全文获取类型
收费全文 | 6313篇 |
免费 | 1135篇 |
国内免费 | 1113篇 |
专业分类
化学 | 5390篇 |
晶体学 | 60篇 |
力学 | 271篇 |
综合类 | 81篇 |
数学 | 771篇 |
物理学 | 1988篇 |
出版年
2024年 | 23篇 |
2023年 | 107篇 |
2022年 | 137篇 |
2021年 | 158篇 |
2020年 | 234篇 |
2019年 | 273篇 |
2018年 | 233篇 |
2017年 | 175篇 |
2016年 | 290篇 |
2015年 | 335篇 |
2014年 | 362篇 |
2013年 | 487篇 |
2012年 | 532篇 |
2011年 | 506篇 |
2010年 | 421篇 |
2009年 | 416篇 |
2008年 | 435篇 |
2007年 | 399篇 |
2006年 | 379篇 |
2005年 | 336篇 |
2004年 | 321篇 |
2003年 | 300篇 |
2002年 | 355篇 |
2001年 | 229篇 |
2000年 | 196篇 |
1999年 | 193篇 |
1998年 | 125篇 |
1997年 | 105篇 |
1996年 | 75篇 |
1995年 | 62篇 |
1994年 | 61篇 |
1993年 | 33篇 |
1992年 | 39篇 |
1991年 | 49篇 |
1990年 | 31篇 |
1989年 | 22篇 |
1988年 | 17篇 |
1987年 | 12篇 |
1986年 | 20篇 |
1985年 | 22篇 |
1984年 | 10篇 |
1983年 | 10篇 |
1982年 | 10篇 |
1981年 | 4篇 |
1979年 | 4篇 |
1977年 | 2篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1968年 | 3篇 |
1936年 | 2篇 |
排序方式: 共有8561条查询结果,搜索用时 15 毫秒
991.
高Verdet常数的Tb3+铝硼硅酸盐玻璃 总被引:1,自引:1,他引:0
本文研究了一种铝硼硅酸盐基质玻璃,通过加大单位体积的稀土离子浓度,并选择P值大的顺磁性Tb3+作为弗尔德常数贡献的主要离子,经反复试验研究,制定合理的熔制工艺,得到性能稳定的透明顺磁旋光玻璃。弗尔德常数V=-0.375/Oe·cm。是目前世界上弗尔德常数较高的磁旋光玻璃。 相似文献
992.
Ruan L. Liu Y. Gao Z. Shen P. Sheng Q. S. 《Journal of Thermal Analysis and Calorimetry》2002,70(2):521-525
The thermogenic curves of the aerobic metabolism of the three strains of Bacillus thuringiensis
B.t. A, B.t. B and B.t. C have been determined by using an LKB-2277 BioActivity Monitor. B.t. A was the host bacterium without foreign gene. B.t. B and B.t. C were constructed by transforming different foreign genes into the host B.t. A, respectively. B.t. B expressed erythromycin resistant gene, while B.t. C expressed both erythromycin resistant gene and tyrosinase gene. The heat flow rate of these strains is B.t. A> B.t. B >B.t. C. These results indicated that there is obvious interrelation between expression of foreign genes and heat flow rate of
B.t. strains.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
993.
In this paper we prove the existence of global weak solutions of the p-harmonic flow with potential between Riemannian manifolds M and N for arbitrary initial data having finite p-energy in the case when the target N is a homogeneous space with a left invariant metric.
Received March 17, 1999, Revised September 22, 1999, Accepted October 15, 1999 相似文献
994.
ThedevelopmentandaPplicationofchemicallymodifiedelectrodescontinuetobeareasofvigorousresearchactivityl-2.Recently,complexatioswithorganicreagentsasmodifiersincarbonpasteelectrodeshavebeenemployedforanalyticaldeterminations3.Schiffbaseligands,however,havebeenscarcelyreportedasmodifierstodeterminemetalions'.Theprincipalcharacteristicrequiredforthesuccessfulconstr[lctionofamodifiedcarbonpasteelectrodeisthatthesolubilityofthemodifiermustbesoslightinthesolventsemployedthatitremainstablyincorporated… 相似文献
995.
Recent advances in the study of short-lived reactive resonances are reviewed. Special emphasis is given to addressing the
question of how reactive resonances might be observed in molecular beam scattering experiments. Three case studies are presented
for simple triatomic systems that are believed to exhibit resonance phenomena: F + HD → D + HF, F + H2 → H + HF, and H + HD → D + H2. It is seen that reactive resonances do strongly influence collision observables, but in a different way for each case. At
this stage, there does not appear to be a unique resonance signature that can be applied to all reactions.
Received: 2 March 2002 / Accepted: 2 June 2002 / Published online: 17 October 2002
Acknowledgements. For their valuable input into the research discussed here, we are grateful to our collaborators, K. Liu, S.H. nk;Lee, F.
Dong, D.E. Manolopoulos, D, Skouteris, X. Yang, S. Harich, D. Dai, and C.C. Wang. This work was supported by the National
Science Foundation.
Correspondence to: R. T. Skodje e-mail: skokje@spot.colorado.edu 相似文献
996.
997.
盛平兴 《应用数学与计算数学学报》1996,10(1):67-72
本文讨论两点边值问题解的存在性,在没有孤立性条件下,获得了不动点定理,作为应用实例,给出了反应扩散方程稳态解的存在性证明。 相似文献
998.
Gui Sheng DENG Ming Yi LIAO Xue TIAN Jian Bo WANG Key Laboratory of Bioorganic Chemistry Molecular Engineering of Ministry of Education College of Chemistry Peking University Beijing 《中国化学快报》2005,(5)
The nucleophilic addition to α, β-unsaturated carbonyl compounds is a fundamental C-C bond forming reaction in organic chemistry1. Since there are two reaction sites in the α, β–unsaturated carbonyl group, the regioselectivity of the nucleophilic addition (1, 2 vs. 1, 4 addition) is of primary importance when applying this type of reaction in organic synthesis. Factors that control the regioselectivity include the softness and hardness of the attacking nucleophiles2, solvent and temperatu… 相似文献
999.
A New Alkaloid from Sinomenium acutum 总被引:2,自引:0,他引:2
Wei Ming CHENG Feng QIU Li Jun WU Xin Sheng YAO 《中国化学快报》2005,16(11):1481-1483
Sinomenium acutum is widely used in East and South Asia for the treatment of many diseases, especially rheumatoid arthritis (RA). The chemical research on Sinomenium acutum led to the isolation of a new alkaloid compound (1). On the basis of chemical evidences and spectral analysis, 1 was identified as N-(1, 7-dimethoxylphenanthren-2-yl)acetamide. 相似文献
1000.
Wei XIE Fu Sheng NIE Meng Long LI Guang Ming LI Min Chun LU 《中国化学快报》2006,17(7):929-932
This paper studies various classifiers to identify primary, secondary or tertiary alcohols by using segmental spectra and their combinations to support vector machines (SVMs). The results showed that the O-H in-plane bending absorption contributed most to identification their substitute. This conclusion disagrees with related known research results. 相似文献