全文获取类型
收费全文 | 202183篇 |
免费 | 2238篇 |
国内免费 | 502篇 |
专业分类
化学 | 110715篇 |
晶体学 | 3651篇 |
力学 | 7996篇 |
综合类 | 11篇 |
数学 | 19198篇 |
物理学 | 63352篇 |
出版年
2020年 | 1733篇 |
2019年 | 1924篇 |
2018年 | 2243篇 |
2017年 | 2355篇 |
2016年 | 3528篇 |
2015年 | 2205篇 |
2014年 | 3558篇 |
2013年 | 9082篇 |
2012年 | 6527篇 |
2011年 | 8028篇 |
2010年 | 5705篇 |
2009年 | 5657篇 |
2008年 | 7175篇 |
2007年 | 7076篇 |
2006年 | 6701篇 |
2005年 | 6059篇 |
2004年 | 5529篇 |
2003年 | 5105篇 |
2002年 | 4878篇 |
2001年 | 6143篇 |
2000年 | 4629篇 |
1999年 | 3518篇 |
1998年 | 2746篇 |
1997年 | 2704篇 |
1996年 | 2593篇 |
1995年 | 2440篇 |
1994年 | 2330篇 |
1993年 | 2167篇 |
1992年 | 2826篇 |
1991年 | 2732篇 |
1990年 | 2674篇 |
1989年 | 2690篇 |
1988年 | 2713篇 |
1987年 | 2721篇 |
1986年 | 2591篇 |
1985年 | 3303篇 |
1984年 | 3313篇 |
1983年 | 2598篇 |
1982年 | 2709篇 |
1981年 | 2763篇 |
1980年 | 2533篇 |
1979年 | 2875篇 |
1978年 | 2860篇 |
1977年 | 2980篇 |
1976年 | 2816篇 |
1975年 | 2553篇 |
1974年 | 2510篇 |
1973年 | 2465篇 |
1972年 | 1702篇 |
1968年 | 1703篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
V. V. Sagaradze N. V. Kataeva V. A. Zavalishin K. A. Kozlov V. V. Makarov A. R. Kuznetsov 《哲学杂志》2020,100(14):1868-1879
ABSTRACT The authors present the results of an investigation in Fe–Ni-Cr austenitic alloys of the low-temperature deformation-induced segregations of nickel that form in the micro regions being (i) located close to grain- and subgrain boundaries and (ii) characteristic of the concentration and magnetic inhomogeneities indicated by the appearance of a dark diffraction contrast at the electron diffraction patterns taken from these regions typical (at the same time) of an enhanced value of Curie temperature. The observed effects were connected with the micro distortions caused by the local change of lattice parameter because of an increase in nickel concentration, as well as in the result of a magnetostriction dilatation. Using methods of the X-ray energy dispersive spectroscopy (XEDS) and atomic-probe body-section radiography (tomography – APT) has made it possible to determine the borders of those regions of austenite that were characteristic of an enhanced concentration of nickel in the fields of the localisation of a deformation-induced segregation of nickel in the vicinity of grain (subgrain) boundaries of austenitic alloys of the types Fe–13Cr–30Ni and Fe–37Ni–3Ti. 相似文献
12.
13.
14.
Manjumol K. A. Jayasankar M. Vidya K. Mohamed A. Peer Nair Balagopal N. Warrier K. G. K. 《Journal of Sol-Gel Science and Technology》2015,74(1):161-167
Journal of Sol-Gel Science and Technology - High temperature stable brookite rich titanium dioxide of average crystallite size 20&;nbsp;nm has been prepared by a novel aqueous sol–gel... 相似文献
15.
Saleh Z. M. Nasser H. Özkol E. Günöven M. Abak K. Canli S. Bek A. Turan R. 《Journal of nanoparticle research》2015,17(10):1-12
Journal of Nanoparticle Research - Plasmonic interfaces consisting of silver nanoparticles of different sizes (50–100&;nbsp;nm) have been processed by the self-assembled dewetting... 相似文献
16.
Development and validation of a reversed‐phase HPLC method for CYP1A2 phenotyping by use of a caffeine metabolite ratio in saliva 下载免费PDF全文
Elias Begas Evangelos Kouvaras Andreas K. Tsakalof Maria Bounitsi Eftihia Konstadinos Asprodini 《Biomedical chromatography : BMC》2015,29(11):1657-1663
CYP1A2 is important for metabolizing various clinically used drugs. Phenotyping of CYP1A2 may prove helpful for drug individualization therapy. Several HPLC methods have been developed for quantification of caffeine metabolites in plasma and urine. Aim of the present study was to develop a valid and simple HPLC method for evaluating CYP1A2 activity during exposure in xenobiotics by the use of human saliva. Caffeine and paraxanthine were isolated from saliva by liquid‐liquid extraction (chlorophorm/isopropanol 85/15v/v). Extracts were analyzed by reversed‐phase HPLC on a C18 column with mobile phase 0.1% acetic acid/methanol/acetonitrile (80/20/2 v/v) and detected at 273nm. Caffeine and paraxanthine elution times were <13min with no interferences from impurities or caffeine metabolites. Detector response was linear (0.10–8.00µg/ml, R2>0.99), recovery was >93% and bias <4.47%. Intra‐ and inter‐day precision was <5.14% (n=6). The limit of quantitation was 0.10µg/ml and the limit of detection was 0.018±0.002µg/mL for paraxanthine and 0.032±0.002µg/ml for caffeine. Paraxanthine/caffeine ratio of 34 healthy volunteers was significantly higher in smokers (p<0.001). Saliva paraxanthine/caffeine ratios and urine metabolite ratios were highly correlated (r=0.85, p<0.001). The method can be used for the monitoring of CYP1A2 activity in clinical practice and in studies relevant to exposure to environmental and pharmacological xenobiotics. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
17.
18.
19.
20.