全文获取类型
收费全文 | 8836篇 |
免费 | 1033篇 |
国内免费 | 711篇 |
专业分类
化学 | 3995篇 |
晶体学 | 14篇 |
力学 | 109篇 |
综合类 | 81篇 |
数学 | 417篇 |
物理学 | 1346篇 |
无线电 | 4618篇 |
出版年
2024年 | 39篇 |
2023年 | 124篇 |
2022年 | 263篇 |
2021年 | 343篇 |
2020年 | 383篇 |
2019年 | 242篇 |
2018年 | 207篇 |
2017年 | 265篇 |
2016年 | 382篇 |
2015年 | 431篇 |
2014年 | 633篇 |
2013年 | 593篇 |
2012年 | 547篇 |
2011年 | 590篇 |
2010年 | 451篇 |
2009年 | 509篇 |
2008年 | 539篇 |
2007年 | 556篇 |
2006年 | 528篇 |
2005年 | 472篇 |
2004年 | 430篇 |
2003年 | 334篇 |
2002年 | 251篇 |
2001年 | 200篇 |
2000年 | 186篇 |
1999年 | 182篇 |
1998年 | 162篇 |
1997年 | 131篇 |
1996年 | 123篇 |
1995年 | 91篇 |
1994年 | 78篇 |
1993年 | 67篇 |
1992年 | 44篇 |
1991年 | 34篇 |
1990年 | 27篇 |
1989年 | 27篇 |
1988年 | 20篇 |
1987年 | 17篇 |
1986年 | 11篇 |
1985年 | 12篇 |
1984年 | 12篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1979年 | 5篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1974年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Edward G. Sheetz Zhao Zhang Alyssa Marogil Minwei Che Dr. Maren Pink Dr. Veronica Carta Prof. Dr. Krishnan Raghavachari Prof. Dr. Amar H. Flood 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(60):e202201584
The recognition of boron compounds is well developed as boronic acids but untapped as organotrifluoroborate anions (R−BF3−). We are exploring the development of these and other designer anions as anion-recognition motifs by considering them as substituted versions of the parent inorganic ion. To this end, we demonstrate strong and reliable binding of organic trifluoroborates, R−BF3−, by cyanostar macrocycles that are size-complementary to the inorganic BF4− progenitors. We find that recognition is modulated by the substituent's sterics and that the affinities are retained using the common K+ salts of R−BF3− anions. 相似文献
2.
《Current Applied Physics》2015,15(11):1296-1302
One-dimensional ZnO materials have been promising for field-emission (FE) application, but how to facially control the alignment of ZnO emitters is still a great challenge especially for patterned display application. Here, we report the fabrication of novel ZnO nanowire (NW) line and bundle arrays for patterned field-electron emitters. The effects of PS template size and heating time on the resulted ZnO nanoarrays were systematically studied. The deformation degree of PS templates was controlled and hence utilized to adjust the alignment of electrochemically deposited ZnO arrays. It was found that the length of NW lines and the density of NW bundles can effectively tuned by the PS template heating time. The optimal FE performance with turn-on electric field as low as of 4.4 V μm−1 and the field-enhancement factor as high as of 1450 were achieved through decreasing the screening effect among the patterned field-electron emitters. 相似文献
3.
Wenqing Zhang Dr. Jiuxing Li Prof. Dr. Bruno Salena Prof. Dr. Yingfu Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(3):592-596
DNA detection is usually conducted under nondenaturing conditions to favor the formation of Watson–Crick base-paring interactions. However, although such a setting is excellent for distinguishing a single-nucleotide polymorphism (SNP) within short DNA sequences (15–25 nucleotides), it does not offer a good solution to SNP detection within much longer sequences. Here we report on a new detection method capable of detecting SNP in a DNA sequence containing 35–90 nucleotides. This is achieved through incorporating into the recognition DNA sequence a previously discovered DNA molecule that forms a stable G-quadruplex in the presence of 7 molar urea, a known condition for denaturing DNA structures. The systems are configured to produce both colorimetric and fluorescent signals upon target binding. 相似文献
4.
5.
6.
通过对目前宽带线路数最多的10个国家和地区、2003年上半年新增线路最多的10个国家、全球宽带业务普及率最高的10个国家和地区、部分运营商住宅DSL业务的第一年费用以及2000~2002年全球入门级住宅DSL业务价格的发展趋势等图表的分析,阐明了全球宽带接入市场的发展状况,指出了其市场规模继续扩大、经济发达国家宽带线路增长速度较快、普及率的差距逐渐缩小以及业务价格趋于稳定等特点. 相似文献
7.
8.
本文提出了全真信息、信息的亲善性等概念,讨论了信息的有关性质及运算的关系,得到了信息的运算与普通集合运算之间存在着差异的结论,说明了引起该差异的原因.同时,以认知模式为基础,定义了信息函数,并得到了有关的命题及运算. 相似文献
9.
Laser welding is one of the most precise welding processes in joining sheet metals. In laser welding, performing real time evaluation of the welding quality is very important to enhance the efficiency of the welding process. In this study, the plasma and spatter, which are generated during laser welding, are measured using UV and IR photodiodes. The factors that influence weld quality are classified into five categories; optimal heat input, slightly low heat input, low heat input, partial joining due to gap mismatch, and nozzle deviation. The data number deviated from reference signals and their standard deviations were also considered to evaluate the qualities. A system was also formulated to perform real time evaluations of the weld quality using a fuzzy multi-feature pattern recognition with the measured signals. 相似文献