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61.
Cu doped MoSi2N4 monolayer (Cu-MoSi2N4) was firstly proposed to analyze adsorption performances of common gas molecules including O2, N2, CO, NO, NO2, CO2, SO2, H2O, NH3 and CH4 via density functional theory (DFT) combining with non-equilibrium Green's function (NEGF). The electronic transport calculations indicate that Cu-MoSi2N4 monolayer has high sensitivity for CO, NO, NO2 and NH3 molecules. However, only NH3 molecule adsorbs on the Cu-MoSi2N4 monolayer with moderate strength (−0.55 eV) and desorbs at room temperature (2.36×10−3 s). Thus, Cu-MoSi2N4 monolayer is demonstrated as a potential NH3 sensor. 相似文献
62.
土壤水溶性盐是表征土壤盐碱化程度的重要指标,也是评价耕地地力的重要参数,被纳入第三次全国土壤普查(“三普”)监测指标体系中。重量法是测定土壤水溶性盐总量的最常用方法,其测定过程易受多种因素影响,导致其测定结果不准。鉴于此,本文设计试验分别验证了水溶性盐浸提和浸提液固液分离这两个过程对测定结果的影响,结果表明浸提液固液分离是影响土壤水溶性盐总量测定准确度和精密度的主要因素。基于此进一步探究4种不同固液分离方式(布氏漏斗过滤、滤膜真空抽滤、离心、滤纸组合过滤)对测定结果的影响,结果表明相较于其它方式,滤纸组合过滤测定结果准确度高,适用于土壤水溶性盐总量的测定。对改进后的重量法测定土壤水溶性盐总量进行方法学确认,结果表明其检出限为0.01 g/kg,测定下限为0.04 g/kg;方法的准确度和精密度、适用范围等均符合相关要求。本文推荐的土壤水溶性盐总量测定方法为:土壤样品采用1:5土水比浸提,180 r/min振荡3 min,浸提液采用滤纸组合自然过滤;其测定结果的准确度和精密度符合相关要求。本文旨在为“三普”内业检测提供参考和借鉴,为全面摸清不同区域土壤水溶性盐含量水平及土壤盐渍化程度提供技术支撑。 相似文献
63.
64.
Experimental Investigation on Binary Phase Diagram of the Thermotropic Phase Transitions Compounds (n‐CnH2n+1R3)2ZnCl4 下载免费PDF全文
The thermotropic phase transitions compounds (n‐CnH2n+1R3)2ZnCl4 as well as a series of their binary mixtures were prepared by a solution reflux method from their ethanol solutions. The experimental subsolidus binary phase diagram of [n‐C18H37N(CH3)3]2ZnCl4‐[n‐(C18H37)2N(CH3)2]2ZnCl4 is constructed over the entire composition range by differential scanning calorimetry(DSC) and X‐ray. Experi‐ mental results indicate one stable intermediate phase [n‐C18H37N(CH3)3] [n‐(C18H37)2N(CH3)2]ZnCl4 at WC18C3Zn %=59.75 %, and two invariant three phase equilibria, which shows two eutectoid temperatures: Te1 at 310±1 K for eutectoid point WC18C3Zn %=36.24 %, Te2 at 313±1 K for eutectoid point WC18C3Zn %=80.17 %. These three noticeable solid‐solution ranges are α‐phase at the left, ?‐phase at the right, and ψ‐phase in the middle of the phase diagram. It is (n‐CnH2n+1R3)2ZnCl4 systems as phase change materials that are characterized the phase transition temperatures T in the range of 310 to 340 K, the transition enthalpies ΔH in the range of 38.40 and 168.72 J/g between two polymorphic forms. 相似文献
65.
