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   187725篇
  免费   2038篇
  国内免费   25篇
耳鼻咽喉   1306篇
儿科学   7155篇
妇产科学   3367篇
基础医学   18034篇
口腔科学   1641篇
临床医学   13800篇
内科学   32933篇
皮肤病学   910篇
神经病学   17841篇
特种医学   9165篇
外科学   30095篇
综合类   2394篇
一般理论   20篇
预防医学   20068篇
眼科学   3045篇
药学   10224篇
  1篇
中国医学   646篇
肿瘤学   17143篇
  2024年   50篇
  2023年   316篇
  2022年   484篇
  2021年   937篇
  2020年   540篇
  2019年   803篇
  2018年   22651篇
  2017年   17837篇
  2016年   19988篇
  2015年   1456篇
  2014年   1482篇
  2013年   1595篇
  2012年   8131篇
  2011年   22095篇
  2010年   19294篇
  2009年   11937篇
  2008年   20158篇
  2007年   22302篇
  2006年   1013篇
  2005年   2583篇
  2004年   3704篇
  2003年   4608篇
  2002年   2694篇
  2001年   304篇
  2000年   439篇
  1999年   186篇
  1998年   233篇
  1997年   227篇
  1996年   106篇
  1995年   120篇
  1994年   126篇
  1993年   81篇
  1992年   57篇
  1991年   102篇
  1990年   145篇
  1989年   86篇
  1988年   64篇
  1987年   50篇
  1986年   32篇
  1985年   49篇
  1984年   36篇
  1983年   34篇
  1982年   45篇
  1980年   50篇
  1974年   24篇
  1938年   61篇
  1937年   26篇
  1934年   30篇
  1932年   58篇
  1930年   49篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
991.
Purpose: Acute appendicitis is one of the most common surgical diseases. Simple and precise guidelines for treating acute appendicitis are necessary for improving the treatment outcome of this disease. The purpose of this study was to determine the impact of a clinical pathway and standardization of treatment for acute appendicitis at our hospital. Methods: The clinical pathway and standardization of treatment for acute appendicitis were introduced to our hospital in January 2000. We compared the length of hospitalization, postoperative stay, hospital costs, and operation time during the years before and the years after their introduction. Results: There was no significant difference in the clinical characteristics of the 73 patients in the control group and the 112 patients in the pathway group. There were 6 (8.2%) and 24 (21.4%) cases of perforated appendicitis in the respective groups. The mean length of hospitalization (P < 0.001), postoperative stay (P < 0.001), and hospital costs (P < 0.01) were significantly less in the patients in the pathway group who underwent surgery. Conclusion: Our clinical pathway and standardization of treatment for acute appendicitis proved effective for treating patients with acute appendicitis and minimizing costs without compromising patient care. Received: February 19, 2002 / Accepted: November 19, 2002 Reprint requests to: K. Takegami (address 2)  相似文献   
992.
Synovial fluid (SF) is a dynamic reservoir for proteins originating from serum, synovial tissue, and cartilage. The composition of the SF proteome may reflect the pathophysiological conditions affecting the circulatory system and cartilage. Our long-term goal is to identify reliable protein markers for osteoarthritis (OA) in SF. We first evaluated the pattern of SF proteins on two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) as a function of protein loading, pH range for isoelectric focusing, and concentration of acrylamide in SDS-PAGE. Removal of albumin and -globulins from the samples did not improve the detection of protein spots on 2D-PAGE. The repeatability of protein spot intensity was tested by triplicate 2D-PAGE of a given sample; these experiments showed low intrasample variability (correlation coefficients 0.89–0.95). Differences between multiple samples were tested by comparing the 2D-PAGE of four samples. These experiments showed slightly greater variation between samples (correlation coefficients 0.85–0.93) and a number of differentially expressed proteins. The intensity of 18 protein spots differed more than fivefold, and the intensity of nine protein spots differed more than 100-fold. These results show that 2D-PAGE can be used under standard conditions to screen SF samples and identify a small subset of proteins in SF that are potential markers associated with OA.  相似文献   
993.
