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   32341篇
  免费   4267篇
  国内免费   830篇
  2023年   138篇
  2022年   401篇
  2021年   752篇
  2020年   545篇
  2019年   662篇
  2018年   774篇
  2017年   680篇
  2016年   1015篇
  2015年   1382篇
  2014年   1523篇
  2013年   1668篇
  2012年   2000篇
  2011年   2082篇
  2010年   1291篇
  2009年   1158篇
  2008年   1436篇
  2007年   1434篇
  2006年   1253篇
  2005年   1127篇
  2004年   1088篇
  2003年   1043篇
  2002年   926篇
  2001年   2461篇
  2000年   2238篇
  1999年   1612篇
  1998年   585篇
  1997年   519篇
  1996年   462篇
  1995年   394篇
  1994年   301篇
  1993年   251篇
  1992年   762篇
  1991年   620篇
  1990年   539篇
  1989年   419篇
  1988年   315篇
  1987年   252篇
  1986年   191篇
  1985年   150篇
  1984年   108篇
  1983年   77篇
  1982年   56篇
  1981年   66篇
  1980年   42篇
  1979年   40篇
  1978年   38篇
  1977年   30篇
  1976年   37篇
  1973年   33篇
  1972年   29篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
Liu  Jin Yue  Sheng  Ze Wen  Hu  Yu Qi  Liu  Qi  Qiang  Sheng  Song  Xiao Ling  Liu  Biao 《Transgenic research》2021,30(1):105-119
Transgenic Research - The releasing of transgenic soybeans (Glycine max (L.) Merr.) into farming systems raises concerns that transgenes might escape from the soybeans via pollen into...  相似文献   
962.
IntroductionPediatric patients with cardiomyopathies are at risk for sudden death and may need implantable cardioverter defibrillators (ICD’s), but given their small size and duration of use, children are at increased risk for complications associated with ICD use. The subcutaneous ICD presents a favorable option for children without pacing indications. Unfortunately, initial pediatric studies have demonstrated a high complication rate, likely due to the 3-incision technique employed.Material and methodsPatients with ICD but no pacing indication were retrospectively reviewed after implantation of subcutaneous ICD via the two-incision technique. In half of the patients, 10-J impedance test was also performed to compare with impedance obtained after defibrillation threshold testing with 65-J.ResultsTwelve patients were included. The median age was 14 years (range 10–16 years) with eight males included (72.7%). The median weight was 55 kg (range 29 kg–75.1 kg). Follow-up had a median of 11.5 months (range 2–27 months). The median body mass index was 18.4 kg/m squared (range 15.5–27.9 kg/m squared). One patient suffered a minor complication after tearing off the incisional adhesive strips early and required a non-invasive repair in clinic. Shock impedance had a median of 55 J (range 48–68 J). There was one appropriate shock/charge and no inappropriate shocks during follow-up.ConclusionThe two-incision, intermuscular technique appears to have a lower acute complication rate than prior reports, in our cohort of 12 pediatric patients.  相似文献   
963.
Zhao  X.  Chen  L.  Ren  Q.  Wu  Z.  Fang  S.  Jiang  Y.  Chen  Y.  Zhong  Y.  Wang  D.  Wu  J.  Zhang  G. 《Applied Biochemistry and Microbiology》2021,57(3):344-350
Applied Biochemistry and Microbiology - A pyridine-transforming strain P2 was isolated from sewage collected from Guangzhou oil stain field(China).According to the system analysis, it was...  相似文献   
964.
Large sample theory of semiparametric models based on maximum likelihood estimation (MLE) with shape constraint on the nonparametric component is well studied. Relatively less attention has been paid to the computational aspect of semiparametric MLE. The computation of semiparametric MLE based on existing approaches such as the expectation‐maximization (EM) algorithm can be computationally prohibitive when the missing rate is high. In this paper, we propose a computational framework for semiparametric MLE based on an inexact block coordinate ascent (BCA) algorithm. We show theoretically that the proposed algorithm converges. This computational framework can be applied to a wide range of data with different structures, such as panel count data, interval‐censored data, and degradation data, among others. Simulation studies demonstrate favorable performance compared with existing algorithms in terms of accuracy and speed. Two data sets are used to illustrate the proposed computational method. We further implement the proposed computational method in R package BCA1SG , available at CRAN.  相似文献   
965.
966.
967.
968.
969.
970.
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