全文获取类型
收费全文 | 132183篇 |
免费 | 10322篇 |
国内免费 | 4864篇 |
专业分类
耳鼻咽喉 | 1840篇 |
儿科学 | 1945篇 |
妇产科学 | 1590篇 |
基础医学 | 17221篇 |
口腔科学 | 2812篇 |
临床医学 | 14638篇 |
内科学 | 20665篇 |
皮肤病学 | 3384篇 |
神经病学 | 7180篇 |
特种医学 | 6160篇 |
外国民族医学 | 25篇 |
外科学 | 14384篇 |
综合类 | 14100篇 |
现状与发展 | 18篇 |
一般理论 | 27篇 |
预防医学 | 9524篇 |
眼科学 | 2968篇 |
药学 | 13786篇 |
83篇 | |
中国医学 | 5554篇 |
肿瘤学 | 9465篇 |
出版年
2024年 | 285篇 |
2023年 | 1441篇 |
2022年 | 3911篇 |
2021年 | 5522篇 |
2020年 | 3679篇 |
2019年 | 3454篇 |
2018年 | 3936篇 |
2017年 | 3633篇 |
2016年 | 4008篇 |
2015年 | 6187篇 |
2014年 | 7624篇 |
2013年 | 8348篇 |
2012年 | 12342篇 |
2011年 | 12049篇 |
2010年 | 8170篇 |
2009年 | 6912篇 |
2008年 | 8598篇 |
2007年 | 7896篇 |
2006年 | 7215篇 |
2005年 | 6221篇 |
2004年 | 4756篇 |
2003年 | 4071篇 |
2002年 | 3461篇 |
2001年 | 2610篇 |
2000年 | 2225篇 |
1999年 | 1641篇 |
1998年 | 759篇 |
1997年 | 692篇 |
1996年 | 495篇 |
1995年 | 446篇 |
1994年 | 394篇 |
1993年 | 273篇 |
1992年 | 496篇 |
1991年 | 467篇 |
1990年 | 389篇 |
1989年 | 340篇 |
1988年 | 308篇 |
1987年 | 300篇 |
1986年 | 222篇 |
1985年 | 193篇 |
1984年 | 154篇 |
1983年 | 127篇 |
1982年 | 65篇 |
1981年 | 78篇 |
1979年 | 98篇 |
1978年 | 77篇 |
1975年 | 56篇 |
1974年 | 73篇 |
1973年 | 56篇 |
1972年 | 59篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Selective inactivation of viruses in the presence of human platelets: UV sensitization with psoralen derivatives. 下载免费PDF全文
R P Goodrich N R Yerram B H Tay-Goodrich P Forster M S Platz C Kasturi S C Park N J Aebischer S Rai L Kulaga 《Proceedings of the National Academy of Sciences of the United States of America》1994,91(12):5552-5556
Inactivation of viruses in blood products requires that the method employed display selectivity in its action for viral elements while not affecting the biological entity of interest. Several methods have been developed for the treatment of human plasma or products derived from human plasma. An effective technique for the treatment of the cellular components of blood has been lacking, in part due to the inability to develop agents capable of selectively targeting viral agents in the milieu of cellular material. In this paper, we examine the behavior of a group of viral sensitizers designed to be added to cellular samples and be activated upon exposure to UVA light. Upon activation, these agents are capable of disrupting nucleic acids of the virus in a manner that renders them inactive for proliferation. The selectivity observed in this inactivation is determined by the chemical structure of the sensitizer, which can be varied to increase viral killing capacity while diminishing collateral damage to cellular and protein constituents. 相似文献
102.
