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   7484篇
  免费   690篇
  国内免费   16篇
耳鼻咽喉   120篇
儿科学   219篇
妇产科学   201篇
基础医学   970篇
口腔科学   193篇
临床医学   679篇
内科学   1328篇
皮肤病学   227篇
神经病学   461篇
特种医学   277篇
外科学   836篇
综合类   326篇
一般理论   2篇
预防医学   958篇
眼科学   155篇
药学   538篇
中国医学   11篇
肿瘤学   689篇
  2022年   48篇
  2021年   97篇
  2020年   78篇
  2019年   127篇
  2018年   131篇
  2017年   115篇
  2016年   138篇
  2015年   173篇
  2014年   177篇
  2013年   225篇
  2012年   355篇
  2011年   295篇
  2010年   227篇
  2009年   212篇
  2008年   333篇
  2007年   369篇
  2006年   394篇
  2005年   365篇
  2004年   334篇
  2003年   292篇
  2002年   270篇
  2001年   233篇
  2000年   250篇
  1999年   230篇
  1998年   130篇
  1997年   129篇
  1996年   106篇
  1995年   98篇
  1994年   93篇
  1993年   65篇
  1992年   137篇
  1991年   165篇
  1990年   163篇
  1989年   146篇
  1988年   165篇
  1987年   123篇
  1986年   107篇
  1985年   113篇
  1984年   110篇
  1983年   66篇
  1982年   55篇
  1981年   58篇
  1979年   74篇
  1978年   51篇
  1977年   50篇
  1976年   49篇
  1975年   56篇
  1974年   54篇
  1973年   52篇
  1972年   44篇
排序方式: 共有8190条查询结果,搜索用时 15 毫秒
91.
Abstract: Indolicidin is a 13‐residue antimicrobial peptide amide, ILPWKWPWWPWRR‐NH2, isolated from the cytoplasmic granules of bovine neutrophils. Indolicidin is active against a wide range of microorganisms and has also been shown to be haemolytic and cytotoxic towards erythrocytes and human T lymphocytes. The aim of the present paper is two‐fold. First, we examine the importance of tryptophan in the antibacterial activity of indolicidin. We prepared five peptide analogues with the format ILPXKXPXXPXRR‐NH2 in which Trp‐residues 4,6,8,9,11 were replaced in all positions with X = a single non‐natural building block; N‐substituted glycine residue or nonproteinogenic amino acid. The analogues were tested for antibacterial activity against both Staphylococcus aureus American type culture collection (ATCC) 25923 and Escherichia coli ATCC 25922. We found that tryptophan is not essential in the antibacterial activity of indolicidin, and even more active analogues were obtained by replacing tryptophan with non‐natural aromatic amino acids. Using this knowledge, we then investigated a new principle for improving the antibacterial activity of small peptides. Our approach involves changing the hydrophobicity of the peptide by modifying the N‐terminus with a hydrophobic non‐natural building block. We prepared 22 analogues of indolicidin and [Phe4,6,8,9,11] indolicidin, 11 of each, carrying a hydrophobic non‐natural building block attached to the N‐terminus. Several active antibacterial analogues were identified. Finally, the cytotoxicity of the analogues against sheep erythrocytes was assessed in a haemolytic activity assay. The results presented here suggest that modified analogues of antibacterial peptides, containing non‐natural building blocks, are promising lead structures for developing future therapeutics.  相似文献   
92.
PURPOSE: ANX7-GTPase located on chromosome 10q21 is significantly altered and associated with hormone-refractory metastatic prostate cancers. Therefore, we investigated whether levels of ANX7 correlate with breast cancer progression and survival EXPERIMENTAL DESIGN: A diagnostic tumor tissue microarray containing 525 human breast tissue specimens at different stages of the disease was assayed for ANX7 using immunocytochemical methods with ANX7 monoclonal antibody. A separate prognostic tumor tissue microarray containing 553 human breast tissue specimens annotated with clinicopathological parameters was assayed for ANX7, HER2, estrogen receptor, progesterone receptor, and p53 protein. RESULTS: We report here for the first time that the expression of ANX7-GTPase is significantly enhanced and associated with the presence of metastatic disease (P < 0.0001) in the 525 human breast tissue specimens analyzed. Furthermore, using a separate 553 case retrospective prognostic tumor tissue microarray, we found that increased ANX7 expression is also significantly associated with poor overall patient survival (P < 0.014). This is particularly true when restricted to patients in whom the BRE clinical grade is 2 (P < 0.001) or for whom there is a lack of HER2 expression (P < 0.002). Finally, Cox regression analysis shows that as the expression of ANX7 rises, the probability of survival decreases by more than 10-fold for those patients with HER2-negative tumors. These latter patients represented 66% of the population affected with breast cancer in this study. CONCLUSIONS: High levels of ANX7 in tumor correlate strongly with poor survival of HER2-negative patients and the most aggressive forms of breast cancer. This is the first study to demonstrate that ANX7 antibody has the potential for development into an in vivo diagnostic and therapeutic tool. This simple and reliable immunohistochemical assay may therefore become an important biomarker for metastatic breast cancer diagnosis and management of HER2-negative breast tumor patients.  相似文献   
93.
