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101.
青海柴达木地区植物白刺叶中微量元素特征 总被引:7,自引:0,他引:7
青海柴达木地区分布有丰富的白刺植物资源。利用220FS原子吸收光谱仪分析了该地区三种白刺叶片的Cu,Zn,Fe,Mn,Cr,Ni,Cd等微量元素。结果表明,铬、 锰含量显著提高是青海柴达木地区植物白刺叶资源微量元素特征。这为柴达木地区白刺叶资源的开发利用提供科学依据。 相似文献
102.
Feng‐You Hao Yong‐Fang Zhao Xiao‐Gong Jing Xin‐Ying Li Feng‐Li Liu 《International journal of quantum chemistry》2007,107(6):1502-1507
Ab initio quantum chemical calculations have been performed on X2Cl? and X2Cl (X = C, Si, Ge) clusters. The geometrical structures, vibrational frequencies, electronic properties and dissociation energies are investigated at the Hartree–Fock (HF), Møller–Plesset second‐ and fourth‐order (MP2, MP4), CCSD(T) level with the 6‐311+G(d) basis set. The X2Cl (X = C, Si, Ge) and X2Cl? (X = Si, Ge) take a bent shape obtained at the ground state, while C2Cl? has a linear structure. The impact on internal electron transfer between the X2Cl and the corresponding anional clusters is studied. The three different types of electron affinities (EAs) at the CCSD(T) are reported. The most reliable adiabatic electronic affinities, obtained at the CCSD(T)/cc‐pvqz level of theory, are predicted to be 3.30, 2.62, and 1.98 eV for C2Cl, Si2Cl, and Ge2Cl, respectively. The calculated EAs of C2Cl and Ge2Cl are in good agreement with theoretical results reported. The correlation effects and basis sets effects on the geometrical structures and dissociation energies are discussed. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 相似文献
103.
牛血清白蛋白中氨基酸的高效液相色谱荧光测定及质谱鉴定 总被引:1,自引:0,他引:1
利用新型荧光试剂1,2苯-并-3,4二-氢咔唑-9乙-基氯甲酸酯(BCEOC)作为柱前衍生化试剂,在Hypersil BDS C18(4.6 mm×200 mm,5μm)反相色谱柱上,采用梯度洗脱对氨基酸衍生物进行了分离检测。检测的激发和发射波长分别为λex=333 nm,λem=390 nm。采用电喷雾离子源(ESI Source),实现了牛血清白蛋白中氨基酸的定性测定。荧光定量检测的线性回归系数均大于0.999;检出限为6.3~117.6 fmo。l 相似文献
104.
Nonlinear optical (NLO) crystals assembled with conventional non-π-conjugated tetrahedral functional building units (FBUs), generally referring to [PO4] and [BO4], usually exhibit weak nonlinearity and poor birefringence. It is currently proposed that partially substituting oxygen atoms with fluoride atoms in these FBUs could enhance these crucial properties. Hence, we investigated for the first time the NLO-related properties of NH4BAsO4F (ABAF), which was constructed from tetrahedral [BO3F] and [AsO4] FBUs, and enhancements of these properties were observed in this material, that is large second-harmonic generation (SHG) response (2 × KDP) and improved birefringence (0.03 at 1064 nm). Notably, both SHG coefficient and birefringence of ABAF exceeded those of a great majority of phosphates, sulfates, or boron phosphates and achieved a preferable balance. It is interesting that ABAF shows vast structural similarities to the typical NLO crystals Sr2Be2B2O7 (SBBO) and KBe2BO3F2 (KBBF), which might be the partial reason why it showed improvement in these vital properties. This work may afford some inspiration for enhancing the key performances of NLO crystals assembled with non-π-conjugated tetrahedra.We report a new nonlinear optical crystal assembled exclusively with tetrahedral functional building units in which enhanced birefringence (Δn) and second-harmonic generation (deff) were observed. 相似文献
105.
