
1993年 | 683篇 |
1992年 | 490篇 |
1991年 | 494篇 |
1990年 | 417篇 |
1989年 | 404篇 |
1988年 | 321篇 |
1987年 | 275篇 |
1986年 | 254篇 |
1985年 | 231篇 |
1984年 | 199篇 |
1983年 | 151篇 |
1982年 | 152篇 |
1981年 | 130篇 |
1980年 | 130篇 |
1979年 | 102篇 |
1978年 | 94篇 |
1977年 | 123篇 |
1976年 | 158篇 |
1975年 | 80篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
Joon Seok Lee Hyun Geun Cho Jeong Yeop Ryu Eun Jung Oh Hyun Mi Kim Suin Kwak Seok-Jong Lee Jongmin Lee Sang Yub Lee Seung Huh Ji Yoon Kim Ho Yun Chung 《International journal of molecular sciences》2022,23(16)
Arteriovenous malformation (AVM) is characterized by high-flow blood vessels connecting arteries and veins without capillaries. This disease shows increased angiogenesis and a pathophysiological hypoxic environment in proximal tissues. Here, we analyzed the effects of hypoxia on angiogenesis in the endothelial cells (ECs) of AVM and normal tissues. ECs from human normal and AVM tissues were evaluated using immunocytochemistry with CD31. In vitro tube formation under hypoxia was tested in both ECs using Matrigel. The relative expression of angiogenesis-related genes was measured using real-time PCR. Under normoxia, CD31 was significantly higher in AVM ECs (79.23 ± 0.65%) than in normal ECs (74.15 ± 0.70%). Similar results were observed under hypoxia in AVM ECs (63.85 ± 1.84%) and normal ECs (60.52 ± 0.51%). In the tube formation test under normoxic and hypoxic conditions, the junction count and total vessel length were significantly greater in AVM ECs than normal ECs. Under both normoxia and hypoxia, the angiogenesis-related gene FSTL1 showed a significantly higher expression in AVM ECs than in normal ECs. Under hypoxia, CSPG4 expression was significantly lower in AVM ECs than in normal ECs. Accordingly, the angiogenic effect was increased in AVM ECs compared with that in normal ECs. These results provide a basic knowledge for an AVM treatment strategy. 相似文献
52.
Scientometrics - As technology convergence is attracting increasing attention, many companies pay attention to human resources planning for the convergence R&D. This study proposes a... 相似文献
53.
54.
55.
Magnetic Resonance Materials in Physics, Biology and Medicine - Our goal is to design and validate a simple apparatus for the safety assessments of magnetically induced torques by four active... 相似文献
56.
The effect of variations in composition on optical properties was studied. The index of refraction is lowered by the substitution of fluorine and alumina for silica; the reciprocal dispersion, however, is increased by fluorine and lowered by alumina so that fluorine and alumina can be balanced against each other to give almost any desired optical properties within the field investigated, that is, in the range of 1.46 to 1.50 for index of refraction and 63 to 70 for the reciprocal dispersion. 相似文献
57.
Hyeri Park Jin Seok Jun Hyeong You Dae Hyun Lee Ja-Yun Lim Gi Jin Kim 《International journal of molecular sciences》2022,23(24)
Mesenchymal stem cells (MSCs) are next-generation treatment in degenerative diseases. For the application of mesenchymal stem cell therapy to degenerative disease, transplantation conditions (e.g., optimized dose, delivery route and regenerating efficacy) should be considered. Recently, researchers have studied the mode of action of MSC in the treatment of ovarian degenerative disease. However, the evidence for the optimal number of cells for the developing stem cell therapeutics is insufficient. The objective of this study was to evaluate the efficacy in ovarian dysfunction, depends on cell dose. By intraovarian transplantation of low (1 × 105) and high (5 × 105) doses of placenta-derived mesenchymal stem cells (PD-MSCs) into thioacetamide (TAA)-injured rats, we compared the levels of apoptosis and oxidative stress that depend on different cell doses. Apoptosis and oxidative stress were significantly decreased in the transplanted (Tx) group compared to the non-transplanted (NTx) group in ovarian tissues from TAA-injured rats (* p < 0.05). In addition, we confirmed that follicular development was significantly increased in the Tx groups compared to the NTx group (* p < 0.05). However, there were no significant differences in the apoptosis, antioxidant or follicular development of injured ovarian tissues between the low and high doses PD-MSCs group. These findings provide new insights into the understanding and evidence obtained from clinical trials for stem cell therapy in reproductive systems. 相似文献
58.
59.
Hung-Chieh Lee Wei-Lin Lai Cheng-Yung Lin Chih-Wei Zeng Jin-Chuan Sheu Tze-Bin Chou Huai-Jen Tsai 《International journal of molecular sciences》2022,23(24)
After spinal cord injury (SCI) in mammals, neuronal regeneration is limited; in contrast, such regeneration occurs quickly in zebrafish. Member A of the acidic nuclear phosphoprotein 32 (ANP32a) family is involved in neuronal development, but its function is controversial, and its involvement in zebrafish SCI remains unknown. To determine the role of zebrafish ANP32a in the neuronal regeneration of SCI embryos, we microinjected ANP32a mRNA into embryos from zebrafish transgenic line Tg(mnx1:GFP) prior to SCI. Compared to control SCI embryos, the results showed that the regeneration of spinal cord and resumption of swimming capability were promoted by the overexpression of ANP32a mRNA but reduced by its knockdown. We next combined fluorescence-activated cell sorting with immunochemical staining of anti-GFAP and immunofluorescence staining against anti-PH3 on Tg(gfap:GFP) SCI embryos. The results showed that ANP32a promoted the proliferation and cell number of radial glial cells at the injury epicenter at 24 h post-injury (hpi). Moreover, when we applied BrdU labeling to SCI embryos derived from crossing the Tg(gfap:GFP) and Tg(mnx1:TagRFP) lines, we found that both radial glial cells and motor neurons had proliferated, along with their increased cell numbers in Anp32a-overexpression SCI-embryos. On this basis, we conclude that ANP32a plays a positive role in the regeneration of zebrafish SCI embryos. 相似文献
60.