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   1486篇
  免费   132篇
  国内免费   6篇
耳鼻咽喉   24篇
儿科学   15篇
妇产科学   37篇
基础医学   124篇
口腔科学   29篇
临床医学   94篇
内科学   358篇
皮肤病学   86篇
神经病学   130篇
特种医学   38篇
外科学   327篇
综合类   26篇
一般理论   1篇
预防医学   61篇
眼科学   58篇
药学   117篇
中国医学   9篇
肿瘤学   90篇
  2023年   11篇
  2022年   21篇
  2021年   31篇
  2020年   27篇
  2019年   41篇
  2018年   70篇
  2017年   38篇
  2016年   45篇
  2015年   45篇
  2014年   58篇
  2013年   70篇
  2012年   112篇
  2011年   113篇
  2010年   48篇
  2009年   41篇
  2008年   95篇
  2007年   95篇
  2006年   94篇
  2005年   93篇
  2004年   50篇
  2003年   85篇
  2002年   60篇
  2001年   35篇
  2000年   17篇
  1999年   17篇
  1998年   9篇
  1996年   5篇
  1993年   4篇
  1992年   22篇
  1991年   13篇
  1990年   9篇
  1989年   9篇
  1988年   9篇
  1987年   8篇
  1986年   7篇
  1985年   13篇
  1984年   10篇
  1983年   7篇
  1982年   8篇
  1981年   4篇
  1980年   4篇
  1979年   9篇
  1978年   4篇
  1977年   7篇
  1975年   6篇
  1972年   4篇
  1971年   6篇
  1970年   4篇
  1969年   4篇
  1968年   6篇
排序方式: 共有1624条查询结果,搜索用时 31 毫秒
101.
BACKGROUND: High-altitude-induced hypoxia results in various diseases, such as chronic mountain sickness and high altitude retinal edema, and may affect severity and incidence of some cardiovascular diseases. In order to evaluate the effects of moderately high altitude on diabetic nephropathy and retinopathy, a cross-sectional study was planned. MATERIAL METHOD: Long-term type II diabetic residents of sea level (n=75, 38 male, 37 female, mean age 51.9+/-10.5 in Trabzon and Zonguldak cities) and moderately high altitude (h = 1,727 m, n = 73, 28 male, 45 female, mean age 48.3+/-12.1, Van city) were compared. RESULTS: No difference was observed in terms of age, gender, diabetes duration, body mass index, smoking, systolic, diastolic, and mean arterial blood pressure values, serum glucose levels, cholesterol, high-density lipoprotein (HDL)-cholesterol, low-density lipoprotein (LDL)-cholesterol, hemoglobin, HbA1C, hypertension control, or blood pressure medications and retinopathy incidence. Mean 24 h protein excretion (210.0+/-139.9, 127.8+/-112.1 mg; P=0.00), proteinuria prevalence (57.5% versus 33.3%, p=0.003), and serum creatinine levels (1.04+/-0.22 versus 0.84+/-0.21, p = 0.00) were significantly higher in the highlanders, glomerular filtration rate (GFR) was significantly lower in sea level (SL) patients (90.9+/-26.5 versus 83+/-21.1, p=0.05). CONCLUSION: Tendency to diabetic nephropathy as indicated by higher proteinuria and creatinine levels is increased among type 2 diabetic patients living at moderately high altitude. Prospective studies are needed to confirm these findings.  相似文献   
102.
103.
A 62-years old female presented with postmenopausal vaginal bleeding for one month. On vaginal examination soft fungated mass was palpated in cervix that bled to touch. Ultrasound, CT scan and MRI showed well-defined mass in cervix. On biopsy it was proved to be a primary non-Hodgkin's lymphoma.  相似文献   
104.
