全文获取类型
收费全文 | 1031篇 |
免费 | 98篇 |
出版年
2021年 | 10篇 |
2018年 | 11篇 |
2016年 | 19篇 |
2015年 | 24篇 |
2014年 | 26篇 |
2013年 | 57篇 |
2012年 | 50篇 |
2011年 | 39篇 |
2010年 | 25篇 |
2009年 | 27篇 |
2008年 | 42篇 |
2007年 | 60篇 |
2006年 | 27篇 |
2005年 | 38篇 |
2004年 | 29篇 |
2003年 | 46篇 |
2002年 | 44篇 |
2001年 | 18篇 |
2000年 | 11篇 |
1999年 | 16篇 |
1997年 | 16篇 |
1996年 | 9篇 |
1995年 | 14篇 |
1994年 | 9篇 |
1992年 | 11篇 |
1991年 | 11篇 |
1990年 | 16篇 |
1989年 | 9篇 |
1988年 | 10篇 |
1987年 | 14篇 |
1985年 | 15篇 |
1984年 | 12篇 |
1983年 | 10篇 |
1982年 | 18篇 |
1981年 | 15篇 |
1980年 | 11篇 |
1979年 | 16篇 |
1978年 | 9篇 |
1977年 | 11篇 |
1976年 | 14篇 |
1975年 | 16篇 |
1974年 | 13篇 |
1973年 | 14篇 |
1972年 | 21篇 |
1971年 | 20篇 |
1970年 | 15篇 |
1969年 | 10篇 |
1968年 | 18篇 |
1967年 | 10篇 |
1966年 | 7篇 |
排序方式: 共有1129条查询结果,搜索用时 15 毫秒
131.
Although rodent models are very popular for scientific studies, it is becoming more evident that large animal models can provide unique opportunities for biomedical research. Sheep are docile in nature and large in size, which facilitates surgical manipulation, and their physiology is similar to humans. As a result, for decades they have been chosen for several models and continue to be used to study an ever-increasing array of applications. Despite this, their full potential has not been exploited. Here, we review the use of sheep as an animal model for human vaccine development, asthma pathogenesis and treatment, the study of neonatal development, and the optimization of drug delivery and surgical techniques. 相似文献
132.
Prien JM Huysentruyt LC Ashline DJ Lapadula AJ Seyfried TN Reinhold VN 《Glycobiology》2008,18(5):353-366
In an effort to understand the role of molecular glycosylationin cancer a murine model has been used to characterize and fingerprintmalignancies in established cell lines that manifest all thehallmarks of metastatic disease: spontaneous development, localinvasion, intravasation, immune system survival, extravasation,and secondary tumor formation involving liver, kidney, spleen,lung, and brain. Using astrocyte cell controls, we comparedN-linked glycosylation from a nonmetastatic brain tumor cellline and two different metastatic brain tumor cells. Selectedions in each profile were disassembled by ion trap mass spectrometry(MSn) which exhibited multiple structural differences betweeneach tissue. These unique structures were identified withinisomeric compositions as pendant nonreducing termini of di-and trisaccharide fragments, probably transparent to a tandemMS approach but distinctively not to sequential ion trap MSndetection. 相似文献
133.
Helix aspersa hibernates in Brittany (western France), where it may experience subzero temperatures. Studies on cold hardiness, although scarce in land snails, have shown a seasonal variation in supercooling ability, associated with high temperatures of crystallization (Tc). In the present work, two key environmental factors, temperature and photoperiod, were studied to elucidate, how they may affect the enhancement of supercooling ability in the snails from the end of summer to winter. Nine groups of adult snails were acclimated to different combinations of photoperiod (LD-16:8, LD-12:12, and LD-8:16 h) and temperature (15, 10, and 5°C). Temperature of crystallization, hemolymph osmolality, and water content were measured. The results demonstrate a significant effect of the photoperiod on Tc, i.e., shorter photoperiods induce lower Tc (LD-16:8 h, mean Tc = −3.0°C, SD = 2.0; LD-12:12 h, mean Tc = −4.3°C, SD = 1.9; LD-8:16 h, mean Tc = −5.2°C, SD = 1.9; n = 90), whereas the acclimation temperature had no effect. Measurements of hemolymph osmolality and water content showed that osmolality is negatively correlated with water content. Mechanisms such as dehydration are involved in the decrease of Tc. A declining photoperiod triggers a lower Tc, long before the onset of winter conditions. This response may have an adaptive component, allowing individuals to cope with the mild winters typically observed in oceanic regions. 相似文献
134.
This study involved an investigation into the causes of limb injuries among the wild chimpanzees of the Budongo Forest, Uganda.
In view of the high incidence of limb injuries in this population, an attempt was made to diagnose the physiology of the diverse
range of deformities observed, and to provide a reliable assignment of causality. This enabled the authors to attribute 10
out of the 11 cases of limb abnormality to the wire snares and ‘leg-hold traps’ employed by communities living adjacent to
the forest. One example of congitals deformity is described. 相似文献
135.
Suzanne D Vernon Sanjay K Shukla Jennifer Conradt Elizabeth R Unger William C Reeves 《BMC microbiology》2002,2(1):39-6
Background
The association of an infectious agent with chronic fatigue syndrome (CFS) has been difficult and is further complicated by the lack of a known lesion or diseased tissue. Cell-free plasma DNA could serve as a sentinel of infection and disease occurring throughout the body. This type of systemic sample coupled with broad-range amplification of bacterial sequences was used to determine whether a bacterial pathogen was associated with CFS. Plasma DNA from 34 CFS and 55 non-fatigued subjects was assessed to determine plasma DNA concentration and the presence of bacterial 16S ribosomal DNA (rDNA) sequences. 相似文献136.
Matthias B. Van Hiel Bert Breugelmans Charles N. Pagel Adam K. Williams Aiden K. Varan Richard Burke Vernon M. Bowles Philip Batterham 《PloS one》2012,7(11)
Insecticide resistance has limited the number of available chemical options for insect pest control. Hence there is a need for new chemistries with novel modes of action. Here we investigate the mode of action for an insecticide that has not yet been released for commercial use. The ovicidal, larvacidal and adulticidal effects of 5,5′-dimethyl -2, 2′-dipyridyl (termed Ha44), which is being developed as a treatment for head lice, were evaluated in the Drosophila melanogaster model system. Ha44 demonstrated significant activity against embryos and was capable of arresting development at a number of stages of embryogenesis. The effects of Ha44 on embryos was shown to be reversible following the addition of the metal ions Fe(II) and Fe(III), Cu and Zn. When larvae were exposed to Ha44, lethality was recorded at similar concentrations to those observed for embryos. Using an eYFP reporter system it was shown that Ha44 was able to reduce the levels of both copper and zinc in the digestive tract, confirming the binding of Ha44 to these metals in vivo. Ha44 has further been shown to inhibit a zinc containing metalloproteinase in vitro. Exposure of adult flies to Ha44 resulted in lethality, but at higher concentrations than those observed for embryos and larvae. The median lethal dose in adult flies was shown to be associated with the type of exposure, with an LD-50 of 1.57 mM being recorded following the direct contact of flies with Ha44, while an LD-50 of 12.29 mM was recorded following the ingestion of the compound. The capacity of Ha44 to act on all stages of the life-cycle and potentially via a range of targets suggests that target site resistance is unlikely to evolve. 相似文献
137.
138.
139.
140.