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   3834篇
  免费   235篇
  国内免费   20篇
耳鼻咽喉   18篇
儿科学   99篇
妇产科学   40篇
基础医学   529篇
口腔科学   85篇
临床医学   288篇
内科学   901篇
皮肤病学   238篇
神经病学   236篇
特种医学   75篇
外科学   457篇
综合类   24篇
预防医学   244篇
眼科学   81篇
药学   304篇
中国医学   16篇
肿瘤学   454篇
  2023年   22篇
  2022年   33篇
  2021年   67篇
  2020年   52篇
  2019年   45篇
  2018年   66篇
  2017年   67篇
  2016年   89篇
  2015年   101篇
  2014年   129篇
  2013年   129篇
  2012年   178篇
  2011年   235篇
  2010年   101篇
  2009年   118篇
  2008年   181篇
  2007年   200篇
  2006年   213篇
  2005年   231篇
  2004年   210篇
  2003年   245篇
  2002年   232篇
  2001年   98篇
  2000年   117篇
  1999年   86篇
  1998年   54篇
  1997年   37篇
  1996年   43篇
  1995年   38篇
  1994年   36篇
  1993年   28篇
  1992年   48篇
  1991年   61篇
  1990年   46篇
  1989年   47篇
  1988年   54篇
  1987年   46篇
  1986年   47篇
  1985年   51篇
  1984年   24篇
  1983年   17篇
  1981年   13篇
  1980年   10篇
  1979年   10篇
  1978年   12篇
  1977年   17篇
  1976年   10篇
  1975年   11篇
  1974年   18篇
  1969年   11篇
排序方式: 共有4089条查询结果,搜索用时 15 毫秒
1.
Purpose: Mouse double-stranded DNA-dependent protein kinase (DNA-PK) activity is heat sensitive. Recovery of heat-inactivated DNA repair activity is a problem after combination therapy with radiation and heat. We investigated the mechanism of recovery of heat-inactivated DNA-PK activity.

Methods: Hybrid cells containing a fragment of human chromosome 8 in scid cells (RD13B2) were used. DNA-PK activity was measured by an in vitro assay. Immunoprecipitation of the nuclear extract was performed with an anti-Ku80 antibody. Proteins co-precipitated with Ku80 were separated by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis and detected by Western blotting using anti-heat shock protein (HSP)72 and anti-heat shock cognate protein (HSC)73 antibodies. HSC73 was overexpressed with the pcDNA3.1 vector. Short hairpin (sh)RNA was used to downregulate HSC73 and HSP72.

Results: The activity of heat-inactivated DNA-PK recovered to about 50% of control during an additional incubation at 37?°C after heat treatment at 44?°C for 15?min in the presence of cycloheximide (which inhibits de novo protein synthesis). Maximal recovery was observed within 3?h of incubation at 37?°C after heat treatment. Constitutively expressed HSC73, which folds newly synthesized proteins, reached maximal levels 3?h after heat treatment using a co-immunoprecipitation assay with the Ku80 protein. Inhibiting HSC73, but not HSP72, expression with shRNA decreased the recovery of DNA-PK activity after heat treatment.

Conclusions: These results suggest that de novo protein synthesis is unnecessary for recovery of some heat-inactivated DNA-PK. Rather, it might be reactivated by the molecular chaperone activity of HSC73, but not HSP72.  相似文献   

2.

Background

There were few studies assessed the postoperative sarcopenia in patients with cancers. The objective of present study was to assess whether postoperative development of sarcopenia could predict a poor prognosis in patients with adenocarcinoma of esophagogastric junction, (AEG) and upper gastric cancer (UGC).

Methods

Patients with AEG and UGC who were judged as non-sarcopenic before surgery were reassessed the presence of postoperative development of sarcopenia 6 months after surgery. Patients were divided into the development group or non-development group, and clinicopathological factors and prognosis between these two groups were analyzed.

Results

The 5-year overall survival rates were significantly poorer in the development group than non-development group (68.0% vs. 92.6%, P?=?0.0118). Multivariate analyses showed that postoperative development of sarcopenia was an independent prognostic factor for poor overall survival (P?=?0.0237).

