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   25662篇
  免费   1278篇
  国内免费   117篇
耳鼻咽喉   131篇
儿科学   431篇
妇产科学   317篇
基础医学   3396篇
口腔科学   741篇
临床医学   1720篇
内科学   5980篇
皮肤病学   479篇
神经病学   2478篇
特种医学   1143篇
外科学   4423篇
综合类   104篇
现状与发展   1篇
预防医学   846篇
眼科学   609篇
药学   1973篇
中国医学   62篇
肿瘤学   2223篇
  2023年   137篇
  2022年   291篇
  2021年   535篇
  2020年   257篇
  2019年   379篇
  2018年   504篇
  2017年   397篇
  2016年   465篇
  2015年   474篇
  2014年   626篇
  2013年   794篇
  2012年   1268篇
  2011年   1459篇
  2010年   770篇
  2009年   638篇
  2008年   1177篇
  2007年   1345篇
  2006年   1352篇
  2005年   1315篇
  2004年   1250篇
  2003年   1198篇
  2002年   1195篇
  2001年   810篇
  2000年   822篇
  1999年   772篇
  1998年   303篇
  1997年   243篇
  1996年   217篇
  1995年   177篇
  1994年   163篇
  1993年   172篇
  1992年   546篇
  1991年   491篇
  1990年   458篇
  1989年   446篇
  1988年   433篇
  1987年   372篇
  1986年   364篇
  1985年   368篇
  1984年   212篇
  1983年   170篇
  1982年   99篇
  1981年   91篇
  1980年   88篇
  1979年   172篇
  1978年   128篇
  1977年   96篇
  1974年   129篇
  1973年   115篇
  1969年   102篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
Thrombotic microangiopathy (TMA) may develop after living donor liver transplantation (LDLT), but the mechanism is not fully understood. We retrospectively analyzed all patients undergoing LDLT at our center, including TMA patients, to elucidate the clinical characteristics and presentation and to determine which patients have a higher risk of occurrence of TMA. In all, 57 adult patients were reviewed after LDLT at our institution. TMA was diagnosed by sudden and severe thrombocytopenia, followed by hemolytic anemia with fractionated erythrocytes in the blood smear. Clinical features were compared between the TMA group and the non-TMA group. Of the 57 patients, 4 were diagnosed with posttransplantation TMA. ABO blood group (ABO)-incompatibility, cyclophosphamide (CPA), and recipient blood group (type O) were closely correlated with the occurrence of TMA. Thrombocytopenia appeared 1 to 5 days before hemolytic anemia. Coagulative function markers stayed at the same level after TMA, while marked elevation was shown in fibrinolytic function markers such as plasminogen activator inhibitor type 1 (PAI-1). TMA occurred at a higher prevalence in ABO-incompatible graft recipients. Additional factors associated with ABO-incompatible transplantation, such as an overdose of immunosuppressants, may affect the likelihood of TMA. Sudden and severe thrombocytopenia presented before hemolytic anemia and the serum levels of PAI-1 correlated well with the clinical course of TMA. In conclusion, early recognition of thrombocytopenia and elevation of PAI-1 is crucial to diagnose TMA especially in ABO-incompatible LDLT.  相似文献   
72.
Silent cerebral lesions are increasingly found in mass screenings using MRI and magnetic resonance angiography (MRA). The purpose of this paper is to assess the usefulness of two non-invasive clinical tests-carotid ultrasound examination and brachial-ankle pulse wave velocity (baPWV) measurement-for predicting silent cerebral infarction (SCI) and silent intracranial arterial stenosis. Data were collected on 480 asymptomatic adult subjects who participated in a brain screening program at a single hospital between April 2003 and March 2006. All participants underwent baPWV measurement, B-mode ultrasonography of carotid arteries, MRI, and MRA. Data on 476 (99.1%) subjects were included in the analysis. Among these, 273 (57.4%) were male and the mean age was 51.5 years; 161 (33.8%) had carotid plaque; 33 (6.9%) had increased intima-media thickness (IMT); 99 (20.8%) had SCI; and 7 (1.5%) had intracranial arterial stenosis. The multivariate analysis showed that age (odds ratio [OR]: 1.12; 95% confidence interval [CI]: 1.08-1.17), carotid plaque (OR: 2.69; 1.59-4.56), increased IMT (OR: 2.40; 1.02-5.65), and a history of hypertension treatment (OR 2.22; 1.11-4.43) were significantly associated with SCI. Also, increased IMT (OR 9.70: 1.48-63.71) was related to intracranial arterial stenosis. Brachial-ankle PWV was related to SCI (p<0.01) and intracranial stenosis (p=0.01) in univariate analysis but not in multivariate analysis. The presence of carotid plaque and that of increased IMT on ultrasound examination are useful for assessing the risk of SIC. Increased IMT is also predictive of intracranial arterial stenosis.  相似文献   
73.