Effects of inotropes on human leucocyte numbers, neutrophil function and lymphocyte subtypes 总被引:1,自引:1,他引:0
Burns A. M.; Keogan M.; Donaldson M.; Brown D. L.; Park G. R. 《British journal of anaesthesia》1997,78(5):530-535
We have investigated the effects of inotropes with different adrenergic
receptor specificity on differential white cell count, lymphocyte subtypes
and neutrophil function in healthy volunteers. Six healthy, male volunteers
were enrolled into this randomized, placebo-controlled pilot study. Each
volunteer was studied on four separate occasions during a 2-h infusion of
various agents, and for 2 h after stopping the infusion. The agents
investigated were adrenaline 0.1 microgram kg-1 min-1, dobutamine 5
micrograms kg-1 min-1, dopexamine 2 micrograms kg-1 min-1 and 5% glucose
0.5 ml kg-1 h-1. Venous blood was sampled at 0, 30, 120 and 240 min.
Haemodynamic monitoring was continued throughout the study. Full blood
count, white cell differential count and enumeration of lymphocyte subtypes
were performed. Neutrophil function tests included chemoluminescence, and
assessment of neutrophil chemotaxis, phagocytosis and adhesion. The
Wilcoxon signed rank test was used to compare differences between placebo
and active drugs at each time compared with baseline. There was a
significant increase in white cell count, lymphocyte count and neutrophil
count with adrenaline, and a small but significant decrease in these
variables with dobutamine and dopexamine. These changes were also apparent
for absolute CD3+, CD4+ and CD8+ lymphocyte counts. Neutrophil respiratory
burst in response to f-methionyl-leucyl-phenylalanine increased
significantly only with adrenaline at 30 min (P = 0.046). There were no
other significant changes in tests of neutrophil function. Infusion of
inotropes was associated with changes in white cell numbers, lymphocyte
subtypes and neutrophil respiratory burst. In healthy volunteers,
adrenaline had effects different from those of dobutamine and dopexamine.
The clinical relevance of such effects requires further investigation in
critically ill patients.
相似文献
103.
The relationship between induction of hepatic metallothionein (MT) synthesis and lipid peroxidation by free radical production following an injection of menadione or carbon tetrachloride (CCl4) in mice was studied. The hepatic concentration of MT was increased by menadione significantly at 25 mg/kg or higher. A significant increase in thiobarbituric acid (TBA) value, indicative of lipid peroxidation, was observed in the liver at menadione doses of 62.5 mg/kg or higher. Both the MT and the TBA value in the liver were significantly increased at the low dose of CCl4. The concentration of MT was increased significantly 4-8 hr after administrations of these compounds. The increase of TBA value over time was similar to that of MT concentration after administration of CCl4, but not after administration of menadione. The MT concentration in the menadione group was higher than that in the CCl4 group, and the TBA level in the menadione group was lower than that in the CCl4 group. Pretreatment with vitamin E caused a significant reduction in the TBA value, but did not affect the MT level in the liver. The concentration of MT did not significantly correlate with the TBA value in either the menadione or the CCl4 group. Pretreatment with phenobarbital, which promotes free radical production, did not influence induction of MT synthesis following an injection of menadione or CCl4. Neither L-buthionine sulfoximine nor 2-cyclo-hexen-1-one, which decreases hepatic glutathione, influenced the induction of MT by menadione. These data suggest that induction of MT synthesis by menadione or CCl4 is independent of free radical production in the liver. 相似文献
104.
We present three unusual cases of molluscum contagiosum occurring in epidermal cysts. All of them are asymptomatic, elevated, oval nodules diagnosed clinically as epidermal inclusion cyst or prurigo nodularis. Histology showed true epidermal cysts containing molluscum bodies throughout the cyst wall and some type of laminated material within the cyst itself. The lesion, in all three cases developed in the pubic area of young adult men. 相似文献
105.
医用低值材料采供管理的探讨 总被引:4,自引:2,他引:2
医疗消耗材料是医疗工作开展的基础,本文从医用低值消耗材料的计划制定、材料采购、库房库存结构、材料供应、成本核算等多方面探讨了如何对医疗消耗材料进行科学管理,这对医院的医疗发展和管理建设有着重要意义。 相似文献
106.
