全文获取类型
收费全文 | 5629篇 |
免费 | 631篇 |
国内免费 | 16篇 |
专业分类
耳鼻咽喉 | 11篇 |
儿科学 | 250篇 |
妇产科学 | 244篇 |
基础医学 | 868篇 |
口腔科学 | 128篇 |
临床医学 | 584篇 |
内科学 | 986篇 |
皮肤病学 | 153篇 |
神经病学 | 506篇 |
特种医学 | 347篇 |
外科学 | 614篇 |
综合类 | 148篇 |
一般理论 | 5篇 |
预防医学 | 615篇 |
眼科学 | 145篇 |
药学 | 332篇 |
中国医学 | 20篇 |
肿瘤学 | 320篇 |
出版年
2021年 | 69篇 |
2019年 | 65篇 |
2018年 | 93篇 |
2017年 | 75篇 |
2016年 | 87篇 |
2015年 | 77篇 |
2014年 | 110篇 |
2013年 | 143篇 |
2012年 | 204篇 |
2011年 | 195篇 |
2010年 | 155篇 |
2009年 | 161篇 |
2008年 | 209篇 |
2007年 | 229篇 |
2006年 | 240篇 |
2005年 | 178篇 |
2004年 | 187篇 |
2003年 | 190篇 |
2002年 | 208篇 |
2001年 | 191篇 |
2000年 | 192篇 |
1999年 | 181篇 |
1998年 | 116篇 |
1997年 | 97篇 |
1996年 | 118篇 |
1995年 | 88篇 |
1994年 | 88篇 |
1993年 | 102篇 |
1992年 | 140篇 |
1991年 | 119篇 |
1990年 | 134篇 |
1989年 | 148篇 |
1988年 | 124篇 |
1987年 | 140篇 |
1986年 | 133篇 |
1985年 | 123篇 |
1984年 | 102篇 |
1983年 | 85篇 |
1982年 | 76篇 |
1981年 | 50篇 |
1980年 | 58篇 |
1979年 | 69篇 |
1978年 | 56篇 |
1977年 | 58篇 |
1976年 | 55篇 |
1975年 | 57篇 |
1974年 | 53篇 |
1973年 | 52篇 |
1972年 | 45篇 |
1967年 | 35篇 |
排序方式: 共有6276条查询结果,搜索用时 0 毫秒
991.
Aitken WA Chisholm AW Duncan AW Harper MJ Humphries SE Mann JI Murray Skeaff C Sutherland WH Wallace AJ Williams SM 《Nutrition, metabolism, and cardiovascular diseases : NMCD》2006,16(5):353-363
BACKGROUND AND AIMS: Some individuals respond to a greater extent than others to changes in dietary fat and cholesterol even when dietary intake is consistent. A prospective study has been undertaken in which two groups of individuals according to cholesteryl ester transfer protein (CETP) genotype were compared in terms of plasma lipid response to altering the nature of dietary fat in a free-living situation. METHODS AND RESULTS: Following genotyping, 35 individuals with the CETP Taq1 B1B1 genotype were paired with age and sex-matched individuals with one or two CETP B2 alleles, to undertake a single crossover trial with a diet high in saturated fat and a diet high in polyunsaturated fat. There was no washout period between the two 4-week phases. Plasma lipoproteins were measured at the beginning and end of each phase. The difference (95% CI) in plasma LDL-cholesterol concentration at the end of the PUFA and SAFA diets was 0.95 (0.71, 1.19) mmol/l in the CETP B1B1 group and 0.80 (0.57, 1.04) mmol/l in the group with at least one CETP B2 allele. The dietary induced changes in the two genotype groups were not significantly different (p=0.38) from each other. Comparable results were observed for plasma total cholesterol. The high PUFA and SAFA diets did not significantly alter plasma HDL concentration in either of the CETP genotype groups. Response was also similar according to apolipoprotein E genotype (E3E3 vs E4+) and lipoprotein lipase genotype (S447X). CONCLUSIONS: The results of this study do not support previous studies in which CETP genotype predicted plasma LDL-cholesterol response to diet. CETP genotype does not significantly affect the change in plasma total and LDL-cholesterol concentrations that occur when altering the nature of dietary fat. These data suggest that the influence of genetic factors on total and LDL-cholesterol may be relatively small in comparison with the effect of dietary manipulation. 相似文献
992.