BACKGROUND: The causes of albuminuria in patients with type 2 diabetes are heterogeneous and are scantily investigated, particularly if the patient has a lack of diabetic retinopathy. Therefore, we evaluated the structural background of albuminuria in a large consecutive group of Caucasian patients with type 2 diabetes without retinopathy. METHODS: Three hundred forty-seven consecutive patients with type 2 diabetes with persistent albuminuria (>300 mg/24 h) were recorded. Fundus photo (80%) and ophthalmoscopy were performed. Ninety-three (27%) had no retinopathy, and a kidney biopsy was performed in 52 (56%) of these patients. An insufficient tissue sample was obtained in one patient. The biopsies were evaluated by three masked nephropathologists. RESULTS: The biopsies revealed diabetic glomerulopathy in 69% of the patients (28 males and 7 females), while the remaining 31% (95% CI, 18 to 44) had either nondiabetic glomerulopathies such as glomerulonephritis (N = 7, 6 males and 1 female, 13%) or normal glomerular structure (N = 9, 7 males and 2 females, 18%). No significant differences in sex, age (56 +/- 8 vs. 53 +/- 10 years, mean SD), body mass index (30 +/- 4 vs. 31 +/- 8 kg/m2), known duration of diabetes (6 +/- 6 vs. 4 +/- 3 years), GFR (95 +/- 29 vs. 89 +/- 31 mL/min/1.73 m2), albuminuria (1304 +/- 169 to 4731 vs. 1050 +/- 181 to 5176 mg/24 hours), blood pressure (150/87 +/- 16/9 vs. 145/89 +/- 16/9 mm Hg), prevalence of hypertension (89 vs. 100%), hemoglobin A1c (8.2 +/- 1.6% vs. 9.0 +/- 2.5%), and serum total cholesterol (7.1 +/- 2.4 vs. 6.3 +/- 1.6 mmol/L) were found between patients with and without diabetic glomerulopathy. CONCLUSIONS: Albuminuric patients with type 2 diabetes without diabetic retinopathy have a prevalence of biopsies with normal glomerular structure or nondiabetic kidney diseases of approximately 30%. A separation between diabetic and nondiabetic glomerular lesions was not possible based on demographic, clinical, or laboratory data. Consequently, such patients may require further evaluation, including a kidney biopsy.  相似文献   
94.
OBJECTIVE: To evaluate the impact of zinc supplementation on the clinical course, stool weight, duration of diarrhoea, changes in serum zinc, and body weight gain of children with acute diarrhoea. DESIGN: Randomised double blind controlled trial. Children were assigned to receive zinc (20 mg elemental zinc per day) containing multivitamins or control group (zinc-free multivitamins) daily in three divided doses for two weeks. SETTING: A diarrhoeal disease hospital in Dhaka, Bangladesh. PATIENTS: 111 children, 3 to 24 months old, below 76% median weight for age of the National Center for Health Statistics standard with acute diarrhoea. Children with severe infection and/or oedema were excluded. MAIN OUTCOME MEASURES: Total diarrhoeal stool output, duration of diarrhoea, rate of weight gain, and changes in serum zinc levels after supplementation. RESULTS: Stool output was 28% less and duration 14% shorter in the zinc supplemented group than placebo (p = 0.06). There were reductions in median total diarrhoeal stool output among zinc supplemented subjects who were shorter (less than 95% height for age), 239 v 326 g/kg (p < 0.04), and who had a lower initial serum zinc (< 14 mmol/l), 279 v 329 g/kg (p < 0.05); a shortening of mean time to recovery occurred (4.7 v 6.2 days, p < 0.04) in those with lower serum zinc. There was an increase in mean serum zinc in the zinc supplemented group (+2.4 v -0.3 mumol/l, p < 0.001) during two weeks of supplementation, and better mean weight gain (120 v 30 g, p < 0.03) at the time of discharge from hospital. CONCLUSIONS: Zinc supplementation is a simple, acceptable, and affordable strategy which should be considered in the management of acute diarrhoea and in prevention of growth faltering in children specially those who are malnourished.  相似文献   
95.
The functional status of the descending motor pathways was assessed in malnourished children using transcranial electromagnetic stimulation of the cortex. Twenty children with different severities of malnutrition and 20 control subjects were studied electrophysiologically. The circular coil of a Dentac MAG 2 magnetic stimulator was applied tangentially over the vertex to stimulate the cortex. The muscle evoked potential in the children's arms was recorded from the abductor pollicis brevis muscle and in their legs from the extensor digitorum brevis muscle on both sides of the body using surface electrodes. The muscle evoked potential of the abductor pollicis brevis and extensor digitorum brevis muscles was further obtained using root stimulation by applying the coil at the cervical and lumbar spine, respectively. The indices of cortical threshold, cortical latency, and central motor conduction time (ms) were evaluated in both arm and leg muscles on both sides. The results showed an increased cortical threshold (mean (SD) 1232.5 (134.06) in the study group v 1147.5 (99.31) in the control group) for the abductor pollicis brevis muscle and for the extensor digitorum brevis muscle (1325.00 (115.70) in the study group v 1190.0 (125.24) in the control group). Similarly, significant prolongation of the central motor conduction time (ms) (study group 6.67 (0.91) v control group 5.71 (0.74)) in the abductor pollicis brevis muscle was seen in malnourished children.  相似文献   
96.
