全文获取类型
收费全文 | 1145篇 |
免费 | 81篇 |
国内免费 | 23篇 |
专业分类
耳鼻咽喉 | 32篇 |
儿科学 | 39篇 |
妇产科学 | 16篇 |
基础医学 | 152篇 |
口腔科学 | 15篇 |
临床医学 | 183篇 |
内科学 | 234篇 |
皮肤病学 | 5篇 |
神经病学 | 71篇 |
特种医学 | 85篇 |
外科学 | 213篇 |
综合类 | 12篇 |
预防医学 | 56篇 |
眼科学 | 11篇 |
药学 | 83篇 |
中国医学 | 1篇 |
肿瘤学 | 41篇 |
出版年
2021年 | 11篇 |
2019年 | 10篇 |
2018年 | 16篇 |
2017年 | 19篇 |
2016年 | 10篇 |
2015年 | 24篇 |
2014年 | 31篇 |
2013年 | 24篇 |
2012年 | 37篇 |
2011年 | 33篇 |
2010年 | 28篇 |
2009年 | 34篇 |
2008年 | 64篇 |
2007年 | 72篇 |
2006年 | 47篇 |
2005年 | 47篇 |
2004年 | 37篇 |
2003年 | 36篇 |
2002年 | 48篇 |
2001年 | 52篇 |
2000年 | 43篇 |
1999年 | 31篇 |
1998年 | 18篇 |
1997年 | 13篇 |
1996年 | 17篇 |
1995年 | 21篇 |
1994年 | 19篇 |
1993年 | 13篇 |
1992年 | 25篇 |
1991年 | 28篇 |
1990年 | 29篇 |
1989年 | 29篇 |
1988年 | 29篇 |
1987年 | 27篇 |
1986年 | 27篇 |
1985年 | 27篇 |
1984年 | 12篇 |
1983年 | 9篇 |
1982年 | 15篇 |
1981年 | 15篇 |
1980年 | 12篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1976年 | 8篇 |
1975年 | 10篇 |
1974年 | 7篇 |
1970年 | 5篇 |
1969年 | 6篇 |
1967年 | 5篇 |
1966年 | 6篇 |
排序方式: 共有1249条查询结果,搜索用时 31 毫秒
41.
The role of condensed tannins in the nutritional value of Lotus pedunculatus for sheep. 2. Quantitative digestion of carbohydrates and proteins 总被引:1,自引:0,他引:1
Primary growth vegetative Lotus pedunculatus containing 46 and 106 g/kg dry matter (DM) of total condensed tannin and 3 and 14 g/kg DM of free condensed tannin, was cut and fed fresh at hourly intervals (750 g DM/d) to sheep fitted with permanent cannulas into the rumen and duodenum. Low- and high-tannin lotus contained respectively 41.3 and 31.6 g total nitrogen/kg DM and 132 and 152 g lignin/kg DM. The two forms of lotus were similar in carbohydrate composition. Nutrient intake was recorded and faecal output measured by direct collection. Digesta flow to the duodenum was estimated by measuring dilution at the duodenum of inert ruthenium phenanthroline (Ru-P) and chromium-EDTA markers continuously infused into the rumen. Effects attributable to condensed tannins were assessed by comparing the digestion of the two diets, and by comparing the digestion of each with predicted values for non-tannin-containing fresh forages fed at similar intakes. Apparent digestibility of all nutrients measured was less for high- than for low-tannin lotus (P less than 0.01). The levels of cellulose digested ruminally and post- ruminally in both forms of lotus were similar to predicted values. However, less hemicellulose and readily fermentable carbohydrate (RFC; soluble carbohydrate + pectin) was digested in the rumen in sheep given both forms of lotus than would be predicted for non-tannin-containing fresh forage diets, but this was compensated for by greater post-ruminal absorption of both nutrients. Total N gains across the rumen (duodenal N flow--total N intake) were 1.8 and 10.5 g/d for low- and high-tannin lotus v. predicted losses of 3.7 and 2.1 g/d for non-tannin-containing fresh forages given at the same total N intakes. Post-ruminal digestion of non- amonia -N (NAN; proportion NAN flowing at duodenum) was 0.71 and 0.67 for low- and high-tannin lotus respectively v. 0.76 for comparable non-tannin-containing fresh forages. Energy absorbed as amino acids from the small intestine was calculated to be 0.29 of metabolizable energy for both forms of lotus, compared with 0.17 and 0.21 for perennial ryegrass and white clover. It was concluded that the presence of condensed tannins in lotus markedly increased post-ruminal NAN absorption compared with non-tannin-containing fresh forage diets, but depressed ruminal digestion of RFC and hemicellulose. 相似文献
42.
