全文获取类型
收费全文 | 11925篇 |
免费 | 562篇 |
国内免费 | 50篇 |
专业分类
耳鼻咽喉 | 255篇 |
儿科学 | 839篇 |
妇产科学 | 493篇 |
基础医学 | 1249篇 |
口腔科学 | 293篇 |
临床医学 | 1027篇 |
内科学 | 2381篇 |
皮肤病学 | 459篇 |
神经病学 | 810篇 |
特种医学 | 309篇 |
外科学 | 1682篇 |
综合类 | 486篇 |
一般理论 | 5篇 |
预防医学 | 1013篇 |
眼科学 | 210篇 |
药学 | 622篇 |
1篇 | |
中国医学 | 27篇 |
肿瘤学 | 376篇 |
出版年
2021年 | 100篇 |
2020年 | 76篇 |
2019年 | 84篇 |
2018年 | 94篇 |
2017年 | 90篇 |
2016年 | 95篇 |
2015年 | 135篇 |
2014年 | 174篇 |
2013年 | 252篇 |
2012年 | 317篇 |
2011年 | 342篇 |
2010年 | 223篇 |
2009年 | 259篇 |
2008年 | 280篇 |
2007年 | 262篇 |
2006年 | 299篇 |
2005年 | 232篇 |
2004年 | 185篇 |
2003年 | 197篇 |
2002年 | 163篇 |
2001年 | 174篇 |
2000年 | 139篇 |
1999年 | 185篇 |
1998年 | 203篇 |
1997年 | 220篇 |
1996年 | 238篇 |
1995年 | 201篇 |
1994年 | 189篇 |
1993年 | 181篇 |
1992年 | 173篇 |
1991年 | 173篇 |
1990年 | 148篇 |
1989年 | 169篇 |
1988年 | 135篇 |
1987年 | 144篇 |
1986年 | 125篇 |
1985年 | 105篇 |
1984年 | 94篇 |
1983年 | 72篇 |
1982年 | 73篇 |
1981年 | 77篇 |
1977年 | 69篇 |
1959年 | 343篇 |
1958年 | 759篇 |
1957年 | 868篇 |
1956年 | 771篇 |
1955年 | 803篇 |
1954年 | 780篇 |
1949年 | 182篇 |
1948年 | 125篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Previous studies have shown that cholinergic grafts derived from the medial septal nucleus are capable of restoring behavioral function in rats with lesions that sever the cholinergic inputs to the hippocampal formation. In this study, we demonstrate that intrahippocampal grafts of cholinergic-rich striatal tissue also ameliorate spatial memory deficits of rats with fornix lesions. We also found that atropine administration dramatically disrupted spatial navigation performance of rats with striatal grafts and control rats, thus suggesting that the striatal graft effects are mediated by cholinergic mechanisms of action. Measurements of high affinity choline uptake (HACU) and muscarinic receptor binding revealed that intrahippocampal striatal grafts increased HACU and normalized muscarinic receptor binding in animals with fornix lesions. Regression analyses demonstrated significant correlations between the amelioration of spatial memory deficits and hippocampal HACU and receptor binding. We conclude that intrahippocampal grafts of cholinergic-rich striatal tissue can ameliorate spatial memory deficits and that this amelioration is associated with the reinstatement of functional cholinergic terminations. 相似文献
992.
