首页 | 官方网站   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   6998篇
  免费   466篇
  国内免费   20篇
医药卫生   7484篇
  2023年   34篇
  2022年   61篇
  2021年   129篇
  2020年   93篇
  2019年   124篇
  2018年   143篇
  2017年   117篇
  2016年   131篇
  2015年   164篇
  2014年   189篇
  2013年   268篇
  2012年   465篇
  2011年   450篇
  2010年   255篇
  2009年   267篇
  2008年   430篇
  2007年   454篇
  2006年   509篇
  2005年   439篇
  2004年   439篇
  2003年   396篇
  2002年   388篇
  2001年   138篇
  2000年   108篇
  1999年   89篇
  1998年   103篇
  1997年   81篇
  1996年   72篇
  1995年   80篇
  1994年   49篇
  1993年   58篇
  1992年   42篇
  1991年   47篇
  1990年   47篇
  1989年   36篇
  1988年   35篇
  1987年   33篇
  1986年   47篇
  1985年   51篇
  1984年   32篇
  1983年   38篇
  1982年   26篇
  1981年   21篇
  1980年   28篇
  1979年   26篇
  1978年   21篇
  1976年   13篇
  1975年   14篇
  1974年   21篇
  1973年   18篇
排序方式: 共有7484条查询结果,搜索用时 0 毫秒
61.
62.
Summary Alcohol induced perivenular fibrosis of terminal hepatic veins (THV) is claimed to be a precursor lesion leading to fibrosis development in man and baboon. The nature and significance of the THV lesions found in four baboons chronically fed with alcohol were studied in liver biopsies obtained during a three year period. The surface of THV wall and the number of mesenchymal cells were assessed with a semi-automatic image analyser. Histologically, THV were characterized as (a) phlebitic, in the presence of an inflammatory cell infiltrate involving the venous wall; (b) oedematous, when the connective tissue of the THV wall was disrupted or dissociated and (c) fibrotic, when perivenular scarring appeared as an increased rim. These lesions were present simultaneously and their intensity and distribution were independent of the duration of alcohol intoxication. Morphometric data obtained from these THV confirmed the thickening of the THV wall (WS/IS in: oedematous 1.05±0.36; phlebitic 1.65±1.04; fibrotic 1.47±0.36); and revealed an increased number of mesenchymal cells in fibrotic (439 m2/cell;p<0.01) and in phlebitic THV (510 m2/cell;p<0.05). A constant relationship was found between phlebitis and the presence of inflammatory infiltrate within the hepatic acini. Fibrotic THV was a less frequent finding and the lesion disappeared in the sequential biopsies of one of the baboons. In conclusion, THV lesions were heterogeneous and the collagen deposition in the THV wall was potentially reversible during the three year alcohol intoxication period, regardless the inflammatory reaction and, thus, did not indicate early irreversible hapatic fibrosis.Dr. Porto was supported by a fellowship from MEC-CAPES, Brazil. A grant for morphometric equipment was obtained from the Fondation pour la Recherche Médicale and from the Societé d'Hépatologie Expérimentale, 77 rue Pasteur, Lyon, France  相似文献   
63.
It has been suggested that the renal functional reserve (RFR) defined by the rise in glomerular filtration rate (GFR) after a protein load could disappear in patients with severe nephron loss but with a normal GFR. This study compared, in 17 children, inulin clearance (C in) measured by the plasma inulin plateau at the end of two 14-day randomized periods differing in protein intake: 100% (low protein, LP), or 200% (high protein, HP) of recommended dictary allowances (RDA). Diets were aimed at maintaining food habits and energy intake. Compliance was assessed by records of the last 3–4 days, an interview with the dietician and by urinary nitrogen measurements. Mean actual protein intake was 109% (56%–139%) RDA for the LP period and 220% (163%–319%) RDA for the HP period.C in did not change in 14 children with GFR below (n=7) or within (n=7) the normal range.C in was higher in the HP period than in the LP period (+32, 50, 63%) in 3 children who had a 50% (single kidneys) or a 25% (sclerosed glomeruli) nephron loss. Non-responding children had a GFR below 105 ml/min per 1.73 m2. Nephron loss (70% sclerosed glomeruli) was estimated in only 1 child with no RFR. The results suggest that GFR measurement after prolonged dietary stimulation could help in evaluating the severity of nephron loss in children with normal or borderline GFR. The prognostic value of this test has to be confirmed by long-term follow-up.  相似文献   
64.
