首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   15319篇
  免费   1386篇
  国内免费   24篇
耳鼻咽喉   162篇
儿科学   557篇
妇产科学   410篇
基础医学   2211篇
口腔科学   273篇
临床医学   1906篇
内科学   2878篇
皮肤病学   194篇
神经病学   1448篇
特种医学   367篇
外科学   1955篇
综合类   199篇
一般理论   17篇
预防医学   1823篇
眼科学   245篇
药学   885篇
中国医学   9篇
肿瘤学   1190篇
  2023年   127篇
  2022年   180篇
  2021年   428篇
  2020年   268篇
  2019年   416篇
  2018年   480篇
  2017年   330篇
  2016年   353篇
  2015年   407篇
  2014年   530篇
  2013年   745篇
  2012年   1052篇
  2011年   1070篇
  2010年   560篇
  2009年   471篇
  2008年   832篇
  2007年   854篇
  2006年   775篇
  2005年   750篇
  2004年   604篇
  2003年   584篇
  2002年   524篇
  2001年   298篇
  2000年   340篇
  1999年   276篇
  1998年   160篇
  1997年   129篇
  1996年   111篇
  1995年   105篇
  1994年   101篇
  1993年   102篇
  1992年   210篇
  1991年   205篇
  1990年   163篇
  1989年   181篇
  1988年   171篇
  1987年   188篇
  1986年   148篇
  1985年   162篇
  1984年   119篇
  1983年   87篇
  1982年   67篇
  1981年   79篇
  1980年   66篇
  1979年   102篇
  1978年   93篇
  1976年   64篇
  1973年   66篇
  1972年   60篇
  1971年   62篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
171.
Journal of Gastrointestinal Surgery - Pylephlebitis, or suppurative thrombophlebitis of the portal mesenteric venous system occurring in the setting of abdominal inflammatory processes, is a rare...  相似文献   
172.
It is estimated that 1.7% of orthotopic liver transplant recipients will develop abdominal aortic aneurysms (AAAs) after transplantation. It has been observed that these aneurysms expand faster in transplant recipients; therefore, aggressive surveillance for AAAs in transplant recipients is required. Endovascular aneurysm repair is rapidly becoming the standard of care, especially in patients with previous abdominal surgery and other significant comorbidities. This article describes our experience with AAAs in orthotopic liver transplant recipients treated successfully by endovascular stent graft repair.  相似文献   
173.
BACKGROUND: Diabetic nephropathy is the most frequent cause of end-stage renal disease in the Western world. Dietary intake, including protein amount and type, seems to affect the progression of renal disease. This pilot study tested the hypothesis that substituting soy protein for animal protein in the diets of diabetics would help correct glomerular hyperfiltration. METHODS: Twelve young adults (aged 29.9 +/- 2.4 years) with type 1 diabetes mellitus (duration of diabetes 15.1 +/- 2.3 years) and hyperfiltration (glomerular filtration rate, GFR > 120 ml/min/1.73 m2) completed a crossover, dietary intervention trial. After a four-week assessment of baseline characteristics and dietary habits, subjects were assigned to either a control or soy diet for eight weeks after which each subject was crossed over to the alternative diet for another eight-week period. RESULTS: Mean GFR was significantly reduced (p < 0.02) after eight weeks on the soy diet (143 +/- 7.4 ml/min/1.73 m2) compared with baseline (159 +/- 7.7 ml/min/ 1.73 m2) and control diets (161 +/- 10.0 ml/min/1.73 m2). Urinary excretion of the soy isoflavones was significantly higher (p < 0.01) at the end of the soy diet (genistein 1,014.6 +/- 274.1 nmol/h, daidzein 2,645.1 +/- 989.6 nmol/h) compared with baseline (genistein 53.7 +/- 31.1 nmol/h, daidzein 151.1 +/- 74.1 nmol/h) and control diets (genistein 41.1 +/- 13.3 nmol/h, daidzein 127.5 +/- 54.0 nmol/h). The soy diet significantly reduced total and LDL cholesterol by 7% and 9%, respectively. CONCLUSIONS: Implementation of a soy-based diet appears to reduce the GFR and total and LDL cholesterol of young adults with type 1 diabetes and glomerular hyperfiltration, thus affecting positively their clinical profile.  相似文献   
174.
