全文获取类型
收费全文 | 840篇 |
免费 | 24篇 |
国内免费 | 13篇 |
专业分类
化学 | 485篇 |
晶体学 | 1篇 |
力学 | 24篇 |
数学 | 175篇 |
物理学 | 192篇 |
出版年
2020年 | 10篇 |
2019年 | 9篇 |
2017年 | 5篇 |
2016年 | 21篇 |
2015年 | 14篇 |
2014年 | 17篇 |
2013年 | 30篇 |
2012年 | 30篇 |
2011年 | 47篇 |
2010年 | 10篇 |
2009年 | 13篇 |
2008年 | 31篇 |
2007年 | 24篇 |
2006年 | 41篇 |
2005年 | 36篇 |
2004年 | 33篇 |
2003年 | 31篇 |
2002年 | 39篇 |
2001年 | 23篇 |
2000年 | 25篇 |
1999年 | 11篇 |
1998年 | 10篇 |
1997年 | 11篇 |
1996年 | 11篇 |
1995年 | 11篇 |
1994年 | 9篇 |
1993年 | 12篇 |
1992年 | 10篇 |
1991年 | 11篇 |
1990年 | 11篇 |
1989年 | 9篇 |
1988年 | 14篇 |
1987年 | 12篇 |
1986年 | 9篇 |
1985年 | 13篇 |
1984年 | 11篇 |
1983年 | 9篇 |
1982年 | 10篇 |
1981年 | 10篇 |
1980年 | 8篇 |
1979年 | 9篇 |
1978年 | 10篇 |
1977年 | 10篇 |
1976年 | 14篇 |
1975年 | 14篇 |
1974年 | 7篇 |
1973年 | 8篇 |
1972年 | 7篇 |
1971年 | 6篇 |
1968年 | 6篇 |
排序方式: 共有877条查询结果,搜索用时 15 毫秒
871.
Xuemei Wang Jian Zhou Tsz Kin Tam Evgeny Katz Marcos Pita 《Bioelectrochemistry (Amsterdam, Netherlands)》2009,77(1):69-73
Application of Boolean logic operations performed by enzymes to control electrochemical systems is presented. Indium–tin oxide (ITO) electrodes with the surface modified with poly-4-vinyl pyridine (P4VP) brush were synthesized and used as switchable electrochemical systems. The switch ON and OFF of the electrode activity were achieved by pH changes generated in situ by biocatalytic reactions in the presence of enzymes used as input signals. Two logic gates operating as AND/OR Boolean functions were designed using invertase and glucose oxidase or esterase and glucose oxidase as input signals, respectively. The electrode surface coated with a shrunk P4VP polymer at neutral pH values was not electrochemically active because of the blocking effect of the polymer film. The positive outputs of the logic operations yielded a pH drop to acidic conditions, resulting in the protonation and swelling of the P4VP polymer allowing penetration of a soluble redox probe to the conducting support, thus switching the electrode activity ON. The electrode interface was reset to the initial OFF state, with the inhibited electrochemical reaction, upon in situ pH increase generated by another enzymatic reaction in the presence of urease. Logically processed biochemical inputs of various enzymes allowed reversible activation–inactivation of the electrochemical reaction. 相似文献
872.
Daniel J. Katz 《Designs, Codes and Cryptography》2012,65(3):291-324
We present a theorem that generalizes the result of Delsarte and McEliece on the p-divisibilities of weights in abelian codes. Our result generalizes the Delsarte–McEliece theorem in the same sense that the theorem of N. M. Katz generalizes the theorem of Ax on the p-divisibilities of cardinalities of affine algebraic sets over finite fields. As the Delsarte–McEliece theorem implies the theorem of Ax, so our generalization implies that of N. M. Katz. The generalized theorem gives the p-divisibility of the t-wise Hamming weights of t-tuples of codewords (c (1), . . . ,c (t)) as these words range over a product of abelian codes, where the t-wise Hamming weight is defined as the number of positions i in which the codewords do not simultaneously vanish, i.e., for which ${(c^{(1)}_i,\ldots,c^{(t)}_i)\not=(0,\ldots,0)}$ . We also present a version of the theorem that, for any list of t symbols s 1, . . . ,s t , gives p-adic estimates of the number of positions i such that ${(c^{(1)}_i,\ldots,c^{(t)}_i)=(s_1,\ldots,s_t)}$ as these words range over a product of abelian codes. 相似文献
873.
Collins C Katz N Wallace J Jara-Almonte J Reese I Zweibel E Forest CB 《Physical review letters》2012,108(11):115001
A new concept for spinning unmagnetized plasma is demonstrated experimentally. Plasma is confined by an axisymmetric multicusp magnetic field and biased cathodes are used to drive currents and impart a torque in the magnetized edge. Measurements show that flow viscously couples momentum from the magnetized edge (where the plasma viscosity is small) into the unmagnetized core (where the viscosity is large) and that the core rotates as a solid body. To be effective, collisional viscosity must overcome the ion-neutral drag due to charge-exchange collisions. 相似文献
874.
Probabilistic inference—the process of estimating the values of unobserved variables in probabilistic models—has been used to describe various cognitive phenomena related to learning and memory. While the study of biological realizations of inference has focused on animal nervous systems, single-celled organisms also show complex and potentially “predictive” behaviors in changing environments. Yet, it is unclear how the biochemical machinery found in cells might perform inference. Here, we show how inference in a simple Markov model can be approximately realized, in real-time, using polymerizing biochemical circuits. Our approach relies on assembling linear polymers that record the history of environmental changes, where the polymerization process produces molecular complexes that reflect posterior probabilities. We discuss the implications of realizing inference using biochemistry, and the potential of polymerization as a form of biological information-processing. 相似文献
875.
Jinfeng Han Yufeng Jiang Emma Tiernan Connor Ganley Yunjia Song Taein Lee Arlene Chiu Patty McGuiggan Nicholas Adams Paulette Clancy Thomas P Russell Patrick E. Hopkins Susanna M. Thon John D. Tovar Howard E. Katz 《Angewandte Chemie (International ed. in English)》2023,62(23):e202219313
N-Type thermoelectrics typically consist of small molecule dopant+polymer host. Only a few polymer dopant+polymer host systems have been reported, and these have lower thermoelectric parameters. N-type polymers with high crystallinity and order are generally used for high-conductivity ( ) organic conductors. Few n-type polymers with only short-range lamellar stacking for high-conductivity materials have been reported. Here, we describe an n-type short-range lamellar-stacked all-polymer thermoelectric system with highest of 78 S−1, power factor (PF) of 163 μW m−1 K−2, and maximum Figure of merit (ZT) of 0.53 at room temperature with a dopant/host ratio of 75 wt%. The minor effect of polymer dopant on the molecular arrangement of conjugated polymer PDPIN at high ratios, high doping capability, high Seebeck coefficient (S) absolute values relative to , and atypical decreased thermal conductivity ( ) with increased doping ratio contribute to the promising performance. 相似文献
876.
Aluminum - epoxy single lap joints were subjected at different temperatures to torsional vibrations at constant amplitude superimposed on a creep load. This combination of dynamic and static stresses was chosen in order to simulate to a certain extent the real service conditions of an ordinary bonded joint. The shear strength of these joints was checked in tension at room temperature after their removal from the special device in which the superimposed stresses were applied. It was found that the shear strength of the joint is very dependent on its thermo-mechanical history. DSC analyses and SEM micrographs of the failure surface were used in an attempt to find some correlation between the mechanical properties and the microstructure of the adhesive. 相似文献
877.