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   6315篇
  免费   521篇
  国内免费   2篇
  6838篇
  2022年   46篇
  2021年   71篇
  2020年   36篇
  2019年   69篇
  2018年   62篇
  2017年   85篇
  2016年   145篇
  2015年   198篇
  2014年   246篇
  2013年   369篇
  2012年   395篇
  2011年   402篇
  2010年   283篇
  2009年   299篇
  2008年   396篇
  2007年   411篇
  2006年   396篇
  2005年   387篇
  2004年   390篇
  2003年   412篇
  2002年   385篇
  2001年   76篇
  2000年   54篇
  1999年   87篇
  1998年   130篇
  1997年   86篇
  1996年   75篇
  1995年   85篇
  1994年   65篇
  1993年   57篇
  1992年   69篇
  1991年   53篇
  1990年   41篇
  1989年   35篇
  1988年   35篇
  1987年   22篇
  1986年   22篇
  1985年   28篇
  1984年   37篇
  1983年   16篇
  1982年   32篇
  1981年   28篇
  1980年   33篇
  1979年   30篇
  1978年   20篇
  1977年   20篇
  1976年   19篇
  1975年   18篇
  1974年   15篇
  1972年   15篇
排序方式: 共有6838条查询结果,搜索用时 0 毫秒
11.
Summary To delimit the 14q32.1 recurrent breakpoint of ataxia telangiectasia clones, we performed an in situ hybridization study with various probes located on the 14q32 band. We thus mapped this breakpoint between the D14S1 and Pi loci. Furthermore, an interstitial duplication including D14S1 and a part of the IgH locus was demonstrated on a t(14;14) clone.  相似文献   
12.
Information concerning the cellular localization of dopamine receptor subtypes in the nucleus accumbens (NAcc) was obtained using receptor autoradiographic analysis. Unilateral, stereotaxic injection of the axon-sparing neurotoxin, quinolinic acid, into the NAcc resulted in a prominent loss of dopamine D1 receptors (as labeled by [3H]SCH 23390). Contrarily, no appreciable decrement in D2 receptors (labeled by [3H]raclopride) could be identified within the same region of the NAcc. The findings support the view that accumbens D1 receptors are located postsynaptically on neurons or their processes, while D2 receptors within this nucleus are primarily located on afferent terminals.  相似文献   
13.
In order to assess the relative effectiveness of finger warming and temporal blood volume pulse reduction biofeedback in the treatment of migraine, 22 female migraine patients were assigned to one of three experimental conditions: temporal artery constriction feedback, finger temperature feedback, or waiting list. Biofeedback training consisted of 12 sessions over a 6-week period. All patients completed 5 weeks of daily self-monitoring of headache activity (frequency, duration, and intensity) and medication before and after treatment. Treatment credibility was assessed at the end of Sessions 1, 6, and 12. Results showed that temporal constriction and finger temperature biofeedback were equally effective in controlling migraine headaches and produced greater benefits than the waiting list condition. Power analyses indicated that very large sample sizes would have been required to detect any significant differences between the two treatment groups. No significant relationships were found between levels of therapeutic gains and levels of thermal or blood volume pulse self-regulation skills. Likewise, treatment outcome was not found to be related to treatment credibility. Further analyses revealed that changes in headache activity and medication were associated with changes in vasomotor variability. Because blood volume pulse variability was not significantly affected by biofeedback training, questions about its role in the therapeutic mechanism are raised.This research was supported in part by grants from the Quebec Ministry of Education and the Quebec Ministery of Social Affairs to the first author, and an award from the Medical Research Council of Canada to the second author. The authors are indebted to Drs. Frank Andrasik, Howard Barbaree, Edward Blanchard, Martin Ford, and Patrick McGrath, as well as to two anonymous reviewers, for their helpful comments on an earlier draft of this paper.  相似文献   
14.
Summary Calcium alginate gel-entrapped cells ofCatharanthus roseus were used to study the production of indole alkaloids in a flow through process. The bioreactor was functional for more than two months and product recovery was analyzed under various operating conditions.  相似文献   
15.
Virchows Archiv B Cell Pathology - Various parameters of the local cellular response have been studied in 16 laryngeal papillomas from ten patients with recurrent papillomas as well as normal...  相似文献   
16.
17.
18.
Summary The staining properties of AT-specific dyes Hoechst 33342 and DAPI as revealed by Hoechst 33342/mithramycin and mithramycin/DAPI bivariate human flow karyotype patterns are different for chromosomes rich in heterochromatin. The peak corresponding to chromosome Y of a given cell line is higher on the A/T axis with mithramycin/DAPI staining than with mithramycin/Hoechst. The chromosome 1 was found slightly more fluorescent in mithramycin/DAPI than in mithramycin/Hoechst as judged by the slight displacement of its area on the Hoechst-DAPI axis. The other peaks did not show major differences. On the same flow karyotypes, chromosomal rearrangements were detected.  相似文献   
19.
Redescripción de Proteocephalus paraguayensis (Rudin, 1917) (Cestoda: Proteocephalidae), parásito de Hydrodynastes gigas (Dum., Bibr. & Dum., 1854) de Paraguay. Se describe esta especie notable, considerada por Freze (1965) como species inquirenda. Si comparamos esta especie con otras especies de Proteocephalidea, veremos que ella presenta caracteres anatomo-morfológicos propios. Esta especie se caracteriza por: vitelógenos de posición dorsal, adosados a la musculatura interna longitudinal, desbordando en parte sobre el córtex y la médula; formación particular del útero; posición cortical del tronco uterino y medular de los divertículos uterinos; esfínter vaginal proximal; cirro muy alargado; glándula de Mehlis muy desarrollada. Consideramos P. paraguayensis como una especie válida y presumimos que el huesped-tipo es Hydrodynastes gigas (Dum., Bibr. & Dum., 1854). A pesar de las características que posee P. paraguayensis, pensamos que no es oportuno clasificar esta especie en un nuevo género monotípico. Proteocephalus paraguayensis, considered by Freze (1965) as a species inquirenda, is redescribed and figured. When compared with other members of the Proteocephalidea, the species shows the following morpho-anatomical characters: the vitelline follicles in a dorsal position, attached to the internal longitudinal musculature and extending into both the cortex and medulla; a characteristic formation of the uterus; the uterine stem in a cortical position and uterine branches in a medullary position; a proximal vaginal sphincter; a very elongate cirrus; and very large Mehlis' glands. The specific status of Proteocephalus paraguayensis is confirmed. Our specimens were taken from Hydrodynastes gigas (the host according to Rudin was Coluber sp.). Even though the species differs significantly from other proteocephalideans, its systematic and phylogenetic position is not yet clearly demonstrated, and it is decided to refrain from attributing it to a new genus.  相似文献   
20.
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