全文获取类型
收费全文 | 1563篇 |
免费 | 111篇 |
国内免费 | 3篇 |
出版年
2021年 | 15篇 |
2020年 | 13篇 |
2019年 | 10篇 |
2018年 | 20篇 |
2017年 | 24篇 |
2016年 | 38篇 |
2015年 | 66篇 |
2014年 | 65篇 |
2013年 | 82篇 |
2012年 | 100篇 |
2011年 | 118篇 |
2010年 | 74篇 |
2009年 | 61篇 |
2008年 | 95篇 |
2007年 | 75篇 |
2006年 | 75篇 |
2005年 | 74篇 |
2004年 | 62篇 |
2003年 | 88篇 |
2002年 | 83篇 |
2001年 | 12篇 |
2000年 | 9篇 |
1999年 | 15篇 |
1998年 | 23篇 |
1997年 | 16篇 |
1996年 | 14篇 |
1995年 | 16篇 |
1994年 | 18篇 |
1993年 | 15篇 |
1992年 | 10篇 |
1991年 | 11篇 |
1989年 | 14篇 |
1988年 | 14篇 |
1987年 | 8篇 |
1986年 | 11篇 |
1985年 | 8篇 |
1984年 | 10篇 |
1983年 | 10篇 |
1982年 | 9篇 |
1981年 | 16篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1978年 | 9篇 |
1977年 | 7篇 |
1975年 | 9篇 |
1973年 | 7篇 |
1970年 | 7篇 |
1965年 | 8篇 |
1964年 | 6篇 |
1963年 | 6篇 |
排序方式: 共有1677条查询结果,搜索用时 15 毫秒
1.
Chungwen Wei Eugene Storozynsky A. J. McAdam Kun-Yun Yeh Brian R. Tilton Richard A. Willis Richard K. Barth R. John Looney Edith M. Lord J. G. Frelinger 《Cancer immunology, immunotherapy : CII》1996,42(6):362-368
Human prostate-specific antigen (PSA) has a highly restricted tissue distribution. Its expression is essentially limited
to the epithelial cells of the prostate gland. Moreover, it continues to be synthesized by prostate carcinoma cells. This
makes PSA an attractive candidate for use as a target antigen in the immunotherapy of prostate cancer. As a first step in
characterizing the specific immune response to PSA and its potential use as a tumor-rejection antigen, we have incorporated
PSA into a well-established mouse tumor model. Line 1, a mouse lung carcinoma, and P815, a mouse mastocytoma, have been transfected
with the cDNA for human PSA. Immunization with a PSA-expressing tumor cell line demonstrated a memory response to PSA which
protected against subsequent challenge with PSA-expressing, but not wild-type, tumors. Tumor-infiltrating lymphocytes could
be isolated from PSA-expressing tumors grown in naive hosts and were specifically cytotoxic against a syngeneic cell line
that expressed PSA. Immunization with tumor cells resulted in the generation of primary and memory cytotoxic T lymphocytes
(CTL) specific for PSA. The isolation of PSA-specific CTL clones from immunized animals further demonstrated that PSA can
serve as a target antigen for antitumor CTL. The immunogenicity studies carried out in this mouse tumor model provide a rationale
for the design of methods to elicit PSA-specific cell-mediated immunity in humans.
Received: 4 April 1996 / Accepted: 31 May 1996 相似文献
2.
High N,dry: Experimental nitrogen deposition exacerbates native shrub loss and nonnative plant invasion during extreme drought 下载免费PDF全文
Justin M. Valliere Irina C. Irvine Louis Santiago Edith B. Allen 《Global Change Biology》2017,23(10):4333-4345
Hotter, longer, and more frequent global change‐type drought events may profoundly impact terrestrial ecosystems by triggering widespread vegetation mortality. However, severe drought is only one component of global change, and ecological effects of drought may be compounded by other drivers, such as anthropogenic nitrogen (N) deposition and nonnative plant invasion. Elevated N deposition, for example, may reduce drought tolerance through increased plant productivity, thereby contributing to drought‐induced mortality. High N availability also often favors invasive, nonnative plant species, and the loss of woody vegetation due to drought may create a window of opportunity for these invaders. We investigated the effects of multiple levels of simulated N deposition on a Mediterranean‐type shrubland plant community in southern California from 2011 to 2016, a period coinciding with an extreme, multiyear drought in the region. We hypothesized that N addition would increase native shrub productivity, but that this would increase susceptibility to drought and result in increased shrub loss over time. We also predicted that N addition would favor nonnatives, especially annual grasses, leading to higher biomass and cover of these species. Consistent with these hypotheses, we found that high N availability increased native shrub canopy loss and mortality, likely due to the higher productivity and leaf area and reduced water‐use efficiency we observed in shrubs subject to N addition. As native shrub cover declined, we also observed a concomitant increase in cover and biomass of nonnative annuals, particularly under high levels of experimental N deposition. Together, these results suggest that the impacts of extended drought on shrubland ecosystems may be more severe under elevated N deposition, potentially contributing to the widespread loss of native woody species and vegetation‐type conversion. 相似文献
3.
