全文获取类型
收费全文 | 2076篇 |
免费 | 208篇 |
国内免费 | 1篇 |
专业分类
2285篇 |
出版年
2022年 | 9篇 |
2021年 | 26篇 |
2019年 | 10篇 |
2018年 | 13篇 |
2017年 | 9篇 |
2016年 | 27篇 |
2015年 | 56篇 |
2014年 | 67篇 |
2013年 | 78篇 |
2012年 | 119篇 |
2011年 | 109篇 |
2010年 | 86篇 |
2009年 | 82篇 |
2008年 | 111篇 |
2007年 | 130篇 |
2006年 | 110篇 |
2005年 | 110篇 |
2004年 | 107篇 |
2003年 | 91篇 |
2002年 | 134篇 |
2001年 | 32篇 |
2000年 | 34篇 |
1999年 | 40篇 |
1998年 | 29篇 |
1997年 | 22篇 |
1996年 | 18篇 |
1995年 | 35篇 |
1994年 | 22篇 |
1993年 | 22篇 |
1992年 | 35篇 |
1991年 | 32篇 |
1990年 | 31篇 |
1989年 | 41篇 |
1988年 | 35篇 |
1987年 | 33篇 |
1986年 | 32篇 |
1985年 | 28篇 |
1984年 | 24篇 |
1983年 | 21篇 |
1982年 | 21篇 |
1981年 | 23篇 |
1980年 | 17篇 |
1979年 | 22篇 |
1978年 | 19篇 |
1977年 | 15篇 |
1976年 | 16篇 |
1975年 | 12篇 |
1974年 | 15篇 |
1973年 | 14篇 |
1971年 | 11篇 |
排序方式: 共有2285条查询结果,搜索用时 15 毫秒
91.
Hamill RW Tompkins JD Girard BM Kershen RT Parsons RL Vizzard MA 《Developmental neurobiology》2012,72(6):918-936
Although often overshadowed by the motor dysfunction associated with Parkinson's disease (PD), autonomic dysfunction including urinary bladder and bowel dysfunctions are often associated with PD and may precede motoric changes; such autonomic dysfunction may permit early detection and intervention. Lower urinary tract symptoms are common in PD patients and result in significant morbidity. This studies focus on nonmotor symptoms in PD using a transgenic mouse model with overexpression of human α-synuclein (hSNCA), the peptide found in high concentrations in Lewy body neuronal inclusions, the histopathologic hallmark of PD. We examined changes in the physiological, molecular, chemical, and electrical properties of neuronal pathways controlling urinary bladder function in transgenic mice. The results of these studies reveal that autonomic dysfunction (i.e., urinary bladder) can precede motor dysfunction. In addition, mice with hSNCA overexpression in relevant neuronal populations is associated with alterations in expression of neurotransmitter/neuromodulatory molecules (PACAP, VIP, substance P, and neuronal NOS) within neuronal pathways regulating bladder function as well as with increased NGF expression in the urinary bladder. Changes in the electrical and synaptic properties of neurons in the major pelvic ganglia that provide postganglionic innervation to urogenital tissues were not changed as determined with intracellular recording. The urinary bladder dysfunction observed in transgenic mice likely reflects changes in peripheral (i.e., afferent) and/or central micturition pathways or changes in the urinary bladder. SYN-OE mice provide an opportunity to examine early events underlying the molecular and cellular plasticity of autonomic nervous system pathways underlying synucleinopathies. 相似文献
92.
Kyoung Min Lee Tae-Woo Kim Robert N. Weinreb Eun Ji Lee Micha?l J. A. Girard Jean Martial Mari 《PloS one》2014,9(12)
PurposeTo determine using swept-source optical coherence tomography (SS-OCT) whether there are differences in the location of the anterior lamina cribrosa insertion (ALI) in primary open-angle glaucoma (POAG) patients and healthy subjects.MethodsFifty three eyes from 53 patients with POAG, and 53 eyes from 53 age-matched healthy subjects were included prospectively in Seoul National University Bundang Hospital. Twelve radial line B-scans centered on the optic disc in every half-clock-hour meridian were acquired using SS-OCT. The ALI position was assessed by measuring two parameters: (1) ALI distance (ALID)—the distance from the anterior scleral canal opening (ASCO) to the ALI; and (2) marginal anterior lamina cribrosa surface depth (mALCSD)—the perpendicular distance from the ASCO plane to the anterior lamina cribrosa surface. These parameters were compared between the two groups for each meridian.ResultsBoth ALID (256±54 vs. 209±37 µm, mean ± SD, p<0.001) and mALCSD (232±63 vs. 187±40 µm, p<0.001) were significantly greater in the POAG group than in the normal group. The largest difference was observed at the 6.5 o′clock and 11.5 o′clock meridians for both ALID and mALCSD. Multiple regression analysis revealed a negative correlation between age and both ALID and mALCSD in the control group, and a negative correlation between mean deviation of the visual field test and both ALID and mALCSD in the POAG group.ConclusionsThe ALI was displaced posteriorly in eyes with POAG compared to those of healthy controls. This finding suggests that the posteriorly located lamina cribrosa insertion is an important component of glaucomatous optic nerve excavation. 相似文献
93.
