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1.
综合使用光谱技术对作物养分进行实时、有效诊断,有助于作物的精准管理、保障产量和减少环境污染,提高肥料利用率,并且为定量估测作物生化组分状况提供了一种新的途径。光谱指数是进行作物叶片叶绿素实时估测的重要指标,然而由于受到环境条件及内在生化成分的影响,估测结果不尽满意。为了进一步提高光谱指数在估测作物叶片叶绿素含量时的抗干扰能力和敏感性,于2020年在内蒙古玉米种植典型区域进行不同氮梯度的田间试验,在玉米的四个关键生育时期获取叶片的光谱反射率和叶绿素值,通过建立基于面积的光谱指数和叶片叶绿素值的关系模型并进行光谱指数的优化及评价。结果表明,生育时期对面积光谱指数与叶片叶绿素值的关系有显著影响。前人研究的基于面积的光谱指数在玉米苗期时对于叶片叶绿素含量的估测效果较差,而对抽雄期叶片叶绿素含量的估测效果最佳。基于优化算法构建的面积光谱指数显著提高了光谱指数对叶片叶绿素含量估测的准确度和稳定性,基于优化算法的优化三角形植被指数(OTVI)、优化叶绿素吸收积分指数(OCAI)和优化双峰面积归一化差值指数(ONDDA)在不同生育时期上比前人研究的面积光谱指数具有更强的叶绿素含量估测能力,估测模型的决定系数R2在0.94~0.99之间。与优化三角形植被指数(OTVI)和优化叶绿素吸收积分指数(OCAI)相比优化双峰面积归一化差值指数(ONDDA)在估测春玉米不同生育时期叶片叶绿素含量方面更为稳定,预测模型验证结果的决定系数R2为0.94,并且验证误差最小,RMSE和NRMSE%分别为2.29%,3.94%,模型估测值与实测值的验证斜率为0.996,接近1。综上所述,ONDDA是一个实用且适合于估测不同生育时期叶片叶绿素含量的面积光谱指数。 相似文献
2.
Acta Mathematica Sinica, English Series - For a finite group G, the power graph $$\cal{P}(G)$$ is a simple connected graph whose vertex set is the set of elements of G and two distinct vertices x... 相似文献
3.
Yin Qingqing Xu Fen Sun Lixian Li Yaying Liao Lumin Wang Tao Guan Yanxun Xia Yongpeng Zhang Chenchen Wei Sheng Zhang Huanzhi Li Bin 《Journal of Thermal Analysis and Calorimetry》2022,147(12):6583-6592
Journal of Thermal Analysis and Calorimetry - Polyethylene glycol (PEG) is widely used as phase change materials (PCMs). However, the leakage and low thermal conductivity issues restrict its... 相似文献
4.
采用基于Compass力场的分子动力学(MD)方法,研究了惰性气体氙(Xe)和氪(Kr)在塑料闪烁体(聚乙烯基对甲苯)的平整和粗糙表面的吸附和扩散行为.由惰性气体吸附曲线的均方根位移(MSD),得到了Xe/Kr气体在聚乙烯基对甲苯表面的扩散系数.研究结果表明,Kr/Xe气体均被稳定地吸附在塑料闪烁体表面,其稳定性随着温度的升高而增加,Xe分子的吸附性强于Kr分子. Kr/Xe气体在聚乙烯基对甲苯表面具有较强的扩散性能,扩散深度随着温度与厚度的增加而增加,最大为22.865?,Kr分子扩散能力强于Xe分子.基底粗糙表面增加了两种惰性气体分子的吸附和扩散. 相似文献
5.
Rechargeable Mg batteries (RMBs) are advantageous large-scale energy-storage devices because of the high abundance and high safety, but exploring high-performance cathodes remains the largest difficulty for their development. Compared with oxides and sulfides, selenides show better Mg-storage performance because the weaker interaction with the Mg2+ cation favors fast kinetics. Herein, nanorod-like FeSe2 was synthesized and investigated as a cathode for RMBs. Compared with microspheres and microparticles, nanorods exhibit higher capacity and better rate capability with a smaller particle size. The FeSe2 nanorods show a high capacity of 191 mAh g−1 at 50 mA g−1 and a good rate performance of 39 mAh g−1 at 1000 mA g−1. Ex situ characterizations demonstrate the Mg2+ intercalation mechanism for FeSe2, and a slight conversion reaction occurs on the surface of the particles. The capacity fading is mainly because of the dissolution of Fe2+, which is caused by the reaction between Fe2+ and Cl− of the electrolyte during the charge process on the surface of the particles. The surface of FeSe2 is mainly selenium after long cycling, which may also dissolve in the electrolyte during cycling. The present work develops a new type of Mg2+ intercalation cathode for RMBs. More importantly, the fading mechanism revealed herein has considered the specificity of Mg battery electrolyte and would assist a better understanding of selenide cathodes for RMBs. 相似文献
6.
Structural stability in terms of the decomposition temperature in LiMn2O4 was systematically investigated by a series of high-temperature and high-pressure experiments.LiMn2O4 was found to have structural stability up to 5 GPa at room temperature.Under ambient pressure,the compound decomposed at 1300℃.The decomposition temperature decreased with increasing pressure,yielding more complex decomposed products.Below the decomposition temperature,the crystal structure of LiMn2O4 varied with pressure.The presented results in this study offer new insights into the thermal and pressure stability of LiMn2O4 materials as a cathode for lithium-ion batteries that can operate under extreme conditions.Therefore,these findings may serve as a useful guide for future work for improving lithium-ion batteries. 相似文献
7.
The Ramanujan Journal - Let $$k\ge 2$$ be an even integer, and let M be a positive integer. We prove a hybrid subconvexity bound for $$L(1/2,\text {sym}^2 f\otimes \chi )$$ with the associated... 相似文献
8.
Nonlinear Dynamics - This paper proposes an output feedback control strategy to achieve the global regulation of a class of large-scale feedforward nonlinear systems with discrete and distributed... 相似文献
9.
10.
The properties of six kinds of intrinsic point defects in monolayer GeS are systematically investigated using the“transfer to real state”model,based on density functional theory.We find that Ge vacancy is the dominant intrinsic acceptor defect,due to its shallow acceptor transition energy level and lowest formation energy,which is primarily responsible for the intrinsic p-type conductivity of monolayer GeS,and effectively explains the native p-type conductivity of GeS observed in experiment.The shallow acceptor transition level derives from the local structural distortion induced by Coulomb repulsion between the charged vacancy center and its surrounding anions.Furthermore,with respect to growth conditions,Ge vacancies will be compensated by fewer n-type intrinsic defects under Ge-poor growth conditions.Our results have established the physical origin of the intrinsic p-type conductivity in monolayer GeS,as well as expanding the understanding of defect properties in lowdimensional semiconductor materials. 相似文献