全文获取类型
收费全文 | 24645篇 |
免费 | 3900篇 |
国内免费 | 2052篇 |
专业分类
化学 | 6093篇 |
晶体学 | 72篇 |
力学 | 3333篇 |
综合类 | 624篇 |
数学 | 10498篇 |
物理学 | 9977篇 |
出版年
2024年 | 51篇 |
2023年 | 265篇 |
2022年 | 602篇 |
2021年 | 653篇 |
2020年 | 639篇 |
2019年 | 584篇 |
2018年 | 609篇 |
2017年 | 905篇 |
2016年 | 977篇 |
2015年 | 816篇 |
2014年 | 1312篇 |
2013年 | 1690篇 |
2012年 | 1346篇 |
2011年 | 1519篇 |
2010年 | 1329篇 |
2009年 | 1525篇 |
2008年 | 1703篇 |
2007年 | 1761篇 |
2006年 | 1444篇 |
2005年 | 1301篇 |
2004年 | 1270篇 |
2003年 | 1062篇 |
2002年 | 1100篇 |
2001年 | 817篇 |
2000年 | 725篇 |
1999年 | 659篇 |
1998年 | 591篇 |
1997年 | 500篇 |
1996年 | 439篇 |
1995年 | 434篇 |
1994年 | 292篇 |
1993年 | 270篇 |
1992年 | 206篇 |
1991年 | 226篇 |
1990年 | 157篇 |
1989年 | 105篇 |
1988年 | 126篇 |
1987年 | 90篇 |
1986年 | 67篇 |
1985年 | 76篇 |
1984年 | 60篇 |
1983年 | 33篇 |
1982年 | 49篇 |
1981年 | 49篇 |
1980年 | 36篇 |
1979年 | 37篇 |
1978年 | 18篇 |
1977年 | 16篇 |
1976年 | 13篇 |
1974年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
采用DIS数字信息化系统,对不同浓度的蓝墨水溶液在激光光源照射下的透射平均照度及照度分布图像进行实验研究,得到了平均照度值随溶液浓度变化的规律。对不同颜色塑料膜片对白炽灯光源透过照度值及照度分布图像进行实验研究得到及其相关之规律。 相似文献
2.
Studies on metabolism of total glucosides of paeony from Paeoniae Radix Alba in rats by UPLC‐Q‐TOF‐MS/MS 下载免费PDF全文
Wenli Cao Xinguo Wang Haojie Li Xuliang Shi Wencheng Fan Shaohua Zhao Minyan Liu Liying Niu 《Biomedical chromatography : BMC》2015,29(11):1769-1779
Total glucosides of paeony are the active constituents of Paeoniae Radix Alba. In this study, a novel strategy was proposed to find more metabolites and the differences between paeoniflorin, albiflorin and total glucosides of paeony (TGP). This strategy was characterized as follows: firstly, the animals were divided into three groups (paeoniflorin, albiflorin and TGP) to identify the source of TGP metabolites from paeoniflorin or albiflorin; secondly, a generic information‐dependent acquisition scan for the low‐level metabolites was triggered by the multiple mass defect filter and dynamic background subtraction; thirdly, the metabolites were identified with a combination of data‐processing methods including mass defect filtering, neutral loss filtering and product ion filtering; finally, a comparative study was used in the metabolism of paeoniflorin, albiflorin and TGP. Based on the strategy, 18 metabolites of TGP, 10 metabolites of paeoniflorin and 13 metabolites of albiflorin were identified respectively. The results indicated that the hydrolysis, conjugation reaction and oxidization were the major metabolic pathways, and the metabolic sites were the glycosidic linkage, the ester bond and the benzene ring. This study is first to explore the metabolism of TGP, and these findings enhance our understanding of the metabolism and the interactions of paeoniflrin and albiflorin in TGP. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
4.
对由一类非线性抛物型变分不等方程所描述的无穷维动力系统,给出了存在全局吸引子及弱近似惯性流形的充分条件. 相似文献
5.
Phase Relations and Sodium Ion Conductivity within the Quasi-binary System Na2SiF6/Na2AIF6 . The phase diagram of the Na2SiF6/Na3AlF6 system has been determined by means of x-ray powder diffraction, thermal analysis and conductivity measurements in the sub-solidus region. Na3AlF6 accomodates up to 73 mol.-% Na2SiF6 maintaining the crystal structure type. The sodium ion conductivity increases by about five orders of magnitude upon doping Na3AlF6 with Na2SiF6. 相似文献
6.
In this paper, the authors studied certain properties of the estimate of Liang and Krishnaiah (1985, J. Multivariate Anal. 16, 162–172) for multivariate binary density. An alternative shrinkage estimate is also obtained. The above results are generalized to general orthonormal systems. 相似文献
7.
8.
On Quantum Team Games 总被引:2,自引:0,他引:2
E. Ahmed M. F. Elettreby A. S. Hegazi 《International Journal of Theoretical Physics》2006,45(5):880-886
Recently Liu and Simaan (2004) convex static multi-team classical games have been introduced. Here they are generalized to both nonconvex, dynamic and quantum games. Puu's incomplete information dynamical systems are modified and applied to Cournot team game. The replicator dynamics of the quantum prisoner's dilemma game is also studied. 相似文献
9.
基于校园网的实验管理系统的设计 总被引:2,自引:1,他引:1
主要讨论了应用实验室管理系统的必要性,并从用户需求分析、系统总体设计、功能模块的设计等方面对B/S实验室管理系统的开发进行了详细的阐述。 相似文献
10.
Tsutomu KumagaiMasaaki Tomura Jun-ichi NishidaYoshiro Yamashita 《Tetrahedron letters》2003,44(36):6845-6848
1,3-Dithiol-2-ylidene derivatives containing bis(ethynylpyridine) units were synthesized using a Pd-catalyzed reaction of the corresponding dibromide. X-Ray crystal analysis revealed unique crystal structures depending on the aromatic groups. The absorption spectra and redox properties indicated intramolecular charge-transfer interactions between the 1,3-dithiole unit and the pyridyl parts. 相似文献