全文获取类型
收费全文 | 14155篇 |
免费 | 1082篇 |
国内免费 | 1292篇 |
专业分类
化学 | 10269篇 |
晶体学 | 41篇 |
力学 | 237篇 |
综合类 | 104篇 |
数学 | 303篇 |
物理学 | 5575篇 |
出版年
2024年 | 39篇 |
2023年 | 237篇 |
2022年 | 465篇 |
2021年 | 472篇 |
2020年 | 415篇 |
2019年 | 438篇 |
2018年 | 348篇 |
2017年 | 564篇 |
2016年 | 575篇 |
2015年 | 585篇 |
2014年 | 792篇 |
2013年 | 848篇 |
2012年 | 1089篇 |
2011年 | 971篇 |
2010年 | 784篇 |
2009年 | 992篇 |
2008年 | 931篇 |
2007年 | 949篇 |
2006年 | 828篇 |
2005年 | 715篇 |
2004年 | 616篇 |
2003年 | 390篇 |
2002年 | 328篇 |
2001年 | 229篇 |
2000年 | 212篇 |
1999年 | 238篇 |
1998年 | 184篇 |
1997年 | 192篇 |
1996年 | 134篇 |
1995年 | 146篇 |
1994年 | 102篇 |
1993年 | 109篇 |
1992年 | 105篇 |
1991年 | 71篇 |
1990年 | 82篇 |
1989年 | 52篇 |
1988年 | 60篇 |
1987年 | 52篇 |
1986年 | 35篇 |
1985年 | 31篇 |
1984年 | 23篇 |
1983年 | 17篇 |
1982年 | 34篇 |
1981年 | 17篇 |
1980年 | 9篇 |
1979年 | 12篇 |
1978年 | 4篇 |
1973年 | 2篇 |
1971年 | 2篇 |
1959年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
A highly sensitive fluorescence quenching method for the determination of silicate based on the formation of an ion associate between molybdosilicate and Rhodamine B (RB) in nitric acid medium was developed. A flow injection system coupled with a fluorescence detector was used for the measurement of fluorescence intensity at 560 and 580 nm as excitation and emission wavelengths, respectively. The calibration graph for Si showed a linear range of 0.1–5 ng cm−3 with correlation coefficient of 0.9999, and the detection limit of 0.06 ng cm−3. The proposed method was successfully applied to the determination of silicate in ultrapurified water with satisfactory results. 相似文献
82.
毛细管电泳安培检测扑热息痛及其水解物 总被引:1,自引:0,他引:1
研究了各种电化学预处理条件下碳纤维电极对扑热息痛及水解物的电化学行为。确定该体系最佳预处理条件为0.2V电位下阳极化1min,再于-2.0V下阴极化10s。预处理后的碳纤维伏安响应得到明显提高。运用最佳条件并在支持电解中加入添加剂后,扑热息痛及其水解物在毛细管电泳上获得很好的分离和检测。其中扑热息痛的检测下限为2.78pg;对氨基酚为1.84pg。 相似文献
83.
84.
在聚乙烯醇存在下,用罗丹明B-Mo(V)-SCN~-荧光熄灭法测Mo,能消除过量的SCN-对罗丹明B的熄灭作用。加入聚乙烯醇后体系的荧光熄灭倍数比未加入时大14倍。此法灵敏度高、稳定性好、操作简便,检测下限0.12ng/ml Mo.可用于测水和头发中的钼。 相似文献
85.
Dolashka-Angelova P Hristova R Stoeva S Voelter W 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》1999,55(14):2927-2934
Hemocyanin (Hc) of Carcinus aestuarii contains three major and one minor electrophoretically separable polypeptide chains which were purified by fast protein liquid chromatography (FPLC) ion exchange chromatography. N-terminal amino acid sequences of four structural subunits (SSs) from C. aestuarii were compared with known N-terminal sequences from other arthropodan hemocyanins. The conformational changes, induced by various treatments, were monitored by far UV, CD and fluorescence spectroscopy. The critical temperatures for the structural subunits, Tc, determined by fluorescence spectroscopy, are in the region of 52-59 degrees C and coincide with the melting temperatures, Tm (49-55 degrees C), determined by CD spectroscopy. The free energy of stabilization in water, delta GDH2O, toward guanidinium hydrochloride is about 1.3 times higher for the dodecameric Hc as compared to the isolated subunits and about one time higher for Cal, comparing with other SSs. The studies reveal that the conformational stability of the native dodecamer towards various denaturants (temperature and guanidinium hydrochloride) indicate that the quaternary structure is stabilized by oligomerization between structural subunits, and the possibility of a structural role of the sugar mojeties cannot be excluded. 相似文献
86.
聚电解质溶液中2.6-ANS探针的荧光谱研究 总被引:1,自引:0,他引:1
本文合成了2.6—ANS荧光探针分子,并在含有不同外加盐的NaPSS溶液中测定了探针的荧光发射光谱。结果表明:探针的荧光强度随Cs增大而增大,而探针光谱的最大发射波长和半波宽度随Cs增大而减小。当Cs达到一定值时,荧光谱参数与Cs关系曲线出现转折点,此时聚离了链以“类胶束”状态存在。 相似文献
87.
A portable chip-CE system with potential gradient detection (PGD) was developed and applied to the determinations of alkali metals and alkaloids. The separation efficiency appeared to be satisfactory and nonaqueous capillary electrophoresis (NACE) proved to be applicable to PGD or conductivity detection. The power supplies, separation and detection were built on a device of 3 kg in weight. A branch channel near the end of the separation channel was designed to perform PGD and make the application of relatively high field strength possible. The study is the first report on the application of PGD on the microchip platform. The design of the chip-CE system shows several advantages, such as simplicity, miniaturization and wide applicability. 相似文献
88.
89.
对NO生理作用的新认识及其电化学实时检测 总被引:8,自引:0,他引:8
本文综述了近年来学术界对NO生理作用的新认识,并介绍了现场实时检测生物活体中释放的NO浓度的电化学方法. 相似文献
90.