首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   7423篇
  免费   317篇
  国内免费   41篇
耳鼻咽喉   89篇
儿科学   120篇
妇产科学   70篇
基础医学   911篇
口腔科学   146篇
临床医学   602篇
内科学   1533篇
皮肤病学   117篇
神经病学   458篇
特种医学   401篇
外国民族医学   1篇
外科学   1343篇
综合类   39篇
一般理论   1篇
预防医学   162篇
眼科学   272篇
药学   575篇
  1篇
中国医学   20篇
肿瘤学   920篇
  2024年   28篇
  2023年   42篇
  2022年   77篇
  2021年   146篇
  2020年   111篇
  2019年   126篇
  2018年   153篇
  2017年   116篇
  2016年   140篇
  2015年   147篇
  2014年   205篇
  2013年   225篇
  2012年   334篇
  2011年   370篇
  2010年   203篇
  2009年   203篇
  2008年   366篇
  2007年   338篇
  2006年   357篇
  2005年   304篇
  2004年   358篇
  2003年   340篇
  2002年   326篇
  2001年   260篇
  2000年   245篇
  1999年   215篇
  1998年   95篇
  1997年   72篇
  1996年   74篇
  1995年   62篇
  1994年   64篇
  1993年   53篇
  1992年   148篇
  1991年   134篇
  1990年   132篇
  1989年   144篇
  1988年   123篇
  1987年   94篇
  1986年   89篇
  1985年   117篇
  1984年   81篇
  1983年   62篇
  1982年   31篇
  1981年   28篇
  1980年   38篇
  1979年   53篇
  1978年   40篇
  1971年   30篇
  1970年   34篇
  1969年   33篇
排序方式: 共有7781条查询结果,搜索用时 15 毫秒
91.
Acute epiglottitis causes sudden upper airway obstruction that may become lethal, and must be diagnosed and treated quickly and precisely. We review clinical features of 71-cases of acute epiglottitis in 6 years, focusing in cases requiring emergency airway management. Retrospective analysis was done for 1) age and gender, 2) month of onset, 3) symptoms, 4) smoking history, 5) diabetes history, 6) cause and background, 7) first medical institution visit, 8) duration from symptom onset to hospital visit, 9) oropharyngeal findings, 10) laryngendoscopic findings, 11) pharyngeal culture, and 12) deterioration after hospitalization. We found that 2 cases deteriorated in laryngendoscopic findings after hospitalization despite treatment. Even if the first medical findings are mild, it is necessary to respond to patients with the possibility to deterioration in mind. Five cases required emergency airway management-3 with tracheostomy and 2 cases with endotracheal intubation. If symptoms of laryngeal edema, oxygen desaturation, and dyspnea are present, emergency airway management should be prepared soon after hospitalization.  相似文献   
92.
Evidence for endocytosis-independent infection by human rotavirus   总被引:6,自引:0,他引:6  
Summary The effects of five lysosomotropic drugs (NH4Cl, chloroquine, methylamine, amantadine and dansylcadaverine) and cytochalasin B on human rotavirus (HRV KUN strain) and vesicular stomatitis virus (VSV Indiana strain) infection in monkey MA 104 cells were examined. These drugs had little effect on HRV yield but greatly reduced VSV yield. The results strongly suggest that HRV does not require endocytotic activity and intracellular acidic vesicles for the initial stage of infection and support our postulate that HRV enters the target cell by direct penetration of its nucleoid through the cell membrane.  相似文献   
93.
An unusual human rotavirus (HRV) isolate, designated AU-1, has a "long" RNA electrophoretic pattern and subgroup I specificity, in contrast to properties common to HRVs previously isolated. Hemagglutination activity of the AU-1 strain was demonstrated using erythrocytes of 1-day-old chicken. Neutralization assays revealed that the AU-1 strain was crossneutralized by hyperimmune antisera against the MO strain (serotype 3). However, antiserum directed against a reassortant in which the gene for Vp7 was replaced by the corresponding AU-1 gene neutralized the AU-1 strain to a significantly higher titer than the MO strain.  相似文献   
94.
Retinoblastomas exhibit a unique form of differentiation to produce cell elements similar to those seen in a photoreceptor cell. An ultrastructural study was performed on 29 cases of retinoblastoma to further clarify the cytologic characteristics of the tumor cells. The age of the retinoblastomas averaged 17.1 months and the tumor cells showing photo-receptor differentiation were demonstrated in 10 cases (35%). The findings were especially notable in retinoblastomas with Flexner-Wintersteiner rosette formation (seven cases, 28%). Similar photoreceptor differentiation was also evident in solid cell clusters without rosette formation (four cases, 14%). The presence of photoreceptor elements was assumed to be significantly frequent both in Flexner-Wintersteiner rosettes and in the solid cell clusters. The cell cytoplasm also showed proliferation of long mitochondria and microtubules, reflecting photoreceptor differentiation. The hereditary-type retinoblastoma showed more advanced cell differentiation than the non-hereditary type. Photoreceptor differentiated retinoblastoma showed rather indolent growth compared with the undifferentiated type, and the former can expect a curative treatment by operation. These observations provide additional findings of the biological nature of retinoblastomas.  相似文献   
95.

Purpose

To evaluate the oocyte fertilization ability and embryo growth after cyclophosphamide (CPA) treatment in mice.

Methods

Mice were treated with CPA at different doses (0‐800 mg/kg body weight). The oocytes then were retrieved and evaluated for their in vitro fertilization efficiency.

