全文获取类型
收费全文 | 1012篇 |
免费 | 92篇 |
出版年
2021年 | 11篇 |
2017年 | 11篇 |
2016年 | 15篇 |
2015年 | 35篇 |
2014年 | 40篇 |
2013年 | 47篇 |
2012年 | 58篇 |
2011年 | 65篇 |
2010年 | 36篇 |
2009年 | 25篇 |
2008年 | 44篇 |
2007年 | 52篇 |
2006年 | 45篇 |
2005年 | 44篇 |
2004年 | 50篇 |
2003年 | 45篇 |
2002年 | 43篇 |
2001年 | 9篇 |
2000年 | 6篇 |
1999年 | 12篇 |
1998年 | 18篇 |
1997年 | 9篇 |
1996年 | 13篇 |
1995年 | 7篇 |
1994年 | 13篇 |
1993年 | 16篇 |
1991年 | 10篇 |
1990年 | 14篇 |
1989年 | 16篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 9篇 |
1984年 | 12篇 |
1983年 | 8篇 |
1981年 | 10篇 |
1980年 | 18篇 |
1978年 | 10篇 |
1977年 | 14篇 |
1976年 | 9篇 |
1975年 | 12篇 |
1973年 | 18篇 |
1972年 | 9篇 |
1971年 | 8篇 |
1969年 | 12篇 |
1968年 | 10篇 |
1967年 | 7篇 |
1965年 | 7篇 |
1964年 | 9篇 |
1961年 | 5篇 |
排序方式: 共有1104条查询结果,搜索用时 15 毫秒
91.
92.
Aicardi syndrome is a genetic disorder characterized by the triad of infantile spasm in flexion, callosal agenesis and ocular abnormalities (chorioretinal lacunae, coloboma of optic disc). We report a typical case of Aicardi syndrome with all the classical features. 相似文献
93.
Modern solid-state NMR techniques, combined with X-ray diffraction, revealed the molecular origin of the difference in mechanical properties of self-associated chitosan films. Films cast from acidic aqueous solutions were compared before and after neutralization, and the role of the counterion (acetate vs Cl(-)) was investigated. There is a competition between local structure and long-range order. Hydrogen bonding gives good mechanical strength to neutralized films, which lack long-range organization. The long-range structure is better defined in films cast from acidic solutions in which strong electrostatic interactions cause rotational distortion around the chitosan chains. Plasticization by acetate counterions enhances long-range molecular organization and film flexibility. In contrast, Cl(-) counterions act as a defect and impair the long-range organization by immobilizing hydration water. Molecular motion and proton exchange are restricted, resulting in brittle films despite the high moisture content. 相似文献
94.
Tchemtchoua VT Atanasova G Aqil A Filée P Garbacki N Vanhooteghem O Deroanne C Noël A Jérome C Nusgens B Poumay Y Colige A 《Biomacromolecules》2011,12(9):3194-3204
The final goal of the present study was the development of a 3-D chitosan dressing that would shorten the healing time of skin wounds by stimulating migration, invasion, and proliferation of the relevant cutaneous resident cells. Three-dimensional chitosan nanofibrillar scaffolds produced by electrospinning were compared with evaporated films and freeze-dried sponges for their biological properties. The nanofibrillar structure strongly improved cell adhesion and proliferation in vitro. When implanted in mice, the nanofibrillar scaffold was colonized by mesenchymal cells and blood vessels. Accumulation of collagen fibrils was also observed. In contrast, sponges induced a foreign body granuloma. When used as a dressing covering full-thickness skin wounds in mice, chitosan nanofibrils induced a faster regeneration of both the epidermis and dermis compartments. Altogether our data illustrate the critical importance of the nanofibrillar structure of chitosan devices for their full biocompatibility and demonstrate the significant beneficial effect of chitosan as a wound-healing biomaterial. 相似文献
95.
