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   5414篇
  免费   145篇
  国内免费   1篇
  2021年   67篇
  2020年   45篇
  2019年   72篇
  2018年   122篇
  2017年   101篇
  2016年   133篇
  2015年   138篇
  2014年   185篇
  2013年   229篇
  2012年   246篇
  2011年   268篇
  2010年   145篇
  2009年   113篇
  2008年   168篇
  2007年   178篇
  2006年   173篇
  2005年   147篇
  2004年   153篇
  2003年   168篇
  2002年   141篇
  2001年   142篇
  2000年   105篇
  1999年   86篇
  1998年   51篇
  1992年   101篇
  1991年   70篇
  1990年   74篇
  1989年   99篇
  1988年   101篇
  1987年   77篇
  1986年   92篇
  1985年   86篇
  1984年   75篇
  1983年   58篇
  1980年   45篇
  1979年   93篇
  1978年   65篇
  1977年   64篇
  1976年   49篇
  1975年   53篇
  1974年   87篇
  1973年   100篇
  1972年   98篇
  1971年   97篇
  1970年   90篇
  1969年   74篇
  1968年   67篇
  1967年   61篇
  1966年   58篇
  1965年   42篇
排序方式: 共有5560条查询结果,搜索用时 15 毫秒
61.
62.
63.
Phosphoglucoisomerase (PGI), a soluble enzyme, and AChE, a membrane-bound enzyme were studied in transected peroneal nerves of dog and in isolated segments of these nerves. Although activities of both enzymes increased at the ends of transected nerves, marked differences in their behaviour were observed. The increment in AChE activity was much sharper than that of PGI and continued to grow with time whereas the increase in PGI developed fully within the initial hours after transection and did not change thereafter. In an isolated nerve segment AChE accumulated at both ends with a concomitant decrease in the middle part, whereas changes in PGI activity appeared only in the terminal parts, the rest of the nerve remaining at the normal level. The terminal increase of PGI did not, contrary to that of AChE, depend on the length of the isolated segment. The changes in PGI activity may be features of a local peritraumatic reaction whereas those of AChE indicate involvement of the whole segment along which the enzyme containing organelles are transported.  相似文献   
64.
Zusammenfassung Es wurden mit histochemischen Methoden Milchdrüsen von Meerschweinchen in physiologischer und durch Kastration während der Laktationsperiode hervorgerufener Involution untersucht. Nachgewiesen wurden alkalische und saure Phosphatase (APh und SPh), unspezifische Esterase, Sukzinodehydrase, SH-Gruppen, Nukleinsäuren und Lipide. — Die Aktivität der SPh nimmt während der Involution zu. Die Bedeutung dieses Enzyms für den Rückbildungsprozeß des Drüsengewebes wird diskutiert. — Das Vorkommen der APh-Aktivität in Drüsenendstücken im Involutionsstadium kann auf die Beteiligung dieses Enzyms an der Rückresorption der mit der Milch ausgeschiedenen Substanzen hinweisen. — Zwischen der Aktivität der unspezifischen Esterase und dem Gehalt sowie der Lokalisation von Lipiden besteht eine Abhängigkeit. — Es konnten keine Unterschiede in der Sukzinodehydraseaktivität und dem DNS-Gehalt aufgezeigt werden. — Die Verminderung von SH-Gruppen und RNS hängt mit dem Aufhören der Sekretionsproduktion durch die Zellen der Drüsenendstücke der Milchdrüsen zusammen.
Histochemical studies on the involution mechanism of the mammary gland
Summary Histochemical methods were used to study mammary glands of guinea pigs in the course of physiologic involution and that induced by castration during lactation. Alkaline and acid phosphatases, unspecific esterase, succinic dehydrogenase, SH groups, nucleic acids and lipids were determined. Acid phosphatase activity was found to be increased in mammary glands, subject to involution. The participation of the enzyme in the involutionary process of the gland tissue is discussed. The distribution of alkaline phosphatase in the secretory sections of the gland during involution would suggest the participation of the enzyme in the reabsorption of the substance secreted with milk. A correlation existing between the activity of unspecific esterase, the level and distribution of lipids in the mammary gland could be established. No differences were detected in the activity of succinic dehydrogenase and DNA level. A decrease in SH groups and RNA content is related to cessation of milk secretion.
  相似文献   
65.
66.
