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31.
32.
Summary The structure of the setae on the proximal antennal segments of the beetle Loricera pilicornis is described using electron microscopical methods. These setae are part of a prey-capturing apparatus and are inserted within flexible sockets. They have no central lumen.Four or five sensory cells are connected to each seta. One cell is characterized as a mechanoreceptor due to the presence of a tubular body and the location of its dendritic outer segment. The other sensory cells are of two types. One type shows the usual features of sensillar receptors except that the dendritic outer segments end beneath the seta within the cuticular sheath. In the other type all parts of the cell, including the perikaryon, appear undersized, and no axon was found. In a single case a sixth cell was found which lacks any process, although, due to its location, it belongs to the sensory cell group.The enveloping cells also deviate from the usual pattern. Trichogen and tormogen cells have no membrane folds nor microvilli. From the membrane of the thecogen cell, where it borders on the inner receptor lymph cavity, invaginations have developed which form voluminous membrane whorls. Portasomes are found on these membranes.On the basis of the structural features we hypothesize that the setae represent sensilla undergoing stepwise reduction, losing primordial gustatory units whilst the prey-capturing mechanism is optimized.Dedicated to Professor Dr. Dietrich Schneider on occasion of his 65th birthday 相似文献
33.
Characteristics of single chemoreceptive units sensitive to amino acids and related substances in the crayfish leg 总被引:2,自引:0,他引:2
Ulrike Bauer J. Dudel H. Hatt 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1981,142(1):67-74
Summary Impulses in single afferent fibres from amino acid receptors were recorded extracellularly. Doseresponse relations were determined for different superfused amino acids; the relations all had a slope of 1, a common saturation level, and the action of different amino acids was characterized by a specific half saturation concentration,K
M. The most effective amino acids were always L-serine, L-alanine and L-histidine, having aK
M of 10–5, 2·10–5 and 1.5·10–4 mol/l, respectively. The sequence of effective amino acids was the same for all units tested. Structural requirements for optimal stimulatory action of the amino acid molecules were concluded.Abbreviation
vH
van Harreveld solution
This work was supported by the Deutsche ForschungsgemeinschaftWe gratefully acknowledge assistance in electronics from Mr. W. Zeitz, and in mechanics from Mr. D. Beyer and Mr. L. Müller. Technical help was provided by Mrs. E. Köster, secretarial help by Mrs. L. Bauer. 相似文献
34.
In-vitro binding of labeled auxins to sedimentable particles was tested in subcellular fractions from homogenates of maize (Zea mays L.) coleoptiles. The material was fractionated by differential centrifugation or on sucrose density gradients. It was confirmed that the major saturable binding activity (site I) for 1-naphthyl[1-14C]acetic acid is associated with vesicles derived from the endoplasmatic reticulum. A second type of specific auxin binding (site II) could be distinguished by several criteria, e.g. by the low affinity towards phenylacetic acid. The particles carrying site II could be clearly separated from markers of the endoplasmatic reticulum, the plasmalemma, the mitochondria and the nuclei, while their density as well as sedimentation velocity correlated with particle-bound acid phosphatase, indicating a localization at the tonoplast. In contrast to site I, binding at site II was hardly affected by a supernatant factor and by sulfhydryl groups. However, the specificity pattern of site II towards auxins and auxin analogs was very similar to that of site I tested in the presence of supernatant factor. The existence of a third auxin receptor localized in plasma membrane-rich gradient fractions was indicated by a preferential in-vitro binding of 2,4-dichlorophenoxyacetic acid.Abbreviations 1-NAA
1-naphthyl acetic acid
- 2-NAA
2-naphthyl acetic acid
- IAA
3-indolyl acetic acid
- PAA
phenyl acetic acid
- 2,4-D
2,4-D-dichlorophenoxy acetic acid
- D-2,4-DP
dichlorophenoxy isopropionic acid
- NPA
1-N-naphthyl phthalamic acid
- ER
endoplasmatic reticulum
- SF
supernatant factor 相似文献
35.
