全文获取类型
收费全文 | 87412篇 |
免费 | 1157篇 |
国内免费 | 1211篇 |
专业分类
化学 | 31479篇 |
晶体学 | 891篇 |
力学 | 6966篇 |
综合类 | 66篇 |
数学 | 33443篇 |
物理学 | 16935篇 |
出版年
2023年 | 114篇 |
2022年 | 251篇 |
2021年 | 314篇 |
2020年 | 334篇 |
2019年 | 307篇 |
2018年 | 10613篇 |
2017年 | 10442篇 |
2016年 | 6474篇 |
2015年 | 1268篇 |
2014年 | 782篇 |
2013年 | 1006篇 |
2012年 | 4639篇 |
2011年 | 11370篇 |
2010年 | 6265篇 |
2009年 | 6585篇 |
2008年 | 7289篇 |
2007年 | 9412篇 |
2006年 | 856篇 |
2005年 | 1823篇 |
2004年 | 1986篇 |
2003年 | 2248篇 |
2002年 | 1252篇 |
2001年 | 371篇 |
2000年 | 398篇 |
1999年 | 268篇 |
1998年 | 258篇 |
1997年 | 212篇 |
1996年 | 262篇 |
1995年 | 164篇 |
1994年 | 114篇 |
1993年 | 133篇 |
1992年 | 89篇 |
1991年 | 91篇 |
1990年 | 85篇 |
1989年 | 81篇 |
1988年 | 76篇 |
1987年 | 81篇 |
1986年 | 73篇 |
1985年 | 74篇 |
1984年 | 62篇 |
1983年 | 49篇 |
1982年 | 49篇 |
1981年 | 45篇 |
1980年 | 59篇 |
1979年 | 53篇 |
1978年 | 42篇 |
1914年 | 45篇 |
1912年 | 41篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
We apply the recently improved version of the 0–1 test for chaos to real experimental time series of laser droplet generation
process. In particular two marginal regimes of dripping are considered: spontaneous and forced dripping. The outcomes of the
test reveal that both spontaneous and forced dripping time series can be characterized as chaotic, which coincides with the
previous analysis based on nonlinear time series analysis. 相似文献
962.
Ahmad Seif Ehsan Zahedi Goodarz M. Rozbahani 《Central European Journal of Chemistry》2012,10(1):96-104
To investigate the influence of C-doping on the electrostatic structure properties in the frame work of density functional
theory (DFT), we considered beryllium monoxide nanotubes (BeONTs), consisting of 60 Be and 60 O atoms. Full geometry optimizations
are performed for all structures, i.e., all atoms are allowed to relax. Afterwards, the chemical shielding (CS) tensors are
calculated for Be-9, O-17 and C-13 nuclei in the C-doped forms and also pristine models of the (10, 0) zigzag and (5, 5) armchair
BeONTs. Formation energies indicate that C-doping of Be atom (CBe form) could be more favorable than C-doping of O atom (CO
form) in both zigzag and armchair BeONTs. Gap energies and dipole moments detected the effects of dopant in the (5, 5) armchair
models; however, those parameters did not indicate any significant changes in the C-doped (10, 0) zigzag BeONT models. The
results show that the CS values for the Be and O atoms-contributed to the Be-C bonds or those atoms close to the C-doped region-in
the CO form of BeONTs (zigzag and armchair) are changed. The same values only for the O atoms-contributed to the O-C bonds-
in the CBe form of BeONTs (zigzag and armchair) are changed. 相似文献
963.
Using a cosmological black hole model proposed recently, we have calculated the quasi-local mass of a collapsing structure
within a cosmological setting due to different definitions put forward in the last decades to see how similar or different
they are. It has been shown that the mass within the horizon follows the familiar Brown–York behavior. It increases, however,
outside the horizon again after a short decrease, in contrast to the Schwarzschild case. Further away, near the void, outside
the collapsed region, and where the density reaches the background minimum, all the mass definitions roughly coincide. They
differ, however, substantially far from it. Generically, we are faced with three different Brown–York mass maxima: near the
horizon, around the void between the overdensity region and the background, and another at cosmological distances corresponding
to the cosmological horizon. While the latter two maxima are always present, the horizon mass maxima is absent before the
onset of the central singularity. 相似文献
964.
965.
