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   7241篇
  免费   437篇
  国内免费   11篇
耳鼻咽喉   63篇
儿科学   382篇
妇产科学   154篇
基础医学   843篇
口腔科学   104篇
临床医学   509篇
内科学   1559篇
皮肤病学   121篇
神经病学   387篇
特种医学   264篇
外科学   1414篇
综合类   163篇
一般理论   3篇
预防医学   356篇
眼科学   222篇
药学   633篇
中国医学   11篇
肿瘤学   501篇
  2023年   57篇
  2022年   83篇
  2021年   231篇
  2020年   124篇
  2019年   208篇
  2018年   249篇
  2017年   165篇
  2016年   182篇
  2015年   186篇
  2014年   306篇
  2013年   290篇
  2012年   490篇
  2011年   510篇
  2010年   250篇
  2009年   218篇
  2008年   385篇
  2007年   309篇
  2006年   328篇
  2005年   301篇
  2004年   300篇
  2003年   259篇
  2002年   233篇
  2001年   164篇
  2000年   164篇
  1999年   170篇
  1998年   49篇
  1997年   52篇
  1996年   47篇
  1995年   38篇
  1994年   32篇
  1993年   37篇
  1992年   107篇
  1991年   117篇
  1990年   88篇
  1989年   96篇
  1988年   82篇
  1987年   77篇
  1986年   72篇
  1985年   89篇
  1984年   52篇
  1983年   51篇
  1979年   27篇
  1977年   25篇
  1975年   28篇
  1974年   36篇
  1973年   42篇
  1972年   29篇
  1969年   26篇
  1968年   27篇
  1967年   22篇
排序方式: 共有7689条查询结果,搜索用时 31 毫秒
81.
The surgical management of bilateral synchronous nephroblastoma remains controversial. The authors describe three cases treated using ex vivo tumor dissection followed by autotransplantation in an attempt to preserve functioning renal tissue. Two children are alive and tumor free with adequate renal function at 30 months and 3 years, respectively. One died from tumor recurrence with metastases 9 months after surgery. This technique is an acceptable alternative to bilateral nephrectomy followed by transplantation.  相似文献   
82.
BACKGROUND: Patients with major fracture/soft-tissue injuries are at risk for adult respiratory distress syndrome after secondary infection. Fracture fluids (FF) are rich in neutrophil (PMN) -specific chemokines such as interleukin-8. PMN respond to both interleukin-8 and bacterial stimuli with calcium ([Ca2+]i) fluxes, which can initiate respiratory burst (RB). We hypothesize that small amounts of FF entering the circulation could exaggerate PMN [Ca2+]i and RB responses, potentially increasing the risk of adult respiratory distress syndrome. METHODS: FF were obtained from 10 patients at open fixation of the femur 2 to 5 days postinjury. Volunteer PMN were isolated and loaded with fura dye. PMN were preincubated either in 30% autologous plasma (AP)/70% buffer, or in 5% FF/25% AP/70% buffer. Cells were resuspended in buffer with 1,2,3-dihydrorhodamine and stimulated with low-dose n-formyl-methionyl-leucyl-phenylalanine (fMLP). [Ca2+]i was assayed by fura fluorescence at 505 nm after excitation at 340/380 nm. RB was assessed by 1,2,3-dihydrorhodamine fluorescence at 530 nm after 488 nm excitation. RESULTS: PMN basal [Ca2+]i was higher after FF incubation than AP incubation (94+/-12 vs. 61+/-9 nmol/L, p = 0.0002). Peak [Ca2+]i response to fMLP was 475+/-47 nmol/L after FF but only 356+/-22 nmol/L after AP (p = 0.01). Two hundred seconds after fMLP, [Ca2+]i remained higher after FF (172+/-17 vs. 145+/-9 nmol/L, p = 0.04). Basal RB was slightly higher after FF than AP (13.4+/-0.3 vs. 11.3+/-0.3 units, p = 0.051) as was the maximal rate of extracellular oxidant release (1.10+/-0.17 vs. 0.76+/-0.16 units/s, p = 0.004) and total oxidant production (42.5+/-0.8 vs. 31.7+/-0.8 units, p = 0.006). CONCLUSION: Small amounts of FF in plasma can exaggerate PMN [Ca2+]i flux and RB responses to subsequent bacterial stimuli. These findings are consistent with the hypothesis that release of FF into the circulation primes PMN and, thus, may predispose to adult respiratory distress syndrome. Such PMN priming events might have important implications for both the operative and medical management of patients with major fractures.  相似文献   
83.
