全文获取类型
收费全文 | 3692篇 |
免费 | 351篇 |
国内免费 | 8篇 |
专业分类
4051篇 |
出版年
2023年 | 29篇 |
2022年 | 62篇 |
2021年 | 91篇 |
2020年 | 44篇 |
2019年 | 55篇 |
2018年 | 72篇 |
2017年 | 60篇 |
2016年 | 93篇 |
2015年 | 188篇 |
2014年 | 184篇 |
2013年 | 255篇 |
2012年 | 310篇 |
2011年 | 288篇 |
2010年 | 171篇 |
2009年 | 147篇 |
2008年 | 220篇 |
2007年 | 190篇 |
2006年 | 197篇 |
2005年 | 153篇 |
2004年 | 143篇 |
2003年 | 121篇 |
2002年 | 113篇 |
2001年 | 94篇 |
2000年 | 86篇 |
1999年 | 66篇 |
1998年 | 24篇 |
1997年 | 28篇 |
1996年 | 31篇 |
1995年 | 38篇 |
1994年 | 23篇 |
1993年 | 14篇 |
1992年 | 36篇 |
1991年 | 21篇 |
1990年 | 38篇 |
1989年 | 37篇 |
1988年 | 29篇 |
1987年 | 21篇 |
1986年 | 22篇 |
1985年 | 33篇 |
1984年 | 16篇 |
1983年 | 19篇 |
1982年 | 13篇 |
1981年 | 13篇 |
1980年 | 18篇 |
1979年 | 24篇 |
1977年 | 10篇 |
1975年 | 16篇 |
1973年 | 10篇 |
1970年 | 11篇 |
1969年 | 13篇 |
排序方式: 共有4051条查询结果,搜索用时 15 毫秒
101.
102.
103.
Lee A. Rollins Angela T. Moles Serena Lam Robert Buitenwerf Joanna M. Buswell Claire R. Brandenburger Habacuc Flores‐Moreno Knud B. Nielsen Ellen Couchman Gordon S. Brown Fiona J. Thomson Frank Hemmings Richard Frankham William B. Sherwin 《Ecology and evolution》2013,3(13):4501-4517
Some introduced populations thrive and evolve despite the presumed loss of diversity at introduction. We aimed to quantify the amount of genetic diversity retained at introduction in species that have shown evidence of adaptation to their introduced environments. Samples were taken from native and introduced ranges of Arctotheca populifolia and Petrorhagia nanteuilii. Using microsatellite data, we identified the source for each introduction, estimated genetic diversity in native and introduced populations, and calculated the amount of diversity retained in introduced populations. These values were compared to those from a literature review of diversity in native, confamilial populations and to estimates of genetic diversity retained at introduction. Gene diversity in the native range of both species was significantly lower than for confamilials. We found that, on average, introduced populations showing evidence of adaptation to their new environments retained 81% of the genetic diversity from the native range. Introduced populations of P. nanteuilii had higher genetic diversity than found in the native source populations, whereas introduced populations of A. populifolia retained only 14% of its native diversity in one introduction and 1% in another. Our literature review has shown that most introductions demonstrating adaptive ability have lost diversity upon introduction. The two species studied here had exceptionally low native range genetic diversity. Further, the two introductions of A. populifolia represent the largest percentage loss of genetic diversity in a species showing evidence of substantial morphological change in the introduced range. While high genetic diversity may increase the likelihood of invasion success, the species examined here adapted to their new environments with very little neutral genetic diversity. This finding suggests that even introductions founded by small numbers of individuals have the potential to become invasive. 相似文献
104.
