全文获取类型
收费全文 | 402788篇 |
免费 | 26044篇 |
国内免费 | 6555篇 |
专业分类
耳鼻咽喉 | 5349篇 |
儿科学 | 11859篇 |
妇产科学 | 12585篇 |
基础医学 | 57681篇 |
口腔科学 | 9482篇 |
临床医学 | 38379篇 |
内科学 | 72810篇 |
皮肤病学 | 7230篇 |
神经病学 | 26881篇 |
特种医学 | 15215篇 |
外国民族医学 | 84篇 |
外科学 | 58093篇 |
综合类 | 22602篇 |
现状与发展 | 24篇 |
一般理论 | 183篇 |
预防医学 | 26192篇 |
眼科学 | 9836篇 |
药学 | 31689篇 |
56篇 | |
中国医学 | 5625篇 |
肿瘤学 | 23532篇 |
出版年
2022年 | 4795篇 |
2021年 | 7200篇 |
2020年 | 4912篇 |
2019年 | 5518篇 |
2018年 | 7175篇 |
2017年 | 5600篇 |
2016年 | 5930篇 |
2015年 | 7916篇 |
2014年 | 10220篇 |
2013年 | 12281篇 |
2012年 | 16694篇 |
2011年 | 17817篇 |
2010年 | 11183篇 |
2009年 | 9418篇 |
2008年 | 14071篇 |
2007年 | 15182篇 |
2006年 | 14901篇 |
2005年 | 14820篇 |
2004年 | 12657篇 |
2003年 | 11731篇 |
2002年 | 10929篇 |
2001年 | 15756篇 |
2000年 | 16298篇 |
1999年 | 14136篇 |
1998年 | 4634篇 |
1997年 | 4295篇 |
1996年 | 3967篇 |
1995年 | 3724篇 |
1994年 | 3341篇 |
1993年 | 2868篇 |
1992年 | 9309篇 |
1991年 | 9259篇 |
1990年 | 8945篇 |
1989年 | 8680篇 |
1988年 | 7904篇 |
1987年 | 7605篇 |
1986年 | 7151篇 |
1985年 | 6850篇 |
1984年 | 4982篇 |
1983年 | 4294篇 |
1979年 | 4549篇 |
1978年 | 3293篇 |
1977年 | 2793篇 |
1975年 | 2887篇 |
1974年 | 3401篇 |
1973年 | 3406篇 |
1972年 | 3154篇 |
1971年 | 2990篇 |
1970年 | 2869篇 |
1969年 | 2610篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
Bronchoalveolar lavage fluid neutrophils were studied by the cytologic methods in 58 patients with chronic bronchitis, 63 ones with bronchiectasis, and 8 normal controls. The study included cytospectrophotometry of myeloperoxidase and alkaline phosphatase activity and estimation of active oxygen-producing cells in the NBT test. Neutrophilic functional activity was different in the patients with chronic bronchitis and bronchiectasis. Neutrophilic myeloperoxidase and alkaline phosphatase activities were lower in the patients with chronic bronchitis than in those with bronchiectasis, whereas the counts of cells active in the NBT test were low in both patient populations. 相似文献
52.
53.
54.
The authors suggest additional criteria evidencing inflammations in the gallbladder and colloid stability of the bile: bile acid absorption and cholesterol sedimentation coefficients. Derivation of these coefficients is based on biochemical examination of the bile with measurements of bile acid, cholesterol, and bilirubin concentrations in both portions. The results of examinations of 99 subjects evidence the diagnostic value and specificity of the characteristics, and availability of this method for clinical practice. 相似文献
55.
Z M Huang D Thewke Q Q Gong D Schlichter W D Wicks 《Brain research. Molecular brain research》1991,11(3-4):309-319
Transient transfection of pLB2CAT constructs bearing short synthetic oligonucleotides derived either from the tyrosine hydroxylase (TH) promoter or other sources was used to examine functional cAMP regulatory element (CRE) activity in a variety of cell lines. The region containing only the putative TH CRE was found to be as or more effective in conferring cAMP responsiveness onto pLB2CAT (which employs the TK promoter) than the immediate 272 bp region of the TH promoter. Increases in CAT activity of 10- to 20-fold were observed in JEG-3 cells with a single insert of the TH CRE region (-31 to -54) in pLB2CAT, and the presence of a second insert generated only a modest further increase. This construct also responded to cAMP in 4 other cell lines tested but the degree of increase was less dramatic. Inserts containing the consensus 8 bp CRE motif embedded in other natural or artificial contexts served generally as weak functional CREs in all cell lines tested. In vitro analysis revealed that a specific protein-DNA complex apparently containing a single protein with a MW of 45-50 kDa was formed equally well with JEG-3 cell nuclear extract and CRE-bearing-TH and other fragments which produced dramatically different cAMP effects in vivo. These results suggest specificity in the effects of cAMP on different CREs which are dictated by contextual differences. 相似文献
56.
