全文获取类型
收费全文 | 6098篇 |
免费 | 978篇 |
国内免费 | 3660篇 |
出版年
2024年 | 44篇 |
2023年 | 242篇 |
2022年 | 352篇 |
2021年 | 398篇 |
2020年 | 401篇 |
2019年 | 429篇 |
2018年 | 256篇 |
2017年 | 283篇 |
2016年 | 282篇 |
2015年 | 398篇 |
2014年 | 595篇 |
2013年 | 496篇 |
2012年 | 700篇 |
2011年 | 633篇 |
2010年 | 551篇 |
2009年 | 560篇 |
2008年 | 597篇 |
2007年 | 587篇 |
2006年 | 511篇 |
2005年 | 451篇 |
2004年 | 326篇 |
2003年 | 282篇 |
2002年 | 220篇 |
2001年 | 227篇 |
2000年 | 220篇 |
1999年 | 146篇 |
1998年 | 82篇 |
1997年 | 67篇 |
1996年 | 34篇 |
1995年 | 38篇 |
1994年 | 19篇 |
1993年 | 19篇 |
1992年 | 22篇 |
1991年 | 23篇 |
1990年 | 25篇 |
1989年 | 33篇 |
1988年 | 17篇 |
1987年 | 14篇 |
1986年 | 22篇 |
1985年 | 10篇 |
1984年 | 9篇 |
1983年 | 14篇 |
1982年 | 22篇 |
1981年 | 8篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1965年 | 6篇 |
1964年 | 8篇 |
1953年 | 5篇 |
1950年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 292 毫秒
11.
12.
蚤数量与宿主数量关系 总被引:9,自引:5,他引:4
无论在自然条件下或在人为条件下,蚤指数和染蚤率的高低与宿主密度的高低是一致的.宿主密度的升降,会导致其寄生蚤指数和染蚤率的升降. 本文讨论了宿主数量下降导致其寄生蚤数量下降的原因,仅是分析推测,提出几方面的看法. 相似文献
13.
本文报导四川省西部鱼类寄生粘孢子虫粘体虫属六新种,即异型粘体虫,新种Myxosoma disparis sp.nov.,四川粘体虫,新种Myxosoma sichuanensis sp.nov.,光唇粘体虫,新种Myxosoma acrossochilusi sp.nov.鳅粘体虫,新种Myxosoma nemachilusi sp.nov.斜囊粘体虫,新种Myxosoma obliqua sp.nov.,雅安粘体虫,新种Myxosoma yaanensis sp.nov.。 相似文献
14.
关于苦马豆属学名的讨论 总被引:2,自引:0,他引:2
本文根据国内外豆科研究文献的考证,讨论了苦马豆属(Sphaerophysa DC.)及其近缘属的区别,重新确认了国产苦马豆属和苦马豆的学名。 相似文献
15.
Abstract The vitellogenic period of gypsy moth ovarian development starts on day 3 of the pupal stage and continues through adulthood. During this period, rapid increases occur in follicle size, protein content, and wet weight of the ovary. Patency is observed on day 3 of the pupal stage.
Pre-vitellogenic follicles are formed in the last larval stadium. Newly formed follicles detach from the germarium on day 4, and increase rapidly to 140 per ovariole at the end of the last larval stadium. The pre-vitellogenic follicles are uniformly around 50 um in diameter. No vitellogenin is incorporated into the oocytes until the pupal stage.
Polyacrylamide gel electrophosesis (PAGE) in the presence of sodium dodecylsulphate (SDS) analysis of male and female haemolymph samples and vitellogenic ovaries demonstrates the presence of two female-specific subunits of vitellogenin of 180 kD and 160 kD. These proteins are detected only in haemolymph and ovarian extracts of vitellogenic females. The molecular weight of the native protein determined by size exclusion chromatography is approximately 400–420 kD.
A highly sensitive double antibody sandwich enzyme-linked immunosorbent assay (ELISA) was developed to monitor the temporal changes in vitellogenin titre in haemolymph. Vitellogenin production starts on day 2 of the last larval stadium, reaching a maximum level by day 6 of the last larval stadium, and decreasing in the late pupal stage as vitellogenin was internalized into the oocytes. This is the first report of vitellogenin production occurring in the larval stage of a holometabolous insect. The fact that vitellogenin production and uptake occur during different stages of development in the gypsy moth, opens up some interesting questions concerning the underlying regulatory mechanisms controlling each process. 相似文献
Pre-vitellogenic follicles are formed in the last larval stadium. Newly formed follicles detach from the germarium on day 4, and increase rapidly to 140 per ovariole at the end of the last larval stadium. The pre-vitellogenic follicles are uniformly around 50 um in diameter. No vitellogenin is incorporated into the oocytes until the pupal stage.
Polyacrylamide gel electrophosesis (PAGE) in the presence of sodium dodecylsulphate (SDS) analysis of male and female haemolymph samples and vitellogenic ovaries demonstrates the presence of two female-specific subunits of vitellogenin of 180 kD and 160 kD. These proteins are detected only in haemolymph and ovarian extracts of vitellogenic females. The molecular weight of the native protein determined by size exclusion chromatography is approximately 400–420 kD.
A highly sensitive double antibody sandwich enzyme-linked immunosorbent assay (ELISA) was developed to monitor the temporal changes in vitellogenin titre in haemolymph. Vitellogenin production starts on day 2 of the last larval stadium, reaching a maximum level by day 6 of the last larval stadium, and decreasing in the late pupal stage as vitellogenin was internalized into the oocytes. This is the first report of vitellogenin production occurring in the larval stage of a holometabolous insect. The fact that vitellogenin production and uptake occur during different stages of development in the gypsy moth, opens up some interesting questions concerning the underlying regulatory mechanisms controlling each process. 相似文献
16.
17.
L Poltronieri E Melloni M Rubini R Selvatici C Mazzilli R Baricordi E Gandini 《Biochemical and biophysical research communications》1988,156(1):46-53
Cytoplasmic protein kinase C (PKC) has been studied in phytohemagglutinin (PHA) activated peripheral blood mononuclear cells (PBMC) and macrophage depleted E+ cell culture. Within 10' after contemporanous addition of PHA and anti HLA class I monoclonal antibody 01.65 (MoAb) PKC is depleted in both cell types. Enzyme activity recovers in the following hours however at 72 hours is at control values in E+ cultures while in PBMC cultures it is still depleted at 68% of the control. Anti HLA class I MoAb induced tritiated lymidine (3H-TdR) incorporation inhibition appears to be related to low levels of PKC activity. 相似文献
18.
19.
20.
Effect of oxidants and antioxidants on chromosomal breakage in Fanconi anemia lymphocytes 总被引:4,自引:0,他引:4
B. Dallapiccola B. Porfirio V. Mokini G. Alimena G. Isacchi E. Gandini 《Human genetics》1985,69(1):62-65
Summary Peripheral blood lymphocytes from eight Fanconi anemia (FA) patients, 14 FA heterozygotes, and nine normal subjects have been tested for their susceptibility to chromosomal breakage induction by diepoxybutane (DEB) and by two peroxides. In addition, the effect of five antioxidants was investigated in standard cultures and in cultures stressed either with DEB or with butylhydroperoxide (BHP) or with hydrogen peroxide (H2O2). DEB, BHP, and H2O2 dramatically increased the chromosomal breakage levels in homozygous and heterozygous FA cells. A partial correction of chromosomal instability was obtained by treating the patients' lymphocytes with antioxidants. A protective effect was also noted in the DEB or peroxide-stressed lymphocytes of patients and heterozygotes, grown in the presence of antioxidants. 相似文献