全文获取类型
收费全文 | 353864篇 |
免费 | 2481篇 |
国内免费 | 995篇 |
专业分类
化学 | 159034篇 |
晶体学 | 5223篇 |
力学 | 19569篇 |
综合类 | 4篇 |
数学 | 68814篇 |
物理学 | 104696篇 |
出版年
2018年 | 18362篇 |
2017年 | 19006篇 |
2016年 | 11043篇 |
2015年 | 3258篇 |
2014年 | 2786篇 |
2013年 | 8234篇 |
2012年 | 12269篇 |
2011年 | 26814篇 |
2010年 | 15970篇 |
2009年 | 16339篇 |
2008年 | 21589篇 |
2007年 | 26744篇 |
2006年 | 6307篇 |
2005年 | 13630篇 |
2004年 | 9795篇 |
2003年 | 9457篇 |
2002年 | 6536篇 |
2001年 | 6150篇 |
2000年 | 4937篇 |
1999年 | 3689篇 |
1998年 | 2963篇 |
1997年 | 2922篇 |
1996年 | 3030篇 |
1995年 | 2714篇 |
1994年 | 2542篇 |
1993年 | 2447篇 |
1992年 | 2897篇 |
1991年 | 2790篇 |
1990年 | 2731篇 |
1989年 | 2767篇 |
1988年 | 2721篇 |
1987年 | 2722篇 |
1986年 | 2532篇 |
1985年 | 3392篇 |
1984年 | 3420篇 |
1983年 | 2851篇 |
1982年 | 3044篇 |
1981年 | 2969篇 |
1980年 | 2882篇 |
1979年 | 3038篇 |
1978年 | 3286篇 |
1977年 | 3019篇 |
1976年 | 2971篇 |
1975年 | 2819篇 |
1974年 | 2762篇 |
1973年 | 2814篇 |
1972年 | 1808篇 |
1968年 | 2036篇 |
1967年 | 2175篇 |
1966年 | 1982篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
L. A. Bityutskaya V. V. Distler V. V. Kryachko M. A. Yudovskaya M. V. Grechkina E. V. Bogatikov 《Physics of the Solid State》2007,49(7):1382-1386
Nanostructuring of natural isoferroplatinum crystals is revealed by atomic-force microscopy for the first time. Typical scales of ~30, 50, and 100 nm are determined and the self-affine character of their relation is established using a wavelet analysis. 相似文献
982.
The surface of polystyrene was modified with the bovine serum albumin-Tween 80 complex. The adsorption of the complex and the formation of films on the surface of polystyrene were studied using the piezoelectric weighing method. The state of the modified surface was evaluated by contact angle measurements. The stability of the modifying layer was determined based on the critical interfacial energy values of the surface equilibrated with water. A conclusion was drawn that the complex can be effectively used to enhance the biocompatibility of polymer materials. 相似文献
983.
C. von Borczyskowski F. Cichos J. Martin J. Schuster A. Issac J. Brabandt 《The European physical journal. Special topics》2007,144(1):13-25
Optical spectroscopy in combination with wide field or confocal optical
microscopy enables the investigation of single quantum objects such as
organic molecules, II/VI semiconductor quantum dots and silicon nanocrystals.
They all have fluctuations of luminescence intensities on time scales longer
than μs in common. A comparison reveals that despite the large differences
of the nature of the respective quantum objects, the intensity fluctuations
are related to a slow ionisation process followed
by a trapping of the photoejected charge in the non-conducing environment.
Detailed aspects of the dynamics are controlled by the dielectric properties
of the matrix. 相似文献
984.
Raman scattering in glasses is investigated theoretically. The experimental Raman spectra of glasses exhibit a low-frequency peak (at ~10 cm?1) that, as a rule, is attributed to vibrational modes of nanometer-sized structural units (nanocrystallites). It is established that the elastic moduli of nanocrystallites must necessarily be dependent on their sizes due to the Laplace pressure effect. A theory of the low-frequency peak is constructed using a realistic size distribution function of nanocrystallites with allowance made for the Laplace pressure effect and the dissipation of vibrational energy. Within this theory, the shape of the low-frequency peak and its evolution with temperature can be analyzed quantitatively. The proposed approach offers a physical interpretation of the experimental data and provides insight into the relation of the characteristic nanocrystallite sizes to the elastic moduli and surface tension coefficients of materials. 相似文献
985.
