全文获取类型
收费全文 | 17488篇 |
免费 | 1732篇 |
国内免费 | 2111篇 |
专业分类
21331篇 |
出版年
2024年 | 72篇 |
2023年 | 281篇 |
2022年 | 661篇 |
2021年 | 1020篇 |
2020年 | 735篇 |
2019年 | 888篇 |
2018年 | 800篇 |
2017年 | 562篇 |
2016年 | 755篇 |
2015年 | 1110篇 |
2014年 | 1315篇 |
2013年 | 1350篇 |
2012年 | 1571篇 |
2011年 | 1486篇 |
2010年 | 928篇 |
2009年 | 795篇 |
2008年 | 924篇 |
2007年 | 794篇 |
2006年 | 728篇 |
2005年 | 616篇 |
2004年 | 623篇 |
2003年 | 527篇 |
2002年 | 442篇 |
2001年 | 301篇 |
2000年 | 281篇 |
1999年 | 228篇 |
1998年 | 136篇 |
1997年 | 108篇 |
1996年 | 92篇 |
1995年 | 83篇 |
1994年 | 79篇 |
1993年 | 81篇 |
1992年 | 90篇 |
1991年 | 90篇 |
1990年 | 67篇 |
1989年 | 77篇 |
1988年 | 69篇 |
1987年 | 63篇 |
1986年 | 52篇 |
1985年 | 63篇 |
1984年 | 46篇 |
1983年 | 35篇 |
1982年 | 29篇 |
1981年 | 22篇 |
1979年 | 31篇 |
1978年 | 23篇 |
1977年 | 18篇 |
1975年 | 21篇 |
1974年 | 22篇 |
1973年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
Long-lasting adenovirus transgene expression in mice through neonatal intrathymic tolerance induction without the use of immunosuppression. 总被引:6,自引:0,他引:6 下载免费PDF全文
The major barrier to the clinical application of adenovirus gene therapy for diseases that require stable transgene expression is the immunogenicity of recombinant adenovirus, which ordinarily limits the duration of its effects to a period of about 2 weeks. We postulated that tolerance to adenovirus could be induced and transgene expression could be prolonged if T lymphocytes underwent thymic selection in the presence of adenovirus antigens. Mice were inoculated in the thymus with a recombinant adenovirus containing the lacZ marker gene during the neonatal period at a time before T-cell maturation had occurred. When the virus was administered intravenously to these mice in adulthood, they were found to have an impaired adenovirus-specific cytotoxic T-lymphocyte response which allowed prolonged hepatic lacZ expression, for up to 260 days. The ability to achieve unresponsiveness to a recombinant adenovirus after inoculation of the thymus in neonates extends the paradigm of intrathymic tolerance induction. Furthermore, this model will enable the study of stable adenovirus transgene expression in vivo without the use of immunosuppression and ultimately may have clinical utility. 相似文献
63.
The dissociation constants for the binding of ferric enterobactin with FepA and FecA are quantitated with displacement experiments. It is found that K
d for FepA is 12 times lower than the one for FecA. This indicates that FepA is an high-affinity receptor while FecA binds ferric enterobactin with a lower affinity. Monoclonal antibodies specific for binding epitopes of FepA inhibit the binding of ferric enterobactin with purified FepA. These same antibodies do not inhibit the binding of ferric enterobactin with purified FecA. This indicates that the binding epitopes in FecA and FepA are different. 相似文献
64.