Renal transplant recipients suffering from persistent diarrhea have been repeatedly reported to have increased tacrolimus (Tac) trough levels. This study aimed to explore this phenomenon in detail in 15 renal transplant recipients with diarrhea, whose immunosuppression consisted of corticosteroids, mofetil mycophenolate and Tac. Both hepatic and intestinal CYP3A4 and PGP activity, important determinants of Tac bioavailability, were assessed, together with global CYP activity and investigations for gastrointestinal infection, function and morphology. Global CYP, CYP3A4, PGP and trough/dose levels of Tac were compared with diarrhea-free controls. In addition, a pharmacokinetic study of Tac was performed in 11 patients affected by diarrhea versus 9 controls. As expected, diarrhea was associated with increased Tac trough levels. An even stronger, significant increase of dose-normalized Tac levels was observed between 90 and 360 min after Tac intake. Time to peak concentration and drug half-life, however, were not altered. In addition, a concomitant decrease (+/-50%) of intestinal PGP activity was noticed in patients with diarrhea. For global CYP, CYP3A4 and hepatic PGP activity no such differences were noted. This pattern was not influenced by the specific cause of diarrhea. These data strongly suggest that persistent diarrhea is associated with an increased oral bioavailability of Tac.  相似文献   
175.
Extrahepatic portal vein thrombosis (EHPVT) may occur in children or adults and usually comes to clinical attention due to complications of portal hypertension such as variceal hemorrhage. A variety of standard surgical techniques exist to manage these patients, but when these fail surgical options are limited. We describe two novel portosystemic shunts that utilize the gonadal vein as an autologous conduit. Four patients were evaluated for EHPVT with variceal bleeding. None of the patients were candidates for a standard splenorenal shunt due to prior surgical procedures. The first patient underwent a left mesogonadal shunt and the remaining 3 patients underwent a right mesogonadal shunt. Postoperative ultrasound or computed tomography (CT) scan confirmed early patency of the shunt in each patient. There have been no further episodes of variceal hemorrhage with follow-up of 3.5 years in the child who underwent the left mesogonadal shunt, and 17, 19, and 20 months in the patients who underwent the right mesogonadal shunt. Three of the 4 shunts remain patent. One shunt thrombosis occurred in a patient homozygous for the Factor V Leiden mutation despite anticoagulation with coumadin. This is the first report of the successful use of the gonadal vein as an in situ conduit for constructing a portosystemic shunt. In conclusion, the right and left mesogonadal shunts may be useful as salvage operations for patients with EHPVT who have failed standard surgical shunt procedures.  相似文献   
176.
The Personalized Health Care Workgroup of the American Health Information Community was formed to determine what is needed to promote standard reporting and incorporation of medical genetic/genomic tests and family health history data in electronic health records. The Workgroup has examined and clarified a range of issues related to this information, including interoperability standards and requirements for confidentiality, privacy, and security, in the course of developing recommendations to facilitate its capture, storage, transmission, and use in clinical decision support. The Workgroup is one of several appointed by the American Health Information Community to study high-priority issues related to the implementation of interoperable electronic health records in the United States. It is also a component of the U.S. Department of Health and Human Services'' Personalized Health Care Initiative, which is designed to create a foundation upon which information technology that supports personalized, predictive, and pre-emptive health care can be built.  相似文献   
177.
Although CD8(+) T cells initially suppress human immunodeficiency virus (HIV) replication, cytotoxic T-cell precursor frequencies eventually decline and fail to prevent disease progression. In a longitudinal study including 16 individuals infected with HIV-1, we studied both the number and function of HIV-specific CD8(+) T cells by comparing HLA-peptide tetramer staining and peptide-induced interferon-gamma (IFN-gamma) production. Numbers of IFN-gamma-producing T cells declined during progression to acquired immunodeficiency syndrome (AIDS), whereas the number of tetramer+ T cells in many individuals persisted at high frequencies. Loss of IFN-gamma-producing T cells correlated with declining CD4(+) T-cell counts, consistent with the need of CD4(+) T-cell help in maintaining adequate CD8(+) T-cell function. These data indicate that the loss of HIV-specific CD8(+) T-cell activity is not due to physical depletion, but is mainly due to progressively impaired function of HIV-specific CD8(+) T cells.  相似文献   
178.