Martin DP Lefeuvre P Varsani A Hoareau M Semegni JY Dijoux B Vincent C Reynaud B Lett JM 《PLoS pathogens》2011,7(9):e1002203
Genetic recombination is an important process during the evolution of many virus species and occurs particularly frequently amongst begomoviruses in the single stranded DNA virus family, Geminiviridae. As in many other recombining viruses it is apparent that non-random recombination breakpoint distributions observable within begomovirus genomes sampled from nature are the product of variations both in basal recombination rates across genomes and in the over-all viability of different recombinant genomes. Whereas factors influencing basal recombination rates might include local degrees of sequence similarity between recombining genomes, nucleic acid secondary structures and genomic sensitivity to nuclease attack or breakage, the viability of recombinant genomes could be influenced by the degree to which their co-evolved protein-protein and protein-nucleotide and nucleotide-nucleotide interactions are disreputable by recombination. Here we investigate patterns of recombination that occur over 120 day long experimental infections of tomato plants with the begomoviruses Tomato yellow leaf curl virus and Tomato leaf curl Comoros virus. We show that patterns of sequence exchange between these viruses can be extraordinarily complex and present clear evidence that factors such as local degrees of sequence similarity but not genomic secondary structure strongly influence where recombination breakpoints occur. It is also apparent from our experiment that over-all patterns of recombination are strongly influenced by selection against individual recombinants displaying disrupted intra-genomic interactions such as those required for proper protein and nucleic acid folding. Crucially, we find that selection favoring the preservation of co-evolved longer-range protein-protein and protein DNA interactions is so strong that its imprint can even be used to identify the exact sequence tracts involved in these interactions. 相似文献
96.
97.
Achan J Tibenderana J Kyabayinze D Mawejje H Mugizi R Mpeka B Talisuna A D'Alessandro U 《PloS one》2011,6(3):e17053
Introduction
Severe malaria is a life-threatening medical emergency and requires prompt and effective treatment to prevent death. There is paucity of published information on current practices of severe malaria case management in sub-Saharan Africa; we evaluated the management practices for severe malaria in Ugandan health facilitiesMethods and Findings
We did a cross sectional survey, using multi-stage sampling methods, of health facilities in 11 districts in the eastern and mid-western parts of Uganda. The study instruments were adapted from the WHO hospital care assessment tools. Between June and August 2009, 105 health facilities were surveyed and 181 health workers and 868 patients/caretakers interviewed. None of the inpatient facilities had all seven components of a basic care package for the management of severe malaria consistently available during the 3 months prior to the survey. Referral practices were appropriate for <10% (18/196) of the patients. Prompt care at any health facility was reported by 29% (247/868) of patients. Severe malaria was correctly diagnosed in 27% of patients (233).Though the quinine dose and regimen was correct in the majority (611/868, 70.4%) of patients, it was administered in the correct volumes of 5% dextrose in only 18% (147/815). Most patients (80.1%) had several doses of quinine administered in one single 500 ml bottle of 5% dextrose. Medications were purchased by 385 (44%) patients and medical supplies by 478 patients (70.6%).Conclusions
Management of severe malaria in Ugandan health facilities was sub-optimal. These findings highlight the challenges of correctly managing severe malaria in resource limited settings. Priority areas for improvement include triage and emergency care, referral practises, quality of diagnosis and treatment, availability of medicines and supplies, training and support supervision. 相似文献98.
Bartfield JK Stevens VJ Jerome GJ Batch BC Kennedy BM Vollmer WM Harsha D Appel LJ Desmond R Ard JD 《Obesity (Silver Spring, Md.)》2011,19(8):1609-1615
Little is known about the transition in behaviors from short-term weight loss to maintenance of weight loss. We wanted to determine how short-term and long-term weight loss and patterns of weight change were associated with intervention behavioral targets. This analysis includes overweight/obese participants in active treatment (n = 507) from the previously published PREMIER trial, an 18-month, multicomponent lifestyle intervention for blood pressure reduction, including 33 intervention sessions and recommendations to self-monitor food intake and physical activity daily. Associations between behaviors (attendance, recorded days/week of physical activity, food records/week) and weight loss of ≥5% at 6 and 18 months were examined using logistic regression. We characterized the sample using 5 weight change categories (weight gained, weight stable, weight loss then relapse, late weight loss, and weight loss then maintenance) and analyzed adherence to the behaviors for each category, comparing means with ANOVA. Participants lost an average of 5.3 ± 5.6 kg at 6 months and 4.0 ± 6.7 kg (4.96% of body weight) by 18 months. Higher levels of attendance, food record completion, and recorded days/week of physical activity were associated with increasing odds of achieving 5% weight loss. All weight change groups had declines in the behaviors over time; however, compared to the other four groups, the weight loss/maintenance group (n = 154) had statistically less significant decline in number of food records/week (48%), recorded days/week of physical activity (41.7%), and intervention sessions attended (12.8%) through 18 months. Behaviors associated with short-term weight loss continue to be associated with long-term weight loss, albeit at lower frequencies. Minimizing the decline in these behaviors may be important in achieving long-term weight loss. 相似文献
99.
100.
Insulin resistance in non-obese subjects is associated with activation of the JNK pathway and impaired insulin signaling in skeletal muscle 总被引:1,自引:0,他引:1
Masharani UB Maddux BA Li X Sakkas GK Mulligan K Schambelan M Goldfine ID Youngren JF 《PloS one》2011,6(5):e19878