Iver A. Langmoen Tryggve Lundar Ingebjørg Storm-Mathisen Sverre O. Lie Karl H. Hovind 《Child's nervous system》1991,7(1):13-15
We present 36 consecutive patients with intrinsic glioma of the pons. Tumors with exophytic expansion were excluded. There were 16 females and 20 males, ranging in age from 2 to 13 years, median 6 years. The most common presenting symptoms were cranial nerve dysfunction. unsteadiness of gait, and hemiparesis. Computed tomography (CT) showed a hypodense (17/21) or isodense (4/21) expansion of the pons. Five tumors had areas of contrast enhancement. Following information about prognosis and possible types of management, parents decided for or against radiation therapy: twentyfour children underwent irradiation and 12 did not. Median survival among children receiving a full course of irradiation was 280 days, compared to 140 days in an equivalent group of non-irradiated children. Hemiparesis presenting without cranial nerve symptoms and contrast enhancement on CT scan were poor prognostic factors, whereas sex, age, and duration of symptoms at diagnosis were unrelated to prognosis. 相似文献
57.
Extracellular 5-HT in the anterior hypothalamus/preoptic area (AH/POA) and caudate nucleus of the freely moving cat was measured using in vivo brain microdialysis. Administration of 8-OH-DPAT, a 5-HT1A receptor agonist that decreases 5-HT neuronal activity, decreased extracellular 5-HT in both brain areas. Extracellular 5-HT levels were also examined in relationship to the sleep-wake cycle, because previous data from our laboratory have indicated that behavioral state is the primary determinant of 5-HT neuronal discharge. As with 5-HT neuronal discharge, extracellular 5-HT was increased during active behavioral states and decreased during somnolent periods. These first two sets of findings confirm the ability of the microdialysis technique to measure physiological fluctuations in extracellular 5-HT levels and support the hypothesis that neuronal discharge is a major determinant of extracellular 5-HT levels. Levels of the 5-HT metabolite 5-hydroxyindole acetic acid (5-HIAA) in the AH/POA were also responsive to changes in behavioral state and administration of 8-OH-DPAT, though fluctuations in extracellular 5-HIAA were less robust and temporally delayed. Finally, extracellular 5-HT and 5-HIAA were examined in the AH/POA during fever induced by systemic injection of the synthetic pyrogen muramyl dipeptide. Previous data from our laboratory have indicated that 5-HT neuronal activity is unaffected by this manipulation, though 5-HT has been implicated specifically in thermoregulation. Pyrogen-induced hypothermia produced no specific change in 5-HT efflux, because any changes noted could be accounted for by behavioral state changes. These data are consistent with the hypothesis that the brain serotonergic system is closely linked to the sleep-wake-arousal cycle. However, extracellular 5-HT may be involved in thermoregulatory processes as part of a global role in modulating neuronal activity in coordination with the behavioral state of the animal. 相似文献
58.
59.
Dependence of blood clot lysis on the mode of transport of urokinase into the clot--a magnetic resonance imaging study in vitro 总被引:4,自引:0,他引:4
A Blinc G Planinsic D Keber O Jarh G Lahajnar A Zidans?k F Demsar 《Thrombosis and haemostasis》1991,65(5):549-552
Magnetic resonance imaging was employed to study the dependence of clot lysing patterns on two different modes of transport of urokinase into whole blood clots. In one group of clots (nonperfused clots, n1 = 10), access of urokinase to the fibrin network was possible by diffusion only, whereas in the other group (perfused clots, n2 = 10) bulk flow of plasma containing urokinase was instituted through occlusive clots by a pressure difference of 3.7 kPa (37 cm H2O) across 3 cm long clots with a diameter of 4 mm. It was determined separately that this pressure difference resulted in a volume flow rate of 5.05 +/- 2.4 x 10(-2) ml/min through occlusive clots. Perfused clots diminished in size significantly in comparison to nonperfused ones already after 20 min (p less than 0.005). Linear regression analysis of two-dimensional clot sizes measured by MRI showed that the rate of lysis was more than 50-times faster in the perfused group in comparison to the nonperfused group. It was concluded that penetration of the thrombolytic agent into clots by perfusion is much more effective than by diffusion. Our results might have some implications for understanding the differences in lysis of arterial and venous thrombi. 相似文献
60.
Laterality of cross-modal spatial processing 总被引:1,自引:0,他引:1
J O Adams P D Duda 《Cortex; a journal devoted to the study of the nervous system and behavior》1986,22(4):539-552
This study examined the laterality of spatial-form perception in normal adults using a cross-modal matching paradigm involving visual and tactile processing. Randomly generated eight-point and 12-point Vanderplas and Garvin (1959) patterns were used as the stimuli. In a visual-to-tactile task, a lateralized visual pattern was followed immediately by a haptic task requiring subjects to discriminate which of two simultaneously felt shapes matched the visual pattern. In a tactile-to-visual task, subjects decided which of two simultaneously felt shapes matched a lateralized visual pattern presented after haptic manipulation. There were no main effects for laterality or for sex differences. Matching accuracy was better in the visual-to-tactile task and for less complex stimuli. A visual field by feeling hand interaction showed best recognition accuracy when visual-feeling hand combinations on the same side of the body were used in the two matching tasks. These data reflect a stimulus-response compatibility explanation of spatial-form perception that is consistent with a behavioral and not a cerebral asymmetry model. 相似文献