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81.
E. N. Shchurova 《Human physiology》2008,34(4):493-499
The maximum contractility of the muscles of the lower extremities was studied in patients with lumbar disc hernia in different age periods. Characteristics of the age-related changes in the muscle function of the patients were analyzed in comparison with the parameters of men with physiologically normal aging. It is shown that the maximum strength of muscles of the lower extremities (lower leg extensors and flexors and plantar flexors of the foot) in patients with lumbar disc hernia is 46–50% lower than in healthy subjects. This value is characterized by a negative correlation with age. The percentage of the age-specific decrease in the strength of three groups of muscles (lower leg extensors and flexors and plantar flexors of the foot) is 14% higher than in healthy men. The age-related decrease in the muscle strength of the lower extremities begins 30 years earlier. 相似文献
82.
C. W. Cunningham 《Biological invasions》2008,10(1):1-6
The rapid range southward expansion of the periwinkle Littorina littorea from the Canadian maritimes has fueled a long-running debate over whether this species was introduced to North America by
human activity. A reappraisal of the mitochondrial DNA sequence evidence finds considerable endemic allelic diversity in the
American population. The degree of endemic genetic diversity is higher than expected from human-mediated colonization, but
not so much to suggest that it survived the last glacial maximum in America. Coalescent estimates of population divergence
agree that colonization of America preceded European contact. A reappraisal of the ITS nuclear sequence data finds extensive
recombination. Taking this recombination into account strengthens the genetic case against human-mediated introduction. Finally,
a reappraisal of conflicting allozyme studies from the 1970’s supports a claim of limited divergence between American and
European populations. This is consistent with post-glacial colonization, but the allozyme data cannot distinguish between
natural or human-mediated colonization. Taken as a whole, the DNA sequence data supports the many sub-fossil reports of an
American L. littorea population in the Canadian maritimes that preceded even the first visits by the Vikings. 相似文献
83.
V. V. Dvorkin N. N. Dzbanovskii P. V. Minakov N. V. Suetin A. Yu. Yur'ev 《Plasma Physics Reports》2003,29(9):789-795
Optical emission spectra from the microwave discharge plasma that is used to activate gas-phase deposition of carbon films are systematically investigated under various deposition conditions. The line emission intensities from CH and C2 radicals, which are responsible for the growth of the diamond and graphite phases, respectively, are studied as functions of the main macroparameters of the process. To find the relation between the features of the emission spectra and the composition of the films obtained, the films were examined using Raman spectroscopy and electron microscopy. It is shown that monitoring the relative intensities of the spectral lines can be used to obtain the desired type of film, in which case the state of the substrate surface and the presence of a catalyst on it also play an important role. Experiments on the deposition of carbon films in the pulsed regime of plasma excitation show the possibility of changing the phase composition of the film by varying both the pulse repetition rate and the off-duty factor. At the same average microwave power, the rate of film deposition in the pulsed regime of plasma excitation is lower than that in a continuous discharge; however, the growth rate of the graphite phase decreases insignificantly. 相似文献
84.
85.
86.
Yu. V. Mamkaev 《Biology Bulletin》2009,36(2):98-106
Different approaches to evolutionary interpretation of ontogenies are compared, with special emphasis on the evolutionary role of morphogenetic mechanisms (construction technologies) substantially affecting the structure of definitive forms: they largely determine the structural characteristics of organs, types of anatomical and histological systems, and specificity of symmetry of organisms and their parts. The role of cellular morphogenesis inherited from protozoan ancestors in the morphogenesis of multicellular organisms is demonstrated. Two main ways of improving morphogeneses are considered, based on epithelial morphogenesis and early determined few-celled primordia. On the one hand, the phylogenetic role of archallaxes and deviations is emphasized, these events often switching evolution to a fundamentally new direction. On the other hand, many characteristics of developmental stages are explainable by rationalization of morphogeneses and do not recapitulate ancestral forms, which should be taken into consideration in phylogenetic interpretation of embryogeneses; in particular, this applies to interpretation of axial relationships. 相似文献
87.
A. V. Timofeev 《Plasma Physics Reports》2009,35(11):912-923
A previously developed method for analyzing the plasma processing of spent nuclear fuel is generalized to a plasma containing
multicharged fuel ions. In such a plasma, ion cyclotron resonance heating of nuclear ash ions should be carried out in two
monochromatic RF fields of different frequencies, provided that the fraction of ξ multicharged ions is small, ξ ≤ 0.1, a condition
that substantially restricts the productivity of systems for processing spent nuclear fuel. Ways of overcoming this difficulty
are discussed. 相似文献
88.
There is a growing body of evidence that suggests the effective functioning of marine reserves is dependent on the dispersal
and recruitment of larvae. Enhanced production inside reserves is predicted to lead to a net larval export and increased settlement
and recruitment outside reserve boundaries. However, larval retention in bays is also well documented. Since bays are increasingly
being used as reserve areas, planktonic larvae of benthic marine invertebrates were sampled from two semi-enclosed marine
reserves during flood and ebb tides to determine whether these bays are acting as net exporters of larvae. Neither reserve
was a net importer or exporter of species richness, larval abundance or diversity, although one reserve showed a small export
of species richness during the hours of darkness. Both reserves balanced the net import of some species with a net export
of others, which was generally related to adult or larval abundance, although exceptions were found in one reserve. Significant
effects of light were found, with the net import or export of some species occurring exclusively during either the hours of
daylight or darkness. An increased understanding of larval sink-source dynamics in bays is essential for ensuring their effective
use as marine reserves to meet specific conservation needs.
Guest editors: J. Davenport, G. Burnell, T. Cross, M. Emmerson, R. McAllen, R. Ramsay & E. Rogan
Challenges to Marine Ecosystems 相似文献
89.
We studied the structure of alcohol-soluble lignin in cognac spirits from Spain (7-year aging) and Azerbaijan (15-year aging). Alcohol-soluble lignin was precipitated and refractionated by means of preparative high-performance liquid chromatography. Lignin was studied by the method of high-performance liquid chromatography and mass spectrometry. Lignin hydrolysis products were assayed by the method of gas-liquid chromatography and mass spectrometry. The structure of lignans was reconstructed from these fragments. Lignans from Spanish and Azeri alcohol were arbitrarily designated as sinapoconiferal triglycoside and glucoferulate flavone diglycoside, respectively. 相似文献
90.
Jaap J. Beintema 《Journal of the history of biology》2008,41(1):159-165
Albert (von) Szent-Györgyi started his studies on biological oxidation processes – which also resulted in the discovery of vitamin C, for which he received the Nobel Price in 1937 – in the Laboratory of Physiology of the University in Groningen in 1922–1926. These studies were later continued in Cambridge (UK) and Szeged (Hungary). When he had already received the invitation as well as the financial means to come and work in Cambridge, he still did experiments in Groningen to find out whether the adrenal extract, isolated by him and later found to be a major source of vitamin C, contained the hormone essential for the survival of cats whose adrenals were removed. He was rather upset by the negative results of this experiment, judging by the recollections of a former student of his. This history constitutes an interesting example of the difference between serendipitous discovery and planned invention. 相似文献