全文获取类型
收费全文 | 5468篇 |
免费 | 546篇 |
国内免费 | 2篇 |
出版年
2022年 | 46篇 |
2021年 | 101篇 |
2020年 | 66篇 |
2019年 | 87篇 |
2018年 | 103篇 |
2017年 | 70篇 |
2016年 | 160篇 |
2015年 | 221篇 |
2014年 | 213篇 |
2013年 | 312篇 |
2012年 | 363篇 |
2011年 | 357篇 |
2010年 | 217篇 |
2009年 | 208篇 |
2008年 | 258篇 |
2007年 | 282篇 |
2006年 | 247篇 |
2005年 | 247篇 |
2004年 | 242篇 |
2003年 | 196篇 |
2002年 | 212篇 |
2001年 | 85篇 |
2000年 | 115篇 |
1999年 | 79篇 |
1998年 | 57篇 |
1997年 | 36篇 |
1996年 | 33篇 |
1995年 | 34篇 |
1994年 | 41篇 |
1993年 | 30篇 |
1992年 | 46篇 |
1991年 | 43篇 |
1990年 | 51篇 |
1989年 | 57篇 |
1988年 | 44篇 |
1987年 | 40篇 |
1986年 | 39篇 |
1985年 | 53篇 |
1984年 | 34篇 |
1983年 | 43篇 |
1982年 | 34篇 |
1981年 | 30篇 |
1980年 | 32篇 |
1979年 | 38篇 |
1976年 | 29篇 |
1975年 | 36篇 |
1974年 | 40篇 |
1973年 | 36篇 |
1971年 | 35篇 |
1968年 | 35篇 |
排序方式: 共有6016条查询结果,搜索用时 15 毫秒
1.
L V Melendez M D Daniel H H Barahona C E Fraser R D Hunt F G Garcia 《Laboratory animal science》1971,21(6):1050-1054
2.
3.
4.
Anna M. Kauppi Alicia Edin Ingrid Ziegler Paula M?lling Anders Sj?stedt ?sa Gylfe Kristoffer Str?lin Anders Johansson 《PloS one》2016,11(1)
A metabolomics approach for prediction of bacteremic sepsis in patients in the emergency room (ER) was investigated. In a prospective study, whole blood samples from 65 patients with bacteremic sepsis and 49 ER controls were compared. The blood samples were analyzed using gas chromatography coupled to time-of-flight mass spectrometry. Multivariate and logistic regression modeling using metabolites identified by chromatography or using conventional laboratory parameters and clinical scores of infection were employed. A predictive model of bacteremic sepsis with 107 metabolites was developed and validated. The number of metabolites was reduced stepwise until identifying a set of 6 predictive metabolites. A 6-metabolite predictive logistic regression model showed a sensitivity of 0.91(95% CI 0.69–0.99) and a specificity 0.84 (95% CI 0.58–0.94) with an AUC of 0.93 (95% CI 0.89–1.01). Myristic acid was the single most predictive metabolite, with a sensitivity of 1.00 (95% CI 0.85–1.00) and specificity of 0.95 (95% CI 0.74–0.99), and performed better than various combinations of conventional laboratory and clinical parameters. We found that a metabolomics approach for analysis of acute blood samples was useful for identification of patients with bacteremic sepsis. Metabolomics should be further evaluated as a new tool for infection diagnostics. 相似文献
5.
Alicia A. Gil de Pertierra 《Zoologischer Anzeiger》2005,243(4):307-304
The surface of the tegument of the scolex and the immature proglottides of Monticellia belavistensis, M. ventrei, Nomimoscolex chubbi, and N. lopesi is described using scanning electron microscopy. Only blade-like spiniform microtriches and filiform microtriches were observed in the species studied. The types, size and density of microtriches on the apical region surface of the scolex, central cavity surface of suckers, marginal ring surface of suckers, non-adherent surface of suckers, proliferation zone surface, and immature proglottis surface were compared among these species. The distribution pattern of the microtriches was not a reliable feature to discriminate among the genera considered in this study. It varied in each of the species of Monticellia examined, and did not permit to split the heterogeneous genus Nomimoscolex. However, the microthrix pattern can be regarded as an additional diagnostic feature to distinguish among species of proteocephalideans. Further comparative research involving other species of proteocephalid taxa is needed to elucidate the systematic value of the tegumental morphology. 相似文献
6.
7.
8.
Alicia P. Higueruelo Adrian Schreyer G. Richard J Bickerton Tom L. Blundell Will R. Pitt 《PloS one》2012,7(12)
Efforts to increase affinity in the design of new therapeutic molecules have tended to lead to greater lipophilicity, a factor that is generally agreed to be contributing to the low success rate of new drug candidates. Our aim is to provide a structural perspective to the study of lipophilic efficiency and to compare molecular interactions created over evolutionary time with those designed by humans. We show that natural complexes typically engage in more polar contacts than synthetic molecules bound to proteins. The synthetic molecules also have a higher proportion of unmatched heteroatoms at the interface than the natural sets. These observations suggest that there are lessons to be learnt from Nature, which could help us to improve the characteristics of man-made molecules. In particular, it is possible to increase the density of polar contacts without increasing lipophilicity and this is best achieved early in discovery while molecules remain relatively small. 相似文献
9.
10.
An electroporation protocol for the successful transfection of mouse lymphoblastoid cells has been developed. Two cell lines, a normal and a mutant sensitive to DNA cross-linking agents, were used. The optimum conditions of electroporation in terms of uptake of the fluorescent dye lucifer yellow coupled with low toxicity were established. Subsequently, these conditions were used to achieve stable transfection by a plasmid expression vector. The plasmid integration patterns were determined by Southern blot analysis. 相似文献