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   5970篇
  免费   336篇
  国内免费   17篇
耳鼻咽喉   54篇
儿科学   156篇
妇产科学   89篇
基础医学   870篇
口腔科学   166篇
临床医学   324篇
内科学   1347篇
皮肤病学   61篇
神经病学   424篇
特种医学   246篇
外国民族医学   1篇
外科学   1104篇
综合类   28篇
预防医学   140篇
眼科学   172篇
药学   458篇
中国医学   10篇
肿瘤学   673篇
  2023年   30篇
  2022年   71篇
  2021年   152篇
  2020年   46篇
  2019年   83篇
  2018年   131篇
  2017年   95篇
  2016年   112篇
  2015年   91篇
  2014年   121篇
  2013年   169篇
  2012年   270篇
  2011年   334篇
  2010年   190篇
  2009年   190篇
  2008年   280篇
  2007年   289篇
  2006年   241篇
  2005年   277篇
  2004年   295篇
  2003年   260篇
  2002年   289篇
  2001年   174篇
  2000年   230篇
  1999年   183篇
  1998年   61篇
  1997年   69篇
  1996年   56篇
  1995年   40篇
  1994年   39篇
  1993年   36篇
  1992年   119篇
  1991年   100篇
  1990年   128篇
  1989年   121篇
  1988年   108篇
  1987年   97篇
  1986年   92篇
  1985年   118篇
  1984年   72篇
  1983年   59篇
  1982年   30篇
  1979年   44篇
  1978年   37篇
  1977年   24篇
  1975年   21篇
  1973年   26篇
  1971年   26篇
  1969年   26篇
  1968年   29篇
排序方式: 共有6323条查询结果,搜索用时 15 毫秒
11.
We report a case of groove pancreatitis (GP) associated with a true pancreatic cyst. An 81-year-old man who had suffered epigastric pain for 4 months was referred to Saisekai Kure Hospital. Computed tomography and endoscopic retrograde pancreatography showed a cystic lesion in the groove area of the pancreas. Serum amylase elevation and imaging findings suggested GP due to the cyst. Six weeks of medical treatment did not improve the clinical symptoms. Therefore, pancreatoduodenectomy was performed. Histologic examination revealed a true cyst with intraluminal necrosis, which produced a protein plug that obstructed the Santorini duct. The parenchyma surrounding the groove area showed marked fibrosis and inflammatory cell infiltration. GP due to true pancreatic cyst was diagnosed. Although GP is usually caused by overconsumption of alcohol, which leads to changes in the pancreatic juice and the ultimate blockage of pancreatic outflow, the histologic features in our patient suggest that true pancreatic cyst stands as a secondary cause of GP.  相似文献   
12.
In this study, we characterize bone microstructure, specifically sex differences, at multiple skeletal sites in 165 subjects >52 yr of age, using microCT technology in vitro. Significant sex differences are observed at the distal radius, femoral neck, and femoral trochanter, but not at the iliac crest, calcaneus, and lumbar vertebral body. Correlations in BV/TV between sites ranged from r = 0.13 to 0.56. INTRODUCTION: The goals of this study were (1) to assess potential sex differences of bone microstructure and their difference between skeletal sites and (2) to explore the relationship of trabecular microstructural properties between relevant skeletal sites. MATERIALS AND METHODS: Trabecular bone microstructural properties were measured in vitro in 165 subjects 52-99 yr of age using microCT. Defined volumes of interest (cylinders with 6 mm diameter and 6 mm length) were scanned at a resolution of 26 microm (isotropic) in six different anatomical sites: distal radius, femoral neck and trochanter, iliac crest, calcaneus, and second lumbar vertebral body. RESULTS: At the radius and femoral neck, trabecular bone displayed a more plate-like structure, thicker trabeculae, smaller separation/higher trabecular number, higher connectivity, and a higher degree of anisotropy in men than in women (p < 0.05). At the trochanter, men displayed more plate-like structure and thicker trabeculae (p < 0.05), but no differences in trabecular separation or other parameters compared with the women. At the calcaneus, iliac crest, and second lumbar vertebra none of the bone parameters displayed significant differences between sexes. The BV/TV at one site explained a range of only 2-32% of the variability at other sites. CONCLUSIONS: These results suggest that trabecular bone microstructural properties are remarkably heterogeneous throughout the skeleton. Significant differences between men and women are observed at some, but not at all, sites. The magnitude of sex differences in trabecular microstructure coincides with that of fracture incidence observed for some of the sites in epidemiological studies.  相似文献   
13.
In order to correctly diagnose and treat severe postoperative infections, it may be critical to detect and differentiate between endotoxin derived from Gram-negative bacteria and/or beta-glucan derived from fungi. In addition to the chromogenic assay, the turbidimetric kinetic assay has been performed for the quantification of endotoxin in plasma using Limulus amebocyte lysate as previously reported. However, it is also known that beta-glucan triggers the coagulation of Limulus amebocyte lysate. In the present study, the differentiation of beta-glucan from endotoxin and its clinical application were studied. Endotoxin was able to be inactivated in plasma using one-tenth dilution by 10 per cent ethanol or distilled water, followed by heating at 100 degrees C for 120 min, without affecting the activity of coexisting beta-glucan. The treated sample was then subjected to the turbidimetric kinetic assay using Toxinometer ET-201. Using this method, as little as 30 pg/ml of beta-glucan in the plasma may be assayed separately, with the amount of circulating beta-glucan in the plasma of normal subjects being less than 50 pg/ml. On the other hand, in patients with a fungal infection, the amount of beta-glucan in their plasma was elevated significantly. Clinically, beta-glucanemia may often occur in severe postoperative infection even if fungi are not detected.  相似文献   
14.
