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   701篇
  免费   26篇
  国内免费   2篇
耳鼻咽喉   6篇
儿科学   14篇
妇产科学   7篇
基础医学   64篇
口腔科学   29篇
临床医学   54篇
内科学   122篇
皮肤病学   27篇
神经病学   66篇
特种医学   47篇
外科学   83篇
综合类   8篇
一般理论   1篇
预防医学   33篇
眼科学   11篇
药学   75篇
中国医学   6篇
肿瘤学   76篇
  2023年   2篇
  2022年   10篇
  2021年   22篇
  2020年   15篇
  2019年   12篇
  2018年   29篇
  2017年   14篇
  2016年   12篇
  2015年   18篇
  2014年   33篇
  2013年   32篇
  2012年   81篇
  2011年   56篇
  2010年   33篇
  2009年   39篇
  2008年   32篇
  2007年   41篇
  2006年   31篇
  2005年   24篇
  2004年   30篇
  2003年   20篇
  2002年   10篇
  2001年   11篇
  2000年   15篇
  1999年   7篇
  1998年   4篇
  1997年   4篇
  1996年   5篇
  1995年   2篇
  1994年   3篇
  1993年   3篇
  1992年   6篇
  1991年   3篇
  1990年   7篇
  1989年   7篇
  1988年   11篇
  1987年   5篇
  1986年   3篇
  1985年   3篇
  1984年   8篇
  1983年   13篇
  1982年   5篇
  1981年   3篇
  1980年   2篇
  1979年   1篇
  1969年   1篇
  1968年   1篇
排序方式: 共有729条查询结果,搜索用时 15 毫秒
1.
Both ultrashort echo-time STEAM and MEGA-PRESS-edited spectroscopy were used to validate noninvasive quantification of vitamin C (ascorbate) in the developing rat brain, where changes in ascorbate concentration have been reported. Despite strong overlap with resonances from glutamine, glutamate, glutathione, and macromolecules, reliable quantification of ascorbate (Cramer-Rao lower bounds<0.2 micromol/g) by LCModel analysis of STEAM (TE=2 ms) spectra was possible at 9.4 T. Ascorbate concentrations quantified from the STEAM spectra were in very good agreement with concentrations calculated from fully resolved ascorbate resonances in MEGA-PRESS-edited spectra measured from identical volumes of interest. Ascorbate concentrations measured using STEAM decreased with increasing postnatal rat age, in agreement with published brain ascorbate concentrations measured in vitro using high-performance liquid chromatography (HPLC).  相似文献   
2.
Acute myelogenous leukemia (AMU is a hematologic disorder that is characterized by an abnormal proliferation of immature myeloid cells. Granulocytic sarcomas are clusters of leukemic myeloid cells that may develop as a result of AML. Oral manifestations of AML are common and often involve enlargements of the gingiva and/or mucosal tissue from direct leukemia cell infiltration. We describe the case history of a 50-year-old man who had an ulcera-tive lesion of the oral mucosa that was determined to be a granulocytic sarcoma of AML-M0 subtype. The combination of both the subtype and clinical presentation of the leukemia makes this presentation unusual, and to the best of our knowledge, of a type that has not been previously reported in the literature.  相似文献   
3.
Entomological and epidemiological surveys in May, August and November 1985 and March 1986 were conducted in villages in Bulandshahr, a western district in Uttar Pradesh and in three eastern districts, Jaunpur, Ballia and Saran. In Bulandshahr, Anopheles culicifacies sibling species A and B were found, with a predominance of species A. Both Plasmodium vivax and P. falciparum were present and the malaria incidence remained high (SPR, 6-50%) indicating an active transmission. In contrast, in three eastern districts predominance of species B with an occasional occurrence of species A was observed. Malaria cases were almost absent in Ballia and Saran and in Jaunpur 10.3% slide positivity rate was observed in May but in later surveys cases were considerably lower (SPR, 0.5-2.9%) indicating the absence of indigenous transmission. In the eastern districts, malaria parasites are regularly brought in from endemic areas by the migrant labor population. Although An. culicifacies s.l. occurs in both the areas, the difference in malaria incidence appears to be due to the difference in the composition of the sibling species which is, the predominant presence of species A in the western district and its absence in eastern districts. This indicates that species A is responsible for active malaria transmission while species B is not.  相似文献   
4.
