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241.
Chaperonins are large oligomers consisting of two superimposed rings, each enclosing a cavity used for the folding of other proteins. They have been divided into two groups. Chaperonins of type I were identified in mitochondria and chloroplasts (Hsp60) or bacterial cytosol (GroEL) as well. Chaperonins type II were found in Archea and the eukaryotic cell cytosol (CCT). Protein folding occurs in the chaperonin after its conformational changes induced upon ATP binding. Mechanism of the protein folding, although still poorly defined, clearly differs from the one established for GroEL. Although CCT with prefoldin seems to be mainly involved in the folding of actin and tubulin, other substrates engaged in various cellular processes are beginning to be characterized, including proteins possessing WD40-repeats. Moreover, several lines of evidence suggest that beside prefoldin, CCT may work in concert with phosducin-like proteins (PhLPs). 相似文献
242.
Variation in the shell colour and banding polymorphism in the land snail Cepaea nemoralis was studied in 260 populations in the region of Gdańsk, northern Poland. Unlike in other regions of Poland, many populations
contain brown shells. Populations from shaded habitats have higher frequencies of brown than those from open and intermediate
habitats, largely at the expense of yellow shells. Nearly all brown shells are also unbanded. Apart from this disequilibrium,
banding morphs among yellow and pink shells show no relationship to habitat. There are no broad geographical trends in morph-frequencies,
but there are very strong correlations among populations very close together, revealed both by pairwise analysis and Moran’s
I. Principal Component Analyses show that these correlations relate to overall genetic similarity at the loci involved. The
populations are at the north-eastern limits of the species’ range; habitats are mostly anthropogenic, and comparisons with
studies in two urban areas (Wrocław, SW Poland, and Sheffield, central England) suggest that the patterns of variation seen
are a product of human transport of propagules followed by local dispersal. The effect of habitat here is much less marked
than in regions much further west, but it indicates that natural selection has occurred. 相似文献
243.
The abundance and the biodiversity of summer zooplankton in the waters of the Drawa drainage (NW Poland) were studied, as
was their relation to selected environmental conditions. The conditions upstream, especially in the outlets of lakes, did
not affect the zooplankton communities downstream. This was also true of tributaries which had no influence on the shape of
the zooplankton communities in the main river. The number of zooplankton in the outlets of eutrophic lakes was greater than
in those of mesotrophic lakes. Increased vegetation cover significantly affected mainly the crustacean communities of zooplankton.
Larger amounts of zooplankton were observed in rivers where the riparian zone was not covered with vegetation, but this difference
was not significant. The hydrological conditions of the rivers and the Secchi depth visibility strongly impacted the composition
of the zooplankton. The influence of abiotic factors was most pronounced on the abundance of cladocerans, and least pronounced
on the abundance of rotifers. 相似文献
244.
Primary leaves of bean (Phaseolus vulgaris L.) seedlings cultivated for 14 days in a growth chamber on complete (control) and phosphate deficient (−P) Knop liquid medium
were used for measurements. The −P leaves were smaller and showed an increased specific leaf area (SLA). Their inorganic phosphate
(Pi) concentration was considerably lowered. They did not show any significant changes in chlorophyll (Chl) (a + b) concentration and in their net CO2 assimilation rate when it was estimated under the conditions close to those of the seedlings growth. Light response curves
of photosynthetic net O2 evolution (P
NO2) of the leaves for the irradiation range up to 500 μmol(photon) m−2 s−1 were determined, using the leaf-disc Clark oxygen electrode. The measurements were taken under high CO2 concentration of about 1 % and O2 concentrations of 21 % or lowered to about 3 % at the beginning of measurement. The results obtained at 21 % O2 and the irradiations close to or higher than those used during the seedlings growth revealed the phosphorus stress suppressive
effect on the leaf net O2 evolution, however, no such effect was observed at lower irradiations. Other estimated parameters of P
NO2 such as: apparent quantum requirement (QRA) and light compensation point (LCP) for the control and −P leaves were similar. However, with a high irradiation and lowered
O2 concentration the rate of P
NO2 for the −P leaves was markedly higher than that for the control, in relation to both the leaf area and leaf fresh mass. This
difference also disappeared at low irradiations, but the estimated reduced QRA values indicate, under those conditions, the increased yield of photosynthetic light reaction, especially in the −P leaves.
