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   799篇
  免费   52篇
  国内免费   7篇
耳鼻咽喉   4篇
儿科学   34篇
妇产科学   3篇
基础医学   83篇
口腔科学   33篇
临床医学   69篇
内科学   134篇
皮肤病学   18篇
神经病学   29篇
特种医学   134篇
外科学   97篇
综合类   74篇
一般理论   1篇
预防医学   46篇
眼科学   4篇
药学   62篇
中国医学   1篇
肿瘤学   32篇
  2021年   18篇
  2020年   6篇
  2019年   6篇
  2018年   8篇
  2016年   15篇
  2015年   14篇
  2014年   17篇
  2013年   32篇
  2012年   41篇
  2011年   19篇
  2010年   32篇
  2009年   37篇
  2008年   21篇
  2007年   17篇
  2006年   29篇
  2005年   19篇
  2004年   12篇
  2003年   16篇
  2002年   13篇
  2001年   16篇
  2000年   20篇
  1999年   24篇
  1998年   36篇
  1997年   29篇
  1996年   25篇
  1995年   16篇
  1994年   23篇
  1993年   24篇
  1992年   16篇
  1991年   11篇
  1990年   10篇
  1989年   20篇
  1988年   20篇
  1987年   14篇
  1986年   15篇
  1985年   9篇
  1984年   13篇
  1983年   6篇
  1982年   12篇
  1981年   12篇
  1980年   15篇
  1978年   9篇
  1977年   7篇
  1976年   13篇
  1975年   5篇
  1913年   3篇
  1907年   3篇
  1905年   3篇
  1897年   3篇
  1889年   3篇
排序方式: 共有858条查询结果,搜索用时 31 毫秒
1.
OBJECTIVE: Nocturnal enuresis is a common pediatric problem, the etiology of which is unclear. In recent years, various studies have been published stating that children with nocturnal enuresis exhibit growth and skeletal maturation retardation. METHODS: In this cross-sectional study, we included 27 patients (16 boys, 11 girls) between the ages of 6 and 14 years who had presented with primary nocturnal enuresis (PNE) complaints. We included in the evaluation 19 healthy subjects (12 boys, 7 girls), who were the siblings of the children with PNE, as the control group. RESULTS: The patients in both groups were similar in chronological age, bone age, height and weight, with no significant difference between groups (P>0.05). CONCLUSION: The two groups in our study consisted of the same genetic background. Thus, our results were found to be different from the previous studies. We have concluded that there is no direct relationship between enuresis nocturnal and skeletal maturation.  相似文献   
2.
3.
The effect of cirrhosis on the accuracy of ultrasonography and scintigraphy in the diagnosis of hepatocellular carcinoma (HCC) has not been established. We have therefore studied the findings on ultrasound and scintigraphy in four groups of patients. Fourteen had HCC and cirrhosis, 13 had HCC but no cirrhosis, 53 had cirrhosis but no HCC and 31 had evidence neither of cirrhotic nor malignant liver disease. The accuracies of a positive interpretation of HCC on ultrasound and scintigraphy in the absence of cirrhosis were 85% and 66% respectively (NS), but fell (significantly in the case of scintigraphy: p less than 0.05) to 80% and 31% respectively in the presence of cirrhosis (p less than 0.01). The poorer performance of scintigraphy in the presence of cirrhosis was a result both of its lower sensitivity (50% compared with 85%) and the greater frequency of false positives (28% vs 5%: p less than 0.001). The accuracy of a negative interpretation of HCC on scintigraphy in the absence of cirrhosis was 96% but fell to 84% in the presence of cirrhosis, whereas on ultrasound it remained the same (96%). In conclusion, we recommend ultrasound in preference to scintigraphy as a more accurate technique for the diagnosis of HCC in the presence of cirrhosis.  相似文献   
4.
5.
High serum fluoride (F-) in patients with chronic renal failure (CRF) and end-stage renal disease (ESRD) is associated with risk of renal osteodystrophy and other bone changes. This study was done to determine F- in normal healthy controls and patients with ESRD on haemodialysis (HD) or peritoneal dialysis (PD). Seventeen healthy controls (12 males, 5 females) and 39 ESRD patients on dialysis (17 males, 22 females) were recruited in the study in a community with 47.4 +/- 3.28 microM/l (range 44-51 microM/l) of F- content in drinking water. Control subjects showed a mean serum F- concentration of 1.08 +/- 0.350 microM/l. Males in control group showed slightly higher F- levels (1.15 +/- 0.334, range 0.55-1.9 microM/l) than females (0.92 +/- 0.370, range 0.6-1.5 microM/l). Mean serum F- concentration did not correlate significantly with age and sex among control subjects, whereas such correlation was observed in patients with ESRD on dialysis. Mean serum F- concentration was significantly higher in patients on dialysis (2.67 +/- 1.09, range 0.8-5.2 microM/l) than normal controls. When grouped according to sex, the mean serum F- concentration in males (3.05 +/- 1.04, range 1.8-5.2 microM/l) was significantly higher than females (2.38 +/- 1.08, range 0.8-5.2 microM/l). When patients were grouped according to age, it was observed that F- concentration was significantly higher in patients with age groups 21-70 (2.86 +/- 1.05) than those with age group 13-20 years (1.42 +/- 0.531). Thus F- concentration correlated with age and sex, being higher in males and above 20 years. Despite appreciable clearance of F- (39-90%) across the peritoneum, patients on CAPD showed higher serum F- concentration than those on HD (3.1 +/- 1.97 vs 2.5 +/- 1.137 microM/l). Of the total 39 patients on dialysis 39% had their serum F- concentration above 3.0 microM/l, posing the risk of renal osteodystrophy.   相似文献   
6.
