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81.
作为Hom-Leibniz代数胚的代数类比, 本文引入Hom-Leibniz-Rinehart代数的概念. 证明了分裂的正则Hom-Leibniz-Rinehart代数$L$写成$L=U+\sum_{\gamma}I_\gamma$, 其中$U$为极大交换子代数$H$的子空间和$I_\gamma$为$L$的理想, 若$[\gamma]\neq[d]$, 满足$[I_\gamma, I_d]=0$. 随后分别发展了分裂Hom-Leibniz-Rinehart代数的根和权的连通技术.最后研究了紧致的正则Hom-Leibniz-Rinehart代数的结构. 相似文献
82.
矩阵平方根在数学的许多应用中起着重要的作用.本文研究M-矩阵平方根的计算问题,提出一种计算正则M-矩阵平方根的迭代方法.首先将这个问题转化为M-矩阵代数Riccati方程,进而提出一种有效的方法来求解这个特殊的MARE.理论分析表明,该方法在一定条件下是收敛的.数值实验表明该方法是可行的,且优于二项式迭代法. 相似文献
83.
Chris A. Kieslich 《Journal of Non》2011,357(2):707-716
Electrostatically-driven association of proteins is important to many biological functions, and understanding which amino acid residues contribute to these interactions is crucial to protein design. Theoretical calculations that are used to elucidate the role of electrostatics in association are typically based on a single experimentally determined protein structure, while an underlying rigid-body assumption is adopted. The goal of this study was to investigate the role of conformational fluctuations on electrostatic interaction energies, as applied to the electrostatic analysis of barnase-barstar. For our calculations, we apply theoretical alanine-scan mutagenesis to introduce charge perturbations by replacing every ionizable residue with alanine, one at a time. Electrostatic clustering and free energy calculations based on the Poisson-Boltzmann method are used to evaluate the effects of each perturbation. Molecular dynamics simulations are performed for the barnase-barstar parent complex and seven experimental alanine mutations from the literature, in order to introduce relaxation before and after mutation. We discuss the effects of dynamics, in the form of pre- and post-mutation relaxation, on electrostatic clustering and free energies of association in light of experimental data. We also examine the utility of nine electrostatic similarity methods for clustering of barnase alanine-scan mutants. Our calculations suggest that the rigid-body assumption is reasonable for electrostatic calculations of barnase-barstar. 相似文献
84.
Leaf and root extracts of Clerodendrum infortunatum L. have been reported to show anthelmintic efficacy on a cestode parasite Raillietina tetragona. Its leaf showed no toxicity at 1000 mg/kg body weight but root toxicity study was not known. Therefore, our study is to test both leaf and root extracts at 2000 and 3000 mg/kg body weight concentration given orally for 15 days in four groups of Swiss albino mice, keeping another set as control (without plant extract). Weight and behaviour of mice were recorded daily. Feeding, movement pattern were normal in all treatments as that of control. Though body weight increase, there was no change in the relative organ weight. Biochemical and haematological studies revealed no significant change from control and no alteration in histopathological study of liver and kidney from that of control. The plant extracts thus shown to be safe for consumption. 相似文献
85.
Maria Khan Mohammad Yusuf Majed Al Robaian Mohammed Ali 《Natural product research》2018,32(14):1639-1647
Salvadora persica is virtuous to have a variety of phytoconstituents responsible for many biological activities some of them identified particularly while some are still to be acknowledged. A number of steroidal, glycosidic, terpenoids, saponins and functional esters are reported till date. The present study deals with extraction, isolation, and characterisation of four novel steroidal esters by systematic cold extraction of S. persica. The extracted phytoconstituents were characterised by sophisticated spectral UV, IR, NMR and MS, techniques. The reported four new β-Sitosteryl esters SP-2, 3, 5 and 6 were extracted and reported for the first time. 相似文献
86.
Ahmed M. M. Gabr Hoda B. Mabrok Emam A. Abdel-Rahim Mohamed K. El-Bahr Iryna Smetanska 《Natural product research》2018,32(15):1867-1871
Hairy root culture is a promising alternative method for the production of secondary metabolites. In this study, transformed root of Linum usitatissimum was established using Agrobacterium rhizogenes A4 strain from root cultures for lignans, phenolic acids and antioxidant capacity determination. Total lignin content (secoisolariciresinol diglucoside, secoisolariciresinol and matairesinol) was 55.5% higher in transformed root cultures than in the non-transformed root culture. Secoisolariciresinol was detected in higher concentration (2.107 μmol/g DM) in the transformed root culture than non-transformed culture (1.099 μmol/g DM). Secoisolariciresinol diglucoside and matairesinol were exclusively detected in the transformed root culture, but were not found in the non-transformed root culture. The overall production of phenolic acids in transformed roots was approximately 3.5 times higher than that of the corresponding non-transformed culture. Free radical scavenging DPPH˙ and ABTS˙+ assays showed 2.9-fold and 1.76-fold higher anti-oxidant activity in transformed root culture as compared to non-transformed. 相似文献
87.
It is proved that the center of an automorphism group Aut(FVL2) of a free vector lattice FVL2 on a set of two free generators is isomorphic to a multiplicative group of positive reals. It is shown that the free vector lattice FVL2 has an isomorphic representation by continuous piecewise linear functions of the real line; as a consequence, the ideal lattice and the root system for rectifying ideals in FVL2 are amply described. Similar results are obtained for a free vector lattice FVL2
Q
2 generated by two elements over a field of rational numbers. 相似文献
88.
89.
ABSTRACT. Different harvest timing models make different assumptions about timber price behavior. Those seeking to optimize harvest timing are thus first faced with a decision regarding which assumption of price behavior is appropriate for their market, particularly regarding the presence of a unit root in the timber price time series. Unfortunately for landowners and investors, the literature provides conflicting guidance on this subject. One source for the ambiguous results of unit root tests of timber prices may involve data problems. We used Monte Carlo simulations to show that aggregating observations below their observed rate resulted in similar power reductions and empirical size distortions across three classes of unit root tests. Moving‐average error structures can also affect power and sizes of tests on period‐averaged data. Such error structures can also be created by the kind of temporal averaging common in reported timber prices. If we take timber prices at their face value and therefore ignore these sampling error and temporal aggregation complications, we find that unit root tests on southern timber prices support a unit root in 158 out of 208 product‐deflation combinations tested, random walks in 38 of the series found to be nonsta‐tionary, and stationarity in none. However, if we recognize temporal aggregation errors, unit root tests more commonly favor stationarity, especially for pulpwood stumpage. Because price trends for sawtimber and pulpwood products may behave differently even in the same region, stochastic harvest timing models must be developed that allow their multiple products to follow different price paths. 相似文献
90.
设G为n阶κ正则简单连通图(κ≥2),λ是图G的次根,d(G)是图G的直径,如果G不是二部图,且d(G)≠2,则d(G)≤[log(n-1)/log(κ/λ)],并且当G≌时,这一上界可达. 相似文献