全文获取类型
收费全文 | 2745篇 |
免费 | 175篇 |
国内免费 | 6篇 |
专业分类
耳鼻咽喉 | 13篇 |
儿科学 | 162篇 |
妇产科学 | 61篇 |
基础医学 | 295篇 |
口腔科学 | 35篇 |
临床医学 | 207篇 |
内科学 | 955篇 |
皮肤病学 | 34篇 |
神经病学 | 159篇 |
特种医学 | 77篇 |
外科学 | 296篇 |
综合类 | 53篇 |
一般理论 | 1篇 |
预防医学 | 104篇 |
眼科学 | 51篇 |
药学 | 264篇 |
中国医学 | 22篇 |
肿瘤学 | 137篇 |
出版年
2022年 | 19篇 |
2021年 | 56篇 |
2020年 | 29篇 |
2019年 | 40篇 |
2018年 | 51篇 |
2017年 | 47篇 |
2016年 | 47篇 |
2015年 | 47篇 |
2014年 | 73篇 |
2013年 | 103篇 |
2012年 | 156篇 |
2011年 | 136篇 |
2010年 | 116篇 |
2009年 | 79篇 |
2008年 | 123篇 |
2007年 | 126篇 |
2006年 | 120篇 |
2005年 | 121篇 |
2004年 | 135篇 |
2003年 | 93篇 |
2002年 | 101篇 |
2001年 | 90篇 |
2000年 | 120篇 |
1999年 | 79篇 |
1998年 | 29篇 |
1997年 | 34篇 |
1996年 | 23篇 |
1995年 | 24篇 |
1994年 | 14篇 |
1993年 | 18篇 |
1992年 | 68篇 |
1991年 | 53篇 |
1990年 | 40篇 |
1989年 | 53篇 |
1988年 | 40篇 |
1987年 | 42篇 |
1986年 | 43篇 |
1985年 | 56篇 |
1984年 | 41篇 |
1983年 | 29篇 |
1981年 | 13篇 |
1980年 | 16篇 |
1979年 | 23篇 |
1978年 | 11篇 |
1975年 | 12篇 |
1974年 | 15篇 |
1973年 | 14篇 |
1971年 | 12篇 |
1970年 | 10篇 |
1968年 | 10篇 |
排序方式: 共有2926条查询结果,搜索用时 15 毫秒
1.
Effect of long-term treatment of two tobacco-specific N-nitrosamines on the vitamin A status of mice
The effect of long-term treatment of two important tobacco-specific N-nitrosamines, N'-nitrosonornicotine (NNN) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), on the depot or circulating levels of vitamin A of Swiss and BALB/c male mice was studied. It was observed that treatment of both NNN and NNK in Swiss and BALB/c mice decreased liver vitamin A levels significantly. NNK treatment also caused a decrease in the levels of vitamin A in plasma. 相似文献
2.
3.
4.
D. Le Elizabeth Eric R. Powers Jian-Ping Bin Howard Leong-Poi N. Craig Goodman Sanjiv Kaul 《Journal of nuclear cardiology》2007,14(2):207-214
Background The mechanism by which transmyocardial revascularization (TMR) offers clinical benefit is controversial. We hypothesized that
TMR ameliorates ischemia by reversing paradoxical catecholamine-induced vasoconstriction.
Methods and Results Chronic ischemic cardiomyopathy was created in 11 dogs by placing ameroid constrictors on the proximal coronary arteries and
their major branches. Six weeks later, 35 channels were created percutaneously in the left circumflex artery region, with
the left anterior descending artery region serving as control. At rest, wall thickening and myocardial blood flow did not
change in the treated region, whereas they deteriorated in the control bed. Contractile and myocardial blood flow reserve
increased in the treated region but deteriorated in the control region. There was diminished iodine 123 metaiodobenzylguanidine
uptake and a significant reduction in noradrenergic nerves in the treated region compared with the control region, with a
corresponding reduction in tissue tyrosine hydroxylase activity.
Conclusions We conclude that the absence of a catecholamine-induced reduction in MBF reserve and contractile reserve in the TMR-treated
region with associated evidence of neuronal injury indicates that the relief of exercise-induced ischemia after TMR most likely
results from reversal of paradoxical catecholamine-induced vasoconstriction. These findings may have implications in selecting
patients who would benefit from TMR.
Supported in part by grants from the National Institutes of Health (R01-HL66034 and K-08-HL074290-01). Bethesda. Md. The radio-labeled
microspheres were provided by DuPont Pharmaceuticals, North Billerica. Mass, and the ultrasound equipment was supplied by
Philips. Andover, Mass. Dr Leong-Poi was the recipient of a Fellowship Training Grant from the Canadian Institute of Health
Research and the Heart and Stroke Foundation of Canada. 相似文献
5.
