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   2511篇
  免费   230篇
  国内免费   6篇
耳鼻咽喉   53篇
儿科学   68篇
妇产科学   41篇
基础医学   368篇
口腔科学   57篇
临床医学   308篇
内科学   537篇
皮肤病学   31篇
神经病学   245篇
特种医学   119篇
外科学   399篇
综合类   25篇
一般理论   1篇
预防医学   147篇
眼科学   111篇
药学   158篇
中国医学   3篇
肿瘤学   76篇
  2022年   19篇
  2021年   48篇
  2019年   47篇
  2018年   38篇
  2017年   47篇
  2016年   49篇
  2015年   38篇
  2014年   54篇
  2013年   62篇
  2012年   110篇
  2011年   114篇
  2010年   69篇
  2009年   56篇
  2008年   98篇
  2007年   109篇
  2006年   121篇
  2005年   118篇
  2004年   120篇
  2003年   108篇
  2002年   112篇
  2001年   98篇
  2000年   82篇
  1999年   71篇
  1998年   44篇
  1997年   28篇
  1996年   36篇
  1995年   20篇
  1994年   22篇
  1993年   19篇
  1992年   64篇
  1991年   52篇
  1990年   46篇
  1989年   45篇
  1988年   49篇
  1987年   40篇
  1986年   41篇
  1985年   38篇
  1984年   35篇
  1983年   34篇
  1982年   27篇
  1981年   14篇
  1980年   20篇
  1979年   23篇
  1978年   17篇
  1974年   17篇
  1973年   25篇
  1972年   15篇
  1971年   24篇
  1969年   16篇
  1968年   14篇
排序方式: 共有2747条查询结果,搜索用时 33 毫秒
11.
OBJECTIVE: Chronic pancreatitis (CP) is a chronic condition associated with pancreatic fibrosis. A small subgroup of patients with CP develop enlargement of the head of the pancreas (EHP). This study examined some of the mechanisms that may lead to the development of EHP. SUMMARY BACKGROUND: The c-erb B-2 protooncogene encodes a 185-kDa transmembrane growth factor receptor (p185) that regulates cell growth and differentiation. METHODS: The authors analyzed c-erb B-2 expression in samples obtained from the head of the pancreas from 26 patients with CP (5 women, 21 men) using immunohistochemical and molecular technique. A diagnosis of CP with EHP was made when the vertical pancreatic head diameter was greater than 4 cm (14 patients), as determined by contrast-enhanced computed axial tomography scan. Pancreatic tissues from 15 healthy organ donors served as control subjects. RESULTS: In all patients without EHP and in the healthy control subjects, p185 immunoreactivity was present at low levels. In contrast, strong p185 immunoreactivity was observed in acinar and ductal cells in all patients with EHP. By in situ hybridization, c-erb B-2 messenger ribonucleic acid (mRNA) grains were expressed at high levels in patients with CP with EHP in both ductal and acinar cells. Northern blot analysis demonstrated a 4.5-fold increase (p < 0.001) in c-erb B-2 mRNA levels in patients with EHP compared with patients without EHP and healthy control subjects. Southern blot analysis did not reveal c-erb B-2 gene amplification or rearrangement. CONCLUSIONS: These findings indicate the c-erb B-2 is not overexpressed in most patients with CP. However, its overexpression in patients with CP with EHP suggest that c-erb B-2 may contribute to the pathophysiologic processes that lead to pancreatic head enlargement.  相似文献   
12.
13.
SYNOPSIS
Few controlled studies have examined the effectiveness of relaxation therapy for the treatment of adolescent headaches. In this study, ten chronic headache sufferers (migraine or muscle contraction), ranging in age from 12 to 17 years (M = 13.5 SD = 1.3), were sequentially assigned to either a relaxation therapy or waiting-list control group. Following treatment, subjects in the treatment group demonstrated significantly lower Headache Index scores than subjects in the control group (U = 0, p £ .004). Group differences in Headache Free Days, Peak Headache Rating, and Medication Index scores were not significant; differences in Medication Index scores approached significance at U = 3, p £ .03. Objective compliance to treatment data indicated subjects overreported their actual practice time, on average, by 70%. Results and implications for future research are discussed.  相似文献   
14.
15.