From 1985 to 1987, we examined relationship between the lesion of tricuspid valve and right ventricular function in 31 patients (male: 9, female: 22) with mitral valve disease. The median age at operation was 52 years (range 37-69 years). Group I consisted of 17 patients (MS: 10, MSR: 5, MR: 2) accompanied with tricuspid regurgitation (TR) and Group II 14 patients (MS: 12, MSR: 2) without TR. In all cases of Group I tricuspid annuloplasty (TAP) were performed correctly. De Vega methods were done in 12 cases and Carpentier rings were used in 5 cases. Cardiac catheterization was done before and after operation. And right ventricular volume was measured by right ventricular angiography. In both groups pulmonary capillary wedge pressure, pulmonary artery pressure and cardiac index were improved postoperatively. Pulmonary artery resistance (PAR) and total pulmonary resistance (TPR) in Group I were significantly higher before operation but there were no difference between two groups postoperatively. Right ventricular end-diastolic volume index (RVEDVI) and right ventricular end-systolic volume index (RVESVI) in Group I were significantly improved postoperatively, but in Group II these were within normal range both pre- and postoperatively. Preoperative PAR was correlated inversely with postoperative right ventricular ejection fraction (RVEF). It means that patients with severe pulmonary vascular lesion had postoperative lower right ventricular function. In both groups, RVESVI was in inverse correlation with RVEF pre- and postoperatively. In both groups, there was an inverse correlation between the per cent change of RVESVI and that of RVEF. This means that RVESVI influenced right ventricular pump function.  相似文献   
74.
There have only been a few studies of chemo-endocrine therapy compared with endocrine therapy alone in newly diagnosed prostate cancer patients. We assessed the effects of these two therapies by comparing long-term survival rates. One hundred and twenty-nine patients were entered in this study between November 1977 and March 1992. Seventy-seven patients were treated with endocrine therapy alone. Other 52 patients received chemo-endocrine therapy, which included orchiectomy and/or diethylstilbestrol diphosphate (DES-DP) plus Cisplatin, with or without other cytotoxic agents. All patients had bone metastasis at the beginning of the study. There was a significant difference in survival between patients who received endocrine therapy and chemo-endocrine therapy (P = 0.0078). That is, survival rate was superior for the chemoendocrine therapy patients throughout the entire follow-up period. These data suggest that early chemo-endocrine therapy containing Cisplatin, with or without maintenance chemotherapy, is a potentially effective treatment for newly diagnosed metastatic prostate cancer and is worth further investigation via a randomized trial.  相似文献   
75.
Mycobacterium bovis BCG (BCG) is a live vaccine used worldwide against tuberculosis. However, it has unfavourable side effects such as osteitis or osteomyelitis, and these sometimes lead to vertebral caries in some patients as a result of bone resorption. Osteoblasts might play a role in the bone resorption caused by BCG infection, because they are central cells in bone metabolism. Cultured osteoblast-like cell lines (MC3T3-E1) derived from C57BL mice susceptible to BCG infection cells were infected with BCG at several doses. Interestingly, internalization of BCG-enveloped phagosome-like membrane in osteoblast-like cells were observed by transmission electron microscopy (TEM). Owing to infection, the proliferation and alkaline phosphatase activity of the osteoblast-like cells were reduced in a dose-dependent manner. On the other hand, interleukin (IL)-6 production was considerably enhanced by infection. These results suggest that BCG infects osteoblasts, suppressing their proliferation and differentiation and inducing bone resorption, which may be related to osteitis/osteomyelitis and bone caries caused by BCG infection.  相似文献   
76.
