全文获取类型
收费全文 | 1240篇 |
免费 | 93篇 |
出版年
2022年 | 18篇 |
2021年 | 35篇 |
2020年 | 17篇 |
2019年 | 15篇 |
2018年 | 27篇 |
2017年 | 21篇 |
2016年 | 36篇 |
2015年 | 60篇 |
2014年 | 60篇 |
2013年 | 78篇 |
2012年 | 85篇 |
2011年 | 94篇 |
2010年 | 47篇 |
2009年 | 48篇 |
2008年 | 66篇 |
2007年 | 80篇 |
2006年 | 55篇 |
2005年 | 50篇 |
2004年 | 50篇 |
2003年 | 33篇 |
2002年 | 48篇 |
2001年 | 13篇 |
2000年 | 8篇 |
1999年 | 16篇 |
1998年 | 9篇 |
1997年 | 5篇 |
1996年 | 8篇 |
1995年 | 5篇 |
1993年 | 10篇 |
1992年 | 8篇 |
1991年 | 10篇 |
1990年 | 13篇 |
1989年 | 9篇 |
1988年 | 7篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 11篇 |
1984年 | 12篇 |
1983年 | 11篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1979年 | 20篇 |
1978年 | 6篇 |
1977年 | 9篇 |
1976年 | 5篇 |
1974年 | 4篇 |
1973年 | 7篇 |
1968年 | 6篇 |
1892年 | 3篇 |
排序方式: 共有1333条查询结果,搜索用时 203 毫秒
921.
Glen Lovell L. Bueser Kharina G. Bueser Donald S. Afan Dennis I. Salvador James W. Grier Robert S. Kennedy & Hector C. Miranda Jr 《Ibis》2003,145(1):130-135
The Philippine Eagle Pithecophaga jefferyi , first discovered in 1896, is one of the world's most endangered eagles. It has been reported primarily from only four main islands of the Philippine archipelago. We have studied it extensively for the past three decades. Using data from 1991 to 1998 as best representing the current status of the species on the island of Mindanao, we estimated the mean nearest-neighbour distances between breeding pairs, with remarkably little variation, to be 12.74 km ( n = 13 nests plus six pairs without located nests, se = ±0.86 km, range = 8.3–17.5 km). Forest cover within circular plots based on nearest-neighbour pairs, in conjunction with estimates of remaining suitable forest habitat (approximately 14 000 km2 ), yield estimates of the maximum number of breeding pairs on Mindanao ranging from 82 to 233, depending on how the forest cover is factored into the estimates. 相似文献
922.
Dean P. Hector 《Ethology : formerly Zeitschrift fur Tierpsychologie》1986,73(3):247-257
Aplomado falcons (Falco femoralis) often hunt in pairs when chasing birds; 29% of 349 hunts observed in eastern Mexico involved mated pairs of falcons simultaneously chasing the same prey animal; and 66% of 100 hunts of birds were tandem pursuits. Although true cooperative hunting is uncommon in birds of prey, hunts by pairs of Aplomado falcons consistently showed signs of cooperative behavior such as use of a simple coordinative signal, and some division of labor between participating individuals. Pairs were more than twice as successful as solo falcons hunting birds (44% vs. 19%), however, there was no evidence that cooperative hunting increased the range of feasible prey sizes. The frequent use of cooperative foraging in this and similar species may relate to necessities of efficient nest defense, and food and nest procurement in savannas inhabited by a diversity of nest-site predators. 相似文献
923.
DNA Isolation and Amplification from Cacti 总被引:2,自引:1,他引:1
de la Cruz Marlene Ramirez Fabiola Hernandez Hector 《Plant Molecular Biology Reporter》1997,15(4):319-325
The cacti family is a morphologically heterogeneous group comprising 100 genera and about 1500 species (Hernandez and Barcenas, 1996). With the exception of one genus, all members of this family are native to America (Hernandez and Barcenas, 1996). There are three subfamilies, Opuntioideae, Cactoideae, and Pereskioideae (Gibson and Nobel, 1986). DNA isolation from cacti is notoriously difficult because they contain high amounts of polysaccharides and secondary metabolites which form insoluble complexes with nucleic acids during extraction (Guillemaut and Marechal-Drouard, 1992). Like in other groups of plants, the secondary metabolites and polysaccharides in cacti inhibit enzyme action (Porebski et al., 1997). The polysaccharides are visually evident by their viscous, glue-like texture and they make the DNA unmanageable when pipeting and hard to amplify by the polymerase chain reaction (PCR) (Poresbski et al., 1997). We report an easy and inexpensive protocol to isolate DNA from cacti. We used this method to isolate DNA from 85 species (170 individuals) of 39 genera of the subfamilies Pereskioideae, Opuntioidea, and Cactoideae. This procedure is a modification of a protocol described by De la Cruz et al. (1995) for the Cacti family. It requires only a few grams of tissue and does not require destruction of the whole plant to produce high molecular weight genomic DNA. The DNA from this procedure can be amplified consistently by PCR and used for RAPD analysis. 相似文献
924.