Yong-Ping?ZhengEmail author Timothy?Tin-Yan?Lee Kelly?Ka-Lee?Lai Benjamin?Hon-Kei?Yip Guang-Quan?Zhou Wei-Wei?Jiang James?Chung-Wai?Cheung Man-Sang?Wong Bobby?King-Wah?Ng Jack?Chun-Yiu?Cheng Tsz-Ping?Lam 《Scoliosis》2016,11(1):13
Background
Radiographic evaluation for patients with scoliosis using Cobb method is the current gold standard, but radiography has radiation hazards. Several groups have recently demonstrated the feasibility of using 3D ultrasound for the evaluation of scoliosis. Ultrasound imaging is radiation-free, comparatively more accessible, and inexpensive. However, a reliable and valid 3D ultrasound system ready for clinical scoliosis assessment has not yet been reported. Scolioscan is a newly developed system targeted for scoliosis assessment in clinics by using coronal images of spine generated by a 3D ultrasound volume projection imaging method. The aim of this study is to test the reliability of spine deformity measurement of Scolioscan and its validity compared to the gold standard Cobb angle measurements from radiography in adolescent idiopathic scoliosis (AIS) patients.Methods
Prospective study divided into two stages: 1) Investigation of intra- and inter- reliability between two operators for acquiring images using Scolioscan and among three raters for measuring spinal curves from those images; 2) Correlation between the Cobb angle obtained from radiography by a medical doctor and the spine curve angle obtained using Scolioscan (Scolioscan angle). The raters for ultrasound images and the doctors for evaluating radiographic images were mutually blinded. The two stages of tests involved 20 (80 % females, total of 26 angles, age of 16.4?±?2.7 years, and Cobb angle of 27.6?±?11.8°) and 49 (69 % female, 73 angles, 15.8?±?2.7 years and 24.8?±?9.7°) AIS patients, respectively. Intra-class correlation coefficients (ICC) and Bland-Altman plots and root-mean-square differences (RMS) were employed to determine correlations, which interpreted based on defined criteria.Results
We demonstrated a very good intra-rater and intra-operator reliability for Scolioscan angle measurement with ICC larger than 0.94 and 0.88, respectively. Very good inter-rater and inter-operator reliability was also demonstrated, with both ICC larger than 0.87. For the thoracic deformity measurement, the RMS were 2.5 and 3.3° in the intra- and inter-operator tests, and 1.5 and 3.6° in the intra- and inter-rater tests, respectively. The RMS differences were 3.1, 3.1, 1.6, 3.7° in the intra- and inter-operator and intra- and inter-rater tests, respectively, for the lumbar angle measurement. Moderate to strong correlations (R2?>?0.72) were observed between the Scolioscan angles and Cobb angles for both the thoracic and lumbar regions. It was noted that the Scolioscan angle slightly underestimated the spinal deformity in comparison with Cobb angle, and an overall regression equation y?=?1.1797x (R2?=?0.76) could be used to translate the Scolioscan angle (x) to Cobb angle (y) for this group of patients. The RMS difference between Scolioscan angle and Cobb angle was 4.7 and 6.2°, with and without the correlation using the overall regression equation.Conclusions
We showed that Scolioscan is reliable for measuring coronal deformity for patients with AIS and appears promising in screening large numbers of patients, for progress monitoring, and evaluation of treatment outcomes. Due to it being radiation-free and relatively low-cost, Scolioscan has potential to be widely implemented and may contribute to reducing radiation dose during serial monitoring.105.
106.
Agnes Y. Lai Moses W. Mui Alice Wan Sunita M. Stewart Carol Yew Tai-hing Lam Sophia S. Chan 《PloS one》2016,11(1)
Evidence-based practice and capacity-building approaches are essential for large-scale health promotion interventions. However, there are few models in the literature to guide and evaluate training of social service workers in community settings. This paper presents the development and evaluation of the “train-the-trainer” workshop (TTT) for the first large scale, community-based, family intervention projects, entitled “Happy Family Kitchen Project” (HFK) under the FAMILY project, a Hong Kong Jockey Club Initiative for a Harmonious Society. The workshop aimed to enhance social workers’ competence and performance in applying positive psychology constructs in their family interventions under HFK to improve family well-being of the community they served. The two-day TTT was developed and implemented by a multidisciplinary team in partnership with community agencies to 50 social workers (64% women). It focused on the enhancement of knowledge, attitude, and practice of five specific positive psychology themes, which were the basis for the subsequent development of the 23 family interventions for 1419 participants. Acceptability and applicability were enhanced by completing a needs assessment prior to the training. The TTT was evaluated by trainees’ reactions to the training content and design, changes in learners (trainees) and benefits to the service organizations. Focus group interviews to evaluate the workshop at three months after the training, and questionnaire survey at pre-training, immediately after, six months, one year and two years after training were conducted. There were statistically significant increases with large to moderate effect size in perceived knowledge, self-efficacy and practice after training, which sustained to 2-year follow-up. Furthermore, there were statistically significant improvements in family communication and well-being of the participants in the HFK interventions they implemented after training. This paper offers a practical example of development, implementation and model-based evaluation of training programs, which may be helpful to others seeking to develop such programs in diverse communities. 相似文献
107.