The vertical wheeler is a new mobility aid that was specifically designed to help improve the quality of life for the handicapped child by providing mobility while standing. Results of a clinical trial in a population of patients with cerebral palsy are presented. Criteria were selected to allow evaluation of the rehabilitative effect of the device on the population. Results showed that the children in this cerebral palsy group all benefited from ambulation with the wheeler. Patients with spastic quadriparesis seemed to gain the most immediate benefit. The device contributed to improved mobility, posture, and self-image. The wheeler was safe and fun for the children. It has the potential for improving the psychologic and medical status of the child with severe locomotion impairment. 相似文献
43.
44.
45.
The incidence of hollow-organ injury has increased steadily since the use of seat-belts was introduced. It has become apparent that the clinical manifestations of intestinal injury may be delayed considerably. Delayed perforations can pose a diagnostic challenge to the attending surgeon. The authors report four patients who suffered delayed intestinal perforation 6 or more days after sustaining nonpenetrating abdominal trauma in motor vehicle accidents while wearing passive seat-belt restraints. All patients had low severity of injury (scores ranging from 4 to 13) but had persistent vague abdominal pain before perforation occurred. Three of the four patients suffered spinal trauma as their major initial injury. Such patients appear to be at higher risk for delayed perforation and should be monitored carefully. 相似文献
46.
47.
48.
BACKGROUND: Airbag deployment is an acknowledged mechanism of serious trauma in children involved in motor vehicle crashes. From a review of national databases, we determined the number and types of fatal and nonfatal injuries to children caused by airbag deployment and child restraint system use. We also reviewed the relevant literature and provide information useful for caregivers and health care professionals in hopes of reducing future injuries. METHODS: We retrospectively reviewed 263 reported cases in which airbag deployment caused fatal or nonfatal injuries in children from reports released by the National Highway and Transportation Safety Administration and the National Pediatric Trauma Registry. Data were collected from January 1993 to December 2002 and imported into a database program for analysis. RESULTS: Of the 263 pediatric injuries caused by airbag deployment, 159 were fatal, and 104 were nonfatal. The peak incidence occurred in 1998, when 58 children were reported injured. Head injuries were most frequent, involving 170 children (64.6%), followed by spinal injuries, involving 100 children (38.0%). For children in their first year of life, head injuries were the sole mechanism of fatality. Of all children studied, only six (2.3%) were properly restrained. CONCLUSION: Airbag deployment in motor vehicle crashes is a well-recognized mechanism of morbidity and mortality in the pediatric population. Most injuries include trauma to the head and spine, which can have significant long-term consequences. Although the reported incidence of such injuries is decreasing, many children are improperly restrained. In our study, only 2.3% of children were properly restrained, suggesting that proper child restraint and seating position could have prevented most injuries. 相似文献
49.
Various neuropeptides and neurotransmitters affect GH secretion by acting on GHRH and somatostatin (SRIF) cells. GH secretion is also affected by alteration in adiposity, which could be via modulation of GHRH and SRIF cells. We quantified colocalization of neuropeptides in GHRH and SRIF cells and afferent projections to these cells in lean (food restricted) and normally fed sheep (n=4/group). The number of GHRH-immunoreactive (IR) cells in the arcuate nucleus was higher in lean animals, but the number of SRIF-IR cells in the periventricular nucleus was similar in the two groups. A subpopulation of GHRH-IR cells colocalized neuropeptide Y in lean animals, but this was not seen in normally fed animals. GHRH/galanin (GAL) colocalization was higher in lean animals with no difference in numbers of GHRH/tyrosine hydroxylase or GHRH/GAL-like peptide cells. SRIF/enkephalin colocalization was lower in lean animals. The percentage of GHRH neurons receiving SRIF input was similar in lean and normally fed animals, but more GHRH cells received input from enkephalin afferents in normally fed animals. The percentage of SRIF cells receiving GHRH, neuropeptide Y, GAL, and orexin afferents was higher in lean animals. These findings provide an anatomical evidence of central mechanism(s) by which appetite-regulating peptides and dopamine could regulate GH secretion. Increased input to SRIF cells in lean animals may be inhibitory and permissive of increased GH. The appearance of NPY in GHRH cells of lean animals may be a mechanism for regulation of increasing GH secretion with reduced adiposity. 相似文献
50.
Binding of 125I-labelled bovine TSH to crude membrane fractions of human thyroid tissue was a saturable, hormonally specific process which yielded non-linear Scatchard plots with limiting affinities of approximately 10(9) and 10(7) l/mol. Binding activity in membranes was soluble in Triton X-100, was inhibited specifically by immunoglobulins from patients with Graves's disease, and was increased by the beta-blocking drug, propranolol. In contrast, purified nuclear preparations showed a predominance of lower affinity binding, and their binding activity was insoluble in Triton and insensitive to immunoglobulins from patients with Grave's disease and to propranolol. Tryptic digestion liberated only low affinity binding activity from membranes or nuclei. It was concluded that human thyroid tissue contains independent classes of TSH-binding sites, which differ in their chemical, immunological and hormone-binding properties. 相似文献