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531.
532.
Closed-vessel microwave digestion of nine standard reference plant materials (NIST, BCR, IAEA) and a laboratory standard of plant material with different Si contents assisted by HNO3 + H2O2 (procedure A), HNO3 + H2O2 + HF + H3BO3 (procedure B) and HNO3 + H2O2 + HBF4 (procedure C) were used to determine the recovery of 36 elements by ICP-MS: Ag, Al, As, Ba, Be, Bi, Cd, Ce, Co, Cr, Cs, Cu, Fe, Ga, Ge, In, La, Li, Mn, Mo, Nd, Ni, Pb, Pr, Rb, Sb, Se, Sn, Sr, Th, Tl, U, V, W, Y, Zn. Additions of HF + H3BO3 and HBF4 in procedures B and C exceeded by 10% (B1, C1) and 100% (B2, C2) the equivalent concentrations of Si in the samples determined by ICP-OES. Most recoveries of certified elements (e.g., Al*, Cu, Mo*, Rb*, Sb*, Th) decreased significantly (*p ≤ 0.05) with increasing Si content in plant reference materials digested by procedure A, while the recoveries from procedures B and C decreased insignificantly only for Mo and Sb. Digestions B and C gave significantly higher recoveries of Al, Sb, W and REEs, which were tighter to the reference values of these elements. A similar effect was found for Cu, Fe, Li, Ni, Sn, Th, Tl, V, Zn, Ba, Rb and Sr recoveries in samples with Si contents exceeding 2000 μg g−1. If the Si content in plant samples is less than 10 mg g−1, digestion of 0.5 g of plant samples through 0.05 mL of HF and 0.5 mL of 4% H3BO3 or 0.1 mL of HBF4 is recommended to get satisfactory results for most of the elements. For materials with Si content exceeding 10 mg g−1 the weight of the sample for digestion should be reduced to 0.25 g. However, the operation of potential interferences should be taken into account and eliminated through correction equations and adequate dilution of the samples. 相似文献
533.
Based on the analysis of Adaptive Moving Target Indication(AMTI) and the signal processing of Synthetic Aperture Radar(SAR), a complete compatible system of AMTI and SAR is put forward. The compatibility and effectiveness of this system is prcved in theory. The results of simulation show that this system not only has good ability in stationary targets imaging but also has ability in detecting moving targets under the background of strong clutter. 相似文献
534.
N. Majcen 《Accreditation and quality assurance》2003,8(3-4):108-112
The fact that various definitions and terminology applied to measurements in analytical chemistry are not always consistent
and straightforward, by not only answering the question ”what”, but also ”how”, leads to their various interpretations. This
results in non-uniform implementation of very basic and essential metrological principles in chemistry. Such a diverse situation
is not conducive to the endorsement of harmonised measurements all across the world, to serve as a tool for improving the
quality of life in its broadest sense for all its citizens. The discussion in this paper is focused on problems associated
with terminology and definitions of ’reference material’ and ’validation’. The role of reference materials in measurement
processes for purposes other than calibration and validation principles in analytical chemistry are also discussed in this
paper. Where possible, potential solutions are proposed, but more often, questions of essential importance are raised in order
to initiate international discussion which will hopefully lead to equally understandable answers.
Received: 2 November 2002 Accepted: 3 February 2003
Acknowledgements
The author is grateful to Aleš Fajgelj for his comprehensive comments on the topic described in this paper. Sincere thanks
also to Philip Taylor, Ewa Bulska, Emilia Vassileva, Miloslav Suchanek and Margreet Lauwaars for their contribution during
fruitful discussions on validation.
Presented at the CERMM-3, Central European Reference Materials and Measurements Conference: The function of reference materials
in the measurement process, May 30–June 1, 2002, Rogaška Slatina, Slovenia
Correspondence to N. Majcen 相似文献
535.
536.
Measurement traceability is universally recognised as one of the basic prerequisites for comparability of results obtained in different laboratories and is a basic aspect of metrological sciences such as analytical chemistry. This requirement is underscored by the increasing adoption of standards and measurement quality systems, such as laboratory accreditation against ISO/IEC 17025. Testing laboratories ensure traceability of their measurement results by using appropriate reference standards for calibration of instruments and control of measurement processes. For routine work in the field of water analysis, these standards are usually commercial solutions or in-house solutions prepared from pure products. Therefore, laboratories should demonstrate that their use of reference standards is appropriate and sufficient, which can be done by participation in an appropriate proficiency-testing scheme. The paper reports how measurement traceability of results from field laboratories (nitrite nitrogen, nitrate nitrogen, chloride and sulphate; all in water) can be demonstrated by participation in a proficiency-testing scheme based on reference values. 相似文献
537.
The effect of matrix contents on the detection limit of total reflection X-ray fluorescence analysis was experimentally investigated using a set of multielement standard solutions (500 ng/mL of each element) in variable concentrations of NH4NO3. It was found that high matrix concentration, i.e. 0.1–10% NH4NO3, had a strong effect on the detection limits for all investigated elements, whereas no effect was observed at lower matrix concentration, i.e. 0–0.1% NH4NO3. 相似文献
538.
The concept of adequacy of reference materials (RMs) to samples under analysis is discussed. It is emphasized that effectiveness of RM as a measurement standard can depend dramatically on assessment of the RM adequacy. A score is proposed for quantitative adequacy evaluation that formalizes the existing analytical knowledge. The score is based on the comparison of the compositions and physico-chemical parameters of RM with those of a sample, choosing the parameters influencing the analytical results. The score allows us to find the most adequate RM before analysis, using RM catalogues and prior information about the sample and analytical method. 相似文献
539.
本文介绍了基准试剂纯度定值装置的工作原理,研究制作了用于反映库仑滴定终点的终点指示器,并对基准试剂的纯度分析方法进行了研究,使定值精度达到了国内外先进水平。 相似文献
540.
Mary M. Kimberly 《Accreditation and quality assurance》2004,9(4-5):239-241
In 1968, clinical chemistry was considered to be the field most in need of certified reference materials (CRMs). While significant progress has been made in this area, new diagnostic assays are continually being developed that create a need for new CRMs. Members of the clinical laboratory community help to identify reference material needs. Professional and governmental organizations, such as IFCC, AACC, NCCLS, CDC, and the national metrological institutes (NMIs), respond to develop protocols and materials. Several measurands are presented as examples. In the late 1950s and early 1960s, in response to a need for standardization of lipid and lipoprotein measurements, CDC developed a reference system that included secondary reference materials. Over the years, the process of preparation of these materials was refined, eventually leading to the development of NCCLS guideline for preparation of commutable frozen serum pools for use as secondary reference materials (C37-A). This protocol was used for the preparation of NIST SRM 1951a (lipids in frozen (liquid) human serum). In the 1980s, a need for a reference material for blood lead was identified. CDC and NIST cooperated to develop SRM 955 (lead in bovine blood). More recently, efforts have been initiated to standardize high-sensitivity C-reactive protein (hsCRP) assays. In this case, a CRM for CRP existed (CRM 470, developed by IFCC and available from IRMM), but at concentrations in the acute phase reactant range and not in the low range needed for hsCRP assays. CDC coordinated a study to evaluate diluted CRM470 and other candidate materials as secondary reference materials for hsCRP assays.Presented at BERM-9—Ninth International Symposium on Biological and Environmental Reference Materials, June 15–19, 2003, Berlin, Germany. 相似文献