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   130475篇
  免费   8319篇
  国内免费   1860篇
耳鼻咽喉   1413篇
儿科学   2822篇
妇产科学   2698篇
基础医学   16220篇
口腔科学   4037篇
临床医学   12047篇
内科学   28867篇
皮肤病学   2766篇
神经病学   9898篇
特种医学   3032篇
外国民族医学   6篇
外科学   15935篇
综合类   6498篇
现状与发展   2篇
一般理论   42篇
预防医学   11485篇
眼科学   2717篇
药学   10222篇
  53篇
中国医学   2581篇
肿瘤学   7313篇
  2024年   215篇
  2023年   1154篇
  2022年   1960篇
  2021年   3743篇
  2020年   2577篇
  2019年   2965篇
  2018年   4132篇
  2017年   3184篇
  2016年   3024篇
  2015年   4238篇
  2014年   5029篇
  2013年   6418篇
  2012年   11561篇
  2011年   11812篇
  2010年   6403篇
  2009年   5136篇
  2008年   9271篇
  2007年   9389篇
  2006年   8924篇
  2005年   8406篇
  2004年   7242篇
  2003年   6677篇
  2002年   6075篇
  2001年   2059篇
  2000年   2469篇
  1999年   1362篇
  1998年   535篇
  1997年   446篇
  1996年   414篇
  1995年   359篇
  1994年   287篇
  1993年   251篇
  1992年   250篇
  1991年   204篇
  1990年   161篇
  1989年   164篇
  1988年   122篇
  1987年   109篇
  1986年   127篇
  1985年   134篇
  1984年   157篇
  1983年   115篇
  1982年   155篇
  1981年   146篇
  1980年   123篇
  1979年   88篇
  1978年   67篇
  1977年   72篇
  1976年   70篇
  1974年   56篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
191.
The gene coding for Eimeria tenella protein EtMIC3 was cloned by screening a sporozoite cDNA library with two independent monoclonal antibodies raised against the oocyst stage. The deduced sequence of EtMIC3 is 988 amino acids long. The protein presents seven repeats in tandem, with four highly conserved internal repeats and three more divergent external repeats. Each repeat is characterised by a tyrosine kinase phosphorylation site, WRCY, and a reminiscent motif of the thrombospondin1 (TSP1)-type I domain, CXXXCG. The protein EtMIC3 is localised at the apex of free parasite stages. It is not detected in the early intracellular parasite stage but is synthesised in mature schizonts. Secretion of the protein is induced when sporozoites are incubated in complete medium at 41 degrees C. Strangely enough, the two independent mAb that allow cloning of EtMIC3 interfere with parasitic growth in different ways. One is able to inhibit parasite invasion whereas the other inhibits development. Expression and localisation of the protein EtMIC3 are consistent with a protein involved in the invasion process as is expected for a microneme protein.  相似文献   
192.
OBJECTIVE: The lack of a beneficial long-term cardiovascular effect of hormone therapy and the early incidence of cardiovascular adverse events observed in recent randomized studies have been related to a heightened inflammatory effect of hormone therapy. DESIGN: We evaluated the effect of different postmenopause therapies on inflammatory markers and endothelial function in 205 postmenopausal women before and after therapy. RESULTS: all postmenopausal women, estrogens alone increased plasma levels of C-reactive protein (CRP) but decreased all other markers of inflammation including interleukin-6 (IL-6) (CRP: +75% +/- 11%, intracellular adhesion molecule: -21% +/- 4%, vascular cell adhesion molecule: -15% +/- 6%, E-selectin: -18% +/- 4%, s-thrombomodulin -10.5% +/- 3.7%, IL-6 -14% +/- 6%; percent changes, P < 0.01 compared with baseline). Raloxifene and tibolone did not significantly affect the overall inflammatory milieu. In a minority of patients, estrogen-progestogen associations and tibolone increased IL-6 levels and induced unfavorable changes on inflammation markers (CRP: +93% +/- 8%, intracellular adhesion molecule: -3% +/- 2%, vascular cell adhesion molecule: -5% +/- 2%, E-selectin: +6% +/- 2%, s-thrombomodulin: +5% +/- 2%, IL-6: +12% +/- 4%; percent changes compared with baseline). Patients with increased IL-6 levels were older and had a longer time since menopause. In all patients except those with increased IL-6 levels, hormone therapy improved endothelial function, whereas tibolone and raloxifene did not significantly change endothelial function compared with baseline. A worsening of endothelial function was detected in patients with increased IL-6 levels during therapy. CONCLUSIONS: Postmenopausal hormone therapy is associated with decreased vascular inflammation; however, in patients with a longer time since menopause, postmenopause hormone therapy may increase inflammation and worsen endothelial function. These unfavorable vascular effects may be detected by an elevation in IL-6 levels and by a lack of improvement in endothelial function.  相似文献   
193.
Schistosomiasis: an unusual cause of tubal infertility   总被引:3,自引:0,他引:3  
A case report of a Nigerian woman having an unusual cause oftubal infertility is presented. On histological examinationof the Fallopian tube, ova of Schistosoma haematobium enclosingliving miracidia were found in the smooth muscle layer of theFallopian tube and its mesosalpinx. Mechanisms of tubal involvementare analysed. The case indicates the need to consider schisto-somiasisas a possible aetiological factor in patients with tubal infertilitycoming from areas where the disease is endemic.  相似文献   
194.
