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   3253篇
  免费   319篇
  国内免费   20篇
耳鼻咽喉   28篇
儿科学   124篇
妇产科学   58篇
基础医学   354篇
口腔科学   55篇
临床医学   468篇
内科学   784篇
皮肤病学   121篇
神经病学   140篇
特种医学   168篇
外科学   551篇
综合类   135篇
现状与发展   30篇
一般理论   2篇
预防医学   225篇
眼科学   26篇
药学   124篇
中国医学   4篇
肿瘤学   195篇
  2023年   184篇
  2021年   34篇
  2020年   61篇
  2019年   44篇
  2018年   74篇
  2017年   59篇
  2016年   52篇
  2015年   80篇
  2014年   116篇
  2013年   115篇
  2012年   119篇
  2011年   130篇
  2010年   108篇
  2009年   117篇
  2008年   101篇
  2007年   114篇
  2006年   94篇
  2005年   78篇
  2004年   69篇
  2003年   72篇
  2002年   89篇
  2001年   69篇
  2000年   66篇
  1999年   73篇
  1998年   53篇
  1997年   72篇
  1996年   57篇
  1995年   50篇
  1994年   49篇
  1993年   44篇
  1992年   56篇
  1991年   58篇
  1990年   69篇
  1989年   68篇
  1988年   62篇
  1987年   47篇
  1986年   37篇
  1985年   53篇
  1984年   39篇
  1983年   27篇
  1982年   29篇
  1979年   55篇
  1978年   33篇
  1977年   27篇
  1976年   42篇
  1975年   40篇
  1974年   27篇
  1971年   26篇
  1970年   29篇
  1967年   27篇
排序方式: 共有3592条查询结果,搜索用时 32 毫秒
11.
12.
Cryopreservation of human zygotes and embryos has been routinely performed by in-vitro fertilization clinics for many years. Karran and Legge (1996) first reported that formaldehyde (FA) present in the cryoprotective solutions can have a deleterious effect on mouse oocytes. FA is a cytotoxic, carcinogenic and mutagenic chemical. The effect of FA on mouse zygotes was investigated. In addition, the concentrations of FA in propanediol (PROH) obtained from various sources were determined. Pooled 1-cell embryos were dispensed into droplets of modified Ham's F10 or human tubal fluid containing various concentrations of FA. Since bovine serum albumin (BSA) may minimize toxicity additional trials were done as above in the absence of BSA. FA concentration in the standard 1.5 M PROH, from different sources in water, was measured in the same assay using a standard curve of 0-100 microM FA. FA in a complex medium had a significant deleterious effect on embryo development and hatching but only at 1 mM concentration (P < 0.000001; see Tables I-III). There was no significant effect of FA at 100 microM. However, in a simple medium even 50 microM FA decreased embryo hatching. FA was present in 1.5 M PROH from different sources (range 1.0-35.3 microM concentration). It appears that FA concentrations do not increase with storage because FA concentrations were low even after opening and storage for 3 years on the shelf. This suggests that FA is a contaminant during the manufacturing process and may vary from manufacturer to manufacturer and batch to batch. Until further studies are done to confirm the lack of toxicity to embryos during cryopreservation (with or without FA scavengers) it may be prudent to screen all batches of cryoprotectants for FA as part of quality control.   相似文献   
13.
Hearing impairment is the most frequent sensory defect in children, with a genetic basis in about 50% of cases. Several point mutations and deletions in mitochondrial DNA (mtDNA) have been identified in non-syndromic sensorineural hearing loss (NSSNHL). Beside the frequent A1555G mutation, a number of mutations in tRNAs have been reported recently, but their incidence remains unknown. We identified the T7511C mutation in the tRNASer(UCN) gene in two French families with isolated deafness. Maternal transmission was obvious in both. The 15 patients with hearing impairment exhibited a variable disease phenotype in terms of onset, severity, and progression. T7511C was present in all the patients screened. Homoplasmic and heteroplasmic levels were observed and did not correlate with the severity of the disease. T7511C was also present in 12 hearing offspring of the oldest deaf mothers, confirming the existence of modulatory factors. Our data suggest that this mtDNA mutation should be screened for in all cases of familial NSSNHL compatible with maternal transmission.  相似文献   
14.
The group JK diphtheroid organism is a multiply resistant opportunistic pathogen which infects immunocompromised patients sporadically. We describe the first reported outbreak of JK diphtheroid infections, in which four cases of bacteremia and one Hickman catheter site infection occurred during 4 weeks on a hematology ward. On this ward, JK diphtheroid was recovered from 17 of 39 patients, 10 of 17 30-ft3 (0.840-m3) air samples, surfaces in 9 of 13 patient rooms, and hands of 4 of 22 personnel. Previously identified risk factors for JK diphtheroid sepsis (male gender, broad-spectrum antibiotic therapy, granulocytopenia, and prolonged hospital stay) were present in infected patients but did not distinguish them from patients who were only colonized. Emphasis on aseptic practices was associated with termination of the outbreak and negative hand cultures from personnel, despite continued patient colonization and environmental contamination.  相似文献   
15.
16.
