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   3766篇
  免费   171篇
  国内免费   7篇
耳鼻咽喉   15篇
儿科学   291篇
妇产科学   66篇
基础医学   470篇
口腔科学   145篇
临床医学   233篇
内科学   629篇
皮肤病学   54篇
神经病学   226篇
特种医学   98篇
外科学   508篇
综合类   92篇
一般理论   2篇
预防医学   212篇
眼科学   125篇
药学   547篇
中国医学   18篇
肿瘤学   213篇
  2023年   13篇
  2022年   63篇
  2021年   99篇
  2020年   55篇
  2019年   63篇
  2018年   82篇
  2017年   63篇
  2016年   68篇
  2015年   86篇
  2014年   151篇
  2013年   165篇
  2012年   249篇
  2011年   265篇
  2010年   142篇
  2009年   135篇
  2008年   205篇
  2007年   218篇
  2006年   166篇
  2005年   174篇
  2004年   145篇
  2003年   135篇
  2002年   121篇
  2001年   112篇
  2000年   98篇
  1999年   83篇
  1998年   31篇
  1997年   32篇
  1996年   21篇
  1995年   15篇
  1994年   12篇
  1993年   15篇
  1992年   67篇
  1991年   56篇
  1990年   58篇
  1989年   53篇
  1988年   47篇
  1987年   40篇
  1986年   53篇
  1985年   38篇
  1984年   27篇
  1983年   22篇
  1981年   13篇
  1979年   17篇
  1977年   16篇
  1976年   11篇
  1974年   17篇
  1973年   19篇
  1972年   15篇
  1970年   9篇
  1969年   10篇
排序方式: 共有3944条查询结果,搜索用时 31 毫秒
71.
This case has been presented as pellagra, which is very rare in children. Pellagra is due dietary deficiency of niacin. Usually seen in alcoholics, malabsorption syndromes occur very rarely in children. A 11-y-old girl presented with well-defined, hyperpigmented, hyperkeratotic, symmetrical, thick scaly plaques surrounded by erythema on the dorsum of the hands, arms, feet, legs up to knees, and along the sides of the neck. The child was given 100 mg of Nicotinamide. Skin lesions resolved rapidly with the treatment and the child improved.  相似文献   
72.
While research has identified gender differences in characteristics and outcomes of smokers in the general population, no studies have examined this among smokers with psychosis. This study aimed to explore gender differences among 298 smokers with psychosis (schizophrenia, schizoaffective and bipolar affective disorder) participating in a smoking intervention study. Results revealed a general lack of gender differences on a range of variables for smokers with psychosis including reasons for smoking/quitting, readiness and motivation to quit, use of nicotine replacement therapy, and smoking outcomes including point prevalence or continuous abstinence, and there were no significant predictors of smoking reduction status according to gender at any of the follow-up time-points. The current study did find that female smokers with psychosis were significantly more likely than males to report that they smoked to prevent weight gain. Furthermore, the females reported significantly more reasons for quitting smoking and were more likely to be driven by extrinsic motivators to quit such as immediate reinforcement and social influence, compared to the male smokers with psychosis. Clinical implications include specifically focussing on weight issues and enhancing intrinsic motivation to quit smoking for female smokers with psychosis; and strengthening reasons for quitting among males with psychosis.  相似文献   
73.
Previous nuclear magnetic resonance (NMR) imaging studies have indicated that coronary occlusion does not produce sufficient changes in standard tissue relaxation times to allow the detection of acute ischemia. To identify acute myocardial perfusion abnormalities, the use of the paramagnetic agent manganese gluconate combined with calcium gluconate (MnGlu/CaGlu) was investigated in canine models of acute coronary artery occlusion. In vitro studies showed that MnGlu/CaGlu was a more efficient relaxing agent than gadolinium-DTPA (relaxivity of 7.8 versus 5.1 s-1 mM-1) and demonstrated affinity for normal myocardium. The distribution of MnGlu/CaGlu as measured by manganese-54 tracer studies was proportional to myocardial blood flow in both normal and ischemic tissue. Hearts excised from dogs after coronary artery occlusion and administration of 0.035 mM/kg MnGlu/CaGlu were imaged ex vivo using a relatively spin-lattice relaxation time (T1)-weighted gradient reversal technique (repetition time [TR] 50 ms and echo time [TE] 9 ms). These images showed increased signal intensity in the normally perfused myocardium with a mean signal intensity ratio of hypoperfused to normal myocardium of 0.55 +/- 0.12 (mean +/- SD). In vivo images obtained in nine dogs after coronary artery occlusion and administration of the same dose of MnGlu/CaGlu demonstrated the region of hypoperfused myocardium in six dogs with a signal intensity ratio of hypoperfused to normal myocardium of 0.64 +/- 0.23 (p less than 0.05 versus control). When a higher dose of 0.1 mM/kg MnGlu/CaGlu was utilized and in vivo imaging was performed using a relatively spin-spin relaxation time (T2)-weighted (TR gated, TE 60 ms) spin-echo sequence in six dogs, the signal intensity of normal myocardium was decreased.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
74.
