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991.
One-dimensional photonic crystal structures for multiple channeled
filtering and polarization selective filtering in the terahertz
(THz) range are studied theoretically. The design of aperiodic photonic
quantum-well (APQW) structures for multiple channeled filtering and
different polarization filtering at arbitrary preassigned
frequencies are achieved by using the simulated annealing algorithm
with a special merit function. The parameters of these filters can
be expediently controlled and the transmission characters are
polarization dependent. Numerical simulations show that the designed
APQWs can meet the desired specification well. 相似文献
992.
Density and impurity profile behaviours in HL-2A tokamak with different gas fuelling methods 下载免费PDF全文
The electron density profile peaking and the impurity accumulation
in the HL-2A tokamak plasma are observed when three kinds of
fuelling methods are separately used at different fuelling particle
locations. The density profile becomes more peaked when the
line-averaged electron density approaches the Greenwald density limit
nG and, consequently, impurity accumulation is often
observed. A linear increase regime in the density range ne<
0.6nG and a saturation regime in ne > 0.6nG
are obtained. There is no significant difference in achieved density
peaking factor fne between the supersonic molecular beam
injection (SMBI) and gas puffing into the plasma main chamber.
However, the achieved fne is relatively low, in particular,
in the case of density below 0.7nG, when the working
gas is puffed into the divertor chamber. A discharge with a
density as high as 1.2nG, i.e. ne = 1.2nG,
can be achieved by SMBI just after siliconization as a wall
conditioning. The metallic impurities, such as iron and chromium,
also increase remarkably when the impurity accumulation happens. The
mechanism behind the density peaking and impurity accumulation is
studied by investigating both the density peaking factor versus the
effective collisionality and the radiation peaking versus density
peaking. 相似文献
993.
994.
James B. Gerken Claire Badger Christopher Bisbee Sasha Gardner Yan Qi Víctor Durà Vilà John D. Roberts 《Journal of Physical Organic Chemistry》2008,21(3):193-197
Conformational preferences of glutaric, 3‐hydroxyglutaric and 3‐methylglutaric acid, and their mono‐ and dianions have been investigated with the aid of NMR spectroscopy. In contrast to succinic acid, glutaric acid displays essentially statistical conformational equilibria in polar and non‐polar solutions of high and low hydrogen‐bonding ability with no clear evidence for intramolecular hydrogen‐bonding interactions. The acid ionization constant ratios, K 1/K2, in D2O and DMSO of glutaric, 3‐hydroxyglutaric, and 3‐methylglutaric acids also indicate that intramolecular interactions are much less important than, or indeed insignificant, for shorter‐chain acids. FTIR studies on 3‐methylglutaric acid indicate some preference for either association with solvent or dimerization, depending on the solvent, rather than intramolecular hydrogen bonding. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
995.
Ou Xu Shaohua Lu Yan Liu Bin Li Xiaowei Dong Li Pei Shuisheng Jian 《Optics Communications》2008,281(15-16):3990-3995
On the basis of the coupled-mode theory, a detailed investigation of the optical spectral characteristics is presented for uniform tilted fiber gratings. Explicit expressions are derived for the spectral parameters of reflection and transmission spectra. Numerical simulations are carried on to show the dependences of grating spectral responses on the structural parameters, such as tilt angle, grating length, index modulation amplitude and polarization states. The effects of these parameters on shaping the grating spectra are discussed comprehensively. The physical mechanism and intuitive phase-matching vector model are provided to explain the unique behaviors of transmission loss spectra. The results are helpful for providing a better understanding of the spectral behavior of the tilted fiber grating. 相似文献
996.
The alloys of non-centrosymmetric superconductor, Re 3 W, which were reported to have an α-Mn structure [P. Greenfield and P. A. Beck, J. Metals, N. Y. 8, 265 (1959)] with T c = 9 K, are prepared by arc melting. The values of ac susceptibility and the low-temperature specific heat of these alloys are measured. It is found that there are two superconducting phases coexisting in the samples with T c1 ≈ 9 K and T c2 ≈ 7 K, which are both non-centrosymmetric in structure as reported previously. By analysing the specific heat data measured in various magnetic fields down to a temperature of 1.8 K, we find that the absence of the inversion symmetry does not lead to an obvious deviation from an s-wave pairing symmetry in Re 3 W. 相似文献
997.
998.
以亚当姆预测 校正系统数值计算方法为基础,在同时考虑光束通过克尔介质后的相位和光束线型变化的情况下,利用惠更斯 菲涅尔衍射积分公式,对高斯光束通过克尔介质后的近场和远场的横向光强分布进行了研究.结果表明:当高斯光束通过“薄”介质的出射面时,不仅仅相位发生了变化,而且光强线型分布也不再呈理想的高斯分布,而是有一系列丝状的近高斯分布.光束通过克尔介质后,无论是在近场还是远场,其光束总能量分布都被发散了.结果同时表明:光束通过正克尔介质后的远场光强分布主要集中在中心附近,并逐渐向边缘减弱,而光束通过负克尔介质后远场光束能量主要集中在边缘. 相似文献
999.
光学非接触廓形测量技术研究进展 总被引:1,自引:0,他引:1
表面轮廓、几何尺寸、各种模具及自由曲面的精确测量是提高零件数字化制造水平的重要环节。对光学非接触测量方法及其关键技术进行了分析。介绍了光学非接触廓形测量的两种方法:光学被动式廓形测量法和光学主动式廓形测量法。对光学非接触廓形测量常用方法进行了分析。论述了光学非接触测量的关键技术和发展趋势。 相似文献
1000.
在直接计算分子配分函数的基础上,将无转动跃迁偶极矩平方近似为一常数,计算了对称陀螺分子NH3,0300a-0000 s跃迁在高温下的线强度.在296 K,计算的分子总配分函数与HITRAN数据库的结果符合很好,只有O.19%的百分误差.计算的跃迁线强度在2000 K和3000 K的高温与HITRAN数据库的结果也符合相当好,最大百分误差分别为-0.65%和-1.77%.这就表明分子配分函数和线强度的高温计算是可靠的.在此基础上,计算被扩展到更高温度,报道了对称陀螺分子NH30300 a-0000 s跃迁在极端高温4000和5000 K的模拟光谱.计算结果对大气分子高温光谱的实验测量和理论研究均有一定的参考价值. 相似文献