全文获取类型
收费全文 | 2894篇 |
免费 | 307篇 |
国内免费 | 45篇 |
学科分类
医药卫生 | 3246篇 |
出版年
2023年 | 17篇 |
2022年 | 18篇 |
2021年 | 45篇 |
2020年 | 31篇 |
2019年 | 32篇 |
2018年 | 62篇 |
2017年 | 57篇 |
2016年 | 34篇 |
2015年 | 59篇 |
2014年 | 84篇 |
2013年 | 119篇 |
2012年 | 137篇 |
2011年 | 157篇 |
2010年 | 116篇 |
2009年 | 132篇 |
2008年 | 159篇 |
2007年 | 156篇 |
2006年 | 135篇 |
2005年 | 132篇 |
2004年 | 93篇 |
2003年 | 81篇 |
2002年 | 83篇 |
2001年 | 70篇 |
2000年 | 87篇 |
1999年 | 79篇 |
1998年 | 53篇 |
1997年 | 48篇 |
1996年 | 48篇 |
1995年 | 47篇 |
1994年 | 35篇 |
1993年 | 44篇 |
1992年 | 34篇 |
1991年 | 48篇 |
1990年 | 51篇 |
1989年 | 50篇 |
1988年 | 46篇 |
1987年 | 54篇 |
1986年 | 46篇 |
1985年 | 49篇 |
1984年 | 43篇 |
1983年 | 42篇 |
1982年 | 43篇 |
1981年 | 27篇 |
1980年 | 27篇 |
1979年 | 23篇 |
1978年 | 17篇 |
1977年 | 29篇 |
1976年 | 21篇 |
1975年 | 21篇 |
1970年 | 20篇 |
排序方式: 共有3246条查询结果,搜索用时 0 毫秒
1.
HA Carpay P Matthijsse M Steinbuch PGH Mulde 《Cephalalgia : an international journal of headache》1997,17(5):591-595
In an open, randomized cross-over study in 124 patients, we compared the efficacy, safety and patient preference of oral and subcutaneous sum triptan in the acute treatment of migraine. Patients were treated for 3 attacks or 3 months and then crossed over. Primary clinical efficacy was defined as a reduction in headache severity on a four-point self-rating scale from severe (3) or moderate (2) to mild (1) or none (0), or mild (1) to none (0). Efficacy was evaluated 2 h after the administration of subcutaneous and 4h after the administration of oral sumatriptan. Subcutaneous sumatriptan was significantly more effective than oral sumatriptan in relieving headache (over all three attacks 78% vs 61% improvement), improving clinical disability (55% vs 41 % improvement) and relieving nausea (69% vs 53%), vomiting (72% vs 32%) and phono- or photophobia (67% vs 49%). Median time to recurrence was shorter after subcutaneous (12.5 h) than after oral sumatriptan (18 h); the number of patients experiencing a recurrence was similar Patients reported more adverse events after subcutaneous sumatriptan (1.32 per attack) than after the oral form (0.85 per attack), but all adverse events were mild to moderate in intensity and of short duration. Patient opinion was more often positive after subcutaneous sumatriptan. These results may be useful in counselling patients to choose between the available marketed formulations of sumatriptan. 相似文献
2.
3.
Carcinoma of the body and tail of the pancreas. 总被引:13,自引:0,他引:13
I H Nordback R H Hruban J K Boitnott H A Pitt J L Cameron 《American journal of surgery》1992,164(1):26-31
Recently, several institutions have reported improved results in the treatment of patients with carcinoma of the head of the pancreas. In an attempt to determine whether similar trends could be demonstrated for patients with carcinoma of the body and tail of the pancreas, the records of all 113 patients with an adenocarcinoma of the body or tail of the pancreas treated at The Johns Hopkins Hospital between 1972 and 1989 were reviewed. The patients were divided into two groups: those diagnosed between 1972 and 1982 (41 patients) and those between 1983 and 1989 (72 patients). No significant differences in tumor stage were observed between the two groups. The proportion of patients who underwent surgery decreased from 68% to 47% (p = 0.02). The number of patients who had bypass operations (15% versus 17%) or pancreatic resection (5% versus 10%) was similar in the two groups, but the proportion of patients who underwent exploratory laparotomy with biopsy only decreased from 49% to 21% (p = 0.002). The postoperative 30-day mortality (7% versus 3%), postoperative morbidity (18% versus 21%), median survival (4 months versus 3 months), and the 1-year survival (8% versus 9%) did not differ significantly between the two groups. One patient survived for 6 years after resection, and another patient is still alive 3 years after resection. Thus, unlike adenocarcinoma of the head of the pancreas, it appears that treatment results for patients with adenocarcinoma of the body or tail of the pancreas have not improved in recent years, the only change being a decreased need for exploratory laparotomy with biopsy only. 相似文献
4.