The incidence of gastric cancer and the need for subsequent surgery has been decreasing in the United States. However, very few population-based studies on the magnitude of these changes are available. The objective of the present study was to characterize temporal trends in the use of gastric resection in the treatment of gastric cancer. Patients with a primary diagnosis code for gastric cancer (N = 105,887) and a procedure code for gastric resection (N = 23,690) in the Nationwide Inpatient Sample for 1988–2000 were included. The Nationwide Inpatient Sample represents a 20% stratified random sample representative of all United States hospitals. Outcome variables included the overall incidence, in-hospital mortality rate, and length of stay. Rates of surgery are shown as the number of cases per 100,000 hospital discharges. Hospital volume was defined as follows: low volume (1 to 4 cases per year), medium volume (5 to 8 cases per year), and high volume (9 or more cases per year). Rates of gastric resection have shown a 20% decline from 30 cases per 100,000 (1988-1989) to 24 cases per 100,000 (1999-2000) (P = 0.001). In-hospital mortality has not changed over the 13-year period and remains at 7.4%. There was significant variation in mortality across hospitals, with very low-volume centers having an 8.9% mortality rate, whereas very high-volume centers had a 6.4% mortality rate (P < 0.001). The market share of gastric resections performed at high-volume centers increased a small amount from 43% (1988–1989) to 48% (1999-2000) (P = 0.023). Over the 13-year period, length of stay decreased from 15 days (interquartile range [IQR] 11–23) in 1988 to 11 days (interquartile range [IQR] 8–16) in 2000 (P < 0.001). Rates of gastric resection for cancer have shown a modest decline over the past 13 years in the United States. Although the length of stay for these patients has decreased, no significant changes to in-hospital mortality have occurred. Given the declining rates of gastric cancer surgery, and the superior outcomes at high-volume centers, regionalization of care may improve mortality rates for this high-risk surgical procedure. Presented at the Forty-Fourth Annual Meeting of The Society for Surgery of the Alimentary Tract, Orlando, Florida, May 18-22, 2003 (poster presentation).  相似文献   
994.
Linkage guide for rotational alignment during total knee arthroplasty   总被引:1,自引:0,他引:1  
A linkage guide was devised for use in conjunction with knee arthroplasty instruments to achieve proper component rotation. The femoral component was rotationally aligned to the surgical epicondylar axis using one guide. The other guides were used after all bone surfaces were cut and soft tissue balancing was completed. A Kirschner wire was guided into the proximal tibial aspect parallel to the sagittal plane of the femoral component with the patella in its normal position and the knee in full extension. The wire was used as a reference to determine tibial component rotation. The relative rotational alignment of 21 knees in 19 patients who had undergone cruciate-retaining total knee arthroplasty utilizing this guide was assessed using the modified Eckhoff method. The results of radiographic analysis were compared with those in a control group of 25 knees where the guide was not employed. The external rotation of the femoral component relative to the tibial component was 1.3° ± 2.0° (mean ± SD) in the guided group and 1.1° ± 4.4° in the control group. The relative rotational angle was significantly more consistent using the guide. Implant malrotation can be reduced using our technique.  相似文献   
995.
The C3-C4 propriospinal neurons (PNs) transmit motor signals to forelimb motoneurons. Stem axons of the PNs bifurcate in the same segments and send ascending axons to the lateral reticular nucleus (LRN) as well as descending axons to the cervical motor nucleus. After laminectomy of decerebrated cats, ascending axons were stimulated by tungsten electrodes placed in the LRN. The N1 descending incoming volleys via axon reflexes with a latency of approximately 1.5 ms (N1 potential) were recorded in the forelimb motoneuron pools at C8 segment. We compressed the spinal cord at C3 or C6 segment by 6 x 5 mm plastic material and analyzed amplitudes of the N1 potentials at C8 motoneuron pools. After spinal compression step by step until 3000 microm from the surface for 30 min at the C3 segment, the amplitude of N1 potentials decreased to approximately 39.7% of the control. On the other hand, the amplitude of N1 potentials changed little after the same compression of the C6 segment. The N1 potentials during compression of the C3 segment did not recover to the initial amplitude of 63.5% after decompression. It is concluded that activities of axons at C3 segment are more sensitive than those at C6 to compression of the spinal cord. We discuss the properties of the bifurcation of the stem axons and the central spinal cord injury.  相似文献   
996.
Changes in bone turnover markers during 14-day 6° head-down bed rest   总被引:1,自引:0,他引:1  
Osteoporosis caused by exposure to microgravity represents a serious clinical concern, but the mechanisms have yet to be fully elucidated. The present research aimed to elucidate the effects of microgravity environments on bone turnover, with a specific focus on changes in bone resorption markers such as type I collagen cross-linked N-telopeptides (NTx) and deoxypyridinoline (Dpyr), for which scant data are available regarding detailed time course. Methods using 6° head-down bed rest were utilized to simulate a microgravity environment. Eleven adult male volunteers underwent 6° head-down bed rest for 14 days; measurements were made of serum and urine Ca concentrations, in addition to osteocalcin (OC), bone alkaline phosphatase (ALP), NTx, and Dpyr as bone turnover markers. By the end of bed rest, concentrations of bone ALP had significantly increased, but OC displayed a tendency toward decrease. Concentrations of Dpyr significantly increased from day 6, remaining elevated until the end of bed rest. Concentrations of NTx significantly increased on day 13 and at the end of bed rest. Serum and urinary concentrations of Ca increased significantly at the end of bed rest. Bone ALP represents a relatively early marker of osteoblast differentiation at the matrix maturation phase and OC is a late marker in osteoblast differentiation at the calcification phase. The present results therefore suggest an absolute increase in bone resorption and normal or reduced bone formation, together causing prominent uncoupling and rapid bone loss after simulated microgravity. Moreover, the present results suggest that bone resorption is enhanced at an early stage of exposure to microgravity environments.  相似文献   
997.
