全文获取类型
收费全文 | 311047篇 |
免费 | 33632篇 |
国内免费 | 1573篇 |
专业分类
耳鼻咽喉 | 5419篇 |
儿科学 | 10776篇 |
妇产科学 | 8781篇 |
基础医学 | 30266篇 |
口腔科学 | 11498篇 |
临床医学 | 42638篇 |
内科学 | 63294篇 |
皮肤病学 | 8235篇 |
神经病学 | 25555篇 |
特种医学 | 14776篇 |
外国民族医学 | 97篇 |
外科学 | 49268篇 |
综合类 | 1309篇 |
现状与发展 | 40篇 |
一般理论 | 11篇 |
预防医学 | 31145篇 |
眼科学 | 6844篇 |
药学 | 15975篇 |
2篇 | |
中国医学 | 234篇 |
肿瘤学 | 20089篇 |
出版年
2023年 | 5231篇 |
2021年 | 3420篇 |
2020年 | 5770篇 |
2019年 | 2562篇 |
2018年 | 10963篇 |
2017年 | 11630篇 |
2016年 | 11508篇 |
2015年 | 13183篇 |
2014年 | 15156篇 |
2013年 | 16285篇 |
2012年 | 14701篇 |
2011年 | 9473篇 |
2010年 | 9602篇 |
2009年 | 13405篇 |
2008年 | 6581篇 |
2007年 | 6325篇 |
2006年 | 7717篇 |
2005年 | 14376篇 |
2004年 | 15141篇 |
2003年 | 10476篇 |
2002年 | 5589篇 |
2001年 | 6566篇 |
2000年 | 3317篇 |
1999年 | 7840篇 |
1998年 | 2711篇 |
1997年 | 2266篇 |
1996年 | 2416篇 |
1995年 | 2162篇 |
1992年 | 7733篇 |
1991年 | 7828篇 |
1990年 | 7935篇 |
1989年 | 7546篇 |
1988年 | 7045篇 |
1987年 | 6684篇 |
1986年 | 6375篇 |
1985年 | 5616篇 |
1984年 | 3887篇 |
1983年 | 3254篇 |
1979年 | 3948篇 |
1978年 | 2515篇 |
1977年 | 1950篇 |
1975年 | 2568篇 |
1974年 | 3217篇 |
1973年 | 2827篇 |
1972年 | 2860篇 |
1971年 | 2805篇 |
1970年 | 2636篇 |
1969年 | 2511篇 |
1968年 | 2257篇 |
1967年 | 2193篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Three-dimensional images of bone structures can easily be reconstructed from computed tomography data. The technique and the advantages of contemplating reconstructions of bone defects in different directions are described. A special software programme allows to combine all data which are given by the standard CT. The slice diameter is two millimetres. The reconstruction shows bone surfaces in all required views. In traumatic and orthopaedic surgery 3-D-CT is useful in the analysis, detection and preoperative planning of comminuted bone injuries of the spine, pelvis, knee, shoulder and the calcaneus. With this technique it is possible to see the bone in its topographic constellation, to observe fractures in unusual directions and to identify fragments from each other. The surgeon gets a lot of additional information which is helpful to decide on the incision, the reduction and the fixation of fragments. Undesirable effects during operation are reduced, which leads to a more accurate treatment and subsequent better results. 相似文献
992.
F Ledesma Casta?o S Echevarria Vierna J L Lozano Polo R Oloriz Rivas C Alvarez Moreno F Pons Romero 《European journal of clinical nutrition》1992,46(7):527-533
Interleukin-1 (IL-1) is a cytokine produced by the macrophage-monocyte system that has important effects on immunological responses and inflammatory reactions. Several clinical studies have shown that severe protein energy malnutrition adversely effects cell-mediated immune responses and the functional state of macrophages. The objective of this study was to analyse IL-1 production by adherent cells stimulated in vitro with lipopolysaccharide B (LPS) from patients with alcoholic cirrhosis of the liver and its possible relationship with nutritional states. Forty-five patients with alcoholic cirrhosis and 28 healthy donors were investigated. A combined index of nine anthropometric and biochemical parameters was used to evaluate nutritional status of cirrhotic patients, allowing a distinction to be made between those patients with acceptable nutrition (group I: 40%), those with slight malnutrition (group II: 37.7%), and those with severe malnutrition (group III: 22.3%). IL-1 activity was significantly lower in the cirrhosis patients than in the controls (P less than 0.001). This activity also was significantly lower in samples obtained from cirrhotics with severe malnutrition than in those with acceptable nutrition (P less than 0.05); the combined index and the sole anthropometric index gave the same results, suggesting that malnutrition may play a role in the immunoregulatory disturbances in the pathogenesis of alcoholic liver disease. 相似文献
993.