Abthagir PS Ha YG You EA Jeong SH Seo HS Choi JH 《The journal of physical chemistry. B》2005,109(50):23918-23924
The neutral cluster beam deposition (NCBD) method has been applied to produce and characterize organic thin-film transistors (OTFTs) based upon tetracene and pentacene molecules as active layers. Organic thin films were prepared by the NCBD method on hexamethyldisilazane (HMDS)-untreated and -pretreated silicon dioxide (SiO2) substrates at room temperature. The surface morphology and structures for the tetracene and pentacene thin films were examined by atomic force microscopy (AFM) and X-ray diffraction (XRD). The measurements demonstrate that the weakly bound and highly directional neutral cluster beams are efficient in producing high-quality single-crystalline thin films with uniform, smooth surfaces and that SiO2 surface treatment with HMDS enhances the crystallinity of the pentacene thin-film phase. Tetracene- and pentacene-based OTFTs with the top-contact structure showed typical source-drain current modulation behavior with different gate voltages. Device parameters such as hole carrier mobility, current on/off ratio, threshold voltage, and subthreshold slope have been derived from the current-voltage characteristics together with the effects of surface treatment with HMDS. In particular, the high field-effect room-temperature mobilities for the HMDS-untreated OTFTs are found to be comparable to the most widely reported values for the respective untreated tetracene and pentacene thin-film transistors. The device performance strongly correlates with the surface morphology, and the structural properties of the organic thin films are discussed. 相似文献
106.
In this paper, the authors study the multiplicity of solutions to the weighted p-Laplacian with isolated singularity and di?usion suppressed by convection ?div(|x|α|?u|p?2?u) + λ 1/|x|β |?u|p?2?u · x = |x|γg(|x|) in B \ {0} subject to nonlinear Robin boundary value condition |x|α|?u|p?2?u · ?n = A ? ρu on ?B,where λ > 0, B ? RN(N ≥ 2) is the unit ball centered at the origin, α > 0, p > 1, β ∈ R, γ > ?N, g ∈ C([0,1]) with g(0) > 0, A ∈ R, ρ > 0 and ?n is the unit outward normal. The same problem with di?usion promoted by convection, namely λ ≤ 0, has already been discussed by the last two authors (Song-Yin (2012)), where the existence, nonexistence and classi?cation of singularities for solutions are presented. Completely di?erent from [Song, H. J. and Yin, J. X., Removable isolated singularities of solutions to the weighted p-Laplacian with singular convection, Math. Meth. Appl. Sci., 35, 2012, 1089–1100], in the present case λ > 0, namely the di?usion is suppressed by the convection, non-singular solutions are not only existent but also may be in?nite which vary according only to the values of solutions at the isolated singular point. At the same time, the singular solutions may exist only if the di?usion dominates the convection. 相似文献
107.
As a continuation of part I of the paper under the same title, we developgeneral monotonic enclosure methods for the couple systems of the splitting equations {x=G([x]a,[x]b,[y]c) y=G([y]a,[y]b,[x]c),which models the system of equations associated with hybrid and aaynchronotts monotonicity as well as convexity. The resulting algorithms and convergence theorems generalize and unify various known methods and monotonic enclosure theorents established by other authors. 相似文献
108.
X. H. Yan J. R. Yan J. Q. You Y. P. Mei 《Zeitschrift für Physik B Condensed Matter》1994,94(4):439-446
Electronic properties of a general class of one-dimensional two-tile systems are calculated exactly. The systems containing periodic crystals, generalized Fibonacci quasicrystals, generalized Thue-Morse aperiodic lattices and even other two-tile aperiodic lattices, can be divided into two different families which are constructed by the inflation rules: {A, B}{A
m11
B
m12,A
m21
B
m22} and {A, B}{A
n11
B
n12,B
n21
A
n22}, respectively. As typical examples, global spectra of bands and density of states in some two-tile aperiodic systems are numerically calculated. Some interesting properties are obtained. 相似文献
109.
110.
In a previous paper, a scheme of integral approximation was proposed, in which a large number of two-electron integrals containing a certain kind of orbital pairs, i.e., weakly related pairs, can be neglected. A new criterion for partitioning orbital pairs into two groups, i.e., strongly and weakly related pairs, is introduced in order to allow for neglect of more integrals without sacrificing the accuracy of a computation. Test calculations on the BH3? C2H4 complex show that by the use of the new version, results of roughly the same accuracy as was obtained by the old version is obtained by retaining 80% of the integrals used in the old version. This kind of saving is more significant for larger molecules. For example, in a calculation on Cu-porphine with 203 CGTO 'S , the revised version will require about 2.0 × 106 integrals, while the original version will require about 4.5 × 106. And these two approximate calculations are expected to give the results of roughly the same accuracy. 相似文献