Twelve prognostic features of melanoma were examined in a series of 185 patients with nodal metastases (Stage II), who underwent surgical treatment at our institution during the past 20 years. Forty-four per cent of the patients presented with synchronous nodal metastases (substage IIA), 44% of the patients had delayed nodal metastases (substage IIB), and 12% of the patients had nodal metastases from an unknown primary site (substage IIC). The patients with IIB (delayed) metastases had a better overall survival rate than patients with IIA (synchronous) metastases, when calculated from the time of diagnosis. These differences could be explained on the basis of tumor burden at the time of initial diagnosis (microscopic for IIB patients versus macroscopic for IIA patients). Once nodal metastases became evident in IIB patients, their survival rates were the same as for substage IIA patients, when calculated from the onset of nodal metastases. The survival rates for both subgroups was 28% at five years and 15% for ten years. Substage IIC patients (unknown 1° site) had better five-year survival rates (39%), but the sample size was small and the differences were not statistically significant. A multifactorial analysis was used to identify the dominant prognostic variables from among 12 clinical and pathologic parameters. Only two factors were found to independently influence survival rates: 1) the number of metastatic nodes (p = 0.005), and the presence or absence of ulceration (p = 0.0019). Additional factors considered that had either indirect or no influence on survival rates (p > 0.10) were: anatomic location, age, sex, remission duration, substage of disease, tumor thickness, level of invasion, pigmentation, and lymphocyte infiltration. All combinations of nodal metastases were analyzed from survival differences. The combination that showed the greatest differences was one versus two to four versus more than four nodes. Their five-year survival rates were 58%, 27% and 10%, respectively (p < 0.001). Ulceration of the primary cutaneous melanoma was associated with a <15% five-year survival rate, while nonulcerative melanomas had a 30% five-year survival rate (p < 0.001). The combination of ulceration and multiple metastatic nodes had a profound adverse effect on survival rates. While tumor thickness was the most important factor in predicting the risk of nodal metastases in Stage I patients (p < 10-8), it had no predictive value on the patient's clinical course once nodal metastases had occurred (p = 0.507). The number of metastatic nodes and the presence of ulceration are important factors to account for when comparing surgical results, and when analyzing the efficacy of adjunctive systemic treatments.  相似文献   
105.
A multifactorial analysis of 200 cutaneous melanoma patients with distant metastasis (stage III) was performed on 13 clinical and pathological factors using the Cox regression analysis. There were only three dominant prognostic variables that independently predicted the patient's clinical course: (1) number of metastatic sites (1 vs. 2 vs. greater than or equal to 3, p less than 0.00001), (2) remission duration (less than 12 mo vs. greater than or equal to 12 mo, p = 0.0186), and (3) the location of the metastases (visceral vs. nonvisceral vs. combined, p = 0.0192). Factors that were not significant in the multifactorial analysis included the patients' age and sex, the site of the primary melanoma, the sequence of metastases, and all histopathological features of the primary melanoma (thickness, level of invasion, ulceration, growth pattern, pigmentation, and lymphocyte infiltration). For a single metastatic site, the 1-yr survival rate was 36%, while it was only 13% for 2 sites, and 0% for greater than or equal to 3 sites (p less than 0.00001). The 1-yr survival for patients was 40% for nonvisceral sites (skin, subcutaneous, distant lymph nodes) compared to only 11% for visceral metastases and 8% for combined sites (p less than 0.00001). Pulmonary metastases were associated with a significantly higher survival rate than metastatic melanoma in any other visceral site. The most common first site of distant metastases (either alone or in combination) was skin (38%), lung (36%), liver (20%), and brain (20%). The skin, subcutaneous and distant lymph node group was the first site of metastases in 59% of patients. This finding emphasizes the importance of careful physical exams in routine metastatic evaluations. Only a minority (25%) of stage I patients progressed to stage III disease after a median interval of 2.8 years. In contrast, the majority (75%) of melanoma patients with nodal metastases (stage II) progressed to stage III disease after a median duration of only 11 mo. Of the patients who eventually developed stage III disease, 95% of those who initially presented with stage II disease progressed within 3 yr, while stage I patients who progressed to stage III did not reach a 95% cumulative incidence until 8 yr.  相似文献   
106.
