全文获取类型
收费全文 | 2458篇 |
免费 | 98篇 |
国内免费 | 16篇 |
专业分类
耳鼻咽喉 | 9篇 |
儿科学 | 24篇 |
妇产科学 | 22篇 |
基础医学 | 292篇 |
口腔科学 | 62篇 |
临床医学 | 209篇 |
内科学 | 639篇 |
皮肤病学 | 66篇 |
神经病学 | 176篇 |
特种医学 | 31篇 |
外科学 | 522篇 |
综合类 | 9篇 |
预防医学 | 92篇 |
眼科学 | 17篇 |
药学 | 156篇 |
肿瘤学 | 246篇 |
出版年
2022年 | 20篇 |
2021年 | 29篇 |
2020年 | 23篇 |
2019年 | 35篇 |
2018年 | 25篇 |
2017年 | 22篇 |
2016年 | 37篇 |
2015年 | 32篇 |
2014年 | 34篇 |
2013年 | 53篇 |
2012年 | 87篇 |
2011年 | 106篇 |
2010年 | 49篇 |
2009年 | 52篇 |
2008年 | 85篇 |
2007年 | 90篇 |
2006年 | 80篇 |
2005年 | 101篇 |
2004年 | 92篇 |
2003年 | 84篇 |
2002年 | 90篇 |
2001年 | 98篇 |
2000年 | 101篇 |
1999年 | 92篇 |
1998年 | 42篇 |
1997年 | 15篇 |
1996年 | 24篇 |
1995年 | 33篇 |
1994年 | 20篇 |
1993年 | 21篇 |
1992年 | 87篇 |
1991年 | 57篇 |
1990年 | 80篇 |
1989年 | 77篇 |
1988年 | 78篇 |
1987年 | 72篇 |
1986年 | 75篇 |
1985年 | 52篇 |
1984年 | 44篇 |
1983年 | 28篇 |
1980年 | 13篇 |
1979年 | 29篇 |
1978年 | 19篇 |
1976年 | 13篇 |
1975年 | 13篇 |
1974年 | 15篇 |
1970年 | 15篇 |
1968年 | 16篇 |
1967年 | 16篇 |
1965年 | 12篇 |
排序方式: 共有2572条查询结果,搜索用时 15 毫秒
41.
Brain temperature modifies glutamate neurotoxicity in vivo 总被引:5,自引:0,他引:5
The purpose of this study was to examine the effects of mild hypothermia and hyperthermia on glutamate excitotoxicity. Glutamate-induced cortical lesions were produced in hypothermic (32 degrees C), normothermic (37 degrees C), and hyperthermic (40 degrees C) rats by perfusion of a 0.5 M glutamate solution via a microdialysis probe. The volume of the lesion 7 days after glutamate perfusion was quantified histologically by image analysis. This histological assessment was performed in two experiments; in one, each of the target temperatures was induced before glutamate perfusion, and in the other, each of the target temperatures was induced after stopping the glutamate perfusion. We also examined the effect of temperature on the diffusion of exogenously delivered material in the extracellular space using autoradiography of the perfused glutamate solution containing 14C-labeled sucrose. In the two experiments in which each of the target temperatures was induced before or after glutamate perfusion, the volume of damage was reduced by mild hypothermia and enlarged by mild hyperthermia. The volume of 14C diffusion also increased as brain temperature increased. These results provide evidence that small variations of brain temperature modify glutamate excitotoxicity. The results also suggest that the change in glutamate diffusion in the extracellular space is one mechanism by which mild hypothermia and hyperthermia exert their protective and harmful effects respectively. 相似文献
42.
We report five cases of multiple sclerosis (MS) and three cases of allied demyelinative diseases starting during childhood. Three of the MS patients presented with atypical initial symptoms, such as acute encephalitis or myelitis, making an early clinical diagnosis difficult. Ophthalmologic symptoms were noted in four of MS children, and in two with allied demyelinative diseases. Therefore, if a child shows ophthalmologic symptoms (i.e. optic neuritis, ophthalmoplegia), brain magnetic resonance imaging (MRI) should be conducted for the differential diagnosis of MS and other demyelinative diseases. Cerebrospinal fluid analysis is not useful for the initial diagnosis of MS, because pleocytosis and increase of oligoclonal IgG band in cerebrospinal fluid are seen in both MS and other demyelinative disorders. However, neuron specific enolase (NSE) is slightly higher in the latter than in the former. T2-weighted MRI of multiple sclerosis showed multiple high intensity areas in the white matter of the cerebrum and cerebellum, capsula interna, and crus cerebri etc. Most of these lesions were clinically silent, being characteristic of MS. In two MS cases, however, initial MRI revealed no abnormal findings. Thus, the diagnosis of MS can not be made by initial MRI only. 相似文献
43.
Yoshiyama T Mikawa K Maekawa N Tanaka O Goto R Yaku H Obara H 《Journal of anesthesia》1991,5(3):313-316
Key words complications - intubation - epiglottic cyst 相似文献
44.
A Takeshita K Shinjo K Naito H Matsui K Shigeno S Nakamura T Horii M Maekawa K Kitamura T Naoe K Ohnishi R Ohno 《Leukemia》2003,17(3):648-650
45.
