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   5339篇
  免费   434篇
  国内免费   4篇
耳鼻咽喉   114篇
儿科学   185篇
妇产科学   178篇
基础医学   794篇
口腔科学   112篇
临床医学   582篇
内科学   1152篇
皮肤病学   54篇
神经病学   397篇
特种医学   195篇
外科学   686篇
综合类   134篇
一般理论   1篇
预防医学   481篇
眼科学   40篇
药学   310篇
中国医学   7篇
肿瘤学   355篇
  2023年   29篇
  2022年   36篇
  2021年   66篇
  2020年   42篇
  2019年   89篇
  2018年   112篇
  2017年   87篇
  2016年   91篇
  2015年   104篇
  2014年   129篇
  2013年   221篇
  2012年   269篇
  2011年   263篇
  2010年   168篇
  2009年   125篇
  2008年   248篇
  2007年   246篇
  2006年   247篇
  2005年   236篇
  2004年   219篇
  2003年   224篇
  2002年   211篇
  2001年   161篇
  2000年   158篇
  1999年   137篇
  1998年   82篇
  1997年   61篇
  1996年   57篇
  1995年   59篇
  1994年   59篇
  1993年   54篇
  1992年   110篇
  1991年   113篇
  1990年   87篇
  1989年   99篇
  1988年   104篇
  1987年   92篇
  1986年   94篇
  1985年   78篇
  1984年   53篇
  1983年   50篇
  1982年   37篇
  1981年   28篇
  1980年   37篇
  1979年   65篇
  1978年   51篇
  1976年   37篇
  1974年   32篇
  1970年   25篇
  1966年   25篇
排序方式: 共有5777条查询结果,搜索用时 187 毫秒
81.
目的观察去甲硫氨酸全肠外营养对大鼠血清氨基酸谱等的影响.方法 Wistar大鼠24只,随机分为含甲硫氨酸(+MetTPN,n=12)和去甲硫氨酸全肠外营养2组(-MetTPN,n=12),分别给予相应的TPN支持.治疗7d后,每组随机抽取6只大鼠处死,检测血清FAA(HPLC法)、肝肾功能和全血常规,同时作心、肺、肝、肾组织病理学检查.两组其余大鼠继续原TPN治疗,观察生存期.结果 -MetTPN组大鼠血清游离Met、Cys明显降低,Asp、Glu、Ser等显著增高;大鼠体重下降;血清总蛋白和白蛋白水平下降;血常规和肾功能未见明显异常;组织学检查见肝细胞轻度肿胀,细胞核仁增粗,心肺肾未见明显异常;平均生存18d.对照组上述检查未见异常,除一只大鼠因导管并发症于TPN第16d死亡,其余大鼠全部存活.结论 -MetTPN一周可致大鼠血清游离Met、Cys明显降低和Asp、Glu、Ser等显著增高,及轻度肝功能改变;随着-MetTPN时间延长,出现严重的代谢紊乱和器官功能障碍导致死亡.  相似文献   
82.
In differentiating leukemic cells, cyclin-dependent kinase interacting protein (Cip1) is induced and stimulates a G(1) arrest. TPA treated U937 monoblastoid cells expressed Cip1, hypophosphorylated retinoblastoma protein (Rb), arrested in G(1) and differentiated. PKC-zeta cells are U937 cells that overexpress the zeta isoform and display alterations in endogenous PKC isoform expression. TPA treated PKC-zeta cells undergo apoptosis without differentiating. TPA treated PKC-zeta cells express Cip1 and display substantial hypophosphorylation of Rb but fail to arrest in G(1). Thus, a novel phorbol ester dependent signalling pathway exists in which Cip1 induction is associated with the absence of a G(1) arrest and induction of apoptosis rather than differentiation.  相似文献   
83.
