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   995599篇
  免费   76788篇
  国内免费   2612篇
耳鼻咽喉   12969篇
儿科学   34461篇
妇产科学   28465篇
基础医学   145275篇
口腔科学   27709篇
临床医学   90190篇
内科学   193400篇
皮肤病学   22909篇
神经病学   79103篇
特种医学   38400篇
外国民族医学   305篇
外科学   149529篇
综合类   23729篇
一般理论   385篇
预防医学   77780篇
眼科学   22592篇
药学   71858篇
  3篇
中国医学   2029篇
肿瘤学   53908篇
  2018年   10566篇
  2017年   8245篇
  2016年   9380篇
  2015年   10604篇
  2014年   14424篇
  2013年   22018篇
  2012年   29002篇
  2011年   30853篇
  2010年   18507篇
  2009年   17459篇
  2008年   28813篇
  2007年   30477篇
  2006年   30973篇
  2005年   29658篇
  2004年   28944篇
  2003年   27818篇
  2002年   26827篇
  2001年   46935篇
  2000年   48046篇
  1999年   40272篇
  1998年   11184篇
  1997年   10102篇
  1996年   10166篇
  1995年   9779篇
  1994年   9094篇
  1993年   8483篇
  1992年   32249篇
  1991年   31463篇
  1990年   31010篇
  1989年   29881篇
  1988年   27170篇
  1987年   27328篇
  1986年   25436篇
  1985年   24603篇
  1984年   18401篇
  1983年   15515篇
  1982年   9290篇
  1981年   8375篇
  1979年   16862篇
  1978年   12217篇
  1977年   10316篇
  1976年   9754篇
  1975年   10179篇
  1974年   12319篇
  1973年   11844篇
  1972年   10886篇
  1971年   10116篇
  1970年   9378篇
  1969年   8725篇
  1968年   8104篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
OBJECTIVE: To assess the impact of activity restriction (AR) on the incidence of preterm birth in women treated for preterm labor testing negative for fetal fibronectin (fFN). STUDY DESIGN: Women who were diagnosed with preterm labor and tocolyzed with magnesium sulfate were concurrently screened with fFN for the purpose of subsequent management. Included were consenting patients with negative fFN, gestational age 23 0/7-33 6/7 weeks, cervical dilation < or =3 cm, and minimal vaginal bleeding. Patients were randomized to AR or no AR. Primary study outcome was incidence of preterm delivery and interval from randomization to delivery. RESULTS: A total of 73 women with negative fFN were randomized (36 with AR, 37 without AR). The overall preterm birth rate was 40%, with 44.4% of patients with AR and 35.1% of patients without AR delivering preterm, p=0.478. CONCLUSION: Maternal AR did not impact pregnancy outcome. The incidence of preterm birth in symptomatic women testing fFN negative was higher than previously reported.  相似文献   
992.
Between January 1977 and December 1982, 66 consecutive patients have been treated for unilateral, rapidly progressing, non metastatic breast cancer. They were divided into three groups: Group A (n = 10): tumor whom volume had increased during the 2 months before diagnosis; Group B (n = 30): inflammatory signs (erythema, skin oedema, elevated local temperature) involving less than one half of the breast; Group C (n = 26): inflammatory signs involving more than one half of the breast. All patients where managed similarly: 3 to 4 courses of chemotherapy (CMF: n = 24; AVCF: n = 42), then loco regional irradiation therapy with cobalt 60, followed by maintenance chemotherapy, only if the first chemotherapy had proved effective (CMF: n = 13; AVCF: n = 27). Nine patients with residual tumor after radiotherapy underwent mastectomy with axillary dissection. The actuarial 5 years survival for the whole group is 29%, and respectively 49%, 38% and 9% for the groups A, B and C. The median disease free intervals are 43, 29 and 12 months respectively. Fifteen prognostic factors likely to influence overall survival or disease free survival were evaluated. With univariate analysis, 8 factors were found to be of individual prognostic value: extent of initial erythema, erythema present after initial chemotherapy, erythema present after radiotherapy, non menopaused status, tumor diameter greater than 10 cms, residual breast tumor (clinical or radiographic) after maintenance chemotherapy, supra clavicular adenopathy (N3). Age at the diagnosis, type of chemotherapy, or performance of a radical mastectomy did not influence the prognosis. Multivariate analysis using the Cox-model isolated 3 factors of bad prognosis: erythema involving the whole breast at initial diagnosis, erythema present at the end of initial chemotherapy, N3.  相似文献   
993.
The synthesis of barbituric acid derivatives containing α-phenylskatyl residues substituted at C(5) is described. The initial compound was α-phenylnorgramine, which had been previously successfully used for the alkylation of a series of CH-acids, in particular, for the synthesis of diethyl-1H-indol-3-yl(phenyl)methylmalonate. This compound has been used to obtain a series of 2-thiobarbituric acid derivatives, which are expected to possess antioxidant, membrane protector, and radioprotector properties.__________Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 39, No. 1, pp. 29 – 33, January, 2005.  相似文献   
994.
