全文获取类型
收费全文 | 343篇 |
免费 | 32篇 |
专业分类
375篇 |
出版年
2022年 | 2篇 |
2021年 | 6篇 |
2020年 | 2篇 |
2019年 | 3篇 |
2018年 | 7篇 |
2017年 | 6篇 |
2016年 | 4篇 |
2015年 | 11篇 |
2014年 | 16篇 |
2013年 | 13篇 |
2012年 | 16篇 |
2011年 | 19篇 |
2010年 | 15篇 |
2009年 | 10篇 |
2008年 | 16篇 |
2007年 | 8篇 |
2006年 | 11篇 |
2005年 | 11篇 |
2004年 | 17篇 |
2003年 | 10篇 |
2002年 | 9篇 |
2001年 | 12篇 |
2000年 | 17篇 |
1999年 | 10篇 |
1998年 | 9篇 |
1997年 | 3篇 |
1996年 | 7篇 |
1995年 | 5篇 |
1992年 | 7篇 |
1991年 | 2篇 |
1990年 | 6篇 |
1988年 | 3篇 |
1987年 | 9篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1982年 | 2篇 |
1979年 | 9篇 |
1978年 | 8篇 |
1977年 | 2篇 |
1975年 | 7篇 |
1974年 | 3篇 |
1973年 | 6篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1970年 | 3篇 |
1968年 | 2篇 |
1967年 | 3篇 |
1954年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有375条查询结果,搜索用时 15 毫秒
1.
2.
Genetic identification of rat liver carboxylesterases isolated in different laboratories 总被引:3,自引:0,他引:3
R Mentlein A Ronai M Robbi E Heymann O von Deimling 《Biochimica et biophysica acta》1987,913(1):27-38
Six carboxylesterases previously isolated from rat liver microsomes, characterized in Brussels and in Kiel, were compared with genetically defined liver esterases of various reference strains using polyacrylamide gel electrophoresis and isoelectric focusing. The six liver carboxylesterases were identified as alloenzymic forms of ES-3, ES-4, ES-8/ES-10 and ES-15 according to the genetic nomenclature recommended by van Zutphen (Van Zutphen, L.F.M. (1983) Transplant. Proceed. 15, 1687-1688). The genetic and biochemical characteristics of the four isoenzymes are summarized, and their identity with several other drug-metabolizing esterases/amidases and lipases of rat liver endoplasmic reticulum is discussed. 相似文献
3.
N S Cherniack G S Longobardo F P Palermo M Heymann 《Journal of applied physiology》1968,24(6):809-816
4.
5.
Eckhard W. Heymann 《International journal of primatology》1990,11(4):327-337
During a field study in northeastern Peru, the reactions of a group ofSaguinus mystax on Padre Isla and of a mixed-species troop ofS. mystax andSaguinus fuscicollis at the Río Blanco to raptorial and other birds were observed. Alarms that are specific to flying stimuli were elicited by birds of prey, but other birds that do not represent a threat to the tamarins also caused alarm calls. Alarm events (i.e., instances when one or more alarm calls were given) were observed at rates of 0.3/hr (Padre Isla) and 0.5/hr (Río Blanco). Rates of alarm events significantly increased after the birth of an infant in the Padre Isla group and after the attack of an ornate hawk-eagle (Spizaetus ornatus) on the Río Blanco group. Reactions to alarming stimuli/alarm calls ranged from looking up to falling down from trees. The modification of the tamarins' behavior by the potential presence of aerial predators indicates that raptors represent an important predatory threat to tamarins. 相似文献
6.