Antibodies against aflatoxin Q1 (AFQ1) were obtained from rabbits after immunization of either AFQ1-hemisuccinate or AFQ2a conjugated to bovine serum albumin. Both radioimmunoassay and enzyme-linked immunosorbent assaY (ELISA) were used for the determination of antibody titers and specificities. Antibodies obtained from rabbits after immunization with AFQ1-hemisuccinate-bovine serum albumin had the highest affinity to aflatoxin B1, whereas antibodies obtained from rabbits after immunization with AFQ2a-bovine serum albumin bound most effectively with AFQ2a. AFQ2a antibody was selected for the subsequent direct and indirect ELISA for the detection of AFQ1 in biological fluids. When AFQ2a-peroxidase and AFQ2a antibody were used, direct ELISA was able to detect as low as 2 ppb (ng/ml) of AFQ1 spiked in the urine samples that had been subjected to a Sep-Pak cleanup treatment. In indirect ELISA in which the antigen (AFQ2a-bovine serum albumin) was coated to the solid phase followed by reaction with rabbit antibody and goat anti-rabbit immunoglobulin G-peroxidase conjugate, 50-fold less antibody was used without sacrificing sensitivity. Recoveries of AFQ1 added to urine samples (2 to 40 ppb) were 46.3 to 73% and 65.8 to 85.8% for direct and indirect ELISA, respectively. 相似文献
65.
66.
Three peptide fragments (designated II, III and IV) of human prostatic acid phosphatase (PAP) were isolated to homogeneity from a limited tryptic hydrolysate of PAP by gel filtration on Sephadex G-100, followed by chromatography on DEAE-cellulose and Sephadex G-75. The homogeneity was confirmed by disc poly-acrylamide-gel electrophoresis. The Mr values were 32 500, 25 000 and 11 000 as estimated by gel filtration and sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. Immunoprecipitation study revealed that only fragment II formed an immune precipitate with anti-PAP antibodies. Fragment II exhibited 45% of maximum inhibitory activity on the reaction between PAP and goat anti-PAP IgG (immunoglobulin G) antibodies (or rabbit anti-PAP antibodies), whereas fragments III and IV demonstrated 24% (or 23%) and 29% (or 27%) inhibition respectively. A mixture of these three tryptic fragments of PAP result in 96% (for goat anti-PAP antibodies) and 94% (for rabbit anti-PAP antibodies) inhibitory activities, which were equivalent to the sum of maximum inhibitory activity of the three fragments individually. The results demonstrated that these three tryptic peptide fragments carried all the antigenic active sites of the native PAP, and suggested that the entire molecule of human PAP comprised a minimum of four distinguishable, nonoverlapping antigenic determinants. These three fragments also were shown to retain all the disulphide bonds of the native PAP, and thus were useful reagents for the elucidation of PAP molecular structure. 相似文献
67.
68.
Antibody against T-2 toxin was obtained after immunization of rabbits with bovine serum albumin-T-2 hemisuccinate conjugate. The antibody had greatest binding efficiency for T-2 toxin, less efficiency for HT-2, and least for T-2 triol. Cross-reaction of antibody with neosolaniol, T-2 tetraol, and 8-acetyl-neosolaniol was very weak. Diacetoxyscirpenol, trichodermin, vomitoxin, and verrucarin A essentially gave no cross-reaction with the antibody. The sensitivity of the binding assay for T-2 toxin detection was in the range of 1 to 20 ng per assay. Detailed methods for the preparation of the conjugate and the production of immune serum and methods for antibody determination are described. 相似文献
69.
Bacteria were found that are capable of producing good yields of β-amylase in unrefined media. The culture filtrates are free of α-amylase and isoamylase. 相似文献
70.
Antibody against aflatoxin B1 was obtained after one multiple-site injection of bovine serum albumin-aflatoxin B1 conjugate into rabbits. The antibody has greatest binding efficiency for aflatoxin B1, less efficiency for B2, G1, and Q1, and least for aflatoxicol, G2, and M1. Sterigmatocystin, coumarin, and 4-hydroxycoumarin did not give a cross-reaction with the antibody. The sensitivity of the binding assay for detection of aflatoxin B1 is in the range of 0.2 to 2.0 ng per 0.5-ml sample. Detailed methods for the preparation of the conjugate, production of immune serum, and methods for antibody titer determination are described. 相似文献