New chemotherapy drugs and, more recently, targeted therapies have significantly improved the outcome of patients with resected stage III colon cancer (adjuvant chemotherapy) and patients with unresectable metastases (palliative therapy). These advances raise several questions about the place of chemotherapy after and before surgery in patients with resectable liver metastases. To date, only a combined intra-arterial plus systemic fluoropyrimidine-based chemotherapy regimen has clearly demonstrated a relapse-free survival benefit. Yet, this approach is restricted to specialized centers, mainly because of technical difficulties and locoregional toxicities. The role of systemic use of oxaliplatin- and irinotecan-based regimens is currently under investigation. Planned trials will assess the role of anti-angiogenic and anti-epidermal growth factor receptor agents. We review the main trials performed in patients with resectable metastases, and discuss their potent impact on clinical practice.  相似文献   
5.
Midline cysts in the male pelvis are a confusing entity due to their relatively infrequent presentation and the uncertainty as to their origin and classification. We report on CT appearance of four cases of midline prostatic cysts. Ultrasound correlation was available in one case. Two patients presented with lower urinary tract symptoms (hematospermia and/or hematuria), and two were asymptomatic, with one case detected on physical examination and one found incidentally on CT. Computed tomography demonstrated a characteristic sharply marginated, low density, homogeneous midline cyst within the prostate. On ultrasound a well defined midline anechoic cystic mass was seen. These cases are illustrated and a discussion of cystic masses in the male pelvis is included.  相似文献   
6.
BackgroundLiver transplantation is a complex surgical procedure. The experience of the anesthesiologist, and its potential relationship to patient morbidity and mortality, is yet to be determined. We sought to explore this possible association using our institutional training patterns as the subject of study.MethodsThis is a single center retrospective analysis investigating the association of an anesthesiologist's experience with liver transplantation and its potential effect on early patient outcomes in adult liver transplant recipients from January 2010 to September 2016. Training of team members consisted of a 6-month period of clinical shadowing with a senior anesthesiologist and co-staffing 8 liver transplant procedures before solo staffing a liver transplant. Specifically, patient outcomes for the first 5 transplants after this training were investigated.ResultsThe only independent risk factor for early death or early graft loss was the amount of packed red blood cells administered during transplantation. With respect to secondary outcomes, the amount of packed red blood cells and hospitalization at the time of transplant were associated with the number of days on a ventilator, length of intensive care unit stay, and overall hospital length of stay.ConclusionsThe results of this study conclude that the training model currently in place for our new team members has no negative impact on patient outcomes after liver transplantation.  相似文献   
7.
Administration of caffeine (1,3,7-trimethylxanthine), a major component of coffee, to Swiss mice at doses of 80 or 100 mg/kg body weight 60 min prior to whole-body lethal dose of gamma-irradiation (7.5 Gy) resulted in the survival of 70 and 63% of animals, respectively, at the above doses in contrast to absolutely no survivors (LD-100/25 days) in the group exposed to radiation alone. Pre-treatment with a lower concentration of caffeine (50 mg/kg) did not confer any radioprotection. The protection exerted by caffeine (80 mg/kg), however, was reduced from 70 to 50% if administered 30 min prior to irradiation. The trend statistics reveal that a dose of 80 mg/kg administered 60 min before whole-body exposure to 7.5 Gy is optimal for maximal radioprotection. However, caffeine (80 mg/kg) administered within 3 min after irradiation offered no protection. While there is documentation in the literature that caffeine is an antioxidant and radioprotector against the oxic pathway of radiation damage in a wide range of cells and organisms, this is the first report demonstrating unequivocally its potent radioprotective action in terms of survival of lethally whole-body irradiated mice.  相似文献   
8.
PURPOSE: Legumain, a novel asparaginyl endopeptidase, has been observed to be highly expressed in several types of tumors including colorectal cancer. However, there is no study examining the relationship of legumain expression to clinocopathologic and biological variables in colorectal cancers. EXPERIMENTAL DESIGN: We investigated legumain expression in 164 primary colorectal cancers, 34 corresponding distant normal mucosa samples, 89 adjacent normal mucosa samples, and 33 lymph node metastases using immunohistochemistry. We also did Western blotting analysis on three additional colorectal cancers and three colonic cell lines. RESULTS: Legumain expression was increased in primary tumors compared with distant or adjacent normal mucosa (P < 0.05), but there was no significant change between primary tumors and metastases (P > 0.05). Legumain expression was positively related to poorer differentiation/mucinous carcinoma (P = 0.04), higher degree of necrosis (P = 0.03) and apoptosis (P < 0.0001), positive proliferating cell nuclear antigen (P < 0.0001) and p53 expression (P = 0.049), and had a positive tendency towards stromelysin 3 (P = 0.058) and PINCH positivity (P = 0.05). The patients with tumors that showed both weak and lower percentage of the legumain expression, either in tumor (P = 0.01) or in stroma (P = 0.04), had a better prognosis. CONCLUSIONS: The legumain expression may be involved in colorectal cancer development and have a prognostic value in the patients.  相似文献   
9.