Sarina Thiel Franziska Willems Nina Farwig Finn Rehling Dana G. Schabo Matthias Schleuning Ney Shahuano Tello Till Töpfer Marco Tschapka Eckhard W. Heymann Katrin Heer 《Biotropica》2023,55(3):650-664
Vertical stratification is a key feature of tropical forests and structures plant–frugivore interactions. However, it is unclear whether vertical differences in plant-frugivore interactions are due to differences among strata in plant community composition or inherent preferences of frugivores for specific strata. To test this, we observed fruit removal of a diverse frugivore community on the liana Marcgravia longifolia in a Peruvian rain forest. Unlike most other plants, Marcgravia longifolia produces fruits across forest strata. This enabled us to study effects of vertical stratification on fruit removal without confounding effects of plant species and stratum. We found a high number of visits of a few frugivore species in the understorey and a low number of visits of many different frugivores in the canopy and midstorey. Whereas partial and opportunistic frugivores foraged across strata with differing frequencies, obligate frugivores were only found eating fruits in the higher strata. Avian frugivores foraging in the canopy were mainly large species with pointed wings, whereas under- and midstorey avian foragers were smaller with rounded wings. Our findings suggest a continuous shift in the frugivore community composition along the vertical gradient, from a few generalized frugivores in the understorey to a diverse set of specialized frugivores in the canopy. This shift in the frugivore community leads to correlated, reciprocal changes from specialized to generalized plant-frugivore interactions. Thus, we conclude that vertical niche differentiation between species in tropical forests persists even when food resources are available across strata. This highlights its role for promoting biodiversity and ecosystem functioning. 相似文献
7.
Ronald I. Clyman Louise Wong Michael A. Heymann Abraham M. Rudolph 《Prostaglandins & other lipid mediators》1978,15(2):325-331
The relative potencies of the prostaglandins A1, A2, E1, E2, F2α and their 15-keto-, 15-keto-13,14-dihydro-, and 13,14-dihydro-metabolites were investigated on isolated lamb ductus arteriosus preparations contracted by exposure to elevated PO2. All the prostaglandins (except PGF2α and its 15-keto-metabolites) relaxed the tissue. However, only PGE1, E2, and their 13,14-dihydro-metabolites, were effective at concentrations below 10−8 M. Therefore, events that alter metabolism of circulating PGs in the perinatal period may have significant effects on the relative patency or closure of the ductus arteriosus. 相似文献
8.
A highly purified dipeptidyl peptidase IV from human placenta cleaves glycylproline from the N-terminal end of the fibrin α chain and inhibits the clotting of fibrin monomers. This result underlines the importance of the amino terminus of the fibrin α chain as an aggregation site masked by fibrinopeptide A. We speculate that the peptidase may hinder blood coagulation in intact vessels in vivo, because it is located on the surface of the capillary endothelium. 相似文献
9.
Gold salts and phenylbutazone selectively inhibit the synthesis of PGF2α and PGE2 respectively. Lowered production of one prostaglandin species is accompanied by an increased production of the other. Selective inhibition by these drugs was observed in the presence of adrenaline, reduced glutathione and copper sulphate under conditions when most anti-inflammatory compounds inhibited PGE2 and PGF2α syntheses equally. It is postulated that selective inhibitors may have a different mode of action
and beneficial effects may be related to the endogenous ratio of PGE to PGF required for normal function. 相似文献
10.
The degradation of bioactive peptides and proteins by dipeptidyl peptidase IV from human placenta 总被引:2,自引:0,他引:2
The degradation of several bioactive peptides and proteins by purified human dipeptidyl peptidase IV is reported. It was hitherto unknown that human gastrin-releasing peptide, human chorionic gonadotropin, human pancreatic polypeptide, sheep prolactin, aprotinin, corticotropin-like intermediate lobe peptide and (Tyr-)melanostatin are substrates of this peptidase. Kinetic constants were determined for the degradation of a number of other natural peptides, including substance P, the degradation of which has been described earlier in a qualitative manner. Generally, small peptides are degraded much more rapidly than proteins. However, the Km-values seem to be independent of the peptide chain length. The influence of the action of dipeptidyl peptidase IV on the biological function of peptides and proteins is discussed. 相似文献