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   9224篇
  免费   479篇
  国内免费   51篇
耳鼻咽喉   169篇
儿科学   200篇
妇产科学   80篇
基础医学   1205篇
口腔科学   250篇
临床医学   637篇
内科学   2661篇
皮肤病学   74篇
神经病学   658篇
特种医学   324篇
外科学   1413篇
综合类   29篇
预防医学   228篇
眼科学   269篇
药学   703篇
中国医学   18篇
肿瘤学   836篇
  2023年   66篇
  2022年   98篇
  2021年   223篇
  2020年   130篇
  2019年   152篇
  2018年   178篇
  2017年   129篇
  2016年   203篇
  2015年   164篇
  2014年   227篇
  2013年   275篇
  2012年   406篇
  2011年   457篇
  2010年   273篇
  2009年   207篇
  2008年   420篇
  2007年   419篇
  2006年   383篇
  2005年   441篇
  2004年   441篇
  2003年   414篇
  2002年   428篇
  2001年   324篇
  2000年   317篇
  1999年   272篇
  1998年   129篇
  1997年   89篇
  1996年   82篇
  1995年   70篇
  1994年   61篇
  1993年   52篇
  1992年   209篇
  1991年   168篇
  1990年   177篇
  1989年   168篇
  1988年   163篇
  1987年   152篇
  1986年   133篇
  1985年   112篇
  1984年   102篇
  1983年   73篇
  1982年   49篇
  1981年   43篇
  1979年   78篇
  1978年   55篇
  1976年   45篇
  1972年   47篇
  1971年   41篇
  1970年   43篇
  1968年   45篇
排序方式: 共有9754条查询结果,搜索用时 31 毫秒
1.

Purpose

Suppression of respiratory movement of the liver would be desirable for high-precision radiation therapy for liver tumors. We aimed to investigate the effect of our original device-free compressed shell fixation method and breathing instruction on suppression of respiratory movement. The characteristics of liver motion based on the movement of a fiducial marker were also analyzed.

Methods and Materials

First, respiratory amplitudes of the liver with the device-free compressed shell were analyzed from the data of 146 patients. The effect of this shell fixing method on liver movement was evaluated. Second, as another cohort study with 166 patients, interfractional internal motion of the liver for patients fixed in the shell was calculated using the fiducial marker coordinate data of images for position setting before daily irradiation. Third, in another 12 patients, intrafractional internal motion was calculated from the fiducial marker coordinate data using x-ray images before and after irradiation.

Results

The median respiratory movement without the shell, after fixing with the shell, and after instructing on the breathing method with the shell was 14.2 (interquartile range, 10.7-19.8), 11.5 (8.6-17.5), and 10.4 mm (7.3-15.8), respectively. Systematic and random errors of interfractional internal motion were all ≤2 mm in the left-right and anteroposterior directions and 3.7 and 3.0 mm, respectively, in the craniocaudal direction. Systematic and random errors of intrafractional internal motion were all ≤1.3 mm in the left-right and anteroposterior directions and 0.8 and 2.4 mm, respectively, in the craniocaudal direction.

Conclusions

The device-free compressed shell fixation method was effective in suppressing the respiratory movement of the liver. Irradiation position matching using the fiducial marker can correct the interfractional internal motion on each day, which would contribute to the reduction of the margin to be given around the target.  相似文献   
2.
3.

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   
4.
5.
6.
7.
8.
We examined the mechanisms of the inhibition of DNA synthesis by a new platinum compound, (-)-( R )-2-aminomethylpyrrolidine(1,1-cyclobutane-dicarboxylato)-2-platinum(II) monohydrate (DWA-2114R), a derivative of the antitumor drug cis- diamminedichloroplatinum(II) (CDDP), using prokaryotic and eukaryotic DNA polymerases. Preincubating activated DNA with CDDP or DWA-2114R reduced its template activity for prokaryotic and eukaryotic DNA polymerases in a dose-dependent manner. DWA2114R required six times greater drug concentration and two times longer incubation time to show the same decrease of the template activity compared to CDDP. Treatment of primed pUC118 ssDNA templates with the two drugs followed by second-strand synthesis by prokaryotic and eukaryotic DNA polymerases revealed that DWA2114R bound to DNA in a similar manner to CDDP and these adducts blocked DNA elongation by DNA polymerases of eukaryotes as well as of prokaryotes. With these two drugs, the elongations by E. coli DNA polymerase I (Klenow fragment), T7 DNA polymerase and calf thymus DNA polymerase α were strongly arrested at guanine-guanine sequences (GG). Stop bands were also observed at adenine-guanine sequences (AG) guanine-adenine-guanine sequences (GAG) and mono-guanine sequence (G). Calf testis DNA polymerase β was also arrested efficiently at AG, GAG and G, but much more weakly at GG. This pattern was common to DWA2114R and CDDP.  相似文献   
9.
Effects of N-(2,6-dimethylphenyl)-2-(2-oxo-1-pyrrolidinyl) acetamide (DM-9384) on learning and memory were studied using four different experimental rat models. In electroconvulsive shock- or scopolamine-induced amnesia in the step-through passive avoidance task, DM-9384 improved both types of amnesia when administered before the training trial. Aniracetam also showed similar but somewhat weaker effects. Furthermore, in the scopolamine amnesia model, an improvement was confirmed with arecoline. The dose-response curves for these compounds were bell-shaped. In the shuttle box active avoidance task, DM-9384 administered daily 1 hr before each training session facilitated the acquisition process of the avoidance response. In addition, the experiment of light-dark discrimination task with positive reinforcement showed that this compound administered daily after each session slightly accelerated the acquisition process of the correct response. These results suggest an ability of DM-9384 to enhance cognitive functions.  相似文献   
10.
In lung cancer patients, hypercalcemia is a fairly common metabolic problem associated with malignancy. However, the occurrence of hypercalcemia in lung cancer patients means an ominous prognostic sign. As hypercalcemia often causes early death, quick diagnosis and treatment for hypercalcemia are required. A 69-year-old woman was admitted to our hospital with anorexia caused by hypercalcemia. On admission, serum level of PTH was elevated and PTHrP was normal. From the results of CT findings and transbronchial lung biopsy, the cause of the hypercalcemia was determined as lung cancer incidentally complicated with primary hyperparathyroidism. First, serum calcium level was returned to normal through hydration with saline and bisphosphonates. Next, left hemithyroidectomy for primary hyperparathyroidism was performed. Histologically, the tumor was diagnosed as parathyroid adenoma. Fifteen days later, left lower lobectomy for primary lung cancer was performed under a video-assisted thoracoscopic approach. Histologically, the tumor was diagnosed as a moderately differentiated adenocarcinoma. Four years and three months after the operation, the patient is alive and well with no sign of recurrence. When a lung cancer patient is complicated with hypercalcemia, we need to consider that primary hyperparathyroidism is a possible cause of the hypercalcemia.  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