The Fawn-Hooded strain of rats exhibits a hemorrhagic disorder, known as platelet storage pool deficiency. In addition to the platelet dysfunction, there is an altered response to certain serotonin drugs. To assess the characteristics of the binding to 5-HT1A and 5-HT2 receptors in this strain, regions of the brain from Fawn-Hooded, Sprague-Dawley and Wistar male rats were examined. The drug [3H]8-OH-DPAT was used to label 5-HT1A receptors and the Kd values for frontal cortex, hippocampus, striatum, hypothalamus and brainstem were similar in all three strains of rat. As with the 5-HT1A receptors, no differences were observed in the Kd values for 5-HT2 receptors, in any of the regions examined, among the three strains. However, the Bmax for the binding of [3H]8-OH-DPAT in the striatum and brainstem of Fawn-Hooded rats was less than in the Sprague-Dawley and Wistar animals. Furthermore, 5-HT2 receptors displayed a greater Bmax value in the striatum and in the frontal cortex of Fawn-Hooded animals, compared to Sprague-Dawley and Wistar rats. These differences in receptors are consistent with previous studies in which Fawn-Hooded rats were found to have altered serotonergic function, relative to Wistar and Sprague-Dawley animals. 相似文献
107.
108.
109.
A dual sensor Wiener filter (DSWF) technique was used to improve the image quality of a scanning type digital radiographic system. In a digital radiographic system, image quality is evaluated by resolution and SNR (signal-to-noise ratio), which are two important parameters representing the objective performance of the system. In this method, when two images are acquired in the same region using two sensors with different characteristics of resolution and SNR, they are processed simultaneously using DSWF, which is the extended concept of a Wiener filter to two dimensions. DSWF uses the cross power spectrum between dual sensor outputs of the same chest radiographic image in the design of filter parameters. It has been implemented with fast algorithm using FFT (fast Fourier transform). The performance of the proposed method is compared with that of conventional methods (Wiener filter and parametric projection filter). In simulation studies, it is shown in 12 cases that this new method has SNR improvement of 1-2 dB better than conventional methods. 相似文献
110.
Yoon-Ho Hong Jung-Joon Sung Kyung Seok Park Ohyun Kwon Ju-Hong Min Kwang-Woo Lee 《Clinical neurophysiology》2007,118(12):2605-2611
OBJECTIVE: To address the issue as to how best to perform statistical MUNE, we applied two different approaches and compared results in healthy subjects and ALS patients. METHODS: Twelve normal subjects (women 8, mean age 52years) and 11 ALS patients (women 4, mean age 54years) underwent two consecutive MUNE studies, which differed in terms of setting and modifying the recording window. These are referred to as the 'expansion' and 'narrowing' methods, respectively. Size-weighted average (Av) SMUP and MUNE values were obtained using the two methods, and compared in control and patient groups. RESULTS: Expansion method-derived Av SMUP sizes and MUNE values differed only slightly from those obtained using the narrowing method in healthy subjects, whereas the narrowing method resulted in significantly larger Av SMUP sizes and smaller MUNE values than the expansion method in ALS patients (Wilcoxon signed ranks test, p=0.003). The sizes of tested areas (mean+/-SD) were significantly larger for the narrowing method than the expansion method in both subject groups with much greater difference in ALS patients; 9.6+/-3.1% vs. 7.9+/-1.7% in healthy subjects and 16.1+/-5.1% vs. 11.2+/-3.0% in ALS patients (Student t-test, p<0.01). CONCLUSIONS: The present study shows, unlike that found in normal subjects, that the results of statistical MUNE in ALS patients are heavily dependent on the approach used to set and modify recording windows. SIGNIFICANCE: The expansion method using a 10%-sized window is likely to suffer from systemic errors due to the ceiling effect and the sampling of artifactually small motor units in ALS patients. The authors recommend that the narrowing method be considered as an alternative that avoids these problems. 相似文献