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   2800篇
  免费   153篇
  国内免费   12篇
耳鼻咽喉   20篇
儿科学   58篇
妇产科学   40篇
基础医学   389篇
口腔科学   91篇
临床医学   244篇
内科学   591篇
皮肤病学   72篇
神经病学   232篇
特种医学   138篇
外科学   425篇
综合类   19篇
一般理论   1篇
预防医学   120篇
眼科学   91篇
药学   246篇
中国医学   3篇
肿瘤学   185篇
  2023年   15篇
  2022年   24篇
  2021年   92篇
  2020年   57篇
  2019年   73篇
  2018年   68篇
  2017年   41篇
  2016年   74篇
  2015年   73篇
  2014年   92篇
  2013年   107篇
  2012年   152篇
  2011年   172篇
  2010年   73篇
  2009年   72篇
  2008年   135篇
  2007年   122篇
  2006年   118篇
  2005年   100篇
  2004年   77篇
  2003年   92篇
  2002年   69篇
  2001年   87篇
  2000年   65篇
  1999年   65篇
  1998年   19篇
  1997年   21篇
  1996年   22篇
  1995年   17篇
  1994年   39篇
  1993年   15篇
  1992年   43篇
  1991年   43篇
  1990年   55篇
  1989年   41篇
  1988年   57篇
  1987年   53篇
  1986年   58篇
  1985年   37篇
  1984年   24篇
  1983年   22篇
  1982年   23篇
  1979年   21篇
  1978年   16篇
  1977年   16篇
  1976年   18篇
  1975年   16篇
  1973年   19篇
  1972年   14篇
  1968年   10篇
排序方式: 共有2965条查询结果,搜索用时 671 毫秒
1.
2.
3.
It has been demonstrated that total parenteral nutrition (TPN) modulates the function of the hepatic reticuloendothelial system (RES). The objective of this study was to evaluate the impact of two different TPN lipid emulsions on the recovery of allograft RES function after orthotopic liver transplantation (OLTx). In a prospective, double-blind study, OLTx patients were randomly assigned to two treatment groups. Group I ( n=13) received a TPN regimen that included long-chain triglycerides (LCT). Group II ( n=9) received a TPN regimen that included a fat emulsion consisting of both medium-chain triglycerides (MCT) and LCT. At baseline, i.e., on days 2 or 3 after OLTx ( t1), before lipids for TPN were started, hepatic RES function was determined using the human serum albumin millimicrosphere technique (K-value, 1/min). A second measurement ( t2) was obtained after 7 days of TPN, including one of the study's two fat emulsions. The mean (+/- SD) K-value (1/min) was 0.48+/-0.16 in the LCT group and 0.55+/-0.28 in the MCT/LCT group at t1, and it improved to 0.62+/-0.21 in the LCT group and to 0.86+/-0.32 in the MCT/LCT group at t2. RES function recovery was significantly better in the MCT/LCT group ( P< or = 0.05). MCT/LCT emulsion appears to be the TPN fat emulsion of choice after OLTx as it seems to have less impact on hepatic RES recovery.  相似文献   
4.
5.
The isolated azygos continuation of the inferior vena cave is a very rare variation of this organ. It is accompanied by the absence of the retrohepatic segment of the vena cava with two new observations, the literature is revised and the origin discussed.  相似文献   
6.
Theodor Leber grew up in Heidelberg as the son of a professor of Romance languages. Initially he planned to study natural sciences. Bunsen's advice led him to medicine. During his studies he succeeded in solving a competition problem posed by Helmholtz in the medical department. A short period of practical work in the eye hospital of Knapp was unsatisfactory. In Vienna with the physiologist Carl Ludwig, he was able in 1863/64, at the age of only 24 years, to demonstrate the blood circulation of the eye by color injections into the arteries and veins. Since that time the schematic drawings of his results can be found in every textbook of ophthalmology. On the occasion of the congress of the German Ophthalmological Society in Heidelberg in 1864, Theodor Leber reported on these findings and met with immense approval. In 1864–67 he followed an invitation as coworker of Liebreich to Paris; in 1867 he became A.v. Graefe's coworker in Berlin; in 1871 he moved to Göttingen, which became the first eye clinic with a laboratory for experimental investigations.The second epoch-making discovery accomplished by Leber was the detection of the fluid exchange in the eye. These results have also been confirmed by modern methods. Therefore, Theodor Leber can be called the father of experimental ophthalmology.  相似文献   
7.
A study is reported of the utilization of non-clinical institutional care (geriatric and old people's homes) by the elderly inhabitants of Mannheim (pop. 306,000). The aim of the research was to establish the probability of admission to institutional care of an elderly person from this population, and to examine the influence of socio-demographic features. Under the West German health insurance system, most of the long-stay care of the elderly is provided not in hospitals but in nursing and geriatric homes. Data were collected on age at admission, place of residence before admission, duration of stay, age at death and place of death, as well as on the financial basis of care. The data were gathered retrospectively, the sample consisting of all inhabitants of Mannheim over 65 years old who died in the year 1982 (N = 2,585). At any given time only about four per cent of the elderly population will be in institutional care. In this respect, Mannheim is typical for the Federal Republic of Germany. However, the research findings demonstrate that approximately one elderly person in five will spend the last period of his life in this type of care. Seen in this light, the geriatric and old people's homes acquire a much greater social significance than is revealed by the number of institutional places alone.  相似文献   
8.
