全文获取类型
收费全文 | 13160篇 |
免费 | 1207篇 |
国内免费 | 1165篇 |
专业分类
化学 | 10269篇 |
晶体学 | 172篇 |
力学 | 469篇 |
综合类 | 91篇 |
数学 | 1204篇 |
物理学 | 3327篇 |
出版年
2024年 | 20篇 |
2023年 | 113篇 |
2022年 | 290篇 |
2021年 | 364篇 |
2020年 | 351篇 |
2019年 | 363篇 |
2018年 | 296篇 |
2017年 | 314篇 |
2016年 | 533篇 |
2015年 | 542篇 |
2014年 | 661篇 |
2013年 | 866篇 |
2012年 | 1136篇 |
2011年 | 1228篇 |
2010年 | 798篇 |
2009年 | 724篇 |
2008年 | 955篇 |
2007年 | 819篇 |
2006年 | 780篇 |
2005年 | 714篇 |
2004年 | 566篇 |
2003年 | 500篇 |
2002年 | 529篇 |
2001年 | 355篇 |
2000年 | 289篇 |
1999年 | 256篇 |
1998年 | 171篇 |
1997年 | 126篇 |
1996年 | 108篇 |
1995年 | 106篇 |
1994年 | 88篇 |
1993年 | 89篇 |
1992年 | 69篇 |
1991年 | 65篇 |
1990年 | 57篇 |
1989年 | 40篇 |
1988年 | 32篇 |
1987年 | 28篇 |
1986年 | 33篇 |
1985年 | 29篇 |
1984年 | 14篇 |
1983年 | 16篇 |
1982年 | 17篇 |
1981年 | 10篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1978年 | 7篇 |
1976年 | 7篇 |
1975年 | 8篇 |
1974年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
Asner DM Athanas M Bliss DW Brower WS Masek G Paar HP Gronberg J Korte CM Kutschke R Menary S Morrison RJ Nakanishi S Nelson HN Nelson TK Qiao C Richman JD Roberts D Ryd A Tajima H Witherell MS Balest R Cho K Ford WT Lohner M Park H Rankin P Smith JG Alexander JP Bebek C Berger BE Berkelman K Bloom K Browder TE Cassel DG Cho HA Coffman DM Crowcroft DS Dickson M Drell PS Dumas DJ Ehrlich R Elia R Gaidarev P Garcia-Sciveres M Gittelman B Gray SW Hartill DL Heltsley BK Henderson S Jones CD 《Physical review D: Particles and fields》1996,53(3):1039-1050
63.
64.
65.
66.
67.
The Diels-Alder reaction between anthracene and tetracyanoethylene in acetonitrile does not reach a steady-state during the first half-life. The reaction follows the reversible consecutive second-order mechanism accompanied by the formation of a kinetically significant intermediate. The experimental observations consistent with this mechanism include extent of reaction-time profiles which deviate markedly from those expected for the irreversible second-order mechanism and initial pseudo first-order rate constants which differ significantly from those measured at longer times. It is concluded that the reaction intermediate giving rise to these deviations cannot be the charge-transfer (CT) complex, which is formed during the time of mixing, but rather a more intimate complex with a geometry favorable to the formation of the Diels-Alder adduct. The kinetics of the reaction were resolved into the microscopic rate constants for the individual steps. The rate constants, as shown in equation 1, at 293 K were observed to be 5.46 M(-)(1) s(-)(1) (k(f)), 14.8 s(-)(1) (k(b)), and 12.4 s(-)(1) (k(p)). Concentration profiles calculated under all conditions show that intermediate concentrations increase to maximum values early in the reaction and then continually decay during the first half-life. It is concluded that the charge-transfer complex may be an intermediate preceding the formation of the reactant complex, but due to its rapid formation and dissociation it is not detected by the kinetic measurements. 相似文献
68.
