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   15860篇
  免费   963篇
  国内免费   91篇
耳鼻咽喉   109篇
儿科学   398篇
妇产科学   205篇
基础医学   2524篇
口腔科学   315篇
临床医学   1332篇
内科学   3371篇
皮肤病学   468篇
神经病学   1660篇
特种医学   687篇
外科学   2275篇
综合类   72篇
一般理论   7篇
预防医学   804篇
眼科学   489篇
药学   1115篇
中国医学   17篇
肿瘤学   1066篇
  2023年   78篇
  2022年   117篇
  2021年   262篇
  2020年   177篇
  2019年   220篇
  2018年   278篇
  2017年   253篇
  2016年   341篇
  2015年   346篇
  2014年   498篇
  2013年   592篇
  2012年   933篇
  2011年   961篇
  2010年   666篇
  2009年   628篇
  2008年   1056篇
  2007年   1110篇
  2006年   1091篇
  2005年   1116篇
  2004年   1002篇
  2003年   939篇
  2002年   915篇
  2001年   277篇
  2000年   190篇
  1999年   228篇
  1998年   250篇
  1997年   183篇
  1996年   167篇
  1995年   153篇
  1994年   108篇
  1993年   129篇
  1992年   91篇
  1991年   88篇
  1990年   94篇
  1989年   92篇
  1988年   113篇
  1987年   92篇
  1986年   75篇
  1985年   66篇
  1984年   57篇
  1983年   59篇
  1982年   70篇
  1981年   41篇
  1980年   48篇
  1979年   39篇
  1978年   43篇
  1977年   47篇
  1976年   42篇
  1974年   39篇
  1973年   36篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
991.
The physiological dynamics of intramyocellular lipids (IMCLs) in different muscle types and of hepatocellular lipids (HepCLs) are still uncertain. The dynamics of IMCLs in the soleus, tibialis anterior, and extensor digitorum longus (EDL) muscles and HepCL during fed, 12- to 72-h starved, and refed conditions were measured in vivo by (1)H-magnetic resonance spectroscopy (MRS) in Wistar rats. Despite significant elevations of free fatty acids (FFAs) during starvation, HepCLs and IMCLs in soleus remained constant. In tibialis anterior and EDL, however, IMCLs increased significantly by 170 and 450% after 72 h of starvation, respectively. After refeeding, elevated IMCLs dropped immediately in both muscles. Total muscle long-chain acyl-CoAs (LCACoAs) remained constant during the study period. Hepatic palmitoleoyl-CoA (C16:1) decreased significantly during starvation while total hepatic LCACoAs increased significantly. Consistent with constant values for FFAs, HepCLs, IMCLs, and muscle LCACoAs from 12-72 h of starvation, insulin sensitivity did not change. We conclude that during starvation-induced adipocytic lipolysis, oxidative muscles dispose elevated FFAs by oxidation, while nonoxidative ones neutralize FFAs by reesterification. Both mechanisms might prevent impairment of insulin signaling by maintaining low levels of LCACoAs. Hepatic palmitoleoyl-CoA might have a special role in lipid metabolism due to its unique dynamic profile during starvation.  相似文献   
992.
993.
The development of visual hallucinations after loss of vision is known as the Charles Bonnet syndrome. This phenomenon was first described in 1760 by Charles Bonnet and others during their observations of elderly patients with degeneration of the retina or cornea. To date a clear association between visual hallucinations and neurosurgical procedures has not been reported. Because of their clear demarcation, however, surgical lesions in the cerebrum offer a unique opportunity to determine the pathoanatomical aspects of visual hallucinations. During a 3-year period, 41 consecutive patients who acquired visual field defects after neurosurgery were examined for the occurrence of visual hallucination. Postoperatively, four of these patients experienced visual hallucinations. In two of them an upper quadrantanopia developed after the patients had undergone selective amygdalohippocampectomy. In the other two patients a complete hemianopia developed, in one case after resection of a parietal astrocytoma and in the other after resection of an occipital glioblastoma multiforme. The visual hallucinations were transient and gradually disappeared between 4 days and 6 months postoperatively. The patients were aware of the fact that their hallucinations were fictitious and displayed no psychosis. Electroencephalographic recordings were obtained in only two patients and epileptic discharges were found. Deafferentiation of cortical association areas may lead to the spontaneous generation of complex visual phenomena. In the present series this phenomenon occurred in approximately 10% of patients with postoperative visual field defects. In all four cases the central optic radiation was damaged between the lateral geniculate nucleus and the primary visual cortex. The complex nature of the visual hallucination indicates that they were generated in visual association areas.  相似文献   
994.
