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排序方式: 共有1686条查询结果,搜索用时 312 毫秒
91.
Rodrigo D. Tosso Oscar Parravicini M. Natalia C. Zarycz Emilio Angelina Marcela Vettorazzi Nélida Peruchena Sebastián Andujar Ricardo D. Enriz 《Journal of computational chemistry》2020,41(21):1898-1911
We report an exhaustive conformational and electronic study on dopamine (DA) interacting with the D2 dopamine receptor (D2DR). For the first time, the complete surface of the conformational potential energy of the complex DA/D2DR is reported. Such a surface was obtained through the use of QM/MM calculations. A detailed study of the molecular interactions that stabilize and destabilize the different molecular complexes was carried out using two techniques: Quantum Theory of Atoms in Molecules computations and nuclear magnetic shielding constants calculations. A comparative study of the behavior of DA in the gas phase, aqueous solution, and in the active site of D2DR has allowed us to evaluate the degree of deformation suffered by the ligand and, therefore, analyze how rustic are the lock-key model and the induced fit theory in this case. Our results allow us to propose one of the conformations obtained as the “biologically relevant” conformation of DA when it is interacting with the D2DR. 相似文献
92.
In this study, a molecularly imprinted sensor technology is engineered to detect glucose in real blood samples by chronoimpedimetrically. The imprinting process of glucose (Glc) was carried out by electrochemical polymerization of aminophenylboronic acid (APBA) and pyrrole (Py) by performing cyclic voltammetry (CV). Afterwards, glucose molecule was removed from imprinted surface by 5 % acetic acid to reveal glucose imprinted cavities. Electrochemical Impedance Spectroscopy (EIS) was used to characterize sensor modification steps and glucose removal. Glucose monitoring process was carried out chronoimpedimetrically(CI) for the first time in real blood samples. Calibration curve was prepared between 20–800 mg/dL. The standard deviations of the 18 calibration curves R2 were calculated as 0.9866±0.0066 to assess reproducibility. Recovery was calculated by using 105 mg/dL Glc Serum Sample, which was monitored by auto analyzer and into this sample 50 mg/dL Glc added and our sensor response was 147.92±2.43 mg/dL, 98.6±1.62 % (n=5). Non‐imprinted (NIP) sensor gave no signal for the glucose concentration. 相似文献
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95.
Dr. Oscar Bertran Dr. Guillermo Revilla‐López Dr. Jordi Casanovas Dr. Luis J. del Valle Dr. Pau Turon Prof. Dr. Jordi Puiggalí Prof. Dr. Carlos Alemán 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(19):6631-6636
In spite of the clinical importance of hydroxyapatite (HAp), the mechanism that controls its dissolution in acidic environments remains unclear. Knowledge of such a process is highly desirable to provide better understanding of different pathologies, as for example osteoporosis, and of the HAp potential as vehicle for gene delivery to replace damaged DNA. In this work, the mechanism of dissolution in acid conditions of HAp nanoparticles encapsulating double‐stranded DNA has been investigated at the atomistic level using computer simulations. For this purpose, four consecutive (multi‐step) molecular dynamics simulations, involving different temperatures and proton transfer processes, have been carried out. Results are consistent with a polynuclear decalcification mechanism in which proton transfer processes, from the surface to the internal regions of the particle, play a crucial role. In addition, the DNA remains protected by the mineral mold and transferred proton from both temperature and chemicals. These results, which indicate that biomineralization imparts very effective protection to DNA, also have important implications in other biomedical fields, as for example in the design of artificial bones or in the fight against osteoporosis by promoting the fixation of Ca2+ ions. 相似文献
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97.
Sara Cruz?y?Cruz Oscar Rosas-Ortiz 《International Journal of Theoretical Physics》2011,50(7):2201-2210
The Schr?dinger equation for position-dependent mass singular oscillators is solved by means of the factorization method and
point transformations. These systems share their spectrum with the conventional singular oscillator. Ladder operators are
constructed to close the su(1,1) Lie algebra and the involved point transformations are shown to preserve the structure of the Barut-Girardello and Perelomov
coherent states. 相似文献
98.
Oscar Perdomo 《Proceedings of the American Mathematical Society》2002,130(11):3379-3384
The stability operator of a compact oriented minimal hypersurface is given by , where is the norm of the second fundamental form. Let be the first eigenvalue of and define . In 1968 Simons proved that for any non-equatorial minimal hypersurface . In this paper we will show that only for Clifford hypersurfaces. For minimal surfaces in , let denote the area of and let denote the genus of . We will prove that . Moreover, if is embedded, then we will prove that . If in addition to the embeddeness condition we have that , then we will prove that .
99.
The influence of previous exposure to ultraviolet-A radiation (UVA) was studied on the susceptibility of Enterobacter cloacae to undergo the growth delay effect. Comparison of growth curves corresponding to irradiated and control cells showed that a previous treatment with UVA almost abolished the growth delay effect. UV absorption spectra of tRNA, and reverse phase HPLC analysis of hydrolysed tRNA, demonstrated a low content of 4-thiouridine in E. cloacae cells grown after UVA exposure at low doses. Since 4-thiouridine is the UVA target responsible for initiation of growth delay, this observation explained the influence of previous exposure to UVA on the susceptibility of this organism to undergo growth delay. A similar but weaker alteration was found when Escherichia coli was assayed. The results suggest that, in addition to cross-linking with cytidine residues, the content of 4-thiouridine in tRNA may be modified by UVA by an unknown mechanism. 相似文献
100.
Niobium and tantalum carbide clusters have been isolated in the gas phase and irradiated with intense tunable infrared (IR) light. Stable neutral clusters are selectively ionized and subsequently detected in a mass spectrometer. By tuning the IR frequency, infrared multiphoton absorption spectra are obtained for a whole range of clusters. These mass-selective IR spectra lead to insights into the structures of small niobium and tantalum carbide clusters and nanocrystals. 相似文献