Menthol glucuronide was isolated from the urine of a healthy 70-kg female subject following ingestion of 400 mg of peppermint oil and 6 g of 99% [U-(13)C]glucose. Glucuronide (13)C-excess enrichment levels were 4-6% and thus provided high signal-to-noise ratios (SNRs) for confident assignment of (13)C-(13)C spin-coupled multiplet components within each (13)C resonance by (13)C NMR. The [U-(13)C]glucuronide isotopomer derived via direct pathway conversion of [U-(13)C]glucose to [U-(13)C]UDP-glucose was resolved from [1,2,3-(13)C(3)]- and [1,2-(13)C(2)]glucuronide isotopomers derived via Cori cycle or indirect pathway metabolism of [U-(13)C]glucose. In a second study, a group of four overnight-fasted patients (63 +/- 10 kg) with severe heart failure were given peppermint oil and infused with [U-(13)C]glucose for 4 hr (14 mg/kg prime, 0.12 mg/kg/min constant infusion) resulting in a steady-state plasma [U-(13)C]glucose enrichment of 4.6% +/- 0.6%. Menthol glucuronide was harvested and glucuronide (13)C-isotopomers were analyzed by (13)C NMR. [U-(13)C]glucuronide enrichment was 0.6% +/- 0.1%, and the sum of [1,2,3-(13)C(3)] and [1,2-(13)C(2)]glucuronide enrichments was 0.9% +/- 0.2%. From these data, flux of plasma glucose to hepatic UDPG was estimated to be 15% +/- 4% that of endogenous glucose production (EGP), and the Cori cycle accounted for at least 32% +/- 10% of GP.  相似文献   
9.
The usefulness of indices commonly used in Doppler sonography is limited; the aim of this study was to investigate if inclusion of systolic acceleration and deceleration patterns in Doppler indices will result in practical diagnostic advantages. Systolic delay time index (SDTI) and height-width index (HWI) are compared to Gosling's pulsatility index (PI) and to PI-based damping factors (DF) in patients with isolated lesions in the distal superficial femoral artery before and after percutaneous transluminal angioplasty (PTA). Before PTA, all indices distal to the lesion differ significantly from proximal indices. After successful PTA, none of the indices is able to detect the PTA outcome with sufficient sensitivity. The additionally defined curve broadening index (CBI) shows a 100% sensitivity for detecting PTA success in the examined patient population.  相似文献   
10.
INTRODUCTION: In patients (pts) with atrial fibrillation (AF) of more than 48 hours' duration, electrical cardioversion (ECV) should only be performed after 3 weeks of effective anticoagulation. Transesophageal echocardiography (TEE) allows earlier ECV; however, despite exclusion of thrombi in the atrium and left atrial appendage (LAA), cases of thromboembolism related to ECV have been documented in AF. To define a low-risk group for cardioversion without previous anticoagulation, pts were selected for immediate ECV if no thrombi or dynamic spontaneous echo contrast (auto-contrast) were found after TEE and if LAA velocity was more than 0.25 m/sec. METHODS AND RESULTS: We performed TEE in 31 consecutive pts referred for ECV for AF of more than 48 hours' duration and without previous anticoagulation. After TEE the pts eligible for immediate ECV began anticoagulation with low molecular weight heparin (enoxaparin), subcutaneously in therapeutic doses, together with warfarin immediately before cardioversion. Enoxaparin was continued until an INR of over 2 was reached. Based on the TEE findings, the pts were divided in 2 groups: immediate ECV, group A, 20 pts with a mean age of 62 +/- 13 years, 6 female; and conventional therapy with warfarin before ECV, group B, 11 pts, mean age of 67 +/- 10 years (p < 0.05), 2 female. None of the pts in either group had mitral stenosis or previous episodes of thromboembolism. The mean transverse diameter of the left atrium in the 31 pts was 47 +/- 4.5 mm, without statistically significant differences between the 2 groups. Of the 11 pts in group B, 3 had a thrombus in the LAA, 6 dynamic spontaneous echo contrast and the remainder LAA velocities of less than 0.25 m/sec. ECV was achieved in all the pts, with no complications. Oral anticoagulation was maintained for at least a month. At one month, sinus rhythm was maintained in 75% of group A and 45% of group B (p < 0.01). CONCLUSION: In pts with AF of more than 48 hours' duration and no previous history of thromboembolism, the use of our exclusion criteria during TEE enabled stratification of a low-risk population for immediate ECV, which was accomplished effectively and safely in 2/3 of the pts. This strategy is associated with early symptomatic improvement, and may contribute to maintenance of sinus rhythm after one month, which was significantly better than in the pts who had prolonged therapy with warfarin before ECV, despite the differences found in age and left ventricular function.  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