全文获取类型
收费全文 | 840篇 |
免费 | 69篇 |
国内免费 | 56篇 |
专业分类
化学 | 516篇 |
晶体学 | 7篇 |
力学 | 27篇 |
综合类 | 5篇 |
数学 | 172篇 |
物理学 | 238篇 |
出版年
2023年 | 8篇 |
2022年 | 11篇 |
2021年 | 16篇 |
2020年 | 14篇 |
2019年 | 16篇 |
2018年 | 17篇 |
2017年 | 13篇 |
2016年 | 28篇 |
2015年 | 31篇 |
2014年 | 28篇 |
2013年 | 45篇 |
2012年 | 56篇 |
2011年 | 59篇 |
2010年 | 35篇 |
2009年 | 38篇 |
2008年 | 45篇 |
2007年 | 57篇 |
2006年 | 31篇 |
2005年 | 47篇 |
2004年 | 30篇 |
2003年 | 46篇 |
2002年 | 37篇 |
2001年 | 30篇 |
2000年 | 33篇 |
1999年 | 17篇 |
1998年 | 19篇 |
1997年 | 12篇 |
1996年 | 9篇 |
1995年 | 9篇 |
1994年 | 13篇 |
1993年 | 14篇 |
1992年 | 8篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 8篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 10篇 |
1984年 | 5篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1972年 | 2篇 |
1942年 | 3篇 |
1928年 | 2篇 |
排序方式: 共有965条查询结果,搜索用时 62 毫秒
31.
Ramón Herrera Eugenio San Martin 《The European Physical Journal C - Particles and Fields》2011,71(7):1701
Warm-intermediate inflationary universe models in the context of braneworld cosmologies are studied. This study is done in
the weak and strong dissipative regimes. We find that the scalar potentials and dissipation coefficients in terms of the scalar
field evolve as type-power-law and powers of logarithms, respectively. General conditions required for these models to be
realizable are derived and discussed. We also study the scalar and tensor perturbations for each regime. We use recent astronomical
observations to constrain the parameters appearing in the braneworld models. 相似文献
32.
Seong Yong Yoon Hoo San LeeSok Hyun Kong Hoon Sang Oh 《Journal of magnetism and magnetic materials》2007
We studied the magnetic and noise properties with various soft underlayer (SUL) types. For an as-deposited SUL, the results of spectrum, oscilloscope waveform and MFM indicated that the SUL types with IrMn pinning layer have more noise level than that of SUL types without IrMn pinning layer. And, after magnetic filed annealing along radial direction of disk, the exchange bias field increased and the noise level of type B (exchange bias type) decreased. These results reveal that incomplete or partial coupling may be generated at the interface between IrMn and ferromagnetic layer in as-deposited SUL. This incomplete coupling may result in complex or multidomain patterns in ferromagnetic layer. 相似文献
33.
The operator formalism (Fokker-Planck dynamics) associated to a general n-dimensional, non-linear drift, non-constant diffusion Fokker-Planck equation, is derived by a stochastic quantization from the corresponding path integral formulation in phase space. 相似文献
34.
A class of non-linear Fokker Planck equations with exactly known steady state solution is investigated and its relation with the models considered earlier in the literature is discussed. A characterisation of the absence of detailed balance and possible existence of limit cycles is given. The implications of detailed balance on the existence and the character of limit cycle behaviour are studied. It is shown that detailed balance does not determine the existence or non-existence of limit cycles but rather their character. 相似文献
35.
A rank-three condition for invariant (1, 2)-symplectic almost Hermitian structures on flag manifolds
Nir Cohen Caio J.C. Negreiros Luiz A.B. San Martin 《Bulletin of the Brazilian Mathematical Society》2002,33(1):49-73
This paper considers invariant (1, 2)-symplectic almost Hermitian structures on the maximal flag manifod associated to a
complex semi-simple Lie group G. The concept of cone-free invariant almost complex structure is introduced. It involves the rank-three subgroups of G, and generalizes the cone-free property for tournaments related to 𝕊l (n,ℂ) case. It is proved that the cone-free property is necessary for an invariant almost-complex structure to take part in
an invariant (1, 2)-symplectic almost Hermitian structure. It is also sufficient if the Lie group is not B
l , l ≥ 3, G
2 or F
4. For B
l and F
4 a close condition turns out to be sufficient.
Received: 28 October 2001 相似文献
36.