Jair E. Garcia Madeline B. Girard Michael Kasumovic Phred Petersen Philip A. Wilksch Adrian G. Dyer 《PloS one》2015,10(5)
Background
The ability to discriminate between two similar or progressively dissimilar colours is important for many animals as it allows for accurately interpreting visual signals produced by key target stimuli or distractor information. Spectrophotometry objectively measures the spectral characteristics of these signals, but is often limited to point samples that could underestimate spectral variability within a single sample. Algorithms for RGB images and digital imaging devices with many more than three channels, hyperspectral cameras, have been recently developed to produce image spectrophotometers to recover reflectance spectra at individual pixel locations. We compare a linearised RGB and a hyperspectral camera in terms of their individual capacities to discriminate between colour targets of varying perceptual similarity for a human observer.Main Findings
(1) The colour discrimination power of the RGB device is dependent on colour similarity between the samples whilst the hyperspectral device enables the reconstruction of a unique spectrum for each sampled pixel location independently from their chromatic appearance. (2) Uncertainty associated with spectral reconstruction from RGB responses results from the joint effect of metamerism and spectral variability within a single sample.Conclusion
(1) RGB devices give a valuable insight into the limitations of colour discrimination with a low number of photoreceptors, as the principles involved in the interpretation of photoreceptor signals in trichromatic animals also apply to RGB camera responses. (2) The hyperspectral camera architecture provides means to explore other important aspects of colour vision like the perception of certain types of camouflage and colour constancy where multiple, narrow-band sensors increase resolution. 相似文献94.
Nissan X Blondel S Navarro C Maury Y Denis C Girard M Martinat C De Sandre-Giovannoli A Levy N Peschanski M 《Cell reports》2012,2(1):1-9
One puzzling observation in patients affected with Hutchinson-Gilford progeria syndrome (HGPS), who overall exhibit systemic and dramatic premature aging, is the absence of any conspicuous cognitive impairment. Recent studies based on induced pluripotent stem cells derived from HGPS patient cells have revealed a lack of expression in neural derivatives of lamin A, a major isoform of LMNA that is initially produced as a precursor called prelamin A. In HGPS, defective maturation of a mutated prelamin A induces the accumulation of toxic progerin in patient cells. Here, we show that a microRNA, miR-9, negatively controls lamin A and progerin expression in neural cells. This may bear major functional correlates, as alleviation of nuclear blebbing is observed in nonneural cells after miR-9 overexpression. Our results support the hypothesis, recently proposed from analyses in mice, that protection of neural cells from progerin accumulation in HGPS is due to the physiologically restricted expression of miR-9 to that cell lineage. 相似文献
95.
