全文获取类型
收费全文 | 21739篇 |
免费 | 1934篇 |
国内免费 | 99篇 |
专业分类
耳鼻咽喉 | 235篇 |
儿科学 | 698篇 |
妇产科学 | 397篇 |
基础医学 | 2999篇 |
口腔科学 | 332篇 |
临床医学 | 2380篇 |
内科学 | 4407篇 |
皮肤病学 | 322篇 |
神经病学 | 1907篇 |
特种医学 | 862篇 |
外国民族医学 | 3篇 |
外科学 | 2697篇 |
综合类 | 504篇 |
一般理论 | 14篇 |
预防医学 | 2212篇 |
眼科学 | 732篇 |
药学 | 1605篇 |
中国医学 | 24篇 |
肿瘤学 | 1442篇 |
出版年
2022年 | 126篇 |
2021年 | 327篇 |
2020年 | 241篇 |
2019年 | 364篇 |
2018年 | 384篇 |
2017年 | 285篇 |
2016年 | 336篇 |
2015年 | 409篇 |
2014年 | 568篇 |
2013年 | 836篇 |
2012年 | 1226篇 |
2011年 | 1307篇 |
2010年 | 648篇 |
2009年 | 682篇 |
2008年 | 1093篇 |
2007年 | 1276篇 |
2006年 | 1175篇 |
2005年 | 1204篇 |
2004年 | 1166篇 |
2003年 | 997篇 |
2002年 | 995篇 |
2001年 | 456篇 |
2000年 | 478篇 |
1999年 | 493篇 |
1998年 | 350篇 |
1997年 | 253篇 |
1996年 | 286篇 |
1995年 | 243篇 |
1994年 | 212篇 |
1993年 | 200篇 |
1992年 | 317篇 |
1991年 | 319篇 |
1990年 | 314篇 |
1989年 | 318篇 |
1988年 | 296篇 |
1987年 | 278篇 |
1986年 | 300篇 |
1985年 | 263篇 |
1984年 | 222篇 |
1983年 | 168篇 |
1982年 | 168篇 |
1981年 | 145篇 |
1980年 | 142篇 |
1979年 | 200篇 |
1978年 | 152篇 |
1977年 | 124篇 |
1976年 | 108篇 |
1975年 | 109篇 |
1974年 | 115篇 |
1973年 | 133篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
81.
Skin cancer is the most common malignancy in the United States accounting for more than 840,000 cases and 9,400 deaths annually. It is estimated that 90% of non-melanoma skin cancers and much of melanoma incidence can be attributed to sun exposure. The evidence suggests that regular use of sunscreen (Sun Protective Factor (SPF) of 15 or higher), wearing protective, tightly woven clothing and wide brimmed hats, and avoiding sun exposure when the ultraviolet rays are strongest (between 11:00 a.m. and 3:00 p.m.) can dramatically reduce the risk of skin cancer. Interventions to promote sun-protection behaviors that target children and adults are necessary to reduce the growing incidence rate of skin cancer in the United States.MA during the time of this research 相似文献
82.
Alister Oliver Mark Wright Andrew Matson Graham Woodrow Neil King Louise Dye 《Nephrology, dialysis, transplantation》2004,19(11):2883-2885
BACKGROUND: Interdialytic weight gain (IDWG) can be reduced by lowering the dialysate sodium concentration ([Na]) in haemodialysis patients. It has been assumed that this is because thirst is reduced, although this has been difficult to prove. We compared thirst patterns in stable haemodialysis patients with high and low IDWG using a novel technique and compared the effect of low sodium dialysis (LSD) with normal sodium dialysis (NSD). METHODS: Eight patients with initial high IDWG and seven with low IDWG completed hourly visual analogue ratings of thirst using a modified palmtop computer during the dialysis day and the interdialytic day. The dialysate [Na] was progressively reduced by up to 5 mmol/l over five treatments. Dialysis continued at the lowest attained [Na] for 2 weeks and the measurements were repeated. The dialysate [Na] then returned to baseline and the process was repeated. RESULTS: Baseline interdialytic day mean thirst was higher than the dialysis day mean for the high IDWG group (49.9+/-14.0 vs 36.2+/-16.6) and higher than the low weight gain group (49.9+/-14.0 vs 34.1+/-14.6). This trend persisted on LSD, but there was a pronounced increase in post-dialysis thirst scores for both groups (high IDWG: 46+/-13 vs 30+/-21; low IDWG: 48+/-24 vs 33+/-18). The high IDWG group demonstrated lower IDWG during LSD than NSD (2.23+/-0.98 vs 2.86+/-0.38 kg; P<0.05). CONCLUSIONS: Our results indicate that patients with high IDWG experience more intense feelings of thirst on the interdialytic day. LSD reduces their IDWG, but paradoxically increases thirst in the immediate post-dialysis period. 相似文献
83.
