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   5803篇
  免费   289篇
  国内免费   35篇
耳鼻咽喉   53篇
儿科学   82篇
妇产科学   82篇
基础医学   667篇
口腔科学   118篇
临床医学   339篇
内科学   1729篇
皮肤病学   158篇
神经病学   446篇
特种医学   241篇
外科学   913篇
综合类   26篇
预防医学   161篇
眼科学   69篇
药学   398篇
中国医学   28篇
肿瘤学   617篇
  2024年   11篇
  2023年   43篇
  2022年   65篇
  2021年   131篇
  2020年   92篇
  2019年   83篇
  2018年   121篇
  2017年   111篇
  2016年   133篇
  2015年   155篇
  2014年   169篇
  2013年   194篇
  2012年   353篇
  2011年   410篇
  2010年   211篇
  2009年   199篇
  2008年   332篇
  2007年   373篇
  2006年   336篇
  2005年   339篇
  2004年   343篇
  2003年   397篇
  2002年   361篇
  2001年   98篇
  2000年   66篇
  1999年   102篇
  1998年   74篇
  1997年   48篇
  1996年   64篇
  1995年   44篇
  1994年   73篇
  1993年   43篇
  1992年   70篇
  1991年   60篇
  1990年   47篇
  1989年   40篇
  1988年   37篇
  1987年   52篇
  1986年   27篇
  1985年   28篇
  1984年   21篇
  1983年   11篇
  1982年   21篇
  1981年   17篇
  1980年   17篇
  1979年   16篇
  1977年   13篇
  1975年   7篇
  1971年   9篇
  1969年   9篇
排序方式: 共有6127条查询结果,搜索用时 15 毫秒
971.
Fear is one of the most potent emotional experiences and is an adaptive component of response to potentially threatening stimuli. On the other hand, too much or inappropriate fear accounts for many common psychiatric problems. Cumulative evidence suggests that the amygdala plays a central role in the acquisition, storage and expression of fear memory. Here, we developed an inducible striatal neuron ablation system in transgenic mice. The ablation of striatal neurons in the adult brain hardly affected the auditory fear learning under the standard condition in agreement with previous studies. When conditioned with a low-intensity unconditioned stimulus, however, the formation of long-term fear memory but not short-tem memory was impaired in striatal neuron-ablated mice. Consistently, the ablation of striatal neurons 24 h after conditioning with the low-intensity unconditioned stimulus, when the long-term fear memory was formed, diminished the retention of the long-term memory. Our results reveal a novel form of the auditory fear memory depending on striatal neurons at the low-intensity unconditioned stimulus.  相似文献   
972.

Purpose

To evaluate the effect of flip angle on volume flow rate measurements obtained with nontriggered phase‐contrast magnetic resonance imaging (MRI) in vivo.

Materials and Methods

We prospectively measured volume flow rates of the bilateral internal carotid artery and the basilar artery with cine and nontriggered phase‐contrast MRI. For nontriggered phase‐contrast imaging, flip angles of 4, 15, 60, and 90° were used for 40 volunteers and of 8, 15, and 30° for 54 volunteers. Lumen boundaries were semiautomatically determined by pulsatility‐based segmentation using cine phase‐contrast MRI. Identical lumen boundaries were used for nontriggered phase‐contrast imaging.

Results

The ratio of volume flow rate obtained with nontriggered phase‐contrast imaging to that obtained with cine phase‐contrast imaging significantly increases with an increase in the flip angle. The mean ratios lie within a relatively narrow range of ±15% with a wide range of flip angles of 8–90°. As the flip angle increases, ghost artifacts become prominent and signal‐to‐noise and contrast‐to‐noise ratios increase.

Conclusion

Flip angles between 8 and 60° are most appropriate for nontriggered phase‐contrast MR measurements in the internal carotid and the basilar artery. J. Magn. Reson. Imaging 2009;29:1218–1223. © 2009 Wiley‐Liss, Inc.  相似文献   
973.
Ketogenic diets, which are carbohydrate-restricted high-fat diets, may have therapeutic effects on various diseases, including cancer. However, ketogenic diets are often not standardized and, therefore, results are difficult to interpret. We previously investigated the usefulness of ketogenic diets in cancer therapy, where ketogenic formulas (KF) were used as supplements to enhance blood ketone bodies; however, the amount of KF was determined empirically with reference to blood ketone bodies levels. Here, to determine a standardized optimal amount of KF, we investigated temporal changes in blood ketone bodies (acetoacetic acid (AcAc), β-hydroxybutyrate (BHB)) and safety in 20 healthy individuals when KF was taken repeatedly under the conditions of a ketogenic diet (UMIN000034216). The diurnal variation in total ketone bodies, and AcAc and BHB levels significantly increased after lunch and after dinner, on the 4th day of KF administration. There were no significant safety issues related to KF in the context of anthropometric, metabolic, nutritional, urological and gastrointestinal parameters. In addition, ketogenic diets lead to changes in gut microbiota. KF showed a decrease in phylum Firmicutes. Our study provides baseline data of the usefulness of KF in a ketogenic diet.  相似文献   
974.