PURPOSE OF THE PAPER: Relatively little attention has been paid to cervical cancer control in Asian American populations. We summarize available cervical cancer incidence and mortality dat, present information on levels of Pap testing use, and review factors that may be associated with cervical cancer screening participation. METHODS: We reviewed the literature pertaining to cervical cancer and Pap testing among Asian populations in North America. PRINCIPAL FINDINGS: Cancer registry data suggest that women from Southease Asia have a nearly five­fold increased risk of invasive cervical cancer (when compared to non­Hispanic White women). Filipino and Korean populations also have elevated risks. The excess invasive cervical cancer burden appears to be concentrated among women aged 40 and older. Pap testing use by Asians is less than for all toher racial/ethnic groups in the U.S., and recent studies suggest that over one­third of Vietnamese immigrants have never been screened. Barriers to Pap testing participation by less acculturated Asian women include a lack of familiarity with Western preventive concepts, a lack of knowledge concerning cervical cancer, embarrassment in association with gynecologic exams, the role of women in some Asian cultures, the cost of health care, and language difficulties. CONCLUSIONS: There is a considerable need for ethnoculturally appropriate cervical cancer control programs targeting Asian American populations. RELEVANCE TO ASIAN PACIFIC ISLANDER AMERICAN POPULATIONS: This paper is relevant to Asian American women from East, South, Southeast, and Island Asia.  相似文献   
84.
Objectives. Mexican Americans (MAs), compared to white non‐Hispanics (WNHs), have higher rates of biliary disease, noninsulin dependent diabetes, and endstage renal disease but lower rates of lung cancer, hip fractures, and mortality from coronary heart disease. Relatively little research has been done to identify other ethnic differences in disease incidence. We used surgical procedure rates to confirm known ethnic differences and to explore our clinical suspicion that MAs have higher rates of appendectomy than WNHs.

Methods. We used a registry of surgical procedures at two teaching hospitals in South Texas to calculate proportional operation ratios (PORs) for MAs versus WNHs. These two hospitals are the primary source of acute hospital care for the indigent in the area. The POR is arithmetically identical to proportional incidence and mortality ratios.

Results. MAs underwent appendectomy proportionally more often than WNHs at both hospitals (POR = 1.41 and 1.75, p < 0.0001). Other significant PORs were consistent with known ethnic disease differences in biliary tract operations, vascular access for chronic hemodialysis, lung cancer, and coronary artery bypass.

Conclusions. These findings support the hypothesis that MAs may undergo appendectomy more often than WNHs and so may be at higher risk of appendicitis.  相似文献   

85.
Medical school graduates have become increasingly dependent on former community hospitals for residency programs because charitable institutions attached to medical schools are disappearing. It is not known what impact residencies have on hospitals that were community hospitals. We interviewed private practice physicians, residents, nurses, patients, and other groups in a large former community hospital. Overall, the interviews indicated good support for the hospital's new teaching function. Furthermore, the residents were viewed in very favorable terms by all groups. There were two problem areas. One, some residents seem less sensitive to human relations than private practice physicians and other hospital groups. Two, many private practice physicians are concerned over the number of hospital-salaried physicians and the outpatient care offered by residents supervised by hospital-salaried physicians. This research suggested several recommendations that, if followed, would serve to increase the value of the residency in meeting patient needs in the most effective manner.  相似文献   
86.
The failure of three consecutive treatment protocols to significantly increase the complete remission rate for poor prognosis newly diagnosed patients with acute myelocytic leukemia led to a detailed investigation of the causes of treatment failure. In the majority of cases treatment failure was attributable to "clinical resistance" to therapy. Upon close examination two types of "clinical resistance" were discernible: the failure of chemotherapy to produce adequate cytotoxic effects ("classical" drug resistance), and treatment failure attributed to the rapid regrowth of leukemia cells subsequent to the substantial killing of leukemia cells by cytotoxic therapy ("biological" resistance). Each form of resistance accounted for one-half of the treatment failures.  相似文献   
87.
The activity of an isoenzyme of alkaline phosphatase (FHAP) was measured in serum samples obtained from 1692 individual subjects. The median FHAP concentration in patients with untreated or recurrent cancer (2.73 IU/liter) was two-fold higher than in hospitalized control patients with illnesses other than cancer (1.17 IU/liter) and three-fold higher than in healthy control subjects (0.93 IU/liter). Among patients with either breast or colorectal cancer who were clinically disease free following their initial therapy, the median FHAP concentration (1.54 IU/liter) was intermediate between the median FHAP concentration in patients with untreated or recurrent cancer and that of healthy control subjects. In order to illustrate the potential clinical application of FHAP as a diagnostic cancer marker, we have selected a serum FHAP concentration of 2.22 IU/liter as a reference value above which only 3% of healthy control subjects would have a "positive" test. Utilizing this reference value, 58% of the patients in the present study with untreated or recurrent cancer would have a positive FHAP test, whereas only 11%, of hospitalized patients with illnesses other than cancer would have a positive test. These data suggest that FHAP may be equivalent to the carcinoembryonic antigen as a diagnostic cancer marker.  相似文献   
88.
