全文获取类型
收费全文 | 38189篇 |
免费 | 6174篇 |
国内免费 | 4569篇 |
专业分类
化学 | 27839篇 |
晶体学 | 437篇 |
力学 | 2188篇 |
综合类 | 402篇 |
数学 | 4243篇 |
物理学 | 13823篇 |
出版年
2024年 | 120篇 |
2023年 | 786篇 |
2022年 | 1278篇 |
2021年 | 1342篇 |
2020年 | 1599篇 |
2019年 | 1597篇 |
2018年 | 1263篇 |
2017年 | 1148篇 |
2016年 | 1825篇 |
2015年 | 1794篇 |
2014年 | 2116篇 |
2013年 | 2670篇 |
2012年 | 3327篇 |
2011年 | 3275篇 |
2010年 | 2299篇 |
2009年 | 2175篇 |
2008年 | 2441篇 |
2007年 | 2210篇 |
2006年 | 2032篇 |
2005年 | 1738篇 |
2004年 | 1428篇 |
2003年 | 1276篇 |
2002年 | 1288篇 |
2001年 | 1124篇 |
2000年 | 878篇 |
1999年 | 904篇 |
1998年 | 675篇 |
1997年 | 589篇 |
1996年 | 572篇 |
1995年 | 512篇 |
1994年 | 437篇 |
1993年 | 398篇 |
1992年 | 349篇 |
1991年 | 314篇 |
1990年 | 304篇 |
1989年 | 199篇 |
1988年 | 146篇 |
1987年 | 105篇 |
1986年 | 123篇 |
1985年 | 86篇 |
1984年 | 55篇 |
1983年 | 47篇 |
1982年 | 39篇 |
1981年 | 23篇 |
1980年 | 9篇 |
1979年 | 8篇 |
1976年 | 1篇 |
1959年 | 1篇 |
1957年 | 4篇 |
1936年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
The Effect of the Spacer of Bis(biurea) Ligands on the Structure of A2L3‐type (A=anion) Phosphate Complexes 下载免费PDF全文
Prof. Biao Wu Dr. Shaoguang Li Prof. Yibo Lei Prof. Huaiming Hu Dr. Nader de Sousa Amadeu Prof. Dr. Christoph Janiak Dr. Jennifer S. Mathieson Dr. De‐Liang Long Prof. Leroy Cronin Prof. Xiao‐Juan Yang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(6):2588-2593
By tuning the length and rigidity of the spacer of bis(biurea) ligands L, three structural motifs of the A2L3 complexes (A represents anion, here orthophosphate PO43?), namely helicate, mesocate, and mono‐bridged motif, have been assembled by coordination of the ligand to phosphate anion. Crystal structure analysis indicated that in the three complexes, each of the phosphate ions is coordinated by twelve hydrogen bonds from six surrounding urea groups. The anion coordination properties in solution have also been studied. The results further demonstrate the coordination behavior of phosphate ion, which shows strong tendency for coordination saturation and geometrical preference, thus allowing for the assembly of novel anion coordination‐based structures as in transition‐metal complexes. 相似文献
4.
5.
This study is concerned with a new,explicit approach by means of which forms of the large strain elastic potential for multiaxial rubberlike elasticity may be obtained based on data for a single deformation mode.As a departure from usual studies,here for the first time errors may be estimated and rendered minimal for all possible deformation modes and,furthermore,failure behavior may be incorporated.Numerical examples presented are in accurate agreement with Treloar's well-known data. 相似文献
6.
Simultaneous quantitative determination of 20 active components in the traditional Chinese medicine formula Zhi‐Zi‐Da‐Huang decoction by liquid chromatography coupled with mass spectrometry: application to study the chemical composition variations in different combinations 下载免费PDF全文
Zheng Tang Ran Yin Kaishun Bi Heyun Zhu Fei Han Kelin Chen Fenrong Wang 《Biomedical chromatography : BMC》2015,29(9):1406-1414
7.
Studies on metabolites and metabolic pathways of bulleyaconitine A in rat liver microsomes using LC‐MSn combined with specific inhibitors 下载免费PDF全文
Hongbin Zhu Fengrui Song Zhiqiang Liu Shuying Liu 《Biomedical chromatography : BMC》2015,29(7):1027-1034
Bulleyaconitine A (BLA) from Aconitum bulleyanum plants is usually used as anti‐inflammatory drug in some Asian countries. It has a variety of bioactivities, and at the same time some toxicities. Since the bioactivities and toxicities of BLA are closely related to its metabolism, the metabolites and the metabolic pathways of BLA in rat liver microsomes were investigated by HPLC–MSn. In this research, the 12 metabolites of BLA were identified according to the results of HPLC‐MSn data and the relevant literature. The results showed that there are multiple metabolites of BLA in rat liver microsomes, including demethylation, deacetylation, dehydrogenation deacetylation and hydroxylation. The major metabolic pathways of BLA in rat liver microsomes were clarified by HPLC‐MS combined with specific inhibitors of CYP450 isoforms. As a result, CYP3A and 2C were found to be the principal CYP isoforms contributing to the metabolism of BLA. Moreover, CYP2D6 and 2E1 are also more important CYP isoforms for the metabolism of BLA. While CYP1A2 only affected the formation rate of M11, its effect on the metabolism of BLA is very small. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
8.
9.
Ionics - This study aims to explore the potential merits of palladium oxide sensing electrode. PdO is applied on a solid-state potentiometric sensor on an yttria-stabilized zirconia (YSZ)... 相似文献
10.
Metabolic profiles of dioscin in rats revealed by ultra‐performance liquid chromatography quadrupole time‐of‐flight mass spectrometry 下载免费PDF全文
He Zhu Jin‐Di Xu Qian Mao Hong Shen Ming Kong Jian‐Ping Chen Song‐Lin Li 《Biomedical chromatography : BMC》2015,29(9):1415-1421
Dioscin (DIS), one of the most abundant bioactive steroidal saponins in Dioscorea sp., is used as a complementary medicine to treat coronary disease and angina pectoris in China. Although the pharmacological activities and pharmacokinetics of DIS have been well demonstrated, information regarding the final metabolic fates is very limited. This study investigated the in vivo metabolic profiles of DIS after oral administration by ultra‐performance liquid chromatography quadrupole time‐of‐flight mass spectrometry method. The structures of the metabolites were identified and tentatively characterized by means of comparing the molecular mass, retention time and fragmentation pattern of the analytes with those of the parent compound. A total of eight metabolites, including seven phase I and one phase II metabolites, were detected and tentatively identified for the first time. Oxidation, deglycosylation and glucuronidation were found to be the major metabolic processes of the compound in rats. In addition, a possible metabolic pathway on the biotransformation of DIS in vivo was proposed. This study provides valuable and new information on the metabolism of DIS, which will be helpful for further understanding its mechanism of action. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献