J. C. GARCÍA-ROBAINA F. DE LA TORRE-MORÍN C. VAZQUEZ-MONCHOLI J. FIERRO C. BONNET-MORENO 《Clinical and experimental allergy》1997,27(4):418-423
Background Most published studies on changes of specific IgG or its subclasses as a response to stimuli by allergens have been performed on patients under immunotherapy. There are few reports analysing the response to immunoglobulins in patients exposed to allergens in their natural habitats. Objective The aim of this work was to discover the natural history of Apis specific IgG (IgG-ap) and IgG4 (IgG4-ap) levels in beekeepers from the Canary Islands. Methods We studied 242 beekeepers (Bks). We used a questionnaire and measured total IgE and seric Apis specific IgE (IgE-ap), IgG-ap and IgG4-ap against Apis mellifera venom. Results All Bks had IgG-ap and IgG4-ap. IgE-ap was positive in 160 Bks (65.6 %), but only 92 (37.6 %) Bks were considered sensitized. IgG-ap and IgG4-ap showed significant correlation (r = 0,84); IgE did not correlate with IgG-ap or IgG4-ap. There was no seasonal variation in IgG-ap or IgG4-ap. The group of sensitized Bks had significantly lower IgG-ap and IgG4-ap levels (P < 0.05). The groups with longer beekeeping activity showed significantly higher levels of IgG-ap and IgG4-ap (P < 0.001). Bks with locals reactions had significantly higher IgG-ap and IgG4-ap than Bks who reported systemic reactions (P < 0.05). Conclusion Our study showed that IgG-ap and IgG4-ap appear to increase in Bks, either according to their beekeeping experience or in subjects with local reactions after bee stings. 相似文献
993.
The porosity of the epithelial basement membrane (basal lamina) overlying lymphoid follicles within Peyer's patches was studied in rats and monkeys by scanning electron microscopy. Basement membranes of lymphoid follicles are markedly porous, more conspicuously so than those of adjacent villus cores. The porosity increases centrifugally from the apex of the follicle to its periphery, where the basement membrane continues into the cul-de-sacs of the crypts. Such porosity may facilitate bidirectional passage of lymphocytes during an immune response. The unique structure of the basement membrane overlying lymphoid follicles suggests a biologic adaptation of this tissue boundary to a specific physiologic activity of the organism. 相似文献
994.
A. DAVIES
frcp consultant J. BAGG
phd professor D. LAVERTY
msc nurse consultant M. FILBET
md director J. DE ANDRÉS
md associate professor S. MERCADANTE
md director 《European journal of cancer care》2010,19(2):172-177
DAVIES A., BAGG J., LAVERTY D., SWEENEY P., FILBET M., NEWBOLD K., DE ANDRÉS J. & MERCADANTE S. (2010) European Journal of Cancer Care 19 , 172–177 Salivary gland dysfunction (‘dry mouth’) in patients with cancer: a consensus statement A group of interested professionals was convened to develop some evidence‐based recommendations on the management of salivary gland dysfunction (SGD) in oncology patients. A Medline search was performed to identify the literature on SGD. The abstracts of all identified papers were read, and the full texts of all relevant papers were reviewed. The evidence was graded according to the Scottish Intercollegiate Guidelines Network grading system for recommendations in evidence‐based guidelines. The summary of the main recommendations are: (1) patients with cancer should be regularly assessed for SGD (grade of recommendation – D); (2) the management of SGD should be individualised (D); (3) consideration should be given to strategies to prevent the development of radiation‐induced SGD (C); (4) consideration should be given to treatment of the cause(s) of the SGD (C); (5) the treatment of choice for the symptomatic management of SGD is use of an appropriate saliva stimulant (C); (6) consideration should be given to prevention of the complications of the SGD (D); (7) consideration should be given to treatment of the complications of the SGD (D); and (8) patients with SGD should be regularly reassessed (D). 相似文献
995.
996.
Follicular dendritic cell (FDC) sarcoma is a rare and probably even underreported entity. Only approximately some 50 cases have been described in the literature, the majority of which had a lymph node origin. The authors report a case of FDC sarcoma arising within the soft tissues of the abdominal cavity. As FDC markers are often not routinely included in antibody panels, awareness of this sarcoma is important, as it can be confused with other tumors, especially when occurring extranodally. 相似文献
997.