Kim DW  Egan KK  O'Grady K  Toriumi DM 《The Laryngoscope》2005,115(8):1451-1453
OBJECTIVE/HYPOTHESIS: Nasal septal perforation is a common complication following surgery involving the nasal septum. Septoplasty, septorhinoplasty, and submucosal resection may result in the inadvertent resection of perichondrium, which may predispose the patient to septal perforations. STUDY DESIGN: Controlled human cadaver study testing the biomechanical strength of the constituent layers of nasal septal lining. METHODS: Uniform samples of nasal septal mucosa, perichondrium, and a composite of both layers were obtained from five fresh human cadavers. The mechanical tensile strength of these layers was evaluated and compared with the Instron 4301 Mechanical Testing System (Canton, MA). RESULTS: Mixed-effects regression analysis demonstrated a significant difference in the tensile strength of the three groups (mean values +/- SD: mucosa, 662 +/- 308 g; perichondrium, 1370 +/- 798 g; composite, 2340 +/- 1252 g). All three pairwise comparisons among the three groups showed a significant difference in tensile strength. CONCLUSION: The perichondrial layer imparts the majority of the biomechanical strength to septal lining. Lining flaps containing both perichondrium and mucosa are stronger than flaps with either perichondrium or mucosa alone. Dissection in the subperichondrial plane during septal surgery provides a stronger septal flap and may prevent the development of nasal septal perforation during nasal surgery.  相似文献   
179.
Background: Eosinophilic cellulitis is a polymorphous, chronic disease characterized by eosinophil infiltration and granulomatous inflammation. Objective: Our purpose was to describe the clinical, histologic, and immunohistologic findings in three family members who have had eosinophilic cellulitis since childhood associated with mental retardation and abnormal body habitus. Methods: Family members were evaluated. Multiple skin biopsy specimens were obtained and examined after hematoxylin-and-eosin staining, by immunofluorescence and by electron microscopy. Blood specimens were analyzed by immunoassays for eosinophil granule proteins and eosinophil active cytokines. Results: Three short-statured, mentally retarded family members with abnormal body habitus in at least two generations had recurrent eosinophilic cellulitis. Peripheral blood and bone marrow eosinophilia was present. Plasma eosinophil granule major basic protein and eosinophil-derived neurotoxin levels were elevated with normal plasma eosinophil cationic protein levels. Eosinophil survival in culture was increased by patients’ plasma and was blocked with monoclonal interleukin-5 antibody. The level of plasma interleukin-5 was elevated. Lesional skin biopsy specimens showed massive staining for three eosinophil granule proteins. Electron microscopy showed eosinophil disruption. Conclusion: Eosinophilic cellulitis, mental retardation, and abnormal body habitus were likely inherited as a dominant syndrome in this family in which eosinophil involvement was striking. (J Am Acad Dermatol 1998;38:919-28.)  相似文献   
180.
1. Multiple microelectrode maps of the hand representation within and across the borders of cortical area 3b were obtained before, immediately after, or several weeks after a period of behaviorally controlled hand use. Owl monkeys were conditioned in a task that produced cutaneous stimulation of a limited sector of skin on the distal phalanges of one or more fingers. 2. Analysis of microelectrode mapping experiment data revealed that 1) stimulated skin surfaces were represented over expanded cortical areas. 2) Most of the cutaneous receptive fields recorded within these expanded cortical representational zones were unusually small. 3) The internal topography of representation of the stimulated and immediately surrounding skin surfaces differed greatly from that recorded in control experiments. Representational discontinuities emerged in this map region, and "hypercolumn" distances in this map sector were grossly abnormal. 4) Borders between the representations of individual digits and digit segments commonly shifted. 5) The functionally defined rostral border of area 3b shifted farther rostralward, manifesting either an expansion of the cutaneous area 3b fingertip representation into cortical field 3a or an emergence of a cutaneous input zone in the caudal aspect of this normally predominantly deep-receptor representational field. 6) Significant lateralward translocations of the borders between the representations of the hand and face were recorded in all cases. 7) The absolute locations--and in some cases the areas or magnifications--of representations of many skin surfaces not directly involved in the trained behavior also changed significantly. However, the most striking areal, positional, and topographic changes were related to the representations of the behaviorally stimulated skin in every studied monkey. 3. These experiments demonstrate that functional cortical remodeling of the S1 koniocortical field, area 3b, results from behavioral manipulations in normal adult owl monkeys. We hypothesize that these studies manifest operation of the basic adaptive cortical process(es) underlying cortical contributions to perception and learning.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号