5.
The protein sticking coefficient, phi, the fraction of collisions that result in adsorption, is a function of the molecular interactions between the protein and the surface. A random walk and diffusion-to-capture model was used to describe the kinetics of protein adsorption. The assumption of a constant sticking coefficient leads to a first-order model of the kinetics. A solution of the problem of adsorption from a semi-infinite medium with first-order kinetics at the boundary was obtained by numerical simulation on the computer. The results of the computer simulations match the time dependence observed experimentally. A correlation was developed to estimate phi from experimental data. phi has been found to be in the range 10(-5)-10(-8) for several protein adsorption kinetic studies reported in the literature. 相似文献
6.
EEG findings in hypomelanosis of Ito. 总被引:1,自引:0,他引:1
The EEG findings in 15 children with Hypomelanosis of Ito have been reviewed and related to the clinical and CT scan data. Although no consistent electroclinical associations were found in the group as a whole, there was some association between the presence of abnormal rhythmic EEG activity and the radiological appearances of neuronal migration defects. In addition, the possibility is raised that there may be a distinctive sub-group of children with Ito's syndrome who present with an early onset of intractable seizures and who have a neuronal migration defect. 相似文献
7.
超细β-磷酸三钙/聚-L-乳酸复合材料的制备与骨折内固定器的加工 总被引:3,自引:0,他引:3
目的:制备分散性良好的超细β-磷酸三钙(β-TCP)/聚-L-乳酸(PLLA)复合材料及新型可吸收骨折内固定器。方法:通过研磨方法制备β-TCP超细粒子,用一缩二乙二醇作分散剂研磨β-TCP后,再将β-TCP与PLLA超声混合,制得复合材料,经注塑加工制成可吸收骨钉,并采用扫描电镜等方法进行表征。结果与结论:用一缩二乙二醇作分散剂研磨β-TCP后再经超声混合,可以使β-TCP超细粒子在复合材料中分散均匀,粒子大小仅为300nm左右,β-TCP与PLlA基体之间结合良好。超细β-TCP/PLLA复合材料可加工成可吸收骨钉,弯曲强度达到100MPa左右,完全满足松质骨内固定的要求。 相似文献
8.
Albumin adsorption on alkyl chain derivatized polyurethanes. II. The effect of alkyl chain length 总被引:1,自引:0,他引:1
Linear alkyl chains containing 2, 10 and 18 carbon atoms were grafted to 10% of the urethane nitrogens in a polyether-polyurethane. The polyurethane was synthesized from methylene bis(p-phenyl isocyanate), 1,4-butanediol, and polytetramethylene oxide of 1000 molecular weight in a molar ratio of 3/2/1. Fourier transform infrared spectroscopy and attenuated total reflectance optics were used to study the adsorption of 5.0 mg/ml human serum albumin (HSA) at 37 degrees C to the derivatized and non-derivatized polymers. Both delipidized HSA and HSA containing 6.5 mol stearic acid per mol of albumin were used to study the effect of chain length upon the initial adsorption rate, the total amount adsorbed in 1 h, and the desorption rate. The initial adsorption rates revealed that non-specific adsorption was similar upon all four polymers. An increase in initial adsorption rate upon the C-18 derivatized polymer was attributed to a specific binding interaction between the HSA and the grafted alkyl chains. The conformational stability of the HSA also affected the adsorption rate. The total amount adsorbed after 1 h decreased as the alkyl chain length increased from 2 to 18 methylene groups. The desorption rate decreased in magnitude as the alkyl chain length increased from C-2 to C-18. These results support a hypothesis that alkyl chain length influences the interaction between albumin and an alkylated polymer system. 相似文献
9.
10.