Background Conscious sedation using monitored anesthesia care can provide a clinical spectrum from relaxation to moderate anesthesia. This middle ground between general anesthesia and pure tumescent liposuction can help facilitate patient comfort and surgical proficiency during the procedure.Objective To describe a method of liposuction surgery with monitored anesthesia care in which a designated licensed and qualified individual is responsible for administration of supplemental intravenous conscious sedation as well as continuous monitoring of the patient.Methods Conscious sedation is induced with midazolam, and the patient is titrated to level II-V on the Ramsey sedation scale with propofol. The basic surgical technique is that of tumescent liposuction. However, the supplemental conscious sedation allows the tumescent fluid to be infiltrated at higher rates and fat extraction to be completed in a shorter period with minimal or no discomfort.Results In the authors experience with more than 5,000 cases of liposuction surgery using this method, safety and efficacy have been proved. No patients have experienced significant adverse effects.Conclusion Tumescent liposuction surgery with monitored anesthesia care provides a middle ground between general anesthesia and purely tumescent liposuction.  相似文献   
998.
Ruptured abdominal aortic aneurysms (RAAA) have a 78-94% mortality rate. If cost-effectiveness of screening programs for abdominal aortic aneurysms (AAA) are to be assessed, direct costs for RAAA repairs and elective AAA (EAAA) repairs are required. This study reports mortality, morbidity, and direct costs for RAAA and EAAA repairs in Nova Scotia in 1997-1998 and also compares Nova Scotia and U.S. costs. We performed a retrospective study of 41 consecutive RAAA and 48 randomly selected EAAA patients. Average total costs for RAAA repair were significantly greater than those for EAAA repair (direct costs: $15,854 vs. $9673; direct plus overhead costs: $18,899 vs. $12,324 [pricing in 1998 Canadian dollars]). Intensive care unit length of stay and blood product usage were the most substantial direct cost differentials ($3593 and $2106). Direct cost for preoperative testing and surveillance was greater in the EAAA group ($839 vs. $33). Estimates of U.S. in-hospital RAAA and EAAA repair costs are more than 1.5 times Nova Scotia costs. Direct in-hospital RAAA repair costs are $6181 more than EAAA repair costs. These in-hospital cost data are key cost elements required to assess the cost-effectiveness of various screening strategies for earlier detection and monitoring of AAA within high-risk populations in Canada. Further studies are required to estimate cost per quality-adjusted-life-year gained for various AAA screening and monitoring strategies in Canada.  相似文献   
999.
Carcinoid Tumors of the Common Bile Duct: Report of Two Cases   总被引:1,自引:0,他引:1  
We report two cases of carcinoid tumors of the common bile duct. The first patient was a 65-year-old woman in whom a carcinoid tumor of the distal bile duct was incidentally found during an open cholecystectomy for cholecystitis. The second patient was a 27-year-old man in whom a distal common bile duct carcinoid was incidentally found during orthotopic liver transplantation for sclerosing cholangitis and multiple biliary strictures. There are few reports of carcinoid tumors of the extrahepatic ducts, and a brief review of the relevant literature is discussed following these case reports. Received: April 22, 2002 / Accepted: November 19, 2002 RID="*" ID="*" Reprint requests to: D. K. Imagawa  相似文献   
1000.
 Changes in the fiber-type ratio and diameter during limb lengthening in 10 adult rabbits were studied using histochemical techniques. Changes in the ratio and diameter of muscle fibers (classified as type 1, 2A, or 2B fibers) in tibialis anterior muscles were examined after 20% gradual distraction of the tibia. There was an increase in the number of type 1 fibers and a decrease in type 2B fibers after tibial lengthening. Moreover, the average diameter of the type 1 fibers increased, whereas that of the type 2B fibers decreased. The diameters of muscle fibers measured immediately after completion of the lengthening showed a tendency to recover to normal levels within 1 month; however, the ratio profile of the muscle fibers changed both immediately and 1 month after lengthening. The above results demonstrate that stretched skeletal muscle adapts differently to bone lengthening according to the type of muscle fibers present, resulting in qualitative changes in the fiber-type profile. Received: February 1, 2002 / accepted: August 26, 2002 Acknowledgments. This work was supported in part by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science, and Culture of Japan. Offprint requests to: H. Yamazaki, 4-21-2 Kurakuen, Nishi-nomiya 662-0088, Japan  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