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   41779篇
  免费   3182篇
  国内免费   438篇
耳鼻咽喉   436篇
儿科学   1142篇
妇产科学   757篇
基础医学   6083篇
口腔科学   583篇
临床医学   3937篇
内科学   9205篇
皮肤病学   942篇
神经病学   3242篇
特种医学   1655篇
外国民族医学   18篇
外科学   5653篇
综合类   1293篇
现状与发展   1篇
一般理论   6篇
预防医学   3108篇
眼科学   745篇
药学   2998篇
  6篇
中国医学   633篇
肿瘤学   2956篇
  2023年   333篇
  2022年   783篇
  2021年   1411篇
  2020年   851篇
  2019年   1079篇
  2018年   1337篇
  2017年   924篇
  2016年   964篇
  2015年   1159篇
  2014年   1506篇
  2013年   1919篇
  2012年   2778篇
  2011年   2735篇
  2010年   1727篇
  2009年   1408篇
  2008年   2027篇
  2007年   2020篇
  2006年   1888篇
  2005年   1807篇
  2004年   1629篇
  2003年   1488篇
  2002年   1412篇
  2001年   1236篇
  2000年   1232篇
  1999年   1101篇
  1998年   386篇
  1997年   338篇
  1996年   289篇
  1995年   249篇
  1994年   231篇
  1993年   198篇
  1992年   585篇
  1991年   566篇
  1990年   561篇
  1989年   505篇
  1988年   498篇
  1987年   444篇
  1986年   425篇
  1985年   424篇
  1984年   297篇
  1983年   222篇
  1982年   138篇
  1981年   127篇
  1979年   238篇
  1978年   129篇
  1977年   143篇
  1976年   127篇
  1974年   157篇
  1972年   143篇
  1969年   124篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
We investigated the role of the nitric oxide (NO) synthase (NOS) pathway in muscular metabolism during endotoxemia in four groups of male Wistar rats. Two groups were injected with the lipopolysaccharide (LPS) of Escherichia coli (3 mg/kg), with one group treated using N(G)-nitro-L-arginine methylester ([L-NAME] 85 mg/kg/d) and the other not. The two control groups included one treated with L-NAME and the other not. After 24 hours of fasting, the rats were fed by controlled enteral nutrition and killed on day 3. The results showed that (1) NOS inhibition was detrimental during endotoxemia, increasing lethality from 20% to 80.5%, and (2) NOS inhibition did not modify the hypercatabolic state consecutive to endotoxemia, particularly at the muscular level (nitrogen balance, total-body and muscular weight loss, and muscular protein and glutamine concentrations). However, myofibrillar catabolism was delayed in the LPS-NAME group. In conclusion, NO production is of major importance for survival after an endotoxemic challenge, but contributes weakly to the metabolic response of muscle to injury.  相似文献   
992.
OBJECTIVE: The endonasal approach to the sella turcica is supposed to simplify surgical techniques and reduce the risk and sequelae linked to removal of pituitary adenomas. We report our experience with 105 procedures using this approach. Method: The series included 45 men and 60 women, aged 17 to 83 years. Their intrasellar lesions were: 43 non-functional adnomas, 37 prolactinomas, 7 GH- adenomas, 9 corticotrop adenomas, 9 miscellaneous lesions (abscess, Rathke cleft cysts, empty sella). Mean duration of the procedures was 50 minutes. Mean hospital stay was 4 days. RESULTS: There were no deaths. Morbidity included: 1 (0.95%) rhinorrhea associated with meningitis which cured without sequelae, 11 (10.5%) transient diabetes insipidus lasting no longer than 48 hours, 2 cases of permanent diabetes insipidus (1 non-functional macroadenoma, 1 pituitary abscess), 1 transient hyposmia (3 months), 2 transient nasal obstructions. There were no cases of septal perforation, nasal deformation, partial or complete mucosal anesthesia, nasal pain, dental pain, or epistaxis. CONCLUSION: This surgical approach is easier to perform and causes less rhinological sequelae than the sublabial transsphenoidal approach. It allows an as effective tumor removal than the latter. Hospitalization stay is significantly shortened.  相似文献   
993.
Ultrasound has been proposed as a low-cost, radiation-free method for osteoporosis assessment in postmenopausal women. Large prospective studies have shown that ultrasound parameters can be used for fracture risk estimate in this population, providing that adequate quality control is performed. The places of both ultrasound and the current gold standard method for bone assessment, dual energy x-ray absorptiometry, are still to be determined. Further studies are needed on the diagnosis of osteoporosis using ultrasound, because current diagnostic thresholds, designed by the World Health Organization, do not apply to this-new technology. Monitoring of skeletal changes and treatment effects by ultrasound cannot be recommended.  相似文献   
994.
995.