Physiological abnormalities in hereditary hyperekplexia.   总被引:3,自引:0,他引:3  
Five patients from a kindred with hereditary hyperekplexia had physiological testing. The surface-recorded electromyographic pattern of audiogenic muscle jerks was identical to that of the normal acoustic startle reflex. Testing at graded stimulus intensities indicated an increase in the gain of the acoustic startle reflex. Nose-tap stimuli resulted in short-latency generalized electromyographic bursts that were similar to the R1 component of the blink reflex. Electrical stimulation of peripheral nerves elicited a pattern of generalized muscle jerks that was similar to that of the acoustic startle reflex. Somatosensory evoked potentials, brainstem auditory evoked potentials, and cortical auditory evoked potentials were normal. The primary physiological abnormality in hereditary hyperekplexia is widespread elevated gain of vestigial withdrawal reflexes in the brainstem and possibly the spinal cord, most likely resulting from increased excitability of reticular neurons.  相似文献   
77.
The responses of the ganglioglomerular nerve (GGN) to transient changes and steady-state levels of paO2 at a constant paCO2 were studied in 12 anesthetized and spontaneously breathing cats before and after bilateral section of aortic (AN) and carotid sinus nerves (CSN). In two of these cats carotid chemoreceptor activity was monitored simultaneously. Onset of moderate hypoxia, down to paO2 of about 50 Torr, stimulated GGN activity and withdrawal of the hypoxic stimulus promptly eliminated the responses both before and after CSN section. CSN section, however, significantly raised the baseline activity and slightly delayed the GGN response to the onset of hypoxia. These responses to hypoxia are qualitatively similar to the characteristic responses of peripheral chemoreceptors. Thus, the basic oxygen chemosensing mechanism appeared to be present in the sympathetic nervous system, and is expressed in the postganglionic GGN activity. This property allows the sympathetic nervous system to perform physiologically important functions independent of the peripheral chemoreceptors.  相似文献   
78.
79.
P E Pepe  K L Mattox  R P Fischer  C M Matsumoto 《The Journal of trauma》1990,30(9):1125-31; discussion 1131-2
The purpose of this study was to investigate the distribution of various mechanisms of injury and the relative severity of such injury cases throughout the different geographic zones of a large urban area using a computerized emergency medical services (EMS) dispatch/patient record database. The study city (population, 2 million residents) was divided into 156 geographic grids (each 4.5 by 3 miles) and the incidence and relative severity of various injury mechanisms were determined for each zone. Results: In one year (1988), there were more than 115,000 separate EMS incidents involving more than 150,000 patients, 26,000 of whom were transported for injuries incurred in 10,064 motor vehicle accidents, 4,587 falls, 4,015 lacerations/stabwounds, 1,796 beatings, 1,270 gunshots, and 952 auto-pedestrian accidents. Analysis of the 156 zones showed a disproportionate number of EMS responses in the city center with two centralmost grids accounting for about 25% of all responses. Call volume then progressively diminished toward the periphery of the city. However, with some very minor exceptions, the relative incidence and severity of the various injury mechanisms remained proportionally uniform within each zone, regardless of geographic location. Therefore, contrary to popular notoriety, the incidence and associated severity of any given injury type generally was not necessarily predicted by any particular neighborhood predilection for it, but rather by the overall demand for EMS in that zone of the city.  相似文献   
80.
To find antiviral agents, various sulfonamidobenzophenone oximes (II) were synthesized from the appropriate m-sulfonamidobenzophenones by hydroxylamine reaction. The reaction products were generally obtained as syn/anti mixtures which were separable by fractional crystallization. The anti isomer had more potent antipoliovirus activity than the syn isomer. Various sulfonamidobenzamides (III) which were structurally related to II were synthesized by the reactions of amino-substituted benzamides with sulfuryl chloride or amines with (aminosulfonyl)benzoyl chloride. Antiviral activity was examined by the plaque-inhibition test. Compounds 5, 36, and 69 exhibited strong antipicornavirus activity. The structure-activity relationships are discussed.  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