全文获取类型
收费全文 | 137092篇 |
免费 | 44646篇 |
国内免费 | 181篇 |
专业分类
耳鼻咽喉 | 1993篇 |
儿科学 | 6271篇 |
妇产科学 | 2213篇 |
基础医学 | 24037篇 |
口腔科学 | 6617篇 |
临床医学 | 20251篇 |
内科学 | 34562篇 |
皮肤病学 | 8525篇 |
神经病学 | 19100篇 |
特种医学 | 3629篇 |
外科学 | 19124篇 |
综合类 | 528篇 |
一般理论 | 94篇 |
预防医学 | 11333篇 |
眼科学 | 2129篇 |
药学 | 9286篇 |
2篇 | |
中国医学 | 1146篇 |
肿瘤学 | 11079篇 |
出版年
2024年 | 81篇 |
2023年 | 622篇 |
2022年 | 843篇 |
2021年 | 2913篇 |
2020年 | 6055篇 |
2019年 | 12262篇 |
2018年 | 11850篇 |
2017年 | 12673篇 |
2016年 | 13465篇 |
2015年 | 13571篇 |
2014年 | 13930篇 |
2013年 | 15481篇 |
2012年 | 8997篇 |
2011年 | 9093篇 |
2010年 | 11374篇 |
2009年 | 7443篇 |
2008年 | 6032篇 |
2007年 | 4986篇 |
2006年 | 4933篇 |
2005年 | 4454篇 |
2004年 | 4370篇 |
2003年 | 4030篇 |
2002年 | 3780篇 |
2001年 | 1234篇 |
2000年 | 1039篇 |
1999年 | 663篇 |
1998年 | 633篇 |
1997年 | 482篇 |
1996年 | 453篇 |
1995年 | 406篇 |
1994年 | 326篇 |
1993年 | 314篇 |
1992年 | 264篇 |
1991年 | 225篇 |
1990年 | 213篇 |
1989年 | 161篇 |
1988年 | 165篇 |
1987年 | 138篇 |
1986年 | 150篇 |
1985年 | 145篇 |
1984年 | 162篇 |
1983年 | 137篇 |
1982年 | 170篇 |
1981年 | 171篇 |
1980年 | 134篇 |
1979年 | 91篇 |
1978年 | 87篇 |
1977年 | 68篇 |
1976年 | 62篇 |
1974年 | 54篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
41.
Jing‐Ping Zhang Limin Zheng Jiang‐Hai Wang Karl‐Eric Magnusson Xin Liu 《Phytotherapy research : PTR》2009,23(6):844-850
Ganoderma sinensis has been used widely in Oriental countries for the prevention and treatment of various diseases including cancer. Previous studies have shown that the lipid extract from Ganoderma exhibits direct cytotoxicity against tumor cells. Here, it is reported that the lipid extract from germinating G. sinensis spores, at lower concentrations that have no direct tumoricidal activity, induce potent antitumor immune responses in human monocytes/macrophages. Upon stimulation with the lipid extract, monocytes/macrophages exhibited markedly increased production of proinflammatory cytokines and surface expression of costimulatory molecules. Conditioned medium from stimulated cells effectively suppressed the growth of tumor cells. Apparently, the lipid extract triggered macrophage activation via a mechanism different from that associated with LPS. Moreover, it was observed that the lipid extract could partially re‐establish the antitumor activity of the immunosuppressive tumor‐associated macrophages. These results indicated that in addition to its direct tumoricidal activity, the lipid extract from G. sinensis spores could exert antitumor activity by stimulating the activation of human monocytes/macrophages. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
42.
43.
44.
Henry Ho‐Lung Chan 《Clinical & experimental optometry》2005,88(6):410-414
The first‐order kernel analysis in multifocal electroretinogram (mfERG) using low contrast stimulation is suggested as a way to detect the inner retinal responses in animal studies. In this case report, this protocol is applied to human patients with glaucoma to demonstrate the possibility of using mfERG as a tool to detect glaucomatous damage. Two patients with glaucoma were recruited and had mfERG measurements with the 103‐scaled hexagonal stimulus pattern at low (50 per cent) contrast. Their responses were analysed and compared with those from normal subjects with the mfERG measured under the same condition. In the normal subjects, there were obvious oscillatory components on the ascending and descending limbs of the first‐order kernel response to 50 per cent contrast. In the glaucomatous patients, the oscillatory component on the descending limb was obviously diminished. In addition, this component was significantly diminished in the quadrant with a glaucomatous visual field defect. This suggests that the low‐contrast stimulation condition in mERG measurement may provide a good way to detect glaucomatous damage and this may help in clinical diagnosis of glaucoma. 相似文献
45.
Skoug John W. Borin Marie T. Fleishaker Joseph C. Cooper Anne M. 《Pharmaceutical research》1991,8(12):1482-1488
The mechanism of release from sustained-release adinazolam mesylate tablets was assessed by the Higuchi equation and by analysis of drug release profiles through 60% released using the Peppas equation. Computed values of the diffusional exponent, n, ranged from 0.59 to 0.66. Values of n in this range are consistent with a mixed mechanism of release, with diffusion of drug through the hydrated polymer matrix and relaxation of this matrix being the principal processes controlling release. The rate of in vitro drug release was increased for half tablets relative to whole tablets and is attributed to an increase in the surface to volume ratio of half tablets of about 16%. This increase in surface-to-volume ratio of half tablets was reflected by an increase in the constant, k, from the Peppas equation of 20–23% and by an increase in the slope of Higuchi plots of 12–18% for four lots of tablets. In vivo/in vitro relationships from two bioavailability studies were thoroughly evaluated. Using either a linear or a quadratic relationship, an in vivo/in vitro correlation exists for sustained-release adinazolam mesylate tablets. 相似文献
46.
