全文获取类型
收费全文 | 7177篇 |
免费 | 350篇 |
国内免费 | 1篇 |
出版年
2023年 | 13篇 |
2022年 | 37篇 |
2021年 | 75篇 |
2020年 | 51篇 |
2019年 | 59篇 |
2018年 | 143篇 |
2017年 | 116篇 |
2016年 | 171篇 |
2015年 | 249篇 |
2014年 | 289篇 |
2013年 | 424篇 |
2012年 | 728篇 |
2011年 | 1277篇 |
2010年 | 593篇 |
2009年 | 640篇 |
2008年 | 325篇 |
2007年 | 314篇 |
2006年 | 282篇 |
2005年 | 266篇 |
2004年 | 228篇 |
2003年 | 202篇 |
2002年 | 196篇 |
2001年 | 53篇 |
2000年 | 46篇 |
1999年 | 64篇 |
1998年 | 51篇 |
1997年 | 58篇 |
1996年 | 52篇 |
1995年 | 44篇 |
1994年 | 39篇 |
1993年 | 27篇 |
1992年 | 39篇 |
1991年 | 28篇 |
1990年 | 25篇 |
1989年 | 22篇 |
1988年 | 22篇 |
1987年 | 18篇 |
1986年 | 31篇 |
1985年 | 16篇 |
1984年 | 23篇 |
1983年 | 20篇 |
1982年 | 12篇 |
1981年 | 20篇 |
1980年 | 14篇 |
1979年 | 11篇 |
1977年 | 12篇 |
1974年 | 9篇 |
1972年 | 10篇 |
1969年 | 9篇 |
1967年 | 8篇 |
排序方式: 共有7528条查询结果,搜索用时 156 毫秒
1.
2.
3.
Vincent Anquetil Caroline Le Sommer Agn��s M��reau Sandra Hamon Hubert Lerivray Serge Hardy 《The Journal of biological chemistry》2009,284(47):32370-32383
Alternative splicing of 3′-terminal exons plays a critical role in gene expression by producing mRNA with distinct 3′-untranslated regions that regulate their fate and their expression. The Xenopus α-tropomyosin pre-mRNA possesses a composite internal/3′-terminal exon (exon 9A9′) that is differentially processed depending on the embryonic tissue. Exon 9A9′ is repressed in non-muscle tissue by the polypyrimidine tract binding protein, whereas it is selected as a 3′-terminal or internal exon in myotomal cells and adult striated muscles, respectively. We report here the identification of an intronic regulatory element, designated the upstream terminal exon enhancer (UTE), that is required for the specific usage of exon 9A9′ as a 3′-terminal exon in the myotome. We demonstrate that polypyrimidine tract binding protein prevents the activity of UTE in non-muscle cells, whereas a subclass of serine/arginine rich (SR) proteins promotes the selection of exon 9A9′ in a UTE-dependent way. Morpholino-targeted blocking of UTE in the embryo strongly reduced the inclusion of exon 9A9′ as a 3′-terminal exon in the endogenous mRNA, demonstrating the function of UTE under physiological circumstances. This strategy allowed us to reveal a splicing pathway that generates a mRNA with no in frame stop codon and whose steady-state level is translation-dependent. This result suggests that a non-stop decay mechanism participates in the strict control of the 3′-end processing of the α-tropomyosin pre-mRNA. 相似文献
4.
The authors present data from a group of 55 patients suffering from chronic renal diseases. Twenty-two were treated by haemodialysis; the rest had serum creatinine levels ranging from normal to 950 mumol/l. The molar esterification rats [MER] and total cholesterol [TCH] values decreased parallel to the gradual extinction of renal function. A reduced fractional esterification rate [FER] was found in about two thirds of the dialysed patients and in about half of those whose kidney function was still relatively well preserved. It can thus be concluded that reduction of FER values indicative of a disturbance of cholesterol metabolism can already be detected in the early stages of chronic nephropathies. 相似文献
5.
Daneen Schaeffer Filipa Pereira Reis Sean J. Johnson Cec��lia Maria Arraiano Ambro van Hoof 《Nucleic acids research》2012,40(18):9298-9307
The 10-subunit RNA exosome is involved in a large number of diverse RNA processing and degradation events in eukaryotes. These reactions are carried out by the single catalytic subunit, Rrp44p/Dis3p, which is composed of three parts that are conserved throughout eukaryotes. The exosome is named for the 3′ to 5′ exoribonuclease activity provided by a large C-terminal region of the Rrp44p subunit that resembles other exoribonucleases. Rrp44p also contains an endoribonuclease domain. Finally, the very N-terminus of Rrp44p contains three Cys residues (CR3 motif) that are conserved in many eukaryotes but have no known function. These three conserved Cys residues cluster with a previously unrecognized conserved His residue in what resembles a metal-ion-binding site. Genetic and biochemical data show that this CR3 motif affects both endo- and exonuclease activity in vivo and both the nuclear and cytoplasmic exosome, as well as the ability of Rrp44p to associate with the other exosome subunits. These data provide the first direct evidence that the exosome-Rrp44p interaction is functionally important and also provides a molecular explanation for the functional defects when the conserved Cys residues are mutated. 相似文献
6.
7.
8.
9.
The Anemia monica Verrill population in Mono Lake, Californiahas two generations per year. Despite similarities in the year-to-yearlife history patterns, some important differences developedbetween 1979 and 1981. The first generation hatches from overwinteringcysts in early spring and reaches maturity by the end of May.The first-generation females reproduce ovoviviparously, givingrise to a second generation which matures between mid-July andAugust. In July, both first and second generation females beginproducing overwintering cysts. The population reaches it maximumin late summer, then declines to low numbers by November. Theabundance of the first generation in June declined from a meanof 20 000 m2 to 2400 m2. Despite the smaller firstgeneration, the second generation in 1980 and 1981 was at leastas abundant as in 1979. These differences are indicative ofa change in the Artemia population dynamics in Mono Lake.
1Address for correspondence: Hawaii Institute of Marine Biology,University of Hawaii, P.O. Box 1346 Kaneohe, HI 96744-1346,USA. 相似文献
10.
Vladimír Křen Jiří Ludvík Olga Kofroňová Jaroslava Kozová Zdeněk Řeháček 《Applied microbiology and biotechnology》1987,26(3):219-226
Summary The 550-day semicontinuous cultivation of Claviceps fusiformis immobilized in calcium alginate is documented. The vegetative mycelium from seed or from early-production submerged culture is the best choice for immobilization. No extracellular glucans are produced by immobilized cells. Immobilized spores give low yields of clavine alkaloids. Alginate concentrations in a range of 2%–4% do not influence yield and spectrum of alkaloids. The cytoplasm of the immobilized cells becomes condensed (after 3 days), polysaccharides disappear, and centres of lipid synthesis are formed in the cytoplasm. After 60 days the cells harbour a great number of lipid particles, mitochondria are diminishing and their cristae partly disappear, indicating a decreased respiration capacity. After 350–500 days the volume of most cells is increased many times and the cells are filled with large oval bodies of electrondense material. Chloramphenicol protects immobilized cultures against bacterial contamination. 相似文献