全文获取类型
收费全文 | 1278篇 |
免费 | 114篇 |
专业分类
1392篇 |
出版年
2024年 | 4篇 |
2023年 | 12篇 |
2022年 | 17篇 |
2021年 | 40篇 |
2020年 | 28篇 |
2019年 | 36篇 |
2018年 | 25篇 |
2017年 | 27篇 |
2016年 | 46篇 |
2015年 | 75篇 |
2014年 | 82篇 |
2013年 | 79篇 |
2012年 | 143篇 |
2011年 | 97篇 |
2010年 | 55篇 |
2009年 | 44篇 |
2008年 | 48篇 |
2007年 | 56篇 |
2006年 | 42篇 |
2005年 | 40篇 |
2004年 | 30篇 |
2003年 | 32篇 |
2002年 | 25篇 |
2001年 | 26篇 |
2000年 | 21篇 |
1999年 | 13篇 |
1998年 | 11篇 |
1997年 | 10篇 |
1996年 | 9篇 |
1995年 | 10篇 |
1994年 | 11篇 |
1993年 | 13篇 |
1992年 | 17篇 |
1991年 | 12篇 |
1990年 | 16篇 |
1989年 | 14篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1971年 | 5篇 |
1887年 | 6篇 |
1886年 | 6篇 |
1885年 | 8篇 |
1884年 | 3篇 |
1883年 | 8篇 |
1882年 | 4篇 |
1875年 | 6篇 |
1874年 | 3篇 |
排序方式: 共有1392条查询结果,搜索用时 15 毫秒
101.
Acoustic signals transmit information by temporal characteristics and envelope periodicity as well as by their frequency content.
Many animals can extract the frequency content of a signal by means of specialized organs such as the cochlea but for the
detection and identification of higher-order periodicity, e.g., amplitude modulations, this type of organ is useless. In addition,
many animals do not have a cochlea but still depend on a reliable identification of different frequencies in the vast variety
of acoustic signals they perceive in their natural environment. Hence, neural mechanisms to decode periodicity information
must exist. We present a detailed mathematical analysis of a recurrent and a feedforward model of neuronal periodicity extraction
and discuss basic constraints for neuronal circuitry performing such a task in a biological system. Both the recurrent and
the feedforward model perform well using neuronal parameters typical for the auditory system. Performance is limited mainly
by the temporal precision of the connections between the neurons. 相似文献
102.
Hoppe CC Evans RG Bertram JF Moritz KM 《American journal of physiology. Regulatory, integrative and comparative physiology》2007,292(5):R1768-R1774
In rats, maternal protein restriction reduces nephron endowment and often leads to adult hypertension. Sex differences in these responses have been identified. The molecular and genetic bases of these phenomena can best be identified in a mouse model, but effects of maternal protein restriction on kidney development have not been examined in mice. Therefore, we determined how combined prenatal and postnatal protein restriction in mice affects organ weight, glomerular number and dimensions, and renal expression of angiotensin receptor mRNA, in both male and female offspring. C57/BL6/129sv mice received either a normal (20% wt/wt; NP) or low (9% wt/wt; LP) protein diet during gestation and postnatal life. Offspring were examined at postnatal day 30. Protein restriction retarded growth of the kidney, liver, spleen, heart, and brain. All organs except the brain weighed less in female than male offspring. Protein restriction increased normalized (to body weight) brain weight, with females having relatively heavier brains than males. The effects of protein restriction were not sex dependent, except that normalized liver weight was reduced in males but increased in females. Glomerular volume, but not number, was greater in female than in male mice. Maternal protein restriction reduced nephron endowment similarly in male and female mice. Renal expression of AT(1A) receptor mRNA was approximately sixfold greater in female than male NP mice, but similar in male LP and female LP mice. We conclude that maternal protein restriction reduces nephron endowment in mice. This effect provides a basis for future studies of developmental programming in the mouse. 相似文献
103.
