全文获取类型
收费全文 | 2793篇 |
免费 | 344篇 |
国内免费 | 2篇 |
专业分类
3139篇 |
出版年
2022年 | 21篇 |
2021年 | 45篇 |
2019年 | 29篇 |
2018年 | 28篇 |
2017年 | 36篇 |
2016年 | 54篇 |
2015年 | 91篇 |
2014年 | 103篇 |
2013年 | 125篇 |
2012年 | 134篇 |
2011年 | 142篇 |
2010年 | 87篇 |
2009年 | 79篇 |
2008年 | 104篇 |
2007年 | 115篇 |
2006年 | 91篇 |
2005年 | 90篇 |
2004年 | 99篇 |
2003年 | 109篇 |
2002年 | 104篇 |
2001年 | 84篇 |
2000年 | 95篇 |
1999年 | 68篇 |
1998年 | 44篇 |
1997年 | 55篇 |
1996年 | 44篇 |
1995年 | 35篇 |
1994年 | 26篇 |
1993年 | 43篇 |
1992年 | 56篇 |
1991年 | 48篇 |
1990年 | 49篇 |
1989年 | 56篇 |
1988年 | 33篇 |
1987年 | 26篇 |
1986年 | 39篇 |
1985年 | 38篇 |
1984年 | 53篇 |
1983年 | 29篇 |
1982年 | 36篇 |
1981年 | 29篇 |
1980年 | 35篇 |
1979年 | 28篇 |
1977年 | 36篇 |
1976年 | 23篇 |
1975年 | 21篇 |
1974年 | 25篇 |
1973年 | 26篇 |
1972年 | 26篇 |
1970年 | 31篇 |
排序方式: 共有3139条查询结果,搜索用时 31 毫秒
41.
Andrew M. Griffiths David W. Sims Andrew Johnson Arve Lynghammar Matthew McHugh Torkild Bakken Martin J. Genner 《Conservation Genetics》2011,12(2):577-582
Sequencing of a partial region of the mitochondrial control region has revealed no shared haplotypes between longnose skate (Dipturus oxyrinchus L.) sampled in the north-eastern Atlantic (Norway and Rockall) and those sampled in the Mediterranean (Mallorca). Bayesian estimation of the migration rate suggests little, if any, gene flow occurs between the regions and that the populations separated 20,000?years ago. These conclusions provide a genetic basis for long-standing observations, based on egg capsule and adult size, that longnose skate in the Mediterranean may be genetically isolated from other stocks. This result has important conservation implications for the threatened longnose skate. 相似文献
42.
WHO Collaborating Centres (CCs) form part of an international collaborative network set up by WHO in support of its mandated programme at the country, intercountry, regional, interregional and global levels, as appropriate. As part of its mandate in the area of biologicals, WHO has broadened the scope of its work and has expanded the range of activities devoted to the establishment of international standards for vaccines. In line with global immunization goals, the need for standards for evaluation of quality, safety and efficacy of new vaccines, as well as those that have been in use for a long time, has significantly increased. Furthermore, complex issues related to new production methodologies, more sophisticated techniques for characterization and laboratory testing, and for nonclinical and clinical evaluation of vaccines have raised a number of regulatory challenges for WHO when requested to assist its Member States. In this context, CCs in the area of standardization of vaccines and biotherapeutics (excluding blood products) have provided technical assistance and have broadened the scope of their work over time. In the area of standardization and regulatory evaluation of vaccines, WHO currently has six CCs as well as one candidate centre for which the designation process has been initiated and a further three candidate centres with great potential. The purpose of the meeting held on 24–26 April 2012 was to improve understanding of WHO's priorities in setting standards, to facilitate their implementation, and to increase transparency of the roles and responsibilities of CCs. The meeting was also an excellent opportunity to explore possibilities for improving collaboration between WHO and CCs, as well as among CCs themselves by working as a CC network. All CCs expressed a wish for increased interaction, information-sharing, collaboration and other ways of working together that may lead to cross-fertilization between the CCs. Synergy was recognized as a significant mechanism for leveraging existing resources in responding to global public health challenges and in addressing WHO's priorities. Agreement was reached for operating as a network of CCs. 相似文献
43.
International workshop on opportunities for ecosystem approaches to fisheries management in the Pacific Ocean tuna fisheries 总被引:1,自引:0,他引:1
44.
Manon Grube Sukhbinder Kumar Freya E. Cooper Stuart Turton Timothy D. Griffiths 《Proceedings. Biological sciences / The Royal Society》2012,279(1746):4496-4504
This work tests the relationship between auditory and phonological skill in a non-selected cohort of 238 school students (age 11) with the specific hypothesis that sound-sequence analysis would be more relevant to phonological skill than the analysis of basic, single sounds. Auditory processing was assessed across the domains of pitch, time and timbre; a combination of six standard tests of literacy and language ability was used to assess phonological skill. A significant correlation between general auditory and phonological skill was demonstrated, plus a significant, specific correlation between measures of phonological skill and the auditory analysis of short sequences in pitch and time. The data support a limited but significant link between auditory and phonological ability with a specific role for sound-sequence analysis, and provide a possible new focus for auditory training strategies to aid language development in early adolescence. 相似文献
45.
