全文获取类型
收费全文 | 103843篇 |
免费 | 1233篇 |
国内免费 | 821篇 |
出版年
2023年 | 44篇 |
2022年 | 67篇 |
2021年 | 186篇 |
2020年 | 123篇 |
2019年 | 121篇 |
2018年 | 11966篇 |
2017年 | 10789篇 |
2016年 | 7711篇 |
2015年 | 1060篇 |
2014年 | 806篇 |
2013年 | 977篇 |
2012年 | 5038篇 |
2011年 | 13593篇 |
2010年 | 12460篇 |
2009年 | 8674篇 |
2008年 | 10394篇 |
2007年 | 11999篇 |
2006年 | 924篇 |
2005年 | 1084篇 |
2004年 | 1543篇 |
2003年 | 1580篇 |
2002年 | 1358篇 |
2001年 | 412篇 |
2000年 | 300篇 |
1999年 | 197篇 |
1998年 | 188篇 |
1997年 | 156篇 |
1996年 | 122篇 |
1995年 | 132篇 |
1994年 | 119篇 |
1993年 | 138篇 |
1992年 | 141篇 |
1991年 | 115篇 |
1990年 | 84篇 |
1989年 | 59篇 |
1988年 | 76篇 |
1987年 | 47篇 |
1986年 | 45篇 |
1985年 | 56篇 |
1984年 | 43篇 |
1983年 | 51篇 |
1982年 | 46篇 |
1981年 | 35篇 |
1980年 | 26篇 |
1979年 | 30篇 |
1977年 | 31篇 |
1976年 | 25篇 |
1972年 | 252篇 |
1971年 | 283篇 |
1962年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
141.
Background
Meiotic prophase is a critical stage in sexual reproduction. Aberrant chromosome recombination during this stage is a leading cause of human miscarriages and birth defects. However, due to the experimental intractability of mammalian gonads, only a very limited number of meiotic genes have been characterized. Here we aim to identify novel meiotic genes important in human reproduction through computational mining of cross-species and cross-sex time-series expression data from budding yeast, mouse postnatal testis, mouse embryonic ovary, and human fetal ovary. 相似文献142.
Kasper Stovgaard Christian Andreetta Jesper Ferkinghoff-Borg Thomas Hamelryck 《BMC bioinformatics》2010,11(1):429
Background
Genome sequencing projects have expanded the gap between the amount of known protein sequences and structures. The limitations of current high resolution structure determination methods make it unlikely that this gap will disappear in the near future. Small angle X-ray scattering (SAXS) is an established low resolution method for routinely determining the structure of proteins in solution. The purpose of this study is to develop a method for the efficient calculation of accurate SAXS curves from coarse-grained protein models. Such a method can for example be used to construct a likelihood function, which is paramount for structure determination based on statistical inference. 相似文献143.
Siddhartha Kumar Bhaumik Manoj Kumar Singh Subir Karmakar Tripti De 《Glycoconjugate journal》2009,26(6):663-673
As compared to cutaneous leishmaniasis, vaccination against visceral leishmaniasis (VL) has received limited attention. In
this study, we demonstrate for the first time that an UDP-Galactose: N-acetylglucosamine β 1–4 galactosyltransferase (GenBank Accession No. EF159943) expressing attenuated LD clonal population (A-LD) is able to confer protection against the experimental challenge with the virulent LD AG83 parasite. A-LD was also effective in established leishmania infection. The vaccinated animals showed both cell mediated
(in vitro T-cell proliferation, and DTH response) and humoral responses (Th1 type). These results demonstrate the potential of the
attenuated clones as an immunotherapeutic and immunoprophylactic agent against visceral leishmaniasis. 相似文献
144.
Summary The specificity of interaction of amino acids with triplets in the acceptor helix stem of tRNA was investigated by means of a statistical analysis of 1400 tRNA sequences. The imprint of a prototypic genetic code at position 3–5 of the acceptor helix was detected, but only for those major amino acids, glycine, alanine, aspartic acid, and valine, that are formed by spark discharges of simple gases in the laboratory. Although remnants of the code at position 3–5 are typical for tRNAs of archaebacteria, eubacteria, and chloroplasts, eukaryotes do not seem to contain this code, and mitochondria take up an intermediary position. A duplication mechanism for the transposition of the original 3–5 code toward its present position in the anticodon stern of tRNA is proposed. From this viewpoint, the mode of evolution of mRNA and functional ribosomes becomes more understandable.Offprint requests to: W. Moller 相似文献
145.
