全文获取类型
收费全文 | 13574篇 |
免费 | 307篇 |
国内免费 | 53篇 |
专业分类
化学 | 9468篇 |
晶体学 | 65篇 |
力学 | 238篇 |
数学 | 2435篇 |
物理学 | 1728篇 |
出版年
2020年 | 133篇 |
2016年 | 233篇 |
2015年 | 217篇 |
2014年 | 194篇 |
2013年 | 465篇 |
2012年 | 421篇 |
2011年 | 512篇 |
2010年 | 315篇 |
2009年 | 324篇 |
2008年 | 479篇 |
2007年 | 510篇 |
2006年 | 452篇 |
2005年 | 504篇 |
2004年 | 450篇 |
2003年 | 368篇 |
2002年 | 351篇 |
2001年 | 180篇 |
2000年 | 196篇 |
1999年 | 183篇 |
1998年 | 165篇 |
1997年 | 207篇 |
1996年 | 207篇 |
1995年 | 207篇 |
1994年 | 195篇 |
1993年 | 198篇 |
1992年 | 201篇 |
1991年 | 172篇 |
1990年 | 149篇 |
1989年 | 181篇 |
1988年 | 210篇 |
1987年 | 176篇 |
1986年 | 197篇 |
1985年 | 253篇 |
1984年 | 222篇 |
1983年 | 190篇 |
1982年 | 236篇 |
1981年 | 220篇 |
1980年 | 217篇 |
1979年 | 214篇 |
1978年 | 192篇 |
1977年 | 189篇 |
1976年 | 178篇 |
1975年 | 168篇 |
1974年 | 178篇 |
1973年 | 171篇 |
1971年 | 130篇 |
1961年 | 159篇 |
1960年 | 213篇 |
1959年 | 125篇 |
1958年 | 136篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
Richard A. Reid Walter A. StarkJr 《The Journal of the Operational Research Society》1988,39(2):135-139
Individual/group replacement models were used to identify the minimum-cost policy for replacing protective gloves that are utilized in product fabrication at a nuclear processing facility. Since historical data on glove longevity were not available to determine the failure-rate distribution, the classical replacement model for items that fail was modified to consider glove life as a normally distributed variable. Moreover, the absence of replacement-cost required that the classical model be transformed to incorporate the ratio of single to unit-group replacement cost. Sensitivity analysis on these two input parameter values provided guidance for the development of an appropriate replacement policy. 相似文献
92.
Elliott H. Lieb Israel M. Sigal Barry Simon Walter Thirring 《Communications in Mathematical Physics》1988,116(4):635-644
LetN(Z) denote the number of electrons which a nucleus of chargeZ can bind in non-relativistic quantum mechanics (assuming that electrons are fermions). We prove thatN(Z)/Z1 asZ.Research partially supported by the NSERC under Grant NA7901 and by the USNSF under Grants DMS-8416049 and PHY 85-15288-A01 相似文献
93.
Walter Selig 《Fresenius' Journal of Analytical Chemistry》1969,247(5-6):294-296
Summary A new complexometric method for the determination of phosphorus in organic compounds is described. After combustion in an oxygen-flask, phosphorus is precipitated as cerous phosphate. The excess cerous ion is back-titrated at pH 6–7 with EDTA in the presence of methylthymol blue or xylenol orange indicators. Alkaline hypobromite is used as an absorbent. Tight clamping of the paper carrier in the platinum holder insures complete combustion.
This work was performed under the auspices of the U.S. Atomic Energy Commission. 相似文献
Komplexometrische Titration von Phosphor in organischen Verbindungen
Zusammenfassung Die Probe wird im Sauerstoffkolben nach Schöniger verbrannt und der Phosphor als Cer(III)-phosphat ausgefällt. Der Überschuß an Cer(III) wird bei pH 6–7 mit ÄDTA zurücktitriert, wobei Methylthymolblau oder Xylenolorange als Indicator dient. Als Absorptionsmittel wird alkalische Hypobromitlösung verwendet. Um eine vollständige Verbrennung zu gewährleisten, ist es wichtig, daß das Papier mit der Probe fest am Platinhalter angeklammert wird.
This work was performed under the auspices of the U.S. Atomic Energy Commission. 相似文献
94.
Daniela Stllner Walter Stcklein Frieder Scheller Axel Warsinke 《Analytica chimica acta》2002,470(2):3438-119
An amperometric immunosensor for hemoglobin-A1c (HbA1c) determination has been developed utilizing membrane-immobilized haptoglobin as affinity matrix fixed in front of a Pt-working electrode. The HbA1c assay was carried out in a two-step procedure including the selective hemoglobin enrichment on the sensor surface and the specific HbA1c detection by a glucose oxidase (GOx) labeled anti-HbA1c antibody. Hydrogen peroxide generated by the enzyme label was oxidized at +600 mV versus Ag/AgCl. A standard curve for HbA1c was obtained with a linear range between 0 and 25% HbA1c of total hemoglobin which correspond to 7.8–39 nM. ELISA studies confirmed the advantage of a sandwich-type format with haptoglobin as capture molecule for selective hemoglobin binding over the direct adsorption method. Results by the sandwich immunoassay showed a linear correlation within the clinically relevant range 5–20% (CV < 3). For sensor application the immobilization procedure of haptoglobin onto CDI-activated cellulose membranes was optimized. 相似文献
95.
Pure-silica optical waveguides, fiber couplers, and high-aspect ratio submicrometer channels for electrokinetic separation devices 总被引:1,自引:0,他引:1
Mogensen KB Eriksson F Gustafsson O Nikolajsen RP Kutter JP 《Electrophoresis》2004,25(21-22):3788-3795
A new fabrication procedure for integration of ultraviolet transparent pure-silica planar waveguides, fiber couplers and high-aspect ratio submicrometer channels is presented. Only a single photolithographic mask step is required. The channels are 80-90 microm deep and the width can be reduced to about 0.5 microm, corresponding to a height-to-width ratio of more than 150. The core of the waveguides consists of pure silicon dioxide, which is favorable over doped silica, due to the absence of absorption centers associated with the dopants. This furthermore improves the long-term stability of the waveguides, because of an increased radiation resistance of the glass. The propagation loss decreases from 1.0 dB/cm at 200 nm to 0.2 dB/cm at 800 nm, which, to our knowledge, is the lowest propagation loss reported for integrated planar waveguides in the ultraviolet wavelength region to date. The effective optical path length is 1.2 mm for an absorbance cell with a nominal length of 1.0 mm, indicating effective suppression of stray light. The limit of detection for paracetamol when present in the entire channel network was determined to 3 microg/mL. Finally, the applicability of the fabricated devices for capillary electrophoresis was evaluated by separation of caffein, paracetamol and ketoprofone using absorbance detection at 254 nm. 相似文献
96.
97.
98.
99.
100.