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   422篇
  免费   14篇
  国内免费   26篇
耳鼻咽喉   1篇
儿科学   11篇
基础医学   35篇
口腔科学   9篇
临床医学   44篇
内科学   132篇
皮肤病学   2篇
神经病学   9篇
特种医学   90篇
外科学   44篇
综合类   16篇
预防医学   29篇
眼科学   6篇
药学   22篇
肿瘤学   12篇
  2023年   3篇
  2022年   5篇
  2021年   5篇
  2018年   3篇
  2015年   6篇
  2014年   5篇
  2013年   8篇
  2012年   6篇
  2011年   7篇
  2010年   11篇
  2009年   13篇
  2008年   9篇
  2007年   12篇
  2006年   28篇
  2005年   13篇
  2004年   7篇
  2003年   6篇
  2002年   4篇
  2001年   11篇
  2000年   8篇
  1999年   2篇
  1998年   16篇
  1997年   5篇
  1996年   19篇
  1995年   18篇
  1994年   16篇
  1993年   9篇
  1992年   8篇
  1991年   10篇
  1990年   12篇
  1989年   21篇
  1988年   17篇
  1987年   16篇
  1986年   15篇
  1985年   18篇
  1984年   4篇
  1983年   7篇
  1982年   6篇
  1981年   10篇
  1980年   9篇
  1979年   6篇
  1978年   5篇
  1977年   7篇
  1976年   3篇
  1975年   5篇
  1966年   3篇
  1955年   2篇
  1954年   2篇
  1950年   2篇
  1943年   2篇
排序方式: 共有462条查询结果,搜索用时 15 毫秒
91.
Benacerraf  BR; Stryker  J; Frigoletto  FD  Jr 《Radiology》1989,171(1):151-153
Certain fetal cranial abnormalities found on second-trimester sonograms can be signs of an open spina bifida. In particular, an abnormal configuration of the cerebellum, known as the banana sign, has been associated with neural tube defects. To further evaluate the usefulness of this sign, the authors compared images of the posterior fossa in 23 fetuses who had documented neural tube defects with those of 38 control fetuses who underwent sonography because of an elevated maternal serum alpha-fetoprotein level. Twenty-two of the 23 fetuses with neural tube defects had compression and anterior alignment of the cerebellar hemispheres (the banana sign), and follow-up confirmed the presence of an open neural tube defect. One fetus had a normal-appearing posterior fossa; however, the neural tube defect at birth was completely covered with skin. Four of the neural tube defects were difficult to see sonographically, and the abnormal configuration of the cerebellum, as well as the flattening of the frontal bone (lemon sign), was instrumental in suggesting the correct diagnosis. The 38 control fetuses had normal-appearing posterior fossae.  相似文献   
92.
93.
The clinical profile, malignant potential, and management of 17 children with juvenile polyposis (more than five juvenile polyps) were evaluated clinically and endoscopically. Colonoscopy and polypectomy were done three weekly until colonic clearance was achieved, and thereafter two yearly. All polyps were subjected to histological examination. Mean age was 7.7 years, with a male preponderance (3:1). Presentation was with rectal bleeding (94%), pallor (65%), stunted growth (53%), and oedema (47%), and the mean (SD) duration of symptoms was 33 (27) months. None had a positive family history or any congenital anomaly. Two children had six polyps up to the transverse colon; the rest had numerous polyps all over the colon. All children had juvenile polyps on histology and 10 (59%) had adenomatous changes (dysplasia). Total colectomy was done in six for intractable symptoms. Colon clearance was achieved in eight after an average 3.4 polypectomy sessions, and three were still on the polypectomy programme. In conclusion, juvenile polyposis is commonly associated with low grade dysplasia. Serial colonoscopic polypectomy is effective but colectomy is required for intractable symptoms and when clearance of the colon is not possible.  相似文献   
94.
