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   9071篇
  免费   627篇
  国内免费   23篇
耳鼻咽喉   43篇
儿科学   259篇
妇产科学   259篇
基础医学   1377篇
口腔科学   181篇
临床医学   1062篇
内科学   1763篇
皮肤病学   241篇
神经病学   1202篇
特种医学   221篇
外科学   736篇
综合类   70篇
一般理论   9篇
预防医学   824篇
眼科学   305篇
药学   571篇
中国医学   20篇
肿瘤学   578篇
  2023年   79篇
  2022年   119篇
  2021年   212篇
  2020年   190篇
  2019年   223篇
  2018年   275篇
  2017年   219篇
  2016年   226篇
  2015年   278篇
  2014年   306篇
  2013年   475篇
  2012年   755篇
  2011年   728篇
  2010年   383篇
  2009年   352篇
  2008年   654篇
  2007年   611篇
  2006年   561篇
  2005年   532篇
  2004年   492篇
  2003年   457篇
  2002年   446篇
  2001年   73篇
  2000年   44篇
  1999年   66篇
  1998年   86篇
  1997年   74篇
  1996年   68篇
  1995年   46篇
  1994年   52篇
  1993年   44篇
  1992年   38篇
  1991年   26篇
  1990年   22篇
  1989年   18篇
  1988年   26篇
  1987年   32篇
  1986年   31篇
  1985年   23篇
  1984年   26篇
  1983年   27篇
  1982年   25篇
  1981年   16篇
  1980年   20篇
  1978年   28篇
  1977年   16篇
  1976年   18篇
  1975年   17篇
  1971年   17篇
  1970年   18篇
排序方式: 共有9721条查询结果,搜索用时 15 毫秒
1.
We report on 9 patients with pilomatricomas that showed unusual histopathologic features. Our patients were mainly elderly individuals (age range 42 to 88 years; mean age 70.1 years) who presented solitary cutaneous nodules situated on the head and neck (7 neoplasms), upper arm (1 neoplasm), and back (1 neoplasm). All the lesions were treated by simple excision. Follow-up data available in 7 of the 9 patients (mean follow-up, 17 months) revealed local recurrences in 1 patient whose lesion recurred 3 times. No lymph node involvement or distant metastases were recorded in any of our cases. Histopathologically, most neoplasms were characterized by a relatively large lesion in the clermis that in some cases showed extension to the subcutis. Each lesion was predominantly composed of a lobular proliferation of basaloid cells in association with adjacent focal areas containing eosinophilic, cornified material with shadow cells. In some cases, relatively large areas of shadow cells were present, whereas, in others only small foci of shadows cells were observed. Cytomorphologically, the basaloid cells showed features of matrical and supramatrical cells of a normal hair follicle and exhibited variable nuclear atypia and mitotic figures. The overall architectural pattern of the neoplasms was different from that of large fully developed stereotypical pilomatricomas that maintain a cystic character with basaloid cells predominantly aligned at the periphery. Based on the histopathologic findings, namely the presence of a large, lobular proliferation of basaloid cells in association with small to large foci of shadow cells, we interpreted these neoplasms to be a distinctive proliferative variant of pilomatricoma and propose the designation "proliferating pilomatricoma." Proliferating pilomatricomas should be differentiated from the recently described matricoma, basal-cell carcinoma with matrical differentiation, and matrical carcinoma (pilomatrical carcinoma).  相似文献   
2.
3.
1. The aim of the present study was to compare electrolyte handling in naturally reared neonatal spontaneously hypertensive rats (SHR) with those reared by a Wistar-Kyoto (WKY) rat foster mother (denoted SHRX), as cross-fostering SHR pups to a WKY rat dam lowers adult blood pressure in the SHR. 2. The electrolyte content of WKY rat and SHR dams’ milk was determined and electrolyte intake and urinary excretion rates were calculated in both naturally reared and cross-fostered WKY rat and SHR pups. 3. The milk sodium concentration fell in both strains (WKY rat: 31.8 ± 2.0 to 15.2 ± 1.2 mmol/L; SHR 31.9 ± 2.5 to 18.2 ± 1.6 mmol/L; P < 0.001), as did potassium (P < 0.001), over lactation, but there were no differences between strains. Calcium and magnesium concentrations increased (P< 0.001), although SHR dam's milk contained less calcium (P < 0.001) than that of WKY rat dams during the third week of lactation. 4. Spontaneously hypertensive rat pups ingested less milk (P<0.05) than WKY rat pups; therefore, their cumulative sodium intake over postnatal days 4–15 was significantly lower than that of WKY rat pups (WKY rat vs SHR: 84.4 ± 3.6 vs 59.7 ± 2.6 μmol/g bodyweight, respectively; P < 0.05) and fostered SHRX pups (77.7 ± 7.0 μmol/g bodyweight; P < 0.05). Potassium and magnesium intakes were comparable between SHR, WKY rat and SHRX pups, but SHR pups ingested significantly less calcium than either WKY rat pups (136.1 ± 6.4 vs 200.1 ± 9.5p, mol/g bodyweight, respectively; P<0.05) or SHRX pups (200.0 ± 18.0 μmol/g bodyweight; P<0.05). 5. These data show that the neonatal SHR experiences a period of sodium deficiency during the developmental stage when cross-fostering is effective in lowering blood pressure. This is consistent with the reported up-regulation of the renin-angiotensin system observed in SHR at this time and may have a long-term influence on blood pressure.  相似文献   
4.