仁术健胃颗粒逆转胃癌前期病变的临床研究   总被引:11,自引:1,他引:10  
目的观察仁术健胃颗粒对胃癌前病变的逆转作用。方法将120例符合诊断标准的胃癌前期病变患者,随机分为仁术健胃颗粒治疗组80例和胃复春对照组40例进行临床疗效观察。结果①综合疗效:治疗组总有效率为91.25%,对照组为75.00%,经统计学处理,差异有显著性(P〈0.05);②治疗组胃镜及对萎缩、肠化、异型增生的疗效分别为71.25%、77.50%、79.49%、88.46%,对照组为52.50%、6  相似文献   
65.
Background: Occult choroidal neovascularization (CNV), poorly defined on fluorescein angiography, is present in the majority of patients with exudative complications of age-related macular degeneration. For patients who present with this type of subfoveal CNV but who have useful visual acuity, no form of treatment is of proven benefit. Accordingly, a pilot randomized trial of indirect laser treatment was performed. The rationale of this treatment was to inhibit the CNV through laser-induced effects on the retinal pigment epithelium. Methods: Patients with occult subfoveal CNV without retinal pigment epithelial detachment and with visual acuity of 20/200 or better were randomized to treatment or control groups. A grid of laser burns was applied to the macula beyond the area of serous retinal detachment and of angiographically defined occult CNV Results: After an average follow-up of 38 months, there was no difference in mean final visual acuity (0.12 treated, 0.14 control) or clinical outcome between treated and untreated groups. Fluorescein angiography showed gradual enlargement in the occult CNV in 58% of eyes in both groups. A decrease in visual acuity to worse than 20/200 (54% of treated, 50% of control eyes) was associated with ingrowth of well-delineated CNV (6 treated, 7 control eyes) or progression to a fibroglial or atrophic scar (11 treated, 8 control eyes). Conclusions: No benefit was demonstrated for scatter photocoagulation of the macula in patients with age-related macular degeneration and occult subfoveal CNV with initially good visual acuity. There were, however, no complications related to treatment.  相似文献   
66.
Emotion perception and perspective-taking skills were examined among women with or without the fragile X gene. The performance of 56 control women was compared to the performance of 46 women who were carriers of the fragile X gene. Twenty-seven of the carrier women had 0–1% cytogenetic expression and did not appear affected by the gene, whereas the remaining 19 women had 2% cytogenetic expression and did appear affected by the gene. The emotion perception task employed was one for which deficits have been reported among individuals with autism. The results show that performance on this emotion-perception test and the perspective-taking measure was significantly related to full-scale IQ scores, but not to fragile X group status when effects of IQ were removed. Thus the results do not support the hypothesis that perspective-taking or emotion perception deficits are a component of the fragile X phenotype in females and represent an important differentiation between fragile X and autism.This research was supported by NIMH Grant MCJOOO252 U.S. Department of Health and Human Services, Bureau of Maternal and Child Health; and by grant MH45916 U.S. National Institutes of Health (NIMH). Randi J. Hagerman and Michele M. M. Mazzocco received additional support from a grant from Joslins Department Store, Denver, Colorado. Hagerman received support from grant RR-69 from the General Clinical Research Program, National Center for Research Resources, National Institutes of Health. Bruce F. Pennington was supported by an RSDA (MH0419) and MERIT award (MH38870) from NIMH, as well as by an NICHD Center Grant (HD27802). The authors thank all the women who participated in the study and Dennis Lucky and Barrett Jeffers from the Kempe Research Center at The Children's Hospital.  相似文献   
67.
68.