The presented results confirm the suggestion that during the initial phase of insufficient phosphate feeding the acclimations
in the light phase of photosynthesis, both structural and functional appear. They correspond, probably, to the increased energy
costs of carbon assimilation under phosphorus stress, e.g. connected with raised difficulties in phosphate uptake and turnover and enhanced photorespiration. Under the experimental
conditions especially advantageous for the dark phase of photosynthesis (saturating CO2 and PAR, low O2 concentration), those acclimations may be manifested as an enhancement of photosynthetic net O2 evolution. 相似文献
245.
246.
Rowena Spence Robert J. Wootton Iain Barber Mirosław Przybylski Carl Smith 《Ecology and evolution》2013,3(6):1717-1726
The central assumption of evolutionary theory is that natural selection drives the adaptation of populations to local environmental conditions, resulting in the evolution of adaptive phenotypes. The three‐spined stickleback (Gasterosteus aculeatus) displays remarkable phenotypic variation, offering an unusually tractable model for understanding the ecological mechanisms underpinning adaptive evolutionary change. Using populations on North Uist, Scotland we investigated the role of predation pressure and calcium limitation on the adaptive evolution of stickleback morphology and behavior. Dissolved calcium was a significant predictor of plate and spine morph, while predator abundance was not. Stickleback latency to emerge from a refuge varied with morph, with populations with highly reduced plates and spines and high predation risk less bold. Our findings support strong directional selection in three‐spined stickleback evolution, driven by multiple selective agents. 相似文献
247.
248.
Kałużna Monika Albuquerque Pedro Tavares Fernando Sobiczewski Piotr Puławska Joanna 《Applied microbiology and biotechnology》2017,101(2):903-903
Applied Microbiology and Biotechnology - 相似文献
249.
Wojciech Szczepanik Artur Krężel Magdalena Brzezowska Ewa Dworniczek Małgorzata Jeżowska-Bojczuk 《Inorganica chimica acta》2008,361(9-10):2659-2666
The formation of copper(II) complexes of an aminoglycoside antibiotic – sisomicin – was studied by potentiometry and spectroscopic techniques (UV–Vis, CD, NMR and EPR). At physiological pH, Cu(II) is bound to both amino functions and hydroxyl oxygen of the 2-deoxystreptamine moiety. When pH increases slightly, another amino group located at the aminosugar ring becomes engaged in the coordination process. Microbiological studies with the use of Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa showed that copper(II) does not interfere with the bactericidal action of sisomicin. 相似文献
250.
Zylicz-Stachula A Zołnierkiewicz O Jeżewska-Frąckowiak J Skowron PM 《BioTechniques》2011,50(6):397-406
The type IIS/IIC restriction endonuclease TspGWI recognizes the sequence 5'-ACGGA-3', cleaving DNA 11/9 nucleotides downstream. Here we show that sinefungin, a cofactor analog of S-adenosyl methionine, induces a unique type of relaxation in DNA recognition specificity. In the presence of sinefungin, TspGWI recognizes and cleaves at least 12 degenerate variants of the original recognition sequence that vary by single base pair changes from the original 5-bp restriction site with only a single degeneracy per variant appearing to be allowed. In addition, sinefungin was found to have a stimulatory effect on cleavage at these nondegenerate TspGWI recognition sites, irrespective of their number or the DNA topology. Interestingly, no fixed "core" could be identified among the new recognition sequences. Theoretically, TspGWI cleaves DNA every 1024 bp, while sinefungin-induced activity cleaves every 78.8 bp, corresponding to a putative 3-bp long recognition site. Thus, the combination of sinefungin and TspGWI represents a novel frequent cutter, next only to CviJI/CviJI*, that should prove useful in DNA cloning methodologies. 相似文献