全文获取类型
收费全文 | 75435篇 |
免费 | 23316篇 |
国内免费 | 17014篇 |
专业分类
化学 | 47831篇 |
晶体学 | 971篇 |
力学 | 4991篇 |
综合类 | 20篇 |
数学 | 9591篇 |
物理学 | 52361篇 |
出版年
2023年 | 669篇 |
2022年 | 648篇 |
2021年 | 563篇 |
2020年 | 812篇 |
2019年 | 1361篇 |
2018年 | 1332篇 |
2017年 | 1961篇 |
2016年 | 2107篇 |
2015年 | 2305篇 |
2014年 | 2145篇 |
2013年 | 3940篇 |
2012年 | 4218篇 |
2011年 | 5789篇 |
2010年 | 9163篇 |
2009年 | 9407篇 |
2008年 | 3294篇 |
2007年 | 2817篇 |
2006年 | 2519篇 |
2005年 | 2901篇 |
2004年 | 3829篇 |
2003年 | 3092篇 |
2002年 | 2899篇 |
2001年 | 3113篇 |
2000年 | 2334篇 |
1999年 | 2527篇 |
1998年 | 2143篇 |
1997年 | 1959篇 |
1996年 | 2289篇 |
1995年 | 2730篇 |
1994年 | 2800篇 |
1993年 | 2870篇 |
1992年 | 2457篇 |
1991年 | 2112篇 |
1990年 | 1774篇 |
1989年 | 1855篇 |
1988年 | 1865篇 |
1987年 | 1143篇 |
1986年 | 1194篇 |
1985年 | 882篇 |
1984年 | 1013篇 |
1982年 | 916篇 |
1981年 | 778篇 |
1980年 | 820篇 |
1979年 | 568篇 |
1978年 | 571篇 |
1977年 | 669篇 |
1976年 | 1075篇 |
1973年 | 460篇 |
1972年 | 540篇 |
1971年 | 444篇 |
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
161.
162.
163.
Toshiro Watanabe Tapan Kumar Mazumder Shiro Nagai Keisuke Tsuji Shigeru Terabe 《Analytical sciences》2003,19(1):159-161
A micellar electrokinetic chromatography (MEKC) method was developed for estimating the angiotensin-I converting enzyme (ACE) inhibitory activity by separating the hippuric acid liberated in the ACE reaction mixture in the presence of an inhibitor, captopril. The hippuric acid was successfully separated and detected by MEKC with a 25 mM sodium dodecyl sulfate solution in a 25 mM phosphate-50 mM borate buffer at pH 7.0; the total analysis took about 5 min. A good linear relationship was observed between the inhibitor and the peak area of hippuric acid release. No significant difference in the ACE inhibitory activity (IC50) of captopril (an antihypertensive medicine) or autolyzed-mushrooms (functional foods) was observed between the conventional method and the MEKC method. The MEKC method was found to be a useful technique for a rapid assay of the ACE inhibitory activity. 相似文献
164.
Solid state nuclear track detectors are commonly used for measurements of concentrations of radon gas and/or radon progeny. All these measurements depend critically on the thickness of the removed layer during etching. However, the thickness of removed layer calculated using the etching period does not necessarily provide a sufficiently accurate measure of the thickness. For example, the bulk etch rate depends on the strength of stirring during etching for the LR 115 detector. We propose here to measure the thickness of the removed layer by using energy-dispersive X-ray fluorescence spectrometry. In the present work, a reference silver nitrate pellet is placed beneath the LR 115 detector, and the fluorescence X-ray intensity for silver is then measured. We have found a linear relationship between the X-ray intensity and the thickness of the removed layer for LR 115 detector. This provides a fast method to measure the thickness of removed layer from etching of LR 115 detector. However, this method was found to be inapplicable for the CR-39 detector. Therefore, alternative methods have yet to be explored for the CR-39 detector. 相似文献
165.
碱蓝6B共振光散射法检测DNA 总被引:4,自引:0,他引:4
研究了碱蓝 6B与脱氧核糖核酸在酸性条件下共振光散射特征 ,考察了影响因素和最佳反应条件 ,建立了一种测定纳克级DNA的方法。在四硼酸钠 盐酸 (pH =2 90 )缓冲溶液中 ,线性范围为 10~ 10 0 4 μg·L- 1 ,相关系数为 0 9913,检出限为 4 2 μg·L- 1 ,用于合成样品的测定结果令人满意。 相似文献
166.
We have simultaneously used adsorption isotherm volumetry and Fourier transform infrared spectroscopy in order to take the investigations on amorphous ice structure a step further, especially concerning porosity and annealing-induced modifications. We have studied surface reorganization during annealing and found that the number of surface sites decreases before crystallization, their relative ratios being different for amorphous and crystalline ice. We also present results confirming that ice can have a large specific surface area and nevertheless be non-microporous. 相似文献
167.
Mid-infrared generation based on a periodically poled LiNbO3 optical parametric oscillator
下载免费PDF全文
![点击此处可从《中国物理》网站下载免费的PDF全文](/ch/ext_images/free.gif)
We report a nanosecond Nd:YVO_4-pumped optical parametric oscillator (OPO) based on periodically poled LiNbO_3 (PPLN). Tuning is achieved in this experiment by varying the temperature and period of the PPLN. The design of double-pass singly resonant oscillator (DSRO) and confocal cavity enables the OPO threshold to be lowered considerably, resulting in a simple, compact, all-solid-state configuration with the mid-infrared idler powers of up to 466mW at 3.41μm. 相似文献
168.
Characterizations of Tb:Zn2SiO4 films on silicon wafer prepared by sol-gel dip-coating and solid-phase reaction
下载免费PDF全文
![点击此处可从《中国物理》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Terbium-doped Zn_2SiO_4 films were successfully prepared on Si wafers by a simple sol-gel dip-coating and solid-phase reaction method of ZnO and SiO_2. X-ray diffraction (XRD) and UV-Vis absorption results revealed that films processed below 850℃ were ZnO in wurzite structure, and films processed above 850℃ were Zn_2SiO_4 in wellimite structure. Photoluminescence measurements of the Tb-doped Zn_2SiO_4 films showed two strong emission bands at 490 and 545nm. The photoluminescence lifetime was 4.6ms. 相似文献
169.
170.