T lymphocyte cloning from rejected human kidney allograft. Recognition repertoire of alloreactive T cell clones 总被引:3,自引:0,他引:3
M Bonneville J F Moreau E Blokland J Pool J P Moisan E Goulmy J P Soulillou 《Journal of immunology (Baltimore, Md. : 1950)》1988,141(12):4187-4195
We analyzed the recognition repertoire of 16 human alloreactive T cell clones (ATLC) derived from cells invading an irreversibly rejected kidney allograft. These clones, which specifically proliferated against the kidney donor B lymphoblastoid cell line, fell into two classes: CD4+ killers and CD8+ killers. Cytotoxic and proliferative activities of the ATLC were studied by using a panel of allogeneic cells sharing HLA specificities with kidney donor cells. Moreover, mAb recognizing monomorphic parts of HLA class I and class II molecules were used in blocking experiments of ATLC cytotoxicity. The results obtained from proliferative and cytotoxic assays were concordant. All ATLC investigated were directed against HLA molecules, and some clones were found to recognize HLA-B, -C, -DP, -DQ, or -DR products. All anti-HLA class I ATLC were CD8+, whereas both CD4+ and CD8+ ATLC were committed against HLA class II specificities. Nine of 16 ATLC were shown to react against serologically defined donor HLA determinants. These data indicate the recognition of HLA determinants in the course of an in vivo alloimmune response and particularly emphasize the role of HLA-C and DP loci products so far ignored in clinical transplantation. 相似文献
925.
P C Braun R F Hector M E Kamark J T Hart R L Cihlar 《Canadian journal of microbiology》1987,33(6):546-550
Experiments were conducted to gain insight concerning the mechanism(s) whereby cerulenin and sodium butyrate affect chitin synthesis in Candida albicans. In vitro studies with isolated membrane-bound chitin synthase from C. albicans, strain 4918, showed that neither agent affected the level of either unactivated or trypsin-activated enzyme activity. Subsequent studies utilizing protoplasts revealed that early in the cell wall regeneration process, cells treated with cerulenin or butyrate synthesized chitin at a rate equal to untreated controls, as measured by the incorporation of [3H]-N-acetylglucosamine (GlcNAc) into acid-alkali insoluble material. However, after 40 min of incubation, the incorporation of [3H]GlcNAc into chitin is reduced in cells treated with either agent. On the other hand, samples taken during the same time intervals and analyzed by flow cytometry suggested that the amount of chitin synthesis in treated and untreated cells was identical. A marked decrease in fluorescence was observed in similar experiments using polyoxin D, a direct inhibitor of chitin synthase activity. Experiments that measured uptake of [3H]GlcNAc into both whole cells and protoplasts demonstrated that cerulenin and butyrate had no effect on the transport of the chitin precursor. 相似文献
926.
Claudia E. Sotomayor Hector R. Rubinstein Laura Cervi Clelia M. Riera Dra. Diana T. Masih 《Mycopathologia》1989,108(1):5-10
The presence of the microorganism, cortical hyperplasia and germinal centers was detected in the thymus of rats infected with 107 viable Cryptococcus neoformans cells and immunized at 7 days afterwards with 2.5 mg (0.1 ml) of human serum albumin (HSA) incorporated to complete Freund's adjuvant (CFA) (Group 2). There was no modification of the glandular structure in the thymus of the animals only immunized with HSA-CFA (Group 1). The weight of the thymus of group 2, animals infected and immunized, was increased compared with the weight of the thymus of group 1 animals, this became evident by the increase of the thymic index (TI) (p <0.005). This rate was obtained calculating the thymus weight/total body weight ratio × 1000.Thymic cells (107 cells in 1 ml) obtained from both groups of animals were transferred to normal syngeneic rats of the same sex. The recipient rats were immunized with HSA-CFA 24 h later and 14 days after the transference, the response of delayed-type hypersensitivity (DTH) was studied in them. It could be observed that the thymic cells coming from group 2 animals were capable of suppressing significatively the afferent pathway of the DTH response to HSA when compared with the response of the animals that received cells coming from group 1 rats (p<0.0001). 相似文献
927.
928.
929.
Effect of maternal diet on offspring coping styles in rodents: a systematic review and meta‐analysis
下载免费PDF全文
![点击此处可从《Biological reviews of the Cambridge Philosophical Society》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Anne A. Besson Malgorzata Lagisz Alistair M. Senior Katie L. Hector Shinichi Nakagawa 《Biological reviews of the Cambridge Philosophical Society》2016,91(4):1065-1080
Maternal nutrition can have long‐term effects on offspring morphology, physiology and behaviours. However, it is unclear whether mothers ‘program’ offspring behavioural coping strategy (proactive/reactive) according to the predicted nutritional quality of their future environment. We conducted a systematic review on this topic and meta‐analytically synthesized relevant experimental data on mice and rats (46 studies). We included data from experiments where dams were subjected to caloric restriction, protein restriction or overfeeding around gestation and subsequently measured offspring activity, exploration, or anxiety. Overall, little evidence existed for effects of maternal nutrition on the three investigated behavioural traits. The high heterogeneity observed in the data set suggests that maternal programming may sometimes occur. However, because offspring had access to a balanced diet before testing, behaviours may have been reprogrammed. Our results may indicate that reprogrammed behaviours could ameliorate negative effects associated with sub‐optimal nutrition in early life. Further, our systematic review revealed clear knowledge gaps and fruitful future research avenues. 相似文献
930.
Fátima Duarte-Aké Eduardo Castillo-Castro Felipe Barredo Pool Francisco Espadas Jorge M. Santamaría Manuel L. Robert Clelia De-la-Peña 《Plant cell reports》2016,35(12):2489-2502