A high‐throughput capillary isoelectric focusing immunoassay for fingerprinting protein sialylation 下载免费PDF全文
Lam Raga Anggara Markely Lila Cheung Young Jun Choi Thomas Ryll Scott Estes Shashi Prajapati Iva Turyan Ruth Frenkel Zoran Sosic James Lambropoulos Lia Tescione Thomas Ryll Melissa Berman 《Biotechnology progress》2016,32(1):235-241
The serum half‐life, biological activity, and solubility of many recombinant glycoproteins depend on their sialylation. Monitoring glycoprotein sialylation during cell culture manufacturing is, therefore, critical to ensure product efficacy and safety. Here a high‐throughput method for semi‐quantitative fingerprinting of glycoprotein sialylation using capillary isoelectric focusing immunoassay on NanoPro (Protein Simple) platform was developed. The method was specific, sensitive, precise, and robust. It could analyze 2 μL of crude cell culture samples without protein purification, and could automatically analyze from 8 samples in 4 h to 96 samples in 14 h without analyst supervision. Furthermore, its capability to detect various changes in sialylation fingerprints during cell culture manufacturing process was indispensable to ensure process robustness and consistency. Moreover, the changes in the sialylation fingerprints analyzed by this method showed strong correlations with intact mass analysis using liquid chromatography and mass spectrometry. © 2015 American Institute of Chemical Engineers Biotechnol. Prog., 32:235–241, 2016 相似文献
108.
109.
Joanna Maria Radziwill-Bienkowska Doan Thanh Lam Le Pawel Szczesny Marie-Pierre Duviau Tamara Aleksandrzak-Piekarczyk Pascal Loubière Muriel Mercier-Bonin Jacek Karol Bardowski Magdalena Kowalczyk 《Applied microbiology and biotechnology》2016,100(22):9605-9617
Understanding the nature of mucus-microbe interactions will provide important information that can help to elucidate the mechanisms underlying probiotic adhesion. This study focused on the adhesive properties of the Lactococcus lactis subsp. cremoris IBB477 strain, previously shown to persist in the gastrointestinal tract of germ-free rats. The shear flow-induced detachment of L. lactis cells was investigated under laminar flow conditions. Such a dynamic approach demonstrated increased adhesion to bare and mucin-coated polystyrene for IBB477, compared to that observed for the MG1820 control strain. To identify potential genetic determinants giving adhesive properties to IBB477, the improved high-quality draft genome sequence comprising chromosome and five plasmids was obtained and analysed. The number of putative adhesion proteins was determined on the basis of surface/extracellular localisation and/or the presence of adhesion domains. To identify proteins essential for the IBB477 specific adhesion property, nine deletion mutants in chromosomal genes have been constructed and analysed using adhesion tests on bare polystyrene as well as mucin-, fibronectin- or collagen IV-coated polystyrene plates in comparison to the wild-type strain. These experiments demonstrated that gene AJ89_07570 encoding a protein containing DUF285, MucBP and four Big_3 domains is involved in adhesion to bare and mucin-coated polystyrene. To summarise, in the present work, we characterised the adhesion of IBB477 under laminar flow conditions; identified the putative adherence factors present in IBB477, which is the first L. lactis strain exhibiting adhesive and mucoadhesive properties to be sequenced and demonstrated that one of the proteins containing adhesion domains contributes to adhesion. 相似文献
110.