Risk factors for the presence of high-level shedders of Escherichia coli O157 on Scottish farms
下载免费PDF全文
![点击此处可从《Journal of clinical microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Chase-Topping ME McKendrick IJ Pearce MC MacDonald P Matthews L Halliday J Allison L Fenlon D Low JC Gunn G Woolhouse ME 《Journal of clinical microbiology》2007,45(5):1594-1603
Escherichia coli O157 infections are the cause of sporadic or epidemic cases of often bloody diarrhea that can progress to hemolytic uremic syndrome (HUS), a systematic microvascular syndrome with predominantly renal and neurological complications. HUS is responsible for most deaths associated with E. coli O157 infection. From March 2002 to February 2004, approximately 13,000 fecal pat samples from 481 farms with finishing/store cattle throughout Scotland were examined for the presence of E. coli O157. A total of 441 fecal pats from 91 farms tested positive for E. coli O157. From the positive samples, a point estimate for high-level shedders was identified using mixture distribution analysis on counts of E. coli O157. Models were developed based on the confidence interval surrounding this point estimate (high-level shedder, greater than 10(3) or greater than 10(4) CFU g(-1) feces). The mean prevalence on high-level-shedding farms was higher than that on low-level-shedding farms. The presence of a high-level shedder on a farm was found to be associated with a high proportion of low-level shedding, consistent with the possibility of a higher level of transmission. Analysis of risk factors associated with the presence of a high-level shedder on a farm suggested the importance of the pathogen and individual host rather than the farm environment. The proportion of high-level shedders of phage 21/28 was higher than expected by chance. Management-related risk factors that were identified included the type of cattle (female breeding cattle) and cattle stress (movement and weaning), as opposed to environmental factors, such as water supply and feed. 相似文献
998.
999.
Lamarche LJ Driver HS Wiebe S Crawford L DE Koninck JM 《Journal of sleep research》2007,16(3):262-268
The objective of this study is to examine daytime sleepiness and alertness and nap characteristics among women with significant emotional/behavioral premenstrual symptoms, and to determine their relationship with nocturnal sleep. Participants spent one night during the follicular phase and two nights during the late-luteal phase, one of which occurred after a 40 min opportunity to nap, sleeping in the laboratory. Subjective measures of sleepiness and alertness were completed during the afternoon of each recording. Setting took place at the sleep laboratory at the University of Ottawa. A total number of participants were 10 women with significant and nine women with minimal emotional/behavioral premenstrual symptoms (mean age 26 years). The results were compared with the follicular phase, both groups of women had less slow wave sleep and more stage 2 sleep at night, as well as a higher daytime and nocturnal mean and maximum temperature during the late-luteal phase. Women with significant symptoms were sleepier and less alert during the late-luteal phase and had a higher overall mean nocturnal temperature compared with women with minimal symptoms. No significant differences were found between the two groups on nap characteristics and nocturnal sleep characteristics. Results show that women with more severe premenstrual symptoms are sleepier during the late-luteal phase than women with minimal symptoms. The increased daytime sleepiness seems to be unrelated to nocturnal sleep or nap characteristics. 相似文献
1000.
Liu WC Shaw DJ Matthews L Hoyle DV Pearce MC Yates CM Low JC Amyes SG Gunn GJ Woolhouse ME 《Epidemiology and infection》2007,135(8):1316-1323
Mathematical models are constructed to investigate the population dynamics of Verocytotoxin-producing Escherichia coli (VTEC) serogroups O26 and O103 in two different calf cohorts. We compare the epidemiological characteristics of these two serogroups within the same calf cohort as well as the same serogroups between the two calf cohorts. The sources of infection are quantified for both calf cohort studies. VTEC serogroups O26 and O103 mainly differ in the rate at which calves acquire infection from sources other than infected calves, while infected calves typically remain infectious for less than 1 week regardless of the serogroups. Fewer than 20% of VTEC-positive samples are the result of calf-to-calf transmission. PFGE typing data are available for VTEC-positive samples to further subdivide the serogroup data in one of the two calf cohort studies. For serogroup O26 but not O103, there is evidence for unequal environmental exposure to infection with different PFGE types. 相似文献