首页 | 官方网站   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   1328篇
  免费   71篇
  国内免费   8篇
医药卫生   1407篇
  2023年   6篇
  2022年   26篇
  2021年   44篇
  2020年   16篇
  2019年   46篇
  2018年   35篇
  2017年   18篇
  2016年   27篇
  2015年   28篇
  2014年   36篇
  2013年   57篇
  2012年   71篇
  2011年   89篇
  2010年   48篇
  2009年   61篇
  2008年   72篇
  2007年   84篇
  2006年   75篇
  2005年   70篇
  2004年   61篇
  2003年   53篇
  2002年   47篇
  2001年   25篇
  2000年   42篇
  1999年   31篇
  1998年   14篇
  1997年   15篇
  1996年   11篇
  1995年   8篇
  1994年   9篇
  1993年   2篇
  1992年   11篇
  1991年   15篇
  1990年   5篇
  1989年   19篇
  1988年   13篇
  1987年   17篇
  1986年   14篇
  1985年   10篇
  1984年   8篇
  1983年   12篇
  1982年   7篇
  1981年   8篇
  1980年   6篇
  1979年   13篇
  1978年   5篇
  1977年   6篇
  1976年   3篇
  1975年   2篇
  1974年   3篇
排序方式: 共有1407条查询结果,搜索用时 0 毫秒
71.
The predictive role of the degree of endocrine responsiveness to preoperative chemotherapy (PCT) is unclear. We reviewed pretreatment biopsies of 553 patients with locally advanced breast cancer who were treated with PCT. The incidence of pathological complete remission (pCR) and outcome were assessed with respect to the degree of estrogen (ER) and progesterone receptor (PgR) expression (ER and PgR absent, vs. ER or PgR 0–49%, vs. ER and PgR ≥50% of the cells positive). A statistically significant higher pCR rate was observed at the multivariate analysis for patients with ER and PgR absent tumors (17.7%) versus patients with tumors expressing high ER and PgR (0%) (OR 14.4 P < 0.001). Despite the higher incidence of pCR, a statistically significant worse disease-free survival (DFS), and overall survival (OS) was observed for patients with ER and PgR absent tumors versus patients with tumors expressing high ER and PgR (HR 6.4, 95% CI 3.5–11.6, for DFS; HR 3.6 95% CI 2.4–5.6 for OS). Response and outcome after PCT are correlated with the degree of expression of steroid hormone receptors. Studies on tailored preoperative therapies are needed.  相似文献   
72.
Central nervous system metastases in patients with ovarian carcinoma   总被引:1,自引:0,他引:1  
BACKGROUND: Central nervous system (CNS) involvement by ovarian carcinomais rare. PATIENTS AND METHODS: From September 1982 to September 1994, 23 patients with CNSmetastases from ovarian carcinoma were observed in our institution. RESULTS: Their median age at the time of CNS metastasis diagnosis was59 years, and the median interval between diagnosis of ovariancancer and documentation of the metastasis was 35 months. Themost common symptoms related to CNS involvement were motor weakness,headache, seizures, dizziness and visual disturbances. One patienthad meningeal carcinomatosis; 22 had parenchyma] lesions (18cerebral and 4 cerebellar). Nine patients had a single CNS lesion,and 13 had multiple metastatic sites. CNS was the only siteof disease in 9 patients, while 8 had concomitant extra-peritonealdissemination. The median survival (MS) from diagnosis of cerebralmetastases for the entire series was five months. Four patientswere not treated (MS 3 months); 14 received radiotherapy (MS5.5 months), and five underwent surgical resection of solitarymetastases followed by radiotherapy (MS 17 months). Number ofCNS lesions, extent of the disease at the time of CNS metastasisand treatment were the only factors which significantly affectedsurvival. CONCLUSIONS: The prognosis of patients with CNS metastasis from ovarian carcinomaappears poor. However, early diagnosis followed by multimodaltreatment may result in significant palliation and improve overallsurvival in a selected group of patients. central nervous system metastasis, ovarian carcinoma  相似文献   
73.
74.
X-ray fluorescence tomography promises to map elemental distributions in unstained and unfixed biological specimens in three dimensions at high resolution and sensitivity, offering unparalleled insight in medical, biological, and environmental sciences. X-ray fluorescence tomography of biological specimens has been viewed as impractical—and perhaps even impossible for routine application—due to the large time required for scanning tomography and significant radiation dose delivered to the specimen during the imaging process. Here, we demonstrate submicron resolution X-ray fluorescence tomography of a whole unstained biological specimen, quantifying three-dimensional distributions of the elements Si, P, S, Cl, K, Ca, Mn, Fe, Cu, and Zn in the freshwater diatom Cyclotella meneghiniana with 400-nm resolution, improving the spatial resolution by over an order of magnitude. The resulting maps faithfully reproduce cellular structure revealing unexpected patterns that may elucidate the role of metals in diatom biology and of diatoms in global element cycles. With anticipated improvements in data acquisition and detector sensitivity, such measurements could become routine in the near future.  相似文献   
75.
