全文获取类型
收费全文 | 23750篇 |
免费 | 4106篇 |
国内免费 | 3018篇 |
专业分类
化学 | 17187篇 |
晶体学 | 252篇 |
力学 | 1668篇 |
综合类 | 165篇 |
数学 | 2637篇 |
物理学 | 8965篇 |
出版年
2024年 | 88篇 |
2023年 | 502篇 |
2022年 | 912篇 |
2021年 | 881篇 |
2020年 | 976篇 |
2019年 | 922篇 |
2018年 | 835篇 |
2017年 | 770篇 |
2016年 | 1231篇 |
2015年 | 1098篇 |
2014年 | 1400篇 |
2013年 | 1753篇 |
2012年 | 2141篇 |
2011年 | 2176篇 |
2010年 | 1460篇 |
2009年 | 1391篇 |
2008年 | 1644篇 |
2007年 | 1416篇 |
2006年 | 1253篇 |
2005年 | 1128篇 |
2004年 | 814篇 |
2003年 | 673篇 |
2002年 | 648篇 |
2001年 | 542篇 |
2000年 | 463篇 |
1999年 | 476篇 |
1998年 | 403篇 |
1997年 | 362篇 |
1996年 | 398篇 |
1995年 | 384篇 |
1994年 | 293篇 |
1993年 | 229篇 |
1992年 | 230篇 |
1991年 | 208篇 |
1990年 | 175篇 |
1989年 | 133篇 |
1988年 | 113篇 |
1987年 | 95篇 |
1986年 | 63篇 |
1985年 | 62篇 |
1984年 | 38篇 |
1983年 | 32篇 |
1982年 | 17篇 |
1981年 | 21篇 |
1980年 | 10篇 |
1978年 | 2篇 |
1972年 | 1篇 |
1959年 | 1篇 |
1957年 | 8篇 |
1936年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
Rui Feng Yong Zhang He Li Dan Wu Xiaodong Xin Sen Zhang Haiqin Yu Qin Wei Bin Du 《Analytica chimica acta》2013
Nano-montmorillonites belong to aluminosilicate clay minerals with innocuity, high specific surface area, ion exchange, and favorable adsorption property. Due to the excellent properties, montmorillonites can be used as labels for the electrochemical immunosensors. In this study, nano-montmorillonites were converted to sodium montmorillonites (Na-Mont) and further utilized for the immobilization of thionine (TH), horseradish peroxidase (HRP) and the secondary anti-zeranol antibody (Ab2). The modified particles, Na-Mont-TH-HRP-Ab2 were used as labels for immunosensors to detect zeranol. This protocol was used to prepare the immunosensor with the primary antibody (Ab1) immobilized onto the nanoporous gold films (NPG) modified glassy carbon electrode (GCE) surface. Within zeranol concentration range (0.01–12 ng mL−1), a linear calibration plot (Y = 0.4326 + 8.713 X, r = 0.9996) was obtained with a detection limit of 3 pg mL−1 under optimal conditions. The proposed immunosensor showed good reproducibility, selectivity, and stability. This new type of immunosensors with montmorillonites and NPG as labels may provide potential applications for the detection of zeranol. 相似文献
962.
963.
964.
965.
Strobilurins have become one of the most important classes of agricultural fungicides. To search for new strobilurin derivatives with high activity against resistant pathogens, a series of new β‐methoxyacrylate analogues containing substituted pyrimidine in the side chain with strobilurin pharmacophore were synthesized and their biological activities were tested. The compounds were confirmed and characterized by 1H‐NMR, elemental analysis and mass spectroscopy. The bioassays indicated that most of the compounds 1 exhibited potent antifungal activities against Colletotrichum orbiculare, Botrytis cinerea Pers and Phytophthora capsici Leonian at a concentration of 50 μg mL?1. Notably, compound 1b (R = 2,5‐dimethylphenyl) showed better antifungal activity against all the tested fungi than the commercial strobilurin fungicide azoxystrobin. 相似文献
966.
Pyrrole was polymerized on the surface of titanium foam using FeCl3 as oxidant and the as-synthesized product could be directly used as electrode for supercapacitor. The globular polypyrrole (PPy) particles were firmly loaded on the substrate with high density. The morphology study of PPy film is observed in SEM images, the XRD, FTIR and UV–vis spectra reveal the structure and crystalline of PPy nanoparticles. The electrochemical properties of PPy modified electrode are investigated by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and cycle life techniques. The electrochemical measurements showed such a PPy–Ti electrode had a wide working potential window, a high specific capacitance of 855 F g−1 and excellent cycle stability at a discharge current density of 1 A g−1. 相似文献
967.
Jian‐You Li Ying Peng Ling‐Zhi Li Pin‐Yi Gao Chang Gao Su‐Xia Xia Shao‐Jiang Song 《Helvetica chimica acta》2013,96(2):313-319
Two new abietane‐type diterpenoids, named triptobenzene R ( 1 ) and triptobenzene S ( 2 ), together with three known abietane‐type diterpenoids, triptophenolide ( 3 ), triptonodiol ( 4 ), and triptonoterpene methyl ether ( 5 ), were isolated from the roots of Tripterygium wilfordii Hook . f. Their structures and relative configurations were established by detailed spectral studies, including 1D‐ and 2D‐NMR (HSQC, HMBC, and NOESY), and HR‐ESI‐TOF‐MS, and by comparison with published data. Their absolute configurations were assigned by the CD technique, applied for the first time to abietane diterpenes from Tripterygium wilfordii. Compound 2 is the first abietane‐type norditerpenoid isolated from the genus Tripterygium. 相似文献
968.
2‐Alkylthio‐3‐alkyl‐5‐phenylmethylidene‐4H‐imidazol‐4‐ones 6 were synthesized by N‐alkylation and S‐alkylation of 2‐thioxo‐5‐phenylmethylidene‐4‐imidazolidinone 5, which was obtained via cyclization of vinyl isothiocyanate 4 with excess ammonium hydroxide (28% NH3 in water). 相似文献
969.
One-pot etherification reaction of aromatic and some aliphatic carbonyl compounds with organic halides in the presence of sodium hydride as a reducing reagent proceeded smoothly in dioxane, a polar solvent with higher boiling point, to provide desired ethers in moderate to high yields. 相似文献
970.
The Knoevenagel condensation of Meldrum's acid with aromatic aldehydes proceeded efficiently in a reusable ionic liquid, ethylammonium nitrate, at room temperature in the absence of any catalyst with high yields. 相似文献