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   4850篇
  免费   183篇
  国内免费   1篇
  5034篇
  2023年   15篇
  2022年   14篇
  2021年   35篇
  2020年   17篇
  2019年   31篇
  2018年   83篇
  2017年   79篇
  2016年   97篇
  2015年   74篇
  2014年   109篇
  2013年   195篇
  2012年   421篇
  2011年   627篇
  2010年   276篇
  2009年   72篇
  2008年   416篇
  2007年   390篇
  2006年   332篇
  2005年   305篇
  2004年   232篇
  2003年   231篇
  2002年   171篇
  2001年   67篇
  2000年   146篇
  1999年   75篇
  1998年   47篇
  1997年   13篇
  1996年   12篇
  1995年   16篇
  1994年   9篇
  1993年   10篇
  1992年   20篇
  1991年   14篇
  1990年   11篇
  1989年   12篇
  1987年   17篇
  1985年   19篇
  1984年   22篇
  1982年   16篇
  1981年   9篇
  1980年   17篇
  1979年   14篇
  1978年   14篇
  1977年   9篇
  1976年   17篇
  1975年   13篇
  1974年   18篇
  1973年   9篇
  1971年   10篇
  1967年   8篇
排序方式: 共有5034条查询结果,搜索用时 15 毫秒
1.
The level of urine selenium in healthy adult population, 230 persons, was examined. Persons were selected regarding sex, ages, and smoking habits. No differences versus these observations have been found. For a total, group values are 16.96 Se nmol/creatinine mmol, SD=5.44. It is possible from a single-void specimen to express daily excretion of selenium.  相似文献   
2.
3.
A?koliv na zá kladě mnoha pokus? se p? edpokládalo, ?e tzv. bÍlkovinná v?etena v buňkách tzn. buně?né inkluse X-viru kaktus? (Ca XV), jsou slo?ena z ?etních prodlou?ených ?ásti Ca XV, p?esto to dosud nebylo proká zá no. Proto jsme se pokusili pomocÍ fluoreskujÍcÍch protilátek doká ?at, ?e bilkovinná v?etena jsou skute?ně agregáty virových ?ástic. V těto práci jsme pouzili tzv. nep?Ímé metody. Nejprve jsme p? sobili na buňky obsahujÍci tato v?etena homologiokým antisé rem proti Ca XV, zÍskanym imunizacÍ králÍk? a teprve potom jsme buňky vlo?ili do roztoku fluoreskujicÍch protilátek proti králicimu γglobulinu. BÍlkovinná v?etena svitila potom ve fluorescen?nÍm mikroskopu silně ?lutozeleně (bylopou?ito fluoresceinisothiocyaná tu). Tato fluorescence ná m uká zala, ?e nastala pozitivnÍ reakce a ?e bÍlkovianá v?etena jsou slo?ena z virových ?ástic. ?etné kontrolnÍ pokusy potvrdily ná? základnÍ pokus.  相似文献   
4.
5.
The influence of external sodium concentration on potassium (depolarizing agent)-stimulated calcium uptake and Ca+-dependent acetylcholine release by rat cerebral cortex synaptosomes has been studied. It was found that increased sodium concentration decreases both the Ca2+ uptake and the acetylcholine release, whereas a low external sodium concentration is stimulatory.  相似文献   
6.
The effect of sucrose on fruiting, seed production, and seed germination of lesser centaury [Centaurium pulchellum (Sw.) Druce] was examined using explants of flowers and flower buds. Sucrose concentrations in the culture medium ranged from 0.003 to 0.3 M. It has been shown that the number of auxiliary buds, capsules dimension, number of viable seeds per capsule and seed dimensions increased with the increase of sucrose concentrations. The highest values were recorded at sucrose concentrations higher than 0.03 M, except for seeds size, which were larger at sucrose concentration ranging from 0.003 to 0.1 M. The germination of in vitro produced seeds was affected by previous culture history: a higher germination percentage was obtained in seeds that were raised from explants originally grown on medium with sucrose concentrations higher than 0.003 M.  相似文献   
7.
Horse chestnut (Aesculus hyppocastanum L., Hyppocastanacea) is a relict species with a slow and complex reproductive cycle considered to have horticultural and medical importance. The cycle maybe circumvented via in vitro androgenesis. Androgenesis of horse chestnut was induced in microspores and anther culture on MS media. Some of the horse chestnut androgenic embryos were albinos. Addition of abscisic acid in media (in concentrations of 0.01, 0.1, 0.5, 1, 2, 5, 10, and 20 mg l?1) with horse chestnut androgenic embryos has circumvented the reproduction cycle barriers. The best results were achieved on medium with the lowest abscisic acid concentration (0.01 mg l?1) in microspore culture. The microspore culture proved to be a better model system for embryo production and albino embryo reduction than anther culture. Flow cytometry analysis after maturation treatments induced by ABA showed that 88 % of green embryos originating from microspore culture were haploid. However, 50 % of green embryos from anther culture were haploid. The remaining analyzed androgenic embryos, from both types of cultures were diploid.  相似文献   
8.
Ohne ZusammenfassungDie vorliegenden Versuehe wurden während meines kurzen Aufenthalts im Pflanzenphysiologisehen Institut der Universität Wien ausgeführt. Herrn Prof. Dr. Karl Höfler und Herrn Dr. H. Kinzel danke ich sehönstens auch an dieser Stelle für die Untersfützung während der Arbeit.  相似文献   
9.
10.
Losses of proteolytic peptides during extraction and/or purification procedures succeeding in-gel or in-solution digests of proteins frequently occur in the course of protein identification investigations. In order to overcome this disadvantage, the method of in-capillary digest was developed: native proteins were incubated in the presence of endoproteases in the electrospray capillary and the resulting peptides were analyzed by nanoelectrospray-mass spectrometry during the ongoing proteolysis. In-capillary digest of apomyglobin by use of trypsin in a molar ratio of 25:1 yielded complete degradation already after 15 min. The sequence coverage based on formation of molecular ions was 100% and peptide ions could be fragmented by collision-induced dissociation and sequenced. When myoglobin was incubated in the electrospray capillary with trypsin in a molar ratio of 500:1, a clear shift from molecular ions and miscleaved peptide ions to the expected final tryptic peptide ions was observed over a 2 h period. The peptide spectra obtained from tryptic in-capillary proteolysis of bovine serum albumin and apotransferrin, respectively, gave rise to sequence coverages of more than 40% for both proteins. The data obtained from the peptide maps as well as from collision-induced dissociation (CID) of selected peptides were more than sufficient for protein identification by database searches. An elephant milk protein preparation was used to demonstrate the application of in-capillary proteolysis on protein mixtures. Tryptic digest, simultaneous analysis of the proteolytic peptides by use of CID, and subsequent sequencing allowed the identification of lactoferrin, alphas1-casein, beta-casein, delta-casein, and kappa-casein by homology search.  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