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   2799篇
  免费   214篇
  国内免费   26篇
耳鼻咽喉   26篇
儿科学   162篇
妇产科学   57篇
基础医学   373篇
口腔科学   16篇
临床医学   213篇
内科学   529篇
皮肤病学   50篇
神经病学   145篇
特种医学   95篇
外国民族医学   1篇
外科学   416篇
综合类   273篇
预防医学   188篇
眼科学   39篇
药学   204篇
中国医学   10篇
肿瘤学   242篇
  2022年   34篇
  2021年   53篇
  2020年   29篇
  2019年   50篇
  2018年   47篇
  2017年   39篇
  2016年   59篇
  2015年   67篇
  2014年   75篇
  2013年   96篇
  2012年   138篇
  2011年   147篇
  2010年   78篇
  2009年   100篇
  2008年   138篇
  2007年   140篇
  2006年   159篇
  2005年   123篇
  2004年   131篇
  2003年   97篇
  2002年   86篇
  2001年   84篇
  2000年   82篇
  1999年   81篇
  1998年   47篇
  1997年   48篇
  1996年   33篇
  1994年   21篇
  1992年   35篇
  1991年   50篇
  1990年   49篇
  1989年   35篇
  1988年   36篇
  1987年   30篇
  1986年   31篇
  1985年   37篇
  1984年   19篇
  1981年   24篇
  1980年   19篇
  1979年   30篇
  1978年   27篇
  1977年   23篇
  1976年   16篇
  1975年   25篇
  1974年   22篇
  1973年   27篇
  1972年   23篇
  1971年   25篇
  1970年   16篇
  1969年   19篇
排序方式: 共有3039条查询结果,搜索用时 12 毫秒
81.
Cholera has been present in India since antiquity. Six pandemics originated in Indian subcontinent. The present seventh pandemic caused by El Tor Vibrio cholerae started from Indonesia (Sulawesi) in 1961 and entered India in 1964. By the end of 1965 it has replaced the age old classical V. cholerae. Many of the States which never had cholera or were free from it for a long time got infected and became endemic foci of El Tor infection. This article reviews the epidemiological features of important outbreaks reported after 1975 in India.  相似文献   
82.
Amylin and amylin-amide lack an acute effect on blood glucose and insulin   总被引:1,自引:0,他引:1  
Amylin-amide has been implicated in the pathogenesis of type II diabetes due to its proposed inhibitory effect on insulin release from beta cells of the pancreatic islets, and on glucose uptake by the skeletal muscle. In experiments with rats and rabbits we failed to demonstrate these anti-insulin actions of amylin and amylin-amide. A single bolus dose of the two peptides (500 pmol) administered i.v. failed to suppress plasma insulin levels or to elevate blood glucose levels. The continuous infusion of amylin-amide into rabbits also failed to suppress the release of insulin in response to hyperglycaemia produced by an i.v. bolus injection of glucose. These in vivo observations imply that the amylin peptides may not have a primary physiological role in carbohydrate metabolism, but in view of our previous findings, we speculate that the peptide has a more prominent role in calcium homeostasis.  相似文献   
83.
84.
BACKGROUND: We explored whether inducible nitric oxide synthase (iNOS) driven nitric oxide (NO) production regulates expression of iNOS, endothelial NOS (eNOS), Cyclooxygenase-2 (COX-2), and Hemeoxygenase-1 (HO-1) proteins in a rat model of glomerulonephritis induced by antibody raised in rabbits against rat glomerular basement membrane (anti-GBM). METHODS: Rats were injected either with non-immune serum (control), or anti-GBM serum. In a group of rats N6-(1-iminoethyl)-L-lysine (L-NIL) was administered prior to injection of anti-GBM serum to inhibit iNOS activity. Urinary nitrite plus nitrate (NOx) excretion was assessed to determine the extent of iNOS inhibition by L-NIL. Urinary albumin excretion was assessed to determine extent of proteinuria. Urinary PGE2 was assessed as a marker of COX activity. Glomeruli were harvested 24 h after injection of anti-GBM serum and ED1, COX-2, iNOS, eNOS and HO-1 expression was analysed by Western blot analysis. RESULTS: iNOS activity in glomeruli was effectively reduced in L-NIL-treated nephritic animals. In these animals, there was exacerbation of proteinuria and reduction in urinary PGE2 levels without changes in the extent of macrophage infiltration in glomeruli. In nephritic animals, there was an increase in glomerular protein levels of COX-2, HO-1 and iNOS, but not of eNOS. While L-NIL treatment reduced glomerular HO-1, levels of COX-2 and iNOS increased; but not that of eNOS. CONCLUSIONS: The observations indicate that in glomerulonephritis iNOS-driven NO production acts as a negative feedback regulator of iNOS itself, suppresses COX-2 levels, and maintains HO-1 levels.  相似文献   
85.
86.

