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   61512篇
  免费   6039篇
  国内免费   1330篇
耳鼻咽喉   516篇
儿科学   1345篇
妇产科学   1647篇
基础医学   5129篇
口腔科学   1366篇
临床医学   5745篇
内科学   9578篇
皮肤病学   440篇
神经病学   2420篇
特种医学   1926篇
外国民族医学   25篇
外科学   7446篇
综合类   7848篇
现状与发展   4篇
预防医学   8123篇
眼科学   430篇
药学   5298篇
  107篇
中国医学   1867篇
肿瘤学   7621篇
  2024年   145篇
  2023年   1147篇
  2022年   2049篇
  2021年   2937篇
  2020年   2765篇
  2019年   2518篇
  2018年   2523篇
  2017年   2386篇
  2016年   2381篇
  2015年   2485篇
  2014年   4255篇
  2013年   4331篇
  2012年   3613篇
  2011年   3803篇
  2010年   2873篇
  2009年   2744篇
  2008年   2787篇
  2007年   2771篇
  2006年   2264篇
  2005年   2037篇
  2004年   1808篇
  2003年   1510篇
  2002年   1347篇
  2001年   1135篇
  2000年   1006篇
  1999年   927篇
  1998年   782篇
  1997年   776篇
  1996年   701篇
  1995年   595篇
  1994年   589篇
  1993年   442篇
  1992年   468篇
  1991年   426篇
  1990年   354篇
  1989年   337篇
  1988年   308篇
  1987年   247篇
  1986年   235篇
  1985年   291篇
  1984年   253篇
  1983年   166篇
  1982年   209篇
  1981年   181篇
  1980年   166篇
  1979年   145篇
  1978年   112篇
  1977年   100篇
  1976年   95篇
  1975年   94篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Mycophenolate mofetil (MMF) used in a triple-drug regimen has been shown to decrease acute rejection rates, compared to a double-drug regimen. The impact of MMF on late acute rejection (LAR) episodes has not been well described. To investigate the risk of LAR (rejection > or = 6 months post-transplantation) data from the Scientific Registry of Transplant Recipients (SRTR) were used. We studied adult primary liver transplant recipients transplanted between June 1, 1995, and April 30, 2004, with hepatitis C virus (HCV) (n = 3356), hepatitis B virus (HBV) (n = 550) or a nonviral (n = 5740) primary cause of liver disease who were recorded as receiving continuous 3-(MMF + Tacro + steroids) versus 2-drug (Tacro + steroids) therapy for at least 6 months immediately post transplantation. Kaplan-Meier analysis showed significantly lower LAR rates 4 years post-transplant in 3- versus 2-drug HCV, HBV and nonviral disease patients. Multivariate regression confirmed 3- versus 2-drug therapy to be associated with a decreased risk of LAR. Late graft survival was significantly lower at 4 years post-transplant for patients with LAR 6-12 months post-transplantation versus patients with early rejection (78.0% vs. 87.0%, p < 0.001) and no rejection (88.1%, p < 0.001). Three-drug versus 2-drug therapy for a minimum of 6 months may offer a better treatment strategy to avoid the consequences and expense of LAR episodes.  相似文献   
42.
The incidence of uterine cervical cancer has increased slightly in Western countries, with an increase in relatively young women. Overexpression of matrix metalloproteinases (MMPs)-2 and -9 has turned out as a prognostic factor in many cancers. We compared the expression of the proteins MMP-2 and MMP-9 in cervical primary tumors with clinical outcome and risk factors of cervical cancer. One hundred sixty-one patients with cervical cancer treated in Ume? University Hospital or Sahlgrenska University Hospital, Sweden, between 1991 and 1995 were included in the study. Paraffin-embedded tissue samples obtained prior to treatment were examined immunohistochemically by specific antibodies for MMP-2 and MMP-9. Forty-two percent of the tumors were intensively positive for MMP-2 and 31% for MMP-9. Nineteen percent of the samples were intensively positive for both proteinases and 47% negative or weak for both. Overexpression of MMP-2 seemed to predict unfavorable survival under Kaplan-Meier analysis and in the multivariate analysis. Early sexual activity and low parity seemed to correlate to overexpression of MMP-2. MMP-9 was not associated with survival or sexual behavior. Intensive MMP-9 was noted in grade 1 tumors. We conclude that MMP-2 and MMP-9 have different roles in uterine cervical cancer. MMP-2 could be associated with aggressive behavior, but MMP-9 expression diminishes in high-grade tumors.  相似文献   
43.
