全文获取类型
收费全文 | 17188篇 |
免费 | 2418篇 |
国内免费 | 1328篇 |
专业分类
化学 | 5727篇 |
晶体学 | 34篇 |
力学 | 2458篇 |
综合类 | 230篇 |
数学 | 1912篇 |
物理学 | 2812篇 |
无线电 | 7761篇 |
出版年
2024年 | 85篇 |
2023年 | 267篇 |
2022年 | 499篇 |
2021年 | 608篇 |
2020年 | 754篇 |
2019年 | 488篇 |
2018年 | 471篇 |
2017年 | 618篇 |
2016年 | 786篇 |
2015年 | 803篇 |
2014年 | 1110篇 |
2013年 | 1258篇 |
2012年 | 1128篇 |
2011年 | 1106篇 |
2010年 | 863篇 |
2009年 | 919篇 |
2008年 | 980篇 |
2007年 | 992篇 |
2006年 | 1006篇 |
2005年 | 888篇 |
2004年 | 776篇 |
2003年 | 694篇 |
2002年 | 520篇 |
2001年 | 461篇 |
2000年 | 422篇 |
1999年 | 378篇 |
1998年 | 323篇 |
1997年 | 278篇 |
1996年 | 256篇 |
1995年 | 212篇 |
1994年 | 175篇 |
1993年 | 144篇 |
1992年 | 113篇 |
1991年 | 86篇 |
1990年 | 83篇 |
1989年 | 56篇 |
1988年 | 66篇 |
1987年 | 41篇 |
1986年 | 29篇 |
1985年 | 36篇 |
1984年 | 33篇 |
1983年 | 12篇 |
1982年 | 32篇 |
1981年 | 16篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1978年 | 9篇 |
1977年 | 8篇 |
1975年 | 5篇 |
1957年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 21 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.
3.
The structure and rotational barrier for the mesityl-silicon bond of 2,2-dimesityl-1,1,1,3,3,3-hexamethyltrisilane have been investigated by 1H- and 13C-variable temperature nuclear magnetic resonance (NMR) as well as by density functional theory structural calculations. The calculations show that the lowest energy structure has C2 symmetry with nonequivalent ortho methyl groups, consistent with the crystal structure and solution NMR. The nonequivalent ortho methyl groups exchange through a Cs transition state with a calculated relative free energy of 11.0 kcal mol−1. The barrier for this rotation found by dynamic NMR is 13.4 ± 0.2 kcal mol−1 at 298 K. 相似文献
4.
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
5.
Dr. Liat Avram Dr. Václav Havel Ronit Shusterman-Krush Dr. Mark A. Iron Dr. Moritz Zaiss Prof. Vladimír Šindelář Dr. Amnon Bar-Shir 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(7):1687-1690
The accumulated knowledge regarding molecular architectures is based on established, reliable, and accessible analytical tools that provide robust structural and functional information on assemblies. However, both the dynamicity and low population of noncovalently interacting moieties within studied molecular systems limit the efficiency and accuracy of traditional methods. Herein, the use of a saturation transfer-based NMR approach to study the dynamic binding characteristics of an anion to a series of synthetic receptors derived from bambusuril macrocycles is demonstrated. The exchange rates of BF4− are mediated by the side chains on the receptor (100 s−1<kex<5000 s−1), which play a critical role in receptor-anion binding dynamics. The signal amplification obtained with this approach allows for the identification of different types of intermolecular interactions between the receptor and the anion, something that could not have been detected by techniques hitherto used to study molecular assemblies. These findings, which are supported by a computational molecular dynamic study, demonstrate the uniqueness and added value of this NMR method. 相似文献
6.
In this paper, we consider a viscoelastic wave equation of variable coefficients in the presence of past history with nonlinear damping and delay in the internal feedback and dynamic boundary conditions. Under suitable assumptions, we establish an explicit and general decay rate result without imposing restrictive assumption on the behavior of the relaxation function at infinity by Riemannian geometry method and Lyapunov functional method. 相似文献
7.
8.
With the proliferation of mobile computing technologies, location based services have been identified as one of the most promising
target application. We classify mobile information service domains based on feature characteristics of the information sources
and different patterns of mobile information access. By carefully examining the service requirements, we identify the dynamic
data management problem that must be addressed for effective location based services in mobile environments. We then devise
a general architecture and cost model for servicing both location independent and location dependent data. Based on the architecture
and cost model, we propose a set of dynamic data management strategies that employs judicious caching, proactive server pushing
and neighborhood replication to reduce service cost and improve response time under changing user mobility and access patterns.
Detail behavior analysis helps us in precisely capturing when and how to apply these strategies. Simulation results suggest
that different strategies are effective for different types of data in response to different patterns of movement and information
access.
Shiow-yang Wu is an associate professor of the Department of Computer Science and Information Engineering at National Dong Hwa University,
Hualien, Taiwan, R.O.C. He received the BS and MS degrees in computer engineering from National Chiao Tung University, Hsinchu,
Taiwan, ROC, and the PhD degree in computer science from the University of Texas at Austin in 1984, 1986, and 1995, respectively.
His research interests include data/knowledge bases, mobile computing, distributed processing, intelligence information systems,
and electronic commerce.
Kun-Ta Wu was born in Taipei, Taiwan, R.O.C., in 1976. He received the B.S. degree in computer science from Soochow University, Taipei,
Taiwan, R.O.C., in 1999 and the M.S. degree in computer science and information engineering from National Dong Hwa University,
Hualien, Taiwan, R.O.C., in 2001.
Currently, he is an Assistant Researcher in the Domestic Division at Science and Technology Information Center, National Science
Council, R.O.C., as a member of Information Gathering and Analysis Group of National Information and Communication Security
Taskforce. His research interests include mobile computing, wireless network and information security. 相似文献
9.
10.