BACKGROUND: Growing evidence suggests that intestinal recovery from injury induced by radiation, endotoxin, and protein deficiency is improved by the ingestion of nucleosides and nucleotides. AIM: This study examined the effect of dietary nucleosides and nucleotides supplementation on trinitrobenzene sulphonic acid induced colonic damage in experimental colitis. METHODS: Sprague-Dawley rats were randomised into two groups and fed nucleic acid free 20% casein diet (control) or this diet supplemented with 0.5% nucleoside-nucleotide mixture for four weeks. On the second week, colonic inflammation was induced in rats by intracolonic administration of 0.25 ml of 50% ethanol containing 25 mg of trinitrobenzene sulphonic acid. Additionally, other sets of rats were treated with 0.25 ml of 50% ethanol, 25 mg of trinitrobenzene sulphonic acid in 0.25 ml saline, or 0.25 ml of 0.9% saline. RESULTS: After two weeks, colon weight, macroscopic and microscopic damage scores, were significantly greater (p < 0.05) in the nucleoside-nucleotide supplemented group compared with the non-supplemented control groups. The same variables seen in the trinitrobenzene sulphonic acid-ethanol group fed nucleoside-nucleotide free diet were greater (p < 0.05) than in the rest of the groups fed nucleoside-nucleotide free diet and treated with ethanol, trinitrobenzene sulphonic acid in saline, or saline. Histologically, segmental ulceration and inflammation associated with significantly increased infiltration of polymorphonuclear leucocytes, macrophages, lymphocytes, fibroblasts were observed in the supplemented group compared with the controls. In the nucleoside-nucleotide supplemented group the epithelial damage, mucosal erosion, oedema, and coagulative necrosis of the muscularis propria was more extensive in comparison to the non-supplemented control groups. CONCLUSIONS: This study suggests that dietary nucleosides and nucleotides may aggravate colonic damage and inflammation in chemically induced experimental colitis in rats; and that nucleoside-nucleotide free diet combined with other pharmacological agents may offer a better response.  相似文献   
75.
This is a retrospective comparison of partially mismatched related donor transplantation (PMRDT) and autotransplantation (ABMT) in advanced acute leukemia. Patients underwent T-cell-depleted PMRDT (n=164) or ABMT (n=131) for acute myeloid leukemia (n=130) or acute lymphoblastic leukemia (n=165). Fewer PMRDT patients were in remission (29 vs 85%; P<0.0001). The 5-year cumulative incidence of transplant-related mortality (TRM) was 52% after PMRDT and 16% after ABMT (P<0.0001). The 5-year cumulative incidence of relapse was 32% after PMRDT and 54% after ABMT (P=0.006). The actuarial unadjusted 5-year disease-free survival (DFS) was 16% after PMRDT and 30% after ABMT. In Cox's regression analysis, PMRDT (P<0.0001) and age >15 years (P=0.002) were associated with higher TRM, active disease (P=0.0021), ABMT (P=0.0074) and male sex (P=0.011) with higher relapse, and age >15 years (P=0.0007) and PMRDT (P=0.047) with lower DFS. Amongst second remission patients, TRM was higher after PMRDT (P=0.0003), relapse was higher after ABMT (P=0.034), and 5-year DFS was comparable (32% ABMT and 25% PMRDT). ABMT, if feasible, may be preferable to PMRDT in advanced acute leukemia patients since lower relapse after PMRDT is offset by higher TRM. If an autograft is not feasible because of nonavailability of autologous cells or very advanced disease, PMRDT is a potential alternative.  相似文献   
76.
A prospective serial follow-up after coil closure of patent ductus arteriosus in 84 patients showed a cumulative duct closure up to 96% at the end of 2 years. Five patients underwent transient recanalization, and 4 patients required repeat procedure for residual shunt or recanalization.  相似文献   
77.
78.
Thermogenic responses to similar doses of norepinephrine appear to be different when repeatedly administered. This hypothesis was tested by three consecutive 30-minute infusions of a fixed dose of norepinephrine separated by a rest period of one hour between infusions. There was a significant increase or potentiation of the metabolic response as measured by oxygen consumption to the third dose of norepinephrine, while the cardiovascular responses showed no change. It is therefore important to make allowances for this phenomenon when assessing intergroup differences in regulatory thermogenesis using dose-response protocols for norepinephrine administration.  相似文献   
79.
80.
Eighteen highly exposed but persistently seronegative (HEPS) women (HW) and their human immunodeficiency virus (HIV) type 1-seropositive male partners were studied for HIV-specific T cells and other host factors. Circulating HIV-specific T cells were measured by interferon-gamma enzyme-linked immunospot assays, using recombinant vaccinia virus vectors expressing HIV proteins. Nine (50%) of the HW and all HIV-seropositive persons had HIV-specific T cell responses. Only 2 (22%) of the HEPS responders recognized Env, compared with 94% of HIV-seropositive persons. A high percentage (75%) of the HW with HIV-specific T cell responses reported recent HIV exposure. Remarkably, however, long-lived HIV-specific T cells were detected in 2 HW who had an extended period (>3.9 years) of no HIV exposure. These findings have important implications for HIV vaccine design.  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