全文获取类型
收费全文 | 1908篇 |
免费 | 141篇 |
国内免费 | 22篇 |
专业分类
耳鼻咽喉 | 1篇 |
儿科学 | 87篇 |
妇产科学 | 47篇 |
基础医学 | 191篇 |
口腔科学 | 81篇 |
临床医学 | 218篇 |
内科学 | 399篇 |
皮肤病学 | 57篇 |
神经病学 | 140篇 |
特种医学 | 262篇 |
外科学 | 233篇 |
综合类 | 41篇 |
一般理论 | 1篇 |
预防医学 | 95篇 |
眼科学 | 17篇 |
药学 | 73篇 |
1篇 | |
肿瘤学 | 127篇 |
出版年
2022年 | 8篇 |
2021年 | 19篇 |
2020年 | 23篇 |
2019年 | 24篇 |
2018年 | 34篇 |
2017年 | 19篇 |
2016年 | 18篇 |
2015年 | 38篇 |
2014年 | 43篇 |
2013年 | 79篇 |
2012年 | 72篇 |
2011年 | 72篇 |
2010年 | 73篇 |
2009年 | 69篇 |
2008年 | 49篇 |
2007年 | 57篇 |
2006年 | 61篇 |
2005年 | 58篇 |
2004年 | 39篇 |
2003年 | 65篇 |
2002年 | 49篇 |
2001年 | 40篇 |
2000年 | 38篇 |
1999年 | 45篇 |
1998年 | 86篇 |
1997年 | 83篇 |
1996年 | 64篇 |
1995年 | 56篇 |
1994年 | 48篇 |
1993年 | 49篇 |
1992年 | 26篇 |
1991年 | 40篇 |
1990年 | 45篇 |
1989年 | 63篇 |
1988年 | 47篇 |
1987年 | 45篇 |
1986年 | 36篇 |
1985年 | 41篇 |
1984年 | 17篇 |
1983年 | 22篇 |
1982年 | 23篇 |
1981年 | 18篇 |
1980年 | 21篇 |
1979年 | 12篇 |
1978年 | 21篇 |
1977年 | 20篇 |
1976年 | 16篇 |
1975年 | 13篇 |
1971年 | 8篇 |
1967年 | 10篇 |
排序方式: 共有2071条查询结果,搜索用时 15 毫秒
91.
Burwinkel B; Maichele AJ; Aagenaes O; Bakker HD; Lerner A; Shin YS; Strachan JA; Kilimann MW 《Human molecular genetics》1997,6(7):1109-1115
Glycogen storage disease due to phosphorylase kinase deficiency occurs in
several variants that differ in mode of inheritance and tissue-
specificity. This heterogeneity is suspected to be largely due to mutations
affecting different subunits and isoforms of phosphorylase kinase. The gene
of the ubiquitously expressed beta subunit, PHKB, was a candidate for
involvement in autosomally transmitted phosphorylase kinase deficiency of
liver and muscle. To identify such mutations, the complete PHKB coding
sequence was amplified by RT-PCR of RNA isolated from blood samples of
patients and analyzed by direct sequencing of PCR products. The
characterization of mutations was complemented by PCR of genomic DNA. In
one female and four male patients, we identified five independent nonsense
mutations (Y418ter; R428ter; Y974H+E975ter; Q656ter in two cases), one
single-base insertion in codon N421, one splice-site mutation affecting
exon 31, and a large deletion involving the loss of exon 8. Although these
severe translation-disrupting mutations occur in constitutively expressed
sequences of the only known beta subunit gene of phosphorylase kinase,
PHKB, they are associated with a surprisingly mild clinical phenotype,
affecting virtually only the liver, and relatively high residual enzyme
activity of approximately 10%.
相似文献
92.