986.
Explosion-produced plasma jets formed in free spece are experimentally investigated. The feasibility of emitting pulsed electromagnetic signals by plasma jets is shown, and the emitting conditions are studied. Comparison is made between the results of experiments with short and long plasma jets. When the jet passes through the field of a helix, a short-term increase in the emitted signal is detected. A linear parametric model of interaction between the plasma jet and an exciting electromagnetic signal is proposed. The operating performance of instrumentation developed for the investigation is presented. 相似文献
987.
Qing Shi Dong Yang Yanlei Su Jian Li Zhongyi Jiang Yanjun Jiang Weikang Yuan 《Journal of nanoparticle research》2007,9(6):1205-1210
Lipase from Candida rugosa was covalently anchored onto acid-treated multi-walled carbon nanotubes (MWNTs) through a self-catalytic mechanism. A variety
of characterization techniques including FTIR, Raman spectroscopy, and XPS were employed to demonstrate the formation of the
ester linkage between lipase and MWNTs. The MWNTs-lipase biocomposites showed significantly increased solubility in some common-used
organic solvents, such as THF, DMF and chloroform. This study may offer a novel and facile route for covalent modification
of carbon nanotubes, and expand the potential utilization of both lipases and MWNTs in the fields of biocatalyst and biosensor. 相似文献
988.
E. de A. Gonçalves V. M. de Oliveira A. Rosas P. R.A. Campos 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(1):127-132
Adaptation of populations takes place with the occurrence and subsequent fixation of mutations that confer some selective
advantage
to the individuals which acquire it. For this reason, the study of the process of fixation of advantageous mutations has a
long history
in the population genetics literature. Particularly, the previous investigations aimed to find out the main evolutionary forces
affecting the strength of natural selection in the populations.
In the current work, we investigate the dynamics of fixation of beneficial mutations in a subdivided population. The subpopulations
(demes)
can exchange migrants
among their neighbors, in a migration network which is assumed to have either a random graph or a scale-free topology. We
have observed that the migration rate
drastically affects the dynamics of mutation fixation, despite of the fact that the probability of fixation is invariant on
the
migration rate, accordingly to
Maruyama's conjecture. In addition, we have noticed a topological dependence of the adaptive evolution of the population when
clonal interference
becomes effective. 相似文献
989.
A. Vukics H. Ritsch 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(3):585-599
We present a framework for efficiently performing Monte Carlo
wave-function simulations in cavity QED with moving particles. It
relies heavily on the object-oriented programming paradigm as realised
in C++, and is extensible and applicable for simulating open
interacting qua
ntum dynamics in general. The user is provided with a
number of “elements”, e.g. pumped moving particles, pumped lossy
cavity modes, and various interactions to compose complex interacting
systems, which contain several particles moving in electromagnetic
fields of various configurations, and perform wave-function
simulations on such systems. A number of tools are provided to
facilitate the implementation of new elements. 相似文献
990.
Numerical studies were conducted to investigate the natural convection heat transfer around a uniformly heated thin plate
with arbitrary inclination in an infinite space. The numerical approach was based on the finite volume technique with a nonstaggered
grid arrangement. For handling the pressure–velocity coupling the SIMPLE-algorithm was used. QUICK scheme and first order
upwind scheme were employed for discretization of the momentum and energy convective terms respectively. Plate width and heating
rate were used to vary the modified Rayleigh number over the range of 4.8×106 to 1.87×108. Local and average heat transfer characteristics were compared with regarding to the inclination angle. The empirical expressions
for local and average Nusselt number were correlated. It has been found that for inclination angle less than 10∘, the flow and heat transfer characteristics are complicated and the average Nusselt number can not be correlated by one equation
while for inclination angle larger than 10∘, the average Nusselt number can be correlated into an elegant correlation.
Received on 18 April 2001 / Published online: 29 November 2001 相似文献