Five solid complexes of zinc with L‐α‐methionine, L‐α‐phenylalanine and L‐α‐histidine were prepared. The constant‐volume combustion energies of the complexes, ΔEc (coordination), were determined by a precise rotating bomb calorimeter at 298.15 K. They were ‐ 2969.03 ± 0.34, ‐2929.46 ± 1.59, ‐9597.13 ± 6.12, ‐4378.98 ± 3.27 and ‐14047 ± 6.75 kJ/mol, respectively. Their standard enthalpies of combustion, ΔHθm,c(coordination, s, 298.15 K), and standard enthalpies of formation, ΔHθm,f (coordination, s, 298.15 K), were calculated. They were ‐2959.73 ± 0.34, ‐2923.88 ± 1.59, ‐9649.18 ± 6.12, ‐4373.40 ± 3.27, ‐14048.53 ± 6.75 kj/mol and ‐1180.94 ± 0.92, ‐1401.26 ± 1.77, ‐2501.69 ± 6.50, ‐1381.47 ± 3.49, ‐1950.19 ± 7.65 kJ/mol, respectively. 相似文献
37.
San Miguel V Alvarez M Filevich O Etchenique R del Campo A 《Langmuir : the ACS journal of surfaces and colloids》2012,28(2):1217-1221
Photoreactive surfaces derived from a new photocleavable surface modification agent and with photosensitivity in the Vis and IR region are described. A ruthenium(II) caged aminosilane, [Ru(bpy)(2)(PMe(3))(APTS)](PF(6))(2), was synthesized and attached to silica surfaces. Light irradiation removed the cage and generated surface patterns with reactive amine groups. The photosensitivity of this compound under single (460 nm) and two-photon (900) excitation is demonstrated. Functional patterns with site-selective attachment of other molecular species are described. 相似文献
38.
Diverse existing lines for the calculation of excited states are exposed, with an emphasis on those methods that consider
both types of correlation energy: the dynamic and the non-dynamic one. We analyze the possibility of to calculate the dynamic
correlation energy using a correlation energy density functional applied to a multi-determinantal wavefunction, which would
include the non-dynamic correlation energy, versus the use of mono-determinantal wavefunctions, which are not able to include
the long-range correlation energy, and versus the use of variational or perturbative calculations from multi-determinantal
wavefunctions, with their excessive computational cost. The results obtained with several methods are compared.
Contribution to the Serafin Fraga Memorial Issue. 相似文献
39.
This paper describes the optimization of solid-phase microextraction (SPME) conditions for three different fibres (Carboxen-polydimethylsiloxane (CAR-PDMS), divinylbenzene-Carboxen-polydimethylsiloxane (DVB-CAR-PDMS) and polydimethylsiloxane-divinylbenzene (PDMS-DVB)) used to determine trihalomethanes (THMs) in water by headspace solid-phase microextraction and gas chromatography (HS-SPME-GC). The influence of temperature and salting-out effect was examined using a central composite design for each fibre. Extraction time was studied separately at the optimum values found for temperature and sodium chloride concentration (40 degrees C and 0.36g mL-1). The HS-SPME-GC-MS method for each fibre was characterised in terms of linearity, detection (LOD) and quantification (LOQ) limits and repeatability. The fibre PDMS-DVB was selected as it provided a broader linear range, better repeatability and lower detection and quantification limits than the others, particularly CAR-PDMS fibre. The accuracy of the proposed method using the PDMS-DVB fibre was checked by a recovery study in both ultrapure and tap water. A blank analysis study showed the absence of memory effects for this fibre. The reproducibility (expressed as a percentage of relative standard deviation) was 6-11% and the detection limits were between 0.078 and 0.52microgL-1 for bromoform and chloroform, respectively. Finally, the method was applied to determine THM concentration in two drinking water samples. 相似文献
40.
Alejandro Valverde Amira ben Hassine Vernica Serafín Cristina Muoz‐San Martín María Pedrero María Garranzo‐Asensio Maria Gamella Noureddine Raouafi Rodrigo Barderas Paloma Yez‐Sedeo Susana Campuzano Jos M. Pingarrn 《Electroanalysis》2020,32(4):706-714
This paper reports the development of a dual immunosensor using magnetic microcarriers (MBs) and amperometric transduction at dual screen‐printed carbon electrodes (SPdCEs) for the simultaneous determination of two biomarkers: interleukin‐13 receptor α2 (IL‐13Rα2) and E‐cadherin (E‐CDH), with both extracellular and soluble fraction; oncogenic and tumor suppressor markers, respectively, of great relevance in metastatic processes. The implemented methodology involved the formation of sandwich‐type immunocomplexes using specific capture antibodies immobilized onto carboxylic acid magnetic microbeads (HOOC‐MBs), and biotinylated detector antibodies labeled with streptavidin?horseradish peroxidase conjugates (Strep‐HRP). The amperometric detection was performed by addition of hydrogen peroxide in the presence of hydroquinone (HQ) as the redox mediator. The dual immunosensing platform provided linear calibration ranges suitable for the determination of both biomarkers in liquid and solid clinical specimens as well as excellent selectivity against other cancer biomarkers. This simple handling dual bioplatform was applied to the determination of the soluble and extracellular fraction of the target biomarkers in serum and paraffined‐embedded tissues from colorectal cancer (CRC) patients diagnosed at different tumor grade. The obtained results reveal great potential of this configuration to improve the reliability in diagnosing metastatic CRC. 相似文献