全文获取类型
收费全文 | 188132篇 |
免费 | 2480篇 |
国内免费 | 530篇 |
专业分类
化学 | 100490篇 |
晶体学 | 2226篇 |
力学 | 7667篇 |
综合类 | 15篇 |
数学 | 21521篇 |
物理学 | 59223篇 |
出版年
2020年 | 1579篇 |
2019年 | 1540篇 |
2018年 | 1957篇 |
2017年 | 1928篇 |
2016年 | 3442篇 |
2015年 | 2299篇 |
2014年 | 3295篇 |
2013年 | 8099篇 |
2012年 | 6538篇 |
2011年 | 8034篇 |
2010年 | 5502篇 |
2009年 | 5278篇 |
2008年 | 7319篇 |
2007年 | 7302篇 |
2006年 | 6870篇 |
2005年 | 6304篇 |
2004年 | 5545篇 |
2003年 | 4805篇 |
2002年 | 4677篇 |
2001年 | 5065篇 |
2000年 | 3911篇 |
1999年 | 2996篇 |
1998年 | 2609篇 |
1997年 | 2553篇 |
1996年 | 2433篇 |
1995年 | 2315篇 |
1994年 | 2341篇 |
1993年 | 2182篇 |
1992年 | 2498篇 |
1991年 | 2442篇 |
1990年 | 2255篇 |
1989年 | 2225篇 |
1988年 | 2146篇 |
1987年 | 2061篇 |
1986年 | 1955篇 |
1985年 | 2627篇 |
1984年 | 2732篇 |
1983年 | 2254篇 |
1982年 | 2441篇 |
1981年 | 2321篇 |
1980年 | 2275篇 |
1979年 | 2395篇 |
1978年 | 2539篇 |
1977年 | 2422篇 |
1976年 | 2424篇 |
1975年 | 2331篇 |
1974年 | 2374篇 |
1973年 | 2317篇 |
1972年 | 1492篇 |
1971年 | 1361篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
101.
The breakup of suspended, agglomerated submicron particles was studied by exposing the aerosol to weak shock waves of varying strength under conditions 400 ms?1?v?880 ms?1. A newly developed laser light-scattering diagnostic employing a top hat laser profile was used to size the particles passing through a very small scattering volume. By Comparing the optically measured particle size in front of and behind shock waves, the breakup of agglomerated particles could be clearly identified. The experiments indicate that the aerodynamic forces behind an incident shock overcome the particle binding force resulting in disintegration of the submicron agglomerates. The results are presented in form of a modified Weber number. 相似文献
102.
Jürgen Kurths M. Carmen Romano Marco Thiel Grigory V. Osipov Mikhail V. Ivanchenko István Z. Kiss John L. Hudson 《Nonlinear dynamics》2006,44(1-4):135-149
We present two different approaches to detect and quantify phase synchronization in the case of coupled non-phase coherent
oscillators. The first one is based on the general idea of curvature of an arbitrary curve. The second one is based on recurrences
of the trajectory in phase space. We illustrate both methods in the paradigmatic example of the R?ssler system in the funnel
regime. We show that the second method is applicable even in the case of noisy data. Furthermore, we extend the second approach
to the application of chains of coupled systems, which allows us to detect easily clusters of synchronized oscillators. In
order to illustrate the applicability of this approach, we show the results of the algorithm applied to experimental data
from a population of 64 electrochemical oscillators. 相似文献
103.
104.
105.
F. Seiffert R. Schwengner G. Winter L. Funke W. Lieberz R. Reinhardt K. P. Schmittgen D. Weil R. Wrzal K. O. Zell P. von Brentano 《Zeitschrift für Physik A Hadrons and Nuclei》1991,340(2):141-153
Excited states of73Se have been investigated up to spin, 21/2 using techniques of in-beamγ-ray spectroscopy in connection with the70Ge(α, n) reaction. Mean lifetimes of 12 levels have been determined applying Doppler-shift andγ-RF-methods. Five different bands have been identified that reflect a variety of different excitation modes. The decoupled 9/2+ band is likely to correspond to an oblate deformation while the 5/2+ band is interpreted as a strongly coupled prolate band built on the Nilsson configuration [422] 5/2+. The 3/2? band is a strongly coupled band built on the [301] 3/2} configuration.Nuclear reactions:70Ge(α,n),E=14, 16, 18, 19, 20MeV; measuredE γ,I γ,σ(E γ,θ),γγ-coin, linear polarization, DSA,γ(t).75Se deduced levels,I, π, τ, δ(E2/M1), B(σλ). Enriched targets, Ge detectors. 相似文献
106.
The determination of doxazosin by high-performance liquid chromatography with fluorescence detection is described. Propanolol was used as the internal standard. Plasma samples were treated with methanol to precipitate the proteins. Doxazosin was isolated with C18 reversed-phase extraction columns. The determination limit is 1 ng/ml of plasma, while the extraction columns can be reused frequently. The method is applied to clinical trial samples. 相似文献
107.
108.
Electron energy distribution functions (eedf) in CO2 laser discharge (He—CO2—N2—CO mixture) have been calculated by solving the Boltzmann equation in the presence of given concentrations of excited (vibrational and electronic) states. The results show a well structured eedf as a result of second kind collisions coming from metastable electronic states of N2 and He as well as a strong dependence of rate coefficients for CO2 dissociation and for the ionization of the different species. 相似文献
109.
110.
T Christensen E B Jensen F Junker H Dalb?ge F Abildgaard J J Led 《Acta chemica Scandinavica (Copenhagen, Denmark : 1989)》1992,46(1):97-99
Biosynthetic human growth hormone specifically 13C-labelled in the carbonyl positions of all 26 leucine residues has been obtained by recombinant DNA techniques using 13C-labelled leucine and an E. coli strain that requires leucine. It is shown that, on the whole, the labelling is specific with no significant mislabelling as would have been the case had the 13C-labelled leucine been metabolized. 相似文献