全文获取类型
收费全文 | 32732篇 |
免费 | 140篇 |
国内免费 | 271篇 |
专业分类
化学 | 13170篇 |
晶体学 | 283篇 |
力学 | 1404篇 |
综合类 | 12篇 |
数学 | 9236篇 |
物理学 | 9038篇 |
出版年
2021年 | 61篇 |
2020年 | 63篇 |
2019年 | 50篇 |
2018年 | 1269篇 |
2017年 | 1546篇 |
2016年 | 850篇 |
2015年 | 643篇 |
2014年 | 578篇 |
2013年 | 842篇 |
2012年 | 3304篇 |
2011年 | 2635篇 |
2010年 | 1968篇 |
2009年 | 1664篇 |
2008年 | 835篇 |
2007年 | 872篇 |
2006年 | 853篇 |
2005年 | 4644篇 |
2004年 | 4071篇 |
2003年 | 2429篇 |
2002年 | 591篇 |
2001年 | 370篇 |
2000年 | 196篇 |
1999年 | 235篇 |
1998年 | 165篇 |
1997年 | 119篇 |
1996年 | 81篇 |
1995年 | 63篇 |
1994年 | 74篇 |
1993年 | 42篇 |
1992年 | 191篇 |
1991年 | 174篇 |
1990年 | 153篇 |
1989年 | 123篇 |
1988年 | 123篇 |
1987年 | 71篇 |
1986年 | 59篇 |
1985年 | 59篇 |
1984年 | 41篇 |
1983年 | 44篇 |
1979年 | 46篇 |
1976年 | 93篇 |
1975年 | 47篇 |
1974年 | 57篇 |
1973年 | 56篇 |
1972年 | 51篇 |
1970年 | 43篇 |
1969年 | 48篇 |
1968年 | 42篇 |
1967年 | 41篇 |
1966年 | 47篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
JETP Letters - Extraordinary multiparticle effects in quantizing magnetic fields that are manifested in strongly interacting two-dimensional electron systems in MgZnO/ZnO heterostructures have been... 相似文献
2.
Watanabe Sou Senzaki Tatsuya Shibata Atsuhiro Nomura Kazunori Takeuchi Masayuki Nakatani Kiyoharu Matsuura Haruaki Horiuchi Yusuke Arai Tsuyoshi 《Journal of Radioanalytical and Nuclear Chemistry》2019,322(3):1273-1277
Journal of Radioanalytical and Nuclear Chemistry - Extraction chromatography flow-sheet employing octyl(phenyl)-N,N-diisobutylcarbonoylmethylphosphine oxide and bis(2-ethylhexyl) hydrogen phosphate... 相似文献
3.
Nováková Kateřina Hrdlička Vojtěch Navrátil Tomáš Vyskočil Vlastimil Barek Jiří 《Monatshefte für Chemie / Chemical Monthly》2015,146(5):761-769
Monatshefte für Chemie - Chemical Monthly - The voltammetric behavior of 5-nitroindazole was investigated at polished (p-AgSAE) and at mercury meniscus-modified (m-AgSAE) silver solid amalgam... 相似文献
4.
Julia K Pruns Jens-Peter Vietzke Manfred Strassner Claudius Rapp Ulrich Hintze Wilfried A K?nig 《Rapid communications in mass spectrometry : RCM》2002,16(3):208-211
A new solvent-free sample preparation method using silver trifluoroacetate (AgTFA) was developed for the analysis of low molecular weight paraffins and microcrystalline waxes by laser desorption/ionization time-of-flight mass spectrometry (LDI-TOFMS). Experiments show that spectral quality can be enhanced by dispersing AgTFA directly in liquid paraffins without the use of additional solvents. This preparation mixture is applied directly to the MALDI probe. Solid waxes could be examined by melting prior to analysis. The method also provides sufficiently reproducible spectra that peak area ratios between mono- and bicyclic alkane peaks indicated variations in the cycloalkane content of paraffin samples. Dehydrogenation of hydrocarbons observed during the desorption/ionization process was studied by analysis of alkane standards. 相似文献
5.
The versatile behavior of a trihydrazidophosphoradamantane allowing the synthesis of a variety of neutral, mono- or di-cationic water-soluble molecules of potential interest for biphasic catalysis is reported. 相似文献
6.
In this paper we construct an example of a word metric on an infinite cyclic subgroup. This example shows that subexponential
distortion does not obstruct non-trivial growth of connected radii. This answers a question of Gromov [6]. The constructed
metric has other pathological properies. Specifically, its asymptotic cone depends on the choice of ultrafilter and scaling
sequence.
The work has been partially supported by the Swiss National Science Foundation. 相似文献
7.
We build a metric space which is homeomorphic to a Cantor set but cannot be realized as the attractor of an iterated function system. We give also an example of a Cantor set K in R3 such that every homeomorphism f of R3 which preserves K coincides with the identity on K. 相似文献
8.
Milan Medved? 《Journal of Mathematical Analysis and Applications》2002,267(2):643-650
A criterion for the nonexplosion of solutions to semilinear evolution equations on Banach spaces is proved. The result is obtained by applying a modification of the Bihari type inequality to the case of a weakly singular nonlinear integral inequality. 相似文献
9.
M. Uleysky L. Konkov S. Prants 《Communications in Nonlinear Science & Numerical Simulation》2003,8(3-4):329
We study the coupled translational, electronic, and field dynamics of the combined system “a two-level atom + a single-mode quantized field + a standing-wave ideal cavity”. In the semiclassical approximation with a point-like atom, interacting with the classical field, the dynamics is described by the Heisenberg equations for the atomic and field expectation values which are known to produce semiclassical chaos under appropriate conditions. We derive Hamilton–Schrödinger equations for probability amplitudes and averaged position and momentum of a point-like atom interacting with the quantized field in a standing-wave cavity. They constitute, in general, an infinite-dimensional set of equations with an infinite number of integrals of motion which may be reduced to a dynamical system with four degrees of freedom if the quantized field is supposed to be initially prepared in a Fock state. This system is found to produce semiquantum chaos with positive values of the maximal Lyapunov exponent. At exact resonance, the semiquantum dynamics is regular. At large values of detuning |δ|1, the Rabi atomic oscillations are usually shallow, and the dynamics is found to be almost regular. The Doppler–Rabi resonance, deep Rabi oscillations that may occur at any large value of |δ| to be equal to |αp0|, is found numerically and described analytically (with α to be the normalized recoil frequency and p0 the initial atomic momentum). Two gedanken experiments are proposed to detect manifestations of semiquantum chaos in real experiments. It is shown that in the chaotic regime values of the population inversion zout, measured with atoms after transversing a cavity, are so sensitive to small changes in the initial inversion zin that the probability of detecting any value of zout in the admissible interval [−1,1] becomes almost unity in a short time. Chaotic wandering of a two-level atom in a quantized Fock field is shown to be fractal. Fractal-like structures, typical with chaotic scattering, are numerically found in the dependence of the time of exit of atoms from the cavity on their initial momenta. 相似文献
10.
We consider the one-dimensional steady-state semiconductor deviceequations modelling a pnpn device. There are two relevant scalingsof the equations corresponding to small and large applied voltages.In both scalings, the semiconductor equations can be consideredas singularly perturbed. It turns out that the small-voltagescaling breaks down for current values between two saturationcurrents. In that interval, the large-voltage scaling has tobe employed. For both scalings, we derive the first-order termsof an asymptotic expansion and show that the reduced problemhas a solution. An example verifies that the current-voltagecurves obtained have the expected qualitative structure. 相似文献