全文获取类型
收费全文 | 8014篇 |
免费 | 436篇 |
国内免费 | 47篇 |
专业分类
耳鼻咽喉 | 104篇 |
儿科学 | 159篇 |
妇产科学 | 189篇 |
基础医学 | 1343篇 |
口腔科学 | 168篇 |
临床医学 | 482篇 |
内科学 | 1739篇 |
皮肤病学 | 228篇 |
神经病学 | 480篇 |
特种医学 | 301篇 |
外科学 | 1342篇 |
综合类 | 24篇 |
预防医学 | 303篇 |
眼科学 | 129篇 |
药学 | 521篇 |
中国医学 | 8篇 |
肿瘤学 | 977篇 |
出版年
2023年 | 47篇 |
2022年 | 77篇 |
2021年 | 128篇 |
2020年 | 75篇 |
2019年 | 108篇 |
2018年 | 117篇 |
2017年 | 102篇 |
2016年 | 146篇 |
2015年 | 140篇 |
2014年 | 166篇 |
2013年 | 213篇 |
2012年 | 345篇 |
2011年 | 367篇 |
2010年 | 195篇 |
2009年 | 195篇 |
2008年 | 347篇 |
2007年 | 371篇 |
2006年 | 384篇 |
2005年 | 334篇 |
2004年 | 348篇 |
2003年 | 341篇 |
2002年 | 336篇 |
2001年 | 336篇 |
2000年 | 346篇 |
1999年 | 303篇 |
1998年 | 118篇 |
1997年 | 96篇 |
1996年 | 62篇 |
1995年 | 53篇 |
1994年 | 37篇 |
1993年 | 48篇 |
1992年 | 192篇 |
1991年 | 156篇 |
1990年 | 186篇 |
1989年 | 195篇 |
1988年 | 199篇 |
1987年 | 161篇 |
1986年 | 146篇 |
1985年 | 132篇 |
1984年 | 106篇 |
1983年 | 83篇 |
1979年 | 56篇 |
1978年 | 38篇 |
1977年 | 43篇 |
1975年 | 34篇 |
1974年 | 42篇 |
1973年 | 50篇 |
1972年 | 43篇 |
1970年 | 47篇 |
1968年 | 36篇 |
排序方式: 共有8497条查询结果,搜索用时 15 毫秒
81.
Suita S Taguchi T Yamanouchi T Masumoto K Ogita K Nakamura M Nakayama H Hara T Tsukimori K Nakano H Kanna T Takahashi S 《Journal of pediatric surgery》1999,34(11):1652-1657
BACKGROUND/PURPOSE: Infants with congenital diaphragmatic hernia have pulmonary hypoplasia resulting in persistent pulmonary hypertension of neonates (PPHN), which is the main contributor to both high mortality and morbidity. The pulmonary artery bed in patients with congenital diaphragmatic hernia (CDH) is underdeveloped and is very sensitive to slight stimuli. It is, therefore, vital to avoid any factors that might increase pulmonary vascular resistance during the perinatal treatment of these patients. Recently, fetal anesthesia for perinatal stabilization in patients with CDH has been reported. However, the efficacy of this method remains controversial. The aim of this study is to analyze the benefits of fetal stabilization using fetal anesthesia in patients with CDH. METHODS: The authors have seen 9 cases of antenatally diagnosed CDH and attempted fetal stabilization. The indication for fetal stabilization was a lung thoracic ratio of less than 0.2, without any severe associated anomalies. The protocol for fetal stabilization was (1) monitoring the fetal respiratory movement and heart beat by ultrasonography, (2) the administration of morphine (20 to 30 mg) and diazepam (5 mg) to the mother, (3) the confirmation of any interruptions in fetal movement followed by a cesarean section, (4) pancuronimum (0.5 mg) was given through the umbilical vessels, (5) intubation before clamping of the umbilical cord, and (6) high-frequency oscillatory ventilation (HFO) without bagging. RESULTS: The lung-thratic ratio (LTR) was between 0.06 to 0.17 (average, 0.10+/-0.04). Operation was performed in 7 of 9 patients at between 2.5 and 27 hours after birth. The overall survival rate was 66.7% (6 of 9). All of the patients who underwent operation within 5 hours after birth survived. CONCLUSIONS: Perinatal stabilization using fetal anesthesia was found to be effective in preventing PPHN and shortening the period of preoperative stabilization. It also improved the survival rate of patients with severe CDH. 相似文献
82.