4.
Dr. Edith Raadts 《Planta》1952,40(5):419-430
Zusammenfassung Mittels der Diffusionsmethode wurde für den aufsteigenden inaktiven Wuchsstoff der Haferkoleoptile ein Molekulargewicht ungefähr um 170 bestimmt. Das entspricht annähernd dem der -Indolessigsäure von 175. Der inaktive Wuchsstoff ist daher jedenfalls ein Derivat dieser Säure. Er ist eine neutrale Substanz und gegen Säuren und Laugen empfindlich.Mit 1 Textabbildung. 相似文献
5.
6.
The zygopterid fern Etapteris leclercqii sp. n. is described from Lower Pennsylvanian age coal balls from the Lewis Creek, Kentucky, locality. Isolated petioles extend up to 15.0 cm in length and 5.0 mm in diam; no lateral axes have been observed. The clepsydroid-shaped petiole trace is characterized by lateral arms that sharply taper and by the production of peripheral loops prior to the separation of pinna traces from the stele. Large irregularly shaped multicellular hairs are randomly scattered over the surface of the petioles. When compared with other currently recognized zygopterid ferns, E. leclercqii appears most similar to Metaclepsydropsis duplex. Based on the configuration of the leaf trace and the occurrence of peripheral loops, it is suggested that E. leclercqii may represent the most primitive species of the genus known to date. 相似文献
7.
A mutant of Neurospora crassa (pm-nbg27) was isolated on the basis of its resistance to p-fluoro-phenylalamine on ammonium-deficient Vogel's medium. This mutant was found to be devoid of both conidial and post-conidial (after 180 min of preincubation) transport acitvity of all amino acids.Genetic analysis exhibiting of pm-nbg27 by crossing it to wild-type (74A) resulted in the predicted segregants exhibiting transport characteristics of pm-n, pm-b, pm-g, pm-nb, pm-ng, pm-bg and parental types.The above observations confirm the postulated general amino acids permease system as well as a single genetic locus control of that activity. 相似文献
8.
Edith Willimzik 《Zoomorphology》1930,18(4):669-700
Ohne Zusammenfassung 相似文献
9.
10.
Male aggression,limited female choice and the ontogeny of mating behaviour in the flesh fly Sarcophaga crassipalpis 下载免费PDF全文
J. Dylan Shropshire Darrell Moore Edith Seier Karl H. Joplin 《Physiological Entomology》2015,40(4):325-335
Previous work has shown that male flesh flies (Sarcophaga crassipalpis Macquart) exhibit an ontogeny of behaviour from eclosion through sexual maturity that includes extensive changes in the expression of aggressive, non‐aggressive interactive and non‐interactive behaviours. To determine how the presence of a female flesh fly influences the manifestation of these behaviours, male flesh flies of different ages post‐eclosion are paired with same‐age females and their behaviours are monitored in a simple arena during a 50‐min observation period. All flies are socially isolated until pairing. Although the levels of expression of aggressive and non‐aggressive interactive behaviours are depressed relative to previous findings in male‐opponent pairs, the ontogeny of aggression still occurs as indicated by a significant increase, with age, in the agonistic behaviour ‘hold’. Similar to male‐opponent pairs and individual males, the performance by males of the non‐interactive behaviours ‘walking’ and ‘standing’ diminishes, whereas ‘upside‐down’ increases with age. By contrast, ‘grooming’ shows a significant age‐related decline. No courtship behaviours are observed in the males, although the aggressive behaviour ‘hold’ is a significant transition to mating. Females show no obvious courtship or rejection behaviours, although the significant increase in ‘upside‐down’ with age could possibly be a behavioural gateway to mating. The results of this study indicate that extensive age‐related changes encompassing the entire behavioural repertoire are intrinsic to male flesh flies and persist under a variety of different social contexts. 相似文献