Przemysław Koźmiński Ewa Gniazdowska Leon Fuks Agata Oszczak 《Journal of Radioanalytical and Nuclear Chemistry》2012,292(1):67-74
Easy and efficient way to modify of the C-terminus of the peptide using amino acid lysine has been proposed and experimentally
verified. The synthesis yield was high (≥85%) and it was found that reactions can be carried out even with microgram amounts
of the peptide. Using Fmoc-alanine (as the peptide model) with modified C-terminus the procedure of peptide labelling with
monovalent and trivalent 99mTc complexes has been elaborated. 相似文献
966.
Vladimir Petukhov John Stoemenos Johan Rothman Andrey Bakin Andreas Waag 《Applied Physics A: Materials Science & Processing》2011,102(1):161-168
In order to interpret results of temperature dependent Hall measurements in heteroepitaxial ZnO-thin films, we adopted a multilayer
conductivity model considering carrier-transport through the interfacial layer with degenerate electron gas as well as the
upper part of ZnO layers with lower conductivity. This model was applied to the temperature dependence of the carrier concentration
and mobility measured by Hall effect in a ZnO-layer grown on c-sapphire with conventional high-temperature MgO and low-temperature
ZnO buffer. We also compared our results with the results of maximum entropy mobility-spectrum analysis (MEMSA). The formation
of the highly conductive interfacial layer was explained by analysis of transmission electron microscopy (TEM) images taken
from similar layers. 相似文献
967.
Carlyle T. B. Menezes Erilson C. Barros Raquel D. Rufino Juliana M. Luna Leonie A. Sarubbo 《Applied biochemistry and biotechnology》2011,163(4):540-546
Dissolved air flotation (DAF) is a well-established separation process employing micro bubbles as a carrier phase. The application
of this technique in the treatment of acid mine drainage, using three yeast biosurfactants as alternative collectors, is hereby
analyzed. Batch studies were carried out in a 50-cm high acrylic column with an external diameter of 2.5 cm. High percentages
(above 94%) of heavy metals Fe(III) and Mn(II) were removed by the biosurfactants isolated from Candida lipolytica and Candida sphaerica and the values were found to be similar to those obtained with the use of the synthetic sodium oleate surfactant. The DAF
operation with both surfactant and biosurfactants, achieved acceptable turbidity values, in accordance with Brazilian standard
limits. The best ones were obtained by the biosurfactant from C. lipolytica, which reached 4.8 NTU. The results obtained with a laboratory synthetic effluent were also satisfactory. The biosurfactants
removed almost the same percentages of iron, while the removal percentages of manganese were slightly higher compared with
those obtained in the acid mine drainage effluent. They showed that the use of low-cost biosurfactants as collectors in the
DAF process is a promising technology for the mining industries. 相似文献
968.
Xiongxin Dai Sheila Kramer-Tremblay 《Journal of Radioanalytical and Nuclear Chemistry》2011,289(2):461-466
Assays of alpha- and beta-emitting radionuclides in swipe samples are often required to monitor the presence of removable
surface contamination for radiological protection and control in nuclear facilities. Swipe analysis has also proven to be
a very sensitive analytical technique to detect nuclear signatures for safeguard verification purposes. A new sequential method
for the determination of actinide isotopes and radiostrontium in swipe samples, which utilizes a streamlined column separation
with stacked anion and extraction chromatography resins, has been developed. To validate the separation procedure, spike and
blank samples were prepared and analyzed by inductively coupled mass spectrometry (ICP-MS), alpha spectrometry and liquid
scintillation (LS) counting. Low detection limits have been achieved for isotopic analysis of Pu (238Pu, 239Pu, 240Pu, 241Pu), U (234U, 235U, 238U), Am (241Am), Cm (242Cm, 243/244Cm) and Sr (90Sr) at ultra-trace concentration levels in swipe samples. 相似文献
969.
James Casey 《Meccanica》2011,46(2):471-476
For motion of a material point along a space curve, a kinematical decomposition, discovered by Siacci, expresses the acceleration
vector as the sum of two special oblique components in the osculating plane to the curve. A new proof of Siacci’s theorem
is presented. 相似文献
970.
Fluorescence correlation spectroscopy (FCS) of colloidal nanoparticles using a near-field fiber probe was numerically simulated.
The near-wall dynamics was simulated by accounting for the anisotropic mobility of nanoparticles owing to hydrodynamic interaction
with a wall (Stokes viscous force). By comparing the simulation results with theoretical model calculations, we found that
the influence of anisotropic diffusion is insignificant in near-field FCS autocorrelation analysis. 相似文献