N. Black J. Griffiths C. Pope A. Bowling P. Abel 《BMJ (Clinical research ed.)》1997,315(7121):1493-1498
OBJECTIVES: To describe the impact of surgery for stress incontinence on the severity of symptoms, other mental and physical symptoms, and overall health. To describe the incidence of postoperative complications. DESIGN: Prospective cohort study; questionnaires completed by patients before and 3, 6, and 12 months after surgery. Questionnaires completed by surgeons both before and after surgery. SETTING: 18 hospitals in the North Thames region. SUBJECTS: 442 women treated surgically for stress incontinence between January 1993 and June 1994. 367 women returned the 3 month questionnaire; 364 returned the 6 month questionnaire; and 359 returned the 12 month questionnaire. 49 surgeons provided perioperative information on 285 of the 442 women and postoperative information on 278. MAIN OUTCOME MEASURES: Stress incontinence symptom severity index, other urinary symptoms, bowel function, mental health, complications, global measures. RESULTS: Most women (288; 87%) reported an improvement in the severity of their stress incontinence, though only 92 (28%) were cured (continent). These improvements persisted for at least 12 months. The likelihood of improvement was similar regardless of whether urodynamic pressure studies had been conducted before surgery. Following surgery, women were less likely to suffer from urinary frequency, nocturia, postvoid fullness, dysuria, and urgency. While mental health improved for 194 (71%), a quarter of women reported deterioration. Only 37 (10%) were satisfied with postoperative pain control. A third experienced one or more complications while in hospital, most commonly difficulty urinating. This problem affected 1 in 11 women after discharge. A year after surgery two thirds of women reported feeling better (251; 72%), that the outcome met or exceeded their expectations (230; 66%), and that they would recommend the operation to a friend in a similar situation (239; 68%), and that they would recommend the operation to a friend in a similar situation (239; 68%). Surgeons tended to be more optimistic about the effects of surgery; they were satisfied with the outcome in 176 (85%) cases and would again treat 245 (94%) of the women as they had done previously. CONCLUSIONS: Although surgery reduces the severity of stress incontinence it is not as effective as current textbooks suggest. Women considering surgery should be provided with more accurate information on the likelihood of an improvement in symptoms and the occurrence of complications, including postoperative pain. Urgency and urge incontinence should not be considered contraindications to surgery. The need for urodynamic assessment before surgery should be reappraised. 相似文献
46.
Kathleen M. Griffiths Andrew J. Mackinnon Dimity A. Crisp Helen Christensen Kylie Bennett Louise Farrer 《PloS one》2012,7(12)
Background
Internet support groups (ISGs) are popular, particularly among people with depression, but there is little high quality evidence concerning their effectiveness.Aim
The study aimed to evaluate the efficacy of an ISG for reducing depressive symptoms among community members when used alone and in combination with an automated Internet-based psychotherapy training program.Method
Volunteers with elevated psychological distress were identified using a community-based screening postal survey. Participants were randomised to one of four 12-week conditions: depression Internet Support Group (ISG), automated depression Internet Training Program (ITP), combination of the two (ITP+ISG), or a control website with delayed access to e-couch at 6 months. Assessments were conducted at baseline, post-intervention, 6 and 12 months.Results
There was no change in depressive symptoms relative to control after 3 months of exposure to the ISG. However, both the ISG alone and the combined ISG+ITP group showed significantly greater reduction in depressive symptoms at 6 and 12 months follow-up than the control group. The ITP program was effective relative to control at post-intervention but not at 6 months.Conclusions
ISGs for depression are promising and warrant further empirical investigation.Trial Registration
Controlled-Trials.com ISRCTN65657330 相似文献47.
48.
Griffiths GM 《Trends in cell biology》1996,6(9):329-332
The secretory granules o f cells derived from the haemopoietic lineage are 'secretory lysosomes' containing both lysosomal hydrolases and secretory proteins. Studies on cytotoxic T lymphocytes (CTLs) have elucidated several of the mechanisms that regulate protein sorting to, and secretion from, this unusual secretory organelle. In particular, recent findings from a CTL mutant have led to the hypothesis that CTLs, and other cells of the haemopoietic lineage, use specialized sorting and secretory mechanisms in which the lysosome functions as a regulated secretory granule. 相似文献
49.
Studies on flavonoid metabolism. Identification of the metabolites of (+)-catechin in rat urine 总被引:1,自引:2,他引:1 下载免费PDF全文
L. A. Griffiths 《The Biochemical journal》1964,92(1):173-179
50.