全文获取类型
收费全文 | 567029篇 |
免费 | 59170篇 |
国内免费 | 213篇 |
专业分类
626412篇 |
出版年
2016年 | 6884篇 |
2015年 | 8563篇 |
2014年 | 10389篇 |
2013年 | 14461篇 |
2012年 | 16470篇 |
2011年 | 17229篇 |
2010年 | 11864篇 |
2009年 | 10992篇 |
2008年 | 15737篇 |
2007年 | 16463篇 |
2006年 | 15460篇 |
2005年 | 14754篇 |
2004年 | 14887篇 |
2003年 | 14121篇 |
2002年 | 13935篇 |
2001年 | 23723篇 |
2000年 | 23985篇 |
1999年 | 18712篇 |
1998年 | 6638篇 |
1997年 | 6895篇 |
1996年 | 6360篇 |
1995年 | 6016篇 |
1994年 | 5771篇 |
1993年 | 5909篇 |
1992年 | 15717篇 |
1991年 | 15732篇 |
1990年 | 15278篇 |
1989年 | 14929篇 |
1988年 | 14213篇 |
1987年 | 13612篇 |
1986年 | 12599篇 |
1985年 | 12628篇 |
1984年 | 10486篇 |
1983年 | 9067篇 |
1982年 | 6764篇 |
1981年 | 6068篇 |
1980年 | 5873篇 |
1979年 | 10030篇 |
1978年 | 7962篇 |
1977年 | 7274篇 |
1976年 | 6912篇 |
1975年 | 7714篇 |
1974年 | 8665篇 |
1973年 | 8469篇 |
1972年 | 7954篇 |
1971年 | 7285篇 |
1970年 | 6433篇 |
1969年 | 6243篇 |
1968年 | 5999篇 |
1967年 | 5228篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
I E Ganelina L M Kukui J P Nikolaewa T E Schumilowa W E Cholmogorow K W Timofeew A L Schurigin 《Folia haematologica (Leipzig, Germany : 1928)》1982,109(3):470-482
We observed 70 male patients with a seriously proceeding Chronic myocardial ischemia. They were hospitalised because of frequent, permanent and serious attacks of stenocardia at rest and in stress situations. More than 2/3 of these patients had suffered from a myocardial infarct. In the course of two weeks an intensive therapy with all modern preparations for vasodilatation was made. This therapy proved to be unsuccessful. Nearly all patients were administered more than 10 tables of nitroglycerin per day and, in addition, they were injected analgetics as a compensation of attack. The ultraviolet own blood irradiation (UVB) had a positive therapeutic effect in all patients. There was a good success in 46 patients, in all patients satisfactory results could be registered. The effect of therapy was evident by the decrease of administration of nitroglycerin required, by an increase in the degree of stress capacity, and by an easier treatment of stenocardia attacks. The observation time for patients amounted to 2-8 months. The success of therapy remained in 38 patients. After this time the success of therapy could partially be regained by a repeated number of irradiation series. Then, it remained positive in 9 of 22 patients who had been followed-up for 10 months. The half decay period of eliminating 131I from an intradermal depot could be normalised under the influence of ultraviolet own blood irradiation. This ultraviolet own blood irradiation had no significant influence on the fibrinogen level, fibrinolytic activity, and erythrocyte aggregation (examined in 11 patients). A 2 1/2-fold diminution of monomer fibrin complexes in the blood could be observed. The titre of antistreptolysin-O was increased in all patients who had got over the infarct. It had completely normalised a week after finishing the ultraviolet own blood irradiation. Spectroscopic examinations of the blood and plasma made after ultraviolet own blood irradiation revealed that this irradiation will not only affect the properties of Hb, but will also cause a photochemical transformation accompanied by a destruction of some plasma proteins, of the membrane of formed blood elements, and a photosynthesis of biochemically active compounds. The mechanism of action of ultraviolet own blood irradiation is complicated and requires further exact investigations. Even today, however, this method can be recommended as a complex therapy in patients with severe myocardial ischemia. 相似文献
992.
993.
994.
