全文获取类型
收费全文 | 3357篇 |
免费 | 187篇 |
国内免费 | 18篇 |
专业分类
化学 | 2583篇 |
晶体学 | 28篇 |
力学 | 82篇 |
数学 | 466篇 |
物理学 | 403篇 |
出版年
2023年 | 26篇 |
2022年 | 27篇 |
2021年 | 66篇 |
2020年 | 89篇 |
2019年 | 90篇 |
2018年 | 57篇 |
2017年 | 56篇 |
2016年 | 124篇 |
2015年 | 82篇 |
2014年 | 121篇 |
2013年 | 149篇 |
2012年 | 249篇 |
2011年 | 302篇 |
2010年 | 111篇 |
2009年 | 87篇 |
2008年 | 234篇 |
2007年 | 201篇 |
2006年 | 211篇 |
2005年 | 192篇 |
2004年 | 151篇 |
2003年 | 124篇 |
2002年 | 118篇 |
2001年 | 30篇 |
2000年 | 32篇 |
1999年 | 21篇 |
1998年 | 29篇 |
1997年 | 26篇 |
1996年 | 28篇 |
1995年 | 33篇 |
1994年 | 21篇 |
1993年 | 28篇 |
1992年 | 28篇 |
1991年 | 27篇 |
1990年 | 15篇 |
1989年 | 19篇 |
1988年 | 18篇 |
1987年 | 21篇 |
1985年 | 31篇 |
1984年 | 30篇 |
1983年 | 18篇 |
1982年 | 36篇 |
1981年 | 24篇 |
1980年 | 24篇 |
1979年 | 20篇 |
1978年 | 23篇 |
1977年 | 23篇 |
1976年 | 19篇 |
1975年 | 12篇 |
1974年 | 10篇 |
1973年 | 10篇 |
排序方式: 共有3562条查询结果,搜索用时 15 毫秒
941.
942.
Hatfield MP Palermo NY Csontos J Murphy RF Lovas S 《International journal of quantum chemistry》2008,108(5):1017-1021
The accuracy of the determination of the energy of interaction between Phe20 and the Pro5-Thr6-Tyr7-Pro8 complex inside the hydrophobic core of avian pancreatic polypeptide was investigated using three capping strategies for molecular fractionation with conjugated caps and DFT quantum chemical calculations at the BHandHLYP/cc-pVTZ level of theory. The most accurate determination resulted from acetylation of the alpha-amino group combined with methyl amidation of the alpha-carbonyl group with relative deviations less than 10%. Combinations of hydrogenation of the alpha-amino group with the replacement of the alpha-carbonyl group with a hydrogen and the hydrogenation of the alpha-amino group with methylation of the alpha-carbonyl group were less accurate, leading to relative deviations up to 35%. Choice of capping methods depends on the structural features of the polypeptide system, the desired accuracy and the available computational resources. 相似文献
943.
944.
Nicholas D. Alikakos Peter W. Bates Xinfu Chen 《Transactions of the American Mathematical Society》1999,351(7):2777-2805
We establish the existence and robustness of layered, time-periodic solutions to a reaction-diffusion equation in a bounded domain in , when the diffusion coefficient is sufficiently small and the reaction term is periodic in time and bistable in the state variable. Our results suggest that these patterned, oscillatory solutions are stable and locally unique. The location of the internal layers is characterized through a periodic traveling wave problem for a related one-dimensional reaction-diffusion equation. This one-dimensional problem is of independent interest and for this we establish the existence and uniqueness of a heteroclinic solution which, in constant-velocity moving coodinates, is periodic in time. Furthermore, we prove that the manifold of translates of this solution is globally exponentially asymptotically stable.
945.
Pei Y Lilly MJ Owen DJ D'Souza LJ Tang XQ Yu J Nazarbaghi R Hunter A Anderson CM Glasco S Ede NJ James IW Maitra U Chandrasekaran S Moos WH Ghosh SS 《The Journal of organic chemistry》2003,68(1):92-103
Type II diabetes mellitus is a chronic metabolic disorder that can lead to serious cardiovascular, renal, neurologic, and retinal complications. While several drugs are currently prescribed to treat type II diabetes, their efficacy is limited by mechanism-related side effects (weight gain, hypoglycemia, gastrointestinal distress), inadequate efficacy for use as monotherapy, and the development of tolerance to the agents. Consequently, combination therapies are frequently employed to effectively regulate blood glucose levels. We have focused on the mitochondrial sodium-calcium exchanger (mNCE) as a novel target for diabetes drug discovery. We have proposed that inhibition of the mNCE can be used to regulate calcium flux across the mitochondrial membrane, thereby enhancing mitochondrial oxidative metabolism, which in turn enhances glucose-stimulated insulin secretion (GSIS) in the pancreatic beta-cell. In this paper, we report the facile synthesis of benzothiazepines and derivatives by S-alkylation using 2-aminobenzhydrols. The syntheses of other bicyclic analogues based on benzothiazepine, benzothiazecine, benzodiazecine, and benzodiazepine templates are also described. These compounds have been evaluated for their inhibition of mNCE activity, and the results from the structure-activity relationship (SAR) studies are discussed. 相似文献
946.
Petrella AJ Roberts NK Craig DC Raston CL Lamb RN 《Chemical communications (Cambridge, England)》2003,(8):1014-1015
Reaction of p-'Bu-calix[6]arene with potassium metal in methanol followed by [TiCp2Cl2] affords novel mononuclear and binuclear monocyclopentadienyl titanium(IV) complexes, both having the same inverted double cone conformation with a Cp in one of the cavities, in both complexes. 相似文献
947.
We present high-precision measurements of pure element stable isotope pairs that demonstrate mass has no influence on the backscattering of electrons at typical electron microprobe energies. The traditional prediction of average backscatter intensities in compounds was pragmatically based on elemental mass fractions. Our isotopic measurements establish that this approximation has no physical basis. We propose an alternative model to mass fraction averaging, based on the number of electrons or protons, termed "electron fraction," which predicts backscatter yield better than mass fraction averaging. We also present an improved backscatter (electron loss) factor based on a modified electron fraction average for the ZAF atomic number correction that provides a significant analytical improvement, especially where large atomic number corrections are required. 相似文献
948.
949.
950.