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71.
72.
Wolfram W. Rudolph 《Journal of solution chemistry》2010,39(7):1039-1059
Measurements have been made of the Raman spectra of aqueous solutions of Be(ClO4)2, BeCl2, (NH4)2SO4 and BeSO4 to 50 cm−1. In some cases low concentrations (0.000770 mol⋅kg−1) have been used and two temperatures (23 and 40 °C) were studied. In BeSO4(aq), the ν
1-SO42-\mathrm{SO}_{4}^{2-} mode at 980 cm−1 broadens with increasing concentration and shifts to higher wavenumbers. At the same time, a band at 1014 cm−1 is detectable with this mode being assigned to [BeOSO3], an inner-sphere complex (ISC). Confirmation of this assignment is provided by the simultaneous appearance of stretching
bands for the Be2+-OSO32-\mathrm{Be}^{2+}\mbox{-}\mathrm{OSO}_{3}^{2-} bond of the complex at 240 cm−1 and for the BeO4 skeleton mode of the [(H2O)3BeOSO3] unit at 498 cm−1. The ISC concentration increases with higher temperatures. The similarity of the n1-SO42-\nu_{1}\mbox{-}\mathrm{SO}_{4}^{2-} Raman bands for BeSO4 in H2O and D2O is further strong evidence for formation of an ISC. After subtraction of the ISC component at 1014 cm−1, the n1-SO42-\nu_{1}\mbox{-}\mathrm{SO}_{4}^{2-} band in BeSO4(aq) showed systematic differences from that in (NH4)2SO4(aq). This is consistent with a n1-SO42-\nu_{1}\mbox{-}\mathrm{SO}_{4}^{2-} mode at 982.7 cm−1 that can be assigned to the occurrence of an outer-sphere complex ion (OSCs). These observations are shown to be in agreement
with results derived from previous relaxation measurements. Infrared spectroscopic data show features that are also consistent
with a beryllium sulfato complex such as the appearance of a broad and weak n1-SO42-\nu_{1}\mbox{-}\mathrm{SO}_{4}^{2-} mode at ∼1014 cm−1, normally infrared forbidden, and a broad and asymmetric n3-SO42-\nu_{3}\mbox{-}\mathrm{SO}_{4}^{2-} band contour which could be fitted with four band components (including n3-SO42-(aq)\nu_{3}\mbox{-}\mathrm{SO}_{4}^{2-}(\mathrm{aq})). The formation of ISCs in BeSO4(aq) is much more pronounced than in the similar MgSO4(aq) system studied recently. 相似文献
73.
Rosemarie Philipp Olaf Hanebeck Sebastian Hein Wolfram Bremser Tin Win Irene Nehls 《Accreditation and quality assurance》2010,15(3):141-146
The Federal Institute for Materials Research and Testing (BAM), Germany, has issued a series of large volume ethanol in water
certified reference materials (CRMs), primarily developed for the calibration of evidential breath alcohol analyzers in Germany.
The certified parameter is the ethanol mass concentration at 20 °C. When used in a wet bath simulator, the solutions deliver
gas samples that meet the requirements set by the Organization of Legal Metrology for calibration of breathalyzers. The materials
were prepared gravimetrically by spiking of ethanol into water in single 5 L units. A complete uncertainty budget for the
preparation process has been established. The purity of the commercial ethanol stock solution was identified to be the main
source of uncertainty. For stability and homogeneity measurements and for the verification of the gravimetric mass concentration
of the CRMs, a robust high-precision gas chromatography, with flame-ionization detection method for ethanol determination
in aqueous samples was developed and validated. The good performance of this method has been demonstrated in several international
comparisons organized by the Consultative Committee for Amount of Substance—Metrology in Chemistry at the International Bureau
of Weights and Measures. 相似文献
74.
75.
Technical systems are subjected to a variety of excitations that cannot generally be described in deterministic ways. Random excitations such as road roughness, wind gusts or loads on marine structures are commonly described by stochastic differential equations (SDEs). Given a set of SDEs, the main task is in finding probability density functions (PDFs), which yield statistical information about the system states. Monte-Carlo simulations represent a general way of generating PDFs, however, reliable integration methods can be time-consuming for complex systems. An alternative way of finding PDFs lies in the analysis of the Fokker-Planck equation, a partial differential equation of the PDF. Linear problems under Gaussian excitation can be solved analytically, which is the case only for a small class of nonlinear problems. As a result, there are a number of methods of approximating PDFs for general problems. Most of these are restricted to comparably low dimensions, such as d=4 ("curse of dimensionality"), limiting the relevance to technical applications. This paper presents solutions to problems of dimensions up to d=10, applying a Galerkin-method that expands approximate solutions into orthogonal polynomials. Problems include polynomial nonlinearities in damping and restoring terms, such as classical Duffing-elements, as well as other types of nonlinearities, demonstrated on a typical problem in vehicle dynamics. All results are compared with results from Monte-Carlo simulations or exact solutions, where available. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
76.