带手套穿刺对留置套管针一次成功率的影响   总被引:1,自引:0,他引:1  
张昆 《护理研究》2002,16(5):259-260
为探讨戴手套与不戴手套穿刺对留置静脉套管针一次成功率的影响 ,为护理人员的自身防护提供科学依据 ,选取冠状动脉搭桥术病人 12 0例 ,随机分为实验组和对照组 ,实验组采用戴手套穿刺法 ,对照组采用常规洗手后不戴手套穿刺法。结果两组一次穿刺成功率经χ2 检验 ,无统计学意义( χ2 =0 .5 6 3,P >0 .0 5 )。说明戴手套留置套管针并不影响一次穿刺成功率。  相似文献   
44.
45.
作者用自制的[~(125)I]标记激素,参考国外经验,建立了人血清胰岛素抗体、猪胰岛素原抗体和胰多肽抗体等三种放射免疫检测法,并对方法的主要实验条件进行了优选,对方法的质量控制参数作了验证。结果发现:在使用国产胰岛素的糖尿病人血清中,三种抗体的检出率分别为90.8%、48.3%和36.5%;抗体特异性结合值分别为21.2±17.4%、41.8±27.4%和25.6±28.4;而正常人和糖尿病人未用胰岛素者全部为阴性,显示国产胰岛素具有明显的免疫原性。  相似文献   
46.
A design technique (Control of Uncertain Systems with Bounded Inputs, Tarbouriech S, Garcia G, (Eds), Lecture Notes in Control and Information Sciences, vol. 227 , Springer: Berlin, 1997; 173–186) recently proposed for stabilization of a linear system with rate‐limited actuators is utilized to design feedback laws that cause the system output to track a desired command signal. This design technique combines two design techniques recently developed for linear systems with position limited actuators, piecewise‐linear LQ control (Automatica, 1994; 30 : 403–416) and low‐and‐high gain feedback (IEEE Trans. Automat. Control, 1996; 41 : 368–378), and hence takes advantage of both design techniques, while avoiding their disadvantages. In the case that only the output is available for feedback, the performance of the state feedback law is preserved by the use of a fast observer. An open‐loop exponentially unstable fighter aircraft is used to demonstrate the effectiveness of the proposed control design method. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   
47.
目的探讨肥胖患者下腹部手术采用Joel—Cohen切口对预防非感染性切口裂开的临床效果。方法选择切口部位皮下脂肪层厚达4—5cm的妇产科手术患者90例,随机分为观察组44例,采用Joel—Cohen切口;对照组46例,采用下腹正中直切口。观察切口愈合和脂肪液化情况。结果观察组切口甲级愈合率显著高于对照组(P〈0.01);脂肪液化切口裂开率显著低于对照组(P〈0.05)。结论脂肪组织厚达4—5cm以上下腹部手术切口,采用Joel—Cohen切口可以减少脂肪液化,切口愈合显著优于下腹直切口,值得临床推广应用。  相似文献   
48.
For several genetic diseases two biological phenomena have been recognised as important: germline mosaicism; and different new mutation rates in males and females depending on mutation type. Both principles have been investigated separately and their influence on risk estimation in families has been exemplified in the literature. The aim of this paper is to present a general model that includes mosaicism and different new mutation rates. Mosaicism is introduced by defining additional alleles at the disease locus in combination with adapted segregation rules. Taking Duchenne muscular dystrophy as an example, we derive the conditions which have to be fulfilled for a population in mutation selection equilibrium. Our approach describes the model at the population level and not in individual subjects. This has the advantage of being able to use well known algorithms for the calculation of likelihoods in pedigrees, and to include additional diagnostic information such as marker genotypes and carrier deletion test results. We demonstrate the impact of the new model on a typical pedigree. In families where the patient is not available, the distinction between point mutations and deletions is important, since often molecular diagnostic tests for females can only screen for deletions. Negative deletion test results can now be included in the risk calculations.  相似文献   
49.
目的探讨第一产程胎心监护异常的相关因素,提示处理措施。方法2004年1月1日。12月31日对我院226例第一产程胎心监护异常的相关因素进行回顾性分析。结果第一产程胎心监护异常为综合因素所致,胎儿高危因素为91.59%,母体高危因素为65.49%,产程处理因素为42.92%。结论第一产程胎心监护异常主要与胎儿因素、母体因素有关,提高产前检查质量、加强产程监护、正确选择分娩方式极为重要。  相似文献   
50.
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