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891.
892.
Composition of mobile phase can greatly influence the success of electrospray ionization (ESI)-interfaced liquid chromatography-mass spectrometry analysis. To investigate the relationship between formic-acid-based modification of mobile phase and ESI nebulizing conditions, an API 4000 ESI source and a TSQ Quantum one were compared under the same chromatographic conditions. Ginkgo terpene lactones and flavonols were measured in plasma, which involved using ascorbic acid to circumvent cross-interference between the analytes. ESI responses to using formic acid included changes in signal intensity, matrix effect, and upper limit of quantification. Significant disparities in the responses were observed between the two ESI sources, suggesting that the use of electrolyte modifier in liquid chromatography mobile phase and the pneumatic nebulization for ESI should be properly balanced to accomplish optimal ESI-based analysis. The distribution of unpaired ions toward the surface of the initial droplet was assumed to be an important step in the pneumatic ESI process. When using the electrolyte in mobile phase, a too fast droplet reduction by rapid-heating-assisted pneumatic nebulization could negatively decrease the time available for the unpaired ions to migrate from droplet interior to its surface. Ascorbic acid was identified as a major interfering substance for the bioanalytical assay; the interference mechanism might be associated with hindering the unpaired analyte ions from distributing toward the droplet surface rather than outcompeting the analyte ions for the limited excess charge on droplets surface. The current work extends the knowledge base of pneumatic ESI, which has implication for optimal use of the ESI-interfaced liquid chromatography-mass spectrometry technique. 相似文献
893.
通过利用K泛函及光滑模、不等式等技巧,在Orlicz空间中讨论了Müntz有理逼近问题,得到了有理逼近的三种估计. 相似文献
894.
The time-dependent density functional theory (TDDFT) method was carried out to investigate the excited state intramolecular proton transfer (ESIPT) process of 3-hydroxy-2-(pyridin-2-yl)-4H-chromen-4-one (1a). 1a has two tautomeric forms: one is 1a(O), which is induced by intramolecular hydrogen bond O-H?O=C, and the other one is 1a(N), which is caused by intramolecular hydrogen bond O-H?N. From excited state to tautomer excited state coming from ESIPT, the hydroxyl hydrogen breaks away and the dissociated hydrogen adsorbed on pyridinic nitrogen or carbonyl oxygen formed new intramolecular HB and the corresponding bond length and bond angle varied greatly. In comparison, a similar process of proton transfer for 1a(N)H+ protonated 1a(N) from ground state to excited state was obtained. This detailed proton transfer mechanism was provided by molecular orbitals analysis and it may be applied to molecular switch and organic Lewis acid/base. We investigated the excited state proton transfer mechanism of the four molecules through the theoretical method for the first time and gave unambiguous geometry of excited state. 相似文献
895.
A new mediator-free amperometric immunoassay for hepatitis B surface antigen (HBsAg) in human serum was designed by means
of immobilizing horseradish peroxidase-hepatitis B surface antibodies conjugates (HRP-HBsAb) on ionic liquids-doped organic-inorganic
hybrid film. The composite film including magnetic nanogold particles and nanoalumina particles provides a friendly microenvironment
for the immobilization of biomolecules. The presence of ionic liquids enhances the electron communication between the immobilized
biomolecules and the base electrode and improves the sensitivity of the electrochemical immunoassay. With a non-competitive
immunoassay format, the formation of the immunocomplex between the immobilized HRP-HBsAb and HBsAg in sample solution exhibited
a barrier of direct electrical communication between the immobilized HRP and the base electrode and changed the bioelectrocatalytic
properties of the immobilized HRP towards H2O2 in the detection solution. Under optimal conditions, the developed immunosensors displayed a good current response in a dynamic
range from 1.2 to 430 ng/mL with a limit of detection of 0.3 ng/mL HBsAg (at 3s). The proposed immunosensors have good precision, high sensitivity, acceptable stability, and reproducibility and could be
used for the HBsAg detection in human serum with consistent results in comparison with those obtained by the enzyme-linked
immunosorbent assay method. 相似文献
896.
Consistent invertibility and Weyl's theorem 总被引:1,自引:0,他引:1
Xiaohong Cao Hejia Zhang Yanhua Zhang 《Journal of Mathematical Analysis and Applications》2010,369(1):258-264
A Banach space operator T∈B(X) may be said to be “consistent in invertibility” provided that for each S∈B(X), TS and ST are either both or neither invertible. The induced spectrum contributes the conditions equivalent to various forms of “Weyl's theorem”. 相似文献
897.
An adaptive decision maker (ADM) is proposed for constrained evolutionary optimization. This decision maker, which is designed in the form of an adaptive penalty function, is used to decide which solution candidate prevails in the Pareto optimal set and to choose the individuals to be replaced. By integrating the ADM with a model of a population-based algorithm-generator, a novel generic constrained optimization evolutionary algorithm is derived. The performance of the new method is evaluated by 13 well-known benchmark test functions. It is shown that the ADM has powerful ability to balance the objective function and the constraint violations, and the results obtained are very competitive to other state-of-the-art techniques referred to in this paper in terms of the quality of the resulting solutions. 相似文献
898.
Rui Ma Zhibo Dong Yanhong Wei Xiaohong Zhan Yong Wang 《Crystal Research and Technology》2009,44(11):1197-1204
A coupled model was used to simulate columnar grain growth in TIG (tungsten inert‐gas) molten pool of nickel base alloy. The cellular automaton algorithm for dendritic growth is incorporated with solute transport model to take fluid flow into consideration. The results indicate that shear flow changes the solute distribution at the S/L (Solid/Liquid) interface, leading to asymmetrical growth of columnar grains. The dendrite arms on the upstream side grow fast, while the growth of dendrite arms on the downstream side is much delayed. However, dendrite arms on both sides are not as well‐developed as the grain growth without flow. With inlet flow velocity increasing, the phenomenon becomes more obvious. In addition, shear flow also results in more severe coring segregation. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
899.
900.
Yang Gao Xiaohong Shen Haoping Zheng 《International journal of quantum chemistry》2010,110(4):925-938
The equivalent potential of water for the electronic structure of asparagine(Asn) is constructed by using the first‐principles, all‐electron, ab initio calculation. The process is composed of three steps. The first step is to determine the geometric structure of Asn+nH2O system with a minimum energy. The second step is to calculate the electronic structure of Asn with the potential of water molecules by using the self‐consistent cluster‐embedding (SCCE) method, based on the result obtained in the first step. The last step is to calculate the electronic structure of Asn with the potential of dipole after replacing water molecules with dipoles. The results show that the major effect of water molecules on Asn' electronic structure be raising the occupied electronic states by 0.034 Ry on average and narrowing energy gap by 0.91%. The effect of water on the electronic structure of Asn can be well simulated by using dipole potential. The obtained equivalent potential can be applied directly to the electronic structure calculation of protein in solution by using the SCCE method. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 相似文献