全文获取类型
收费全文 | 5214篇 |
免费 | 994篇 |
国内免费 | 1282篇 |
专业分类
化学 | 4450篇 |
晶体学 | 61篇 |
力学 | 327篇 |
综合类 | 82篇 |
数学 | 559篇 |
物理学 | 2011篇 |
出版年
2024年 | 19篇 |
2023年 | 99篇 |
2022年 | 178篇 |
2021年 | 212篇 |
2020年 | 203篇 |
2019年 | 226篇 |
2018年 | 173篇 |
2017年 | 190篇 |
2016年 | 252篇 |
2015年 | 277篇 |
2014年 | 293篇 |
2013年 | 434篇 |
2012年 | 472篇 |
2011年 | 518篇 |
2010年 | 398篇 |
2009年 | 359篇 |
2008年 | 406篇 |
2007年 | 348篇 |
2006年 | 320篇 |
2005年 | 301篇 |
2004年 | 210篇 |
2003年 | 189篇 |
2002年 | 248篇 |
2001年 | 213篇 |
2000年 | 163篇 |
1999年 | 136篇 |
1998年 | 110篇 |
1997年 | 85篇 |
1996年 | 51篇 |
1995年 | 59篇 |
1994年 | 61篇 |
1993年 | 48篇 |
1992年 | 53篇 |
1991年 | 56篇 |
1990年 | 27篇 |
1989年 | 20篇 |
1988年 | 17篇 |
1987年 | 12篇 |
1986年 | 10篇 |
1985年 | 13篇 |
1984年 | 7篇 |
1983年 | 11篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1957年 | 1篇 |
1943年 | 1篇 |
排序方式: 共有7490条查询结果,搜索用时 0 毫秒
991.
本文主要讨论一类完备Riemann流形上的调和函数所组成的线性空间.推广了P.Li及L.F.Tam[5], [7]和和Greene-Wu[3]中的结果. 相似文献
992.
IrnmobilisedaIninoacylaseisanotablecatalystforthekineticresolutionofN-acetyl-D,L-aIninoacidsandquitealotofresearchworkhasbeeninvolvedonaminoacylase~bilisationswithitscarriers.lTheauthorshaverePortedthattheaIninosilicagelspreparedbyanlinProvedmethodwereeffechveforchymotryPsininunobilisahon,'l'butitwasnotproperforaIninoacylasetriobilisahon.InordertodevelopasahsfactorysurfacesmictUreofsilicagelsforaIninoacylasetriobilisation,tWokindsofreactivegrouPs,theN,N-diethylaIninogrouPandthehydroxygr… 相似文献
993.
Xiao‐Mei Qiu Xi‐Lian Wei Bao‐Lin Yin De‐Zhi Sun 《Journal of Polymer Science.Polymer Physics》2006,44(2):275-283
The interactions between sodium bis(2‐ethylhexyl) sulfosuccinae (AOT) and two nonionic water‐soluble polymers, including polyvinyl pyrrolidone (PVP) and polyethylene glycol (PEG) have been investigated by using isothermal titration microcalorimetry in aqueous solutions at 298.15 K. The results show that the critical aggregation concentration, which corresponding to the first turning point in the curve of experimental interaction heat versus concentration of the surfactant, is lower than the critical micellar concentration (cmc), confirming the existence of polymer‐surfactant interactions. The value of cac is not sensitive to the relative amount of polymer in low concentration range of the polymer. The mono‐layer saturated adsorption concentration, which corresponding to the second turning point, rises as the polymer concentration is increased. The interaction between PVP and AOT is stronger than that between PEG and AOT. The results also indicate that the aggregation of AOT in water and polymers solutions is entropically driven. The observed thermal effects have been interpreted in terms of the interactions of the polymer molecules with AOT monomers or the molecular clusters. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 275–283, 2006 相似文献
994.
JunBoWANG ChunHaoYANG XueMingYAN XiHartWU YuYuanXIE 《中国化学快报》2005,16(7):859-862
The novel bone-targeted agents were designed and synthesized by the combination of raloxifene and bisphosphonates. The anti-osteoporosis effect was evaluated by bone mineral density (BMD) obtained from OVX mice in vivo. The results indicated that the compound 8, 9 not only prevented ovariectomy induced loss of bone but also enhanced BMD to 0.87% and 19.67% compared to Sham, respectively. 相似文献
995.
Xi Yin Zheng 《Set-Valued Analysis》2005,13(2):181-196
We introduce and discuss measure of non-Radon–Nikodym property to investigate differentiability of continuous convex functions on Banach spaces. Using this new concept, we establish some results about Asplund spaces and generic Fréchet differentiability of continuous convex functions on non-Asplund spaces.Mathematics Subject Classifications (2000) 46B22, 49J50, 49J53. 相似文献
996.
Fubao Xi 《Journal of Mathematical Analysis and Applications》2002,272(2):458-472
In this paper we consider a random evolution equation which is perturbed by Gaussian type noise, and show how to construct its coupled solutions. On the basis of the coupling results, we discuss the asymptotic flatness and the stability in total variation norm for the solutions of the equation. In addition, we also prove the Feller continuity, and the existence and uniqueness of invariant measures of the solutions. 相似文献
997.
Using the Tang-Toennies potential model and a set of expressions given by J. Kestinet al., we calculate the transport properties of the two noble gases He and Ne and of their binary mixtures, based upon the calculation
of the interaction potential. Our calculated results for the transport properties are restricted to low densities but cover
the full temperature interval extending from 50 K to the onset of ionization; the mole fraction of the binary mixtures isx
1:x
2=0.25:0.75. Our results are comparable to the best theoretical results given by J. Kestinet al. 相似文献
998.
测量了1,4-羟基蒽醌及其氘化物的红外光谱,用NRCC程序进行了振动分析,由于同时考虑了分子内与分子间的氢键,统一处理面内与面外振动,计算结果优于文献报道,并纠正了一些错误归属。 相似文献
999.
Xi Li Xianghao Cui Xuewu Liu Mingzhi Jin Liangzhi Xiao Muyu Zhao 《Hyperfine Interactions》1992,69(1-4):851-854
Perovskite-type nanocrystalline materials LaFeO3 with different crystal size were synthesized. These samples with different compacted pressure were investigated by Mössbauer spectroscopy at room temperature. The results showed that the LaFeO3 crystal in size of 70nm possessed an antiferromagnetic structure, that of 12nm was the superposition of the weaker antiferromagnetic structure and the stronger superparamagnetic structure. The rate of interface atoms to crystal atoms and the hyperfine field in nanocrystals varied with the compacted pressure. 相似文献
1000.
在实验教学中,有时候我们必须要以比仪器所能达到的技术指标更小的不确定度(更高的准确度)来进行测量.对于这种情况,可以利用标准器对仪器进行特性修正. 相似文献