Mutations in the TSC2 gene: analysis of the complete coding sequence using the protein truncation test (PTT) 总被引:4,自引:0,他引:4
Mutations in the TSC2 gene on chromosome 16p13.3 are responsible for
approximately 50% of familial tuberous sclerosis (TSC). The gene has 41
small exons spanning 45 kb of genomic DNA and encoding a 5.5 kb mRNA. Large
germline deletions of TSC2 occur in <5% of cases, and a number of small
intragenic mutations have been described. We analysed mRNA from 18
unrelated cases of TSC for TSC2 mutations using the protein truncation test
(PTT). Three cases were predicted to be TSC2 mutations on the basis of
linkage analysis or because a hamartoma from the patient showed loss of
heterozygosity for 16p13.3 markers. Three overlapping PCR products,
covering the complete coding sequence of mRNA, were generated from
lymphoblastoid cell lines, translated into 35S-methionine labelled protein,
and analysed by SDS-PAGE. PCR products showing PTT shifts were directly
sequenced, and mutations confirmed by restriction enzyme digestion where
possible. Six PTT shifts were identified. Five of these were caused by
mutations predicted to produce a truncated protein: (i) a sporadic case
showed a 32 bp deletion in exon 11, and a mutant mRNA without exon 11 was
produced; the normal exon 10 was also spliced out; (ii) a sporadic case had
a 1 bp deletion in exon 12 (1634delT); (iii) a TSC2-linked mother and
daughter pair had a G-->T transversion in exon 23 (G2715T) introducing a
cryptic splice site causing a 29 bp truncation of mRNA from exon 23; (iv) a
sporadic case showed a 2 bp deletion in exon 36; (v) a sporadic case showed
a 1 bp insertion disrupting the donor splice site of exon 37 (5007+2insA),
resulting in the use of an upstream exonic cryptic splice site to cause a
29 bp truncation of mRNA from exon 37. In one case, the PTT shift was
explained by in-frame splicing out of exon 10, in the presence of a normal
exon 10 genomic sequence. Alternative splicing of exon 10 of the TSC2 gene
may be a normal variant. Three 3rd base substitution polymorphisms were
also detected during direct sequencing of PCR products. Confirmed mutations
were identified in 28% of the families studied and on the assumption that
half of the sporadic cases should have TSC2 mutations, a crude estimate of
the detection rate would be 60%. This compares favourably with other
screening methods used for TSC2, notably SSCP, and since PTT involves much
less work it may be the method of choice.
相似文献
93.
Telfer JF; Thomson AJ; Cameron IT; Greer IA; Norman JE 《Human reproduction (Oxford, England)》1997,12(10):2306-2312
Superoxide, an agent which attenuates the half-life of nitric oxide, is
metabolized and synthesized by superoxide dismutase (SOD) and xanthine
oxidase, respectively. Over the last few years much work has focused on the
role of nitric oxide in human parturition. The aim of this study was to
determine whether the onset of human parturition is associated with a
change in the expression of copper/zinc superoxide dismutase (Cu/Zn SOD),
manganese superoxide dismutase (Mn SOD) or xanthine oxidase within the
uterus. Samples of myometrium, placenta, decidua and fetal membranes were
obtained from women before and after the onset of labour at term.
Immunocytochemistry was used to localize Cu/Zn SOD, Mn SOD and xanthine
oxidase and measure SOD enzyme activity. Cu/Zn and Mn SOD-like
immunoreactivity was detected in syncytiotrophoblast cells, villous stromal
cells and endothelial cells of blood vessels in the placenta. In the
myometrium Cu/Zn and Mn SOD were localized to myocytes and endothelial
cells and to some vascular smooth muscle cells. In the fetal membranes we
observed staining for Cu/Zn SOD and Mn SOD in the amnion, chorion,
extravillous trophoblast and decidua. There was no difference in SOD enzyme
activity or staining intensity for SOD between different cell types before
and during labour. Xanthine oxidase immunoreactivity was identified in each
of the tissues examined and again there was no difference in immunostaining
in tissues obtained from women delivered before or after the onset of
labour. These results show that the pregnant uterus is capable of both
synthesizing and degrading superoxide and suggest that superoxide dismutase
and xanthine oxidase may play a role in the maintenance of uterine
quiescence during pregnancy, but not in the initiation of parturition.
相似文献
94.
Omar Hayani Lyall AJ Higginson Baldwin Toye Ian G Burwash 《The Canadian journal of cardiology》2009,25(4):e130-e132
Infective endocarditis caused by zoonotic microorganisms is an uncommon clinical entity. A 55-year-old man was diagnosed with endocarditis due to Capnocytophaga canimorsus, a commensal bacterium contained in the saliva of dogs, that involved the aortic and tricuspid valves and was complicated by a para-aortic valve abscess and aorta-to-right atrial fistula. The patient was successfully treated with antibiotic therapy and surgical intervention. C canimorsus endocarditis should be considered in patients with culture-negative endocarditis, particularly in immunosuppressed, asplenic or alcoholic individuals who have recently suffered a dog bite or have had close contact with dogs. 相似文献
95.