Conclusions

Postoperative development of sarcopenia was associated with a poor prognosis in patients with AEG and UGC.  相似文献   
3.
Circulating white blood cell (WBC) and platelet (PLT) counts are widely available and inexpensive cellular biomarkers of systemic inflammation and have been associated with a risk of cardiovascular disease, cancer, and mortality. Melatonin may reduce systemic inflammation through its direct and indirect antioxidative effect; however, the associations of melatonin secretion with systemic inflammation remain unclear. In this cross‐sectional study on 1088 elderly individuals (mean age, 71.8 years), we measured overnight urinary 6‐sulfatoxymelatonin excretion (UME) and WBC and PLT counts as indices of melatonin secretion and systemic inflammation, respectively. UME was naturally log‐transformed for linear regression models because of skewed distribution (median, 6.8 μg; interquartile range, 4.1–10.6 μg). Univariate models revealed that higher log‐transformed UME levels were significantly associated with lower WBC and PLT counts (= 0.046 and 0.018). After adjusting for potential confounding factors significantly associated with WBC or PLT counts, higher log‐transformed UME levels were significantly associated with lower WBC and PLT counts (WBC: β, ?0.143; 95% confidence interval, ?0.267 to ?0.020; = 0.023; PLT: β, ?6.786; 95% confidence interval, ?12.047 to ?1.525; = 0.012). Furthermore, the adjusted mean differences in WBC and PLT counts between the lowest and highest UME tertile groups were 0.225 × 109/L and 9.480 × 109/L, respectively. In conclusion, melatonin secretion was significantly and inversely associated with WBC and PLT counts in the general elderly population. The associations were independent of several major causes of systemic inflammation, including aging, obesity, smoking, hypertension, diabetes, and physical inactivity.  相似文献   
4.
High blood pressure (BP) is a major determinant of cardiovascular events in obesity. The beta2- and beta3-adrenoceptor polymorphisms are associated with obesity and hypertension. In the present study, we examine the relationships of beta2- and beta3-adrenoceptor polymorphisms with further weight gain-induced BP elevation in obese subjects. Changes in BP, body weight, total body fat-mass, waist-to-hip ratio, plasma norepinephrine (NE) and leptin levels, and beta2(Arg16Gly)- and beta3(Trp64Arg)-adrenoceptor polymorphisms were measured periodically over a 5-year period in 55 entry obese (body mass index [BMI]> or =25.0 kg/m(2)) normotensive (BP<140/90 mmHg) men. BP elevation and weight gain were defined as > or =10% increases from entry levels over 5 years in mean BP or BMI. Obese subjects with weight gain, BP elevation or weight gain-induced BP elevation had higher frequencies of the Gly16 allele of Arg16GIy and Arg64 allele of Trp64Arg. Subjects carrying the Gly16 or Arg64 alleles had significantly greater total fat-mass and waist-to-hip ratio at entry and over a 5-year period compared to the subjects who did not carry these polymorphisms. Subjects carrying the Gly16 allele had similar levels of plasma NE, higher levels of plasma leptin and a lower slope of the regression lines between plasma leptin and NE levels. Those carrying the Arg64 allele had higher plasma NE levels at entry and over a 5-year period compared to the subjects without the Arg64 allele, but plasma leptin levels and slopes were similar. The findings demonstrate that the Arg64 allele of the beta3-adrenoceptor polymorphisms relates to weight gain-induced BP elevation accompanying high plasma NE (heightened sympathetic activity) in obese men. The Gly16 allele of the beta2-adrenoceptor polymorphisms links to weight gain-induced BP elevation associated with leptin resistance. beta2- and beta3-adrenoceptor polymorphisms could predict the future BP elevation and further weight gain-induced BP elevation in originally obese subjects.  相似文献   
5.
Background: We evaluated the endoscopic microvascular architecture of the gastric mucosa in portal hypertension patients using the prototype of narrow band imaging (NBI). Material and Methods: The study included 103 Helicobacter pylori‐negative patients with chronic liver disease (22 without portal hypertension (group 1), 81 with portal hypertension (group 2)). Results: (i) Abnormality of collecting venules, reddening mucosa, red spots, a mosaic‐like pattern, and gastric antral vascular ectasia (GAVE) were observed on the gastric mucosa, and an obscure change in collecting venules (73% vs 14%; P < 0.001), reddening mucosa (49% vs 5%; P < 0.001), red spots (36% vs 5%; P < 0.01) and a mosaic‐like pattern (40% vs 5%; P < 0.01) were more frequently observed in group 2 than in group 1. (ii) On magnifying endoscopy with NBI, the mucosa with an obscure change in collecting venules was demonstrated as dilation of the capillaries surrounding the gastric pits in various degrees, and reddening mucosa was observed as extended and swollen gastric pits and various degrees of dilated and convoluted capillaries surrounding the gastric pits. Red spots were demonstrated as extended and swollen gastric pits, dilated and convoluted capillaries surrounding the gastric pits, and intramucosal hemorrhage around these capillaries. GAVE was recognized as partial and marked dilatation of the capillaries surrounding the gastric pits. Conclusion: Abnormality of collecting venules, swelling of gastric pits, dilatation of capillaries surrounding the gastric pits, intramucosal hemorrhage around capillaries, and partial and marked dilatation of the capillaries were observed on the gastric mucosa in portal hypertension patients.  相似文献   