Summary Effect of LH, vinblastine and cytochalasin B on the cytoskeleton of cultured Leydig cells was investigated using monoclonal antibodies and fluorescence microscopy. After LH addition and treatment with cytoskeletal disrupting drugs, three main effects were observed: 1) increase of androgen level secreted by cultured mouse Leydig cells, 2) changes of cell-shape towards regular and rounded, 3) increase of 5,3-HSD activity. The results are discussed in respect to possible involvement of cytoskeleton in the regulation of steroidogenesis.  相似文献   
67.
Scintigraphic and gammagraphic (gamma-camera) techniques have been applied in diagnosing "hot" non-TSH dependent thyroid nodules. On the basis of frequent uneven accumulation of isotopic tracer observed in scintigraphic studies it was concluded that the structure of these nodules is heterogeneous. In some cases paradoxical patterns have been obtained following the dynamic tests of suppression and stimulation of the thyroid: after the administration of thyroid preparations paranodular thyroid tissue appears, while TSH administration causes an increase in the iodine uptake by the nodule. Ultrasonographic and gamma-camera studies have been carried out in 50 cases of "hot" autonomic thyroid nodules previously diagnosed by scintigraphy. Ultrasonographic studies revealed a weaker echogenicity in some cases and an intensified echo in the other. Sometimes by using this technique it was possible to demonstrate the occurrence of heterogeneous structures suggesting a cystic degeneration of the nodule. Paranodular thyroid tissue, invisible in scintigraphic scanning, could usually be observed by applying gamma-camera. It was concluded that both gamma camera and ultrasonographic studies confirm heterogeneous structure of intranodular tissue producing paradoxical patterns in scintigraphic scanning, with the latter technique usually aiding the detection of paranodular thyroid tissue without the necessity of application of the TSH test.  相似文献   
68.
Summary During cell division in antheridial filaments ofChara vulgaris an increase in DNA content occurs in both shield cells and manubria within an antheridium, reaching 16C–64C and 8C–32C levels, respectively. Endoreplication ceases prior to the formation of spermatids and initiation of spermiogenesis, probably as a result of symplasmic isolation of the antheridium from the thallus. As the DNA content of the nuclei increases, the shield cells3H-leucine incorporation increases, and they grow intensively in the tangential plane. Translation decreases considerably after termination of shield cell growth. DNA content of mature manubria is half of that in shield cells, although their size is 10 times that of manubria. Translational activity of manubria also increases as DNA content rises and cells grow. However, during spermiogenesis, this activity remains at its maximum, which is associated with the secretory function of the manubria. Spermiogenesis is also accompanied by far-reaching ultrastructural changes within the manubrial cytoplasm.The level of endopolyploidy in both shield cells and manubria of antheridia formed in the spring is higher by one replication cycle, than in autumnal antheridia. AMO-1618, at a concentration of 10–5M reduces the DNA content in the autumnal manubria. The higher the manubrial level of endopolyploidy in spermiogenesis, the greater their size, and the higher the translational activity and number of joined spermatids. The number of spermatozoids in the antheridium is also positively correlated with the internal volume of an antheridium, which is itself dependent on the endopolyploidy level of shield cells.The results obtained confirm the assumption that endoreplication favours the higher growth dynamics and potential translational activity, which occurs in the dynamic growth phase only in shield cells, while in manubria, i.e. cells producing substances necessary to spermatozoids development, it remains high until the end of spermiogenesis.  相似文献   
69.
The study involved 126 patients with cholelithiasis. Set of biochemical, radiological, endoscopic, and ultrasound examinations was carried out in these patients. Potential coincidence of clinical symptoms and causes of so-called postcholecystectomy syndrome was the purpose of a 1-year follow-up studies. The significance of the results are discussed.  相似文献   
70.
LTABP regimen was applied to 18 patients in IIB and IV stage of malignant lymphogranulomatosis resistant to MOPP. The obtained results were compared with historical control group of 18 patients with similar stage of the disease treated according to ABVD regimen. In both regimens courses were repeated every 28 days or more rarely, when leucopenia and thrombocytopenia prolonged. Only patients who had received at least 3 courses were analysed. In the LTABP group the complete remission was obtained in 10 cases (55%) while partial remission in 6 (33%). In the group treated with ABVD complete remission was obtained in 4 cases (22%) and partial in 9 cases (50%). In the LTABP group 11 patients are still alive and remain in complete remission, while in ABVD group--4 patients. The most frequent side effects in both groups included leucopenia, thrombocytopenia and symptoms of gastrointestinal intolerance. The LTABP regiment allows to obtain higher percentage of the complete remission than ABVD.  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