Cryotherapy was applied to 182 rectal cancer patients in the Department of General Surgery, University of Ulm, between 4/1982 and 4/1991. Recipients of this tumor freezing therapy were patients whose general condition was bad, patients with an advanced inoperable carcinoma, patients with tumor recurrence and patients refusing operation. Rectal carcinomas, mostly in an advanced stage, were usually freezed several times. Only 4 patients with general inoperability reached the survival time margin of 5 years. In 18 patients local tumor destruction was possible by application of cryotherapy. In 80% of cases disagreeable tumor symptoms like tenesma, mucous discharge and oozing hemorrhages could be reduced or completely removed. Perianal pain and intense tumor bleeding could be relieved temporarily or definitely in only 50% of patients. An artificial anus could be avoided in 80% of cases by local tumor destruction/reduction or arrest of tumor growth. The mean survival time of patients with tumor recidivation was 11 months after onset of the recurrence. Tumor progression, incontinence and iatrogenic rectal perforation made an artificial anus necessary in 14 patients. 相似文献
994.
Computer-Assisted Instruction Improves Clinical Reasoning Skills of Dietetics Students 总被引:1,自引:0,他引:1
MARTHA A. RAIDL PhD RD OLIVIA BENNETT WOOD MPH RD JAMES D. LEHMAN PhD WILLIAM D. EVERS PhD RD 《Journal of the American Dietetic Association》1995,95(8)
Objective The effects of a computer-assisted instruction (CAI) tutorial program on learning clinical reasoning skills were compared in undergraduate dietetics students.Design A drill-and-practice program to control for time on task, a tutorial program, and a simulation program, as the test vehicle, were developed. The tutorial and simulation programs presented data on a patient with cardiovascular disease.Setting Subjects were tested in 30 undergraduate dietetics programs.Subjects Participants were 413 undergraduate diet therapy students enrolled in a coordinated program in dietetics (CPD) or a didactic program in dietetics (DPD).Intervention After completion of lectures on cardiovascular disease, subjects were given the drill-and-practice program plus a simulation test (group 1), the tutorial plus a simulation test (group 2), or the simulation test only (group 3).Main outcome measures Scores on the simulation test were compared. Variables included type of CAI, dietetics program, year in school, computer experience, and experience using a medical chart. Mastery of objectives related to lower- and higher-level clinical reasoning skills introduced in the tutorial program was compared.Statistical analysis One-way analysis of variance and Student-Newman Keuls tests were conducted to determine any differences among the three groups. Reliability was determined using the Kuder-Richardson Formula 20.Results The reliability coefficient of the simulation test was 0.93. Group 2 scored higher on the simulation test than group 1 or group 3. As a group, the CPD students scored higher than the DPD students. When CPD and DPD students were divided into the three experimental groups, there was no significant difference between the CPD and DPD student simulation scores. Group 2 mastered all objectives for lower-level reasoning skills and the higher-level decision-making objective better than groups 1 and 3.Applications/conclusions A computer tutorial program enhanced clinical reasoning skills in undergraduate dietetics students. This type of program could be used to supplement many topics taught in diet therapy and provide DPD students with experiential learning before their clinical intern practicums. J Am Diet Assoc. 1995; 95:868–873. 相似文献
995.
996.