Cytokines and heart rate variability in patients with chronic heart failure   总被引:3,自引:0,他引:3  
INTRODUCTION: Heart rate variability (HRV) analysis is a non-invasive method of assessment of the autonomic nervous system's effects on heart function. In chronic heart failure (CHF), decreased HRV correlates with the progression of the disease. It is also known that in CHF increased levels of proinflammatory cytokines are present. Because these molecules are believed to influence the nervous system at both the central and peripheral levels, their potential role in HRV reduction in the course of CHF has been proposed. AIM: The study was designed to verify potential relations between cytokines and HRV parameters in CHF patients. The concept of the study was driven by the recognition of controversies in this field and the paucity of published reports. METHODS: Forty-four patients with CHF and stable NYHA class I-IV symptoms and 15 healthy controls were enrolled in the study. Time-domain HRV analysis was performed based on of 24-hour Holter ECG monitoring. Plasma concentrations of soluble TNFalpha receptors sTNF-RI and sTNF-RII and interleukin 6 (IL-6) were measured using commercially available ELISA kits (Quantikine, RD Systems). RESULTS: In patients with CHF, HRV indices included in the analysis were significantly decreased, and the levels of cytokines increased in comparison with the control group. In the whole study population, both in the CHF patients and the control group, significant negative correlations were observed between sTNF-RI level and long-term HRV indices such as SDNN (r=-0.44; p=0.0006), SDANN (r=-0.44; p=0.0005) and short-time index SDNNI (r=-0.37; p=0.004). Similar negative correlations were found between sTNF-RII level and SDNN (r=-0.35; p=0.007), SDANN (r=-0.34; p=0.01), and SDNNI (r=-0.31; p=0.02), as well as between IL-6 level and SDNN (r=-0.41; p=0.001), SDANN (r=-0.44; p=0.0005) and SDNNI (r=-0.34; p=0.009). CONCLUSIONS: Significant negative correlations between TNF-alpha soluble receptors sTNF-RI, sTNF-RII and IL-6 levels and time-domain HRV parameters were observed in the study. Because the results of investigations conducted so far do not elucidate the cause-effect relationship, further studies are needed to clarify the mechanisms of HRV depression in CHF and the role of cytokines in this severe clinical condition.  相似文献   
996.
997.
BACKGROUND/AIMS: To compare non-invasive biological liver fibrosis scores, as alternatives to liver biopsy, in HIV/HCV co-infected patients. METHODS: Two hundred and seventy-two HIV/HCV patients, nai ve for HCV treatment, underwent liver biopsy [197 (72%) men, 39.9 years, fibrosis stage (Metavir) F1 (25%), F2 (40%), F3 (25%), F4 (10%), median CD4 486/mm(3) and median HIV viral load 3.5log. Fibrotest (FT), Hepascore (HS), Fibrometer (FM), SHASTA, APRI, Forns index, and Fib-4 were tested in order to differentiate patients with mild to moderate fibrosis (F2) and those with advanced fibrosis (F3). The AUROC and the rate of well-classified patients were compared to liver biopsy. RESULTS: FT, HS, and FM were able to stage liver fibrosis in all patients with AUROCs of 0.78, 0.84 and 0.89 for the diagnosis of F2, respectively. The correlation coefficient indexes were 0.37, 0.46 and 0.48, respectively. The rates of well-classified patients were 62%, 68% and 71%, respectively. Fib-4, APRI and the Forn's index were only able to stage 37-61% of patients and showed lower accuracies. Using a combination of FT, HS and FM did not significantly increase the performance of each test. CONCLUSIONS: In HIV/HCV co-infected patients, Fibrometer, Hepascore and Fibrotest outperformed other non-invasive liver fibrosis biomarkers for the prediction of significant liver fibrosis.  相似文献   
998.
In freshwater or seawater female silver eel, the release of gonadotropin (GTH) accumulated in the pituitary under estradiol (E2) influence could be stimulated by a conjugated treatment with a mammalian gonadoliberin agonist (GnRH-A = des-Gly10, (D-Ala6)-LH-RH ethylamide) and a blocker of dopamine receptor (pimozide). Furthermore, despite the GTH release, no reduction or even a significant increase in pituitary GTH levels were noted, indicating a stimulation of GTH synthesis. In consequence of the endogenous GTH release, a stimulation of ovarian development was induced, as demonstrated by the gonadosomatic index and histological study. Similar results were obtained with a combined treatment with GnRH-A and an inhibitor of catecholamine synthesis (L-alpha-methyl-3,4-dihydroxyphenylalanine). In contrast, no effect was produced by GnRH-A, pimozide, or L-alpha-methyl-DOPA, given alone. The results suggest that a double neuroendocrine mechanism (a lack of GnRH production and a dopaminergic inhibition of GnRH action) is involved in the prepubertal blockage of eel gonadotropic function before the reproductive migration.  相似文献   
999.
We describe an immunocompetent 8-year-old boy with a serological profile indicating chronic infection by Epstein-Barr virus (EBV) who developed subcutaneous and pulmonary lesions related to a peripheral T-cell proliferation. No clonal rearrangement of T-cell receptor or immunoglobulin genes was seen. However, the finding of a t(3;17)(q21;q25) in 44 metaphases from one skin lesion demonstrated a clonal origin. We also showed that the proliferative T cells contained EBV genome leading to the diagnosis of EBV-associated peripheral T-cell lymphoma. Further cytogenetic and molecular studies are needed to identify genes implicated in the pathogenesis of this haematological malignancy.  相似文献   
1000.
The role played by T lymphocytes in myelopoiesis has been established in in vitro studies. Dysregulation of the lymphoid system results in quantitative and, more rarely, qualitative abnormalities of myelopoiesis. The authors report the clinical data of two cases of peripheral T cell lymphoma associated with an AREB type of dysmyelopoiesis. The fact that both conditions were diagnosed simultaneously and progressed in parallel is an indirect argument in favour of the regulation of myelopoiesis by the T lymphocytes.  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