89.
Carey ME  Kutz S 《Neurosurgery》2000,47(4):985-6; discussion 986-7
OBJECTIVE: To notify neurosurgeons about a modified bayonet forceps that aids application of the vagus nerve stimulating electrode. METHODS: The manufacturer (Codman & Shurtleff, Inc., Raynham, MA) extended the tips of an upward-angled Malis bayonet forceps from 2 mm to 6 mm. RESULTS: The modified bayonet tips, when placed under the vagus nerve, extend well beyond the edge of the usual vagus nerve to easily accept the electrode lead. CONCLUSION: The modified bayonet forceps and depicted wrapping sequence shorten electrode wrapping time.  相似文献   
90.
PURPOSE: Vascular endothelial growth factor (VEGF) is a potent angiogenic agent and plays a major role in tumor growth and metastases. We have previously reported the locoregional (i.p.) delivery of adenovirus-mediated antiangiogenic soluble FLT-1 (sFLT-1; a naturally encoded potent VEGF antagonist) gene therapy to inhibit VEGF action in a murine ovarian carcinoma model. This study was predicated on the fact that systemic delivery of sFLT-1 might allow an approach for therapy of disseminated tumor. The purpose of this study is to test the effects of i.v. delivered, adenovirus-mediated sFLT-1 on the survival duration in a murine ovarian tumor model and to evaluate the safety of i.v.-delivered versus i.p.-delivered adenovirus-mediated sFLT-1 in non-tumor-bearing mice. EXPERIMENTAL DESIGN: To determine the effects of i.v.-administered adenovirus-mediated sFLT-1 on survival duration of mice bearing i.p. human ovarian tumors, an E1A/B-deleted, (replication-deficient) infectivity-enhanced recombinant adenovirus AdRGDGFPsFLT-1 encoding cDNA for both sFLT-1 and GFP (green fluorescent protein), a control adenovirus AdRGDGFP encoding GFP alone, or PBS was delivered i.v. The therapeutic effect of sFLT-1 was evaluated by survival duration of the mice. Furthermore, the safety of i.v.- or i.p.-delivered adenovirus-mediated sFLT-1 was evaluated by administering AdRGDGFPsFLT-1, AdRGDGFP, or PBS either i.v. or i.p. into non-tumor-bearing mice. Adenovirus-mediated gene expression was determined by determining GFP expression using fluorescent microscopy and by assessing sFLT-1 expression in liver, lungs, spleen, and kidneys by immunohistochemistry using anti-FLT-1 monoclonal antibody. Systemic levels of sFLT-1 were evaluated by ELISA and the toxicity was evaluated by histopathology. RESULTS: The i.v. delivery of AdRGDGFPsFLT-1 in the ovarian tumor model resulted in a shorter duration of survival of the mice as compared with the control group. Furthermore, in the safety evaluation experiment, i.v. administration of AdRGDGFPsFLT-1 in non-tumor-bearing mice principally localized to the liver. This localization lead to sFLT-1 overexpression, mainly in the liver, resulting in hemorrhage and tissue toxicity. However, i.p. delivery of AdRGDGFPsFLT-1 did not localize principally to the liver, leading to negligible expression of sFLT-1, and no intrahepatic hemorrhage or toxicity was observed. The i.v. delivery of the control virus AdRGDGFP also principally localized to the liver, leading to GFP expression mainly in the liver. However, neither hemorrhage nor morphological cytotoxicity was observed. i.p. delivery of AdRGDGFP resulted in ectopic localization to the liver with very little GFP expression and no toxicity. These results suggest that overexpression of sFLT-1 in the liver as a result of i.v. delivery is hepatotoxic. CONCLUSIONS: Our results suggest that i.v. delivery of the sFLT-1 gene via replication-deficient, infectivity-enhanced recombinant adenoviral vectors will result in overexpression of sFLT-1 in the liver leading to unacceptable hepatotoxicity. Tumor-specific targeting of the vectors and tumor-specific expression strategies should be used to ensure a clinically useful antiangiogenesis gene therapy.  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