Mind the correct basis set: A case study for predicting gas phase acidities of small compounds using calculations from first principles 下载免费PDF全文
Nina Tymińska Marta Włoch A. Timothy Royappa 《International journal of quantum chemistry》2015,115(1):42-49
Some of the most popular computational methods have been utilized to determine a dependency of the acidity trend of the first‐row hydrides on a choice of basis set. For about three decades, methyl anion ( ) was known as the strongest base but after Tian et al. were able to produce the gas phase lithium monoxide anion (LiO–) they discovered it was a stronger base than (Tian et al., Proc Natl Acad Soc USA 2008, 105, 7647). Furthermore, the authors confirmed their experimental results using high‐level ab initio methods, namely W1 and W2C composite methods, as well as complete active space‐averaged quadratic coupled cluster and Brueckner Doubles with triple excitation contribution (BD(T)) within the aug‐cc‐pVQZ basis set. These methods are highly demanding in terms of the computational effort as well as a level of expertise needed from the user to correctly conduct such calculations. We have shown that the proper acidity trend, that is, , can be obtained with less expensive, ”black‐box” type methods if only the basis set is properly chosen. Our results prove that the diffuse augmented basis sets are absolutely necessary for appropriate predictions of acidities. Our calculations show that the correct order of is achieved by augmenting relatively small cc‐pVXZ (X = D,T) basis sets. A similar effect is observed for the family of Pople's basis sets. Our estimate for with CCSD(T)/aug‐cc‐pVTZ was 423.8 kcal/mol, which agrees very well with the experimental value 425.7 ± 6.1 kcal/mol. An important finding is that the proper acidity trend may be reversed if the basis sets are not correctly selected. © 2014 Wiley Periodicals, Inc. 相似文献
66.
Deformation of single‐walled carbon nanotubes by interaction with graphene: A first‐principles study 下载免费PDF全文
Xiao Wang Juan Yang Ruoming Li Hong Jiang Yan Li 《Journal of computational chemistry》2015,36(10):717-722
The interaction between single‐walled carbon nanotubes (SWNTs) and graphene were studied with first‐principles calculations. Both SWNTs and single‐layer graphene (SLG) or double‐layer graphene (DLG) display more remarkable deformations with the increase of SWNT diameter, which implies a stronger interaction between SWNTs and graphene. Besides, in DLG, deformation of the upper‐layer graphene is less than in SLG. Zigzag SWNTs show stronger interactions with SLG than armchair SWNTs, whereas the order is reversed for DLG, which can be interpreted by the mechanical properties of SWNTs and graphene. Density of states and band structures were also studied, and it was found that the interaction between a SWNT and graphene is not strong enough to bring about obvious influence on the electronic structures of SWNTs. © 2015 Wiley Periodicals, Inc. 相似文献
67.
以鳞片石墨(GR)为原料,采用改性Hummers法液相氧化方法制备氧化石墨,通过超声剥离的方法剥离出片状的氧化石墨烯(GO),探讨了H2SO4环境与H2SO4+H3PO4混酸环境和KMnO4与GR的比例对GO制备的影响。采用FTIR、UV、TG、XRD、SEM和XPS等分析手段对制备的GO进行分析。结果表明:GO外貌是呈褶皱片状,在片层上主要有C=O、C-OH、-COOH和C-O-C等官能团,以共价键形式存在石墨层间;通过TG与XPS数据分析表明在H2SO4 H3PO4混酸环境下制备的GO含氧官能团较多,并且(KMnO4)与鳞片石墨的最佳比例是1:4。 相似文献
68.
The PLANE WAVE pseudo-potential method within density functional theory (DFT) has been used to investigate the structural, elastic, electronic and optical properties of XCaF3 (X = K and Rb) insulating. The studied compounds show a weak resistance to shear deformation compared to the resistance to the unidirectional compression. KCaF3 and RbCaF3 are considered ductile. The elastic constants and related parameters were predicted. The stiffness is more important in KCaF3, whereas, the lateral expansion is more important in RbCaF3. KCaF3 and RbCaF3 have R- Г indirect band gap. The main peaks in the imaginary part of the dielectric function correspond to the transition from the occupied state F−p to the unoccupied states Ca: s or K, Rb: p. At lower energies, KCaF3 and RbCaF3 show the same optical properties. Under pressure effect, the peaks of imaginary part of dielectric function were shifted toward high energy. 相似文献
69.
弹性力学混合状态方程的小波解法 总被引:1,自引:0,他引:1
应用小波理论求解弹性力学混合状态方程,讨论了解的收敛性。从文中的数值算例不难看出,该方法不失为混合状态方程一种新的求解途径。 相似文献
70.
为使弹性摩擦问题的线性互补法得到收敛性保证,提出一个摄动原理,证明了通过“摆脱摄动误差”可得到原离散模型的精确解。 相似文献