Current evidence suggests that multiple neural mechanisms contribute to the fatal lethal event in SIDS. The processes may develop from a range of otherwise seemingly-innocuous circumstances, such as unintended external airway obstruction or accidental extreme flexion of the head of an already-compromised structure of the infant upper airway. The fatal event may occur in a sleep state which can suppress muscle tone essential to restore airway patency or exert muscle action to overcome a profound loss of blood pressure. Neural processes that could overcome those transient events with reflexive compensation appear to be impaired in SIDS infants. The evidence ranges from subtle physiological signs that appear very early in life, to autopsy findings of altered neurotransmitter, including serotonergic, systems that have extensive roles in breathing, cardiovascular regulation, and thermal control. Determination of the fundamental basis of SIDS is critical to provide biologic plausibility to SIDS risk reduction messages and to develop specific prevention strategies. 相似文献
993.
Harper JM Durkee SJ Dysko RC Austad SN Miller RA 《The journals of gerontology. Series A, Biological sciences and medical sciences》2006,61(10):1019-1029
Previously we showed that mouse stocks derived from wild-caught progenitors are long-lived relative to genetically heterogeneous mice derived from laboratory-adapted strains. Here we replicate this life-span effect, and show that F2 hybrids between wild-derived and laboratory-derived stocks have intermediate survival patterns. Moreover, wild-derived mice are small, lean, and slow to mature, and have low serum insulin-like growth factor-I (IGF-I) relative to genetically heterogeneous mice. These traits, too, were at intermediate levels in the F2 hybrids. Furthermore, serum IGF-I at 6 months was a significant predictor of life span in two different populations of F2 hybrid mice. Pooling across stocks, life span was negatively correlated with body weight and serum IGF-I levels, and positively correlated with age at vaginal patency and serum leptin levels. Overall, these finding suggest that wild-derived mice harbor alleles that increase longevity, perhaps through effects on growth, maturation, and early-life hormone levels. 相似文献
994.
Hiscox S Jordan NJ Jiang W Harper M McClelland R Smith C Nicholson RI 《Endocrine-related cancer》2006,13(4):1085-1099
Our previous investigations using cell models of tamoxifen resistance have shown that the acquisition of an endocrine-insensitive state is accompanied by an invasive in vitro phenotype. In this study, we wished to determine whether this was specifically related to partial oestrogen receptor agonists or whether similar phenomena arise with the newer 'pure' anti-oestrogens, exemplified by fulvestrant. Our data demonstrate that the development of fulvestrant resistance in two breast cancer cell lines, MCF7 and T47D, is accompanied by an augmented migratory and invasive phenotype in vitro and overexpression of the HGF/SF receptor, c-Met. Importantly, upregulated c-Met expression in these cells facilitates their stimulation by HGF/SF-secreting stromal fibroblasts, leading to the activation of Src, Akt and ERK1/2 and a profound enhancement of their aggressive phenotype in vitro. These effects could be specifically attributable to activation of the c-Met receptor since the inclusion of neutralising antibodies to c-Met, or siRNA-mediated knockdown of c-Met expression, suppressed both invasion and migration stimulated by either exogenous HGF/SF, fibroblast-conditioned medium or following co-culture with fibroblast cells. Together, these in vitro data suggest that the development of fulvestrant resistance in vivo may confer a metastatic advantage to the cells by allowing their migratory and invasive behaviour to be augmented by surrounding stromal cells. 相似文献
995.