995.
BACKGROUND: Alternaria alternata is one of the most important allergenic fungi worldwide. Mannitol dehydrogenase (MtDH) has previously been shown to be a major allergen of Cladosporium herbarum and cross-reactivity has been demonstrated for several fungal allergens. OBJECTIVE: The present study's objective was to clone the MtDH from an A. alternata cDNA library, express and purify the recombinant non-fusion protein and test its IgE-binding properties. Methods A cDNA library prepared from A. alternata hyphae and spores was screened for mannitol dehydrogenase by DNA hybridization with the radioactively labelled C. herbarum homologue as a probe. The resulting clone was sequenced and heterologously expressed in Escherichia coli as a recombinant non-fusion protein, which was purified to homogeneity and analysed for its IgE-binding capacity. RESULTS: The coding sequence of the full-length cDNA clone comprises 798 bp encoding a protein with a molecular mass of 28.6 kDa and a predicted pI of 5.88. Protein sequence analysis revealed an identity of 75% and a homology of 86% between the MtDHs of A. alternata and C. herbarum. The functional mannitol dehydrogenase was expressed in the E. coli strain BL21(DE3) transformed with the vector pMW172 and purified to homogeneity. The enzyme catalyses the NADPH-dependent conversion of d-fructose to d-mannitol. In IgE-ELISA and immunoblots, MtDH is recognized by 41% of A. alternata-allergic patients. In vivo immunoreactivity of the recombinant MtDH was verified by skin prick testing. Finally, inhibition-ELISA experiments confirmed cross-reactivity between the MtDHs of A. alternata and C. herbarum. CONCLUSION: Mannitol dehydrogenase (Alt a 8) represents an important new allergen of the ascomycete A. alternata that might be suitable for improving diagnostic and therapeutic procedures.  相似文献   
996.
997.

Background  

Although training and education have long been accepted as integral to disaster preparedness, many currently taught practices are neither evidence-based nor standardized. The need for effective evidence-based disaster training of healthcare staff at all levels, including the development of standards and guidelines for training in the multi-disciplinary health response to major events, has been designated by the disaster response community as a high priority. We describe the application of systematic evidence-based consensus building methods to derive educational competencies and objectives in criteria-based preparedness and response relevant to all hospital healthcare workers.  相似文献   
998.
OBJECTIVE: The aim of this study was to evaluate the biocompatibility of Portland cement with the addition of iodoform, compared to MTA (ProRoot). STUDY DESIGN: Eighteen Wistar albino rats were divided into 3 groups of 6 animals each. Polyethylene tubes were filled either with freshly mixed MTA or Portland cement mixed with iodoform (20% wt/wt) and implanted subcutaneously. An empty tube served as control. After 7, 30, or 60 days, the implants together with the surrounding tissues were removed in blocks. Sections were evaluated for the presence and thickness of a fibrous capsule, presence of granulation tissue, and the severity of inflammatory response. Data were submitted to nonparametric statistical analysis with individual comparisons between groups at a significance level of P < 0.05. RESULTS: There were no differences between inflammatory responses at 7 and 30 days. After 60 days from surgical removal, there was significantly more tissue reaction to the MTA and Portland cement compared to the control group. CONCLUSION: There were no significant differences regarding inflammatory responses between MTA and Portland cement with iodoform after 7, 30, or 60 days. After 60 days, the fibrous capsule around the Portland cement appeared more organized than tissue surrounding MTA implants. After 60 days, there was still a significantly increased tissue reaction to the 2 cements compared to the empty polyethylene tubes.  相似文献   
999.
Perianal mucinous adenocarcinoma is a rare tumour which may be associated with long‐standing chronic perianal sepsis. Early diagnosis is challenging and is based on a high index of clinical suspicion and specific histological features. Definitive treatment is surgical, in the form of an abdomino‐perineal resection. We hereby describe a case of a perianal mucinous adenocarcinoma arising from long‐standing recurrent perianal fistula and complement this with a brief review of the literature pertaining in particular to the management of this condition.  相似文献   
1000.
Abstract We report a case of SMV injury in a critically ill patient. The patient was a 19-year-old woman involved in a motor vehicle collision. Her injuries included grade II splenic and renal lacerations, devascularized and lacerated right and transverse colon, a transected transverse mesocolon, a massive shear injury of her abdominal wall, and two partial SMV transections. At initial damage control laparotomy, the SMV was ligated, the devascularized bowel resected and a temporary abdominal closure applied. At re-operation, a mesocaval shunt using saphenous vein was employed. The shunt failed and the patient required a saphenous vein jump graft. Although visceral vascular injuries are rare, ligation of the SMV in a damage control situation is acceptable. This case study is the first to discuss appropriate treatment when interruption to a patient's collateral visceral venous drainage limits the surgeon’s ability to ligate. In these situations, bypass shunts may be successful.  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