Five patients with double outlet right ventricle, ventricular septal defect, pulmonary arterial hypertension and pulmonary vascular obstructive disease and three patients with complete d-transposition of the great arteries, ventricular septal defect, pulonary arterial hypertension and pulmonary vascular obstructive disease underwent an elective Mustard baffle operation. The ventricular septal defect was not closed. A large patent ductus arteriosus was divided in three patients. Seven of the eight patients are alive five to 32 months after surgery; one patient died 11 months after surgery. Cyanosis, dyspnea on exertion, and exercise limitation improved initially in all and has persisted in the survivors. In pre and postoperative hemodynamic studies in four patients, systemic arterial oxygen saturation and effective pulmonary blood flow increased from mean values of 70% to 90% and 1.7/min/m2 to 3.3 L/mon/m2, respectively. Absolute systemic and pulmonary flows, and pressures and resistances, were not significantly altered. Criteria for selection of patients with transposition of the great arteries of double outlet right ventricle who would benefit from a palliative Mustard procedure (Mustard atrial baffle without closure of the ventricular spetal defect) are: 1) severe symptoms; 2) pulmonary arteiral hypertension (75% systemic) with pulmonary vascular obstructive disease; and 3) pulmonary artieral oxygen saturation greater than systemic (ascending aorta) arterial oxygen saturation by approximately 10%.  相似文献   
95.
Early amniocentesis at 11-14 weeks gestation was evaluated in 100 consecutive patients to see how this technique compares with later amniocentesis. There were no complications as a consequence of the procedure or related pregnancy losses of chromosomally normal fetuses. Samples obtained from three (3%) patients showed insufficient cell growth; two of these patients elected a repeat procedure, which yielded a normal karyotype in each case. There were five abnormal karyotypes, one of which was a culture artifact; in the latter case, repeat amniocentesis at 15 weeks yielded a normal result. Of the 95 pregnancies with normal karyotypes, 94 were progressing normally at follow-up, and one patient elected pregnancy termination because of maternal indications. It appears that early amniocentesis may be an attractive alternative to traditional amniocentesis, in that it provides results at an earlier gestational age and may avoid certain disadvantages of chorionic villus sampling.  相似文献   
96.
Radiocontrast-induced nephropathy (RCIN) is a common cause of hospital-acquired acute renal failure and is associated with a high mortality rate. RCIN is potentially preventable, because administration of the radiocontrast agent is predictable, and a high-risk population has been identified. This multicenter, prospective, randomized, double-blind, placebo-controlled trial was performed to evaluate the efficacy of intravenous atrial natriuretic peptide (anaritide, ANP 4-28) to prevent RCIN. Patients with stable chronic renal failure (serum creatinine greater than 1.8 mg/dL or serum creatinine between 1.5 and 1.8 mg/dL with estimated creatinine clearance of < or = 65 mL/min) were assigned to receive either placebo or one of three doses of anaritide (0.01 microg/kg/min, 0.05 microg/kg/min, or 0.1 microg/kg/min) for 30 minutes before and continuing for 30 minutes after radiocontrast administration. All patients were given intravenous 0.45% saline for 12 hours before the radiocontrast procedure and continuing for 12 hours after the last dose of radiocontrast. Both ionic and nonionic radiocontrast agents were administered. RCIN was defined as either an absolute increase of serum creatinine of > or = 0.5 mg/dL or a percent increase of > or = 25% over baseline. Of the 247 patients who completed the study, 50% had diabetes mellitus. There were no statistical differences in baseline serum creatinine, change in serum creatinine, or the incidence of RCIN. The incidence of RCIN was placebo, 19%; anaritide (0.01), 23%; anaritide (0.05), 23%; anaritide (0.1), 25%. Patients with diabetes mellitus had a significantly greater incidence of RCIN: placebo, 26% versus 9%; anaritide (0.01), 33% versus 13%; anaritide (0.05), 26% versus 21%; anaritide (0.1), 39% versus 8% (diabetic v nondiabetic, P < 0.002). There was no effect in the diabetic or nondiabetic groups by anaritide on the incidence of RCIN. Comparison of the highest-risk group of patients, defined as patients with diabetes mellitus and a baseline serum creatinine > or = 1.8 mg/dL, with the lowest-risk group, defined as patients without diabetes mellitus and a baseline serum creatinine of 1.8 mg/dL or less, did not show a beneficial effect of anaritide administration. In conclusion, administration of intravenous anaritide before and during a radiocontrast study did not reduce the incidence of RCIN in patients with preexisting chronic renal failure, with or without diabetes mellitus.  相似文献   
97.