A. de Raucourt D. Girard Y. Prigent P. Boyaval 《Applied microbiology and biotechnology》1989,30(5):528-534
Summary An off-line parameter estimation method has been developed to predict the dynamic behaviour of a continuous lactose fermentation system. The model used is an unstructured model taking into account cell growth, substrate consumption, and metabolite production (lactic acid). This method, based on the Hooke-Jeeves non-linear-programming technique, results in a good estimation of the biological parameters of the model, and so gives a better understanding of the different phenomena involved in lactose fermentation.Nomenclature
Cp, Cs, Cz, Dp, Ds, Dz
coefficients in system (A)
-
Fe
bioreactor influent flow rate (1/h)
-
I
current in the ED unit (A)
-
J
lactate flux in the ED unit (g/h)
-
Kd
mortality constant (h-1)
-
Kp
product inhibition constant (g/l)
-
Ks
strbstrate saturation constant (g/l)
-
P
0
product concentration in the bioreactor (g/l)
-
P
1
product concentration in the D tank (g/l)
-
P
0r
estimation of P
0 (g/l)
-
Q
0
retentate flow rate (UF influent) (1/h)
-
Q
1
permeate flow rate (1/h)
-
Q
22
cell bleed flow rate (1/h)
-
Q
3
recycling flow rate in the ED (influent) (1/h)
-
Se
substrate concentration in the influent (g/l)
-
S
0
supstrate concentration in the bioreactor (g/l)
-
S
1
substrate concentration in tank D (g/l)
-
S
0r
estimation of S
0 (g/l)
-
t
time (h)
-
V
0
fermentation broth volume (1)
-
V
1
tank D volume (1)
-
X
0
biomass concentration in the bioreactor (g/l)
-
Y
P/S
(=1/Y
S/P) lactic acid yield coefficient (g lactic acid/g lactose consumed)
-
Y
X/S
(=1/Y
S/X) cell yield coefficient (g cells produced/g lactose consumed)
-
Y
X/Z
(=1/Y
Z/X) second cell yield coefficient (g cells produced/g nitrogen consumed)
-
Y
x, Y
m
input mathematical parameters of the linear system (M
2)
-
Ze
nitrogen concentration in the influent (g/l)
-
Z
0
nitrogen concentration in the bioreactor (g/l)
-
Z
1
nitrogen concentration in tank D (g/l)
-
Z
0r
estimation of Z
0 (g/l)
- ,
constants of the Luedeking and Piret's model
-
specific growth rate (h-1)
- max
maximum specific growth rate (h-1) 相似文献
96.
97.
The Open Microscopy Environment (OME) Data Model and XML file: open tools for informatics and quantitative analysis in biological imaging 总被引:2,自引:0,他引:2
Goldberg IG Allan C Burel JM Creager D Falconi A Hochheiser H Johnston J Mellen J Sorger PK Swedlow JR 《Genome biology》2005,6(5):R47
The Open Microscopy Environment (OME) defines a data model and a software implementation to serve as an informatics framework for imaging in biological microscopy experiments, including representation of acquisition parameters, annotations and image analysis results. OME is designed to support high-content cell-based screening as well as traditional image analysis applications. The OME Data Model, expressed in Extensible Markup Language (XML) and realized in a traditional database, is both extensible and self-describing, allowing it to meet emerging imaging and analysis needs. 相似文献
98.
99.
ABSTRACT:?Membrane technology for the processing of fruit juices and beverages has been applied mainly for clarification using ultrafiltration and microfiltration, and for concentration using reverse osmosis. The effects of product preparation, membrane selection, and operating parameters are important factors influencing filtration rate and product quality. Technological advances related to the development of new membranes, improvement in process engineering, and better understanding of fruit beverage constituents have expanded the range of membrane separation processes. Developments in novel membrane processes, including electrodialysis and pervaporation, increased the array of applications in combination with other technologies for alternate uses in fruit juices and beverages. 相似文献
100.
Engineering a Saccharomyces cerevisiae Wine Yeast That Exhibits Reduced Ethanol Production during Fermentation under Controlled Microoxygenation Conditions 下载免费PDF全文
Stphanie Heux Jean-Marie Sablayrolles Rmy Cachon Sylvie Dequin 《Applied microbiology》2006,72(9):5822-5828
We recently showed that expressing an H2O-NADH oxidase in Saccharomyces cerevisiae drastically reduces the intracellular NADH concentration and substantially alters the distribution of metabolic fluxes in the cell. Although the engineered strain produces a reduced amount of ethanol, a high level of acetaldehyde accumulates early in the process (1 g/liter), impairing growth and fermentation performance. To overcome these undesirable effects, we carried out a comprehensive analysis of the impact of oxygen on the metabolic network of the same NADH oxidase-expressing strain. While reducing the oxygen transfer rate led to a gradual recovery of the growth and fermentation performance, its impact on the ethanol yield was negligible. In contrast, supplying oxygen only during the stationary phase resulted in a 7% reduction in the ethanol yield, but without affecting growth and fermentation. This approach thus represents an effective strategy for producing wine with reduced levels of alcohol. Importantly, our data also point to a significant role for NAD+ reoxidation in controlling the glycolytic flux, indicating that engineered yeast strains expressing an NADH oxidase can be used as a powerful tool for gaining insight into redox metabolism in yeast. 相似文献