The utility of three-dimensional anisotropy contrast (3DAC) magnetic resonance (MR) axonography, a method sensitive to neuronal fibers and their directionality, was investigated in the clinical setting using a 3-tesla MR imaging system based on a General Electric Signa platform. The study focused on healthy volunteers and patients with common structural central nervous system disorders, namely chronic infarction, brainstem cavernous hemangioma, supratentorial meningioma, and astrocytoma. Three orthogonal anisotropic diffusion-weighted images were first obtained. Three primary colors were each assigned to a diffusion-weighted image, respectively, and the images were subsequently combined into a single-color image in full-color spectrum (3DAC MR axonography image). Fiber-tract definition in the cerebral peduncle of the midbrain of healthy volunteers showed intersubject variation, with two general patterns recognized: dispersed (60% of cases) and compact (40% of cases). Pathological alterations in the fiber tracts were readily identified in cases involving wallerian degeneration of the pyramidal tract, as illustrated in the cases of chronic infarction. Displacement of major tracts, such as the medial lemniscus or corticospinal tract, as well as fiber directionality, was also easily recognized in cases of mass lesions. As an imaging method uniquely capable of providing information regarding axonal connectivity, 3DAC MR axonography appears to have promising potential for routine clinical application. 相似文献
83.
84.
In order to clarify the association between apolipoprotein E4 (ApoE4) and the pathogenesis of Alzheimer's disease (AD), we analyzed the distribution of the apolipoprotein E (ApoE) phenotypes and the frequency of the apo E alleles epsilon2, epsilon3, and epsilon4 in Japanese healthy controls (n = 1090, an average age of 51.2+/-12.6 years) and demented patients (n=103, mean age of 73.6+/-9.2 years). Demented subjects were divided into three subgroups: early-onset AD group (EOAD; n=25, mean age 63.0+/-6.2 years), late-onset AD group (LOAD; n=33, mean age 79.3+/-5.1 years), and vascular dementia group (VD; n=45, mean age 75.3+/-8.0 years). The apolipoprotein E phenotype was determined by isoelectric focusing and immunoblotting. There were no significant differences in the distribution of the apo E phenotypes by gender or age, and the estimated frequencies of epsilon2, epsilon3 and epsilon4 were 0.05, 0.86 and 0.09, respectively, in the normal controls. There was a significant difference in the distribution of the apo E phenotypes between LOAD and elderly controls aged more than 65 years (P<0.0001). The distribution of the apo E phenotypes in EOAD was the same as that in LOAD. The frequency of the epsilon4 allele was significantly higher in LOAD (0.35, P<0.0001) and EOAD (0.28, P<0.0001) than that in the control subjects (0.07), but not in VD (0.12, P=0.1630). The present findings suggest that ApoE4 is related with both EOAD and LOAD, but not with VD, and support the hypothesis that it is a genetic risk factor of AD. 相似文献
85.
86.
Induction of heme oxygenase-1 as a response in sensing the signals evoked by distinct nitric oxide donors. 总被引:5,自引:0,他引:5
E Hara K Takahashi K Takeda M Nakayama M Yoshizawa H Fujita K Shirato S Shibahara 《Biochemical pharmacology》1999,58(2):227-236
To gain insights into the cellular responses evoked by nitric oxide (NO), we have studied the effects of NO donors with distinct chemistries on the expression of heme oxygenase-1 mRNA by northern blot analysis. The expression levels of heme oxygenase-1 mRNA were increased significantly in DLD-1 human colorectal adenocarcinoma cells by treatment with each of three NO donors: sodium nitroprusside (SNP), S-nitroso-L-glutathione (GSNO), and 3-morpholinosydnonimine (SIN-1). A combination of SIN-1 plus SNP or GSNO additively increased heme oxygenase-1 mRNA expression, whereas synergistic induction was seen with SNP plus GSNO. The SNP-mediated induction was not affected noticeably by extracellular superoxide dismutase, catalase, or mannitol, while the induction by SIN-1 was attenuated by superoxide dismutase. Thus, the SNP-mediated induction of heme oxygenase-1 mRNA expression may be independent of reactive oxygen species, and the induction by SIN-1 is mediated partly by peroxynitrite, which is generated by immediate reaction of NO and superoxide anion. Transient transfection assays suggested that treatment with SNP, but not with GSNO or SIN-1, increased the expression of a reporter gene through a cis-acting element, including the cadmium-responsive element, of the human heme oxygenase-1 gene. These results suggest that SNP induces heme oxygenase-1 mRNA expression through a mechanism different from that for GSNO or SIN-1. We therefore propose that induction of heme oxygenase-1 represents a common cellular response in sensing the signals evoked by distinct NO donors. 相似文献
87.