4-(Benzodioxan-5-yl)1-(indan-2-yl)piperazine (S15535) is a highly selective ligand at 5-HT(1A) receptors. The present study compared its autoradiographic labelling of rat brain sections with its functional actions, visualised by guanylyl-5'-[gamma-thio]-triphosphate ([35S]GTPgammaS) autoradiography, which affords a measure of G-protein activation. [3H]S15535 binding was highest in hippocampus, frontal cortex, entorhinal cortex, lateral septum, interpeduncular nucleus and dorsal raphe, consistent with specific labelling of 5-HT(1A) receptors. In functional studies, S15535 (10 microM) did not markedly stimulate G-protein activation in any brain region, but abolished the activation induced by the selective 5-HT(1A) agonist, (+)-8-hydroxy-dipropyl-aminotetralin ((+)-8-OH-DPAT, 1 microM), in structures enriched in [3H]S15535 labelling. S15535 did not block 5-HT-stimulated activation in caudate nucleus or substantia nigra, regions where (+)-8-OH-DPAT was ineffective and [3H]S15535 binding was absent. Interestingly, S15535 attenuated (+)-8-OH-DPAT and 5-HT-stimulated G-protein activation in dorsal raphe, a region in which S15535 is known to exhibit agonist properties in vivo [Lejeune, F., Millan, M.J., 1998. Induction of burst firing in ventral tegmental area dopaminergic neurons by activation of serotonin (5-HT)(1A) receptors: WAY100,635-reversible actions of the highly selective ligands, flesinoxan and S15535. Synapse 30, 172-180.].The present data show that (i) [3H]S15535 labels pre- and post-synaptic populations of 5-HT(1A) sites in rat brain sections, (ii) S15535 exhibits antagonist properties at post-synaptic 5-HT(1A) receptors in corticolimbic regions, and (iii) S15535 also attenuates agonist-stimulated G-protein activation at raphe-localised 5-HT(1A) receptors.  相似文献   
69.
A 7-year-old child presented with a severe form of Takayasu's arteritis, with two consecutive episodes involving the right testis and then the left kidney 6 months later. The renal artery obstruction was accompanied by severe hypertension. An aortography showed a complete obstruction of the left renal artery and a narrowing of the right subclavian artery. Plasma renin activity was high. Serum immunoglobulins were within the normal range, except for an increase in IgE (880 /l). Despite 4 months', treatment with antihypertensive drugs, prednisone, cyclophosphamide, and anticoagulant, the blood pressure never returned to normal and the left renal function remained completely absent. A nephrectomy was performed which immediately normalized plasma renin activity and blood pressure. The child was subsequently treated with alternateday prednisone for 3 months, alternating with 3 months of cyclophosphamide or, later, azathioprine. Persantine (dipyridamole) and acetylsalicylic acid were administered continuously. The right radial pulse returned to normal within 2 years. An 8-year follow-up failed to detect any new episode of arteritis. The right kidney showed signs of compensatory hypertrophy. Finally, a recent arteriography demonstrated not only a normal right renal artery blood flow but almost total disappearance of the right subclavian artery obstruction. However, the IgE remained abnormally high (2,023 g/l).  相似文献   
70.
Intracellular distribution of carbonic anhydrase in the rat kidney   总被引:16,自引:0,他引:16  
The rat kidney was studied by light and electron microscope after it was histochemically stained for carbonic anhydrase activity. Glomeruli and Bowman's capsule were inactive. Convoluted proximal tubules showed intense activity at the brush border and the basolateral membranes. Cytoplasmic activity also was found. Straight proximal tubules had considerable enzyme activity at basolateral membranes but only low activity at the brush border and in the cytoplasm. In nephrons with long loops, the descending thin limb contained cytoplasmic enzyme activity, whereas the ascending thin limb was inactive. Thin limbs of short loops showed a varying enzyme pattern. In the thick limb of Henle's loop, most enzyme activity was found at the luminal cell border. Distal convoluted tubules showed enzyme activity only at basal infolded membranes. In the late distal tubule, intercalated cells appear among the "ordinary" distal cells, and they contained abundant cytoplasmic enzyme. Many highly active intercalated cells were found also in the cortical and outer medullary segments of the collecting duct. The chief cells in these segments also showed some cytoplasmic enzyme activity. In the inner medullary segment of the collecting duct, enzyme activity disappeared gradually, and the tip of the papilla lacked activity. Acetazolamide (10 microM) completely abolished visible staining, whereas Cl 13850 (10 microM), an inactive acetazolamide analogue, did not interfere with the staining.  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-23

京公网安备 11010802026262号