Chelsea E. Matisz Cameron P. Goater Douglas Bray 《International journal for parasitology》2010,40(3):307-312
Evidence for the presumed linkage between the enigmatic rodlet cells of fish and exposure to helminths is anecdotal and indirect. We evaluated the proliferation and development of rodlet cells in the optic lobes of fathead minnows exposed to cercariae of Ornithodiplostomum ptychocheilus. Mean rodlet cell densities (ca. 10/mm2) in the optic lobes were similar between unexposed controls and minnows with 1- and 2-week old infections. Rodlet cell densities increased at 4 weeks p.i., reaching maxima (ca. 200/mm2) at 6 weeks p.i., followed by a decline at 9 weeks. This temporal pattern of proliferation and maturation paralleled the development of metacercariae within the optic lobes. Unencysted metacercariae develop rapidly within tissues of the optic lobes for approximately 4 weeks after penetration by cercariae, then shift to the adjacent meninges to encyst. The former stage is associated with tissue damage, the latter with massive inflammation of the meninges. Thus, peak densities and maturation of rodlet cells correspond to the period when inflammation of the meninges caused by the large metacercarial cysts is at a maximum. Our results support recent contentions that rodlet cells comprise part of the host inflammatory defence response. 相似文献
995.
996.
The RNA helicases encoded by melanoma differentiation-associated gene 5 (mda-5) and retinoic acid-inducible gene I (RIG-I) detect foreign cytoplasmic RNA molecules generated during the course of a virus infection, and their activation leads to induction of type I interferon synthesis. Paramyxoviruses limit the amount of interferon produced by infected cells through the action of their V protein, which binds to and inhibits mda-5. Here we show that activation of both mda-5 and RIG-I by double-stranded RNA (dsRNA) leads to the formation of homo-oligomers through self-association of the helicase domains. We identify a region within the helicase domain of mda-5 that is targeted by all paramyxovirus V proteins and demonstrate that they inhibit activation of mda-5 by blocking dsRNA binding and consequent self-association. In addition to this commonly targeted domain, some paramyxovirus V proteins target additional regions of mda-5. In contrast, V proteins cannot bind to RIG-I and consequently have no effect on the ability of RIG-I to bind dsRNA or to form oligomers. 相似文献
997.
Diverting the antigen from its normal intracellular location to other compartments in an antibody-mediated way represents a mode of action for intracellular antibodies [Cardinale, A., Lener, M., Messina, S., Cattaneo, A. & Biocca, S. (1998) FEBS Lett., 439, 197-202; Lener, M., Horn, I.R., Cardinale, A., Messina, S., Nielsen, U.B., Rybak, S.M., Hoogenboom, H.R., Cattaneo, A. & Biocca, S. (2000) Eur J Biochem. 267, 1196-205]. In the case of p21Ras, the sequestration of the antigen in aggregated structures in the cytoplasm of transfected cells leads to the inhibition of its biological function. We have further investigated the intracellular fate of the antigen-antibody complex by analyzing the effect of proteasome inhibitors on the formation and the intracellular localization of the aggregates. Overexpression of anti-Ras scFv fragments or inhibition of proteasomes activity leads to the formation of large perinuclear aggresomes formed of ubiquitinated-scFv fragments in which p21Ras is sequestered and degraded in an antibody-mediated way. Disruption of microtubules by nocodazole completely abrogates the accumulation of scFv fragments in a single aggresome and induces the dispersion of these structures in the periphery of the cell. Cotransfection of the GFP-scFv with a myc-tagged ubiquitin and colocalization with specific anti-proteasome antibodies indicate the recruitment of exogenous ubiquitin and proteasomes to the newly formed aggresomes. Taken together these results suggest that the intracellular antigen-antibody complex is naturally addressed to the ubiquitin-proteasome pathway and that the mechanism of ubiquitination does not inhibit the antibody binding properties and the capacity to block the antigen function. 相似文献
998.
999.
1000.
Density gradient analysis of newly replicated DNA from synchronized mouse lymphoma cells 总被引:3,自引:0,他引:3
The replication of DNA in synchronous cultures of mouse lymphoma cells was investigated by use of CsCl density gradient centrifugation. We found that the buoyant density of newly replicated DNA depended upon the particular stage of S phase in which synthesis occurred. In early S phase, newly replicated DNA exhibited buoyant densities which were slightly higher, on the average, than that of pre-existing DNA. As S phase progressed, newly replicated DNA shifted to lower buoyant densities, until, near the end of S phase, densities less than pre-existing DNA were observed. These observations are discussed in terms of their possible relevance to base compositional differences between nucleotide sequences made in early as opposed to middle or late S phase. 相似文献