全文获取类型
收费全文 | 2339篇 |
免费 | 135篇 |
国内免费 | 1篇 |
出版年
2024年 | 7篇 |
2023年 | 36篇 |
2022年 | 80篇 |
2021年 | 122篇 |
2020年 | 52篇 |
2019年 | 60篇 |
2018年 | 88篇 |
2017年 | 65篇 |
2016年 | 104篇 |
2015年 | 111篇 |
2014年 | 116篇 |
2013年 | 167篇 |
2012年 | 159篇 |
2011年 | 159篇 |
2010年 | 96篇 |
2009年 | 83篇 |
2008年 | 102篇 |
2007年 | 94篇 |
2006年 | 88篇 |
2005年 | 75篇 |
2004年 | 84篇 |
2003年 | 65篇 |
2002年 | 58篇 |
2001年 | 41篇 |
2000年 | 30篇 |
1999年 | 18篇 |
1998年 | 20篇 |
1997年 | 16篇 |
1996年 | 9篇 |
1995年 | 15篇 |
1994年 | 8篇 |
1993年 | 12篇 |
1992年 | 15篇 |
1991年 | 16篇 |
1990年 | 8篇 |
1989年 | 7篇 |
1988年 | 13篇 |
1986年 | 11篇 |
1985年 | 14篇 |
1984年 | 9篇 |
1981年 | 9篇 |
1980年 | 9篇 |
1979年 | 9篇 |
1978年 | 12篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1974年 | 9篇 |
1973年 | 10篇 |
1969年 | 9篇 |
1968年 | 6篇 |
排序方式: 共有2475条查询结果,搜索用时 15 毫秒
991.
Serge Braun Valerie Askanas W. King Engel Emad N. Ibrahim 《Journal of neurochemistry》1993,60(5):1929-1935
Abstract: We have studied the effect of long-term treatment with hydrocortisone on the expression of acetylcholine receptors (AChRs) at the neuromuscular junctions of human muscle cultured in monolayer and innervated de novo by fetal rat spinal cord motoneurons. Hydrocortisone increased accumulation of junctional AChRs in a dose-and time-dependent fashion. This increase was due to both decreased degradation and increased synthesis of AChRs. Other glucocorticoids, dexamethasone and prednisolone, exerted similar effects. Our study demonstrates a novel action of glucocorticoids on human junctional AChRs. 相似文献
992.
T. M. Butt N. L. Carreck L. Ibrahim I. H. Williams 《Biocontrol Science and Technology》1998,8(4):533-538
Pollen beetles (Meligethes aeneus) are pests that feed and oviposit in the buds and flowers of oilseed rape. Honey-bees foraging from a hive fitted with an inoculum dispenser at the entrance effectively delivered dry conidia of the entomogenous fungus, Metarhizium anisopliae , to the flowers of oilseed rape in caged field plots. In both winter- and spring-sown rape experiments, a greater mortality of pollen beetles occurred in treated plots than in control plots. The mortality (61% on winter rape, 100% on spring rape) was greatest during peak flowering, when the feeding activity of both bees and beetles from the flowers was maximal, providing optimal conditions for inoculum dissemination and infection. Conidial sporulation occurred on a significant proportion of the dead pollen beetles. There was no evidence of any adverse effect on the honey-bee colonies. 相似文献
993.
Pre- or post-treatment of duodenal discs with mannose, N-acetylglucosamine or chitin soluble extracts (CSE) prevented the adherence of Candida albicans to gastrointestinal tract. CSE was the most effective in blocking the adherence of C. albicans. Treatment of infant mice with saccharides significantly reduced the systemic spread of C. albicans inoculated into the gut. The best protection was obtained when the saccharides were given 2 days prior to the infection and continued over the course of the infection. However, systemic spread was reduced with a single dose of saccharide 30 min before infection. The saccharides may bind to the gastrointestinal mucosa and block the attachment of C. albicans. 相似文献
994.
