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51.
Franz Uiblein 《Environmental Biology of Fishes》1992,33(3):311-316
Synopsis Experimental data on snapping behavior of laboratory reared zährte, Vimba elongata, indicate that this species chooses between different food searching methods. If visibility is good, mainly directed snaps are employed for immediate food location. However, under conditions of reduced visibility undirected snapping and sampling methods are adopted. In the field, zährte may use sampling to acquire foraging benefits from stochastically distributed, hidden resources, like sediment dwelling prey. In the experiments this species continued to sample the bottom even in situations without any chance of prey detection. It is therefore concluded that zährte's searching decisions, apart from incorporating external information on prey occurrence, are controlled by internal expectations of long term benefits derived from sampling. 相似文献
52.
The influences of diets having different fatty acid compositions on the fatty-acid content, desaturase activities, and membrane fluidity of rat liver microsomes have been analyzed. Weanling male rats (35–45 g) were fed a fat-free semisynthetic diet supplemented with 10% (by weight) marine fish oil (FO, 12.7% docosahexaenoic acid and 13.8% eicosapentaenoic acid), evening primrose oil (EPO, 7.8% γ-linolenic acid and 70.8% linoleic acid) or a mixture of 5% FO-5% EPO. After 12 weeks on the respective diets, animals fed higher proportions of (n-3) polyunsaturated fatty acids (FO group) consistently contained higher levels of 20:3(n-6), 20:5(n-3), 22:5(n-3), and 22:6(n-3), and lower levels of 18:2(n-6) and 20:4(n-6), than those of the EPO (a rich source of (n-6) polyunsaturated fatty acids) or the FO + EPO groups. Membrane fluidity, as estimated by the reciprocal of the order parameter SDPH, was higher in the FO than in the EPO or the FO + EPO groups, and the n-6 fatty-acid desaturation system was markedly affected. 相似文献
53.
Summary Retinopetal neurons were visualised in the telencephalon and diencephalon of an air-breathing teleost fish, Channa punctata, following administration of cobaltous lysine to the optic nerve. The labelled perikarya (n=45–50) were always located on the side contralateral to the optic nerve that had received the neuronal tracer. The rostral-most back-filled cell bodies were located in the nucleus olfactoretinalis at the junction between the olfactory bulb and the telencephalon. In the area ventralis telencephali, two groups of telencephaloretinopetal neurons were identified near the ventral margin of the telencephalon. The rostral hypothalamus exhibited retrogradely labelled cells in three discrete areas of the lateral preoptic area, which was bordered medially by the nucleus praeopticus periventricularis and nucleus praeopticus, and laterally by the lateral forebrain bundle. In addition to a dorsal and a ventral group, a third population of neurons was located ventral to the lateral forebrain bundle adjacent to the optic tract. The dorsal group of neurons exhibited extensive collaterals; a few extended laterally towards the lateral forebrain bundle, whereas others ran into the dorsocentral area of the area dorsalis telencephali. A few processes extended via the anterior commissure into the telencephalon ipsilateral to the optic nerve that had been exposed to cobaltous lysine. However, the ventral cell group did not possess collaterals. In the diencephalon, retinopetal cells were visualised in the nucleus opticus dorsolateralis located in the pretectal area; these were the largest retinopetal perikarya of the brain. The caudal-most nucleus that possessed labelled somata was the retinothalamic nucleus; it contained the largest number of retinopetal cells. The limited number of widely distributed neurons in the forebrain, some with extensive collaterals, might participate in functional integration of different brain areas involved in feeding, which in this species is influenced largely by taste, not solely by vision. 相似文献
54.