Thermal properties of bio flour-filled polypropylene bio-composites with different pozzolan contents
H. -S. Kim S. -W. Choi B. -H. Lee S. Kim H. -J. Kim C. W. Cho D. Cho 《Journal of Thermal Analysis and Calorimetry》2007,89(3):821-827
In this study, the thermal properties of bio-flour-filled, polypropylene (PP) bio-composites with different pozzolan contents
were investigated. With increasing pozzolan content, the thermal stability, 5% mass loss temperature and derivative thermogravimetric
curve (DTGmax) temperatures of the bio-composites slightly increased. The coefficient of thermal expansion (CTE) and thermal expansion
of the bio-composites decreased as the pozzolan content increased. The glass transition temperature (T
g), melting temperature (T
m) and percentage of crystallinity (X
c) of the bio-composites were not significantly changed. The thermal stability, thermal expansion and X
c of the maleic anhydride-grafted PP (MAPP)-treated bio-composites were much higher than those of non-treated bio-composites
at 1% pozzolan content due to enhanced interfacial adhesion. X-ray diffraction (XRD) analysis confirmed the crystallinity
of pozzolan-added bio-composites. From these results, we concluded that the addition of pozzolan in the bio-composites was
an effective method for enhancing the thermal stability and thermal expansion. 相似文献
69.
Qin B Lin J Lin Z Ren H Xue Y 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(4):717-720
The vibration spectrum and FAB mass spectrum of (+/-)-1-[3-(2-methoxyphenoxy)-2-hydroxypropyl]-4-[(2,6-dimethylphenyl)aminocarbonylmethyl]piperazine dihydrochloride salt was studied. By comparing with the spectra of free base, different bands of IR were found in the NH+ stretching, the NH+ deformation motion, the CH2 of NCH2 group symmetric stretching, the CH2 of N-CH2 group twisting and the CN stretching. FAB shows the basic peak is M + H. Other m/e peaks are consistent with the structure. 相似文献
70.
Yechen Hu Zhongcheng Wang Liang Liu Jianhua Zhu Dongxue Zhang Mengying Xu Yuanyuan Zhang Feifei Xu Yun Chen 《Chemical science》2021,12(23):7993
Precision medicine has been strongly promoted in recent years. It is used in clinical management for classifying diseases at the molecular level and for selecting the most appropriate drugs or treatments to maximize efficacy and minimize adverse effects. In precision medicine, an in-depth molecular understanding of diseases is of great importance. Therefore, in the last few years, much attention has been given to translating data generated at the molecular level into clinically relevant information. However, current developments in this field lack orderly implementation. For example, high-quality chemical research is not well integrated into clinical practice, especially in the early phase, leading to a lack of understanding in the clinic of the chemistry underlying diseases. In recent years, mass spectrometry (MS) has enabled significant innovations and advances in chemical research. As reported, this technique has shown promise in chemical mapping and profiling for answering “what”, “where”, “how many” and “whose” chemicals underlie the clinical phenotypes, which are assessed by biochemical profiling, MS imaging, molecular targeting and probing, biomarker grading disease classification, etc. These features can potentially enhance the precision of disease diagnosis, monitoring and treatment and thus further transform medicine. For instance, comprehensive MS-based biochemical profiling of ovarian tumors was performed, and the results revealed a number of molecular insights into the pathways and processes that drive ovarian cancer biology and the ways that these pathways are altered in correspondence with clinical phenotypes. Another study demonstrated that quantitative biomarker mapping can be predictive of responses to immunotherapy and of survival in the supposedly homogeneous group of breast cancer patients, allowing for stratification of patients. In this context, our article attempts to provide an overview of MS-based chemical mapping and profiling, and a perspective on their clinical utility to improve the molecular understanding of diseases for advancing precision medicine.An overview of MS-based chemical mapping and profiling, indicating its contributions to the molecular understanding of diseases in precision medicine by answering "what", "where", "how many" and "whose” chemicals underlying clinical phenotypes. 相似文献