全文获取类型
收费全文 | 706篇 |
免费 | 65篇 |
专业分类
771篇 |
出版年
2023年 | 4篇 |
2022年 | 8篇 |
2021年 | 13篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 14篇 |
2017年 | 5篇 |
2016年 | 17篇 |
2015年 | 27篇 |
2014年 | 28篇 |
2013年 | 42篇 |
2012年 | 52篇 |
2011年 | 44篇 |
2010年 | 44篇 |
2009年 | 29篇 |
2008年 | 34篇 |
2007年 | 41篇 |
2006年 | 36篇 |
2005年 | 34篇 |
2004年 | 34篇 |
2003年 | 29篇 |
2002年 | 31篇 |
2001年 | 12篇 |
2000年 | 14篇 |
1999年 | 14篇 |
1998年 | 10篇 |
1997年 | 9篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 9篇 |
1991年 | 7篇 |
1990年 | 9篇 |
1989年 | 16篇 |
1988年 | 12篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 8篇 |
1980年 | 7篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1970年 | 2篇 |
排序方式: 共有771条查询结果,搜索用时 0 毫秒
101.
The idiosyncratic behaviours of seed dispersers are important contributors to plant spatial associations and genetic structures. In this study, we used a combination of field, molecular and spatial studies to examine the connections between seed dispersal and the spatial and genetic structures of a dominant neotropical palm Attalea phalerata. Field observation and genetic parentage analysis both indicated that the majority of A. phalerata seeds were dispersed locally over short distances (<30 m from the maternal tree). Spatial and genetic structures between adults and seedlings were consistent with localized and short-distance seed dispersal. Dispersal contributed to spatial associations among maternal sibling seedlings and strong spatial and genetic structures in both seedlings dispersed near (<10 m) and away (>10 m) from maternal palms. Seedlings were also spatially aggregated with juveniles. These patterns are probably associated with the dispersal of seeds by rodents and the survival of recruits at specific microsites or neighbourhoods over successive fruiting periods. Our cross-cohort analyses found palms in older cohorts and cohort pairs were associated with a lower proportion of offspring and sibling neighbours and exhibited weaker spatial and genetic structures. Such patterns are consistent with increased distance- and density-dependent mortality over time among palms dispersed near maternal palms or siblings. The integrative approaches used for this study allowed us to infer the importance of seed dispersal activities in maintaining the aggregated distribution and significant genetic structures among A. phalerata palms. We further conclude that distance- and density-dependent mortality is a key postdispersal process regulating this palm population. 相似文献
102.
103.
104.
Extracellular matrix proteins protect small cell lung cancer cells against apoptosis: a mechanism for small cell lung cancer growth and drug resistance in vivo. 总被引:29,自引:0,他引:29
T Sethi R C Rintoul S M Moore A C MacKinnon D Salter C Choo E R Chilvers I Dransfield S C Donnelly R Strieter C Haslett 《Nature medicine》1999,5(6):662-668
Resistance to chemotherapy is a principal problem in the treatment of small cell lung cancer (SCLC). We show here that SCLC is surrounded by an extensive stroma of extracellular matrix (ECM) at both primary and metastatic sites. Adhesion of SCLC cells to ECM enhances tumorigenicity and confers resistance to chemotherapeutic agents as a result of beta1 integrin-stimulated tyrosine kinase activation suppressing chemotherapy-induced apoptosis. SCLC may create a specialized microenvironment, and the survival of cells bound to ECM could explain the partial responses and local recurrence of SCLC often seen clinically after chemotherapy. Strategies based on blocking beta1 integrin-mediated survival signals may represent a new therapeutic approach to improve the response to chemotherapy in SCLC. 相似文献
105.
S.M.M. Karim S.S. Ratnam A.L. Kim K.C. Yeo H.T. Choo 《Prostaglandins & other lipid mediators》1982,23(2):257-263
16 phenoxy-ω-17,18,19,20 tetranor PGE2 methylsulfonylamide (Sulprostone) was used for termination of second trimester pregnancy in four groups of 30 patients. The drug was administered in intramuscular doses of either 0.5 mg four hourly or 1.0 mg 8 hourly. In two groups of 30 patients a medium size sterile laminaria was inserted into the cervical canal eight hours before the start of prostaglandin treatment. In the group treated with 1.0 mg sulprostone eight hourly, 96.7% of those with laminaria and 86.7% without laminaria aborted in respective mean times of 11.2 hrs and 17.5 hrs. All 30 patients (100%) in the laminaria group treated with 0.5 mg sulprostone four hourly aborted within 30 hours in a mean time of 10.4 hours compared with 26 patients (86.7%) in a mean time of 16.7 hours in the group without laminaria.One patient receiving 0.5 mg sulprostone four hourly (no laminaria) sustained a cervical tear requiring repair. The incidence of nausea, vomiting, diarrhoea, cold and shivering was low and similar in the four groups. 相似文献
106.
Moderate Weight Loss Improves Body Composition and Metabolic Function in Metabolically Unhealthy Lean Subjects 下载免费PDF全文
107.
K.H. Andy Choo 《American journal of human genetics》1997,61(6):1225-1233
108.
109.
110.
Exfoliative cytology in the evaluation of interferon treatment of cervical intraepithelial neoplasia
Local interferon injection in four patients with cervical intraepithelial neoplasia (CIN) regularly elicited progressive regression of the lesions. The response was observed with exfoliative cytology after each injection, guided by colposcopic examination. The cytologic changes showed a cytocidal effect mainly on the dyskaryotic cells, preceded by cellular degeneration not unlike that of nonspecific inflammation and accompanied by an increase in neutrophil infiltration. The cytologic response was closely correlated with partial or complete clinical regression based on the absence of viable or degenerated dyskaryotic cells in the cervical smears. Three patients showed complete clinical regression after treatment. One patient showed recurrent viable dyskaryotic cells when the dosage was reduced, and treatment was suspended temporarily although her lesion had regressed completely after five injections. Clinical recurrence was noted one week after viable dyskaryotic cells reappeared in her smears. These observations suggest that cytology may be a useful means of monitoring interferon treatment in CIN. 相似文献