Maekawa M; Sugano K; Kashiwabara H; Ushiama M; Fujita S; Ohkura H; Kakizoe T 《Japanese journal of clinical oncology》1998,28(6):383-387
BACKGROUND: Ornithine decarboxylase (ODC; EC 4.1.1.17) is the first
rate-limiting enzyme in the biosynthesis of polyamines. ODC protein has a
characteristic amino acid sequence, the PEST sequence, which is related to
the enzyme's rapid degradation. ODC cDNA prepared from human hepatoma
tissues has been reported to show nonsense or missense mutations. METHODS:
We examined somatic mutations of ODC cDNA by RT-PCR-SSCP analysis and mRNA
expressions by RT-PCR in 50 colorectal cancer tissues to investigate the
involvement of ODC gene alterations in colorectal cancers. RESULTS:
Increased expression of the ODC gene was observed in 36 cases (86%) out of
the 42 examined by RT-PCR. In one case, a missense mutation was found in
the cancer tissue but not in normal mucosa. The missense mutation from Asp
to Asn at codon 424, in the PEST region, possibly stabilizes the ODC
protein. In colorectal cancer, replication error and a germline mutation in
hMSH2 gene were observed. CONCLUSIONS: The missense mutation at codon 424
is speculated to be a cause of stabilization and a passenger mutation owing
to the mutator phenotype. Since only one of 50 colorectal cancers exhibited
a missense mutation of the ODC gene, mutations in ODC gene are not frequent
in colorectal cancer. The increased expression of the ODC gene was noted in
86% of colorectal cancer tissues by RT-PCR, however, it was not due to
point mutations in ODC coding exons.
相似文献
46.
Postinfarction ventricular septal rupture is still a surgically challenging situation with high operative mortality. We report a case of ventricular septal rupture in a 75-year-old woman successfully treated with our newly devised technique, in which a pliable large septal path is fixed with transmural sutures placed in posterior left ventricular free wall and anterior ventriculotomy closing sutures, thus covering the septal wall almost entirely. Our method may simplify the operation and reduce the risk of residual leakage. 相似文献
47.
Midori Yoshida Shin-Ichi Katsuda Dai Nakae Akihiko Maekawa 《Food and chemical toxicology》2004,42(4):667-676
A chronic combined toxicity and carcinogenicity study of S-170, a sucrose fatty acid ester, was performed in male and female F344 rats. S-170 was given ad libitum in the diet at levels of 0, 1.25, 2.5 or 5% to 10 rats/sex/group for 12 months to determine chronic toxicity and 0, 2.5 or 5% to 50 rats/sex/group for two years in the carcinogenicity study. Treatment with S-170 exerted no effect on survival in either sex. In the 12-month chronic toxicity study, no treatment-related effects on body weights, or hematological, blood biochemical, urinary and pathological parameters were demonstrated in any of the treated groups. In the carcinogenicity study, S-170 did not cause any dose-related significant increase in the incidences of tumors in any organs or tissues. Taken together, the results clearly demonstrate that S-170 has neither toxic nor carcinogenic activity in F344 rats under the conditions of the study. No observed adverse effect levels (NOAELs) calculated from the 12-month chronic toxicity and carcinogenicity study were 2.37 g/kg/day in males and 2.80 g/kg/day in females, and 2.12 g/kg/day in males and 2.42 g/kg/day in females, respectively. 相似文献
48.
BACKGROUND AND AIMS: Bacterial translocation is precipitated by an increase in bacteria or endotoxin, depression of the membrane barrier, and an increase in mucosal permeability. Plaunotol is a mucosal protective agent, and observed to have a strong suppressive effect on superoxide production. In this study, the effect of plaunotol on bacterial translocation was examined using the model of ischemia and reperfusion. METHOD: Male Sprague Dawley rats were used to create the following model for evaluation of bacterial translocation: (i) the control group; (ii) the preventive dose group (plaunotol 30 mg/kg/day one week before surgery); (iii) the therapeutic dose group (plaunotol 30 mg/kg/day one week after surgery); and (iv) the full dose group (plaunotol 30 mg/kg/day one week before surgery and one week after surgery). Bacterial translocation was assessed as the blood concentration of the endotoxin. RESULTS: In the control group, the endotoxin increased significantly 3 days postsurgery (13.7+/-5.6 pg/ml) compared with before surgery (1.1+/-0.1 pg/ml). In the preventive and full-dose groups, the erndotoxin decreased significantly 3 days postsurgery (4.4+/-2.8 pg/ml, 5.7+/-2.7 pg/ml, respectively) compared with that of the control group. CONCLUSION: Plaunotol in the preventive and full-dose groups decreased the endotoxin. This suggests that plaunotol is one of the protectors for bacterial translocation. 相似文献
49.
A 47-year-old Japanese woman with a history of epigastric pain and a recent episode of acute pancreatitis (back pain, nausea, and vomiting) and anemia was found to have a pancreatic cyst of the tail on CT-scan and ultrasonography. Especially, ultrasonography revealed the papillary solid lesion in the cyst. With the tentative diagnosis of a cystic neoplasm, distal pancreatectomy was performed. Histological examination of sections showed massive hemorrhage, surrounded fibrous connective tissue, and numerous macrophages with hemosiderin deposits; these histological findings resembled cystic endometriosis. The clinicopathological features and pathogenesis of the pancreatic endometrial cyst are discussed. 相似文献
50.
Kazuyuki Enomoto Shuichi Takahashi Yasunari Maekawa 《Macromolecular chemistry and physics.》2012,213(1):72-78
Most polymer grafts in grafted polymer films obtained by radiation‐induced solid graft polymerization are not analyzed in detail due to difficulties in isolation of the grafts without structural decomposition. Herein, a novel structural and molecular weight characterization method is reported for polymer grafts that are chemically attached to thermally and chemically stable polymer substrates, based on a swelling‐induced graft detachment in hot water. Polymer grafts prepared by the radiation‐induced polymerization of alkyl acrylate into poly(ethylene‐co‐tetrafluoroethylene) (ETFE) followed by a sulfonation reaction are found to have a ternary copolymer structure whose monomer units contain –COOH or –SO3H groups, or both. 相似文献