Background/purpose

The anal position index (API) defines the normal anal position as the ratio of fourchette–anal distance to fourchette–coccyx distance for females and the scrotum–anal distance to scrotum‐coccyx distance for males. In this study, measurement of the API in newborns and infants with anorectal malformations (ARM), using the center of the midline anal dimple (AD) to represent the center of the proposed neoanus, was performed to assess whether or not the AD was located in a significantly abnormal position as correlated with the normal anal position.

Methods

The cases comprised 65 consecutive newborn and infants with ARM, divided into 2 age-based groups (Group A: 1st day to 1 month; Group B: 1–12 months), without sacral or significant perineal abnormalities. Controls included an equal number of age and gender matched patients admitted for other conditions. The characteristics of the AD (‘well developed’ or ‘moderately developed’) as well as those of the midline perineal raphé in males and the perineal groove in females were also recorded.

Results

Combining both age groups, the mean API ± SD was 0.41 ± 0.012 in male cases and 0.53 ± 0.07 in male controls (p value 0.003). The corresponding values for female cases and controls were 0.31 ± 0.09 and 0.36 ± 0.07 respectively (p = 0.040). In male newborns, the API in cases was significantly lower than the API in controls (p < 0.001). Combining both males and female newborns, the differences between the API in cases and controls was also statistically significant (p < 0.001). In older boys as well as in girls from both age groups, apart from cases of persistent cloaca, the API was lower in cases than in controls, especially in boys, although the difference was not statistically significant. On comparing the API in individual male ARM with that in male controls, cases of rectobulbar urethral fistula (RBUF) and rectovesical fistula had a statistically significant lower API (p < 0.001). In the 4 cases of persistent cloaca, the mean API (0.40 ± 0.1) was higher than the mean API in female controls and the AD was well developed with a well-delineated, narrow perineal groove. The majority (53/65; 81.53%) of patients had a ‘well developed’ AD. Twelve patients (18.47%) had a ‘moderately developed’ AD including 10 females and 2 males. There were 15 patients with a depressed AD (anal fossette); of these 12 (80%) were females. All boys had a well delineated perineal raphé in contrast to 10 girls (29.4% of total female ARM) who had a poorly delineated midline perineal groove.

Conclusions

During definitive surgery for ARM, if the AD is taken as the site of the proposed neoanus, the neoanal position is likely to be anterior to the normal anal position in both males and females and especially so in males. Overall, girls with ARM appear to be more likely to have a relatively poorly developed and/ or depressed AD and a poorly delineated perineal groove.

Type of study

Clinical Research.

Level of evidence

Level III.  相似文献   
87.
Carcinoma of the penis tends to have a predictable route of spread by direct invasion and by regional lymphatic involvement to the inguinal group of lymph nodes. Blood-borne distant spread is rare, last to occur, and is seen in 1-3% of cases. Metastasis to the spine is even rarer. We encountered one such case who presented with spinal metastasis, as documented by the whole body bone scan, and this was later followed by involvement of the inguinal nodes. This case is unique in its site of metastatic presentation as well as its pattern of presentation.  相似文献   
88.
Rheumatic heart disease is a significant clinical entity in young children, especially in the developing world. One of the major long-term effects of ill managed rheumatic fever is irreversible damage to the cardiac valve leaflets, primarily on the left side. With the limited success of currently available mechanical and bioprosthetic valves, there is an urgent need for new directions in bioprosthetic valves, both in material, including source, degree of fixation, surface, bulk modifications, etc., and design. In the present paper, new proposals in the material selection and fabrication of bioprosthetic valves are proposed based on electron microscopic studies of natural valve leaflets and the pericardial surface. Current approaches for bioprosthetic valve fabrications include the wide use of the pericardium as a leaflet material. The present study indicates a need for nondestructive surface examination of pericardial sheets for the elimination of areas of surface voids resulting from gross fiber disorientation. Also, there seems to be a need for incorporation of an in situ fiber renewal mechanism in bioprosthetic leaflets to emulate the natural valve more closely. Apparently natural leaflets have built-in fiber renewal mechanism(s).  相似文献   
89.
90.
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