The cricothyroid muscle in dogs received branches from two independent nerves, namely the external ramus of the cranial laryngeal nerve and the pharyngeal branch of the vagus. Classical spindles are infrequent in the muscle. Atypical forms of sensory endings were identified. Two end-plates were frequently met with on a single extrafusal fibre. Sectioning of the external ramus of the cranial laryngeal nerve was followed by degeneration of spindles. Intact axons detected up to 6 months after operation are probably derived from the pharyngeal branch of the vagus. Chromatolytic changes occurred in the ipsilateral dorsal vagal nucleus and the capsulated ganglion at the entry of the nerve into the muscle. Chromatolysis occurred in the intramuscular ganglion cell rows and in neurons of the ipsilateral nodose ganglion. Morphological alterations were more pronounced in the ipsilateral medial column of the nucleus ambiguus. No changes were observed in the somata of the mesencephalic nucleus. 相似文献
995.
Determination of staphylococcal enterotoxin A in cheddar cheese produced without starter activity. 总被引:2,自引:0,他引:2 下载免费PDF全文
Three variants of the chloramine-T radioiodination method were used to iodinate staphylococcal enterotoxin A with 125I. Only one method consistently produced usable labels for radioimmunoassay. The iodine incorporation was 55 to 76%; the specific activity was 3.5 to 5.5 muCi/microgram of enterotoxin, and the label was extremely stable on storage at -20 degrees C. Determinations of the enterotoxin in extracts of cheddar cheese produced without starter activity were carried out with the radioimmunoassay system and protein A as antibody immunoadsorbent. The assay buffer used in this system significantly influenced the detected levels of enterotoxin in the cheese extracts. Phosphate buffer, but not tris(hydroxymethyl)aminomethane (Tris) buffer, caused gelling of cheese extract proteins, thus resulting in an incomplete separation of free from antibody-bound 125I enterotoxin. When Tris buffer was used, the results indicated a high degree of accuracy and precision for this radioimmunoassay. The lowest detectable enterotoxin concentration in cheese extract was 0.5 ng/ml. 相似文献
996.
Ragai K. Ibrahim 《Phytochemistry》1980,19(11):2459-2460
A partially purified UDP-glucose: o-dihydroxycoumarin glucosyltransferase from tobacco cell culture required an intact coumarin ring system with o-dihydroxy groups for highest activity. The enzyme exhibited strict position specificity towards the 7-OH group of both esculetin and daphnetin with the formation of cichoriin and daphnin, respectively. The apparent Km values were 111 and 95 μM, while the Vmax for esculetin was 26.4 pkat/mg protein. 相似文献
997.
Ahmet Gul Halil Aslan Ibrahim Polat Altan Cebeci Hasan Bulut Ozturk Sahin Yavuz Ceylan 《Twin research》2003,6(4):263-266
The natural history of 11 cases of twin-twin transfusion syndrome (TTTS) in monochorionic diamniotic (MCDA) twin pregnancies has been reviewed. Seven cases before 28 weeks and four pregnancies after 28 weeks had been followed up without intervention. Eight cases had premature uterine contractions. All seven pregnancies before 28 weeks aborted, leading to a 100% mortality rate. After 28 weeks all mothers delivered live births. The diagnosis of TTTS before 28 weeks, and with premature uterine contraction, seems to be a poor prognostic sign. 相似文献
998.
Pulse-labeling experiments of white lupin (Lupinus albus L.) cell cultures with [U-14C]l-phenylalanine for 72 h resulted in the incorporation of the radioactivity into the isoflavone aglucones, glucosides, and prenylated derivatives. Both the aglucones genistein and 2′-hydroxygenistein and their 7-O-glucosides accounted for 85% of the total isoflavonoids identified in the cultured cells and contained 35% of the radioactivity, whereas the prenylated derivatives comprised 15 and 65%, respectively. Almost 20% of the labeled isoflavones of the cellular pool was recovered from the culture medium, 90% of which were monoprenylated and diprenylated derivatives containing 80% of the radioactivity. These results clearly demonstrate the release into the culture medium of a substantial amount of the endogenously synthesized isoflavonoids, especially the prenylated derivatives. 相似文献
999.