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921.
《Arabian Journal of Chemistry》2022,15(5):103759
Psidium guajava L., commonly known as guava is an important tropical food plant with diverse medicinal values. In traditional medicine, it is used in the treatment of various diseases such as diarrhoea, diabetes, rheumatism, ulcers, malaria, cough, and bacterial infections. The aim of this review is to provide up-to-date information on the ethnomedicinal uses, bioactive compounds, and pharmacological activities of P. guajava with greater emphasis on its therapeutic potentials. The bioactive constituents extracted from P. guajava include phytochemicals (gallic acid, casuariin, catechin, chlorogenic acid, rutin, vanillic acid, quercetin, syringic acid, kaempferol, apigenin, cinnamic acid, luteolin, quercetin-3-O-α-L-arabinopyranoside, morin, ellagic acid, guaijaverin, pedunculoside, asiastic acid, ursolic acid, oleanolic acid, methyl gallate and epicatechin) and essential oils (limonene, trans-caryophyllene, α-humulene, γ-muurolene, selinene, caryophyllene oxide, bisabolol, isocaryophyllene, δ-cadinene, α-copaene, α-cedrene, β-eudesmol, α-pinene, β-pinene, β-myrcene, linalool, α-terpineol and eucalyptol). In vitro and in vivo studies demonstrated that P. guajava possesses pharmacological activities such as antidiabetic, antidiarrhoeal, hepatoprotective, anticancer, antioxidant, anti-inflammatory, antiestrogenic, and antibacterial activities which support its traditional uses. The exhibited pharmacological activities reported may be attributed to the numerous bioactive compounds present in different parts of P. guajava. Based on the beneficial effects of P. guajava as well as its bioactive constituents, it can be exploited in the development of pharmaceutical products and functional foods. However, there is a need for comprehensive studies in clinical trials to establish the safe doses and efficacy of P. guajava for the treatment of several diseases. 相似文献
922.
针对混流装配线存在的工序作业多、平衡难度大等问题,以U型布置的混装线为研究对象,兼顾工作站平均负荷和瞬时负荷平衡,在最小化工作站数的基础上均衡了工作站间和工作站内不同产品的作业负荷,建立U型混流装配线多目标平衡优化模型,同时提出目标法解决联合目标中的目标函数兼容性问题。设计并运用改进的自适应遗传算法求解模型,考虑到交叉、变异操作的随机性,在变异阶段加入强制规则,并对新生成的子代个体进行基因冲突检测,以提高可行解的比率。算例研究的结果表明本文所提的多目标优化方法能够较好地解决混装线平衡问题。 相似文献
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925.
J. Papadakis G. S. Fanourgakis S. C. Farantos M. Founargiotakis 《Journal of computational chemistry》1997,18(8):1011-1022
The most robust numerical algorithms for unconstrained optimization that involve a line search are tested in the problem of locating stable structures and transition states of atomic microclusters. Specifically, the popular quenching technique is compared with conjugate gradient and variable metric algorithms in the Mg+Arn clusters. It is found that the variable metric method BFGS combined with an approximate line minimization routine is the most efficient, and it shows global convergence properties. This technique is applied to find a few hundred stationary points of Mg+Ar12 and to locate isomerization paths between the two most stable icosahedral structures found for Mg+Ar12. The latter correspond to a solvated and a nonsolvated ion, respectively. © 1997 John Wiley & Sons, Inc. J Comput Chem 18 :1011–1022, 1997 相似文献
926.