A 1993 MRC working group on phenylketonuria suggested standardising blood phenylalanine measurements by taking blood samples at the same time each day. Since it is not known how representative of a 24 hour period a single phenylalanine concentration is, the aim of this study was to investigate the 24 hour variability of plasma phenylalanine in well controlled children with phenylketonuria. Sixteen subjects, 12 girls and four boys aged 1 to 18 years, had hourly venous blood samples collected for 13 hours between 09.00 and 21.00 on one day. Serial skin puncture blood specimens were then collected at 24.00, 03.00, and 06.00 within the same 24 hour period. All food and drink was weighed. The median variation in plasma phenylalanine concentration was 155 mumol/l/day, with a minimum of 80 and a maximum of 280. The highest concentration occurred in the morning between 6.00 and 9.00 in 63% of subjects; the lowest occurred between midday and midnight in 94%. Concentrations < 100 mumol/l occurred in 46% of children below 11 years, three having concentrations < 30 mumol/l for two, six, and seven hours respectively. Three of five subjects had concentrations above the MRC guidelines for 24% of the period studied. Except in two subjects, the blood concentrations did not rise in response to phenylalanine consumption. However, the greater the quantity of protein substitute taken between waking and the 16.00 specimen, the larger the decrease in daytime phenylalanine concentration (r = -0.7030) (p < 0.005). There is therefore wide variability in phenylalanine concentrations in a 24 hour period in children with phenylketonuria which is not reflected in a single observation. Further study is needed to investigate the effects of timing of protein substitute on the stability of phenylalanine concentrations.  相似文献   
97.
Objective: Epidemiologic studies have not been able definitely to exclude that appendectomy carries a cancer risk. This study was conducted to clarify whether appendectomy is associated with a subsequent increase in cancer risk, since appendectomy is frequently an elective procedure. Methods: The present study included more than 82,000 persons who underwent appendectomy for acute appendicitis during 1977-89 according to the nation-wide Danish Hospital Discharge Register. During a follow-up interval of up to 17 years, cancer incidence was assessed by linkage to the Danish Cancer Registry and compared with the incidence in the general population of Denmark. Results: The total number of malignancies among appendectomized persons was 1.05 times higher than expected with 95 percent confidence intervals of 0.99-1.11. There was no clear significant excess of any specific cancer type. Conclusion: During a postsurgery period of nearly two decades, results of our study did not support the hypothesis that either appendectomy or acute appendicitis are likely to be associated with malignant neoplasms.  相似文献   
98.
Emergency and elective embolotherapy of various systemic arteries in 64 patients was carried out at a tertiary centre of Armed Forces. Specific indications were haemoptysis (n=43), preoperative (n=18), haematuria (n=1), epistaxis (n=1) and chemoembolization (n=1). The procedures were performed with gelfoam pellets (n=46), gelfoam pellets and absolute alcohol (n=1), polyvinyl alcohol particles (PVA) (n=14), steel coils (n=2) and Adriamycin-in-oil emulsion (n=1). Embolotherapy resulted in complete haemostasis in 37 (82.2%) out of 45 cases of haemorrhage. In eight cases (17.8%), it resulted in significant improvement. Complete haemostasis was achieved in both cases of haematuria and epistaxis. Pre-operative embolotherapy resulted in considerable reduction of peroperative blood loss in all the cases. Chemoembolization of Hepatocellular carcinoma resulted in partial regression of the tumour. The purpose of this study was to assess the efficacy, safety and reliability of vascular embolotherapy for control of life threatening haemorrhage and preoperative reduction of lesions.KEY WORDS: Embolization, Embolotherapy, Haemorrhage  相似文献   
99.
Female sterilisation is an important component of National Family Welfare Programme. The target group is best motivated during the puerperium for such a procedure. However laparoscopic sterilisation which has got some distinct advantages, is not technically feasible at this time. The authors have used a technique where the advantages of cosmetic appearance, reduced post operative morbidity and reversibility can be conferred on the puerperal women.After trying out the method individually in some cases, a formal case control study design has been made and an evaluation study has been performed in 122 cases. The technique has been found to be cosmetically more acceptable, both at clientele and peer evaluation levels (p<0.001). Though all the four parameters of post operative morbidity have shown better results for the technique evaluated as against the conventional technique, statistical significance has been achieved in two of the parameters (p<0.05).KEY WORDS: Cosmetics, Female sterilisation, Post operative morbidity  相似文献   
100.
Cooperative extension has a long‐term history of delivering family life education. Further, the organization has developed numerous research‐based resources and undertaken statewide initiatives in marriage and couples education. Most promising of all is the work of a group of extension specialists to create a practical, research‐based curriculum that may reach communities in the United States through the established network of extension educators and their collaborators. We review various family relationship models and describe how the design of the new couples' curriculum is based on those models.  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