Both D-dimer and E fragments in urinary FDP were determined in renal transplantation patients. Urinary D-dimer fragments increased in 14 out of 20 acute rejections (70.0%) and in 6 out of 18 chronic rejections (33.3%). Urinary E fragments increased in 8 out of 9 acute rejections (88.9%) and in 4 out of 5 chronic rejections (80.0%). It is suggested that urinary FDP-E fragment is a better indicator to detect or predict rejection than the whole Urinary FDP. The appearance of D-dimer in the urine indicates intravascular coagulation in glomeruli followed by a secondary fibrinolysis in the course of the rejection reaction. The urinary D-dimer/FDP ratio which was used as the indicator of fibrinolytic activity in glomeruli was obtained in various conditions of renal transplants. The ratios were relatively high in the urines from well functioning grafts. This ratio deteriorated at the onset of rejection crisis and tended to go upward during the course of the recovery when the rejection was reversible. In the cases of irreversible acute rejection and chronic rejection, these ratios remained at a low level. D-dimer/FDP ratio might be useful indicator to predict the reversibility of rejection and the prognosis of renal allograft. Furthermore, these findings suggest that fibrinolytic and thrombolytic therapy by the tissue-type plasminogen activator (t-PA) along with immunosuppressive drugs might be more effective for the treatment of these rejections.  相似文献   
15.
We reviewed retrospectively 20 cases of optociliary vein over the past 5 years. Fifteen of the 20 cases (75%) were over 40 years of age. There was no sex differences (9 males and 11 females). Causative ocular diseases were: central retinal vein occlusion (14 cases, 70%); optic disc drusen (2 cases, 10%); and optic nerve sheath meningioma, high myopia, glaucoma, congenital anomaly (1 case each, total 20%). The number of patients with an optociliary vein was high in central retinal vein occlusion (14/190 cases, 7.4%). We concluded that occurrence of optociliary vein is not restricted to cases with optic nerve sheath meningioma and this shunt vessel may occur under other conditions in which central retinal venous return is seriously disturbed. The most common cause of optociliary vein is central retinal vein occlusion.  相似文献   
16.
A nondestructive method using a combination of three 2D NMR techniques, DQF-COSY (double quantum filter correlation spectroscopy), HMQC (1H-detected multiple quantum coherence), and HMBC (heteronuclear multiple bond correlation), were developed for structural determination of microcystins, toxic heptapeptides produced by cyanobacteria. With this procedure we were able to assign all carbons and protons of microcystins LR (1) and RR (2), thus determining the constituent amino acid sequences. The procedure was also applied to the microcystin-associated nontoxic minor components, which have molecular weights and amino acid compositions similar to those of 1 and 2 and toxicities different from those of 1 and 2. From detailed analysis of these spectra we rapidly deduced that the minor components are geometrical isomers with respect to C-7 of the diene in Adda of the parent toxins. The structures were finally confirmed to be 3 and 4 by ROESY (rotating frame nuclear Overhauser and exchange spectroscopy) technique.  相似文献   
17.
18.
19.
A review of data on 360 patients with esophageal squamous cell carcinoma who underwent esophageal resection revealed 14 cases (3.9%) and 16 lesions with synchronous gastric carcinomas. Among the 16 lesions, there were 14 (87.5%) early gastric carcinomas and two advanced carcinomas. Of the 14 early gastric carcinomas, two were minute (less than 5 mm in the largest diameter) early gastric carcinomas and four small (6-10 mm in the largest diameter). These gastric carcinomas were in a relatively early stage. The six early gastric carcinomas were not detected preoperatively. However, a thorough observation of the gastric mucosa could not be done in four of those due to stenosis which had developed as a result of the esophageal carcinoma. Therefore, intraoperative gastric observation should be done in cases in which the findings of the preoperative endoscopic examination of the stomach are inadequate and the upper gastrointestinal series reveal certain gastric abnormalities.  相似文献   
20.
We have constructed the recombinant baculovirus which expresses the human immunodeficiency virus type 1 negative factor (nef) gene. Spodoptera frugiperda cells infected with the recombinant virus produced a 27-kDa protein which reacted with rabbit antisera raised against a carboxy-terminal synthetic peptide of the Nef protein by immunoblot analysis. Labeling experiment showed that the recombinant Nef protein was myristoylated. The recombinant Nef protein was purified to near homogeneity by DEAE-Sephacel, phenyl-Sepharose 4B, blue-Sepharose, and Sephadex G-150 column chromatography. No detectable GTP binding activity was observed in the purified recombinant Nef product.  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