Deng W  Han Q  Liao L  Li C  Ge W  Zhao Z  You S  Deng H  Murad F  Zhao RC 《Tissue engineering》2005,11(1-2):110-119
Stem cell plasticity has created great interest because of its potential therapeutic application in degenerative or inherited diseases. Transplantation of bone marrow-derived stem cells was shown to give rise to cells of muscle, liver, nerve, endothelium, epithelium, and so on. But there are still disputes about stem cell plasticity, especially concerning the contribution of bone marrow-derived cells to skin cells. In this study, CM-DiI fluorescence-labeled Flk-(1+) bone marrow mesenchymal stem cells (bMSCs) of BALB/c mice (H-2Kd, white) were transplanted into lethally irradiated C57BL/6 mice (H-2Kb, black). By fluorescence tracing, we found that donor cells could migrate and take residency at the skin, which was confirmed by Y chromosome-specific PCR and Southern blot. The recipient mice grew white hairs about 40 days later and white hairs could spread over the body. Immunochemistry staining and RT-PCR demonstrated that skin tissue within the white hair regions was largely composed of donor-derived H-2Kd cells, including stem cells and committed cells. Furthermore, most skin cells cultured from white hair skin originated from the donor. Thus, our findings provide direct evidence that bone marrow-derived cells can give rise to functional skin cells and regenerate skin tissue. These may have important scientific implications in stem cell biology and transplantation therapy for skin tissue injury.  相似文献   
107.
High serum leptin levels in depressive disorders with atypical features   总被引:2,自引:0,他引:2  
Leptin is thought to be related to vegetative symptoms of depression such as alterations in food intake and weight. Fifty-seven drug-free patients and 26 healthy controls were enrolled in this study. We have found that the serum leptin levels were higher in patients with atypical depressive disorder than in controls, but not in patients with non-atypical depressive disorder, however, body mass index, age, and gender were not significantly different between these groups. Probably, these findings seem to be associated with some features of the atypical depressive disorders such as weight gain, a result of hyperphagia.  相似文献   
108.
OBJECTIVE: To determine whether the incidence and location of childhood CNS tumors in Syria follows the same pattern described in Western and Far Eastern countries. PATIENTS AND METHODS: We analyzed the data compiled from 367 children with brain tumors operated on in our Department of Neurosurgery between 1993 and mid-2002. We excluded all vascular and metastatic lesions and adopted the latest WHO classification in grouping all glial tumors. RESULTS: We found that 47% of brain tumors were located in the supratentorial, and 53% in the infratentorial region. The ratio of male to female occurrence was 1:1.2 (52% males, 48% females). For lesions in the supratentorial space, the distribution was 56% males and 44% females, while in the posterior fossa, the distribution was 61% males and 39% females. Low-grade tumors (WHO I/II) constituted 53.5% of all lesions, and the rest were high grade tumors (WHO III/IV) 46.5%.The most common tumor found in our childhood population was medulloblastoma (27.5%), followed by astrocytoma (25.8%), then craniopharyngioma (14.1%). The most common tumor in the posterior fossa was medulloblastoma (53.5%), followed by astrocytoma (22.5%), then ependymoma (17%). The most common tumors in the supratentorial space were astrocytoma and craniopharyngioma. CONCLUSIONS: In our patient population, the incidence and distribution of CNS tumors were somehow different than those reported by authors from the Western and Far Eastern countries. Whether these results are unique to Syria, or reflect a regional difference in the disease distribution between the Middle East region and the rest of the world, remains to be determined.  相似文献   
109.
Gastrointestinal nematode infection is known to alter host T cell activation and has been used to study immune and inflammatory reactions in which nitric oxide (NO) is a versatile player. We previously demonstrated that Trichinella spiralis infection inhibits host inducible NO synthase (NOS-2) expression. We now demonstrate that (i) an IL-4 receptor alpha-subunit (IL-4Ralpha)/Stat6-dependent but T cell-independent pathway is the key for the nematode-induced host NOS-2 inhibition; (ii) endogenous IL-4 and IL-13, the only known IL-4Ralpha ligands, are not required for activating the pathway; and (iii) treatment of RAW264.7 cells with parasite-cultured medium inhibits NOS-2 expression but not cyclooxygenase 2 expression. We propose that a yet-unidentified substance is released by the nematode during the host-parasite interaction.  相似文献   
110.
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