Ulrike Nolte 《Hydrobiologia》1991,222(3):197-211
Chironomid communities of mosses in a small upland stream in central Germany were highly dynamic across the year with respect to their abundance, biomass and dominant taxa. During 1988 semi-submersed mosses near a main spring and those occurring some 700 m downstream were compared with permanently submersed mosses in immediate vicinity of the downstream site. All the chironomids sampled were conspicuously small, with nearly 98% being less than 5 mm in length. A total of 65 chironomid species from 26 genera were found, with a higher diversity occurring near the source and a change in dominant taxa along the upper stream section. The mean abundance in permanently submersed mosses (250 larvae/10 cm2, n = 125) was about five times higher than in semi-submersed mosses. The maximum value of 830 larvae/10 cm2 (n = 1) is the highest chironomid density ever reported, which is explained by the sampling method used. The mean standing crop was also highest in permanently submersed mosses (1.5 mg AFDW/10 cm2 (n = 125)), even though the highest individual value was recorded in semi-submersed mosses near the spring (10.4 mg AFDW/10 cm2). The evidence suggested that the dominance of chironomid taxa depended mainly on the location of the moss along the stream, whereas abundance and biomass were determined mainly by constancy in the ambient discharge as well as the factors influenced by this (e.g. temperature, detritus deposition). A trend was seen towards a seasonal succession among the chironomid taxa colonizing lotic mosses. 相似文献
36.
G Stenbeck R Schreiner D Herrmann S Auerbach F Lottspeich J E Rothman F T Wieland 《FEBS letters》1992,314(2):195-198
Constitutive secretory transport in eukaryotes is likely to be mediated by non-clathrin-coated vesicles, which have been isolated and characterized [(1989) Cell 58, 329-336; (1991) Nature 349, 215-220]. They contain a set of coat proteins (COPs) which are also likely to exist in a preformed cytosolic complex named coatomer [(1991) Nature 349, 248-250]. From peptide sequence and cDNA structure comparisons evidence is presented that one of the subunits of coatomer, gamma-COP, is a true constituent of non-clathrin-coated vesicles, and that gamma-COP is related to sec 21, a secretory mutant of the yeast Saccharomyces cervisiae. 相似文献
37.
Characterization of cisplatin adducts of oligonucleotides by fast atom bombardment mass spectrometry
The products of the reaction of the antitumor drug cisplatin (cis-diamminedichloroplatinum(II)) with four oligonucleotide tetramers, d(GpCpGpC), d(GpGpCpC), d(TpGpApT), and d(TpGpCpT), were separated by gel permeation chromatography and characterized by negative- and positive-ion fast atom bombardment (FAB) mass spectrometry. Fragment ions indicating the oligonucleotide sequence and the position of cisplatin binding were observed in MS/MS spectra following collisional activation and B/E-linked scanning. Positive-ion FAB MS/MS spectra were characterized by platinum-containing product ions. Nonplatinated sequence ions and internal fragment ions were present primarily in the negative-ion spectra. The most prominent fragment ions containing platinum were [HB2.Pt.B3H]+ and [HB1.Pt.B2H]+, where B1, B2, and B3 were bases in the oligonucleotide tetramer, one of which was usually guanine. Both singly and doubly charged platinum complexes were observed, probably indicating reduction of Pt(II) during the FAB ionization process. The location of the platinum complex bound to each oligonucleotide sequence could be determined, and the binding sites observed by mass spectrometry were similar to those previously determined by other methods. FAB ionization with collisional activation and MS/MS analysis could serve as a new method for structural analysis of platinated oligonucleotides. 相似文献
38.
Purification and Properties of a Thermoactive Glucoamylase from Clostridium thermosaccharolyticum 总被引:1,自引:1,他引:0 下载免费PDF全文
A bacterial glucoamylase was purified from the anaerobic thermophilic bacterium Clostridium thermosaccharolyticum and characterized. The enzyme, which was purified 63-fold, with a yield of 36%, consisted of a single subunit with an apparent molecular mass of 75 kDa. The purified enzyme was able to attack α-1,4- and α-1,6-glycosidic linkages in various α-glucans, liberating glucose with a β-anomeric configuration. The purified glucoamylase, which was optimally active at 70°C and pH 5.0, attacked preferentially polysaccharides such as starch, glycogen, amylopectin, and maltodextrin. The velocity of oligosaccharide hydrolysis decreased with a decrease in the size of the substrate. The Km values for starch and maltose were 18 mg/ml and 20 mM, respectively. Enzyme activity was not significantly influenced by Ca2+, EDTA, or α- or β-cyclodextrins. 相似文献
39.
The generation time ofP. branickii was studied using larval samples in conjunction with rearing experiments and continuous collection of egg masses across one year. This species produced three generations per year in a central German stream (280 m a.s.l., 50° 40 N). Its generation time was variable and obviously influenced by the photoperiod to which eggs and larvulae were subjected. It is thus concluded that two strains ofP. branickii were present in a single population, one bivoltine and the other trivoltine. 相似文献
40.