全文获取类型
收费全文 | 1793篇 |
免费 | 114篇 |
国内免费 | 24篇 |
专业分类
耳鼻咽喉 | 5篇 |
儿科学 | 63篇 |
妇产科学 | 17篇 |
基础医学 | 285篇 |
口腔科学 | 17篇 |
临床医学 | 160篇 |
内科学 | 416篇 |
皮肤病学 | 9篇 |
神经病学 | 205篇 |
特种医学 | 225篇 |
外科学 | 172篇 |
综合类 | 13篇 |
预防医学 | 94篇 |
眼科学 | 51篇 |
药学 | 142篇 |
肿瘤学 | 57篇 |
出版年
2021年 | 14篇 |
2020年 | 16篇 |
2019年 | 19篇 |
2018年 | 18篇 |
2017年 | 10篇 |
2016年 | 26篇 |
2015年 | 21篇 |
2014年 | 27篇 |
2013年 | 53篇 |
2012年 | 45篇 |
2011年 | 69篇 |
2010年 | 41篇 |
2009年 | 52篇 |
2008年 | 74篇 |
2007年 | 79篇 |
2006年 | 65篇 |
2005年 | 88篇 |
2004年 | 59篇 |
2003年 | 41篇 |
2002年 | 66篇 |
2001年 | 58篇 |
2000年 | 44篇 |
1999年 | 46篇 |
1998年 | 47篇 |
1997年 | 40篇 |
1996年 | 47篇 |
1995年 | 31篇 |
1994年 | 23篇 |
1993年 | 36篇 |
1992年 | 20篇 |
1991年 | 22篇 |
1990年 | 39篇 |
1989年 | 37篇 |
1988年 | 36篇 |
1987年 | 41篇 |
1986年 | 26篇 |
1985年 | 26篇 |
1984年 | 15篇 |
1983年 | 22篇 |
1982年 | 25篇 |
1981年 | 14篇 |
1980年 | 22篇 |
1979年 | 11篇 |
1977年 | 22篇 |
1976年 | 26篇 |
1975年 | 17篇 |
1974年 | 14篇 |
1972年 | 13篇 |
1970年 | 13篇 |
1969年 | 18篇 |
排序方式: 共有1931条查询结果,搜索用时 15 毫秒
1.
We investigated the effect of oral contraceptives with low and high estrogen concentration on blood coagulation and thrombogenesis, induced by vascular subendothelium of rabbit aorta exposed to flowing human blood. Twenty healthy women intending to take oral contraceptives were studied [1] before drug ingestion (control), and subsequently during the intake of oral contraceptives with [2] low estrogen content (20 micrograms ethinyl estradiol and 150 micrograms desogestrel per day) and [3] high estrogen content (50 micrograms ethinyl estradiol and 125 micrograms desogestrel per day). All experiments were performed between day 17 and 21 of the menstrual cycle and drug effects were studied during the third tablet cycle. Deposition of fibrin, platelets and platelet thrombi on vascular subendothelium was tested at a defined blood flow and wall shear rate (10 ml/min, 650 s-1) and was quantified by morphometrical techniques. Treatment with the low and high dose contraceptive increased the plasma levels of ethinyl estradiol (728 +/- 139 and 1438 +/- 212 vs. 0 fmol/l [low and high dose vs. control], means +/- SEM, P less than 0.001) and fibrinogen (2.3 +/- 0.1 and 2.6 +/- 0.1 vs. 2.0 +/- 0.1 g/l, P less than 0.05); and decreased antithrombin III activity (95 +/- 3 and 92 +/- 3 vs. 101 +/- 3 %, P less than 0.05). Fibrin deposition on vascular subendothelium was enhanced by the high dose contraceptive only (47 +/- 4 vs. 35 +/- 4 % coverage of the subendothelial surface with fibrin, high dose vs. control, P less than 0.05). The subendothelial deposition of platelets and platelet thrombi was not changed by contraceptive treatment. These results indicate that treatment with high dose contraceptives leads to an increase of fibrin-subendothelial interactions, whereas low dose contraceptives do not significantly alter the blood-subendothelium interactions. observed in this ex vivo model of thrombogenesis. 相似文献
2.
Hysterosalpingography was performed in 31 patients by means of a low-dose scanning-beam digital radiographic system. The technique permits adequate evaluation of gynecologic abnormalities while allowing significant reduction in radiation: 2.4-mR (6.1 X 10(-7) C/kg) exposure to the skin and 0.7-mrad (7 X 10(-6) Gy) mean dose to the ovaries per image obtained. Sixteen patients demonstrated readily recognizable and documented abnormalities, corroborated by laparoscopy, laparotomy, or other supportive evidence. 相似文献
3.