W D Foltz Y Yang J J Graham J S Detsky G A Wright A J Dick 《Magnetic resonance in medicine》2006,56(6):1311-1319
MRI evaluations of intramyocardial hemorrhage in acute infarction have relied on T(2) and T(2)(*) shortening only. We propose a more comprehensive evaluation of hemorrhagic infarction based on the concept that fluctuations in T(2) and T(1) relaxation in acute reperfused infarction will reflect transient edema and hemoglobin oxidative denaturation to uncompartmentalized methemoglobin. Anteroapical infarction was created via percutaneous balloon in young swine (22-25 kg, N = 12). T(2), T(1), diastolic wall thickness (DWT), and the Gd-DTPA partition coefficient (lambda) were measured on days 0, 2, and 7. DWT was elevated at 1 hr postreperfusion (128% +/- 53%, P = 0.0001), and alleviated on days 2 and 7 (48% +/- 10%, P = 0.008; 53% +/- 24%, P = 0.003). T(2) and T(1) elevations were coincident with early edema (DeltaT(2) = 55% +/- 24%, P < 0.0001; DeltaT(1) = 27% +/- 18%, P < 0.04). T(2) and T(1) were nearly normal on day 2 (DeltaT(2) = 8% +/- 8%, P = 0.27; DeltaT(1) = 0% +/- 1%, P = 0.65). On day 7, T(2) increased while T(1) decreased (DeltaT(2) = 27% +/- 16%, P = 0.005; DeltaT(1) = -14% +/- 10%, P = 0.02). Lambda was elevated by >150% at all time points (P < or = 0.002). Histology verified hemorrhagic injury. T(1) and T(2) fluctuations are consistent with transient edema, as well as hemoglobin oxidative denaturation to decompartmentalized methemoglobin. This methodological development may broaden our understanding of hemorrhagic microvascular injury and improve its detection in clinical populations. 相似文献
84.
Short-Ti inversion-recovery pulse sequence: analysis and initial experience in cancer imaging 总被引:2,自引:0,他引:2
Inversion recovery (IR), commonly considered a pulse sequence capable of producing T1-weighted images with excellent display of normal anatomy, is versatile: The null point and peak time provide a useful, succinct summary of the properties of IR and its capacity for producing both T1- and T2-weighted images. Shortening of the inversion time (TI) and creation of a short-TI inversion-recovery (STIR) pulse sequence increases sensitivity to malignancy and other abnormalities by making the effects of prolonged T1 and T2 on signal intensity additive and by nulling the signal from fat. The authors examined over 300 patients with various malignancies and compared STIR images with T1- and T2-weighted images obtained at 0.5 T. In 43 cases, signal-difference-to-noise ratios (SD/Ns) were calculated between tumor, fat, and muscle. In general, STIR images demonstrated tumor as a conspicuously high-intensity area in a background of muted, discernible anatomic detail. The good contrast achieved with STIR sequences between tumor and fat (SD/N = 18.1) and tumor and muscle (SD/N = 12.9) consolidated into a single image the information contained separately on T1- and T2-weighted images, which facilitates efficient detection and localization of malignancy. 相似文献
85.
