全文获取类型
收费全文 | 43380篇 |
免费 | 3314篇 |
国内免费 | 50篇 |
出版年
2022年 | 164篇 |
2021年 | 704篇 |
2020年 | 399篇 |
2019年 | 579篇 |
2018年 | 789篇 |
2017年 | 742篇 |
2016年 | 1252篇 |
2015年 | 1811篇 |
2014年 | 1862篇 |
2013年 | 2734篇 |
2012年 | 2574篇 |
2011年 | 2509篇 |
2010年 | 1951篇 |
2009年 | 1775篇 |
2008年 | 2287篇 |
2007年 | 2300篇 |
2006年 | 2207篇 |
2005年 | 2130篇 |
2004年 | 1857篇 |
2003年 | 1799篇 |
2002年 | 1712篇 |
2001年 | 445篇 |
2000年 | 387篇 |
1999年 | 448篇 |
1998年 | 538篇 |
1997年 | 398篇 |
1996年 | 337篇 |
1995年 | 298篇 |
1994年 | 335篇 |
1993年 | 311篇 |
1992年 | 309篇 |
1991年 | 273篇 |
1990年 | 264篇 |
1989年 | 240篇 |
1988年 | 257篇 |
1987年 | 247篇 |
1986年 | 224篇 |
1985年 | 307篇 |
1984年 | 394篇 |
1983年 | 319篇 |
1982年 | 379篇 |
1981年 | 444篇 |
1980年 | 423篇 |
1979年 | 256篇 |
1978年 | 262篇 |
1977年 | 277篇 |
1976年 | 266篇 |
1975年 | 186篇 |
1974年 | 236篇 |
1973年 | 194篇 |
排序方式: 共有10000条查询结果,搜索用时 687 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.
In vivo EMG biofeedback was found to be an effective pedagogical tool for removing unwanted left-hand tension in nine violin and viola players. Improvement occurred rapidly and persisted throughout a 5-month follow-up period. Further studies will be necessary to assess the effect of biofeedback independent of placebo effects. The brevity of the method and the magnitude of improvement warrant further investigation. 相似文献
3.
The ability to metabolically label proteins with 35S-methionine is critical for the analysis of protein synthesis and turnover. Despite the importance of this approach, however, efficient labeling of proteins in vivo is often limited by a low number of available methionine residues, or by deleterious side-effects associated with protein overexpression. To overcome these limitations, we have created a methionine-rich variant of the widely used HA tag, called HAM, for use with ectopically expressed proteins. Here we describe the development of a series of vectors, and corresponding antisera, for the expression and detection of HAM-tagged proteins in mammalian cells. We show that the HAM tag dramatically improves the sensitivity of 35S-methionine labeling, and permits the analysis of Myc oncoprotein turnover even when HAM-tagged Myc is expressed at levels comparable to that of the endogenous protein. Because of the improved sensitivity provided by the HAM tag, the vectors and antisera described here should be useful for the analysis of protein synthesis and destruction at physiological levels of protein expression. 相似文献
4.
I. N. Semenchuk L. A. Taranova A. A. Kalenyuk P. V. Il’yasov A. N. Reshetilov 《Applied Biochemistry and Microbiology》2000,36(1):69-72
The operating and storage stability of a receptor element of an amperometric biosensor based on thePseudomonas rathonis strain T capable of degrading surfactants was tested. Microbial cells were immobilized by incorporation in gels (agar, agarose,
and calcium-alginate), polyvinyl alcohol membrane, adhesion to Chromatographic paper GF/A, or by cross-linking induced by
glutaric aldehyde. Incorporation of microbial cells in agar gel provides long-standing conservation of their activity and
viability during measurements of high concentrations of surfactants and allows the receptor element of the biosensor to be
rapidly recovered after measurements. 相似文献
5.
S. I. Tkachenko A. R. Mingaleev V. M. Romanova A. E. Ter-Oganes’yan T. A. Shelkovenko S. A. Pikuz 《Plasma Physics Reports》2009,35(9):734-753
Distribution of matter in the discharge channel formed upon a nanosecond electrical explosion of a single wire in air and
vacuum was studied experimentally. Simultaneous use of optical, UV, and X-ray diagnostics made it possible to distinguish
qualitatively different regions of the discharge channel, such as the current-carrying layers and the region occupied by a
weakly conducting cold plasma. Several series of experiments with 25-μm-diameter 12-mm-long wires made of different materials
were performed. The charging voltage and the current amplitude were varied in the ranges of U
0 = 10–20 kV and I
max ∼ 5–10 kA, respectively. Explosion regimes with a current pause and with and without current interruption, as well as with
wire preheating in air and vacuum, were studied. Shadow and schlieren images of the discharge channel were obtained using
optical probing at the second harmonic of a YAG: Nd+3 laser (λ = 0.532 μm, τ ∼ 10 ns). In the experiments carried out in vacuum, X-ray images of the discharge channel were also
obtained using an X-pinch as a point source of probing radiation and UV images were recorded using a four-frame MCP camera. 相似文献
6.
A. V. Nikolayev Yu. V. Kirichek O. I. Ostrovskaya I. I. Maletina K. I. Petko L. M. Yagupol’skii 《Neurophysiology》1999,31(3):191-193
With the use of a patch-clamp technique in the whole-cell configuration, we studied the effects of pinacidil and its fluorine
derivatives on A-type potassium current (I
A) through the membrane of pyramidal neurons of the rat hippocampus. Hydrogen peroxide (10 mM) exerted no influence on the
rate of inactivation ofI
A; therefore, this current is probably mediated by Shal Kv4.2 potassium channels. Pinacidil demonstrated the properties of
a weakI
A blocker: in the 500 μM concentration it blocked about 45% of the current, while 50 μM of pinacidil fluorine derivatives were
capable of blocking up to 30% ofI
A. The effects of pinacidil and its derivatives showed no dependence on the stimulating potential. A similar pattern of the
effects of pinacidil fluorine derivatives, which are an order of magnitude stronger than those of pinacidil itself, allows
us to suppose that the imine nitrogen of the tested compounds is significantly more involved in the molecular interaction
with the site of an A-type potassium channel than the pyridine nitrogen. 相似文献
7.
8.
HIF-1 expression in healing wounds: HIF-1alpha induction in primary inflammatory cells by TNF-alpha 总被引:12,自引:0,他引:12
9.
10.