Two siblings presenting slight mental retardation showed an abnormal elimination of histidine, their blood levels for the same amino acid being normal. The percentage of tubular resorption of histidine was calculated in both boys, and the values were 40.1 per cent (case 1) and 52.8 per cent (case 2). All other amino acids essayed were normal. After an oral overload test with histidine, a low intestinal absorption was found in the two boys, the values of this test in the parents being intermediate between those of the children and of the three normal controls and corresponding to heterozygosity. In view of the studies carried out on the two boys, it is possible to conclude that they are suffering from an impairment in their histidine membrane transport system which affects the kidney and intestines. Since they are siblings a genetically determined trait may be suspected.  相似文献   
195.
A frame-shift 9254del5 mutation was independently identified in 12 families, eleven of them with Spanish ancestors, in a BRCA2 screening performed in 841 breast and/or ovarian cancer families and in 339 women with breast cancer diagnosed before the age of 40 at different centers in France and Spain. We sought to analyze in detail the haplotype and founder effects of the 9254del5 and to estimate the time of origin of the mutation. Eight polymorphic microsatellite markers and two BRCA2 polymorphisms were used for the haplotype analyses. The markers were located flanking the BRCA2 gene spanning a region of 6.1 cM. Our results suggest that these families shared a common ancestry with BRCA2 9254del5, which is a founder mutation originating in the Northeast Spanish, with an estimated age of 92 (95% CI 56-141) generations.  相似文献   
196.
Seizures are common in advanced stages of immunodeficiency virus (HIV) infection. HIV-infected outpatients and inpatients in the national hospital in Bobo-Dioulasso among whom seizures occurred had been recruited over four years. There were mainly male (30/13) with an average age of 35 years with extremes ranging from 22 to 60 years. New-onset generalised seizures occurred in all cases of cryptococcal meningitis or partial motor secondary generalised in 64% among patients with suspected cerebral toxoplasmosis due to the efficiency of the treatment of the antitoxoplasmic proof. Identified causes such as suspected cerebral toxoplasmosis (65%), suspected tuberculous meningitis (7%) as CSF culture is not available, cryptococcal meningitis (16%) were found in this study. In four cases among 43 patients, no identified causes could be determined. CD4 lymphocytes count which was available in 24 patients was under 200/41 in 74% of the cases. This study indicates clearly that seizures in young adults are strongly associated with focal brain lesions and cerebral toxoplasmosis is becoming an important cause of seizure in tropical area. This should imply a screening of toxoplasmosis with new-onset seizure in young people.  相似文献   
197.
We conducted a longitudinal study about daily variation of Wistar male rats' behavior in the elevated plus-maze (EPM) evaluated in the 1st, 2nd, 3rd, 6th, 12th, and 18th months of life. Animals were submitted to the plus-maze in 12 sessions at 2-h intervals (n=72, 6 per time point). Spontaneous rest-activity rhythm of four animals was assessed by observation of 24-h videotape records. Time series were analyzed by Cosinor method. Behavioral rates on the six occasions and in light and dark phases were compared by means of two-way ANOVA with repeated measures. Exploratory behavior in EPM was smaller in the light phase and in older animals. Higher values of open and closed arms exploration were observed in the first and third months of the dark phase, and in the first month of the light phase. Adjustment to the 24-h period was significant at all stages for rest-activity data, number of entries in closed arms, and time on center, and for three to five stages for open-arm exploration. In general, 24 h variability was more pronounced in younger animals compared with older ones. The present study showed that: (1). a significant amount of total variability of the behavioral indexes analyzed could be attributed to 24 h variation, (2). light/dark phases differences in EPM exploration were present at all developmental stages, (3). older Wistar rats explored less the EPM and were less active in their home cage compared with younger ones, and (4). behavioral indexes (EPM) decrease was phase related and partially related to a reorganization of rest-activity rhythm.  相似文献   
198.
We report a case of osteomyelitis caused by Enterobacter cancerogenus resistant to aminopenicillins in a 56-year-old male who had a motorcycle accident and suffered from multiple bone fractures with abundant environmental exposure. E. cancerogenus has rarely been associated with human infections, and its clinical significance remains unclear.  相似文献   
199.
A lipopolysaccharide (LPS)-induced inflammation prior to an hepatic resection has been shown to enhance liver regeneration in rat. The aim of the present study was to investigate the expression of hepatocyte growth factor (HGF) and its c-Met receptor under such experimental conditions. Animals were submitted to a two-third hepatectomy or a LPS challenge carried out 12 h prior to resection. Non parenchymal and parenchymal cells were isolated from livers obtained at various times post-hepatectomy. Quantitative RT-PCR for HGF and c-Met mRNAs were performed from total liver or purified cell fractions and HGF mRNA was also analyzed by in situ RT-PCR on liver sections. A LPS challenge alone induced a marked up-regulation of HGF mRNA level in whole liver and isolated hepatocytes. Furthermore, when partial hepatectomy (PH) was preceded by a LPS challenge, an increase of HGF mRNA level was seen in whole liver and contrasted with a decreased level in non parenchymal cells. These results were confirmed by in situ RT-PCR. In isolated hepatocytes from endotoxemic rats, the mRNA level for the LPS-specific membranous receptor mCD14 was markedly up-regulated and even more so when LPS was followed by PH. Moreover, a TNFalpha challenge alone induced an up-regulation of HGF mRNA in hepatocytes and a down-regulation in non parenchymal cells (NPCs). Overall, when a LPS challenge is given prior to PH the major source of hepatic HGF appears to be the hepatocyte itself rather than NPCs. An autocrine HGF/c-Met loop which promotes the proliferative potential of the hepatic parenchymal cell and participates in liver regeneration is postulated.  相似文献   
200.
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