全文获取类型
收费全文 | 3069篇 |
免费 | 245篇 |
国内免费 | 2篇 |
专业分类
3316篇 |
出版年
2022年 | 49篇 |
2021年 | 88篇 |
2020年 | 42篇 |
2019年 | 55篇 |
2018年 | 69篇 |
2017年 | 52篇 |
2016年 | 86篇 |
2015年 | 140篇 |
2014年 | 182篇 |
2013年 | 210篇 |
2012年 | 242篇 |
2011年 | 209篇 |
2010年 | 151篇 |
2009年 | 115篇 |
2008年 | 169篇 |
2007年 | 143篇 |
2006年 | 156篇 |
2005年 | 125篇 |
2004年 | 122篇 |
2003年 | 118篇 |
2002年 | 106篇 |
2001年 | 34篇 |
2000年 | 28篇 |
1999年 | 28篇 |
1998年 | 23篇 |
1997年 | 16篇 |
1996年 | 19篇 |
1995年 | 13篇 |
1994年 | 20篇 |
1993年 | 18篇 |
1992年 | 27篇 |
1991年 | 27篇 |
1990年 | 19篇 |
1989年 | 20篇 |
1988年 | 14篇 |
1987年 | 26篇 |
1986年 | 22篇 |
1985年 | 18篇 |
1984年 | 25篇 |
1983年 | 17篇 |
1982年 | 19篇 |
1981年 | 13篇 |
1979年 | 27篇 |
1976年 | 13篇 |
1975年 | 18篇 |
1974年 | 18篇 |
1973年 | 16篇 |
1972年 | 15篇 |
1971年 | 14篇 |
1970年 | 15篇 |
排序方式: 共有3316条查询结果,搜索用时 0 毫秒
61.
62.
Seung Hyun Han Seongjun Kim Hanna Chang Hyun-Jun Kim Asia Khamzina Yowhan Son 《Journal of Plant Ecology》2019,12(5):871
Aims
Assessment of factors regulating root decomposition is needed to understand carbon and nutrient cycling in forest ecosystems. The objective of this study is to examine the effects of soil depth and root diameter on root decomposition and to analyze the relationship of root decomposition with factors such as soil environmental conditions and initial litter quality. 相似文献
63.
Nieznanski K Podlubnaya ZA Nieznanska H 《Biochemical and biophysical research communications》2006,349(1):391-399
A growing body of evidence points to an association of prion protein (PrP) with microtubular cytoskeleton. Recently, direct binding of PrP to tubulin has also been found. In this work, using standard light scattering measurements, sedimentation experiments, and electron microscopy, we show for the first time the effect of a direct interaction between these proteins on tubulin polymerization. We demonstrate that full-length recombinant PrP induces a rapid increase in the turbidity of tubulin diluted below the critical concentration for microtubule assembly. This effect requires magnesium ions and is weakened by NaCl. Moreover, the PrP-induced light scattering structures of tubulin are cold-stable. In preparations of diluted tubulin incubated with PrP, electron microscopy revealed the presence of approximately 50 nm disc-shaped structures not reported so far. These unique tubulin oligomers may form large aggregates. The effect of PrP is more pronounced under the conditions promoting microtubule formation. In these tubulin samples, PrP induces formation of the above oligomers associated with short protofilaments and sheets of protofilaments into aggregates. Noticeably, this is accompanied by a significant reduction of the number and length of microtubules. Hence, we postulate that prion protein may act as an inhibitor of microtubule assembly by inducing formation of stable tubulin oligomers. 相似文献
64.
