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991.
A vertex detector concept of the linear collider flavour identification (LCFI) collaboration, which studies pixel detectors
for heavy quark flavour identification, has been implemented in simulations for c-quark tagging in scalar top studies. The production and decay of scalar top quarks (stops) is particularly interesting for
the development of the vertex detector as only two c-quarks and missing energy (from undetected neutralinos) are produced for light stops. Previous studies investigated the vertex
detector design in scenarios with large mass differences between stop and neutralino, corresponding to large visible energy
in the detector. In this study we investigate the tagging performance dependence on the vertex detector design in a scenario
with small visible energy for the international linear collider (ILC).
相似文献
992.
M. Darwish 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(3):547-556
Theoretical investigations of dynamical behavior in optical
parametric oscillators (OPO) have generally assumed that the cavity
detunings of the interacting fields are controllable parameters.
However, OPOs are known to experience mode hops, where the system
jumps to the mode of lowest cavity detuning. We note that this
phenomenon significantly limits the range of accessible detunings
and thus may prevent instabilities predicted to occur above a
minimum detuning from being evidenced experimentally. As a simple
example among a number of instability mechanisms possibly affected
by this limitation, we discuss the Hopf bifurcation leading to
periodic behavior in the monomode mean-field model of a triply
resonant OPO and show that it probably can be observed only in very
specific setups. 相似文献
993.
Milind Kandlikar Gurumurthy Ramachandran Andrew Maynard Barbara Murdock William A. Toscano 《Journal of nanoparticle research》2007,9(1):137-156
Uncertainties in conventional quantitative risk assessment typically relate to values of parameters in risk models. For many
environmental contaminants, there is a lack of sufficient information about multiple components of the risk assessment framework.
In such cases, the use of default assumptions and extrapolations to fill in the data gaps is a common practice. Nanoparticle
risks, however, pose a new form of risk assessment challenge. Besides a lack of data, there is deep scientific uncertainty
regarding every aspect of the risk assessment framework: (a) particle characteristics that may affect toxicity; (b) their
fate and transport through the environment; (c) the routes of exposure and the metrics by which exposure ought to be measured;
(d) the mechanisms of translocation to different parts of the body; and (e) the mechanisms of toxicity and disease. In each
of these areas, there are multiple and competing models and hypotheses. These are not merely parametric uncertainties but
uncertainties about the choice of the causal mechanisms themselves and the proper model variables to be used, i.e., structural
uncertainties. While these uncertainties exist for PM2.5 as well, risk assessment for PM2.5 has avoided dealing with these
issues because of a plethora of epidemiological studies. However, such studies don’t exist for the case of nanoparticles.
Even if such studies are done in the future, they will be very specific to a particular type of engineered nanoparticle and
not generalizable to other nanoparticles. Therefore, risk assessment for nanoparticles will have to deal with the various
uncertainties that were avoided in the case of PM2.5. Consequently, uncertainties in estimating risks due to nanoparticle
exposures may be characterized as ‘extreme’. This paper proposes a methodology by which risk analysts can cope with such extreme
uncertainty. One way to make these problems analytically tractable is to use expert judgment approaches to study the degree
of consensus and/or disagreement between experts on different parts of the exposure–response paradigm. This can be done by
eliciting judgments from a wide range of experts on different parts of the risk causal chain. We also use examples to illustrate
how studying expert consensus/disagreement helps in research prioritization and budget allocation exercises. The expert elicitation
can be repeated over the course of several years, over which time, the state of scientific knowledge will also improve and
uncertainties may possibly reduce. Results from expert the elicitation exercise can be used by risk managers or managers of
funding agencies as a tool for research prioritization. 相似文献
994.
利用数学软件Mathematica 5.2的三维参数作图法,用计算机画出了双轴晶体中光的波面的立体形象,并说明了它的一些特征. 相似文献
995.
基于动量守恒和光参变过程中的三波耦合波方程,和负单轴非线性光学晶体CsLiB6O10的色散方程,研究了在光参变效应中超短激光脉冲由于群速度色散引起的展宽和形变。数值模拟显示,在超短脉冲波形为双曲正割形和无啁啾调制时,高阶群速度色散引起的超短脉冲为50fs时,晶体长度为10mm,紫外光213nm作为基波入射时的脉冲展宽是波长为532nm绿光在同等条件下的1.6倍。脉冲展宽程度与入射波长和晶体长度有关,波长越短和晶体长度越长则脉冲展宽和波形变化越严重,高阶色散引起的超短高斯脉冲展宽,将破坏其波形对称性并引起旁瓣现象。 相似文献
996.
Antoine Berrou Jean-Michel Melkonian Myriam Raybaut Antoine Godard Emmanuel Rosencher Michel Lefebvre 《Comptes Rendus Physique》2007,8(10):1162-1173
Optical parametric oscillators are coherent light sources showing properties that are not encountered with usual laser sources. This article deals with optical architectures that take advantage of the specific properties of the three-wave mixing parametric interaction. We show that optical cavities can be specifically designed to increase either the optical conversion of the parametric process or to reduce dramatically the emitted line width. To cite this article: A. Berrou et al., C. R. Physique 8 (2007). 相似文献
997.
It is demonstrated experimentally that the anharmonic property of the quadrupole trap can be exploited to cool trapped atoms by modulating the trap potential anisotropically.This cooling effect arises from the energy-selective removal of the most energetic trapped atoms and the thermal equilibrium of the remaining atoms.The frequency dependences of the temperature and the fraction of the atoms left in the trap after the modulation are explored.It is also demonstrated that the cooling induced by parametric resonance can also increase the phase space density of the trapped atoms. 相似文献
998.
Exponential synchronization of stochastic impulsive perturbed chaotic Lur''e systems with time-varying delay and parametric uncertainty 下载免费PDF全文
This paper is devoted to investigating the scheme of exponential synchronization for uncertain stochastic impulsive perturbed chaotic Lur'e systems. The parametric uncertainty is assumed to be norm bounded. Based on the Lyapunov function method, time-varying delay feedback control technique and a modified Halanay inequality for stochastic differential equations, several sufficient conditions are presented to guarantee the exponential synchronization in mean square between two identical uncertain chaotic Lur'e systems with stochastic and impulsive perturbations. These conditions are expressed in terms of linear matrix inequalities (LMIs), which can easily be checked by utilizing the numerically efficient Matlab LMI toolbox. It is worth pointing out that the approach developed in this paper can provide a more general framework for the synchronization of multi-perturbation chaotic Lur'e systems, which reflects a more realistic dynamics. Finally, a numerical example is provided to demonstrate the effectiveness of the proposed method. 相似文献
999.
1000.
A CW seeded femtosecond optical parametric amplifier, a compromise between OPG/OPA and strongly seeded OPA configurations,
has been demonstrated. An independent CW Nd: YAG laser with sub-watt power decreases the pump threshold of the OPA and improves
the stability of the output pulses considerably. Output signal energies as high as 30 μJ with pulse durations less than 250
fs near 1 μm are reported. from this two-stage device. 相似文献