We compared the antihypertensive effects and tolerability of a new calcium channel antagonist felodipine with nifedipine in an open randomised parallel group study in 49 patients with moderate hypertension (diastolic blood pressure 105-120 mm Hg). After two weeks run in period felodipine 5 mg and 10 mg once daily was compared with nifedipine 10 mg tid for an active treatment period of 4 weeks. Twenty three patients (mean age 42 +/- 10 years) received felodipine 5 mg once daily for first 2 weeks and 10 mg once daily for subsequent 2 weeks. Twenty six patients (mean age 45 +/- 9 years) received nifedipine 10 mg tid for 4 weeks. The mean reduction in supine diastolic blood pressure in two groups was 17 +/- 6 mm Hg (nifedipine) and 19 +/- 8 mm Hg (felodipine) (p = NS). The goal diastolic blood pressure of less than or equal to 90 mm Hg was achieved in 31 percent (nifedipine group) and 43.5 percent (felodipine group) of patients (p = NS). Side effects were common with both drugs; however, the tolerability was better with felodipine than with nifedipine. In conclusion felodipine was as effective as nifedipine and had the advantage of once a day dosage. 相似文献
6.
Mycoplasma pneumoniae Induces Chronic Respiratory Infection, Airway Hyperreactivity, and Pulmonary Inflammation: a Murine Model of Infection-Associated Chronic Reactive Airway Disease 总被引:9,自引:0,他引:9 下载免费PDF全文
Robert D. Hardy Hasan S. Jafri Kurt Olsen Jeanine Hatfield Janie Iglehart Beverly B. Rogers Padma Patel Gail Cassell George H. McCracken Octavio Ramilo 《Infection and immunity》2002,70(2):649-654
Because chronic Mycoplasma pneumoniae respiratory infection is hypothesized to play a role in asthma, the potential of M. pneumoniae to establish chronic respiratory infection with associated pulmonary disease was investigated in a murine model. BALB/c mice were intranasally inoculated once with M. pneumoniae and examined at 109, 150, 245, 368, and 530 days postinoculation. M. pneumoniae was detected in bronchoalveolar lavage fluid by culture or PCR in 70 and 22% of mice at 109 and 530 days postinoculation, respectively. Lung histopathology was normal up to 368 days postinoculation. At 530 days, however, 78% of the mice inoculated with M. pneumoniae demonstrated abnormal histopathology characterized by peribronchial and perivascular mononuclear infiltrates. A mean histopathologic score (HPS) at 530 days of 5.1 was significantly greater (P < 0.01) than that for controls (HPS score of 0). Serum anti-M. pneumoniae immunoglobulin G was detectable in all of the mice inoculated with M. pneumoniae and was inversely correlated with HPS (r = -0.95, P = 0.01) at 530 days postinoculation. Unrestrained whole-body plethysmography measurement of enhanced pause revealed significantly elevated airway methacholine reactivity in M. pneumoniae-inoculated mice compared with that in controls at 245 days (P = 0.03) and increased airway obstruction at 530 days (P = 0.01). Murine M. pneumoniae respiratory infection can lead to chronic pulmonary disease characterized by airway hyperreactivity, airway obstruction, and histologic inflammation. 相似文献
7.
Trauma is the third most common cause of death in the West. In the US, approximately 90,000 deaths annually are traumatic
in nature and over 75% of casualties from blunt trauma are due to chest injuries. Cardiac injuries from rib fractures following
blunt trauma are extremely rare. We report the unusual case of a patient who fell from a height and presented with haemopericardium
and haemothorax as a result of left ventricular and lingular lacerations and was sucessfully operated upon. 相似文献
8.
目的:探讨小容积动物线圈3.0T临床磁共振扫描仪体外示踪磁标记间充质干细胞的可行性。方法:用GFP转染法将含有不同剂量铁(56ug/ml和560ug/m1)的超顺磁氧化铁(SPIO)标记间充质干细胞。细胞内铁的含量利用原子吸收谱来测量。磁共振扫描和显微镜可以观察培养试管中的磁标记间充质干细胞。 相似文献
9.
Ohne Zusammenfassung 相似文献
10.
Didanosine (ddl) and stavudine (d4T): Absence of peripheral neurotoxicity in rabbits 总被引:1,自引:0,他引:1
W. A. Warner C. L. Bregman C. R Comereski J. C. Arezzo T. J. Davidson C. A. Knupp S. Kaul S. K. Durham A. J. Wasserman J. D. Frantz 《Food and chemical toxicology》1995,33(12):1047-1050
Some 20 male New Zealand White rabbits (five/group) were given either didanosine (ddl) or stavudine (d4T) at 750 and 1500 mg/kg body weight/day by oral intubation for 24 wk. An additional group was given 300 mg/kg body weight/day zidovudine (AZT) as a negative control. After 13 weeks the high dose of ddl was lowered from 1500 to 1000 mg/kg body weight/day following the death of one rabbit and continued inappetence in the dose group. The rabbits were observed daily, plasma drug levels were monitored, and electrophysiological measurements of peripheral nerve conduction were performed during the study. Additionally, body weight and food intake were recorded, and clinicopathological parameters were evaluated. Sections of selected peripheral nerves, and dorsal and ventral spinal nerve roots were examined by light and transmission electron microscopy. Although peripheral neuropathy has been reported in rabbits with the nucleoside analogue zalcitabine (ddC), based on clinical observations, electrophysiological measurements, and light and electron microscopy, no evidence of peripheral neurotoxicity was observed in rabbits given either ddl or d4T. 相似文献