Coronary reperfusion of ischemic myocardium may be beneficial but is highly dependent upon occlusion and reperfusion times. To study the effects of early reperfusion on ischemic myocardium, 24 open chest pigs underwent coronary occlusion; one group was occluded for 40 min, and the other was occluded for 30 min followed by 10 min of reperfusion. Left ventricular wall thickness during systole and diastole was determined by ultrasound. Mitochondrial energy production and calcium content were evaluated from ischemic and nonischemic areas. Results showed: There was an absence of systolic thickness, a slight decrease of diastolic thickness from baseline, and a decrease in energy production in the ischemic myocardium. Reperfusion resulted in a diverse pattern of systolic and diastolic wall thickness in the ischemic area and a variable Ca2+ accumulation and mitochondrial ATP production. The variability of myocardial Ca2+ accumulation in the ischemic reperfused group correlated inversely with mitochondrial ATP production (r = -0.94) and directly with diastolic wall thickness (r = 0.65). Similarly, calcium accumulation, ATP production, and diastolic wall thickness correlated with mean blood pressure during reperfusion. These results suggest that many factors including individual characteristics of the animal and experimental conditions such as the level of blood pressure and the degree of calcium accumulation may determine outcome of reperfusion even in as brief a period as 10 min. 相似文献
4.
5.
J F Newton K M Straub R H Dewey C D Perchonock M E McCarthy J G Gleason R K Lynn 《Drug metabolism and disposition》1992,20(4):479-484
A primary route of inactivation of leukotrienes and their receptor antagonists (LTRA) is metabolism by omega oxidation. SK&F 102922 [5-(2-(8-phenyloctyl)phenyl)-4,6-dithianonanedioic acid] is a LTRA that was designed to be resistant to omega oxidation. Therefore, these experiments were designed to characterize the metabolic fate of [14C]SK&F 102922. Following iv administration of SK&F 102922 (5 mg/kg), 80% of injected radioactivity was excreted in bile in 1 hr. At least five metabolites and parent (18% of administered dose) were present in bile. One metabolite (M1), which accounted for less than 10% of the excreted radioactivity, was monohydroxylated. Three metabolites (M2, M3A, and M3B), which together accounted for greater than 50% of excreted radioactivity, had mass spectra consistent with acyl glucuronides. All three metabolites were alkali labile, whereas only one metabolite (M2) was susceptible to beta-glucuronidase hydrolysis. These data indicate that M3a and M3b are nonglycosidic isomers of M2 that were formed by a nonenzymic reaction involving migration of the aglycone (SK&F 102922) from C-1 to C-2, C-3, or C-4 of glucuronic acid. The 1-O-acyl-beta-glucuronide of SK&F 102922 (M2) exhibits pH dependent rearrangement, with half-lives ranging from 1 to greater than 1000 hr. Therefore, acyl glucuronidation can account for much of the metabolic fate of SK&F 102922 and, potentially, other structurally related LTRAs or endogenous leukotrienes themselves. 相似文献
6.
7.
The RNase mismatch cleavage method was examined for its efficiency of indicating single-base sequence differences in the capsid protein-coding regions of different foot-and-mouth disease virus subtype O1 strains. The method was found suitable for indicating such differences. RNase A as well as RNase T1 contributed to substrate conversion. Examples for the cleavage of eleven different single-base mismatches in RNA double-strands are now known. All virus genomes found to differ from each other exhibited three or more non-neighboured single-base sequence differences. Other genomes found to be indistinguishable by this method were those of a recent field isolate adapted to cell culture, and those of a vaccine production strain; its progeny was transmitted to pig and cow and then analyzed. The results suggest that host change does not necessarily select for antigenic variant virus, and that virus submitted to some kind of selection pressure is changed at more than one position. 相似文献
8.
C. Straub 《Der Onkologe》1998,4(5):440-444
Die Diskussion um Standards bzw. Leitlinien in der Medizin wird in der n?heren Zukunft ein wichtiges Thema sein, inner?rztlich,
aber auch in den Kontakten und Verhandlungen zwischen Leistungserbringern und Kostentr?gern. Wie jedes Schlagwort, das in
Mode kommt, wird auch Standard mit unterschiedlichen Bedeutungen unterlegt, je nachdem, wer, in welchem Zusammenhang mit
dem Begriff operiert. Im folgenden soll die Position eines Krankenkassenverbandes beschrieben werden. 相似文献
9.
10.
Noninvasive metabolic magnetic resonance (MR) imaging reflecting glucose metabolism in the aldose-reductase-sorbitol (ARS) pathway was performed in the rabbit head; after administration of the fluorinated glucose analogue 3-fluoro-3-deoxy-D-glucose (3FD-glucose), fluorine-19 images were generated. Images of 3FD-glucose showed significant 3FD-glucose uptake by adipose tissue, indicating its buffering effects in case of excess loads of glucose. Images of 3-fluoro-3-deoxy-D-sorbitol (3FD-sorbitol) demonstrated the spatial distribution of aldose reductase activities and significant sorbitol accumulation in the lens. Images of 3-fluoro-3-deoxy-D-fructose (3FD-fructose) showed preferential uptake of fructose by muscle tissue. The extremely low toxicity of 3FD-glucose indicates promise for its clinical application in metabolic imaging. 相似文献