全文获取类型
收费全文 | 375719篇 |
免费 | 5030篇 |
国内免费 | 1245篇 |
专业分类
化学 | 203654篇 |
晶体学 | 6076篇 |
力学 | 15217篇 |
综合类 | 12篇 |
数学 | 43386篇 |
物理学 | 113649篇 |
出版年
2019年 | 2950篇 |
2018年 | 3608篇 |
2017年 | 3625篇 |
2016年 | 6135篇 |
2015年 | 4190篇 |
2014年 | 6091篇 |
2013年 | 16400篇 |
2012年 | 11969篇 |
2011年 | 14397篇 |
2010年 | 10025篇 |
2009年 | 9809篇 |
2008年 | 13264篇 |
2007年 | 13213篇 |
2006年 | 12585篇 |
2005年 | 11416篇 |
2004年 | 10486篇 |
2003年 | 9304篇 |
2002年 | 8980篇 |
2001年 | 10667篇 |
2000年 | 8147篇 |
1999年 | 6414篇 |
1998年 | 5167篇 |
1997年 | 5109篇 |
1996年 | 5004篇 |
1995年 | 4658篇 |
1994年 | 4611篇 |
1993年 | 4441篇 |
1992年 | 5154篇 |
1991年 | 4833篇 |
1990年 | 4768篇 |
1989年 | 4734篇 |
1988年 | 4650篇 |
1987年 | 4694篇 |
1986年 | 4355篇 |
1985年 | 5933篇 |
1984年 | 5970篇 |
1983年 | 5057篇 |
1982年 | 5332篇 |
1981年 | 5104篇 |
1980年 | 5034篇 |
1979年 | 5295篇 |
1978年 | 5532篇 |
1977年 | 5375篇 |
1976年 | 5246篇 |
1975年 | 5026篇 |
1974年 | 4979篇 |
1973年 | 5134篇 |
1972年 | 3361篇 |
1968年 | 3177篇 |
1967年 | 3355篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
Galkina E. G. Zaspel C. E. Ivanov B. A. Kulagin N. E. Lerman L. M. 《JETP Letters》2019,110(7):481-486
JETP Letters - The motion of domain walls in GdFeCo-type ferrimagnets near the point of compensation of sublattice spins s1 and s2, when the effects of the exchange increase in the limiting wall... 相似文献
102.
103.
Dr. Sebastian Lars Müller Xinglong Zhou Dr. Peter Leonard Oxana Korzhenko Dr. Constantin Daniliuc Prof. Dr. Frank Seela 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(12):3077-3090
Silver-mediated α-dC–Ag+–β-dC hybrid base pairs decorated with 5-iodo- or 5-octadiynyl residues are well accommodated in duplex DNA. A strong Tm increase and favorable thermodynamic data for duplex DNA were observed after addition of silver ions. The phenomenon is particularly obvious when both nucleobases of the base pairs are functionalized. Neither the position of the base pair, nor the type of 5-substituent had a negative influence. On the contrary, functionalization of conventional silver-mediated β-dC–Ag+–β-dC homo base pairs showed a negative impact induced by the bulky substituents. To this end, cytosine modified 12-mer oligodeoxynucleotides were prepared by solid-phase synthesis employing new α-anomeric 2′-deoxycytidine phosphoramidites. A multigram scale synthesis was developed for 5-iodo-α-d -2′-deoxycytidine ( 1 ) employing the direct glycosylation of cytosine with Hoffer's α-d -halogenose followed by separation of anomeric DMT nucleosides. Regarding base-pair stability and functionalization silver-mediated α/β-dC hybrid base pairs were found to be superior to β/β-dC homo pairs. According to their extraordinary properties, they might find applications in DNA diagnostics, material science, or nanotechnology. 相似文献
104.
105.
106.
Jigneshkumar P. Patel Zou Guo Xiang Shaw Ling Hsu Andrew B. Schoch Sena Ada Carleen Dean Matsumoto 《Journal of Polymer Science.Polymer Physics》2015,53(21):1519-1526
A uniform dispersion of reactants is necessary to achieve a complete reaction involving multicomponents. In this study, we have examined the role of plasticizer in the reaction of two seemingly unlikely reactants: a highly crystalline hexamethylenetetramine (HMTA) and a strongly hydrogen bonded phenol formaldehyde resin. By combining information from NMR, infrared spectroscopy and differential scanning calorimetry, we were able to determine the role of specific intermolecular interactions necessary for the plasticizer to dissolve the highly crystalline HMTA and to plasticize the phenol formaldehyde resin in this crosslinking reaction. The presence of the plasticizer increased the segmental mobility, disrupted the hydrogen bonded matrix, and freed the hydroxyl units, which further increased the solubility of the HMTA. Both the endothermic and exothermic transitions are accounted for in the calorimetric data obtained. For the first time, it is possible to obtain the effective molar ratio of each component needed to complete the crosslinking reaction efficiently. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1519–1526 相似文献
107.
S. V. Panin I. V. Vlasov V. P. Sergeev B. B. Ovechkin P. O. Marushchak Sunder Ramasubbu P. S. Lyubutin V. V. Titkov 《Physical Mesomechanics》2015,18(3):261-272
The structure and properties of 12Cr1MoV steel irradiated with a zirconium ion beam were studied by optical microscopy, scanning electron microscopy, and micro- and nanoindentation. It is shown that the modification covers the entire cross-section of the irradiated specimens to a depth of 1 mm. The data on irradiation-induced structural changes are used to interpret the changes in mechanical properties of the irradiated specimens under static and cyclic loading. Particular attention is given to analysis of strain estimation by the digital image correlation method. 相似文献
108.
109.
Briana L. Simms Nan Ji Indika Chandrasiri Mohammad Farid Zia Chinwe S. Udemgba Ravinder Kaur Jared H. Delcamp Alex Flynt Chalet Tan Davita L. Watkins 《Journal of polymer science. Part A, Polymer chemistry》2021,59(19):2177-2192
Here, we demonstrate the applicability of self-assembling linear-dendritic block copolymers (LDBCs) and their nanoaggregates possessing varied surfaces as therapeutic nanocarriers. These LDBCs are comprised of a hydrophobic, linear polyester chemically coupled to a hydrophilic dendron polyamidoamine (PAMAM)—the latter of which acts as the surface of the self-assembled nanoaggregate in aqueous media. To better understand how surface charge density affects the overall operability of these nanomaterials, we modified the nanoaggregate surface to yield cationic (NH3+), neutral (OH), and anionic (COO−) surfaces. The effect of these modifications on the physicochemical properties (i.e., size, morphology, and surface charge density), colloidal stability, and cellular uptake mechanism of the polymeric nanocarrier were investigated. This comparative study demonstrates the viability of nanoaggregates formed from PDLLA-PAMAM LDBCs to serve as nanocarriers for applications in drug delivery. 相似文献
110.