全文获取类型
收费全文 | 125543篇 |
免费 | 146073篇 |
国内免费 | 32323篇 |
出版年
2021年 | 3401篇 |
2020年 | 2746篇 |
2019年 | 4986篇 |
2018年 | 4500篇 |
2017年 | 3727篇 |
2016年 | 4595篇 |
2015年 | 5886篇 |
2014年 | 6589篇 |
2013年 | 6898篇 |
2012年 | 8028篇 |
2011年 | 8098篇 |
2010年 | 7349篇 |
2009年 | 12036篇 |
2008年 | 6717篇 |
2007年 | 6430篇 |
2006年 | 4974篇 |
2005年 | 4779篇 |
2004年 | 4398篇 |
2003年 | 3748篇 |
2002年 | 4279篇 |
2001年 | 5383篇 |
2000年 | 2984篇 |
1999年 | 7621篇 |
1998年 | 9390篇 |
1997年 | 9565篇 |
1996年 | 8892篇 |
1995年 | 9132篇 |
1994年 | 8500篇 |
1993年 | 8090篇 |
1992年 | 8205篇 |
1991年 | 8173篇 |
1990年 | 8921篇 |
1989年 | 8114篇 |
1988年 | 7354篇 |
1987年 | 6445篇 |
1986年 | 5904篇 |
1985年 | 5366篇 |
1984年 | 4133篇 |
1983年 | 3331篇 |
1982年 | 3625篇 |
1981年 | 3264篇 |
1980年 | 3182篇 |
1979年 | 3301篇 |
1978年 | 3012篇 |
1977年 | 2929篇 |
1976年 | 2755篇 |
1974年 | 2480篇 |
1973年 | 2505篇 |
1972年 | 2833篇 |
1971年 | 2610篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Coordinate regulation of ribosomal protein mRNA level in regenerating rat liver. Study with the corresponding mouse cloned cDNAs. 总被引:17,自引:6,他引:11
下载免费PDF全文
![点击此处可从《Nucleic acids research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Cloned mouse ribosomal protein (rp) cDNAs exhibit extensive homology with the corresponding rat sequences. The size of the rp-mRNAs and complexity of the rp-genes are very similar in the two species. Using the mouse rp-recombinant DNAs we find that the relative abundance of rat L7, L13, L18, L30, L32/33 and S16 mRNAs increases after partial hepatectomy. Their maximal level is about twice that of normal rat liver, and is achieved 12-18 h after the operation, while the relative abundance of albumin mRNA decreases to half the normal values 12 h after partial hepatectomy. This concomitant increase in the relative content of these rp-mRNAs indicates coordinate regulation of their level in the rat. The dissimilar behavior of L10 and L19 rp-mRNA suggests additional control mechanisms of rp-mRNA levels in the regenerating rat liver. 相似文献
52.
The difficulty in predicting the consequences of interactions between different cytokine networks has increased with the expansion
of the T helper (Th) cell universe and the discovery of numerous B lymphocyte-derived cytokines. Consequently, it is now difficult
to conceptualize a straightforward view of the contribution of these disturbances to the pathogenesis of primary Sj?gren's
syndrome (SS). Th1 cells, which produce interferon-γ and IL-2, and Th17 cells, which make IL-17 and TNF-α, have been cast
in the leading roles of the play. However, the complex role of T-cell subsets in SS is accentuated by the reciprocal effects
of Th17 cells and regulatory T cells found in salivary glands of SS patients. Furthermore, B lymphocyte polarization into
type-1 B effector (Be1) and Be2 cells and B-cell modulating factors of the TNF family, most notably the B-cell-activating
factor (BAFF), and their prominent role in SS are additional complicating factors. Whereas Th17 cells orchestrate autoreactive
germinal centers, local BAFF would repress the generation of Th17 cells. Such new insights into interconnected cytokines in
primary SS may lead to new treatments for these patients. 相似文献
53.
54.
55.
56.
57.
The characteristics of the inducible galactose transport system in bakers' yeast were studied in uridine diphosphate, galactose-1-phosphate uridylyl-transferaseless cells. Transferaseless cells transport galactose at the same initial rate as wild-type cells and accumulate a mixture of free galactose and galactose-1-phosphate. The addition of 14C-labeled galactose to cells preloaded with unlabeled galactose and galactose-1-phosphate results in a higher rate of labeling of the free-sugar pool than of the galactose-1-phosphate pool. These results support other evidence that galactose uptake in bakers' yeast is a carrier-mediated, facilitated diffusion and that phosphorylation is an intracellular event after uptake of the free sugar. 相似文献
58.
59.
60.
The ultrastructure of the calcareous skeleton is described in twenty–one species of recent tubuliporine cyclostome bryozoans, using field emission SEM. The succession of skeletal fabrics in interior walls may be classified into four different fabric suites. The first–formed part of the calcitic skeleton in all species for which it has been observed is a precursory fabric of tiny, wedge–shaped crystallites. This is succeeded in about half of the species studied by a fabric of transverse fibres, followed by foliated fabric and often semi–nacre (fabric suite 1). Most of the remaining species lack transverse fibres and have interior walls largely comprising semi–nacre (fabric suite 2). A few species have skeletons consisting of predominantly distally–oriented, irregularly or regularly foliated fabric (fabric suite 3). A single species has a skeleton of proximally–oriented foliated fabric (fabric suite 4). Basal exterior walls in all species have a precursory fabric of tiny wedge–shaped crystallites without a strong preferred orientation, deposited directly upon the organic cuticle, followed by a layer of planar spherulitic structure, which in turn is succeeded by a similar fabric to that developed in the interior wall of the species concerned. Outermost layers of frontal exterior walls exhibit one of the following combinations of three fabrics: an outer layer of (1) finely granular or wedge–shaped crystallites; a thin dense granular layer followed by (2) distally accreting planar spherulitic fabric., or (3) obliquely accreting planar spherulitic fabric growing partly towards the midline of the frontal wall. Terminal diaphragms usually have outer layers dominated by planar spherulitic ultrastructure with centripetal growth directions. The fabric suites present in tubuliporines encompass most known fabrics found in the other cyclostome suborders and support the notion that this species–rich suborder occupies a central position in cyclostome evolution. 相似文献