47.
E. Wieczerzak E. Jankowska S. Rodziewicz‐Motowido A. Giedo J. giewka Z. Grzonka M. Abrahamson A. Grubb D. Brmme 《Chemical biology & drug design》2005,66(Z1):1-11
Abstract: We have designed and synthesized a new series of azapeptides which act as potential inhibitors of cathepsin B and/or cathepsin K. Their structures are based upon the inhibitory sites of natural cysteine protease inhibitors, cystatins. For the synthesized azapeptides, the equilibrium constants for dissociation of inhibitor–enzyme complex, Ki, were determined. Comparison of these values indicated that all of the azainhibitors act much stronger toward cathepsin B. Z‐Arg‐Leu‐His‐Agly‐Ile‐Val‐OMe ( 7 ) proved to be approximately 500 times more potent for cathepsin B than for cathepsin K. To be able to explain the obtained experimental values we used the molecular dynamics procedures to analyze the interactions between cathepsin B and compound 7 . We also determined the structure of the most potent and selective cathepsin B azainhibitor by means of NMR studies and theoretical calculations. In this report, we describe SAR studies of azapeptide inhibitors indicating the influence of the conformational flexibility of the examined compounds on inhibition of cathepsins B and K. 相似文献
48.
49.
Lesley B Milgrom Jo Ann Brooks Rong Qi Karen Bunnell Susie Wuestfeld Daniel Beckman 《American journal of critical care》2004,13(2):116-125
BACKGROUND: Acute pain is common after cardiac surgery and can keep patients from participating in activities that prevent postoperative complications. Accurate assessment and understanding of pain are vital for providing satisfactory pain control and optimizing recovery. OBJECTIVES: To describe pain levels for 5 activities expected of patients after cardiac surgery on postoperative days 1 to 6 and changes in pain levels after chest tube removal and extubation. METHODS: Adults who underwent cardiac surgery were asked to rate the pain associated with various types of activities on postoperative days 1 to 6. Pain levels were compared by postoperative day, activity, and type of cardiac surgery. Pain scores before and after chest tube removal and extubation also were analyzed. RESULTS: Pain scores were higher on earlier postoperative days. The order of overall pain scores among activities (P < .01) from highest to lowest was coughing, moving or turning in bed, getting up, deep breathing or using the incentive spirometer, and resting. Changes in pain reported with coughing (P = .03) and deep breathing or using the incentive spirometer (P = .005) differed significantly over time between surgery groups. After chest tubes were discontinued, patients had lower pain levels at rest (P = .01), with coughing (P = .05), and when getting up (P = .03). CONCLUSIONS: Pain relief is an important outcome of care. A comprehensive, individualized assessment of pain that incorporates activity levels is necessary to promote satisfactory management of pain. 相似文献
50.
Thomas J Beck Anne C Looker Firas Mourtada Maithili M Daphtary Christopher B Ruff 《Journal of bone and mineral research》2006,21(9):1425-1432
Age trends in proximal femur stresses were evaluated by simulating a fall on the greater trochanter using femur geometry from hip DXA scans of 5334 white men and women in the NHANES III survey. Expansion of femur outer diameter seems to counter net bone loss so that stresses remain similar across age groups, but stresses are higher in older women than in older men. INTRODUCTION: The age decline in hip BMD is caused by both bone loss and expansion of outer diameter that increases the region size over which mass is measured in a DXA scan. Because expansion has an opposing effect on structural strength, it may be a homeostatic adaptation to net bone loss to ensure that load stresses are kept within a narrow range. MATERIALS AND METHODS: Age trends in femur stresses were evaluated with an engineering beam simulation of a fall on the greater trochanter. Hip geometry was extracted from hip DXA scans using the Hip Structure Analysis (HSA) software on 2613 non-Hispanic white men and 2721 women from the third National Health and Nutrition Examination Survey (NHANES III). Using body weight as load, stresses were computed on the inferior-medial and superior-lateral femur neck at its narrowest point and the medial and lateral shaft 2 cm distal to the midpoint of the lesser trochanter. Stresses and the underlying geometries in men and women >50 years oaf age were compared with those 20-49 years of age. RESULTS: Compared with men <50 years of age, stresses in older men were 6% lower on both surfaces of the shaft, 4% lower on the inferior-medial neck, and not different on the superior-lateral neck. In women >50 years of age, stresses on the proximal shaft and inferior-medial neck remained within 3% of young values but were 13% greater on the superior-lateral neck. Neck stresses in young women were lower on the superior-lateral than the inferior-medial neck, but lateral stress increased to the level on the medial surface in older women. Stresses were higher in women than in men, with a greater gender difference in those >50 years of age. CONCLUSIONS: We conclude that femur expansion has a homeostatic effect in men and women that opposes bone loss so that stresses change little with age. Because expansion preserves stresses with progressively less bone mass, the process may reduce structural stability in the femoral neck under fall conditions, especially in the elderly female. 相似文献