全文获取类型
收费全文 | 404934篇 |
免费 | 5435篇 |
国内免费 | 1353篇 |
专业分类
电工技术 | 7700篇 |
综合类 | 306篇 |
化学工业 | 59317篇 |
金属工艺 | 16503篇 |
机械仪表 | 13538篇 |
建筑科学 | 8398篇 |
矿业工程 | 2153篇 |
能源动力 | 11617篇 |
轻工业 | 28456篇 |
水利工程 | 4278篇 |
石油天然气 | 7905篇 |
武器工业 | 17篇 |
无线电 | 49529篇 |
一般工业技术 | 83624篇 |
冶金工业 | 75726篇 |
原子能技术 | 9279篇 |
自动化技术 | 33376篇 |
出版年
2021年 | 3913篇 |
2020年 | 2978篇 |
2019年 | 3843篇 |
2018年 | 6533篇 |
2017年 | 6510篇 |
2016年 | 6977篇 |
2015年 | 4356篇 |
2014年 | 7207篇 |
2013年 | 20224篇 |
2012年 | 11513篇 |
2011年 | 15446篇 |
2010年 | 12259篇 |
2009年 | 13857篇 |
2008年 | 14197篇 |
2007年 | 13939篇 |
2006年 | 12544篇 |
2005年 | 11226篇 |
2004年 | 10623篇 |
2003年 | 10530篇 |
2002年 | 9938篇 |
2001年 | 9811篇 |
2000年 | 9198篇 |
1999年 | 9628篇 |
1998年 | 24586篇 |
1997年 | 16901篇 |
1996年 | 12967篇 |
1995年 | 9612篇 |
1994年 | 8449篇 |
1993年 | 8387篇 |
1992年 | 6038篇 |
1991年 | 5685篇 |
1990年 | 5669篇 |
1989年 | 5288篇 |
1988年 | 5011篇 |
1987年 | 4393篇 |
1986年 | 4297篇 |
1985年 | 4813篇 |
1984年 | 4411篇 |
1983年 | 3974篇 |
1982年 | 3642篇 |
1981年 | 3712篇 |
1980年 | 3431篇 |
1979年 | 3329篇 |
1978年 | 3318篇 |
1977年 | 3741篇 |
1976年 | 4861篇 |
1975年 | 2847篇 |
1974年 | 2649篇 |
1973年 | 2714篇 |
1972年 | 2271篇 |
排序方式: 共有10000条查询结果,搜索用时 526 毫秒
91.
High Temperature - The influence of heating from 260 to 400 K on the structure and mechanism of the formation of a molecular water film adsorbed on the walls of a plane fracture with the width of... 相似文献
92.
Masahiro Sato Miyu Koriyama Satoshi Watanabe Masato Ohtsuka Takayuki Sakurai Emi Inada Issei Saitoh Shingo Nakamura Kazuchika Miyoshi 《International journal of molecular sciences》2015,16(8):17838-17856
Some reports demonstrated successful genome editing in pigs by one-step zygote microinjection of mRNA of CRISPR/Cas9-related components. Given the relatively long gestation periods and the high cost of housing, the establishment of a single blastocyst-based assay for rapid optimization of the above system is required. As a proof-of-concept, we attempted to disrupt a gene (GGTA1) encoding the α-1,3-galactosyltransferase that synthesizes the α-Gal epitope using parthenogenetically activated porcine oocytes. The lack of α-Gal epitope expression can be monitored by staining with fluorescently labeled isolectin BS-I-B4 (IB4), which binds specifically to the α-Gal epitope. When oocytes were injected with guide RNA specific to GGTA1 together with enhanced green fluorescent protein (EGFP) and human Cas9 mRNAs, 65% (24/37) of the developing blastocysts exhibited green fluorescence, although almost all (96%, 23/24) showed a mosaic fluorescent pattern. Staining with IB4 revealed that the green fluorescent area often had a reduced binding activity to IB4. Of the 16 samples tested, six (five fluorescent and one non-fluorescent blastocysts) had indel mutations, suggesting a correlation between EGFP expression and mutation induction. Furthermore, it is suggested that zygote microinjection of mRNAs might lead to the production of piglets with cells harboring various mutation types. 相似文献
93.
94.
95.
Bochkareva N. I. Ivanov A. M. Klochkov A. V. Kogotkov V. S. Rebane Yu. T. Virko M. V. Shreter Y. G. 《Semiconductors》2015,49(6):827-835
Semiconductors - It is shown that the emission efficiency and the 1/f noise level in light-emitting diodes with InGaN/GaN quantum wells correlate with how the differential resistance of a diode... 相似文献
96.
Angelico Mendy Nervana Metwali Sarah S. Perry Elizabeth A. Chrischilles Kai Wang Peter S. Thorne 《Indoor air》2020,30(1):88-97
Endotoxin exacerbates asthma. We designed the Louisa Environmental Intervention Project (LEIP) and assessed its effectiveness in reducing household endotoxin and improving asthma symptoms in rural Iowa children. Asthmatic school children (N = 104 from 89 homes) of Louisa and Keokuk counties in Iowa (aged 5-14 years) were recruited and block-randomized to receive extensive (education + professional cleaning) or educational interventions. Environmental sampling collection and respiratory survey administration were done at baseline and during three follow-up visits. Mixed-model analyses were used to assess the effect of the intervention on endotoxin levels and asthma symptoms in the main analysis and of endotoxin reduction on asthma symptoms in exploratory analysis. In the extensive intervention group, dust endotoxin load was significantly reduced in post-intervention visits. The extensive compared with the educational intervention was associated with significantly decreased dust endotoxin load in farm homes and less frequent nighttime asthma symptoms. In exploratory analysis, dust endotoxin load reduction from baseline was associated with lower total asthma symptoms score (Odds ratio: 0.52, 95% confidence interval: 0.29-0.92). In conclusion, the LEIP intervention reduced household dust endotoxin and improved asthma symptoms. However, endotoxin reductions were not sustained post-intervention by residents. 相似文献
97.
98.
99.
100.