Hoppe CC Evans RG Moritz KM Cullen-McEwen LA Fitzgerald SM Dowling J Bertram JF 《American journal of physiology. Regulatory, integrative and comparative physiology》2007,292(1):R462-R469
The effects of prenatal protein restriction on adult renal and cardiovascular function have been studied in considerable detail. However, little is known about the effects of life-long protein restriction, a common condition in the developing world. Therefore, we determined in rats the effects of combined pre- and postnatal protein restriction on adult arterial pressure and renal function and responses to increased dietary sodium. Nephron number was also determined. Male Sprague-Dawley rats were born to mothers fed a low [8% (wt/wt), LP] or normal [20% (wt/wt), NP] isocaloric protein diet throughout pregnancy and maintained on these diets after birth. At postnatal day 135, nephron number, mean arterial pressure (MAP), and renal function were determined. A high-NaCl [8.0% (wt/wt), high-salt] diet was fed to a subset of rats from weaning. MAP was less in LP than in NP rats (120 +/- 2 vs. 128 +/- 2 mmHg, P < 0.05) and was not significantly altered by increased salt intake. Nephron number was 31% less in LP than in NP rats (P < 0.001). The volume of individual glomeruli was also less in LP than in NP rats, as were calculated effective renal plasma flow and glomerular filtration rate. Glomerular filtration rate, but not effective renal plasma flow, appeared to be increased by high salt intake, particularly in LP rats. In conclusion, protein restriction induced a severe nephron deficit, but MAP was lower, rather than higher, in protein-restricted than in control rats in adulthood. These findings indicate that the postnatal environment plays a key role in determining the outcomes of developmental programming. 相似文献
104.
Egbertson MS Moritz HM Melamed JY Han W Perlow DS Kuo MS Embrey M Vacca JP Zrada MM Cortes AR Wallace A Leonard Y Hazuda DJ Miller MD Felock PJ Stillmock KA Witmer MV Schleif W Gabryelski LJ Moyer G Ellis JD Jin L Xu W Braun MP Kassahun K Tsou NN Young SD 《Bioorganic & medicinal chemistry letters》2007,17(5):1392-1398
A 1,6-naphthyridine inhibitor of HIV-1 integrase has been discovered with excellent inhibitory activity in cells, good pharmacokinetics, and an excellent ability to inhibit virus with mutant enzyme. 相似文献
105.
Max Bylesjö Daniel Eriksson Andreas Sjödin Stefan Jansson Thomas Moritz Johan Trygg 《BMC bioinformatics》2007,8(1):207
Background
During generation of microarray data, various forms of systematic biases are frequently introduced which limits accuracy and precision of the results. In order to properly estimate biological effects, these biases must be identified and discarded. 相似文献106.
107.
108.
Auxotrophy and intrapopulation complementary in the ‘interactome’ of a cultivated freshwater model community 下载免费PDF全文
Sarahi L. Garcia Moritz Buck Katherine D. McMahon Hans‐Peter Grossart Alexander Eiler Falk Warnecke 《Molecular ecology》2015,24(17):4449-4459
Microorganisms are usually studied either in highly complex natural communities or in isolation as monoclonal model populations that we manage to grow in the laboratory. Here, we uncover the biology of some of the most common and yet‐uncultured bacteria in freshwater environments using a mixed culture from Lake Grosse Fuchskuhle. From a single shotgun metagenome of a freshwater mixed culture of low complexity, we recovered four high‐quality metagenome‐assembled genomes (MAGs) for metabolic reconstruction. This analysis revealed the metabolic interconnectedness and niche partitioning of these naturally dominant bacteria. In particular, vitamin‐ and amino acid biosynthetic pathways were distributed unequally with a member of Crenarchaeota most likely being the sole producer of vitamin B12 in the mixed culture. Using coverage‐based partitioning of the genes recovered from a single MAG intrapopulation metabolic complementarity was revealed pointing to ‘social’ interactions for the common good of populations dominating freshwater plankton. As such, our MAGs highlight the power of mixed cultures to extract naturally occurring ‘interactomes’ and to overcome our inability to isolate and grow the microbes dominating in nature. 相似文献
109.
110.
Raimondi A Ferguson SM Lou X Armbruster M Paradise S Giovedi S Messa M Kono N Takasaki J Cappello V O'Toole E Ryan TA De Camilli P 《Neuron》2011,70(6):1100-1114
The existence of neuron-specific endocytic protein isoforms raises questions about their importance for specialized neuronal functions. Dynamin, a GTPase implicated in the fission reaction of endocytosis, is encoded by three genes, two of which, dynamin 1 and 3, are highly expressed in neurons. We show that dynamin 3, thought to play a predominantly postsynaptic role, has a major presynaptic function. Although lack of dynamin 3 does not produce an overt phenotype in mice, it worsens the dynamin 1 KO phenotype, leading to perinatal lethality and a more severe defect in activity-dependent synaptic vesicle endocytosis. Thus, dynamin 1 and 3, which together account for the overwhelming majority of brain dynamin, cooperate in supporting optimal rates of synaptic vesicle endocytosis. Persistence of synaptic transmission in their absence indicates that if dynamin plays essential functions in neurons, such functions can be achieved by the very low levels of dynamin 2. 相似文献