6.
The efficacy of Bestatin as adjuvant immunochemotherapy for patients with resectable gastric cancer was investigated. Ninety-six patients with similar background factors were randomized into two groups; a control group and an experimental group, the patients in the experimental group receiving a daily oral dose of 60 mg Bestatin over a long period. All 96 patients were treated with a bolus intravenous injection of mitomycin C (MMC) plus oral administration of tegafur (FT-207, FT). The survival rate of the patients in the MMC + FT + Bestatin group was more favorable than that of the patients in the MMC + FT group, but the difference was not statistically significant. The survival rates of the MMC + FT + Bestatin group patients in the stratification of stage III + IV and positive histological serosal invasion, ps(+), were significantly superior to those of the MMC + FT group patients (Logrank test: p less than 0.05). Moreover, in patients with positive histological serosal invasion, the recurrence of peritoneal dissemination was significantly suppressed in the MMC + FT + Bestatin group.  相似文献   
7.
The effect of ketamine infusion to control the intractable pain which had not responded to ordinary procedures in 12 patients with advanced cancer were evaluated. Ketamine 250 mg or 500 mg in 500 ml of transfusion fluid with or without 10 to 20 mg of droperidol was administered intravenously at the rate of 3 to 20mg of ketamine per hour. The pain scores by VAS in most of the patients decreased significantly with an averaged value of 8.3 before the treatment to 1 during the procedure. The durations of this therapy lasted from over 6 hours to 48 days. Slight disorientation in one patient and drowsiness in 5 were seen during the infusion. No cardiovascular or respiratory complications were noted. These results indicate that ketamine infusion is a useful therapeutic procedure to treat cancer pain which resist ordinary pain therapies.  相似文献   
8.
This study was performed to examine the pattern of Superoxide (O 2 ·) generation from leukocytes using the O 2 · specific chemiluminescence (CL) method.Cypridina luciferin analog, 2-methyl-6-(p-methoxyphenyl)-3,7-dihydroimidazo[1,2-alpha]pyrazin-3-one (MCLA) was used as a CL probe. The appropriate conditions of the MCLA method was first determined for the evaluation of the time course of O 2 · generation by leukocytes. The time course of O 2 · generation obtained by the MCLA-CL system was compared with that by the luminol-dependent CL, electron spin resonance (ESR)/spin trapping, and cytochromec systems. Following stimulation by three different stimulants (PMA, OZ, FMLP), leukocytes continuously generated O 2 · for up to 5 h in the MCLA-CL system, irrespective of the kind of stimulation. The curves obtained by generation ceased more rapidly in the luminol-CL, ESR/spin trapping, and cytochromec systems. A 50% activity of the initial value was observed at 70 min in the MCLA-CL system, but 30, 10 and 35 min in the other systems, respectively. The CL or O 2 · generation value decreased to less than 1% (possible termination) at 300, 90, 120 and 180 min, respectively. With the exception of ESR studies with OZ, the cell viability was not significantly affected in any of the trials. These results indicate that leukocytes can generate O 2 · much longer than previously estimated and that the MCLA-CL-system is the most suitable system for the measurement of the O 2 · generation by leukocytes.  相似文献   
9.
We evaluated a 1-year course of a newly developed immunosuppressant, mizoribine (at a dosage of 3 mg/kg body weight per day), in nine children with steroid-dependent nephrotic syndrome. Steroid treatment could be discontinued in two patients and the maintenance dosage of steroid could be reduced to less than half of that given before mizoribine therapy in a third. There were no beneficial effects in the remaining six patients. No adverse effects of mizoribine were observed during the course of therapy. Received September 20, 1996; received in revised form and accepted April 24, 1997  相似文献   
10.
An elderly case of systemic lupus erythematosus (SLE) with suspected hemolytic anemia was experienced. A 70 year-old female was admitted to our hospital on December 31 with complaints of herpetic eruption. She complained of arthralgia since 3 month prior to her admission. The positive findings on examination were skin eruption in the left chest, a systolic heart murmur and a palpable elastic hard liver. Laboratory data showed raised erythrocyte sedimentation rate of 149 mm per hour, decreased Hb (10.1 g/dl), decreased hematocrit (30.0%), increased reticulocytes (33%1000), decreased thrombocytes (73,000/mm3), increased gamma-globulin (33%) and positive rheumatoid factor. During admission, she developed anemia. A stool test for occult blood was negative. The haptoglobin was 38.8 mg/dl and bone marrow aspiration showed increased erythropoiesis, suggesting features of immune hemolytic anemia, except she was negative on Coomb'test. Eye fundi were similar to case of typical bleeding observed in SLE. Concerning immunological findings, the antinuclear factor was x 1280 and the anti-dsDNA antibody was x 80, on which a diagnosis of SLE was based. She experienced numbness of the left arm and developed left hemiparesis 2 days later. Therapy with 15 mg/day prednisone obtained a good response and anemia, abnormal immunological findings and hemiparesis disappeared.  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