Ruslan M. Minyaev Wolfgang Quapp Govindan Subramanian Paul von R. Schleyer Yirong Mo 《Journal of computational chemistry》1997,18(14):1792-1803
The paths of correlated internal disrotation (barrier less than 0.4 kcal/mol) and conrotation (barrier around 1.9 kcal/mol) of the two BH2 groups in H2BCH2BH2 have been computed employing ab initio [MP2(full)/6–31G**] and density functional theory (Becke3LYP/6–311+G**) methods. Two B(SINGLE BOND)C(DOTTED BOND)B(p) hyperconjugative interactions stabilize the Cs symmetric H2BCH2BH2 isomer ( 1 ). The B(SINGLE BOND)C(DOTTED BOND)B(p) hyperconjugative stabilization, evaluated by homodesmotic reactions and using the orbital deletion procedure (which “deactivates” the “vacant” born p orbital), is less than 6 kcal/mol in diborylmethane. The B(SINGLE BOND)C(DOTTED BOND)B(p) stabilization is shown to be remarkably large in C4B6H10 (Td). At MP2(fu)/6–31G**, disproportionation into 1 and methane is only 5.6 kcal/mol exothermic. The 1,3 H exchange in diborylmethane is an asynchronous process and proceeds via a doubly bridged cyclic intermediate with 9.3 kcal/mol barrier. Structures with “planar tetracoordinate” carbon are stabilized considerably by BH2 substituents, but they are still high in energy. © 1997 John Wiley & Sons, Inc. J Comput Chem 18 : 1792–1803, 1997 相似文献
927.
928.
Characterization of the Protons in Polycrystalline Paratungstates using 1H MAS NMR Investigations 1H MAS NMR experiments are used to characterize the non‐acid protons of the anions in polycrystalline paratungstates by means of the measured isotropic chemical shift values. The investigation of various hydrates of ammonium paratungstate allows a direct proof of protons in NH4 ions and in water molecules while protons of the anions are not detectable. However, for both the potassium and the sodium paratungstates 1H MAS NMR investigations detected the protons of water molecules and the non‐acid protons of the paratungstate anions. Additional 1H broad‐line NMR experiments at 173 K support the interpretation of the results obtained by the 1H MAS NMR investigations. For the NMR signal of the non‐acid protons of the paratungstate anion in the 1H MAS NMR spectra of the potassium salt line‐splitting appears. This refers to the existence of two nonidentical positions of the protons in the crystal lattice and is in agreement with the results of the X‐ray structural analysis. 相似文献
929.
Nasima Arshad Muhammad Ismail Mir Fouzia Perveen Aneela Javed Memona Javaid Aamer Saeed Pervaiz Ali Channar Shahid Iqbal Farooqi Saad Alkahtani Jamshed Anwar 《Molecules (Basel, Switzerland)》2022,27(2)
Imidazolidine and thiazolidine-based isatin derivatives (IST-01–04) were synthesized, characterized, and tested for their interactions with ds-DNA. Theoretical and experimental findings showed good compatibility and indicated compound–DNA binding by mixed mode of interactions. The evaluated binding parameters, i.e., binding constant (Kb), free energy change (ΔG), and binding site sizes (n), inferred comparatively greater and more spontaneous binding interactions of IST-02 and then IST-04 with the DNA, among all compounds tested under physiological pH and temperature (7.4, 37 °C). The cytotoxic activity of all compounds was assessed against HeLa (cervical carcinoma), MCF-7 (breast carcinoma), and HuH-7 (liver carcinoma), as well as normal HEK-293 (human embryonic kidney) cell lines. Among all compounds, IST-02 and 04 were found to be cytotoxic against HuH-7 cell lines with percentage cell toxicity of 75% and 66%, respectively, at 500 ng/µL dosage. Moreover, HEK-293 cells exhibit tolerance to the increasing drug concentration, suggesting these two compounds are less cytotoxic against normal cell lines compared to cancer cell lines. Hence, both DNA binding and cytotoxicity studies proved imidazolidine (IST-02) and thiazolidine (IST-04)-based isatin derivatives as potent anticancer drug candidates among which imidazolidine (IST-02) is comparatively the more promising. 相似文献
930.
G. Bodor S. Gall K. D. Hberle U. Lode W. Wilke 《Journal of Polymer Science.Polymer Physics》1996,34(3):485-496
A method for the calculation of crystallite size distributions from the profile of wide-angle x-ray reflections is developed. The influence of lattice distortions on the profile is taken into account. The information about the lattice distortions is obtained from the measurement of the integral widths of a number of reflections. The method is applied to samples of (ethylen-1 hexen) copolymers. The change of crystallite size distributions in lateral directions with increasing temperature (20–121°C) is measured. Recrystallization processes at temperatures near the melting point are observed. © 1996 John Wiley & Sons, Inc. 相似文献