全文获取类型
收费全文 | 5540篇 |
免费 | 128篇 |
国内免费 | 15篇 |
专业分类
化学 | 3467篇 |
晶体学 | 59篇 |
力学 | 89篇 |
数学 | 867篇 |
物理学 | 1201篇 |
出版年
2021年 | 55篇 |
2020年 | 79篇 |
2019年 | 80篇 |
2018年 | 53篇 |
2017年 | 46篇 |
2016年 | 98篇 |
2015年 | 106篇 |
2014年 | 113篇 |
2013年 | 209篇 |
2012年 | 209篇 |
2011年 | 231篇 |
2010年 | 164篇 |
2009年 | 149篇 |
2008年 | 209篇 |
2007年 | 175篇 |
2006年 | 172篇 |
2005年 | 166篇 |
2004年 | 174篇 |
2003年 | 133篇 |
2002年 | 155篇 |
2001年 | 101篇 |
2000年 | 117篇 |
1999年 | 101篇 |
1998年 | 73篇 |
1997年 | 98篇 |
1996年 | 88篇 |
1995年 | 65篇 |
1994年 | 88篇 |
1993年 | 94篇 |
1992年 | 81篇 |
1991年 | 69篇 |
1990年 | 75篇 |
1989年 | 70篇 |
1988年 | 59篇 |
1987年 | 72篇 |
1986年 | 84篇 |
1985年 | 93篇 |
1984年 | 74篇 |
1983年 | 75篇 |
1982年 | 73篇 |
1981年 | 61篇 |
1980年 | 76篇 |
1979年 | 70篇 |
1978年 | 78篇 |
1977年 | 86篇 |
1976年 | 87篇 |
1975年 | 73篇 |
1974年 | 61篇 |
1973年 | 75篇 |
1972年 | 49篇 |
排序方式: 共有5683条查询结果,搜索用时 15 毫秒
991.
A Self‐Digitization Dielectrophoretic (SD‐DEP) Chip for High‐Efficiency Single‐Cell Capture,On‐Demand Compartmentalization,and Downstream Nucleic Acid Analysis 下载免费PDF全文
Yuling Qin Li Wu Thomas Schneider Gloria S. Yen Jiasi Wang Shihan Xu Min Li Amy L. Paguirigan Jordan L. Smith Jerald P. Radich Prof. Robbyn K. Anand Prof. Daniel T. Chiu 《Angewandte Chemie (International ed. in English)》2018,57(35):11378-11383
The design and fabrication of a self‐digitization dielectrophoretic (SD‐DEP) chip with simple components for single‐cell manipulation and downstream nucleic acid analysis is presented. The device employed the traditional DEP and insulator DEP to create the local electric field that is tailored to approximately the size of single cells, enabling highly efficient single‐cell capture. The multistep procedures of cell manipulation, compartmentalization, lysis, and analysis were performed in the integrated microdevice, consuming minimal reagents, minimizing contamination, decreasing lysate dilution, and increasing assay sensitivity. The platform developed here could be a promising and powerful tool in single‐cell research for precise medicine. 相似文献
992.
993.
Hubert Delange 《Monatshefte für Mathematik》1993,116(3-4):175-196
Let (n) be the number of prime divisors ofn, counted with multiplicity. We denote byS(x, k) the set of thenx for which (n)=k, and byV
p(n) the exponent of the primep in the factorization ofn. In a previous paper we proved a result which implies that, ify=x/2
k
tends to infinity withk>2loglogx where >1, then the distribution of the numbers
on the setS(x, k) converges to the normal distribution of Gauss. Here, besides a slight improvement of that result, we give, for the moment of orderq of the above mentioned distribution, a formula which holds uniformly for 2loglogxklog (x/3)/log2 where 1<<3/2. 相似文献
994.
