全文获取类型
收费全文 | 622456篇 |
免费 | 13324篇 |
国内免费 | 4612篇 |
专业分类
电工技术 | 13859篇 |
技术理论 | 9篇 |
综合类 | 7125篇 |
化学工业 | 93606篇 |
金属工艺 | 29443篇 |
机械仪表 | 25505篇 |
建筑科学 | 19179篇 |
矿业工程 | 5245篇 |
能源动力 | 15875篇 |
轻工业 | 38334篇 |
水利工程 | 7521篇 |
石油天然气 | 13589篇 |
武器工业 | 505篇 |
无线电 | 72393篇 |
一般工业技术 | 122347篇 |
冶金工业 | 88732篇 |
原子能技术 | 10992篇 |
自动化技术 | 76133篇 |
出版年
2022年 | 4460篇 |
2021年 | 7362篇 |
2020年 | 5530篇 |
2019年 | 6139篇 |
2018年 | 26126篇 |
2017年 | 25820篇 |
2016年 | 20817篇 |
2015年 | 8538篇 |
2014年 | 11964篇 |
2013年 | 26393篇 |
2012年 | 21637篇 |
2011年 | 34911篇 |
2010年 | 29739篇 |
2009年 | 28182篇 |
2008年 | 29123篇 |
2007年 | 30909篇 |
2006年 | 17909篇 |
2005年 | 19275篇 |
2004年 | 15974篇 |
2003年 | 15400篇 |
2002年 | 13323篇 |
2001年 | 12185篇 |
2000年 | 11917篇 |
1999年 | 12429篇 |
1998年 | 27288篇 |
1997年 | 18995篇 |
1996年 | 14867篇 |
1995年 | 11282篇 |
1994年 | 9872篇 |
1993年 | 9559篇 |
1992年 | 6929篇 |
1991年 | 6397篇 |
1990年 | 6295篇 |
1989年 | 5886篇 |
1988年 | 5535篇 |
1987年 | 4775篇 |
1986年 | 4642篇 |
1985年 | 5135篇 |
1984年 | 4707篇 |
1983年 | 4237篇 |
1982年 | 3896篇 |
1981年 | 3945篇 |
1980年 | 3623篇 |
1979年 | 3526篇 |
1978年 | 3494篇 |
1977年 | 3948篇 |
1976年 | 5066篇 |
1975年 | 3006篇 |
1974年 | 2784篇 |
1973年 | 2833篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
Golubev N. V. Ignat’eva E. S. Maurus A. A. Ziyatdinova M. Z. Lopatina E. V. Lorenzi R. Paleari A. Sigaev V. N. 《Glass and Ceramics》2021,77(11-12):415-418
Glass and Ceramics - The influence of Al2O3 as an additive and the heat-treatment regime on the luminescence spectra of gallate glass-ceramics was investigated. It is shown that its luminescence... 相似文献
63.
Katja F. Hellendahl Felix Kaspar Dr. Xinrui Zhou Zhaoyi Yang Prof. Dr. Zhen Huang Prof. Dr. Peter Neubauer Dr. Anke Kurreck 《Chembiochem : a European journal of chemical biology》2021,22(11):2002-2009
Selenium-modified nucleosides are powerful tools to study the structure and function of nucleic acids and their protein interactions. The widespread application of 2-selenopyrimidine nucleosides is currently limited by low yields in established synthetic routes. Herein, we describe the optimization of the synthesis of 2-Se-uridine and 2-Se-thymidine derivatives by thermostable nucleoside phosphorylases in transglycosylation reactions using natural uridine or thymidine as sugar donors. Reactions were performed at 60 or 80 °C and at pH 9 under hypoxic conditions to improve the solubility and stability of the 2-Se-nucleobases in aqueous media. To optimize the conversion, the reaction equilibria in analytical transglycosylation reactions were studied. The equilibrium constants of phosphorolysis of the 2-Se-pyrimidines were between 5 and 10, and therefore differ by an order of magnitude from the equilibrium constants of any other known case. Hence, the thermodynamic properties of the target nucleosides are inherently unfavorable, and this complicates their synthesis significantly. A tenfold excess of sugar donor was needed to achieve 40−48 % conversion to the target nucleoside. Scale-up of the optimized conditions provided four Se-containing nucleosides in 6–40 % isolated yield, which compares favorably to established chemical routes. 相似文献
64.
Ava Kwong Cecilia Y. S. Ho Vivian Y. Shin Chun Hang Au Tsun Leung Chan Edmond S. K. Ma 《International journal of molecular sciences》2021,22(2)
The germline carrier of the BRCA1 pathogenic mutation has been well proven to confer an increased risk of breast and ovarian cancer. Despite BRCA1 biallelic pathogenic mutations being extremely rare, they have been reported to be embryonically lethal or to cause Fanconi anemia (FA). Here we describe a patient who was a 48-year-old female identified with biallelic pathogenic mutations of the BRCA1 gene, with no or very subtle FA-features. She was diagnosed with ovarian cancer and breast cancer at the ages of 43 and 44 and had a strong family history of breast and gynecological cancers. 相似文献
65.
66.
Klimis?S.?NtalianisEmail author Anastasios?D.?Doulamis Nikolaos?D.?Doulamis Nikos?E.?Mastorakis Athanasios?S.?Drigas 《Journal of Signal Processing Systems》2015,80(2):153-161
In this paper, we present a novel memory access reduction scheme (MARS) for two-dimension fast cosine transform (2-D FCT). It targets programmable DSPs with high memory-access latency. It reduces the number of memory accesses by: 1) reducing the number of weighting factors and 2) combining butterflies in vector-radix 2-D FCT pruning diagram from two stages to one stage with an efficient structure. Hardware platform based on general purpose processor is used to verify the effectiveness of the proposed method for vector-radix 2-D FCT pruning implementation. Experimental results validate the benefits of the proposed method with reduced memory access, less clock cycle and fewer memory space compared with the conventional implementation. 相似文献
67.
68.
69.
World Wide Web - Rule mechanism has been widely used in many areas, such as databases, artificial intelligent and pervasive computing. In a rule mechanism, rule activation decides which rules are... 相似文献
70.
Fluorescence‐Activated Cell Sorters: Standing Surface Acoustic Wave (SSAW)‐Based Fluorescence‐Activated Cell Sorter (Small 40/2018)
下载免费PDF全文
![点击此处可从《Small (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)