5.
To estimate the evolution of amyloid in tissue, we studied abdominal fat aspirates of cases with familial amyloidotic polyneuropathy (FAP) longitudinally at regular intervals between 1994 and 2006. In 22 cases (13 carriers and nine patients) not yet transplanted median follow-up was 3.3 years (range 0.4-11.3). We found a significant increase in the amyloid grade of fat tissue from 2+ to 4+ and from 0 to 4+ in two of three subjects with follow-ups of >7 years, after 7 and 11 years, respectively. All other subjects remained negative or did not show a significant change. In 11 liver transplant patients, follow-up with fat aspirate was available with a median duration of 3.1 years (range 1.0-10.1). A comparison was made with cardiac amyloid as judged by the cardiac septum diameter and the serum NT-ProBNP (N-terminal pro-B-type natriuretic peptide) level. No stable increase of amyloid in fat was seen in any patient. A stable decrease of amyloid grade was seen in one patient 5 years after transplantation. In contrast, the cardiac septum diameter increased >or=4 mm in six of the 11 transplant patients. Our study shows the diagnostic utility of a regularly repeated fat aspirate in carriers at risk for the development of ATTR amyloidosis. Evolution of amyloid deposition in fat tissue is very gradual. After liver transplantation, amyloid deposition in fat tissue seems to stabilize and may even decrease in the long term, whereas amyloid deposition in cardiac tissue appears to be progressive.  相似文献   
6.
7.
Astrocytes, with their many functions in producing and controlling the environment in the brain, are of great interest when it comes to studying regeneration after injury and neurodegenerative diseases such as in grafting in Parkinson's disease. This study was performed to investigate astrocytic guidance of growth derived from dopaminergic neurons using organotypic cultures of rat fetal ventral mesencephalon. Primary cultures were studied at different time points starting from 3 days up to 28 days. Cultures were treated with either interleukin-1 beta (IL-1 beta), which has stimulating effects on astrocytic proliferation, or the astrocytic inhibitor cytosine arabinoside (Ara-C). Tyrosine hydroxylase (TH)-immunohistochemistry was used to visualize dopaminergic neurons, and antibodies against glial fibrillary acidic protein (GFAP) and S100 beta were used to label astrocytes. The results revealed that a robust TH-positive nerve fiber production was seen already at 3 days in vitro. These neurites had disappeared by 5 days. This early nerve fiber outgrowth was not guided by direct interactions with glial cells. Later, at 7 days in vitro, a second wave of TH-positive neuritic outgrowth was clearly observed. GFAP-positive astrocytic processes guided these neurites. TH-positive neurites arborized overlying S100 beta-positive astrocytes in an area distal to the GFAP-positive astrocytic processes. Treatment with IL-1 beta resulted in an increased area of TH-positive nerve fiber network. In cultures treated with Ara-C, neither astrocytes nor outgrowth of dopaminergic neurites were observed. In conclusion, this study shows that astrocytes play a major role in long-term dopaminergic outgrowth, both in axonal elongation and branching of neurites. The long-term nerve fiber growth is preceded by an early transient outgrowth of dopamine neurites.  相似文献   
8.
A bstract A rare case of congenital mitral insufficiency characterized by the hypoplasia of the posterior leaflet is reported. At operation, the mitral valve was successfully repaired by a ring annuloplasty, which created a satisfactory surface of coaptation between the anterior leaflet and the bulky posterior muscular structure. The presence of this posterior muscular structure represents a developmental arrest at the stage of conversion from muscular chordae and leaflets to thin connective structures.  相似文献   
9.
Twenty-two members of 18 families with autism have been examined for the presence of mutations and abnormal methylation in the FMR-1 region at Xq27.3. All patients fulfilled diagnostic criteria of infantile autism. A characteristic pattern of insertion and methylation were detected after Southern blot analysis in 7 autistic individuals expressing the fragile site at Xq27.3. Normal DNA patterns were observed in 15 autistic boys cytogenetically negative for the fragile site. The results indicate a lack of involvement of the FMR-1 region in infantile autists negative for fragile X expression. © 1992 Wiley-Liss, Inc.  相似文献   
10.
Although fever is a common symptom, few studies have broadly addressed this as a clinical problem in general practice. The aims of this study were to determine the frequency of fever among general practice patients in two rural municipalities in Norway, the diagnoses (according to ICHPPC-2-def.) of conditions causing fever, and the receptionist's role in the management of these problems. All the general practitioners and their receptionists within the study area participated. During 4 weeks throughout 1988 all individuals attending their general practitioner had their body temperature measured with an electronic thermometer (orally > or = 7 years, rectally < 7 years). Fever was defined as an oral body temperature > or = 37.5 degrees C (rectally > or = 38.0 degrees C in those < 7 years). All telephone applications, including telephone encounters for fever, were recorded. Fever was detected in 80 (5%) of a total of 1610 direct encounters: 36% of those below 7 years of age (n = 70) were febrile. One-third of the total encounters for fever were telephone encounters (n = 36), of which 30% were managed by the receptionists. A wide range of diagnoses were made, most of which were associated with infectious diseases. The distribution of the diagnoses of primary care patients with fever is different from those admitted to hospital for fever of unknown origin. General practitioners and their receptionists should consider fever a diagnostic challenge, especially when the patient is handled over the telephone.  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