J J Grome G Gojowczyk W Hofmann D I Graham 《Journal of cerebral blood flow and metabolism》1988,8(1):89-95
This study was carried out with a recently developed model of focal cerebral ischemia in the rat based on the photochemical induction of thrombotic stroke using the dye Rose Bengal. We examined the change in the volume of the lesion and brain water content, in separate groups of rats, at different times (1, 4, 24, 72, and 168 h) after the induction of the ischemic lesion. The volume of ischemic damage increased rapidly between 1 and 24 h after the ischemic insult and decreased between 24 and 168 h. The lesion at 168 h was significantly larger than that following 1 h of ischemia and similar to that obtained at 4 h, suggesting that the maximum extent of tissue damage (without the involvement of significant edema) was reached within the first 4 h in this model. The enlargement of the lesion after 4 h correlated closely with changes in brain water content. 相似文献
86.
Two patients with recurrent symptomatic pericardial effusions secondary to malignant disease were successfully treated by percutaneous balloon pericardiotomy. Open surgery was avoided and the procedure was completed under local anaesthesia in less than 40 minutes. The first patient was free of recurrence at nine months but pericardial effusion recurred at two months in the second patient.Percutaneous balloon pericardiotomy offers a potentially important new means of relieving recurrent tamponade and substantially reduces trauma to the patient. 相似文献
87.
Sixteen cases of histopathologically proved solitary rectal ulcer syndrome were encountered. Fifteen patients underwent barium enema study; in nine cases the findings--including rectal stricture, granularity of the mucosa, and thickened rectal folds-were nonspecific. In six cases the study was normal. All patients had a long history of defecation disorders, and defecography was performed in all. In seven cases, intussusception of the rectal wall was seen; in another case the intussusception was accompanied by a rectocele. One case showed rectal prolapse. In four cases, failed relaxation of the puborectalis occurred and prevented the passage of the bolus; in another case there was abnormal perineal descent. In two patients studies were normal. In patients with defecation disorders, the possibility of this syndrome should be considered. Defecography is the method of choice for establishing the diagnosis. 相似文献
88.
SPECT was used to identify a focal accumulation of cardiac calcification using Tc-99m MDP in a patient with an arrhythmia and known metastatic calcification elsewhere. 相似文献
89.
Julia E. Ledger MSc Graham J. Watson Dr. Juliet E. Compston MD 《Digestive diseases and sciences》1986,31(4):361-368
The biliary excretion of radioactivity after intravenous [3H]25-hydroxyvitamin D3 was studied in nine patients with T-tube bile drainage. The mean +/- SD 24-hr radioactivity excretion in T-tube bile expressed as a percentage of the administered dose was 6.7 +/- 2.9%; after correction for incomplete bile collection, the value obtained was 16.0 +/- 11.1%. Chloroform solubility of biliary radioactivity increased from 27.4 +/- 8.9% to 72.9 +/- 10.1% following incubation with beta-glucuronidase. High-performance liquid chromatographic analysis of chloroform extracts of bile revealed that most of the eluted radioactivity was more polar than [3H]25-hydroxyvitamin D3. No free [3H]25-hydroxyvitamin D3 was demonstrated. Thus in man, most of the biliary radioactivity excreted following [3H]25-hydroxyvitamin D3 is in the form of water-soluble compounds, mainly glucuronides. However, our results suggest that glucuronides of metabolites other than 25-OHD3 are predominantly formed. 相似文献
90.
J A Bond G J Graham M Freshney T Dawson N Sawhney E D Williams D Wynford-Thomas 《Molecular and cellular endocrinology》1992,84(1-2):R15-R21
Normal adult human thyroid follicular cells have an extremely limited proliferative capacity in vitro. No previously studied mitogen, including thyrotropin (TSH) or epidermal growth factor (EGF), has in our hands resulted in a significant improvement over the 3-4% nuclear [3H]thymidine pulse-labelling index (LI) obtainable with 10% fetal calf serum. Here we report the detection in the conditioned medium from a sub-clone of NIH3T3 fibroblasts of a mitogenic activity capable of increasing this response up to 10-fold, to an LI of over 20%, together with an even greater relative stimulation of mitotic activity. Preliminary characterisation has excluded EGF and TGF alpha, and demonstrated that the activity is bound reversibly by heparin-Sepharose, thus pointing to a member of the heparin-binding fibroblast- or hepatocyte-growth factor families. This material should have wide practical application in facilitating primary culture of follicular cells, and may reveal new mechanisms of stromal-epithelial interaction regulating normal and neoplastic thyroid growth in vivo. 相似文献