BACKGROUND: Mechanical manipulation, pressure, and temperature increase can induce bone necrosis during intramedullary reaming. METHODS: In this study, the bone debris obtained after reaming 18 sheep tibiae was analyzed to investigate its vitality by measuring alkaline phosphatase activity. Two different reamer designs were used for the project. Bone cells were first cultivated in a specific growth medium, counted 3 weeks after the reaming procedure, and then cultivated for another 5 weeks. RESULTS: At the end of the project, qualitative evaluation showed positive alkaline phosphatase activity in most of the cases, and quantitative evaluation also showed enzyme activity. The positive alkaline phosphatase results were independent of the reamer sizes and reamer design. No significant results were obtained from a comparison of different reamer sizes and designs. This indicates that osteoblasts survive after correctly performed reaming. CONCLUSION: The results prove the vitality of the bone debris and confirm clinical observations.  相似文献   
995.
AIM: We performed a retrospective analysis of patients with soft tissue defects following total knee arthroplasty and therapy. Furthermore, we described the possibilities of covering soft tissue defects following knee arthroplasty. METHOD: In 5 patients, soft tissue defects following knee arthroplasty were covered with medial M. gastrocneminus flaps. Localisation and size of the defect, microbiology, risk factors, and interval between arthroplasty and the occurrence of the soft tissue defect were retrospectively analysed. RESULTS: On average, defects occurred 9 weeks after prosthesis implantation. In all cases, the soft tissue defect developed in the area of the incision. In 3 cases, wound infection was diagnosed. Four patients exhibited factors associated with wound-healing failure. No prosthesis was lost. CONCLUSION: The gastrocneminus muscle flap provides good quality coverage with small donor site defect, permits early mobilisation, and allows for fast rehabilitation. The risk of flap loss is minimal. Early and adequate defect coverage can reduce both prosthesis loss and amputation rates.  相似文献   
996.
BACKGROUND: Studies have shown that racial and socioeconomic differences lead to inequality in access to health care. It is unknown whether insurance status and race affect the choice of surgical treatment for patients presenting with appendicitis. STUDY DESIGN: Patients with primary ICD-9 procedure codes for laparoscopic and open appendectomy were selected from the 1998, 1999, and 2000 Nationwide (US) Inpatient Samples. The primary predictor variables were insurance status (private, Medicare, Medicaid, other) and race (Caucasian, African American, Hispanic, other). Multiple logistic regression models were used to assess whether insurance status and race are associated with the choice of surgical procedure for patients presenting with appendicitis. RESULTS: Discharge abstracts of 145,546 patients were used for our analyses. There were 32,407 patients (22.3%) who underwent laparoscopic appendectomy and 113,139 patients (77.7%) who had open appendectomy. Although 24.2% of privately insured patients underwent laparoscopic appendectomy, only 16.9% of Medicare patients, 17.4% of Medicaid patients, and 19.6% of patients in the "other" insurance category were treated using the laparoscopic procedure (p < 0.001). Caucasian patients underwent laparoscopic surgery in 24.8%, African Americans in 18.6%, Hispanics in 19.6%, and other ethnicities in 18.8% of patients (p < 0.001). Compared with the Medicaid subset, and after adjusting for potential confounders such as age, gender, race, patient comorbidity, median ZIP code income, hospital location and teaching status, and presence of abscess or perforation, privately insured patients (odds ratio [OR] = 1.26, 95% [CI [1.20, 1.33], p < 0.001) and Medicare patients (OR = 1.17, 95% CI [1.05, 1.30], p = 0.004) were significantly more likely to undergo laparoscopic surgery. Caucasian patients (OR = 1.42, 95% CI [1.33, 1.51], p < 0.001) and Hispanics (OR = 1.12, 95% CI [1.04, 1.20], p = 0.002) were significantly more likely to have laparoscopic appendectomy, compared with African Americans, even after adjusting for the previously mentioned confounders and insurance status. CONCLUSIONS: Even after adjusting for potential confounders, insurance status and race are marked independent predictors of having laparoscopic surgery in patients treated for appendicitis in this sample.  相似文献   
997.
