全文获取类型
收费全文 | 10876篇 |
免费 | 1651篇 |
国内免费 | 1963篇 |
专业分类
化学 | 8984篇 |
晶体学 | 146篇 |
力学 | 562篇 |
综合类 | 203篇 |
数学 | 1189篇 |
物理学 | 3406篇 |
出版年
2024年 | 35篇 |
2023年 | 177篇 |
2022年 | 319篇 |
2021年 | 339篇 |
2020年 | 443篇 |
2019年 | 457篇 |
2018年 | 411篇 |
2017年 | 369篇 |
2016年 | 538篇 |
2015年 | 554篇 |
2014年 | 706篇 |
2013年 | 775篇 |
2012年 | 908篇 |
2011年 | 959篇 |
2010年 | 774篇 |
2009年 | 729篇 |
2008年 | 792篇 |
2007年 | 680篇 |
2006年 | 619篇 |
2005年 | 569篇 |
2004年 | 545篇 |
2003年 | 422篇 |
2002年 | 511篇 |
2001年 | 419篇 |
2000年 | 332篇 |
1999年 | 246篇 |
1998年 | 145篇 |
1997年 | 100篇 |
1996年 | 117篇 |
1995年 | 109篇 |
1994年 | 67篇 |
1993年 | 58篇 |
1992年 | 45篇 |
1991年 | 53篇 |
1990年 | 38篇 |
1989年 | 30篇 |
1988年 | 23篇 |
1987年 | 21篇 |
1986年 | 14篇 |
1985年 | 11篇 |
1984年 | 2篇 |
1983年 | 7篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1975年 | 3篇 |
1957年 | 2篇 |
1936年 | 2篇 |
1916年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
42.
A difference setD in a groupG is called a skew Hadamard difference set (or an antisymmetric difference set) if and only ifG is the disjoint union ofD, D(–1), and {1}, whereD(–1)={d–1|dD}. In this note, we obtain an exponent bound for non-elementary abelian groupG which admits a skew Hadamard difference set. This improves the bound obtained previously by Johnsen, Camion and Mann. 相似文献
43.
44.
Qing Liu 《Transactions of the American Mathematical Society》1996,348(11):4577-4610
Let be a hyperelliptic curve of genus over a discrete valuation field . In this article we study the models of over the ring of integers of . To each Weierstrass model (that is a projective model arising from a hyperelliptic equation of with integral coefficients), one can associate a (valuation of) discriminant. Then we give a criterion for a Weierstrass model to have minimal discriminant. We show also that in the most cases, the minimal regular model of over dominates every minimal Weierstrass model. Some classical facts concerning Weierstrass models over of elliptic curves are generalized to hyperelliptic curves, and some others are proved in this new setting.
45.
Unlabeled fluoroimmunoassay with a europium chelate is described. The recommended method is simple because the complicated labeling process is omitted. The recovery of some samples ranges from 91 to 111%. The relative standard deviation of the method is less than 10%. The detection limit is about 10−10mol liter−1antigen. 相似文献
46.
An efficient synthesis of (+/-)-leporin A (1) has been developed using a tandem Knoevenagel condensation-inverse electron demand intramolecular hetero Diels-Alder reaction to construct the key tricyclic intermediate 3 from pyridone 5 and dienal 6 in one pot in 35% yield. Hydroxylation (71%) of 3 and methylation (77%) of the resulting hydroxypyridone 2 completed the first total synthesis of (+/-)-leporin A (1). 相似文献
47.
Liu Q Fang D Zheng J 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(7):1453-1457
Infrared spectroscopy studies of methyl 4-hydroxybenzoate (MHB) in 17 different organic solvents and in ethanol/CCl4 binary solvent were undertaken to investigate the solvent-solute interactions. The frequencies of carbonyl stretching vibration nu(C=O) of MHB in single solvents were correlated with the solvent acceptor number (AN) and the linear solvation energy relationships (LSER). The assignments of the two bands of nu(C=O) of MHB in alcohols and the single one of that in non-alcoholic solvents were discussed. The shifts of nu(C=O) of MHB in ethanol/CCl4 binary solvents showed that several kinds of solute-solvent hydrogen bonding interactions coexisted in the mixture solvents, with a change in the mole fraction of ethanol in the binary solvents. 相似文献
48.
ZHOU Hai-cheng XU Sheng PENG Qing LI Ya-dong 《高等学校化学研究》2006,22(1):11-13
IntroductionNano-sized semiconductors are of great interestdue to their special optical and electronic proper-ties[1,2].As one of the mostimportantⅡ—Ⅵsemicon-ductors,CdS has importantapplications in many fields,such as the solar cell field,non linear o… 相似文献
49.
Synthesis, Structure and Conductivity of the New Charge-transfer Salt (ET)_2(CH_2=CH-CH_2-SO_3)·H_2O
Zhi LIU Qi FANG* Wen Tao YU Min Hua JIANG De Qing ZHANG Dao Ben ZHU State Key Laboratory of Crystal Materials Shandong University Jinan Institute of Chemistry The Chinese Academy of Sciences Beijing 《中国化学快报》2003,14(4)
ET is one of the most famous electron-donor molecules, which forms charge-transfer complexes (abbr. CT-complexes) with various types of counterions. These complexes have received intense attention because a wide range of physical properties such as conductivity and superconductivity1, ferromagnetism2-4 and nonlinear optical properties5 was found in these materials. Although the majority of the ET-based CT-complexes were prepared by combining with inorganic counterions, CT-complexes with o… 相似文献
50.