全文获取类型
收费全文 | 502篇 |
免费 | 67篇 |
国内免费 | 1篇 |
出版年
2021年 | 8篇 |
2020年 | 11篇 |
2019年 | 15篇 |
2018年 | 3篇 |
2017年 | 9篇 |
2016年 | 23篇 |
2015年 | 20篇 |
2014年 | 24篇 |
2013年 | 32篇 |
2012年 | 44篇 |
2011年 | 33篇 |
2010年 | 23篇 |
2009年 | 21篇 |
2008年 | 31篇 |
2007年 | 24篇 |
2006年 | 29篇 |
2005年 | 22篇 |
2004年 | 21篇 |
2003年 | 15篇 |
2002年 | 13篇 |
2001年 | 6篇 |
2000年 | 10篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1985年 | 7篇 |
1983年 | 4篇 |
1980年 | 4篇 |
1979年 | 11篇 |
1978年 | 3篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1973年 | 5篇 |
1972年 | 7篇 |
1971年 | 7篇 |
1970年 | 2篇 |
1969年 | 2篇 |
1968年 | 5篇 |
1967年 | 2篇 |
1965年 | 2篇 |
排序方式: 共有570条查询结果,搜索用时 15 毫秒
1.
2.
Ernst Sutter 《Journal of Ornithology》1955,96(2):220-222
Ohne Zusammenfassung 相似文献
3.
4.
The role of indole-3-butyric acid (IBA) in adventitious root formation was studied by analyzing the uptake and subsequent metabolism of IBA in shoots of M.26 apple (Malus pumila Mill.) rootstock grown in vitro. Roots were induced by exposing shoots to 4 M IBA and [3H]IBA for 5 days in the dark and then transferring them to plant growth regulator (PGR)-free medium in the light until roots formed. Approximately 50% of the total radioactivity applied was taken up from the agar medium by the shoots during the 5-day incubation period in IBA. Indole-3-butyric acid metabolism was studied by extraction and high-performance liquid chromatographic (HPLC) separation of [3H]IBA and metabolites from the basal sections of treated shoots. The major [3H]IBA metabolite co-eluted with authentic [14C]indole-3-acetic acid (IAA) suggesting that IBA was converted to IAA in the shoots. The proportion of newly synthesized IAA present as conjugates was higher at the end of the 5-day IBA treatment period than after 13 days in PGR-free medium. There appeared to be no conjugation of IBA at any time. 相似文献
5.
Patterns of viral replication correlate with outcome in simian immunodeficiency virus (SIV)-infected macaques: effect of prior immunization with a trivalent SIV vaccine in modified vaccinia virus Ankara. 总被引:23,自引:15,他引:8 下载免费PDF全文
V M Hirsch T R Fuerst G Sutter M W Carroll L C Yang S Goldstein M Piatak Jr W R Elkins W G Alvord D C Montefiori B Moss J D Lifson 《Journal of virology》1996,70(6):3741-3752
The dynamics of plasma viremia were explored in a group of 12 simian immunodeficiency virus (SIV)-infected rhesus macaques (Macaca mulatta) that had received prior immunization with either nonrecombinant or trivalent (gag-pol, env) SIV-recombinant vaccinia viruses. Three distinct patterns of viral replication observed during and following primary viremia accounted for significant differences in survival times. High-level primary plasma viremia with subsequently increasing viremia was associated with rapid progression to AIDS (n = 2). A high-level primary plasma virus load with a transient decline and subsequent progressive increase in viremia in the post-acute phase of infection was associated with progression to AIDS within a year (n = 6). Low levels of primary plasma viremia followed by sustained restriction of virus replication were associated with maintenance of normal lymphocyte subsets and intact lymphoid architecture (n = 4), reminiscent of the profile observed in human immunodeficiency virus type 1-infected long-term nonprogressors. Three of four macaques that showed this pattern had been immunized with an SIV recombinant derived from the attenuated vaccinia virus, modified vaccinia virus Ankara. These data link the dynamics and extent of virus replication to disease course and suggest that sustained suppression of virus promotes long-term, asymptomatic survival of SIV-infected macaques. These findings also suggest that vaccine modulation of host immunity may have profound beneficial effects on the subsequent disease course, even if sterilizing immunity is not achieved. 相似文献
6.
7.
The biodegradation of three synthetic 14C-labeled polymers, poly(methyl methacrylate), phenol formaldehyde, and polystyrene, was studied with 17 species of fungi in axenic cultures, five groups of soil invertebrates, and a variety of mixed microbial communities including sludges, soils, manures, garbages, and decaying plastics. Extremely low decomposition rates were found. The addition of cellulose and mineral failed to increase decomposition rates significantly. 相似文献
8.
Summary Cell suspensions of the fresh-watersponge Ephydatia fluviatilis have been fractionated by means ofFicoll gradient centrifugation. Three fractions were isolated. The densest contains archeocyte-like cells only; the intermediate fraction is very rich in choanocytes, and the lightest is a mixture of cell types. Earch fraction shows specificaggregative properties and potentialities to reconstitute functional sponges.It appears that the sequence of reconstitution events can be selectively altered by certain disequilibria in the cell populationThese preliminary results constitute a first approach to the analysis ofcell type specificity in sponges. 相似文献
9.
Measurement of indolebutyric Acid in plant tissues by isotope dilution gas chromatography-mass spectrometry analysis 总被引:4,自引:2,他引:2 下载免费PDF全文
An internal standard, [13C][indole-2]-indole-3-butyric acid, was synthesized from indole-2[13C] and was shown to be effective for the quantitative determination of indole-3-butyric acid from plant tissue. When this standard was used along with [13C6]indole-3-acetic acid, both indolic auxins could be quantified from the same tobacco (Nicotiana tabacam) leaf sample by isotope dilution analysis using selected ion monitoring gas chromatography-mass spectrometry for detection. 相似文献
10.
This study examines the effect of various plasma proteins from man on the spontaneous contractile activity of the rat portal vein. Albumin, gamma-globulin, alpha-globulin, beta-globulin (the major plasma proteins), and immunoglobulin IgG (the major immunoglobulin present in the gamma-globulin fraction) were obtained commercially. Mesenteric portal vein strips were prepared from rats and placed in a physiological salt solution in muscle baths for the measurement of longitudinal mechanical response. Portal veins exposed to albumin or gamma-globulin showed a dose-dependent increase in the spontaneous activity, whereas those exposed to alpha-globulin or alpha- and beta-globulin together showed a dose-dependent inhibition of spontaneous activity. Immunoglobulin IgG produced a dose-dependent increase in the spontaneous activity similar to that of gamma-globulin. The increased spontaneous activity produced by albumin was not prevented by ouabain but was inhibited by phentolamine. Spontaneous contractile activity was stimulated by albumin in the chemically (6-hydroxydopamine) denervated portal vein. These findings indicate that albumin acts in a manner similar to noradrenaline. The increased spontaneous activity caused by gamma-globulin (IgG) was inhibited by ouabain or verapamil. The effect of IgG was not dependent on alpha-adrenergic, cholinergic, histaminergic, serotoninergic, or renin angiotensin systems nor was it affected by removal of the endothelium. These observations may have implications in the pathophysiology of essential hypertension. 相似文献