全文获取类型
收费全文 | 1136篇 |
免费 | 55篇 |
出版年
2022年 | 8篇 |
2021年 | 22篇 |
2020年 | 12篇 |
2019年 | 20篇 |
2018年 | 17篇 |
2017年 | 20篇 |
2016年 | 26篇 |
2015年 | 44篇 |
2014年 | 41篇 |
2013年 | 85篇 |
2012年 | 111篇 |
2011年 | 103篇 |
2010年 | 67篇 |
2009年 | 43篇 |
2008年 | 80篇 |
2007年 | 93篇 |
2006年 | 80篇 |
2005年 | 66篇 |
2004年 | 42篇 |
2003年 | 52篇 |
2002年 | 55篇 |
2001年 | 11篇 |
2000年 | 6篇 |
1999年 | 6篇 |
1998年 | 10篇 |
1997年 | 7篇 |
1996年 | 7篇 |
1995年 | 8篇 |
1994年 | 8篇 |
1993年 | 7篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1963年 | 1篇 |
1962年 | 1篇 |
1956年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有1191条查询结果,搜索用时 15 毫秒
241.
Rat immunoglobulin (IgG) was covalently bound to N-(2-hydroxypropyl)methacrylamide (HPMA) copolymers via glycylglycyl spacer. The resultant conjugate, free IgG and HPMA copolymer (containing a low percentage of tyrosinamide to facilitate radiolabelling) were radioiodinated, and their rates of pinocytic uptake, intracellular degradation and exocytic release by rat visceral yolk sacs culturedin vitro were determined. Free IgG was pinocytosed rapidly by the yolk sac and some IgG was subject to intracellular proteolysis. In comparison the IgG-HPMA copolymer conjugate was captured more slowly, but faster than unmodified HPMA. IgG was also exocytosed rapidly by the yolk sac following pinocytic capture and similarly IgG-HPMA copolymer had a much higher rate of release than unmodified H PMA. Measurement of tissue accumulation of125I-labelled IgG-H PMA copolymer in the presence of increasing concentrations of non-radiolabelled IgG showed competition for membrane binding sites between the free, and polymer-bound immunoglobulin. These experiments indicate that immunoglobulins can be covalently bound to a soluble polymer developed as a drug-carrier in such a way that they can still interact with specific membrane receptors and they are subsequently subjected to specific cellular transport mechanisms. 相似文献
242.
Renate H. Hans Eric M. Guantai Carmen Lategan Peter J. Smith Baojie Wan Scott G. Franzblau Jiri Gut Philip J. Rosenthal Kelly Chibale 《Bioorganic & medicinal chemistry letters》2010,20(3):942-944
A series of acetylenic chalcones were evaluated for antimalarial and antitubercular activity. The antimalarial data for this series suggests that growth inhibition of the W2 strain of Plasmodium falciparum can be imparted by the introduction of a methoxy group ortho to the acetylenic group. Most compounds were more active against non-replicating than replicating cultures of Mycobacterium tuberculosis H37Rv, an unusual pattern with respect to existing anti-TB agents. 相似文献
243.
244.
Tiago Rodrigues Rita C. Guedes Daniel J.V.A. dos Santos Marta Carrasco Jiri Gut Philip J. Rosenthal Rui Moreira Francisca Lopes 《Bioorganic & medicinal chemistry letters》2009,19(13):3476-3480
(1H-Pyridin-4-ylidene)amines containing lipophilic side chains at the imine nitrogen atom were prepared as potential clopidol isosteres in the development of antimalarials. Their antiplasmodial activity was evaluated in vitro against the Plasmodium falciparum W2 (chloroquine-resistant) and FCR3 (atovaquone-resistant) strains. The most active of these derivatives, 4m, had an IC50 of 1 μM against W2 and 3 μM against FCR3. Molecular modeling studies suggest that (1H-pyridin-4-ylidene)amines may bind to the ubiquinol oxidation Qo site of cytochrome bc1. 相似文献
245.
