全文获取类型
收费全文 | 19432篇 |
免费 | 1948篇 |
国内免费 | 5篇 |
出版年
2022年 | 195篇 |
2021年 | 389篇 |
2020年 | 200篇 |
2019年 | 248篇 |
2018年 | 278篇 |
2017年 | 247篇 |
2016年 | 431篇 |
2015年 | 717篇 |
2014年 | 786篇 |
2013年 | 993篇 |
2012年 | 1202篇 |
2011年 | 1125篇 |
2010年 | 740篇 |
2009年 | 574篇 |
2008年 | 858篇 |
2007年 | 929篇 |
2006年 | 817篇 |
2005年 | 789篇 |
2004年 | 763篇 |
2003年 | 658篇 |
2002年 | 679篇 |
2001年 | 456篇 |
2000年 | 428篇 |
1999年 | 381篇 |
1998年 | 233篇 |
1997年 | 182篇 |
1996年 | 175篇 |
1995年 | 146篇 |
1994年 | 179篇 |
1993年 | 158篇 |
1992年 | 260篇 |
1991年 | 260篇 |
1990年 | 259篇 |
1989年 | 236篇 |
1988年 | 238篇 |
1987年 | 252篇 |
1986年 | 194篇 |
1985年 | 222篇 |
1984年 | 204篇 |
1983年 | 195篇 |
1982年 | 160篇 |
1981年 | 141篇 |
1980年 | 139篇 |
1979年 | 184篇 |
1978年 | 182篇 |
1977年 | 140篇 |
1976年 | 138篇 |
1975年 | 145篇 |
1974年 | 152篇 |
1972年 | 155篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
52.
A neonate with aniridia was found to have a one band paracentric inversion of the short arm of chromosome 4. This was initially difficult to interpret on high resolution banding. The inversion was present in three generations of the family. 相似文献
53.
Kathryn S. Evans Janneke Wit Lewis Stevens Steffen R. Hahnel Briana Rodriguez Grace Park Mostafa Zamanian Shannon C. Brady Ellen Chao Katherine Introcaso Robyn E. Tanny Erik C. Andersen 《PLoS pathogens》2021,17(3)
Parasitic nematodes cause a massive worldwide burden on human health along with a loss of livestock and agriculture productivity. Anthelmintics have been widely successful in treating parasitic nematodes. However, resistance is increasing, and little is known about the molecular and genetic causes of resistance for most of these drugs. The free-living roundworm Caenorhabditis elegans provides a tractable model to identify genes that underlie resistance. Unlike parasitic nematodes, C. elegans is easy to maintain in the laboratory, has a complete and well annotated genome, and has many genetic tools. Using a combination of wild isolates and a panel of recombinant inbred lines constructed from crosses of two genetically and phenotypically divergent strains, we identified three genomic regions on chromosome V that underlie natural differences in response to the macrocyclic lactone (ML) abamectin. One locus was identified previously and encodes an alpha subunit of a glutamate-gated chloride channel (glc-1). Here, we validate and narrow two novel loci using near-isogenic lines. Additionally, we generate a list of prioritized candidate genes identified in C. elegans and in the parasite Haemonchus contortus by comparison of ML resistance loci. These genes could represent previously unidentified resistance genes shared across nematode species and should be evaluated in the future. Our work highlights the advantages of using C. elegans as a model to better understand ML resistance in parasitic nematodes. 相似文献
54.
55.
56.
Sabrina Locatelli Kurt A. McKean Paul R. Sesink Clee Mary Katherine Gonder 《International journal of primatology》2014,35(2):349-375
Examining how pathogens cross species boundaries, spread within species, and persist within their hosts is an essential part of understanding the factors that underpin the evolution of virulence and host resistance. Here, we review current knowledge about the genetic diversity, molecular epidemiology, prevalence, and pathogenicity of simian immunodeficiency viruses (SIVs). SIVs have crossed species boundaries from simian hosts to humans on at least 12 separate occasions, one of which led to the global HIV–AIDS crisis. Though SIVs infect a wide range of primates, scientists have only recently begun to describe the natural history of SIV infection in their natural hosts. Several new studies reveal how both viral and host factors are responsible for the transmission to, and adaptation in, new hosts. These studies also suggest that the spread of the virus may be affected by host-specific traits, including social structure, mating system and demographic history. These studies challenge the traditional view that SIV is relatively benign in its natural host, and instead suggest that a highly dynamic relationship exists between SIV and its simian hosts. 相似文献
57.
Peroxisomal membrane proteins (PMPs) from the Swiss-Webster mouse are analyzed and compared to those of rats and humans using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting. A purification procedure for fresh mouse, rat, or human biopsy liver which enriches peroxisomal/mitochondrial marker enzyme ratios over 100-fold is characterized. When analyzed by SDS-PAGE, membranes of purified liver peroxisomes are shown to contain the same complement of 145-, 70-, 55-, 36-, and 22-kDa PMPs in rats, mice, and humans. A rabbit polyclonal antibody raised against mouse peroxisomal membranes demonstrates immunoreactivity to 145- and 70-kDa proteins in fresh liver homogenates from all three species and in control or Zellweger syndrome fibroblasts from humans. Human autopsy or placental tissues which were refrigerated before analysis exhibited 105-, 55-, and 36-kDa peptides which may be derived from the 145- and 70-kDa peptides. Such conversions, if related to degradation, may explain difficulties in purifying peroxisomes from human autopsy specimens. Variable amounts of the 55-kDa peptide also occurred in mouse adrenal and lung, and the conversion of higher to lower molecular weight PMPs could not be demonstrated by in vitro incubation of mouse liver. Further definition of the structure and variability of mammalian PMPs should be helpful in understanding polyenzymopathies such as Zellweger syndrome. 相似文献
58.
Different pathways of [3H]inositol phosphate formation mediated by alpha 1a- and alpha 1b-adrenergic receptors 总被引:1,自引:0,他引:1
The types of inositol phosphates (InsPs) formed in response to activation of alpha 1-adrenergic receptor subtypes were determined in collagenase-dispersed renal cells and hepatocytes by high pressure liquid chromatography separation. In hepatocytes, which contain only the alpha 1b subtype, norepinephrine stimulated rapid (10-s) formation of [3H]Ins(1,4,5)P3 and [3H]Ins(1,3,4)P3 and slower (5-min) formation of Ins(1,4)P2 and Ins(1)P. Selective inactivation of alpha 1b receptors by chloroethylclonidine almost completely blocked the effects of norepinephrine in hepatocytes. In renal cells, which contain both alpha 1a and alpha 1b receptors in a 60:40 ratio, norepinephrine did not significantly increase the size of any peaks until 5 min after agonist activation. At this time, only a peak eluting with Ins(1)P and one eluting shortly after Ins(1,4)P2 were significantly elevated. Incubation with norepinephrine for 2 h caused small but significant increases in peaks co-eluting with Ins(1)P and Ins(1,4,5)P3 in renal cells; however, only the increase in Ins(1)P was inhibited by chloroethylclonidine pretreatment. Extraction under neutral conditions suggested that cyclic InsPs may be the primary compounds formed in response to norepinephrine in renal cells. Removal of extracellular Ca2+ caused a 60% reduction in the InsP response to norepinephrine in renal cells but had no effect in hepatocytes. These results suggest that activation of alpha 1a and alpha 1b receptor subtypes results in formation of different InsPs and that the response to alpha 1a activation may require influx of extracellular Ca2+. 相似文献
59.
60.