998.
Bioglass particles of the compositions 45s5, 52s, and 55s were implanted in the distal femoral epiphysis of rabbits. Animals were sacrificed at 7, 28, and 84 days postoperatively and specimens investigated using electron microscopy and electron dispersive X-ray analysis. The intention was to correlate the finding of different types of multinuclear giant cells (MNGC) in the center of the implantation bed with earlier hypothesized accumulated particle eluates and changed particle compositions. The distribution of Si, Na, Ca, P, O, S, and Cl throughout the implantation bed was analyzed. Bioglass particles degraded either in Si-rich remnants or in CaP-shells. MNGC of foreign body giant cell type in high numbers as well as of osteoclast-like type at later time intervals in small numbers were found on the surface of Si-rich as well as on Ca- and P-rich particle remnants. Osteoclast-like cells were detected on the particles after transformation in CaP-shells. It is concluded that the formation of different types of MNGC is determined by the composition of the substrate, that is, osteoclast-like cells develop exclusively on resorbable substrates. The absolute number of MNGC depended on the time after implantation and the solubility of the implant. Bone bonding, however, only occurred on Ca- and P-rich surfaces.  相似文献   
999.
BACKGROUND: Immune-mediated adverse reactions to drugs are often due to T-cell reactivity, and cross-reactivity is an important problem in pharmacotherapy. OBJECTIVE: We investigated whether chemical inert drugs can stimulate T cells through their T-cell receptor (TCR) and analyzed the cross-reactivities to related compounds. METHODS: We transfected human TCRs isolated from two drug-reactive T-cell clones (TCCs) by PCR into a TCR-negative mouse T-cell hybridoma. The TCCs were isolated from a patient with drug hypersensitivity to the antibacterial sulfonamide sulfamethoxazole (SMX). RESULTS: The transfectants reacted to SMX only in the presence of antigen-presenting cells (APCs). Glutaraldehyde-fixed APCs, however, were sufficient to elicit T-cell stimulation, indicating a processing-independent direct interaction of the drug with the TCR and MHC molecule. The transfected hybridomas secreted IL-2 in a drug dose-dependent manner, whereas the degree of reactivity was dependent on the level of TCR expression. One transfectant reacted not only to SMX but also to related sulfonamide compounds. Interestingly, high TCR expression increased cross-reactivity to other structurally related compounds. In addition, SMX-specific TCR cross-reacted only with sulfonamides bearing a sulfanilamide core structure but not with sulfonamides such as celecoxib, furosemide, or glibenclamide. CONCLUSIONS: These results demonstrate that the T-cell reactivity to drugs is solely determined by the TCR. Moreover, these results show that cross-reactivity of structurally similar compounds correlates with the density of the TCR. Stably transfected T-cell hybridomas may represent a powerful screening tool for cross-reactivity of newly generated sulfonamide-containing compounds such as celecoxib.  相似文献   
1000.
Using a group-specific PCR assay, we investigated the presence of enterohepatic Helicobacter species in gut specimens from patients with inflammatory bowel disease. Enterohepatic Helicobacter species were detected in 12% (3 of 25) of the patients with Crohn's disease, in 17% (3 of 18) of the ulcerative colitis samples, and in 4% (1 of 23) of the controls.  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