Induction of mediator release from human glomerular mesangial cells by the terminal complement components C5b-9. 总被引:6,自引:0,他引:6
M Sch?nermark R Deppisch G Riedasch K Rother G M H?nsch 《International archives of allergy and applied immunology》1991,96(4):331-337
Exposure of cultured human glomerular mesangial cells (GMC) to normal human serum and an activator of the complement system results in rapid uptake of the terminal complement proteins C5b-9 by the cells. This 'innocent bystander' complement attack, however, does not result in cell killing, but in the stimulation of the GMC to release prostaglandin E (PGE), interleukin 1 (Il-1) and tumor necrosis factor (TNF). Endogenously synthesized Il-1 in turn activates PGE release, indicating that the C5b-9 attack initiates an autocrine feedback stimulation. Together with the fact that C5b-9 is found in many forms of glomerulonephritis, the data point to a role of the terminal complement proteins in the initiation and perpetuation of an inflammatory response. 相似文献
997.
998.
W Fehske J K?hler D Kessel R Rabahieh A Hagendorff K Stevens A Niedeggen B Lüderitz 《Zeitschrift für Kardiologie》1992,81(11):627-635
The normal leakage flow in modern technical heart valve prostheses can be visualized by color-coded Doppler-echocardiography, provided that an adequate ultrasonic image quality can be achieved. Sometimes it may be difficult, however, to distinguish such a normal leakage flow from pathological regurgitation. We therefore mounted new specimens of five different types of prostheses (Bj?rk-Shiley monostrut, Medtronic-Hall, Omnicarbon, Saint Jude Medical, Duromedics) into an invitro model, where the leakage flows could directly be visualized as emerging water jets. When the system was completely filled, the jets could also be registered by two-dimensional Doppler-echocardiography. For each valve, characteristic patterns for the localization of the principal jets were found. Besides the relative broad central jet in the Medtronic-Hall valve, all other jets arose mainly at the ring. They were detected at the hinges or the basis of the larger struts, respectively, and with asymmetrical mono-disc valves at the side of the smaller opening. The length and the orientation of the jets were found to change significantly with minimal variations of the position of the closing discs. This variability could be confirmed, when in a separate model the overall leakage flows were repeatedly measured. For patient examinations it seems useful to refer mainly to the localization of the jet origins. The comparison with reference values of jet-dimensions in Doppler images will rarely enable the examiner to distinguish between normal and pathological jets. 相似文献
999.
The purpose of the present study was to determine whether a hypotonic additive containing a low concentration of glycerol as a membrane permeable solute would improve the liquid storage of red blood cells (RBCs). Packed RBCs were stored either with 200 ml of an experimental additive solution, EAS 25, containing (m M ): glycerol 150, adenine 2, glucose 110, mannitol 55, and NaCl 50, or with 100 ml/unit of a conventional additive solution Adsol®. The results show that the adenosine triphosphate values, hemolysis, potassium leakage, and the morphology scores of RBCs were significantly better with EAS 25 than with Adsol up to 84 days of storage. The ATP values were significantly different only after the first 42 days of storage. The mean corpuscular volumes (MCVs) of the RBCs were significantly higher throughout in the experimental additive accompanied by decreased microvesiculation as compared to Adsol. The total microvesicle membrane protein shed by 100 ml of RBCs was 47.92±12.31 mg in Adsol and 18.96±5.49 mg in EAS 25 (p<0.001). The larger MCVs of the RBCs in EAS 25 may have a favorable effect on maintaining membrane integrity by decreasing the loss of membrane by microvesiculation. 相似文献
1000.
The right gastroepiploic artery (GEA) was used as a pedicled conduit for direct coronary artery revascularization in 20 patients presenting with more or less exhausted saphenous vein resources. The early angiographic patency of the GEA conduit appears to be satisfactory when it is connected to the right coronary artery system. A distinct disadvantage of GEA grafting is the necessity to enter the abdominal cavity, which may lead to probably rare and as yet unrecognized morbidity. Future abdominal surgery may injure the GEA conduit unless its topographic relations to the prepyloric antrum, liver and diaphragm are properly recognized. The surgeon must then be prepared to encounter antegastric, retrogastric, antehepatic, transhepatic and retrohepatic routes of the redirected intraabdominal artery. The present paper addresses this problem. Preoperative angiography of the celiac trunk and superior mesenteric artery may be helpful in decision-making when a patient reports or records show that a graft has been harvested from the abdominal cavity. 相似文献