全文获取类型
收费全文 | 42891篇 |
免费 | 2998篇 |
国内免费 | 151篇 |
专业分类
耳鼻咽喉 | 355篇 |
儿科学 | 1461篇 |
妇产科学 | 989篇 |
基础医学 | 4993篇 |
口腔科学 | 881篇 |
临床医学 | 4391篇 |
内科学 | 9180篇 |
皮肤病学 | 743篇 |
神经病学 | 4372篇 |
特种医学 | 1363篇 |
外科学 | 6491篇 |
综合类 | 664篇 |
一般理论 | 60篇 |
预防医学 | 3376篇 |
眼科学 | 1112篇 |
药学 | 2966篇 |
中国医学 | 45篇 |
肿瘤学 | 2598篇 |
出版年
2023年 | 150篇 |
2022年 | 246篇 |
2021年 | 721篇 |
2020年 | 450篇 |
2019年 | 709篇 |
2018年 | 859篇 |
2017年 | 670篇 |
2016年 | 688篇 |
2015年 | 881篇 |
2014年 | 1247篇 |
2013年 | 1864篇 |
2012年 | 2816篇 |
2011年 | 3048篇 |
2010年 | 1715篇 |
2009年 | 1595篇 |
2008年 | 2799篇 |
2007年 | 3009篇 |
2006年 | 2930篇 |
2005年 | 3003篇 |
2004年 | 2829篇 |
2003年 | 2609篇 |
2002年 | 2603篇 |
2001年 | 398篇 |
2000年 | 248篇 |
1999年 | 423篇 |
1998年 | 634篇 |
1997年 | 467篇 |
1996年 | 419篇 |
1995年 | 371篇 |
1994年 | 317篇 |
1993年 | 314篇 |
1992年 | 271篇 |
1991年 | 229篇 |
1990年 | 221篇 |
1989年 | 212篇 |
1988年 | 204篇 |
1987年 | 175篇 |
1986年 | 201篇 |
1985年 | 203篇 |
1984年 | 298篇 |
1983年 | 251篇 |
1982年 | 323篇 |
1981年 | 288篇 |
1980年 | 282篇 |
1979年 | 167篇 |
1978年 | 164篇 |
1977年 | 160篇 |
1976年 | 140篇 |
1975年 | 127篇 |
1974年 | 140篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
71.
Gary Coleman Tom A. Gardiner Ariel Boutaud Alan W. Stitt 《Albrecht von Graefes Archiv fur klinische und experimentelle Ophthalmologie》2007,245(4):581-587
Background A recombinant form of the α2(IV)NC1 domain of type IV collagen has been shown to have potent anti-angiogenic activity although
this peptide has not been studied in the context of proliferative retinopathies. In the current investigation we examined
the potential for α2(IV)NC1 to regulate retinal microvascular endothelial cell function using a range of in vitro and in vivo
assay systems.
Materials and methods α2(IV)NC1 at concentrations between 0.1 and 1 μg/ml was added to retinal microvascular endothelial cells (RMECs) followed
by assessment of cell attachment, proliferation and survival. This agent was also tested within a novel in vitro three-dimensional
retinal angiogenesis assay and the number of angiogenic sprouts quantified. α2(IV)NC1 was also delivered intra-vitreally to
mice with oxygen-induced proliferative retinopathy (OIR) and neovascularisation evaluated in comparison with vehicle-treated
controls.
Results RMECs treated with α2(IV)NC1 (0.1, 0.5 and 1 μg/ml) showed delayed attachment at 3 h post-seeding, although this deficit had
been restored at the 6-h time point. BrdU assay of DNA replication revealed that confluent RMECs treated with α2(IV)NC1 showed
no measurable response in comparison with vehicle-treated controls. By contrast, proliferation of sub-confluent RMECs was
significantly reduced by α2(IV)NC1 at 0.5 μg/ml (P<0.01). α2(IV)NC1 also induced apoptosis in RMECs and inhibited angiogenesis of pre-existing retinal vascular networks in
vitro (P<0.001). Intra-vitreal injection of α2(IV)NC1 in the OIR model significantly inhibited pre-retinal neovascularisation compared
with vehicle-treated controls (P<0.001).