Purposes

Anastomosis is one of the basic skills of a gastrointestinal surgeon. Stapling devices are widely used because stapled anastomosis (SA) can shorten operation times. Antiperistaltic stapled side-to-side anastomosis (SSSA) using linear staplers is a popular SA technique that is often referred to as “functional end-to-end anastomosis (FEEA).” The term “FEEA” has spread without any definite validation of its “function.” The aim of this review is to show the heterogeneity of SA and conventional hand-sewn end-to-end anastomosis (HEEA) and to advocate the renaming of “FEEA.”

Methods

We conducted a narrative review of the literature on SSSA. We reviewed the literature on ileocolic and small intestinal anastomosis in colonic cancer, Crohn’s disease and ileostomy closure due to the simplicity of the technique.

Results

The superiority of SSSA in comparison to HEEA has been demonstrated in previous clinical studies concerning gastrointestinal anastomosis. Additionally, experimental studies have shown the differences between the two anastomotic techniques on peristalsis and the intestinal bacteria at the anastomotic site.

Conclusions

SSSA and HEEA affect the postoperative clinical outcome, electrophysiological peristalsis, and bacteriology in different manners; no current studies have shown the functional equality of SSSA and HEEA. However, the use of the terms “functional end-to-end anastomosis” and/or “FEEA” could cause confusion for surgeons and researchers and should therefore be avoided.
  相似文献   
975.
A patient with chronic eosinophilic leukemia and a unique complex chromosomal translocation 46,XY,t(3;9;5)(q25;q34;q33) who had elevated blood interleukin-5 is reported. Complete cytogenetic remission was induced by interferon-α after treatment failure with corticosteroids and cytotoxic drugs. Severe cardiopulmonary symptoms due to hypereosinophilia and thromboembolic complication improved dramatically in the first 6 months of interferon therapy. Since it is known that the gene encoding for interleukin-5 resides on the long arm of chromosome 5, it may be possible that the chromosomal translocation in our patient resulted in overproduction of this cytokine, and our findings may be helpful for understanding the pathogenesis of this disorder. Am. J. Hematol. 58:137–141, 1998. © 1998 Wiley-Liss, Inc.  相似文献   
976.
977.
Hereditary ceroid-lipofuscinosis in English setters has been proposed to be the canine equivalent of human juvenile ceroid-lipofuscinosis, which results from defects in the CLN3 gene. Analyses were performed to determine whether the disease in English setters is also the consequence of a CLN3 gene mutation. Canine CLN3 cDNA was found to contain a 1,314-bp open reading frame predicting a derived amino acid sequence which is 89%, 85%, and 84% identical to the predicted amino acid sequences for the human, mouse, and rabbit CLN3 proteins, respectively. The canine gene has sixteen exons. No differences were detected when cDNA nucleotide sequences from an English setter with ceroid-lipofuscinosis and from a normal dog were compared. Moreover, alleles of the canine CLN3 gene distinguished by an intragenic marker segregated independently from the disease in an English setter family, eliminating CLN3 as the locus for the canine disease. A ceroid-lipofuscinosis-affected Tibetan terrier was homozygous for a Gly70Glu CLN3 variant; however, this allele is common in dog breeds considered free of ceroid-lipofuscinosis. J. Neurosci. Res. 52:268–275, 1998. © 1998 Wiley-Liss, Inc.  相似文献   
978.
979.
980.
Although radiation enteritis is a well-recognized sequel of therapeutic irradiation, the standard surgical method is not universally agreed upon. Not only the short-term effect but also the long-term effect after a surgical intervention has been fairly well reported. To reassess the surgical therapy for radiation enteritis, we retrospectively analyzed 48 patients (5 males and 43 females, mean age 58.6 years) who had been operated on in our department. These patients were divided into two types according to the time of surgery or the clinical manifestation, and operative methods were analyzed. Patient’s status such as bowel movement, body weight, and serum albumin value after surgery were analyzed, together with the patients survival. Our surgical methods were small intestinal resection for the intestinal obstruction, and pull-through reconstruction for proctitis. Two patients died of multiple organ failure caused by perforated peritonitis irrespective of emergent operation. Although the overall morbidity was 21.7%, there was no leakage when bowels were anastomosed. Overall survival after radiation-related complication in patients without previous neoplastic disease recurrence was 89%, 79%, and 69%, at 1, 3, and 5 years after surgery, respectively. Bowel motility, serum albumin level, and body weight recovered gradually soon after the operation and reached satisfactory levels within 6 months. Our analysis showed that small bowel injury should be treated by generous resection of the affected bowel followed by careful anastomosis of the disease-free ends, while rectal resection is best dealt with by restorative proctectomy. This may provide a good quality of life and minimize major postoperative complications such as leakage.  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