OBJECTIVE: To compare the efficacy and safety of once-daily telmisartan and ramipril on blood pressure (BP) reductions during the last 6 h of the dosing interval. PATIENTS AND METHODS: In a prospective, randomized, open-label, blinded-endpoint study using ambulatory BP monitoring, 801 patients with mild-to-moderate hypertension were randomly assigned to once-daily treatment with telmisartan 80 mg for 14 weeks or ramipril 5 mg for 8 weeks and then force titrated to ramipril 10 mg for the last 6 weeks. Primary endpoints were the reduction from baseline in the last 6-h mean ambulatory systolic BP (SBP) and diastolic BP (DBP). Secondary endpoints included changes in 24-h, morning, daytime and night-time mean ambulatory BP and ambulatory BP response rates. RESULTS: Telmisartan 80 mg produced greater reductions in the last 6-h mean ambulatory SBP and DBP compared with ramipril 5 mg (P < 0.0001) and 10 mg (P < 0.0001), and was superior to ramipril for all secondary ambulatory SBP and DBP endpoints (P < 0.05). Ambulatory BP response rates (24-h mean ambulatory SBP/DBP < 130/80 mmHg or reduction from baseline > or = 10 mmHg) were greater with telmisartan 80 mg (P < 0.01) than with ramipril 5 and 10 mg. Ramipril was associated with a higher incidence of treatment-related cough (5.7 versus 0.5% for telmisartan). CONCLUSIONS: Telmisartan was significantly more effective than ramipril in reducing BP throughout the 24-h dosing interval and particularly during the last 6 h, a time when patients appear to be at greatest risk of cerebro- and cardiovascular events. Both drugs were well tolerated, although ramipril was associated with a higher incidence of cough. 相似文献
996.
Multicentric assessment of the safety of neonatal videosurgery 总被引:1,自引:0,他引:1
Kalfa N Allal H Raux O Lardy H Varlet F Reinberg O Podevin G Héloury Y Becmeur F Talon I Harper L Vergnes P Forgues D Lopez M Guibal MP Galifer RB 《Surgical endoscopy》2007,21(2):303-308
Background Complex procedures for managing congenital abnormalities are reported to be feasible. However, neonatal videosurgery involves
very specific physiologic constraints. This study evaluated the safety and complication rate of videosurgery during the first
month of life and sought to determine both the risk factors of perioperative complications and the most recent trends in practice.
Methods From 1993 to 2005, 218 neonates (mean age, 16 days; weight, 3,386 g) from seven European university hospitals were enrolled
in a retrospective study. The surgical indications for laparoscopy (n = 204) and thoracoscopy (n = 14) were congenital abnormalities or exploratory procedures.
Results Of the 16 surgical incidents that occurred (7.5%), mainly before 2001, 11 were minor (parietal hematoma, eventration). Three
neonates had repeat surgery for incomplete treatment of pyloric stenosis. In two cases, the incidents were more threatening
(duodenal wound, diaphragmatic artery injury), but without further consequences. No mortality is reported. The 26 anesthetic
incidents (12%) that occurred during insufflation included desaturation (<80% despite 100% oxygen ventilation) (n = 8), transient hypotension requiring vascular expansion (n = 7), hypercapnia (>45 mmHg) (n = 5), hypothermia (<34.9°C) (n = 4), and metabolic acidosis (n = 2). The insufflation had to be stopped in 7% of the cases (transiently in 9 cases, definitively in 6 cases). The significant
risk factors for an incident (p < 0.05) were young age of the patient, low body temperature, thoracic insufflation, high pressure and flow of insufflation,
and length of surgery.
Conclusion Despite advances in miniaturizing of instruments and growth in surgeons’ experience, the morbidity of neonatal videosurgery
is not negligible. A profile of the patient at risk for an insufflation-related incident emerged from this study and may help
in the selection of neonates who will benefit most from these techniques in conditions of maximal safety. 相似文献
997.
998.
