全文获取类型
收费全文 | 8542篇 |
免费 | 687篇 |
国内免费 | 855篇 |
专业分类
化学 | 5490篇 |
晶体学 | 131篇 |
力学 | 412篇 |
综合类 | 69篇 |
数学 | 1290篇 |
物理学 | 2692篇 |
出版年
2023年 | 87篇 |
2022年 | 249篇 |
2021年 | 248篇 |
2020年 | 241篇 |
2019年 | 238篇 |
2018年 | 218篇 |
2017年 | 215篇 |
2016年 | 274篇 |
2015年 | 290篇 |
2014年 | 370篇 |
2013年 | 630篇 |
2012年 | 573篇 |
2011年 | 634篇 |
2010年 | 465篇 |
2009年 | 418篇 |
2008年 | 524篇 |
2007年 | 449篇 |
2006年 | 444篇 |
2005年 | 369篇 |
2004年 | 271篇 |
2003年 | 257篇 |
2002年 | 231篇 |
2001年 | 225篇 |
2000年 | 212篇 |
1999年 | 151篇 |
1998年 | 94篇 |
1997年 | 74篇 |
1996年 | 82篇 |
1995年 | 65篇 |
1994年 | 105篇 |
1993年 | 88篇 |
1992年 | 86篇 |
1991年 | 73篇 |
1990年 | 65篇 |
1989年 | 55篇 |
1988年 | 56篇 |
1987年 | 50篇 |
1986年 | 52篇 |
1985年 | 68篇 |
1984年 | 65篇 |
1983年 | 38篇 |
1982年 | 64篇 |
1981年 | 54篇 |
1980年 | 58篇 |
1979年 | 51篇 |
1978年 | 58篇 |
1977年 | 51篇 |
1976年 | 46篇 |
1975年 | 37篇 |
1973年 | 39篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
73.
E. Pinsolle D. Le Bolloc'h N. Kirova V.L.R. Jacques A.A. Shinchenko P. Monceau 《Physica B: Condensed Matter》2012,407(11):1848-1851
Experiments on the coherent X-ray diffraction, and their modeling, have been performed on the Charge Density Wave (CDW) system NbSe3. The 2kF satellite reflection associated with the CDW has been measured with respect to external dc currents. Below the threshold current, reflection displays several fringes in the transverse direction which disappear when the threshold current is exceeded. In the sliding state, the transverse satellite profile has a form of two nonsymmetric peaks, one of them being centered at the same position as below the threshold and another one being shifted. The shift of the longitudinal peak position below the threshold current and the nonsymmetric peak in the transverse direction above the threshold one is interpreted as the influence of strong linear defect like a crystal step present on the sample surface, combined with induced arrays of dislocations. Coherent X-rays provide a new access to processes in a CDW driven by an external force in a random pinning potential. 相似文献
74.
ICP-MS测定模拟全血基体中不同质量段的Mg, Cu, Pb元素,考察基体效应对测定值的影响,分别采用传统内标法和单一内标CAIS方法(common analyte internal standardization)对其进行校正和比较。结果表明CAIS方法适用于不同浓度血液基体中多种元素的同时校正,且效果良好,其相对平均误差仅为3.05%,明显低于传统内标法的12.39%和校正前的23.91%;CAIS方法不受内标元素和被测元素质量数差异、测定强度差异以及电极电位差异的限制;使用全血和血清标准物质对CAIS方法可靠性进行验证,测定值全部落在标准值范围内。 相似文献
75.
Treussart F Alléaume R Le Floc'h V Xiao LT Courty JM Roch JF 《Physical review letters》2002,89(9):093601
We studied intensity fluctuations of a single photon source relying on the pulsed excitation of the fluorescence of a single molecule at room temperature. We directly measured the Mandel parameter Q(T) over 4 orders of magnitude of observation time scale T by recording every photocount. On time scale of a few excitation periods, sub-Poissonian statistics is clearly observed and the probablility of two-photons events is 10 times smaller than Poissonian pulses. On longer times, blinking in the fluorescence, due to the molecular triplet state, produces an excess of noise. 相似文献
76.
We present a study on the fluctuations of semiflexible actin filaments using fluorescence videomicroscopy, focusing on the end-to-end fluctuations of single filaments. In order to specifically measure the position of the polymer's ends, we developed a novel noninvasive method that consists of annealing short end tags to the filaments. This allows us to probe polymer fluctuations to a very high accuracy. We compared the distribution of the end-to-end distance with recent theoretical results, and found excellent agreement. We also studied the dynamics of the mean-square end-to-end distance deltaR2(t) and orientation of the ends, deltaTheta(2)(t), finding power laws t(3/4) and t(1/4), respectively. Scaling behavior for deltaR2(t) is observed over several decades in relaxation time in agreement with theoretical results. 相似文献
77.
Badro J Fiquet G Struzhkin VV Somayazulu M Mao HK Shen G Le Bihan T 《Physical review letters》2002,89(20):205504
We present a new method to separate the crystallographic and electronic phase transitions in hematite using x-ray emission spectroscopy and x-ray diffraction. Our observations, based on the behavior of a metastable high-pressure phase in the stability domain of the low-pressure phase, show that the electronic transition is preempted by the crystallographic transition. The former occurs only afterwards in the high-pressure phase, possibly as a result of a Mott transition. The idea that the electronic transition drives the transition in hematite is therefore invalidated. Such methods should help elucidate the mechanics and the driving forces behind a number of first-order high-pressure phase transitions. 相似文献
78.
应用荧光光谱和径向基函数神经网络定量检测三聚氰胺 总被引:1,自引:0,他引:1
实验发现三聚氰胺溶液在紫外光激发下产生较强荧光,测得其荧光峰在310~600 nm之间,荧光峰值波长为420 nm左右,荧光相对强度与三聚氰胺溶液浓度呈现复杂的非线性关系。提出了采用径向基函数神经网络结合荧光光谱对三聚氰胺溶液浓度进行测定的方法。对每个样本选取30个发射波长值所对应的荧光强度作为网络数据,训练、建立了径向基函数神经网络。应用训练好的径向基函数神经网络,对5种三聚氰胺溶液的浓度进行预测,结果相对误差分别为0.93%,0.09%,0.31%,1.55%,4.61%。该方法能快捷、准确地测定三聚氰胺在溶液中的含量,为三聚氰胺检测及食品安全监管提供了一种新方法。 相似文献
79.
The α preformation factor and penetration probability
have been analyzed for even--even nuclei of Po, Rn, Ra using
experimental released energies and α decay half-lives in the
frame of the double folding model. It is shown that N=126 is a neutron
magic number from α preformation and shell effects play
an important role in α preformation. The closer the
nucleon number is to the magic number, the more difficult α
formation in the parent nucleus is. The preformation factor can
supply information on the nuclear structure and the penetration
probability mainly determines α decay half-life. 相似文献
80.
Abstract A synchrotron X-ray diffraction study on hexagonal graphite-like boron nitride (h-BN) was performed under high pressures and temperatures. From the measured P-V-Trelation for h-BN (with a three-dimensional ordering parameter P3 = 0.9) in the temperature range from 298 to 1273 K and up to 6.7 GPa, the thermoelastic parameters are derived by fitting a modified high temperature Birch-Murnaghan equation of state. The results are: bulk modulus B0[GPa] = 27.6-0.0081(T[K]-298) and its pressure derivative B1 = 10.5 + 0.0016(T [K] - 298). These values are for samples with P3 = 0.9 and are quite different for samples with different values of the order parameter. This parameter is shown to have a leading role in the determination of the thermoelastic properties of h-BN, which explains and reconciles the differences between previous results. 相似文献