We present data on 10 patients (5 men and 5 women, aged 21-56 yrs) with end-stage liver disease or tumour who underwent orthotopic liver transplantation at Groote Schuur Hospital between October 1988 and June 1991. Standard surgical techniques were used for procuring the donor liver, the recipient hepatectomy and the implantation of the liver. The venovenous bypass method was used in all but 2 patients. Postoperative immunosuppression was usually achieved with cyclosporin, azathioprine and low-dose steroids. Six patients were treated with prophylactic OKT3. Rejection episodes were treated with bolus doses of intravenous steroids. The indications for liver transplantation included chronic active hepatitis progressing to cirrhosis (5), biliary cirrhosis in association with inflammatory bowel disease (1), sclerosing cholangitis (2), alpha 1-antitrypsin deficiency (1), and tumour (1). All patients with chronic liver disease had experienced at least one complication, examples of which included encephalopathy, bacterial peritonitis, ascites, variceal bleeding and septicaemia. Serious postoperative complications included acute rejection of the transplanted liver, renal and liver failure that responded to intensive care support and medical management. One patient died on the 11th postoperative day with complications of bleeding oesophageal ulcer, shock and fungaemia. The remaining patients are alive and well 1-31 months after transplantation.  相似文献   
7.
Spontaneous apoptosis in germinal-centre (GC) B cells can be prevented by treatment with anti-immunoglobulin (Ig). By contrast, susceptible group-I Burkitt lymphoma (BL) cells can be driven to apoptosis by anti-Ig. The second-messenger pathways involved in the regulation of apoptosis in GC B lymphocytes and in BL cell lines were studied using pharmacological agonists or inhibitors of intracellular calcium ([Ca2+]i) and protein kinase C (PKC). Anti-Ig was found to mobilize Ca2+ in group-I cells. Pre-incubation with the Ca2+ chelator EGTA partially reduced apoptosis induced by anti-Ig or by Ca2+ ionophore in group-I BL cells. Activation of PKC with phorbol ester reduced such Ca(2+)-driven programmed cell death (PCD) to control levels of apoptosis. Apoptosis in group-I BL cell lines could also be triggered by the kinase inhibitors staurosporine and Ro-31-8220 at concentrations selective for PKC activity. Expression of the bcl-2 protein in BL group-I cells following gene transfer affords protection from apoptosis induced by ionomycin or anti-Ig. In the present study, bcl-2 was additionally found to protect from apoptosis driven by staurosporine. The high levels of spontaneous apoptosis exhibited by normal GC B cells were reduced, but not abrogated, by co-culture with phorbol ester. These results indicate that, in group-I BL cells, imbalance in the phosphoinositide pathway of signalling, in favour of [Ca2+]i and away from PKC, results in apoptosis: constitutive phosphorylation of key proteins by PKC may therefore suppress apoptosis in BL as well as in GC B cells.  相似文献   
8.
Pre-clerking of all patients undergoing elective general surgical operations was introduced at our hospital in an attempt to reduce an unacceptably high operation cancellation rate. A prospective audit has been performed on the effect of this policy on the cancellation rate. Before the introduction of pre-clerking there was a marked seasonal variation in the number of patients who failed to attend for surgery, which could be explained by absence on holiday. This seasonal variation disappeared after the start of pre-clerking clinics, but there has been no reduction in the number of cancellations for medical reasons.  相似文献   
9.
X-linked spinal and bulbar muscular atrophy (SBMA) is caused by a CAG repeat expansion in the first exon of the androgen receptor (AR) gene. Disease-associated alleles (37-66 CAGs) change in length when transmitted from parents to offspring, with a significantly greater tendency to shift size when inherited paternally. As transgenic mice carrying human AR cDNAs with 45 and 66 CAG repeats do not display repeat instability, we attempted to model trinucleotide repeat instability by generating transgenic mice with yeast artificial chromosomes (YACs) carrying AR CAG repeat expansions in their genomic context. Studies of independent lines of AR YAC transgenic mice with CAG 45 alleles reveal intergenerational instability at an overall rate of approximately 10%. We also find that the 45 CAG repeat tracts are significantly more unstable with maternal transmission and as the transmitting mother ages. Of all the CAG/CTG repeat transgenic mice produced to date the AR YAC CAG 45 mice are unstable with the smallest trinucleotide repeat mutations, suggesting that the length threshold for repeat instability in the mouse may be lowered by including the appropriate flanking human DNA sequences. By sequence-tagged site content analysis and long range mapping we determined that one unstable transgenic line has integrated an approximately 70 kb segment of the AR locus due to fragmentation of the AR YAC. Identification of the cis - acting elements that permit CAG tract instability and the trans -acting factors that modulate repeat instability in the AR YAC CAG 45 mice may provide insights into the molecular basis of trinucleotide repeat instability in humans.   相似文献   
10.
The relative preference for sodium solutions and water was observed during a succession of estrous cycles in housed sheep. The luteal phase of the cycle was associated with statistically significant rises of sodium preference compared with the 6 days following estrus. These reflected changes in the intake both of sodium and water. The similar pattern with both bicarbonate and chloride suggests that it is the acceptability of the sodium which changes. The results are discussed in relation to sodium appetite and electrolyte homeostasis. The possible significance of any similar changes during the menstrual cycle is considered.  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