全文获取类型
收费全文 | 6207篇 |
免费 | 440篇 |
国内免费 | 2篇 |
出版年
2023年 | 28篇 |
2022年 | 78篇 |
2021年 | 157篇 |
2020年 | 82篇 |
2019年 | 115篇 |
2018年 | 140篇 |
2017年 | 115篇 |
2016年 | 199篇 |
2015年 | 327篇 |
2014年 | 358篇 |
2013年 | 411篇 |
2012年 | 583篇 |
2011年 | 544篇 |
2010年 | 328篇 |
2009年 | 302篇 |
2008年 | 370篇 |
2007年 | 342篇 |
2006年 | 288篇 |
2005年 | 294篇 |
2004年 | 288篇 |
2003年 | 246篇 |
2002年 | 224篇 |
2001年 | 60篇 |
2000年 | 36篇 |
1999年 | 47篇 |
1998年 | 61篇 |
1997年 | 41篇 |
1996年 | 51篇 |
1995年 | 30篇 |
1994年 | 45篇 |
1993年 | 30篇 |
1992年 | 34篇 |
1991年 | 34篇 |
1990年 | 25篇 |
1989年 | 36篇 |
1988年 | 17篇 |
1987年 | 27篇 |
1986年 | 21篇 |
1985年 | 18篇 |
1984年 | 28篇 |
1983年 | 13篇 |
1982年 | 15篇 |
1981年 | 18篇 |
1980年 | 18篇 |
1979年 | 13篇 |
1978年 | 11篇 |
1977年 | 15篇 |
1976年 | 10篇 |
1975年 | 10篇 |
1973年 | 13篇 |
排序方式: 共有6649条查询结果,搜索用时 31 毫秒
61.
62.
Michael A. Kron Laura Gately Janardan P. Pandey Miguel H. Jurado Jose Rumbea Guzman 《Human genetics》1994,93(5):517-519
Indigenous Indian groups comprise approximately 20% of Ecuador's population, the third largest percentage in all of Central or South America, yet immunogenetic data on these groups are lacking in the literature. In the course of population migration studies, sera collected from 65 Ecuadorians living in the northern province of Esmeraldas were typed for six GM and two KM markers. The study population consisted of 47 Cayapa Indians and 18 blacks of African origin, descendants of slaves imported into the area during the seventeenth century. The Cayapa demonstrated three GM phenotypes, two of which are common to other South American Indian tribes. The frequency of KM1 positive Cayapa Indians (63%) is similar to other South American Indian tribes, but is significantly greater than the Huaorani of eastern Ecuador (2%), the only other Ecuadorian Indian group for whom limited immunoglobulin allotype data are available (
2=35.8, P<0.0001). 相似文献
63.
Taishin Nomura Shunsuke Sato Shinji Doi Jose P. Segundo Michael D. Stiber 《Biological cybernetics》1994,72(1):55-67
The Bonhoeffer-van der Pol (BVP) oscillator is a valuable dynamical system model of pacemaker neurons. Isochrons, phase transition curves (PTC), and two dimensional bifurcation diagrams served to analyze the neuron's response to periodic pulse stimuli. Responses are described and explained in terms of the nonlinear dynamical system theory. An important issue in the generation of spikes by pacemaker neurons is the existence of both slow and fast dynamics in the state point's trajectory in the phase plane. It is this feature in particular that makes the BVP oscillator a faithful model of living pacemaker neurons. Comparison of the model's responses with those of a living pacemaker was based also on return maps of interspike intervals. Analyzed in detail were the complex discharges called stammering which involve interspike intervals that arise unpredictably and exhibit histograms with several modes separated by the equal intervals.Supported by Trent H. Wells Jr. Inc. 相似文献
64.
Josefa Salgado Jose Villalain Juan C. Gómez-Fernández 《European biophysics journal : EBJ》1993,22(2):151-155
-Tocopherol, ubiquinone-10 and ubiquinol-10 have been studied by high resolution magic angle samples spinning 13C-nuclear magnetic resonance in egg yolk phosphatidylcholine multilamellar vesicles model membranes in order to assess their location and the induced perturbations on this model system. -Tocopherol is placed in such a position that it is in close contact with the head group of the phospholipid and exposed to the solvent. In this position it significantly perturbs the phospholipid head group, the 5a-CH3 and the 7a-CH3 groups being the closest parts to the membrane surface. On the other hand, ubiquinol-10 perturbs the membrane surface more than ubiquinone-10, but neither compound significantly changed the phospholipid head group conformation. 相似文献
65.
Different experiments using Mucor miehei CBS 370.65 were carried out to study the effect of agitation speed on the production of the mold acid protease. The experiments were conducted in shake flasks at a fixed substrate concentration of 58 g l−1 of total carbohydrates and at shaker speeds from 80 to 380 rev min−1. Enzyme production was found to be directly proportional to the shaker speeds, with the highest concentration of enzyme of 1,400 Soxhlet Rennet units (SU) ml−1 obtained at 380 rev min−1. The yield of product to substrate at 380 rev min−1 was determined to be 27,081.0 SU g−1 substrate and the productivity of the process was 221 SU g−1 h−1. Enzyme production was partially growth associated, and glucose supported both cell growth and enzyme production. Product formation and cell concentration were directly related to the rate of substrate consumption. The rate of product formation decreased when product started to accumulate, suggesting that the process was affected by feedback repression. 相似文献
66.
