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   8078篇
  免费   618篇
  国内免费   13篇
耳鼻咽喉   130篇
儿科学   252篇
妇产科学   238篇
基础医学   1166篇
口腔科学   112篇
临床医学   849篇
内科学   1763篇
皮肤病学   111篇
神经病学   747篇
特种医学   192篇
外科学   914篇
综合类   135篇
一般理论   9篇
预防医学   808篇
眼科学   65篇
药学   523篇
中国医学   12篇
肿瘤学   683篇
  2023年   66篇
  2022年   71篇
  2021年   200篇
  2020年   116篇
  2019年   212篇
  2018年   248篇
  2017年   157篇
  2016年   178篇
  2015年   212篇
  2014年   270篇
  2013年   399篇
  2012年   574篇
  2011年   574篇
  2010年   314篇
  2009年   249篇
  2008年   416篇
  2007年   423篇
  2006年   405篇
  2005年   359篇
  2004年   336篇
  2003年   308篇
  2002年   300篇
  2001年   176篇
  2000年   174篇
  1999年   155篇
  1998年   75篇
  1997年   53篇
  1996年   54篇
  1995年   52篇
  1994年   60篇
  1993年   42篇
  1992年   117篇
  1991年   122篇
  1990年   94篇
  1989年   101篇
  1988年   103篇
  1987年   93篇
  1986年   93篇
  1985年   75篇
  1984年   51篇
  1983年   48篇
  1982年   34篇
  1981年   30篇
  1980年   32篇
  1979年   66篇
  1978年   50篇
  1976年   34篇
  1974年   32篇
  1970年   26篇
  1966年   26篇
排序方式: 共有8709条查询结果,搜索用时 15 毫秒
101.
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   
102.
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   
103.
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   
104.
105.
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   
106.
PURPOSE: To allow the longitudinal investigation of molecular events associated with the progression of human hepatocellular carcinoma (HCC), we sought to develop a murine model by orthotopic implantation of tumor fragments obtained from patients diagnosed at early stage. EXPERIMENTAL DESIGN: Tumor pieces (2 x 2 mm) were implanted on the liver surface of nu/nu mice. After xenograft growing, subsequent passages were performed to achieve long-term implant viability. Isolation of tumoral hepatocytes was done to establish new cell lines. HCC characteristics, proliferation rate, apoptotic index (terminal deoxynucleotidyl transferase-mediated nick end labeling), and expression of cell-cycle regulators (cyclins E and A, p21(Cip1), p27(Kip1), p16(INK4a), pRb, and p53) were assessed by Western Blot and immunohistochemistry, to correlate them with tumor progression. RESULTS: Five (50%) of the 10 primary HCCs resulted in small slow-growing liver implants. Three of them are viable after 48 months, whereas the remaining two survived for 15 and 13 months. Xenografts throughout passages exhibited a more aggressive phenotype with a poorer degree of differentiation, intense proliferation, moderate apoptosis, cell-cycle deregulation, p53 alterations, microvascular invasion, and dissemination. In one single passage, we observed critical growth delay, which was associated with significant p27(kip1) overexpression. We established the anchor-free growing BCLC-9 cell line from one xenograft. This has gains of chromosomes 7, 5p, 6q, and 9q, is hepatitis B virus-DNA positive, does not secrete alpha-fetoprotein, and has TP53 missense mutations in codons 192 and 242. CONCLUSIONS: The orthotopic implantation of early HCC fragments in nude mice provides a useful model to investigate the mechanisms of human HCC evolution and to establish new cell lines.  相似文献   
107.
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   
108.
PURPOSE: To evaluate the prognostic value of P-glycoprotein and clinicopathologic parameters in a large series of high-grade osteosarcoma (OS) patients treated at the Rizzoli Institute. PATIENTS AND METHODS: With the use of immunohistochemistry, P-glycoprotein was assessed in 149 patients with primary, nonmetastatic, high-grade OS who were homogeneously treated with chemotherapy protocols based on doxorubicin, high-dose methotrexate, and cisplatin and the addition of ifosfamide in the postoperative phase. RESULTS: P-glycoprotein positivity was found in 47 of 149 cases (32%) and was significantly associated with a higher incidence of relapse and a worse outcome, as was age younger than 12 years and tumor volume greater then 150 mL at diagnosis. Multivariate analysis further confirmed the prognostic value of these parameters, which all were independent adverse prognostic factors. Event-free survival and proportional hazards regression analyses confirmed that overexpression of P-glycoprotein at clinical onset is the most important adverse prognostic factor for high-grade OS patients treated with these chemotherapy protocols. CONCLUSION: Increased P-glycoprotein levels, together with tumor volume and age, should be taken into consideration to identify, at time of diagnosis, subgroups of OS patients with a higher risk of recurrence. This subgroup identification will constitute the basis for drawing individualized treatment protocols on the basis of risk evaluation, with the aim of using more aggressive chemotherapy, or combination chemotherapy with other adjuvants, only in those patients for which more aggressive regimens are strictly necessary and warranted.  相似文献   
109.
Hadler NM  Carey TS 《JAMA》2000,284(21):2780-2781
  相似文献   
110.
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