146.
Mamta Singhvi Dipti Joshi Shalaka Gaikaiwari Digambar V. Gokhale 《Indian journal of microbiology》2010,50(1):97-100
Method for production and regeneration of Lactobacillus delbrueckii protoplasts are described. The protoplasts were obtained by treatment with a mixture of lysozyme and mutanolysin in protoplast
buffer at pH 6.5 with different osmotic stabilizers. The protoplasts were regenerated on deMan, Rogosa and Sharpe (MRS) with
various osmotic stabilizers. Maximum protoplast formation was obtained in protoplast buffer with sucrose as an osmotic stabilizer
using a combination of lysozyme (1 mg/ml) and mutanolysin (10 μg/ml). Maximum protoplast regeneration was obtained on MRS
medium with sucrose (0.5 M) as an osmotic stabilizer. The regeneration medium was also applicable to other species of lactobacilli
as well. This is, to our knowledge, the first report on protoplast formation and efficient regeneration in case of L. delbrueckii. 相似文献
147.
It is generally perceived that landscape patterns or textures in a given protected area are spatially stationary. The findings
of this study suggest that this common perception is only partially correct. Over the course of 52 years, equilibrium in landscape
shifting was detected using digital data for the Lassen Volcanic National Park (USA). Vertical aerial photographs taken of
the park in 1941 were geo-referenced with the digital orthophoto quarter quadrangle (DOQQ) images of the same area from 1993
to identify landscape compositions and to measure change. Spatial analysis was used to observe pattern changes over time.
The results suggested that landscape development maintained equilibrium while patches were in various stages of a successional
sequence. The total area of each landscape component held steady, although over time patches throughout the landscape changed—a
shifting-mosaic steady state (SMSS). These findings reflect the limitations of contemporary environmental conservation theory.
They also suggest the importance of considering landscape change in policies that currently govern park planning and management. 相似文献
148.
Pierre Fellmann Jens Andersen Philippe F. Devaux Marc le Maire Alain Bienvenue 《Biochemical and biophysical research communications》1980,95(1):289-295
A spin labeled fatty acid (16-doxylstearic acid) was linked to a photochemical reacting group (azido derivative). When the molecule is introduced, at a low concentration, into rabbit sarcoplasmic reticulum membranes, the spectrum before illumination is identical to the spectrum obtained with the corresponding spin labeled fatty acid. After illumination, a large immobilized components is seen. It corresponds to about 70% of the ESR signal of the effectively bound label, at room temperature. The fraction of immobilized component varies with temperature, from 100% at 0°C to 50% at 35°C. Addition of a small amount of detergent (dodecyl octaethylene glycol monoether), under non solubilizing conditions, decreases the fraction of signal due to a strongly immobilized probe. A possible interpretation is that the immobilized signal reflects protein bound spin labels trapped in Ca2+ ATPase oligomers, which are partially dissociated by detergent addition or temperature increase. 相似文献
149.
150.
James A. Simmons Andrea Megela Simmons 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2011,197(5):585-594
Widely divergent vertebrates share a common central temporal mechanism for representing periodicities of acoustic waveform
events. In the auditory nerve, periodicities corresponding to frequencies or rates from about 10 Hz to over 1,000 Hz are extracted
from pure tones, from low-frequency complex sounds (e.g., 1st harmonic in bullfrog calls), from mid-frequency sounds with
low-frequency modulations (e.g., amplitude modulation rates in cat vocalizations), and from time intervals between high-frequency
transients (e.g., pulse-echo delay in bat sonar). Time locking of neuronal responses to periodicities from about 50 ms down
to 4 ms or less (about 20–300 Hz) is preserved in the auditory midbrain, where responses are dispersed across many neurons
with different onset latencies from 4–5 to 20–50 ms. Midbrain latency distributions are wide enough to encompass two or more
repetitions of successive acoustic events, so that responses to multiple, successive periods are ongoing simultaneously in
different midbrain neurons. These latencies have a previously unnoticed periodic temporal pattern that determines the specific
times for the dispersed on-responses. 相似文献