B M Biller J F Coughlin V Saxe D Schoenfeld D I Spratt A Klibanski 《Obstetrics and gynecology》1991,78(6):996-1001
Hypothalamic amenorrhea, a common disorder associated with abnormalities in gonadotropin pulsatility and subsequent estrogen deficiency, is usually transient, and treatment indications are unclear unless fertility is desired. To determine whether this disorder is associated with progressive bone loss, we studied 24 women with primary or secondary amenorrhea related to stress or simple weight loss, compared with 31 normal women of the same age. Amenorrheic women had significantly lower (P = .01) body fat (26.4 +/- 7.3 versus 30.6 +/- 4.7%) and higher (P = .0001) urine free cortisol levels (250 +/- 100 versus 140 +/- 50 nmol/day) than normals. Trabecular bone density in women with hypothalamic amenorrhea as assessed by spinal computed tomography was significantly (P = .001) lower than in normals (140.2 +/- 27.3 versus 175.1 +/- 24.6 mg K2HPO4/mL, respectively). Twenty of the 24 amenorrheic women had initial spinal bone density below the mean in normals, and in eight it was 2 standard deviations or more below the normal mean. Initial bone density correlated negatively with duration of amenorrhea (r = -0.489, P = .02) and positively with serum free testosterone levels (r = 0.517, P = .02). Prospective evaluation showed a decline in spinal bone density in those who were amenorrheic for fewer than 5 years. The slope of change in bone density correlated with initial weight, percent ideal body weight, and percent body fat (R2 = 0.597, P = .0003; R2 = 0.549, P = .0007; and R2 = 0.618, P = .0002, respectively).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
96.
PURPOSE: Recruiting participants is a major challenge for population studies. We present the recruitment methods followed by the Diabetic Retinopathy Awareness Program (DRAP), a community-based, randomized, masked, controlled trial to meet and exceed its sample size goals. METHODS: A county-wide multi-media promotional campaign to recruit and enroll participants in the trial was planned and executed from October 1993 through April 1994, with the assistance of the local news media and community and professional groups. A toll-free 800 number recruitment line was established, and postage-paid recruitment postcards distributed. The trial was designed to examine whether a mailed educational intervention could increase compliance with vision care guidelines among persons with diabetes in the community. RESULTS: A total of 2308 persons with diabetes were interviewed for eligibility and 813 enrolled in the intervention trial, exceeding the original recruitment goals of 1800 and 600, respectively. Those who completed the enrollment interview reflected county demographics. During recruitment, newspaper, television and radio stories featured the study; pharmacies and physician offices displayed study materials; public service announcements appeared in local print and broadcast media. The largest single recruitment response was a local television news report, followed by a newspaper story. CONCLUSIONS: These experiences substantiate the need for a comprehensive coordinated approach, using planned multiple sources, to achieve recruitment success. By engaging the lay and professional communities along with the media, recruitment costs can be kept to a minimum. Participant costs can be minimized by employing a toll-free number and eliminating study participant travel, thus allowing for inclusion of traditionally underserved populations. This approach is applicable to other studies, where community-based participation is desired. 相似文献
97.
98.
After the introduction of the colposcope for the examination of children suspected of being sexually abused in Leeds, a study was undertaken to describe the findings in detail. A total of 109 consecutive prepubertal girls, mean age 70.4 months were assessed including colposcopic genital and anal examination, and peer group review of reports and photographs. Fifty nine children had signs consistent with blunt force penetrating trauma (hymenal transection/major notch, scar, or hymenal attenuation). Transections were encountered most commonly at 6 o'clock (directly posterior). In 46 the hymenal orifice was gaping with thigh abduction only and in 47 the hymenal orifice transverse diameter was greater than 4 mm on labial separation. Overall, physical findings were commonly present and in only two cases were no signs recorded. Non-specific and frequent findings included patterns of labial and introital reddening. Supportive hymenal signs including swelling, rounding of edge, thickening, distortion, and loss of symmetry were common. Labial fusion was present in 20. Urethral dilatation with labial separation was noted in 14. Physical findings including normality are consistent with abuse and even minor anogenital signs as well as negative findings should be documented. Colposcopy and photography are valuable tools in peer review, teaching, and case management. 相似文献
99.
AJ Blethyn HR Jenkins R Roberts K Verrier Jones 《Archives of disease in childhood》1995,73(6):534-535
Little objective evidence has been published to support the claim that constipation is an important contributory factor in recurrent urinary tract infection (UTI) in childhood. Using a radiological scoring system, two observers assessed faecal loading from abdominal radiographs of children with proved UTIs. There was a significant increase in the degree of faecal loading in children with UTI when compared with controls (r = 0.237). This difference was mainly accounted for by girls with recurrent (greater than five) UTIs. This study confirms an association between recurrent UTI and faecal loading. Further studies are needed to establish if there is a causal relationship and benefits from treatment. 相似文献
100.
Plasma beta-endorphin levels were measured in five women in physiologic menopause suffering from frequent episodes of hot flushes, recorded objectively by the measurement of finger temperature. Significantly lower levels of plasma beta-endorphin levels were found at the onset of the hot flushes than five to 20 minutes before (P less than .001). After the flush there was a significant rise of plasma beta-endorphin levels at five, ten, and 15 minutes (P less than .002). 相似文献