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   3749篇
  免费   216篇
  国内免费   24篇
耳鼻咽喉   27篇
儿科学   116篇
妇产科学   63篇
基础医学   481篇
口腔科学   106篇
临床医学   265篇
内科学   899篇
皮肤病学   51篇
神经病学   293篇
特种医学   111篇
外科学   673篇
综合类   19篇
预防医学   309篇
眼科学   56篇
药学   201篇
中国医学   25篇
肿瘤学   294篇
  2023年   28篇
  2022年   69篇
  2021年   126篇
  2020年   77篇
  2019年   111篇
  2018年   132篇
  2017年   72篇
  2016年   86篇
  2015年   115篇
  2014年   134篇
  2013年   169篇
  2012年   308篇
  2011年   288篇
  2010年   176篇
  2009年   130篇
  2008年   247篇
  2007年   270篇
  2006年   242篇
  2005年   211篇
  2004年   196篇
  2003年   234篇
  2002年   214篇
  2001年   30篇
  2000年   15篇
  1999年   25篇
  1998年   27篇
  1997年   18篇
  1996年   22篇
  1995年   14篇
  1994年   15篇
  1993年   15篇
  1992年   18篇
  1991年   11篇
  1990年   14篇
  1989年   13篇
  1988年   13篇
  1987年   7篇
  1986年   14篇
  1985年   6篇
  1984年   10篇
  1983年   3篇
  1982年   14篇
  1981年   8篇
  1980年   5篇
  1978年   7篇
  1976年   3篇
  1975年   3篇
  1964年   2篇
  1932年   2篇
  1929年   2篇
排序方式: 共有3989条查询结果,搜索用时 15 毫秒
91.
Periconceptional vitamin supplementation with folate prevents about three-quarters of expected cases of neural tube defects (NTDs) in clinical trials. However, vitamin action may be regulated at the level of the gene, and individual susceptibility to environmental agents, including dietary components, also may be under genetic control. We investigated the presence of familial factors in a retrospective case control study of neural tube defects in Genoa, Italy. Cases included all patients treated at a single pediatric neurosurgical service. Controls matched on age and sex came from the same hospital. We found strong evidence for the contribution of genetic factors in this study. There was an excess risk of 14 for the occurrence of NTDs in first-degree relatives compared to controls (P < .0005). There was no difference in sex ratio in any group of relatives, but maternal grandparents of children with a high spinal lesion had 14% fewer offspring than paternal grandparents (P < .005), possibly because of excess miscarriages. Our study is the first to show complex patterns of inheritance in spina bifida families affecting three generations in one clinical subgroup and preferentially on the mother's side. These results support a role for genomic imprinting and highlight the value of multidisciplinary epidemiologic and clinical studies that include multiple generations. New studies incorporating dietary and genetic approaches will help clarify and extend these findings. © 1996 Wiley-Liss, Inc.  相似文献   
92.
93.
94.
European Archives of Oto-Rhino-Laryngology - To analyze the surgical outcomes in terms of postoperative wound complications in a small case series of six patients treated with lateral cervical...  相似文献   
95.
Summary β-thromboglobulin (BTG) and fibrinopeptide A (FpA) were studied in 68 non-insulin dependent diabetic patients (NIDD) aged 32–81 with a mean duration of diabetes of 9±0.8 SEM years and 44 healthy controls, comparable for age and sex. Diabetic patients were subdivided into subsets according to the presence of microvascular disease, macrovascular disease or the absence of these lesions. Patients with microangiopathy (micro- and/or macrovascular disease) had higher HbA (p<0.01), higher blood pressure (p<0.05) than both healthy controls and uncomplicated diabetics. Plasma BTG was higher in diabetic patients than in healthy controls (p<0.02), and was higher in complicated than in non-complicated diabetic subjects. Fpa was higher in complicated than in non-complicated diabetes (p<0.05). No differences were observed between the two subsets of complicated patients. In conclusion, we have shown that increased plasma- and platelet-BTG levels are present in non-insulin dependent diabetic subjects, with normal renal function and that plasma BTG is higher in patients with than in those without vascular disease. Fibrinopeptide A, a sensitive marker ofin vivo fibrin formation, was significantly increased in NIDD with vascular complications. This study was supported by the Juvenile Diabetes Foundation Grant N. 184066 and by the National Research Council of Italy,Progetto Finalizzato di Medicina Preventiva e Riabilitativa, Sottoprogetto 4.  相似文献   
96.