In order to study the nephropathy associated with experimental streptozotocin diabetes, serila morphologic, ultrastructural, immunohistologic, and functional studies were done in diabetic Lewis rats to study the course of the nephropathy. Early in the course of diabetes, these animals developed an increase in mesangial matrix, with electron-dense material, IgG, and C3 in the mesangium. These alterations were progressive. Mesangial bars, proximal tubular vacuolization, and myeloid bodies were also present. Progressive increase in protein excretion and increase in creatinine clearance were observed. Hyperglycemia was accompanied by weight loss, persistent glycosuris, hyperphosphaturia, and hypercalcuria. Urinary glomerular basement membrane-like protein and major urinary protein were decreased. Normal age-matched controls showed no abnormalities. Some of the changes observed in diabetic rats are present in human diabetes.  相似文献   
17.
Four multicentre double blind trials (two studies comparing placebo to a marketed activating drug and two comparing placebo to a new drug with central adrenergic modulating properties) were pooled, totalling 77 placebo Ss, 30 reference drug Ss and 73 study drug Ss. The AMDP-4 and -5 scales were filled out at day 0 and 7 by trained raters. Four statistical analyses were performed on the pre- vs. postdrug differences: an analysis of variance, a principal components factor analysis, a discriminant analysis and a cluster analysis. The results indicate that 9 out of the 14 AMDP factor scores significantly decrease within 1 week while the factor Mania-Agitation increases, without differences between both active compounds; on the item level, the "inhibition of drive" is specifically improved by the study drug; the discriminant analysis confirms that the two most improved items are "Inhibition of drive" and "Hopelessness". Three factor scores significantly improve on placebo (Depression, Retardation, Psycho-organic Symptoms), which points to the necessity of placebo-controlled studies in clinical trials of new drugs.  相似文献   
18.
The meta-analysis was performed to assess the efficacy and safety of daily oral L-arginine and phosphodiesterase type 5 inhibitors (PDE5Is) alone or combination in treating patients with erectile dysfunction (ED). We performed a search of randomised controlled trials in the following databases: PubMed, EMBASE and Cochrane Library databases. Four articles including 373 patients were studied. Erectile functions were significantly improved in three therapy groups compared with baseline. Patients who received the combination of L-arginine and PDE5Is showed significant improvement compared to those treated with L-arginine and PDE5Is alone, as assessed by sexual function index (p <0.00001 and p =0.005, respectively) and total testosterone (p <0.00001 and p =0.0007, respectively). Furthermore, patients who treated with PDE5Is alone exhibited the better efficacy than those treated with L-arginine alone in respects of sexual function index (p <0.00001) and total testosterone (p =0.0001). However, the combination of L-arginine and PDE5Is had no obvious difference relative to PDE5Is alone in terms of various adverse events (AEs). Conclusively, compared with monotherapy, the combination of L-arginine and PDE5Is showed a greater improvement of sexual function and total testosterone, and did not significantly increase the AEs. Besides, PDE5Is alone revealed a better effect than those treated with L-arginine alone for patients with ED.  相似文献   
19.
In the past 40 years, the prevalence of eating disorders (ED) in China has shown an increasing trend, leading to an urgent need to develop efficient treatment modes and methods. Since the beginning of the new century, the diagnosis, treatment, and research of ED in China have been under development. This article gives an introduction and commentary on the treatment modes, treatment methods and their applications in ED in China. There are two main treatment forms for ED until now, that is, inpatient treatment and outpatient treatment. Inpatient treatment is recommended as the first choice. Since 2008, clinical psychotherapies such as cognitive behavioral therapy (CBT), dialectical behavioral therapy (DBT), and family-based treatment (FBT), which are effective for pathological symptoms of ED, have been introduced into China and developed clinically. Group CBT and group DBT for patients with ED and group FBT for caregivers might be the most efficient psychotherapy in China nowadays. A multi-family FBT support group could be developed as the basic treatment of ED patients. Although these new types of psychotherapy have observed effectiveness in clinical application, the Randomized Controlled Trials (RCT) are rare and need to be developed.  相似文献   
20.
Transit-time ultrasound methods were used to measure blood flow in 37 patients undergoing carotid endarterectomy. Internal carotid flow before (ICFbef) and after (ICFaft) endarterectomy was measured with a 6 mm perivascular probe, and Javid shunt flow (SF) was measured with a clamp-on probe. For the entire group ICFbef averaged 117±67 ml/min and ICFaft was 173±67 ml/min. Shunt flow averaged 123±51 ml/min. The differences between ICFbet and ICFaft and between SF and ICFaft were significant (ANOVA,p<0.01) but the difference between ICFbef and SF was not. The relationship between ICFbef and SF appeared to define two groups of patients. Those in whom SF was greater than ICFbef (SF > ICFbef) had more stenosis evident on preoperative arteriograms (64.7%±14.55% maximum single diameter stenosis) and a greater average increase in ICF (151%±159%) than those with SF ICFbef (43.3%±20.9% stenosis and 34%±54% increase in ICF), suggesting that the relationship between SF and ICFbef defines groups with different hemodynamic responses. The similarity between SF and ICFbef indicates that Javid shunt flow offers adequate protection from cerebral ischemia. A practical benefit of the shunt clamp-on flow probe is the ability afforded to recognize shunt occlusions.Presented at the Twelfth Annual Meeting of the Southern California Vascular Surgical Society, Coronado, Calif., September 17–19, 1993.  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