Conclusion α2(IV)NC1 inhibits angiogenesis in the retinal microvasculature. This recombinant protein has potential for the treatment
of neovascularisation in proliferative retinopathies.
BioStratum Inc. did not sponsor this research in any way. None of the authors are paid consultants with this company. 相似文献
72.
Maurizio Massi Giuseppe De Caro Luigi Mazzarella Alan N. Epstein 《Brain research》1986,381(2):289-299
Pigeons with radiofrequency lesions that damaged the subfornical organ (SFO) (n = 4) or that isolated it from adjacent structures (n = 5), but not sham-lesioned pigeons, were unresponsive to blood-borne (i.p.) ANG II (100 micrograms/pigeon) in the immediate postoperative period and for 60 days thereafter. These animals were less sensitive to hypovolemic challenge (20% PEG), but they responded normally to 24 h of water deprivation and to cellular dehydration. Despite their unresponsiveness to bloodborne ANG II, the lesioned pigeons drank normally to 10 ng of i.c.v. ANG II given as early as 10 days after surgery, and they drank reliably and vigorously but less in total volume to 100 ng i.c.v. They also drank quickly, vigorously, and in normal total volume to i.c.v. tachykinins and bombesins, and to the peripheral (i.p.) bombesins. Peripheral (i.m.) tachykinins produced only low volume and variable drinking in all birds tested regardless of brain damage. The SFO of the pigeon, like that of the mammal, is essential for drinking evoked by blood-borne ANG II and is not necessary for thirst aroused by ANG II acting from within the cerebral ventricles. Lastly, it does not mediate the dipsogenic effects of the tachykinins or the bombesins. 相似文献
73.
74.
75.
J Brent Richards William D Leslie Lawrence Joseph Kerry Siminoski David A Hanley Jonathan D Adachi Jacques P Brown Suzanne Morin Alexandra Papaioannou Robert G Josse Jerilynn C Prior K Shawn Davison Alan Tenenhouse David Goltzman 《Journal of bone and mineral research》2007,22(2):228-234
The impact of clinical risk factor-based absolute risk methods on the prevalence of high risk for osteoporotic fracture is unknown. We applied absolute risk methods to 6646 subjects and found that the prevalence of elderly women deemed to be at high risk increased substantially, whereas the overall prevalence was highly dependent on the threshold used to designate high risk. INTRODUCTION: Many groups have advocated using absolute risk methods that incorporate clinical risk factors to target patients for osteoporosis therapy. We examined how the application of such absolute risk classification systems influences the prevalence of those considered to be at high risk for osteoporotic fracture and compared these systems to one based solely on BMD. MATERIALS AND METHODS: Using 6646 subjects from the Canadian Multicentre Osteoporosis Study (CaMos), a prospective, randomly selected, population-based cohort, we assessed three different systems for determining prevalence of high risk for osteoporotic fracture: a BMD-based system; a simplified risk factor system incorporating age, sex, BMD, and two clinical risk factors; and a comprehensive system, incorporating age, sex, BMD, and seven clinical risk factors. The 10-year absolute risks of incident fragility fracture were compared across systems using three different high-risk thresholds. RESULTS: The prevalence of a T score < or = -2.5 was 18.8% (95% CI: 17.7-19.9%) in women and 3.9% (95% CI: 3.0-4.7%) in men. Using a 15% 10-year risk of fracture threshold, the prevalence of women at high risk increased to 46.9% (95% CI: 45.4-48.4) and 42.5% (95% CI: 41.1-43.9) when the comprehensive and simplified risk factor classification systems were used, respectively. Using a 25% 10-year absolute risk threshold, the prevalence of high risk was similar to that of the BMD-based system, whereas the 20% threshold gave intermediate rates. All thresholds analyzed resulted in an increased prevalence of older women at high risk for fracture, whereas only the 15% 10-year risk of fracture threshold resulted in an increase in the prevalence of men at high risk. CONCLUSIONS: The application of risk factor-based systems results in an increased prevalence of older women at high risk. The prevalence of individuals at high risk may increase with changes to the methods used to determine those who are eligible for therapy. These data have important implications for the pattern of care and costs of treating osteoporotic fractures. 相似文献
76.
