全文获取类型
收费全文 | 3529篇 |
免费 | 303篇 |
国内免费 | 203篇 |
出版年
2023年 | 141篇 |
2022年 | 131篇 |
2021年 | 238篇 |
2020年 | 171篇 |
2019年 | 198篇 |
2018年 | 180篇 |
2017年 | 133篇 |
2016年 | 141篇 |
2015年 | 205篇 |
2014年 | 208篇 |
2013年 | 249篇 |
2012年 | 172篇 |
2011年 | 148篇 |
2010年 | 139篇 |
2009年 | 178篇 |
2008年 | 178篇 |
2007年 | 182篇 |
2006年 | 163篇 |
2005年 | 126篇 |
2004年 | 116篇 |
2003年 | 89篇 |
2002年 | 65篇 |
2001年 | 45篇 |
2000年 | 32篇 |
1999年 | 26篇 |
1998年 | 22篇 |
1997年 | 23篇 |
1996年 | 39篇 |
1995年 | 23篇 |
1994年 | 19篇 |
1993年 | 18篇 |
1992年 | 24篇 |
1991年 | 20篇 |
1990年 | 14篇 |
1989年 | 12篇 |
1988年 | 12篇 |
1985年 | 11篇 |
1984年 | 8篇 |
1983年 | 8篇 |
1982年 | 19篇 |
1981年 | 11篇 |
1980年 | 5篇 |
1979年 | 12篇 |
1978年 | 14篇 |
1977年 | 7篇 |
1976年 | 11篇 |
1975年 | 15篇 |
1974年 | 9篇 |
1973年 | 10篇 |
1972年 | 4篇 |
排序方式: 共有4035条查询结果,搜索用时 15 毫秒
11.
ALEX CÓRDOBA‐AGUILAR DANIELA RUIZ‐SILVA ROBERTO MUNGUÍA‐STEYER HUMBERTO LANZ‐MENDOZA 《Physiological Entomology》2011,36(4):335-342
Recent studies of female insects indicate that reproductive activities, such as mating and oviposition, can impair immune ability. Using the two tropical damselfly species Argia anceps Garrison and Hetaerina americana (Fabricius), egg production and phenoloxidase (PO) activity, a key enzyme in insect immunity, are measured in mating, ovipositing and perching females in December and March. Perching females of both species have fewer eggs compared with mating and ovipositing females, which suggests that perching females are not engaged in reproduction. There is seasonal variation in egg number for the three categories in H. americana but not in A. anceps, which can be interpreted in terms of adaptive changes in egg production depending on female–male interactions in the former species but not in the latter species. There is no difference in PO activity among mating, ovipositing or perching females within either species, although measurements in December and March indicate distinct seasonal changes. Juvenile Hormone (JH) is known to reduce the effectiveness of the immune system by favouring the use of resources for reproduction. A possible role for JH is examined in H. americana, using the JH analogue methoprene to manipulate hormone activity, revealing that PO activity is reduced in methoprene‐treated H. americana females. Thus, although the results of the present study are indicative of possible hormone‐driven changes in PO, there is not necessarily a down‐regulation of immune function (as determined by PO activity) during mating or oviposition. The results complement some recent studies countering the idea that reproductive activities reduce the immune ability in insects. 相似文献
12.
13.
Mengjie Liu Ya-Jie Li Yu-Xiu Zhu Yang Sun Guan-Feng Wang 《Molecular Plant Pathology》2021,22(5):564-579
Most plant intracellular immune receptors belong to nucleotide-binding, leucine-rich repeat (NLR) proteins. The recognition between NLRs and their corresponding pathogen effectors often triggers a hypersensitive response (HR) at the pathogen infection sites. The nicotinate N-methyltransferase (NANMT) is responsible for the conversion of nicotinate to trigonelline in plants. However, the role of NANMT in plant defence response is unknown. In this study, we demonstrated that the maize ZmNANMT, but not its close homolog ZmCOMT, an enzyme in the lignin biosynthesis pathway, suppresses the HR mediated by the autoactive NLR protein Rp1-D21 and its N-terminal coiled-coil signalling domain (CCD21). ZmNANMT, but not ZmCOMT, interacts with CCD21, and they form a complex with HCT1806 and CCoAOMT2, two key enzymes in lignin biosynthesis, which can also suppress the autoactive HR mediated by Rp1-D21. ZmNANMT is mainly localized in the cytoplasm and nucleus, and either localization is important for suppressing the HR phenotype. These results lay the foundation for further elucidating the molecular mechanism of NANMTs in plant disease resistance. 相似文献
14.
15.
Transgenerational effects of infection have a huge potential to influence the prevalence and intensity of infections in vectors and, by extension, disease epidemiology. These transgenerational effects may increase the fitness of offspring through the transfer of protective immune factors. Alternatively, however, infected mothers may transfer the costs of infection to their offspring. Although transgenerational immune protection has been described in a dozen invertebrate species, we still lack a complete picture of the incidence and importance of transgenerational effects of infection in most invertebrate groups. The existence of transgenerational infection effects in mosquito vectors is of particular interest because of their potential for influencing parasite prevalence and intensity and, by extension, disease transmission. Here we present what we believe to be the first study on transgenerational infection effects in a mosquito vector infected with malaria parasites. The aim of this experiment was to quantify both the benefits and the costs of having an infected mother. We find no evidence of transgenerational protection in response to a Plasmodium infection. Having an infected mother does, however, entail considerable fecundity costs for the offspring: fecundity loss is three times higher in infected offspring issued from infected mothers than in infected offspring issued from uninfected mothers. We discuss the implications of our results and we call for more studies looking at transgenerational effects of infection in disease vectors. 相似文献
16.
17.
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
18.
Giancarlo Pizza Renato Meduuri Caterina De Vinci Lucia Scorolli Dr. Dimitri Viza 《Biotherapy》1994,8(1):63-68
Transfer Factor is a dialysable moiety obtained from immune lymphocytes. It has been successfully used for the treatment of several viral infections including labial and genital herpes. In the present study, thirty-three patients with low immune response to HSV antigens and suffering from herpes ocular infections were orally treated with HSV-specific transfer factor (TF). Their relapse index was reduced from 20.1 before treatment to 0.51 after TF administration, with only 6/33 patients relapsing. Although this is not a placebo-controlled-randomized study, the results suggest that TF specific for HSV antigens may be efficacious for preventing relapses of ocular herpes infections as has been the case with genital and labial localisations.Abbreviations CMI
Cell-mediated immunity
- CMV
Cytomegalo-virus
- EBV
Epstein-Barr virus
- HIV
Human immunodeficiency virus
- HK
Herpes keratitis
- HSV
Herpes simplex virus
- IRI
Individual relapse index
- KU
Kerato-uveitis
- LMT
Leucocyte migration test
- LST
Lymphocyte stimulation test
- MIF
Migration inhibition factor
- RHK
Relapsing herpes keratitis
- TF
Transfer factor 相似文献
19.
20.