An inductively coupled plasma-atomic emission spectrometric method is reported for the determination of calcium, copper, iron, manganese, magnesium and zinc. Samples are introduced directly when a sheath gas device is used. An external calibration procedure is used. The standards are prepared in a matrix composed of 0.5% (w/v) albumin and 0.76% (w/v) sodium chloride. The procedure was evaluated with a standard reference material (NBS SRM 909 Human Serum); all the values obtained are in agreement with the certified values. Results obtained for the determination of zinc, calcium, magnesium, copper, iron and manganese in amniotic fluid samples are reported. 相似文献
995.
In this paper, the special construction of a parallel robot, called spatial servopneumatic multi-axis test facility, will be discussed. The investigations include the following aspects: (i) the laboratory set-up of the robot, (ii) various results obtained in laboratory experiments, taking into account quite different control algorithms and command-input signals, (iii) a comparison of the laboratory experiments with the computer simulations of Part I of this paper, and ({vi}) a quality check of the results compared with the cost of the different controller realizations. The results of both the computer simulations and the laboratory experiments show: (i) The dynamic behavior of the parallel structure can be tremendously improved by using sophisticated nonlinear control algorithms. (ii) This improvement has to be paid by a drastically increased amount of work for deriving the model equations and control algorithms, and by augmented hardware cost of the sensing elements and controller electronics. (iii) Carefully developed model equations and identified model parameters provide theoretical models of the complex parallel structure that are very close to reality. This enables the design engineer to systematically investigate constructive alternatives of the design parameters, sensor and actuator concepts, and control strategies of the MAP prior to their hardware realization.This work has been supported by the German Science Foundation (DFG) under Contract No. Ha 1666/6-3. 相似文献
996.
997.
998.
Wahl P Diekhöner L Schneider MA Vitali L Wittich G Kern K 《Physical review letters》2004,93(17):176603
Based on the experimental observation that only the close vicinity of a magnetic impurity at metal surfaces determines its Kondo behavior, we introduce a simple model which explains the Kondo temperatures observed for cobalt adatoms at the (111) and (100) surfaces of Cu, Ag, and Au. Excellent agreement between the model and scanning tunneling spectroscopy experiments is demonstrated. The Kondo temperature is shown to depend on the occupation of the d level determined by the hybridization between the adatom and the substrate with a minimum around single occupancy. 相似文献
999.
Winnerl S Orlita M Plochocka P Kossacki P Potemski M Winzer T Malic E Knorr A Sprinkle M Berger C de Heer WA Schneider H Helm M 《Physical review letters》2011,107(23):237401
We study the carrier dynamics in epitaxially grown graphene in the range of photon energies from 10 to 250 meV. The experiments complemented by microscopic modeling reveal that the carrier relaxation is significantly slowed down as the photon energy is tuned to values below the optical-phonon frequency; however, owing to the presence of hot carriers, optical-phonon emission is still the predominant relaxation process. For photon energies about twice the value of the Fermi energy, a transition from pump-induced transmission to pump-induced absorption occurs due to the interplay of interband and intraband processes. 相似文献
1000.
Gap detection thresholds as a function of tonal duration for younger and older listeners. 总被引:5,自引:0,他引:5
Twenty normal hearing younger and twenty older adults in the early stages of presbycusis, but with relatively normal hearing at 2 kHz, were asked to discriminate between the presence versus absence of a gap between two equal-duration tonal markers. The duration of each marker was constant within a block of trials but varied between 0.83 and 500 ms across blocks. Notched-noise, centered at 2 kHz, was used to mask on- and off-transients. Gap detection thresholds of older adults were markedly higher than those of younger adults for marker durations of less than 250 ms but converged on those of younger adults at 500 ms. For both age groups, gap detection thresholds were independent of audiometric thresholds. These results indicate that older adults have more difficulty detecting a gap than younger adults when short marker durations (i.e., durations characteristic of speech sounds) are employed. It is shown that these results cannot be explained by linear models of temporal processing but are consistent with differential adaptation effects in younger and older adults. 相似文献