84.
AIMS/METHODS: A national data collection exercise was carried out in more than 100 hospital eye service units within the UK to provide clinical and administrative information on patients undergoing cataract surgery. This included patient clinical data such as visual acuity at the time of wait listing and at the time of admission for surgery, presence of other eye disorders, other serious medical disorders, and data on waiting time and type of admission. RESULTS: The profiles of the 18 454 patients aged 50 years or older are reported. Findings of particular note were as follows. At the time of wait listing for cataract surgery 31% had visual acuity of 6/12 or better, 54% had visual acuity between 6/18 and 6/60, and 15% had less than 6/60 vision. Considering those who had visual acuity of 6/12 or better at the time of wait listing, by the time of admission for surgery, the vision deteriorated to 6/18-6/60 in 33% and in a further 3% the vision deteriorated to below 6/60. In patients with moderately poor visual acuity (<6/12-6/60) at the time of wait listing, 13% had less than 6/60 vision by the time of admission for surgery. CONCLUSION: This type of data collection and reporting exercise provides new material that can be used in the planning and provision of cataract surgery services in the UK.  相似文献   
85.
Capillaria hepatica parasitism   总被引:1,自引:0,他引:1  
Capillaria hepatica is rarely encountered in humans, with fewer than 30 documented cases. The clinico-pathological features of capillaria hepatica infection, diagnosed on liver biopsy of a 6-year-old child are discussed. Pathologically, it is characterised by prominent granulomatous lesions in the liver surrounding the eggs, which on cursory examination may be confused withSchistosoma mansoni.  相似文献   
86.
The direct effect of intratracheal (IT) administration of human major basic protein (MBP) on pulmonary inspiratory pressure (PIP), and the effect on agonist-induced change in PIP, were determined in anesthetized, ventilated guinea pigs. 500 g MBP increased PIP from 24.1±4.3 to 49.8±7.4 cm H2O (p<>n=10). Maximum PIP was achieved within 30 min after 500 g MBP. The direct PIP response to 250 g MBP was not different from vehicle. The PIP responses to intravenous (IV) acetylcholine (Ach) and 5-hydroxytryptamine (5-HT) were measured before and after administration of 250 g MBP (n=12). MBP caused a modest, but significant potentiation of the increase in PIP induced by 1, 3 and 10 g/kg Ach (24, 32 and 28%, respectively,p<0.02) and=" to=" 1=">g/kg 5-HT (43%p<0.02). we=" conclude=" that=" mbp=" at=" a=" dose=" that=" does=" not=" directly=" affect=" inspiratory=" pressure=" is=" capable=" of=" augmenting=" the=" pip=" response=" to=" iv=" ach=" and=">in vivo.  相似文献   
87.
Seizures and civilian head injuries   总被引:4,自引:3,他引:1  
Although several studies have reported on the risk of "early seizures" (seizures occurring within 7 days following a head injury), the reported proportions of patients experiencing these seizures vary from 1.4 to 15%. This wide divergence may be due to problems with methodology such as case selection and definitions of head injury and early seizures. In a series of 702 patients admitted with a head injury to Cook County Hospital (CCH), Chicago, Illinois, 29 (4.1%) had early seizures. This proportion is twice as high as one previously reported in a comparable series. This may reflect an actual difference between the two series or a case selection bias serving to elevate the proportion of patients with early seizures at CCH.  相似文献   
88.