Dayue Du Hanna He Ruixin Zheng Li Zeng Xinxiang Wang Chaozhu Shu Chuhong Zhang 《Liver Transplantation》2024,14(17):2304238
Understanding and modulating the unique electronic interaction between single-metal atoms and high entropy compounds are of great significance to enable their high-efficiency oxygen electrocatalysis for aprotic lithium-oxygen (Li-O2) batteries. Herein, a novel bi-functional electrocatalyst is for the first time created by immobilizing single-atom ruthenium (Ru) on lanthanum-based high entropy perovskite oxide La(Mn0.2Co0.2Fe0.2Ni0.2Cr0.2)O3 (Ru@HEPO), which demonstrates high activity and stability in Li-O2 batteries. The heteronuclear coordination between single-atom Ru and HEPO facilitates fast electron transfer from Ru to HEPO by establishing Ru-O-M (M stands for Mn, Co, Fe, Ni) bridges, which well redistributes electrons within the Ru@HEPO hence significantly improving its interfacial charge transfer kinetics and electrocatalytic activity. Additionally, the strong electron coupling between Ru and Mn atoms enhances the hybridization between Mn 3d and O 2p orbitals, which promotes the inherent affinity of Ru@HEPO toward the LiO2 intermediate, thereby reducing the reaction energy barrier of the oxygen electrode. As a result, the Ru@HEPO-based Li-O2 batteries deliver remarkable electrochemical performances, such as high energy efficiency (87.3% at 100 mA g−1), excellent rate capability (low overpotential of 0.52 V at 100 mA g−1) and durable cyclability (345 cycles at 300 mA g−1). This work opens up a promising avenue for the development of high entropy-based electrocatalysts for Li-O2 batteries by precisely tailoring the electronic distributions at an atomic scale. 相似文献
65.
66.
67.
68.
Luiz Henrique Soares de Andrade Wilson Max Almeida Monteiro de Moraes Eduardo Hiroshi Matsuo Junior Elizabeth de Orleans Carvalho de Moura Hanna Karen Moreira Antunes Jairo Montemor Ednei Luiz Antonio Danilo Sales Bocalini Andrey Jorge Serra Paulo José Ferreira Tucci Patricia Chakur Brum Alessandra Medeiros 《Molecular and cellular biochemistry》2015,402(1-2):193-202
69.
Hanna Grajek Regina Drabent Grażyna Żurkowska Czesław Bojarski 《Biochimica et Biophysica Acta (BBA)/General Subjects》1984,801(3):456-460
The electronic absorption spectra of the flavomononucleotide (FMN) in aqueous solution and in glycerine-water solution with change of the dye concentration have been measured. The FMN dimer absorption spectrum, monomer absorption spectrum, dimerization constant K and molar fraction of the monomer were calculated. It was found that FMN dimerization constants in aqueous solution were Ka = 118.0 l/mol and in glycerine Kg = 20.5 l/mol. In the region of the monomer absorption band two dimer absorption bands appear, in accordance with the Kasha molecular exciton theory. 相似文献
70.
J L Templeton R A Spence T L Kennedy T G Parks G Mackenzie W A Hanna 《BMJ (Clinical research ed.)》1983,286(6375):1387-1389
One hundred and thirty seven previously untreated out-patients with first and second degree haemorrhoids were allocated at random to treatment by infrared coagulation (n=66) or rubber band ligation (n=71). Complete follow up was obtained in 122 patients (60 who had undergone infrared coagulation (group 1), and 62 rubber band ligation (group 2)) at periods from three months to one year after completion of treatment. Infrared coagulation produced a satisfactory outcome in 51 patients (85%): 34 were rendered asymptomatic and 17 improved. Rubber band ligation produced a satisfactory outcome in 57 patients (92%): 33 were rendered asymptomatic and 24 improved. Both methods were equally effective in first and second degree haemorrhoids. The incidence of side effects, particularly discomfort, during and after treatment was significantly higher in those treated by rubber band ligation (p less than 0.001). This appeared to be an appreciable deterrent to future patient compliance. The number of patients losing more than 24 hours from work was higher after rubber band ligation than after infrared coagulation. The number of treatments necessary to cure symptoms did not differ significantly between the two methods. Infrared coagulation was significantly faster than rubber band ligation (p less than 0.001). Infrared coagulation is a simple, fast, and effective outpatient method for the treatment of first and second degree haemorrhoids with fewer troublesome side effects and higher patient acceptability than rubber band ligation. 相似文献