全文获取类型
收费全文 | 15609篇 |
免费 | 1521篇 |
国内免费 | 111篇 |
专业分类
耳鼻咽喉 | 229篇 |
儿科学 | 583篇 |
妇产科学 | 362篇 |
基础医学 | 1958篇 |
口腔科学 | 447篇 |
临床医学 | 1167篇 |
内科学 | 3499篇 |
皮肤病学 | 601篇 |
神经病学 | 914篇 |
特种医学 | 684篇 |
外国民族医学 | 6篇 |
外科学 | 2642篇 |
综合类 | 150篇 |
一般理论 | 2篇 |
预防医学 | 1135篇 |
眼科学 | 410篇 |
药学 | 1248篇 |
1篇 | |
中国医学 | 90篇 |
肿瘤学 | 1113篇 |
出版年
2023年 | 104篇 |
2022年 | 344篇 |
2021年 | 591篇 |
2020年 | 398篇 |
2019年 | 656篇 |
2018年 | 831篇 |
2017年 | 575篇 |
2016年 | 614篇 |
2015年 | 543篇 |
2014年 | 759篇 |
2013年 | 1037篇 |
2012年 | 1165篇 |
2011年 | 1267篇 |
2010年 | 833篇 |
2009年 | 758篇 |
2008年 | 811篇 |
2007年 | 825篇 |
2006年 | 762篇 |
2005年 | 615篇 |
2004年 | 573篇 |
2003年 | 390篇 |
2002年 | 385篇 |
2001年 | 296篇 |
2000年 | 322篇 |
1999年 | 237篇 |
1998年 | 132篇 |
1997年 | 121篇 |
1996年 | 117篇 |
1995年 | 84篇 |
1994年 | 68篇 |
1993年 | 65篇 |
1992年 | 35篇 |
1991年 | 45篇 |
1990年 | 32篇 |
1989年 | 40篇 |
1988年 | 51篇 |
1987年 | 42篇 |
1986年 | 26篇 |
1985年 | 41篇 |
1984年 | 87篇 |
1983年 | 75篇 |
1982年 | 51篇 |
1981年 | 34篇 |
1980年 | 52篇 |
1979年 | 45篇 |
1978年 | 47篇 |
1977年 | 41篇 |
1976年 | 37篇 |
1975年 | 42篇 |
1974年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
Quantitative SPECT leads to improved performance in discrimination tasks related to prodromal Alzheimer's disease. 总被引:5,自引:0,他引:5
Georges El Fakhri Marie Foley Kijewski Marilyn S Albert Keith A Johnson Stephen C Moore 《Journal of nuclear medicine》2004,45(12):2026-2031
We investigated the impact of the quantitation and reconstruction protocol on clinical tasks. The performance of standard clinical reconstruction procedures in discrimination tasks related to the diagnosis of prodromal Alzheimer's disease (AD) was compared with the performance of a quantitative approach incorporating improved corrections for scatter, attenuation, intrinsic spatial resolution, and distance-dependent spatial resolution. METHODS: Seventeen normal controls (normal group), 56 subjects who did not have dementia, who did have memory problems, but who did not develop AD within 5 y of follow-up (questionable group), and 27 subjects who did not have dementia, who did have memory problems, and who did develop AD over the follow-up period (converter group) were considered in this study. (99m)Tc-hexamethylpropyleneamine oxime SPECT and MRI studies were performed for each subject at baseline. The standard quantitation protocol (STD), routinely used in our clinic, consisted of Compton window scatter correction followed by filtered backprojection with attenuation correction using a uniform attenuation map. In the improved quantitative approach (QUAN), projections were corrected for scatter by use of a general spectral method and reconstructed by use of ordered-subset(s) expectation maximization, incorporating corrections for collimator response and attenuation using both a uniform attenuation map (QUANunif) and a nonuniform attenuation map (QUANnonunif). Mean SPECT activity concentration and MRI volume were estimated for 7 structures: rostral anterior cingulate gyrus, caudal anterior cingulate gyrus, posterior cingulate gyrus, hippocampus, basal forebrain, amygdala, and the banks of the superior temporal sulcus. Data were analyzed by pairwise discriminant analysis, and performance in binary group discrimination was measured by correlated receiver-operating-characteristic analysis. RESULTS: The use of QUANnonunif yielded a small but systematic improvement in discrimination accuracy for normal versus converter groups (accuracy or area under the receiver-operating-characteristic curve [Az], 0.965), normal versus questionable groups (Az, 0.973), and questionable versus converter groups (Az, 0.881) compared with the results obtained with QUANunif (Az, 0.955, 0.962, and 0.866, respectively). Discrimination performance was significantly lower (P < 0.05) with STD than with QUAN in all 3 tasks (Az with STD, 0.906, 0.878, and 0.768, respectively). MRI volume estimation led to a lower overall performance in all 3 tasks than did QUANnonunif (Az with MRI, 0.947, 0.917, and 0.872, respectively). CONCLUSION: Improved quantitative image reconstruction with accurate compensation for scatter, attenuation, and variable collimator response led to significantly better performance in discrimination tasks related to the diagnosis of prodromal AD than did standard clinical reconstruction procedures. The use of a nonuniform brain attenuation map yields a small improvement in discrimination accuracy. 相似文献
42.
43.
44.
