全文获取类型
收费全文 | 25835篇 |
免费 | 4393篇 |
国内免费 | 5715篇 |
专业分类
化学 | 19642篇 |
晶体学 | 691篇 |
力学 | 1601篇 |
综合类 | 537篇 |
数学 | 2819篇 |
物理学 | 10653篇 |
出版年
2024年 | 59篇 |
2023年 | 343篇 |
2022年 | 806篇 |
2021年 | 796篇 |
2020年 | 875篇 |
2019年 | 842篇 |
2018年 | 718篇 |
2017年 | 821篇 |
2016年 | 1071篇 |
2015年 | 1155篇 |
2014年 | 1387篇 |
2013年 | 1889篇 |
2012年 | 2132篇 |
2011年 | 2291篇 |
2010年 | 1837篇 |
2009年 | 1793篇 |
2008年 | 2037篇 |
2007年 | 1725篇 |
2006年 | 1795篇 |
2005年 | 1675篇 |
2004年 | 1300篇 |
2003年 | 1065篇 |
2002年 | 1157篇 |
2001年 | 967篇 |
2000年 | 959篇 |
1999年 | 662篇 |
1998年 | 451篇 |
1997年 | 394篇 |
1996年 | 367篇 |
1995年 | 354篇 |
1994年 | 297篇 |
1993年 | 283篇 |
1992年 | 275篇 |
1991年 | 213篇 |
1990年 | 215篇 |
1989年 | 170篇 |
1988年 | 138篇 |
1987年 | 115篇 |
1986年 | 107篇 |
1985年 | 96篇 |
1984年 | 64篇 |
1983年 | 55篇 |
1982年 | 35篇 |
1981年 | 39篇 |
1980年 | 25篇 |
1979年 | 25篇 |
1978年 | 13篇 |
1965年 | 7篇 |
1964年 | 7篇 |
1957年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Star copolymers have attracted significant interest due to their different characteristics compared with diblock copolymers, including higher critical micelle concentration, lower viscosity, unique spatial shape, or morphologies. Development of synthetic skills such as anionic polymerization and controlled radical polymerization have made it possible to make diverse architectures of polymers. Depending on the molecular architecture of the copolymer, numerous morphologies are possible, for instance, Archimedean tiling patterns and cylindrical microdomains at symmetric volume fraction for miktoarm star copolymers as well as asymmetric lamellar microdomains for star‐shaped copolymers, which have not been reported for linear block copolymers. In this review, we focus on morphologies and microphase separations of miktoarm (AmBn and ABC miktoarm) star copolymers and star‐shaped [(A‐b‐B)n] copolymers with nonlinear architecture. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1–21 相似文献
3.
4.
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
5.
6.
DING Bin-Gang ZHANG Da-Li LU Ding-Hui 《理论物理通讯》2006,46(1):113-118
We calculate the binding energies of Ni, Cu, Xe, Cs, Pt, Au, Np, Pu isotope chains using two interaction parameter sets NL-3 and NL-Z, and compared the relative errors of the even-even nuclei with those of odd-even nuclei and odd-odd nuclei. We find that the errors of binding energy of odd-even and odd-odd nuclei are not bigger than the one of even-even nuclei. The result shows that comparing with even-even nuclei, there is no systematic error and approximation in the calculations of the binding energy of odd-even and odd-odd nuclei with relativistic mean-field theory. In addition, the result is explained theoretically. 相似文献
7.
Guofen Yu Yuanci Gao Shenggang Liu Wenxiang Wang Jin Wu 《International Journal of Infrared and Millimeter Waves》2002,23(8):1261-1269
Analysis of the field distributions in a single biological cell under electromagnetic wave is given. With Debye approximation, the dielectric relaxation of each part of the cell, including the extracellular and cellular media, the cell membrane and the nuclear membrane, was taken into account. Making use of some typical parameters for a cell, the voltage across nuclear and cytoplasma membranes under electromagnetic waves are calculated up to millimeter wave frequency range. The calculated result indicates that it is unlikely to generate electroporation by present available millimeter wave sources. 相似文献
8.
非线性奇异边值问题的正解 总被引:1,自引:0,他引:1
路慧芹 《应用泛函分析学报》2002,4(3):217-221
利用锥映射的不动点指数定量,研究了一类非线性奇异边值问题多个正解的存在性问题。在构造的解的存在条件之下,证明了奇异边值问题至少有两个正解的存在性定理。 相似文献
9.
Syntheses, structures, and properties of novel molybdenum and tungsten complexes of fullerenes 总被引:1,自引:0,他引:1
The synthesis and characterization of several fullerene-based organometallic complexes containing Mo and W is reported. 相似文献
10.
Jong Chan Lee Jin Young Park So Young Yoon Yong Hun Bae Seung Jun Lee 《Tetrahedron letters》2004,45(1):191-193
A novel and direct method for the synthesis of α-halocarbonyl compounds using sequential treatment of carbonyl compounds with [hydroxy(tosyloxy)iodo]benzene followed by magnesium halides under solvent-free microwave irradiation conditions is described. 相似文献