Frantisek Cervenka Vit Koleckar Zuzana Rehakova Ludek Jahodar Jiri Kunes Lubomir Opletal 《Journal of enzyme inhibition and medicinal chemistry》2013,28(4):574-578
In recent years, great attention has been given to the search for natural compounds or extracts with the purpose of medical use. Evolvulus alsinoides L. (Convolvulaceae) is a plant used in traditional medicine of East Asia in many indications and has known nootropic and anti-inflammatory activity. However, the bioactive constituents have been described poorly in the literature. Four substances isolated from the ethanol extract of E. alsinoides by means of polyamide and Silica-gel chromatography are reported here. Their molecular structures were determined using NMR analyses. There were identified as scopoletin, umbelliferone, scopolin and 2-methyl-1,2,3,4-butanetetrol. The quantity of these substances was determined using HPLC-UV and GC-FID detection. Antioxidant activity of the isolated substances was measured by DPPH assay using the SIA method. Antioxidant activity and total phenolic content of the prepared fractions are also described. The prepared fractions and isolated substances did not exhibit any significant activity in DPPH test. 相似文献
246.
247.
248.
Vadim Kotov Georg Mlynek Oliver Vesper Marina Pletzer Jiri Wald Celso M. Teixeira‐Duarte Herve Celia Maria Garcia‐Alai Stephan Nussberger Susan K. Buchanan Joo H. Morais‐Cabral Christian Loew Kristina Djinovic‐Carugo Thomas C. Marlovits 《Protein science : a publication of the Protein Society》2021,30(1):201-217
249.
Veronika Damkova Veronika Paskova Hana Bandouchova Klara Hilscherova Jana Sedlackova Ladislav Novotny Lucie Peckova Frantisek Vitula Miroslav Pohanka Jiri Pikula 《Harmful algae》2011,10(6):612-618
Previous studies demonstrated the toxic effects of cyanobacteria in Japanese quails (Coturnix coturnix japonica) in various experimental set-ups including acute, sub-chronic and reproduction toxicity, co-exposures with toxic metals and the Newcastle vaccination. This study aimed to assess the testicular toxicity of a complex cyanobacterial biomass administered to Japanese quails in the feed for eight weeks (daily dose of 61.62 μg microcystins pro toto including 26.54 μg MC-RR, 7.62 μg MC-YR and 27.39 μg MC-LR). There was no mortality in the controls or the biomass-exposed birds. However, males exposed to cyanobacteria in the feed showed moderate to marked atrophy of the seminiferous tubular epithelium with only sparse numbers of the developmental stages of spermatozoa and Sertoli cells. Biomass-exposed birds had elevated catalase activities but decreased glutathione peroxidase activities and surprisingly lower levels of lipid peroxides in the testes. The other biochemical parameters studied (i.e., glutathione level and glutathione reductase, glutathione-S-transferase and superoxide dismutase activities) showed no differences. The cell defensive system protecting testicular tissue from the damage associated with toxic effects of the complex cyanobacterial biomass seemed to be insufficient and partly depleted after the chronic exposure of male birds to this biomass. 相似文献
250.
The aim of the study was to evaluate the exclusivity and/or preference of macroinvertebrate taxa for river habitats. Indicator
species analysis and random forests methods were applied to the data set of macroinvertebrate samples taken from 58 sampling
points. Samples were classified according to habitat types defined by the position in a river channel and local hydraulic
characteristics. 86 macroinvertebrate taxa were included in the analyses. High indicative values for habitats (importance
value ≥50 and/or indicator value ≥40) were identified for 26 taxa. The results of both methods can be considered similar.
Merged habitats of channel margin (margin of main channel and side arms) were mainly defined by “negative” indicator taxa
(correct classification of given samples was caused by non-occurrence and low abundances of certain taxa in this habitat).
In general, there was only a small group of taxa preferring these habitats. Taxa were not fully habitat specific because they
mostly occurred in two or three habitat types. This could be the result of autecological plasticity of individual taxa and
the connectivity among habitats. According to the experience from this case study, it can be concluded that both random forests
and IndVal methods are suitable for the detection of indicative species, and random forests method has some additional advantages. 相似文献