Microencapsulated permethrin (penncapthrin) was evaluated under laboratory conditions for its toxicity toward several nontarget aquatic invertebrates. Average LC50 estimates for selected lotic invertebrates, based on a one hour dosing regime, were: 2.71 mg/L forSimulium vittatum, 4.59 mg/L forHydropsyche spp., and 13.41 mg/L forIsonychia bicolor. In acute static tests withDaphnia magna, there was no significant difference (p0.05) between the toxicity of penncapthrin at 96 h (LC50 range: 6.80–22.5 g/L) and the EC formulation at 72 h (LC50 range: 0.6–21 g/L). Comparatively, the toxicity of microencapsulated methyl parathion (penncap-m) was not significantly different from that of penncapthrin towardD. magna, the former having LC50 estimates ranging form 0.3–12.25 g/L. LC50 estimates associated withDaphnia pulex ranged from 19 to 131 g/L. The toxicity of penncapthrin and penncap-m towardD. pulex was difficult to determine because of frequent control mortality due to food deprivation resulting from the need to run tests for longer than 48 h. In successful tests, LC50 estimates ranged from 19 to 28 g/L for penncapthrin and 0.08 to 25 g/L for penncap-m after 72 h exposure. In long term toxicity tests, 95% of D. magna at 1 g/L, 44% at 10 g/L, and 20% at 15 g/L survived after 39 days exposure. Less than 15% ofD. pulex survived over the same concentration range following 32 days exposure. Despite some drawbacks, long-term toxicity tests were more appropriate than short-term tests for evaluating microencapsulated sticides because of reduced variability in LC50 estimates and lower control mortality.  相似文献   
89.
AIM: A number of imaging techniques have been used for the pre-operative assessment of patients for lung volume reduction surgery (LVRS). We evaluated whether data currently acquired from perfusion scintigrams and cine MR of the diaphragm are obtainable from high resolution CT (HRCT) of the thorax. MATERIALS AND METHODS: Thirty patients taking part in a randomized controlled trial of LVRS against maximal medical therapy were evaluated. HRCT examinations (n= 30) were scored for (i) the extent and distribution of emphysema; (ii) the extent of normal pulmonary vasculature; and (iii) diaphragmatic contour, apparent defects and herniation. On scintigraphy, (n= 28), perfusion of the lower thirds of both lungs, as a proportion of total lung perfusion (LZ/T(PERF)), was expressed as a percentage of predicted values (derived from 10 normal control subjects). On cine MR (n= 25) hemidiaphragmatic excursion and coordination were recorded. RESULTS: Extensive emphysema was present on HRCT (60% +/- 13.2%). There was strong correlation between the extent of normal pulmonary vasculature on HRCT and on perfusion scanning (r(s)= 0.85, P< 0.00005). Hemidiaphragmatic incoordination on MR was weakly associated with hemidiaphragmatic eventration on HRCT (P= 0.04). CONCLUSION: The strong correlation between lung perfusion assessed by HRCT and lung perfusion on scintigraphy suggests that perfusion scintigraphy is superfluous in the pre-operative evaluation of patients with emphysema for LVRS.  相似文献   
90.
We reviewed the pattern of involvement of the calvarium by tuberculosis (TB) in five patients and the role of imaging in its management. Four patients presented with localised scalp swelling and one with generalized seizures. Radiographs revealed lucent lesions with minimal surrounding sclerosis in the frontal (2), parietal (2) and occipital (1) bones. CT showed lesions involving the entire thickness of the calvarium and accompanying contrast-enhancing soft tissue. The patient presenting with seizures had a ring-enhancing lesion in the parietal lobe in addition to the extra-axial lesions. Although radiographs in all cases demonstrated calvarial TB, CT showed the extent of the defect, involvement of adjacent soft tissues, and in one case an intra-axial lesion. Radiographs suffice for follow-up of these patients. Received: 23 July 1999 Accepted: 20 September 1999  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