We describe the use of a double-strand peroneus brevis allograft to reconstruct the coracoclavicular and acromioclavicular (AC) joint ligaments. Through sharp dissection, the distal clavicle, the AC joint, and the torn superior AC and coracoacromial ligaments are identified. The coracoid process and injured coracoclavicular ligaments are identified with blunt dissection. A 1-cm segment of the lateral clavicle is resected. Vertical and connecting horizontal tunnels are created (4.5 mm) in the lateral clavicle and in the medial acromion process. The 5.5- to 6.0-mm-diameter allograft is looped around the coracoid process, and both strands are passed through the vertical clavicle tunnel with a nitinol wire loop. One strand passes through the vertical clavicle tunnel, and the other strand passes through the horizontal tunnel, exiting through the lateral end. The allograft strand passed through the vertical clavicle tunnel is then passed inferiorly through the superior vertical acromion tunnel, and the strand passed completely through the horizontal clavicle tunnel is passed laterally through the medial horizontal acromion tunnel. After both strands exit inferiorly through the vertical acromion tunnel, they are tensioned and sutured with AC joint reduction. Soft tissue closure uses No. 0 and No. 2-0 absorbable sutures with No. 3-0 nylon sutures at the skin. 相似文献
77.
78.
79.
80.
Steven N Singh X Charlene Tang Bramah N Singh Paul Dorian Domenic J Reda Crystal L Harris Ross D Fletcher Satish C Sharma J Edwin Atwood Alan K Jacobson H Daniel Lewis Becky Lopez Dennis W Raisch Michael D Ezekowitz 《Journal of the American College of Cardiology》2006,48(4):721-730
OBJECTIVES: The purpose of this study was to determine quality of life (QOL) and exercise performance (EP) in patients with persistent atrial fibrillation (AF) converted to sinus rhythm (SR) compared with those remaining in or reverting to AF. BACKGROUND: Restoration of SR in patients with AF improving QOL and EP remains controversial. METHODS: Patients with persistent AF were randomized double-blind to amiodarone, sotalol, or placebo. Those not achieving SR at day 28 were cardioverted and classified into SR or AF groups at 8 weeks (n = 624) and 1 year (n = 556). The QOL (SF-36), symptom checklist (SCL), specific activity scale (SAS), AF severity scale (AFSS), and EP were assessed. RESULTS: Favorable changes were seen in SR patients at 8 weeks in physical functioning (p < 0.001), physical role limitations (p = 0.03), general health (p = 0.002), and vitality (p < 0.001), and at 1 year in general health (p = 0.007) and social functioning (p = 0.02). Changes in the scores for SCL severity (p = 0.01), functional capacity (p = 0.003), and AFSS symptom burden (p < 0.001) at 8 weeks and in SCL severity (p < 0.01) and AF symptom burden (p < 0.001) at 1 year showed significant improvements in SR versus AF. Symptomatic patients were more likely to have improvement. The EP in SR versus AF was greater from baseline to 8 weeks (p = 0.01) and to 1 year (p = 0.02). The EP correlated with physical functioning and functional capacity except in the AF group at 1 year. CONCLUSIONS: In patients with persistent AF, restoration and maintenance of SR was associated with improvements in QOL measures and EP. There was a strong correlation between QOL measures and EP. 相似文献