Guided by classical concepts, we define the notion of ends of an iterated function system and prove that the number of ends is an upper bound for the number of nondegenerate components of its attractor. The remaining isolated points are then linked to idempotent maps. A commutative diagram illustrates the natural relationships between the infinite walks in a semigroup and components of an attractor in more detail. We show in particular that, if an iterated function system is one-ended, the associated attractor is connected, and ask whether every connected attractor (fractal) conversely admits a one-ended system. 相似文献
77.
A group is called a T-group if all of its subnormal subgroups are normal. In this note we consider the following question: Assume that G is a polycyclic group. What can be said about G if all finite epimorphic images H of G satisfy one of the following conditions: (i) H is a T-group,(ii) \({H/\Phi (H)}\) is a T-group,(iii) H/Z *(H) is a T-group. We will see that the prime 2 will play a particular role in (ii) and (iii), see Theorems C and D. 相似文献
78.
Steven J. Granger Roland Bol Wolfram Meier‐Augenstein Melanie J. Leng Helen F. Kemp Tim H. E. Heaton Sue M. White 《Rapid communications in mass spectrometry : RCM》2010,24(5):475-482
Stable isotopes of water have been previously used in catchment studies to separate rain‐event water from pre‐event groundwater. However, there are a lack of studies at the smaller scale looking at the separation of event water from pre‐event water. This is particularly relevant for heavy clay soil systems through which the movement of water is uncertain but is thought to be rainwater‐dominated. The data presented here were collected at a rural site in the south‐west of England. The historic rainfall at the site was isotopically varied but similar to the global meteoric water line, with annual weighted means of ?37‰ for δ2H and ?5.7‰ for δ18O and with no seasonal variation. Drainage was sampled from the inter‐flow (surface runoff + lateral through‐flow) and drain‐flow (55 cm deep mole drains) pathways of two 1 ha lysimeters during two rainfall events, which had δ2H values of ?68‰ and ?92‰, respectively. The δ2H values of the lysimeter drainage water suggest that there was no contribution of event water during the first, small discharge (Q) event; however, the second larger event did show isotopic variation in δ2H values negatively related to Q indicating that rainwater was contributing to Q. A hydrograph separation indicated that only 49–58% of the inter‐flow and 18–25% of the drain‐flow consisted of event water. This was surprising given that these soil types are considered retentive of soil water. More work is needed on heavy clay soils to understand better the nature of water movement from these systems. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
79.
Matthias Koch Wolfram Bremser Robert K?ppen Rita Kr��ger Tatjana Rasenko David Siegel Irene Nehls 《Accreditation and quality assurance》2011,16(8-9):429-437
Mycotoxins are important non-anthropogenic food and feed contaminants, which can be present on almost every agricultural commodity. Effective consumer protection therefore essentially depends on food surveillance by reliable quantitative analysis enabled by appropriate quality control. Certified (matrix) reference materials (CRMs) are versatile tools to support quality assurance. However, in the case of ochratoxin A (OTA), a hepato- and nephrotoxic mycotoxin, which is regulated in various foods, there is a lack of suitable CRMs. This lack has now been overcome by the development of two European Reference Materials (ERM?) for the determination of OTA in roasted coffee (ERM?-BD475) and red wine (ERM?-BD476). This article discusses the material preparation process as well as the results of homogeneity and stability testing. Furthermore, the results of the in-house certification studies carried out at BAM Federal Institute for Materials Research and Testing are presented and discussed. Interlaboratory comparison studies involving selected expert laboratories with documented expertise in the field of mycotoxin analysis were conducted to confirm the certified values determined by BAM. The certified ochratoxin A values and their corresponding expanded uncertainties (k?=?2) were assigned in full compliance with the requirements of ISO Guide 35 and are as follows: (6.0?±?0.6)???g?kg?1 for roasted coffee, ERM?-BD475, and (0.52?±?0.11)???g?L?1 for red wine, ERM?-BD476. 相似文献
80.