全文获取类型
收费全文 | 9633篇 |
免费 | 1303篇 |
专业分类
10936篇 |
出版年
2023年 | 47篇 |
2022年 | 119篇 |
2021年 | 199篇 |
2020年 | 120篇 |
2019年 | 159篇 |
2018年 | 184篇 |
2017年 | 140篇 |
2016年 | 265篇 |
2015年 | 444篇 |
2014年 | 504篇 |
2013年 | 544篇 |
2012年 | 774篇 |
2011年 | 744篇 |
2010年 | 507篇 |
2009年 | 409篇 |
2008年 | 579篇 |
2007年 | 614篇 |
2006年 | 610篇 |
2005年 | 606篇 |
2004年 | 540篇 |
2003年 | 466篇 |
2002年 | 473篇 |
2001年 | 125篇 |
2000年 | 119篇 |
1999年 | 137篇 |
1998年 | 99篇 |
1997年 | 72篇 |
1996年 | 62篇 |
1995年 | 59篇 |
1994年 | 61篇 |
1993年 | 58篇 |
1992年 | 101篇 |
1991年 | 55篇 |
1990年 | 59篇 |
1989年 | 59篇 |
1988年 | 54篇 |
1987年 | 60篇 |
1986年 | 57篇 |
1985年 | 51篇 |
1984年 | 37篇 |
1983年 | 39篇 |
1982年 | 29篇 |
1981年 | 34篇 |
1980年 | 44篇 |
1979年 | 48篇 |
1978年 | 29篇 |
1977年 | 25篇 |
1976年 | 28篇 |
1975年 | 25篇 |
1974年 | 41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.
Nicole LeBrasseur 《The Journal of cell biology》2003,162(6):958-959
3.
Proteins in the molecular weight range of 10 000–170 000 were separated by high performance gel permeation chromatography. Silica particles with 30 nm or 50 nm pores were derivatized with glycidoxy-propyltrimethoxysilane and used as support. The proteins were eluted with 50% formic acid. A protein fraction which induces endodermal and mesodermal tissues in amphibian gastrula ectoderm was purified by this method. 相似文献
4.
Thomas A. Worthington Shannon K. Brewer Nicole Farless Timothy B. Grabowski Mark S. Gregory 《PloS one》2014,9(5)
Habitat fragmentation and flow regulation are significant factors related to the decline and extinction of freshwater biota. Pelagic-broadcast spawning cyprinids require moving water and some length of unfragmented stream to complete their life cycle. However, it is unknown how discharge and habitat features interact at multiple spatial scales to alter the transport of semi-buoyant fish eggs. Our objective was to assess the relationship between downstream drift of semi-buoyant egg surrogates (gellan beads) and discharge and habitat complexity. We quantified transport time of a known quantity of beads using 2–3 sampling devices at each of seven locations on the North Canadian and Canadian rivers. Transport time was assessed based on median capture time (time at which 50% of beads were captured) and sampling period (time period when 2.5% and 97.5% of beads were captured). Habitat complexity was assessed by calculating width∶depth ratios at each site, and several habitat metrics determined using analyses of aerial photographs. Median time of egg capture was negatively correlated to site discharge. The temporal extent of the sampling period at each site was negatively correlated to both site discharge and habitat-patch dispersion. Our results highlight the role of discharge in driving transport times, but also indicate that higher dispersion of habitat patches relates to increased retention of beads within the river. These results could be used to target restoration activities or prioritize water use to create and maintain habitat complexity within large, fragmented river systems. 相似文献
5.
6.
7.
8.
9.
Molecular mechanisms of ceramide-mediated CD95 clustering. 总被引:2,自引:0,他引:2
H Grassmé H Schwarz E Gulbins 《Biochemical and biophysical research communications》2001,284(4):1016-1030
Receptor clustering has been suggested as a crucial mechanism to initiate receptor signaling. Here we show that ceramide in sphingolipid-rich membrane rafts mediates clustering of CD95. Neutralization of surface ceramide or inhibition of its endogenous generation prevented CD95 clustering. Furthermore, application of ceramide at the cell surface triggered clustering of active but not inactive CD95. Apoptosis was inhibited by neutralization of surface ceramide or inhibition of ceramide release in vitro and in vivo. Thus, we conclude that surface ceramide mediates CD95 clustering, which is required for initiation of apoptosis, at least in some cell types. 相似文献
10.
Antoine Wystrach Sebastian Schwarz Patrick Schultheiss Guy Beugnon Ken Cheng 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2011,197(2):167-179
The Australian desert ant Melophorus bagoti often follows stereotypical routes through a cluttered landscape containing both distant panoramic views and obstacles (plants)
to navigate around. We created an artificial obstacle course for the ants between a feeder and their nest. Landmarks comprised
natural objects in the landscape such as logs, branches, and tussocks. Many ants travelled stereotypical routes home through
the obstacle course in training, threading repeatedly the same gaps in the landmarks. Manipulations altering the relations
between the landmarks and the surrounding panorama, however, affected the routes in two major ways. Both interchanging the
positions of landmarks (transpositions) and displacing the entire landmark set along with the starting position of the ants
(translations) (1) reduced the stereotypicality of the route, and (2) increased turns and meanders during travel. The ants
might have used the entire panorama in view-based travel, or the distal panorama might prime the identification and use of
landmarks en route. Despite the large data set, both options (not mutually exclusive) remain viable. 相似文献