The clinical and virologic efficacy of ganciclovir (9-[1,3-dihydroxy-2-propoxymethyl]guanine) in the treatment of severe CMV infections in solid organ transplant recipients was investigated. Twelve patients (9 liver and 3 kidney transplant recipients) with CMV retinitis, esophagitis, hepatitis, or pneumonia received ganciclovir at a dose of 0.75-7.5 mg/kg/day for 10-30 days (mean duration 17 days). Clinical stabilization or improvement occurred in 8 patients (67%). Serial liver biopsies in 6 liver allograft recipients with CMV hepatitis demonstrated substantial histologic improvement on treatment. Of 6 patients with CMV pneumonia, 4 (67%) recovered and survived. Cultures of blood and other sites became negative in 9 patients (75%). Three patients (25%) had recurrent viral shedding after treatment, but none of these relapsed with invasive infections. Mild neutropenia was the only side effect encountered but was frequent (67%). The overall survival rate was 50%. Ganciclovir is effective in reducing CMV shedding in solid organ transplant recipients and is well tolerated. Our experience suggests a clinical benefit as well in patients with severe, invasive CMV disease. Relapse, in contrast to patients with the acquired immunodeficiency syndrome, is infrequent.  相似文献   
16.
Arteriovenous malformation of the uterus is a rare uterine abnormality. This entity is generally associated with the presence of molar disease, choriocarcinoma and uterine surgery, but may be congenitally acquired. The presence of an arteriovenous malformation generally leads to unexplained profuse uterine bleeding. The diagnosis of this entity has traditionally been made by arteriography, and the treatment is usually hysterectomy. We present a patient with an arteriovenous malformation of the uterus whose prior delivery was by Cesarean section. The patient experienced episodes of heavy vaginal bleeding in the first month following the procedure of suction curettage for a first-trimester pregnancy loss. Chorionic villus sampling performed prior to the procedure showed a chromosomally normal fetus. The diagnosis of an arteriovenous malformation was made by color Doppler velocimetry and confirmed with arteriography. The patient desired to maintain her fertility. Interventional radiological techniques were successfully utilized to obliterate the arteriovenous malformation with the use of polyvinyl alcohol particles (250 micro m) and gelfoam. Discussion includes the presenting signs and symptoms along with the method of both diagnosis and conservative management.  相似文献   
17.
The 2-deoxy-D-[1-14C]glucose ([14C]DG) method was used to examine the effects of the relatively selective sigma ligand 1,3-di-o-tolylguanidine (DTG) on cerebral metabolism in freely moving rats. Each animal received an i.p. injection of DTG (0.2, 1, or 5 mg/kg) or normal saline 20 min prior to the infusion of [14C]DG. DTG induced dose-dependent changes in local cerebral glucose utilization (LCGU) in several motor and limbic structures. Most structures showed increases in LCGU, with a maximum effect at 1 mg/kg. The most profound increases in LCGU were observed in brain regions that are rich in sigma receptors. These included cerebellar and related nuclei (interpositus, lateral and medial cerebellar n., vestibular n., olivary n.), ambiguus n., superior colliculus (superior layers), hippocampus (CA2, CA3, DG), n. basalis of Meynert interpeduncular n., and the substantia nigra pars compacta and pars reticulata. No significant decreases in glucose utilization were observed at any dose. Although the areas affected by DTG are similar to those previously reported for other sigma ligands, future studies employing a range of doses for additional selective sigma ligands must be carried out in order to confirm whether these changes in LCGU were sigma-mediated.  相似文献   
18.
The approximation of logarithmic difference spectra between the reflectance of the normal fundus and the fundus reflectance in different stages of glaucoma is demonstrated by a model. The influences of fundus pigments like oxihemoglobin, melanin, xanthophyll and rhodopsin as well as the intensity and the exponent of the scattered light are optimized. Glaucomatous alterations in the extinction of these pigments and of the scattering parameters are different in the macula, in the papillo-macular bundle and in the parapapillary region temporal to the optic disc. A lack of oxihemoglobin only in the papillo-macular bundle in first relative losses in the visual field function points to a damaged microcirculation in early POAG. In progressive glaucoma the extinction spectrum of xanthophyll is detectable in the papillo-macular bundle. A decreased intensity of the scattered light and an altered scattering exponent are suggestive of a damage in the nerve fiber layer at early stages of glaucoma.  相似文献   
19.
Iniencephaly is a rare, lethal, axial dysraphic malformation complex diagnosed on the basis of three cardinal features: deficiency of the occipital bone, cervicothoracic spinal retroflexion, and rachischisis. The majority of the patients also have various associated viscerae malformations. An iniencephalic female fetus delivered at 355/7 weeks of gestation revealed severe anomalies of the central nervous system and the spine: the cerebellar vermis was hypoplastic, the medulla oblongata was flattened and broadened, and the cervical canal was widely patent dorsally. The thoracolumbar spinal cord had a duplicated central canal and lacked a dorsal fissure, representing a minor degree of diastematomyelia. The cervicothoracic spine showed severe bony anomalies including aplasia and fusion of vertebral bodies.  相似文献   
20.
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