全文获取类型
收费全文 | 393603篇 |
免费 | 10068篇 |
国内免费 | 5852篇 |
专业分类
化学 | 199584篇 |
晶体学 | 5702篇 |
力学 | 20368篇 |
综合类 | 352篇 |
数学 | 56064篇 |
物理学 | 127453篇 |
出版年
2021年 | 3039篇 |
2020年 | 3558篇 |
2019年 | 3594篇 |
2018年 | 12315篇 |
2017年 | 13017篇 |
2016年 | 9813篇 |
2015年 | 5365篇 |
2014年 | 6460篇 |
2013年 | 13649篇 |
2012年 | 16343篇 |
2011年 | 26135篇 |
2010年 | 16943篇 |
2009年 | 16909篇 |
2008年 | 22908篇 |
2007年 | 25828篇 |
2006年 | 12416篇 |
2005年 | 17041篇 |
2004年 | 12815篇 |
2003年 | 11620篇 |
2002年 | 9547篇 |
2001年 | 10038篇 |
2000年 | 7892篇 |
1999年 | 5739篇 |
1998年 | 4683篇 |
1997年 | 4556篇 |
1996年 | 4589篇 |
1995年 | 3978篇 |
1994年 | 3921篇 |
1993年 | 3627篇 |
1992年 | 4113篇 |
1991年 | 4099篇 |
1990年 | 3813篇 |
1989年 | 3587篇 |
1988年 | 3514篇 |
1987年 | 3476篇 |
1986年 | 3347篇 |
1985年 | 4340篇 |
1984年 | 4321篇 |
1983年 | 3487篇 |
1982年 | 3688篇 |
1981年 | 3417篇 |
1980年 | 3163篇 |
1979年 | 3476篇 |
1978年 | 3708篇 |
1977年 | 3685篇 |
1976年 | 3644篇 |
1975年 | 3282篇 |
1974年 | 3440篇 |
1973年 | 3459篇 |
1972年 | 2571篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
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
122.
123.
Kondakov N. N. Mel´nikova T. M. Chekryzhova T. V. Mel´nikova M. V. Zinin A. I. Torgov V. I. Chizhov A. O. Kononov L. O. 《Russian Chemical Bulletin》2015,64(5):1142-1148
Russian Chemical Bulletin - Terminal disaccharide fragment of phenolic glycolipid from Mycobacterium leprae (PGL-I) was synthesized as a glycoside with 4-(2-aminoethoxy)phenyl aglycon. The obtained... 相似文献
124.
Claudia Poloni Marc C. A. Stuart Pieter van der Meulen Wiktor Szymanski Ben L. Feringa 《Chemical science》2015,6(12):7311-7318
The external photocontrol over peptide folding, by the incorporation of molecular photoswitches into their structure, provides a powerful tool to study biological processes. However, it is limited so far to switches that exhibit only a rather limited geometrical change upon photoisomerization and that show thermal instability of the photoisomer. Here we describe the use of an overcrowded alkene photoswitch to control a model β-hairpin peptide. This photoresponsive unit undergoes a large conformational change and has two thermally stable isomers which has major influence on the secondary structure and the aggregation of the peptide, permitting the phototriggered formation of amyloid-like fibrils. 相似文献
125.
Metabolic profiles of dioscin in rats revealed by ultra‐performance liquid chromatography quadrupole time‐of‐flight mass spectrometry 下载免费PDF全文
He Zhu Jin‐Di Xu Qian Mao Hong Shen Ming Kong Jian‐Ping Chen Song‐Lin Li 《Biomedical chromatography : BMC》2015,29(9):1415-1421
Dioscin (DIS), one of the most abundant bioactive steroidal saponins in Dioscorea sp., is used as a complementary medicine to treat coronary disease and angina pectoris in China. Although the pharmacological activities and pharmacokinetics of DIS have been well demonstrated, information regarding the final metabolic fates is very limited. This study investigated the in vivo metabolic profiles of DIS after oral administration by ultra‐performance liquid chromatography quadrupole time‐of‐flight mass spectrometry method. The structures of the metabolites were identified and tentatively characterized by means of comparing the molecular mass, retention time and fragmentation pattern of the analytes with those of the parent compound. A total of eight metabolites, including seven phase I and one phase II metabolites, were detected and tentatively identified for the first time. Oxidation, deglycosylation and glucuronidation were found to be the major metabolic processes of the compound in rats. In addition, a possible metabolic pathway on the biotransformation of DIS in vivo was proposed. This study provides valuable and new information on the metabolism of DIS, which will be helpful for further understanding its mechanism of action. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
126.
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
127.
In this Letter,a novel system for adaptively correcting the phase of a dynamic multimode beam is proposed.While using merely one spatial light modulator,the phase measurement of the first-order diffraction pattern and the correction of the zeroth diffraction order are simultaneously realized.The real-time experimental result is obtained at a control rate of 10 Hz.The power-in-the-bucket value is improved from 38.5%to 61.8%,even with fundamental mode content that is consistently below 30%.To the best of our knowledge,this is the first implementation of real-time adaptive correction of the entire multimode beam. 相似文献
128.
129.
Crosslinked poly(ethylene oxide) containing siloxanes fabricated through thiol‐ene photochemistry 下载免费PDF全文
Victor A. Kusuma Elliot A. Roth William P. Clafshenkel Steven S. Klara Xu Zhou Surendar R. Venna Erik Albenze David R. Luebke Meagan S. Mauter Richard R. Koepsel Alan J. Russell David Hopkinson Hunaid B. Nulwala 《Journal of polymer science. Part A, Polymer chemistry》2015,53(13):1548-1557
Homogenous amphiphilic crosslinked polymer films comprising of poly(ethylene oxide) and polysiloxane were synthesized utilizing thiol‐ene “ click ” photochemistry. A systematic variation in polymer composition was Carried out to obtain high quality films with varied amount of siloxane and poly(ethylene oxide). These films showed improved gas separation performance with high gas permeabilities with good CO2/N2 selectivity. Furthermore, the resulting films were also tested for its biocompatibility, as a carrier media which allow human adult mesenchymal stem cells to retain their capacity for osteoblastic differentiation after transplantation. The obtained crosslinked films were characterized using differential scanning calorimetry, dynamic mechanical analysis, thermogravimetric analysis, FTIR, Raman‐IR , and small angle X‐ray scattering. The synthesis ease and commercial availability of the starting materials suggests that these new crosslinked polymer networks could find applications in wide range of applications. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1548–1557 相似文献
130.