Glucose oxidase was immobilized into photographic gelatin hardened by chromium(III) sulphate. The enzyme-gelatin mixture was coated on polyester film strips which allowed easy and simple handling during assays. The effect of gelatin and cross-linker concentrations on water content and enzymatic activity was studied. The effect of pH during immobilization and that of incubation temperature on maximum activity were examined. Enzyme leakage tests were carried out during reuse number studies. Consecutive use of strips followed by washing and resting between uses were found to affect the reuse number. A maximum immobilization of 68% was reached under optimal conditions. Mechanical stability and leakage were found to be functions of gelatin and cross-linker concentrations. Photographic gelatin was found to have many capabilities with extraordinary characteristics as a carrier on immobilization. 相似文献
45.
M El Kababri M El Khorassani L Hessissen A Kili M N Nachef M Khattab F Msefer Alaoui 《Archives de pédiatrie》2004,11(1):29-32
Venous thrombosis is rare in children. It can be either acquired or of constitutional origin. Thrombosis during non-Hodgkin lymphoma remains exceptional and is usually locally associated to the tumoral process, raising the issue of its tumoral or cruoric nature. The treatment is based on anticoagulation concomitantly to chemotherapy. We report on a 4-year-old boy admitted for mediastinal non-Hodgkin lymphoma, who developed a thrombosis of the superior vena cava associated to protein S-deficiency. The mechanism of thrombosis may have been multifactorial: associated protein S-deficiency, vascular compression, tumoral process and chemotherapy. 相似文献
46.
Abdul Rahman D El Kinge Rami A Mahfouz Ali I Shamseddine Ali T Taher 《Blood coagulation & fibrinolysis》2007,18(6):577-579
Recombinant activated factor VII has been Food and Drug Administration approved to treat hemorrhages in hemophiliac patients with inhibitors and in acquired hemophilia patients. Recombinant activated factor VII use has also been considered for the management of uncontrolled bleeding in a number of congenital and acquired hemostatic abnormalities. The myeloproliferative disorders are a group of clonal hematologic diseases where, frequently, abnormal platelet function is considered a hallmark. This is the first case report addressing the clinical benefit of off-label use of recombinant activated factor VII in an attempt to control intractable bleeding in a patient with a myeloproliferative disorder after splenectomy. 相似文献
47.
48.
49.
Ming Yang Chang Emma Parker Salwa Ibrahim John R Shortland Meguid El Nahas John L Haylor Albert C M Ong 《Nephrology, dialysis, transplantation》2006,21(8):2078-2084
BACKGROUND: Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited human kidney disease and is caused by germline mutations in PKD1 (85%) or PKD2 (15%). It has been estimated that around 1% of tubular cells give rise to cysts, and cell hyperproliferation has been noted to be a cardinal feature of cystic epithelium. Nevertheless, it is uncertain whether the increase in proliferative index observed is an early or late feature of the cystic ADPKD kidney. METHODS: Two Pkd2 mouse mutants (WS25 and WS183) have been recently generated as orthologous models of PKD2. To determine the effect of Pkd2 dosage on cell proliferation, cyst formation and renal fibrosis, we studied renal tissue from Pkd2(WS25/WS25) and Pkd2(+/-) mice by histological analysis. We also examined the proliferative index in archival nephrectomy tissue obtained from patients with ADPKD and normal controls. RESULTS: The proliferative index of non-cystic tubules in Pkd2 mutant mice as assessed by proliferating cell nuclear antigen and Ki67-positive nuclei was between 1-2%, values 5-10 times higher than control tissue. Similarly, the proliferative index of non-cystic tubules in human ADPKD kidneys was 40 times higher than corresponding controls. In Pkd2 mutant mice, significant correlations were found between the fibrosis score and the mean cyst area as well as with the proliferative index. Of significance, proliferating tubular cells were uniformly positive for polycystin-2 expression in Pkd2(+/-) kidney. CONCLUSION: These results suggest that an increase in cell proliferation is an early event preceding cyst formation and can result from haploinsufficiency at Pkd2. The possible pathogenic link between tubular cell proliferation, interstitial fibrosis and cyst formation is discussed. 相似文献
50.
A. Bezza R. Niamane B. Amine A. El Maghraoui R. Bensabbah N. Hajjaj-Hassouni 《Revue du Rhumatisme》2004,71(12):1155-1158
Objective. – To describe the clinical and radiological features of foot involvement in patients with psoriatic arthritis.Methods. – We retrospectively reviewed the medical records of patients admitted between 1972 and 1999 for psoriatic arthritis with involvement of the foot. We included all patients who had peripheral and/or axial, asymmetric, chronic inflammatory joint disease meeting or not Avila's radiological criteria for psoriatic arthritis, with or without other imaging findings suggestive of psoriatic arthritis and with or without psoriasis.Results. – Twenty-six patients were included. Inflammatory heel pain was reported by 14 patients, whereas forefoot involvement was found in only seven patients. Sausage toe was present in two patients. None of the patients had Bauer's toe (combining arthritis and psoriatic skin and/or nail changes) or psoriatic onychopachydermoperiostitis of the great toe. Radiological abnormalities were found in 20 patients. Half the patients had calcaneal changes. Osteoperiostitis of the great toe was noted in two patients and mushrooming in five.Discussion. – The features of psoriatic arthritis in Morocco seem similar to those in other countries. Hindfoot involvement was present in 53% of patients. Involvement of the forefoot was rarely recorded in the charts, suggesting missed cases because of insufficient attention to the forefoot during the physical examination and availability of anteroposterior radiographs only. Oblique views (Hirtz and Chaumet) should be obtained because they give a clearer image of the distal part of the toes, which is often difficult to analyze on anteroposterior films. 相似文献