Peripheral arterial disease (PAD) is an important cause of morbidity and mortality in the world affecting up to 20% in people over 70?years of age. The prevalence is increasing in India due to combined effects of increased life expectancy, increased tobacco smoking and increased prevalence of diabetes mellitus. The aim of the study was to examine the hypothesis whether squatting posture reduces blood flow to lower limbs resulting in worsening of symptoms of lower limb ischemia in patients with PAD. 10 patients with arterial disorders due to thromboangiitis obliterans (TAO), atherosclerosis and diabetic macro vascular disease were selected for patients and were compared with 10 healthy volunteers as controls. Clinical examination and duplex scan of posterior tibial artery (PTA) and dorsalis pedis artery (DPA) performed in standing and squatting position in a clinical environment. They were asked about symptoms of numbness, ischemic pain and the results were noted. Results were tabulated and analysed using Microsoft Excel?. Members in the control group complained of numbness of both the limbs after a period of 30?min on an average. In the patients group, members while squatting complained of numbness in the involved limb within 5?min. They complained of ischemic pain in the involved limb within 10?min and developed numbness in the opposite limb in within 15?min. Posterior tibial artery and dorsalis pedis artery pulsations disappeared for the entire duration of squatting in both groups as confirmed by duplex scanning. It may be recommended that patients with established peripheral vascular disease should avoid squatting position, even if it is for a very short period of time. It is desirable to advice such patients to use appropriate structures as supports which will allow them to work without squatting. This may also necessitate a change in occupation.  相似文献   
10.
Hyperglycemia (blood glucose concentration >150 mg/dL) is common in extremely low gestational age newborns (ELGANs; birth at <28 week gestation). Hyperglycemia increases the risk of brain injury in the neonatal period. The long‐term effects are not well understood. In adult rats, hyperglycemia alters hippocampal energy metabolism. The effects of hyperglycemia on the developing hippocampus were studied in rat pups. In Experiment 1, recurrent hyperglycemia of graded severity (moderate hyperglycemia (moderate‐HG), mean blood glucose 214.6 ± 11.6 mg/dL; severe hyperglycemia (severe‐HG), 338.9 ± 21.7 mg/dL; control, 137.7 ± 2.6 mg/dL) was induced from postnatal day (P) 3 to P12. On P30, the hippocampal neurochemical profile was determined using in vivo 1H MR spectroscopy. Dendritic arborization in the hippocampal CA1 region was determined using microtubule‐associated protein (MAP)‐2 immunohistochemistry. In Experiment 2, continuous hyperglycemia (mean blood glucose 275.3 ± 25.8 mg/dL; control, 142.3 ± 2.6 mg/dL) was induced from P2 to P6 by injecting streptozotocin (STZ) on P2. The mRNA expression of glycogen synthase 1 (Gys1), lactate dehydrogenase (Ldh), glucose transporters 1 (Glut1) and 3 (Glut3) and monocarboxylate transporters 1 (Mct1), 2 (Mct2) and 4 (Mct4) in the hippocampus was determined on P6. In Experiment 1, MRS demonstrated lower lactate concentration and glutamate/glutamine (Glu/Gln) ratio in the severe‐HG group, compared with the control group (p < 0.05). Phosphocreatine/creatine ratio was higher in both hyperglycemia groups (p < 0.05). MAP‐2 histochemistry demonstrated longer apical segment length, indicating abnormal synaptic efficacy in both hyperglycemia groups (p < 0.05). Experiment 2 showed lower Glut1, Gys1 and Mct4 expression and higher Mct1 expression in the hyperglycemia group, relative to the control group (p < 0.05). These results suggest that hyperglycemia alters substrate transport, lactate homeostasis, dendritogenesis and Glu‐Gln cycling in the developing hippocampus. Abnormal neurochemical profile and dendritic structure due to hyperglycemia may partially explain the long‐term hippocampus‐mediated cognitive deficits in human ELGANs.  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