Fibroblast growth factor 14 (FGF14) belongs to the intracellular FGF homologous factor subfamily of FGF proteins (iFGFs) that are not secreted and do not activate tyrosine kinase receptors. The iFGFs, however, have been shown to interact with the pore-forming (alpha) subunits of voltage-gated Na+ (Na(v)) channels. The neurological phenotypes seen in Fgf14-/- mice and the identification of an FGF14 missense mutation (FGF14(F145S)) in a Dutch family presenting with cognitive impairment and spinocerebellar ataxia suggest links between FGF14 and neuronal functioning. Here, we demonstrate that the expression of FGF14(F145S) reduces Na(v) alpha subunit expression at the axon initial segment, attenuates Na(v) channel currents, and reduces the excitability of hippocampal neurons. In addition, and in contrast with wild-type FGF14, FGF14(F145S) does not interact directly with Na(v) channel alpha subunits. Rather, FGF14(F145S) associates with wild-type FGF14 and disrupts the interaction between wild-type FGF14 and Na(v) alpha subunits, suggesting that the mutant FGF14(F145S) protein acts as a dominant negative, interfering with the interaction between wild-type FGF14 and Na(v) channel alpha subunits and altering neuronal excitability.  相似文献   
98.
99.
B cell lymphoproliferative disorders (BLPD) developed in eight patients following bone marrow transplantation (BMT) for leukemia (five patients) or immunodeficiency (three patients). Recipients of T depleted marrow from a mismatched donor were at particularly high risk of this complication. Six of 25 (24%) recipients of mismatched T depleted bone marrow developed BLPD. In contrast, none of 47 matched T depleted transplants, one of ten (10%) who received non-depleted marrow from an unrelated donor, and only one of 424 matched non-depleted transplants were associated with BLPD. Epstein-Barr virus (EBV) specific serology and DNA hybridization studies demonstrating five to 50 copies of EBV genome/cell in involved tissues implicate this virus as an associated etiologic agent. Restriction fragment length polymorphism (RFLP) and cytogenetic analysis of involved tissue demonstrated donor origin (five of seven) or host origin (two of seven). Histologic appearance was similar to EBV-induced polymorphic B cell proliferations described following solid organ transplantation, or which occur de novo in primary immunodeficiency. Six of seven patients with adequate tissue available for study were found to have monoclonal proliferations by: in situ immunofluorescence (six of seven), and/or immunoglobulin gene rearrangement, (four of six). Cytogenetic analysis of involved tissues from four patients showed a normal karyotype, whereas two had multiple clonal chromosomal abnormalities. Seven patients died despite aggressive attempts at therapy with combinations of antiviral, immunologic, and chemotherapeutic agents.  相似文献   
100.
Blazar  BR; Taylor  PA; Smith  S; Vallera  DA 《Blood》1995,85(3):842-851
Studies in mice and humans have indicated that the predominance of interleukin-4 (IL-4)- and IL-10-producing T-helper type 2 (Th2) cells may serve to downregulate acute graft-versus-host disease (GVHD) reactions, whereas IL-2-producing Th1 cells have been implicated in facilitating acute GVHD. We explored the possibility that the in vivo infusion of IL-10 would inhibit acute GVHD induced by fully allogeneic donor grafts. Unexpectedly, IL-10 infusions resulted in a dose- dependent increase in GVHD-induced mortality. The acceleration of lethal GVHD by IL-10 occurred in irradiated recipients of T-cell- depleted bone marrow (BM) plus 5, 15, or 25 x 10(6) splenocytes but did not influence the post-BM transplantation (post-BMT) survival rate of recipients of BM without splenocytes, suggesting that the IL-10 effects were not due to toxicity. Antimurine IL-10-neutralizing monoclonal antibody injections, administered to diminish endogenous IL-10, reduced GVHD-associated mortality and improved the clinical appearance of the recipients. For BM graft rejection studies, IL-10 was infused into sublethally irradiated recipients of anti-Thy 1.2 + C' T-cell-depleted, fully allogeneic BM grafts. In a short-term (day 7) in vivo assay, IL- 10 infusions significantly inhibited allogeneic (but not syngeneic) BM proliferation in vivo, indicative of increased graft rejection. In long- term chimerism experiments, IL-10 infusions caused a significant increase in early post-BMT mortality caused by a profound anemia typically associated with graft rejection and aplasia. A slightly higher irradiation dose (650 cGy v 600 cGy) eliminated the anemia but did not reverse the graft rejection process associated with IL-10 administration. We conclude that the in vivo infusion of exogenous IL- 10 in recipients of fully allogeneic donor grafts results in accelerated GVHD and graft rejection in the strain combinations tested to date.  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