Estaras Matias Ortiz-Placin Candido Castillejo-Rufo Alba Fernandez-Bermejo Miguel Blanco Gerardo Mateos Jose M. Vara Daniel Gonzalez-Cordero Pedro L. Chamizo Sandra Lopez Diego Rojas Adela Jaen Isabel de Armas Noelia Salido Gines M. Iovanna Juan L. Santofimia-Castaño Patricia Gonzalez Antonio 《Journal of physiology and biochemistry》2023,79(1):235-249
Journal of Physiology and Biochemistry - We have investigated the effects of melatonin on major pathways related with cellular proliferation and energetic metabolism in pancreatic stellate cells.... 相似文献
67.
Nick S. Fradgley James Bacon Alison R. Bentley Germano Costa-Neto Andrew Cottrell Jose Crossa Jaime Cuevas Matthew Kerton Edward Pope Stéphanie M. Swarbreck Keith A. Gardner 《Global Change Biology》2023,29(5):1296-1313
Wheat is a major crop worldwide, mainly cultivated for human consumption and animal feed. Grain quality is paramount in determining its value and downstream use. While we know that climate change threatens global crop yields, a better understanding of impacts on wheat end-use quality is also critical. Combining quantitative genetics with climate model outputs, we investigated UK-wide trends in genotypic adaptation for wheat quality traits. In our approach, we augmented genomic prediction models with environmental characterisation of field trials to predict trait values and climate effects in historical field trial data between 2001 and 2020. Addition of environmental covariates, such as temperature and rainfall, successfully enabled prediction of genotype by environment interactions (G × E), and increased prediction accuracy of most traits for new genotypes in new year cross validation. We then extended predictions from these models to much larger numbers of simulated environments using climate scenarios projected under Representative Concentration Pathways 8.5 for 2050–2069. We found geographically varying climate change impacts on wheat quality due to contrasting associations between specific weather covariables and quality traits across the UK. Notably, negative impacts on quality traits were predicted in the East of the UK due to increased summer temperatures while the climate in the North and South-west may become more favourable with increased summer temperatures. Furthermore, by projecting 167,040 simulated future genotype–environment combinations, we found only limited potential for breeding to exploit predictable G × E to mitigate year-to-year environmental variability for most traits except Hagberg falling number. This suggests low adaptability of current UK wheat germplasm across future UK climates. More generally, approaches demonstrated here will be critical to enable adaptation of global crops to near-term climate change. 相似文献
68.
Batdorj Enkhjin AlOgayil Najla Zhuang Qinwei Kim-wee Galvez Jose Hector Bauermeister Klara Nagata Kei Kimura Tohru Ward Monika A. Taketo Teruko Bourque Guillaume Naumova Anna K. 《Mammalian genome》2023,34(1):44-55
Mammalian Genome - Several lines of evidence suggest that the presence of the Y chromosome influences DNA methylation of autosomal loci. To better understand the impact of the Y chromosome on... 相似文献
69.
Jimenez Carlos; Niell F.Xavier; Figueiras F.G.; Clavero Vicente; Algarra Patricia; Buela Jose 《Journal of plankton research》1992,14(5):705-720
In this paper we report a bloom of Gyrodinium cf. aureolum occurringin an estuary of the north-west coast of Spain. It was sampledin late August 1989, in shallow waters 2 m deep in the Ria ofPontevedra. Its temperature was 19.5°C and salinity 35 相似文献
70.
Jose L. Lopez-Lacomba M. Guzman Manuel Cortijo Pedro L. Mateo Raul Aguirre Stephen C. Harvey Herbert C. Cheung 《Biopolymers》1989,28(12):2143-2159
The thermal unfolding of myosin rod, light meromyosin (LMM), and myosin subfragment 2 (S-2) was studied by differential scanning calorimetry (DSC) over the pH range of 6.5–9.0 in 0.5M KCl and either 0.20M sodium phosphate or 0.15M sodium pyrophosphate. Two rod samples were examined: one was purified by Sephadex G-200 without prior denaturation (native rod), and the other was purified by a cycle of denaturation-renaturation followed by Sephacryl S-200 chromatography (renatured rod). There were clearly distinguishable differences in the calorimetric behavior of these two samples. At pH 7.0 in phosphate the DSC curves of native rod were deconvoluted into six endothermic two-state transitions with melting temperatures in the range of 46–67°C and a total enthalpy of 4346 kJ/mol. Under identical conditions the melting profile of LMM was resolved into five endothermic peaks with transition temperatures in the range of 45–66°C, and the thermal profile of long S-2 was resolved into two endotherms, 46 and 57°C. Transition 4 observed with native rod was present in the deconvoluted DSC curve for long S-2, but absent in the DSC curve for LMM. This transition was identified with the high-temperature transition detected with long S-2 and attributed to the melting of the coiled-coil α-helical segment of subfragment 2 (short S-2). The low-temperature transition of long S-2 was attributed to the unfolding of the hinge region. The smallest transition temperatures observed for all three fragments were 45–46°C. It is suggested that the most unstable domain in rod (domain 1) responsible for the 46°C transition includes both the hinge region, which is the C-terminal segment of long S-2, and a short N-terminal segment of LMM. This domain, accounting for 21% of the rod structure, contains the S-2/LMM junction, and upon proteolytic cleavage yields the C-terminal and N-terminal ends of long S-2 and LMM, respectively. Over the pH range of 6.5–7.5, the observed specific heat of denaturation of rod was approximately equal to the sum of the specific heats of LMM and S-2. This finding provides an additional argument for the existence of independent domains in myosin rod. 相似文献