Epigallocatechin-3-Gallate suppresses early stage, but not late stage prostate cancer in TRAMP mice: mechanisms of action 总被引:1,自引:0,他引:1
BACKGROUND: Prostate cancer (PCa) is the second leading cause of cancer-related death in men in the United States. Many men have implemented purported chemopreventive agents into their daily diet in an attempt to delay the early onset of a PCa. Green tea polyphenols, one such agent, has been shown to be chemopreventive in skin, breast, and prostate cancers. We hypothesized that Epigallocatechin-3-Gallate (EGCG), the major polyphenol found in green tea, will exert its chemopreventive effect in the prostate via regulation of sex steroid receptor, growth factor-signaling, and inflammatory pathways. METHODS: Five-week-old male TRAMP (Transgenic Adenocarcinoma Mouse Prostate) offspring were fed AIN-76A diet and 0.06% EGCG in tap water. Animals were sacrificed at 28 weeks of age and the entire prostates were scored histopathologically. In addition, animals were sacrificed at 12 weeks of age and ventral (VP) and dorsolateral (DLP) prostates were removed for histopathological evaluation and immunoblot analyses or ELISA. RESULTS: EGCG, inhibited early but not late stage PCa in the current study. In the VP, EGCG significantly reduced cell proliferation, induced apoptosis, and decreased androgen receptor (AR), insulin-like growth factor-1 (IGF-1), IGF-1 receptor (IGF-1R), phospho-extracellular signal-regulated kinases 1 and 2 (phospho-ERKs 1 and 2), cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS). CONCLUSIONS: The attenuation of the AR, the down-regulation of potent growth factor IGF-1, modulation of inflammation biomarkers, and decrease in the MAPK signaling may contribute to the reduction in cell proliferation and induction of apoptosis and hence provide a biochemical basis for EGCG suppressing PCa without toxicity. 相似文献
999.
Nixon M Taylor G Sheldon P Iqbal SJ Harper W 《The Journal of bone and joint surgery. British volume》2007,89(10):1303-1308
We matched 78 patients with a loose cemented Charnley Elite Plus total hip replacement (THR) by age, gender, race, prosthesis and time from surgery with 49 patients with a well-fixed stable hip replacement, to determine if poor bone quality predisposes to loosening. Clinical, radiological, biomechanical and bone mineral density indicators of bone quality were assessed. Patients with loose replacements had more pain, were more likely to have presented with atrophic arthritis and to have a history of fragility fracture, narrower femoral cortices and lower peri-prosthetic or lumbar spine bone mineral density (all t-test, p < 0.01). They also tended to be smokers (chi-squared test, p = 0.08). Vitamin-D deficiency was common, but not significantly different between the two groups (t-test, p = 0.31) In this series of cemented hip replacements performed between 1994 and 1998, aseptic loosening was associated with poor bone quality. Patients with a THR should be screened for osteoporosis and have regular radiological surveillance. 相似文献
1000.
Roberts VI Esler CN Harper WM 《The Journal of bone and joint surgery. British volume》2007,89(11):1452-1456
This is a 15-year follow-up observational study of 4390 patients with 4606 primary total knee replacements (TKRs) implanted in the Trent health region between 1990 and 1992. The operations were performed in 21 hospitals, including both district general and teaching hospitals, with 77 different surgeons as named consultant. The main objective was to analyse the survival of the patients and of the prostheses, and to evaluate what impact different variables have on survival. In addition, the 1480 patients (33.7%) (1556 TKRs) alive at 15 years following operation were sent a self-administered questionnaire which examined their level of satisfaction, of pain, and their quality of life at 15 years. Completed responses were received from 912 TKRs (58.6%). Three survival curves were constructed: a best-case scenario based on the patients entered into the life tables, another included failures not reported in the revision database, and a third worst-case scenario based on all patients lost to follow-up presumed to have had a failed primary TKR. In the best-case scenario survival at 15 years was 92.2%, and in the worst-case scenario was 81.1%. Survival was significantly increased in women and older patients (Mantel-Cox log-rank test, p < 0.005 and p < 0.001, respectively). Revision as a result of infection was required in 40 TKRs (18.8%) representing 0.87% of the original cohort. The limited information available from the questionnaire indicated that satisfaction was less frequent among men, patients with osteoarthritis and those who required revision (chi-squared test, p < 0.05, p < 0.05 and p < 0.0001, respectively). With regard to pain, older patients, females and patients who still had their primary replacement in place at 15 years, reported the least pain (chi-squared test for trends, p < 0.0005, p < 0.005 and p < 0.0001, respectively). The reported quality of life was not affected by any variable. 相似文献