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   7909篇
  免费   675篇
  国内免费   50篇
耳鼻咽喉   80篇
儿科学   166篇
妇产科学   251篇
基础医学   1100篇
口腔科学   144篇
临床医学   1165篇
内科学   1219篇
皮肤病学   96篇
神经病学   543篇
特种医学   452篇
外科学   866篇
综合类   145篇
一般理论   3篇
预防医学   759篇
眼科学   223篇
药学   517篇
中国医学   4篇
肿瘤学   901篇
  2021年   103篇
  2020年   49篇
  2019年   107篇
  2018年   117篇
  2017年   92篇
  2016年   83篇
  2015年   114篇
  2014年   174篇
  2013年   254篇
  2012年   311篇
  2011年   308篇
  2010年   212篇
  2009年   188篇
  2008年   315篇
  2007年   328篇
  2006年   336篇
  2005年   298篇
  2004年   333篇
  2003年   325篇
  2002年   296篇
  2001年   281篇
  2000年   268篇
  1999年   290篇
  1998年   176篇
  1997年   163篇
  1996年   143篇
  1995年   125篇
  1994年   106篇
  1993年   105篇
  1992年   157篇
  1991年   195篇
  1990年   187篇
  1989年   163篇
  1988年   166篇
  1987年   153篇
  1986年   137篇
  1985年   166篇
  1984年   113篇
  1983年   100篇
  1982年   62篇
  1981年   61篇
  1980年   63篇
  1979年   94篇
  1978年   61篇
  1977年   57篇
  1976年   49篇
  1975年   58篇
  1974年   58篇
  1973年   67篇
  1972年   55篇
排序方式: 共有8634条查询结果,搜索用时 15 毫秒
71.
Renal disease in type I glycogen storage disease   总被引:8,自引:0,他引:8  
Although kidney enlargement occurs in Type I glycogen storage disease, renal disease has not been considered a major problem. Death from renal failure in three patients known to us prompted a study of renal function in this disorder. Of the 38 patients with Type I glycogen storage disease under our care, the 18 children under 10 years old had normal renal function. Fourteen of the 20 older patients (13 to 47 years) had disturbed renal function, manifested by persistent proteinuria; many also had hypertension, hematuria, or altered creatinine clearance. Progressive renal insufficiency developed in 6 of these 14 patients, leading to three deaths from renal failure. At the onset of proteinuria, creatinine clearance was increased in seven patients (3.05 +/- 0.68 ml per second per 1.73 m2 of body-surface area; range, 2.47 to 4.13 [normal range, 1.33 to 2.33 ml per second per 1.73 m2]). Renal biopsies were performed in three patients after an average of 10 years of proteinuria. All three biopsies demonstrated focal segmental glomerulosclerosis in various stages of progression. Our data suggest that chronic renal disease is a frequent and potentially serious complication of Type I glycogen storage disease. In addition to treating hypoglycemia vigorously, physicians should monitor renal function carefully in patients with this disorder.  相似文献   
72.
73.
DNA fingerprinting of Candida dubliniensis isolates using the species-specific probe Cd25 previously showed that this species consists of two distinct groups, termed Cd25 group I and Cd25 group II. The present study investigated the population structure of 30 C. dubliniensis oral isolates from Saudi Arabia and Egypt using Cd25 fingerprinting and rRNA gene internal transcribed spacer region-based genotyping. Cd25 fingerprinting analysis of these isolates revealed two distinct populations, the first of which consisted of 10 closely related genotype 1 isolates (average similarity coefficient [S(AB)] value, 0.86). The second population of 20 isolates was much more heterogeneous (average S(AB) value, 0.35) and consisted of two distinct subpopulations, one of which consisted of genotype 3 isolates (n = 13) and the other of genotype 4 isolates (n = 7). A mixed dendrogram generated from the fingerprint data from the 30 Saudi Arabian and Egyptian isolates, 5 Israeli isolates, and 51 previously characterized international isolates (32 of Cd25 group I and 19 of Cd25 group II) revealed the presence of three distinct main clades. The first corresponded to the previously described Cd25 group I and contained all the Saudi Arabian, Egyptian, and Israeli genotype 1 isolates mixed with international isolates. The second clade corresponded to the previously described Cd25 group II and contained three Israeli isolates, one genotype 2 isolate, one genotype 3 isolate, and a genotype 4 variant isolate, which were mixed with international isolates. The third clade has not been described before and consisted solely of the 20 Saudi Arabian and Egyptian genotype 3 and 4 isolates identified in this study and a previously described genotype 4 Israeli isolate. All 20 Cd25 group III isolates exhibited high-level resistance to 5-flucytosine (MIC > or = 128 microg/ml), whereas all Cd25 group I and Cd25 group II isolates tested (10 Saudi Arabian and Egyptian, 16 Israeli, and 24 international) were susceptible to 5-flucytosine (MIC < or = 0.125 microg/ml). The results of this study show for the first time the presence of a novel 5-flucytosine-resistant clade of C. dubliniensis (Cd25 group III) that is predominant among isolates from Saudi Arabia and Egypt and absent from a previously characterized international collection of 98 isolates from 15 countries.  相似文献   
74.