The osteoprotegerin-ligand (OPG-L) has been identified as the essential factor required for osteoclastogenesis, and its effects are prevented by the osteoprotegerin (OPG). The OPG-L/OPG balance plays a crucial role in coordinating the sequence of osteoclast and osteoblast differentiation during the bone remodeling. The aim of the study was to investigate if polymethylmethacrylate-based cements are able to modulate the expression of OPG-L/OPG in MG63 cells, which are known to have high levels of OPG and inducible expression of OPG-L. Four radio-opaque cements. namely Sulfix-60, CMW1, CMW2 and CMW3, were polymerized for either 1 h or 7 d. MG63 were incubated for 24 h with culture medium only, cement extracts and 2 microg/ml of human recombinant IL-1beta as positive control. An RT-PCR was performed to detect the OPG and OPG-L expression, and the house-keeping gene, GAPDH, was used as a reference for the semi-quantitative analysis. An increase in the OPG-L band density was observed for all cements, and consequently, the OPG-L/OPG ratio also increased. The ability of bone cements to induce the expression of OPG-L could be a co-factor in the development of osteolysis at the bone-cement interface.  相似文献   
97.
98.
BACKGROUND: Controversy exists regarding axillary dissection (ALND) for sentinel node (SLN) metastases detected as isolated tumor cells (ITC). We hypothesized that the number of positive non-SLNs is low and ALND is unnecessary for most patients with ITC. METHODS: From 1995 to 1999, 634 breast cancer patients underwent SLND. SLNs were examined using immunohistochemistry if hematoxylin and eosin was negative. ALND was recommended for ITC-positive SLNs. RESULTS: Seventy-eight patients (12.3%) with ITC-positive SLNs were offered ALND. Sixty-one consented, whereas 17 refused. Fifty-eight (95.1%) had negative non-SLNs. Three (4.9%) had non-SLN metastases. One patient (1.6%) had macrometastatic disease, whereas 2 (3.3%) had micrometastases. No ITC-only-positive SLN patient experienced axillary recurrence. CONCLUSIONS: When ALND was performed for ITC, 1.6% of non-SLNs harbored macrometastases and 3.3% had micrometastases. When ALND was not performed, axillary recurrence was not seen. The low risk of non-SLN disease in this study fails to support the routine use of ALND for ITC-positive SLNs.  相似文献   
99.
Bacterial nanocellulose (BNC) membranes, with remarkable physical and mechanical properties, emerged as a versatile biopolymeric carrier of bioactive compounds for skin care applications. In this study, BNC membranes were loaded with glycerol (as plasticizer and humectant agent) and different doses (1–3 μg cm−2) of an aqueous extract obtained from the hydro-distillation of Eucalyptus globulus Labill. leaves (HDE), for application as sheet facial masks. All membranes are resistant and highly malleable at dry and wet states, with similar or even better mechanical properties than those of a commercial BNC mask. Moreover, the HDE was found to confer a dose-dependent antioxidant activity to pure BNC. Additionally, upon 3 months of storage at 22–25 °C and 52% relative humidity (RH) or at 40 °C and 75% RH, it was confirmed that the antioxidant activity and the macroscopic aspect of the membrane with 2 μg cm−2 of HDE were maintained. Membranes were also shown to be non-cytotoxic towards HaCaT and NIH/3T3 cells, and the membrane with 2 μg cm−2 of HDE caused a significant reduction in the senescence-associated β-galactosidase activity in NIH/3T3 cells. These findings suggest the suitability and potential of the obtained membranes as bioactive facial masks for anti-aging applications.  相似文献   
100.
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