Ken Nakayama 《Vision research》1981,21(10):1475-1482
Sensitivity to horizontal shearing motion in random dots was measured as a function of common image motion amplitude. Without common image motion, thresholds for differential motion are comparable or better than vernier acuity. Above about 2 arc min of common image motion there is a proportionate increase in motion parallax thresholds such that for 20 arc min of common image motion, differential motion thresholds have risen by an order of magnitude. This differs from a comparable lack of threshold elevation for vernier acuity targets under similar conditions of movement (Westheimer and McKee, 1975). By varying movement duration, it can be shown that common image motion amplitude rather than common image velocity is the primary determinant of the effect. Furthermore this degradation of performance is not affected by changes in random dot size. Under favorable circumstances the phenomenon can also be seen with differentially moving vernier lines. The effect shows directional selectivity such that common motion directions closest to the horizontal leads to the greatest interference. The results add weight to the view that differential motion hyperacuity is mediated by a separate mechanism than differential position hyperacuity. 相似文献
88.
Studies were undertaken to examine cholesterogenesis in the intestine of streptozotocin-diabetic rats by measuring incorporation of [2(-14)C] acetate into cholesterol and 3-hydroxy-3-methylgultaryl CoA reductase (HMG-CoA reductase, EC 1.1.1.34) activity. In these diabetic rats, the intestinal mucosal weight and food consumption were markedly high. The incorporation of [2(-14)C] acetate into cholesterol was significantly increased in all diabetic intestinal segments. However, the rates of production of fatty acids and carbon dioxide were not affected. Hepatic HMG-CoA reductase activities were markedly reduced during both the diurnal high and low periods in these diabetic rats, and there was no diurnal variation. In contrast, the specific activities of this enzyme in jejunal crypt cells during both the diurnal high and low periods were significantly higher in these diabetic rats without loss of diurnal variation. Total reductase activity per segment of intestine in jejunal and ileal mucose (villi + crypt cells) was increased in these diabetic rats. Control rats had higher total and specific activity of ileal mucosal (velli + crypt cells) reductase than of jejunal mucosal reducatse during the diurnal high period. The jejunal-ileal gradient in reductase activity and the incorporation of [2(-14)C] acetate into cholesterol did not change significantly with streptozotocin-diabetic rats. The results indicate that in streptozotocin-diabetic rats, hepatic cholesterogenesis decreases but intestinal synthesis increases. 相似文献
89.
90.
I Miyoshi S Hiraki I Kubonishi Y Matsuda H Kishimoto T Nakayama T Tanaka H Masuji I Kimura 《Cancer》1977,40(6):2999-3003
An Epstein-Barr virus (EBV)-negative lymphoma line (JBL) was established in vitro from pleural effusion of an EBV-seropositive 29-year-old Japanese female with Burkitt's lymphoma. JBL cells as well as her original lymphoma cells bore monoclonal surface IgM with lambda light chains. The JBL line grew in single cell suspension with a doubling time of 30 hours. Attempts were made to serially transplant JBL cells in antilymphocyte serum-treated newborn hamsters; intraperitoneal implantation of 1-3 X 10(7) cells gave rise to invasive tumors in all recipients with death after 10 to 14 days. The hamster-passage line, now in the 9th passage, has been converted to an ascitic form with progression to leukemia in some animals. A "starry sky" pattern closely resembling the human tumor material was preserved in every tumor through serial animal passage. 相似文献