OBJECTIVE: To accurately determine whether there are any features of an abnormal cervical smear that predispose to the production of a false negative report, in order to gain insight into why false negative reports are issued, and to establish whether there are steps that can be taken to reduce them. DESIGN: A quantitative retrospective analysis using the AxioHOME microscope of the number, size, and spatial distribution of abnormal cells in a set of 50 slides comprising a mixture of false negative and true positive cervical smears. SETTING: Five different cytology laboratories in the United Kingdom. RESULTS: False negative smears were found to be quantitatively different from true positive smears. They contained significantly fewer abnormal cells (median number of abnormal cells for false negatives = 173, median number of abnormal cells for true positives = 1712; p < 0.004), and these were more likely to be unevenly distributed on the slide. It was possible to predict with a high degree of accuracy whether a smear was a false negative by analysing number and distribution alone (kappa = 0.57). CONCLUSIONS: False negatives are quantitatively different from true positive cervical smears. This has important implications for quality assurance in the UK cervical screening programme. More consideration needs to be given to the effectiveness of existing quality assurance measures, which need to be tailored to the preferential detection of this type of abnormal cervical smear.  相似文献   
75.
Equipment and procedures were devised for quantifying relatively noise-free recordings of low amplitude chin and lip electromyograms (EMGs) during sleep. A total of 28 REM periods were recorded from 5 young adult female Ss. Tonic EMG levels tended to decline toward their lowest level of the night beginning 5 min in advance of REM periods. With very rare exceptions, the lowest EMG levels of the night were maintained throughout REM sleep. During the 20 min of NREM sleep which followed REM periods, mean EMG levels increased over the REM levels but were lower than those recorded during the 20 min of NREM sleep which preceded the REM periods. This pattern of tonic EMG variation obtained for each of the first 3 REM periods of the night.  相似文献   
76.
TestPack Chlamydia (Abbott Laboratories) is a rapid enzyme immunoassay for the direct antigen detection of Chlamydia trachomatis in endocervical specimens. The assay is self-contained, requires no specialized equipment, and yields results in less than 30 min. The clinical performance of TestPack Chlamydia versus chlamydial cell culture was evaluated with a total of 1,694 paired endocervical specimens. Discordant samples were further investigated by immunofluorescent staining and by Chlamydiazyme immunoassay, with confirmatory procedures. The sensitivity of TestPack Chlamydia with less-than-48-h-old specimens was 76.5%, while culture sensitivity was 86.7%. TestPack Chlamydia specificity was determined to be 99.5%. These results indicate that TestPack Chlamydia is an accurate test for chlamydial infection, with a positive predictive value of 96.2%. This assay is suitable for low-volume chlamydial testing in physician offices, clinics, and smaller laboratories.  相似文献   
77.
General practitioners' (GPs') advice against smoking helps smokers to stop; unfortunately, GPs cannot predict which patients will quit following advice. This postal questionnaire survey suggests that where smokers attribute their respiratory symptoms to smoking, they are eight times (95% confidence interval [CI] = 3.0-23.3) more likely to believe that their health will improve if they stop smoking and six times (95% CI = 1.4-23.3) more likely to intend to stop smoking.  相似文献   
78.
The intracellular protozoan parasite Cryptosporidium parvum accumulates host cell actin at the interface between the parasite and the host cell cytoplasm. Here we show that the actin polymerizing proteins Arp2/3, vasodilator-stimulated phosphoprotein (VASP), and neural Wiskott Aldrich syndrome protein (N-WASP) are present at this interface and that host cell actin polymerization is necessary for parasite infection.  相似文献   
79.
Hybrid cells derived from rat L6 myoblasts and mouse primary fibroblasts (M x F hybrids), as well as those derived from rat L6 myoblasts and mouse primary myoblasts (M x M hybrids), were examined for their ability to engage in myogenesis as judged by muscle fiber formation plus the expression of skeletal muscle myosin and creatine kinase (CK). Of 172 primary hybrid colonies scored, 59% were myogenic in the M x F fusion and 97% exhibited muscle fiber formation in the M x M fusion. Individual hybrid clones from each cross were isolated, expanded and analyzed for myogenic capabilities as well. All three M x M and all ten M x F isolated clones exhibited preferential elimination of mouse chromosomes. Nonetheless, all were capable of fusing spontaneously and of elaborating skeletal muscle myosin and CK. The three M x M hybrids expressed only MM-CK whereas nine out of ten M x F hybrids produced all three CK isoenzymes (MM, MB, BB). These results suggest that M x M hybrids express CK patterns reminiscent of the rat L6 parental cells while M x F hybrids apparently mimic mouse muscle fiber CK patterns. Various models are discussed which address these phenomena.  相似文献   
80.
Conventional tube cell culture has been recognised as the most sensitive technique available for human cytomegalovirus (HCMV) detection. Low-speed centrifugation of specimen inocula onto cell culture monolayers has been shown to increase the efficiency of infection with the AD 169 strain of HCMV. Therefore a centrifugal force of 900g for 1 hour at 37 degrees C was used to enhance the detection of HCMV cytopathic effect (CPE) in shell vials that contained circular coverslips with a monolayer of human embryonic lung (HEL) fibroblasts. Of 195 specimens, HCMV CPE was detected in 18 specimens (9.02%) on shell vial culture assay, whereas conventional tube cell culture was positive in only 13 specimens (6.6%). The shell vial culture assay was significantly more sensitive (P less than 0.05). Furthermore the development of the cytopathic effect on shell vial culture assay was significantly earlier (P less than 0.01) and more extensive. Urine samples were sonicated and the results obtained with immunofluorescence using human immune serum demonstrated that sonication increased both the intensity of fluorescence and number of fluorescent foci of HCMV-infected cells and also decreased the non-specific fluorescence of the background.  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