76.
BACKGROUND AND OBJECTIVE: A novel non-enveloped DNA virus, called TT virus (TTV), has been reported to be associated with post-transfusion hepatitis of unknown etiology. Although its clinical role still remains obscure, its presence in blood donations might cause problems. It, therefore, appeared of interest to investigate TTV prevalence in voluntary blood donors. DESIGN AND METHODS: A total of 595 Italian blood donors with and without elevated serum alanine aminotransferase (ALT) levels were tested by polymerase chain reaction using two sets of semi-nested primers that amplify the well-known region in the N22 clone. The amplified products were then sequenced to assess the genotype by phylogenetic and restriction fragment length polymorphism analyses. RESULTS: The prevalence of TTV in blood donors was 5+/-1.9% (25 out of 500) with a 95% confidence limit. A similar prevalence was found in 95 selected blood donors with increased ALT levels. A viral load of 10(3)-10(4) viral DNA molecules/mL was found, thus indicating a rather narrow range of variability. A phylogenetic tree built up on the basis of 210 base sequences of ORF1 allowed isolates to be classified into 2 groups corresponding, at least, to two of the putatives TTV genotypes, group 1 and group 2 of Okamoto's classification. A similar classification was also obtained by site restriction enzyme analysis. INTERPRETATION AND CONCLUSIONS: The results show that TTV infection is present among Italian blood donors. No significant difference in prevalence of TTV infection was found between patients with normal and increased ALT, making the association between TTV infection and human hepatitis questionable.  相似文献   
77.
PURPOSE: Chlamydia psittaci (Cp) has been associated to ocular adnexal lymphomas (OAL) with variable geographic distribution. Herein, we used multiple Chlamydia detection tools to identify Cp elementary bodies-containing cell and to assess Cp prevalence in both nodal and extranodal lymphomas. EXPERIMENTAL DESIGN: TETR-PCR, immunohistochemistry, immunofluorescence, electron microscopy, and laser-capture microdissection were done in 35 OALs to define their effect in Chlamydia detection and, moreover, to identify the Cp cellular carrier. Cp prevalence was screened by TETR-PCR in 205 extraorbital lymphomas and 135 nonneoplastic controls. RESULTS: Twenty-six (74%) OALs were associated with Cp infection: immunohistochemistry, immunofluorescence, and laser-capture microdissection-assisted PCR showed that monocytes/macrophages were the Cp carriers; electron microscopy showed the presence of intact Cp elementary bodies into these cells. Immunohistochemistry and TETR-PCR showed a 70% concordance rate (P = 0.001). Cp DNA was equally prevalent in non-OAL, nodal, and extranodal lymphomas: among the latter, it was more common in diffuse large B-cell lymphomas of the skin (P = 0.03) and Waldeyer's ring. CONCLUSIONS: This multiparametric approach shows, for the first time, that monocytes/macrophages are the carriers of Cp, Cp seems preferentially associated with lymphomas arising in organs primarily exposed to antigens. The clinical implications of these findings deserve to be prospectively investigated.  相似文献   
78.
It is well known that male ceramic workers have elevated risks of chronic silicosis. The objective of this study was to assess whether female ceramic workers also have an increased risk of silicosis and whether these women have decreased lung function related to silica exposure. Ceramic workers from Civitacastellana, Italy, were enrolled in health surveillance during the 1970s. A total of 642 women were under surveillance; a respiratory monitoring program was conducted from 1974 to 1987, with follow-up through 1991 that included annual chest radiography and measurement of lung function. Radiography findings were defined as silicosis if the chest films were > or =1/0 with small, rounded opacities. Multiple linear regression models for repeated measures (generalized estimating equations) were run to evaluate associations of forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV(1)) with years of exposure and radiograph opacities. Nine cases of silicosis were identified on the basis of radiographic evidence. Silicosis risk was not associated with smoking but was related to employment before 1970 and demonstrated a dose-response gradient for years of exposure. FVC and FEV(1) both showed significant (p < 0.05) associations with duration of exposure and with positive radiography findings. The results for female ceramic workers are consistent with those for male employees regarding exposure to fibrogenic dusts.  相似文献   
79.
We studied nine Italian families with a pure form of autosomal dominant spastic paraplegia (ADHSP) to assess the frequency of mutations in the SPG4 gene. We observed marked intrafamilial variability in both age-at-onset and clinical severity, ranging from severe congenital presentation to mild involvement after age 55 years to healthy carriers of the mutation after age 70. Four of nine probands harboured SPG4 mutations, We identified three new SPG4 mutations, all predicting a loss-of-function with apparently important consequences for spastin function. RT-PCR studies predict loss-of-function as a possible mechanism leading to spastin-related HSP. The current study expands the spectrum of allelic variants in SPG4, confirming their pathological significance in pure AD-HSP and suggesting implications for the presumed function of spastin. Received: 15 December 2000, Received in revised form: 29 May 2001, Accepted: 18 June 2001  相似文献   
80.
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-23

京公网安备 11010802026262号