全文获取类型
收费全文 | 22320篇 |
免费 | 1846篇 |
国内免费 | 424篇 |
出版年
2022年 | 308篇 |
2021年 | 554篇 |
2020年 | 357篇 |
2019年 | 427篇 |
2018年 | 446篇 |
2017年 | 369篇 |
2016年 | 634篇 |
2015年 | 1009篇 |
2014年 | 1110篇 |
2013年 | 1394篇 |
2012年 | 1619篇 |
2011年 | 1570篇 |
2010年 | 996篇 |
2009年 | 848篇 |
2008年 | 1197篇 |
2007年 | 1124篇 |
2006年 | 1015篇 |
2005年 | 1012篇 |
2004年 | 943篇 |
2003年 | 842篇 |
2002年 | 832篇 |
2001年 | 284篇 |
2000年 | 283篇 |
1999年 | 258篇 |
1998年 | 254篇 |
1997年 | 192篇 |
1996年 | 181篇 |
1995年 | 150篇 |
1994年 | 154篇 |
1993年 | 136篇 |
1992年 | 186篇 |
1991年 | 162篇 |
1990年 | 158篇 |
1989年 | 131篇 |
1988年 | 122篇 |
1987年 | 151篇 |
1986年 | 131篇 |
1985年 | 118篇 |
1984年 | 156篇 |
1983年 | 119篇 |
1982年 | 148篇 |
1981年 | 142篇 |
1980年 | 166篇 |
1979年 | 137篇 |
1978年 | 122篇 |
1977年 | 129篇 |
1976年 | 95篇 |
1975年 | 102篇 |
1974年 | 107篇 |
1973年 | 95篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Based on its proven anabolic effects on bone in osteoporosis patients, recombinant parathyroid hormone (PTH1-34) has been evaluated as a potential therapy for skeletal repair. In animals, the effect of PTH1-34 has been investigated in various skeletal repair models such as fractures, allografting, spinal arthrodesis and distraction
osteogenesis. These studies have demonstrated that intermittent PTH1-34 treatment enhances and accelerates the skeletal repair process via a number of mechanisms, which include effects on mesenchymal
stem cells, angiogenesis, chondrogenesis, bone formation and resorption. Furthermore, PTH1-34 has been shown to enhance bone repair in challenged animal models of aging, inflammatory arthritis and glucocorticoid-induced
bone loss. This pre-clinical success has led to off-label clinical use and a number of case reports documenting PTH1-34 treatment of delayed-unions and non-unions have been published. Although a recently completed phase 2 clinical trial of PTH1-34 treatment of patients with radius fracture has failed to achieve its primary outcome, largely because of effective healing
in the placebo group, several secondary outcomes are statistically significant, highlighting important issues concerning the
appropriate patient population for PTH1-34 therapy in skeletal repair. Here, we review our current knowledge of the effects of PTH1-34 therapy for bone healing, enumerate several critical unresolved issues (e.g., appropriate dosing regimen and indications)
and discuss the long-term potential of this drug as an adjuvant for endogenous tissue engineering. 相似文献
2.
3.
4.
5.
The ultrastructure of the interstitial cells of Cajal (ICC) in the oesophagus of the monkey resembled that described in the oesophagus of other mammalian species but differed in their paucity and almost lack of smooth endoplasmic reticulum, caveolae and filaments. The plasmalemma of the ICC was in close contact (20- to 30-nm gaps) with that of smooth muscle cells. This may occasionally take the form of a desmosome, but gap junctions have not been observed. Vesiculated axon profiles, containing large granular or agranular vesicles were in close contact (20- to 30-nm gaps) with the plasmalemma of ICC. In a few vesiculated profiles a presynaptic density could be recognized. The intercalation of the ICC between the vesiculated axon profiles and the smooth muscle cells suggest a role in oesophageal motility. Between 3 and 21 days following bilateral vagotomy some ICC showed regressive changes such as increased electron density and shrinkage of the cytoplasm, crowding of the organelles and dissolution of the nuclear chromatin material. Axon profiles in the vicinity of the affected ICC contained glycogen granules suggesting injury. In late stages, the number of ICC and smooth muscle contacts was reduced. The results suggest that the vagus nerves exert a trophic influence on the ICC and that the intercellular relationships between ICC and smooth muscle cells possess a degree of plasticity. It is tentatively suggested that these vagal effects may be mediated via the oesophageal myenteric ganglia. 相似文献
6.
Edward Harrison 《BMJ (Clinical research ed.)》1916,1(2888):645-647
7.
Transcriptional regulatory network triggered by oxidative signals configures the early response mechanisms of japonica rice to chilling stress 总被引:3,自引:0,他引:3
8.
以半矮秆育种为代表的“绿色革命”极大地提高了作物产量,但也带来氮营养利用效率降低的严重问题。“绿色革命”主要基于调控赤霉素的代谢和信号转导而实现。前期的研究发现,赤霉素信号转导关键因子DELLA蛋白通过调控GRF4而负调控氮素的吸收利用,为半矮秆品系氮利用效率低的问题提供了解决方案。最近的一项研究进一步揭示了GA信号途径与氮响应交叉互作的新机制。该研究发现水稻(Oryza sativa)NGR5是氮素调控分蘖数目的一个关键基因,其表达受氮诱导。通过招募PRC2,NGR5对D14和OsSPL14等分蘖抑制基因所在位点进行H3K27me3甲基化修饰,从而抑制其表达。而在半矮秆背景下超表达NGR5可以提高低氮水平下的水稻产量。NGR5同时也被发现为赤霉素受体GID1的一个新靶标,受到其负调控。该研究发现了调控赤霉素信号通路的新机制,并对高产高效的新一代“绿色革命”育种实践具有重要启示。 相似文献
9.
10.