Results

The average number of metaphase II (MII) oocytes significantly decreased by ≥400 mg/kg CPA administration. The fertilization rate also decreased in the group that was treated with ≥400 mg/kg CPA. However, after fertilization, the embryos demonstrated normal growth ability. Two weeks after CPA administration, the number of mice from which the oocytes could be retrieved markedly decreased, but the fertilization rate and development of morphological features in the embryos were similar to those of the controls. One month after CPA administration, the number of mice from which the oocytes could be retrieved, fertilization rate, and development of the morphological features in the embryos were similar to those of the controls.

Conclusion

The number of oocytes decreased as the CPA administration level increased; however, the oocytes' potential for fertilization and development to the blastocyst stage was not significantly affected. One month after CPA administration, the number of oocytes and the potential for development into blastocysts were recovered.  相似文献   
96.
This study investigated the expression of the growth factors HGF and IGF-1 during the process of muscle regeneration in mdx mice. HGF and IGF-1 are reportedly expressed during the regeneration of muscle tissue in vitro. However, few studies have focused on the role of HGF and IGF-1 during muscle regeneration in mdx mice, which lack expression of the dystrophin gene. In the present study, we examined the expression of HGF and IGF-1 in masseter muscle during muscle regeneration in mdx and B10 (control) mice using histological analysis, immunohistochemistry and Western blotting, as well as examining gene expression by RT-PCR, at 3, 4 and 9 weeks. Mdx mice showed localized HGF and IGF-1 positivity in the cytoplasm of regenerating muscle cells at 3 and 4 weeks, but hardly any reactivity was evident at 9 weeks. The control group was completely negative for IGF-1 at any of the examined time points. Western blotting showed stronger expression of HGF and IGF-1 in mdx mice than in B10 mice at 3 and 4 weeks, but at 9 weeks the expression was absent in both groups. Similar results were obtained using RT-PCR. These present results suggest that HGF and IGF-1 appear to play an important role during regeneration of the masseter muscle in mdx mice.  相似文献   
97.
Stressful exercise results in temporary immune depression. However, the impact of exercise on the immune responses via toll-like receptor (TLR) 7, which recognizes the common viral genomic feature, single-stranded RNA, remains unclear. To clarify the effect of stressful exercise on immune function in response to viral infection, we measured the changes in the plasma concentration of tumor necrosis factor (TNF)-α and interferon (IFN)-α, which are induced downstream from the TLR–ligand interaction, in exhaustive-exercised mice immediately after treatment with the imidazoquinoline R-848, which can bind to and activate TLR7. Both exhaustive-exercised (EX) and non-exercised (N-EX) male C3H/HeN mice were injected with R-848 (5 mg kg?1), and blood samples were collected. In addition, RAW264 cells, which are mouse macrophage cells, were cultured 30 min after epinephrine (10 μM) or norepinephrine (10 μM) treatments, and were then stimulated with R-848 (10 μg ml?1). In addition, the effect of propranolol (10 mg kg?1) as blockade of β-adrenergic receptors on R-848-induced TNF-α and IFN-α production in the exercised mice was examined. Both the TNF-α and IFN-α concentrations in the plasma of EX were significantly lower than those in the plasma of N-EX after R-848 injection (P < 0.05 and P < 0.01, respectively), although the R-848 treatment increased the plasma TNF-α and IFN-α concentrations in both groups (P < 0.01, respectively). The R-848-induced TNF-α production in RAW264 cells was significantly inhibited by epinephrine and norepinephrine pre-treatment, although IFN-α was not detected. The propranolol treatment completely inhibited exercise-induced TNF-α and IFN-α suppression in response to R-848 in the mice. These data suggest that EX induces a reduction in TNF-α and IFN-α production in response to R-848, and that these phenomena might be regulated by an exercise-induced elevation of the systemic catecholamines.  相似文献   
98.

Purpose

To describe a successful pregnancy outcome following intracytoplasmic sperm injection (ICSI) with assisted oocyte activation (AOA) in a case of partial globozoospermia.

Methods

AOA was accomplished with calcium ionophore A23187. Sperm morphology was observed via light, fluorescent and electron microscopy following a Diff-Quik stain and fluorescein isothiocyanate-labeled peanut agglutinin (FITC-PNA) staining. An activation ability test was employed using a mouse oocyte exposed to strontium chloride.

Results

Via light microscopy, it was found that a large number of sperm possessed deficient acrosomes and a sharply rounded head; however, we observed both normal and the aforementioned abnormal sperm via FITC-PNA staining of a semen specimen. Mouse oocyte activation was 87.5?% via natural activation without AOA. With AOA after ICSI, 100?% oocyte activation was observed. Five oocytes were retrieved, and AOA with A23187 after ICSI resulted in a high fertilization rate (4 of 5, 80?%). Two embryos developed and the patient subsequently delivered a healthy female infant without any congenital abnormalities.

Conclusions

We report a successful pregnancy outcome using an early stage embryo, which developed following ICSI using sperm from a partially globozoospermic patient who possessed temporary potential oocyte activation.  相似文献   
99.
100.
To investigate the role of microfilaments in natural killer (NK) cell-mediated cytotoxicity, general microfilament inhibitors, cytochalasins B,D and dihydrocytochalasin B, and a selective inhibitor of myosin light chain kinase (MLCK) which regulates microfilament contraction, i.e. 1-(5-chloronaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine hydrochloride (ML-9) were examined in an NK assay system. ML-9 inhibited NK cell activity in a dose-dependent manner without affecting target cell binding, whereas cytochalasins suppressed the binding. The dextran suspension method revealed that ML-9 inhibits the programming for the lysis stage of the lytic process. In the single cell assay, the addition of ML-9 after target cell binding had occurred inhibited the lysis of bound target cells, whereas the addition of cytochalasins in a similar manner did not affect it. Thus, these results suggest the possibility that microfilament contraction is involved in the lytic mechanism of NK cell-mediated cytolysis. However, the mechanism whereby cytochalasins inhibit target cell binding remains unclear.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号