Gary J. Rose James G. Canfield 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1991,168(4):461-467
Several species of weakly electric fish reflexively change their frequency of electric organ discharge (EOD) in response to sensing signals of similar frequency from conspecifics; that is, they exhibit jamming avoidance responses (JAR).Eigenmannia increases its EOD frequency if jammed by a signal of lower frequency and decreases its EOD frequency if jammed by a signal of higher frequency. This discrimination is based on an analysis of the patterns of amplitude modulations and phase differences resulting from signal interference. Fish of the closely related genus,Sternopygus, however, do not exhibit a JAR. Here we show that despite lacking this behavior,Sternopygus shares many sensory processing capacities withEigenmannia:
相似文献
1. | Fish could be conditioned to discriminate the sign of the frequency difference (Df) between an exogenous sinusoidal signal and its own EODs with as few as 300 training trials. |
2. | Fish can discriminate the sign of Df for jamming signals with an amplitude as low as 2 V/cm (p-p); which is approximately 40 dB below the amplitude of the fish's EOD, as measured lateral to the operculum. |
3. | Fish appear to discriminate the sign of Df by evaluating modulations in signal amplitude and differences in the timing of signals received by different areas of the body surface. |
4. | Sternopygus processes electrosensory information through band-pass modulation filters. Tuning to modulation rates over at least 4–16 Hz exists. |
55.
Svenja Viete Walter Heiligenberg 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1991,169(1):15-23
Summary In its Jamming Avoidance Response (JAR), the gymnotiform electric fish Eigenmannia shifts its electric organ discharge (EOD) frequency away from similar interfering frequencies. Continual behavioral measurements were carried out in 164 juvenile fish until a correct JAR emerged. Sixty-four of these fish were raised in complete isolation, the remainder in a community of their siblings. A correct JAR emerged in fish of 1.2–1.6 cm in body length, corresponding to a developmental age of 24–32 days. In 6 of 164 fish, the emergence of a correct JAR followed an interim appearance of an incorrect JAR, which involved frequency shifts in the direction opposite to those of a correct JAR. The fish raised in isolation developed the same forms of behavior and showed the same sequence in their appearance as did socially raised fish. This indicates that the JAR and its developmental schedule are innate. The appearance of an incorrect JAR suggests initial errors or incompleteness in the wiring of central nervous connections. A correct JAR ultimately emerged even if a stimulus regimen was offered that rewarded frequency shifts in the direction opposite to those of a correct JAR. This indicates that the development of the JAR is immune to experimental alterations of sensory experience.Abbreviations
Df
frequency difference between a jamming stimulus and fish's EOD
-
ELL
electrosensory lateral line lobe
-
EO
electric organ
-
EOD
electric organ discharge
-
JAR
Jamming Avoidance Response
-
nE
nucleus electrosensorius
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nE
subnucleus of nE, causing drop of EOD frequency
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nE
subnucleus of nE, causing rise of EOD frequency
-
Pn
pacemaker nucleus
-
PPn
prepacemaker nucleus 相似文献
56.
Murray Itzkowitz 《Environmental Biology of Fishes》1991,30(3):287-293
Synopsis Male beaugregory damselfish,Stegastes leucostictus, were provided with three types of artificial breeding structures to determine if they change habitats based on past or future reproductive payoffs. All three site types quickly lured males away from their natural sites. In comparison to those living on natural sites, those using artificial sites were less likely to move to different areas and had a higher reproductive success. When given no choice, male reproductive success was correlated to structural type. A second experiment provided males with an additional structure after using the intermediate quality type for 2 months. Males would often initially use both sites but would eventually shift their spawning activity to the new site if it was of the same quality or better than the old one. However, males would not move if the new site was of inferior quality. When given a new site identical to the initial one, approximately half of the males shifted to the new site. There was no evidence that reproductive performance influenced a male's decision to use a new site. 相似文献
57.
Muderhwa Nshombo 《Environmental Biology of Fishes》1991,31(2):207-212
Synopsis Of 23 males and 39 females of Plecodus straeleni observed for one hour each, 2 males and 14 females searched for the mouthbrooder Cyathopharynx furcifer under courtship display near or in the bower to get eggs, besides foraging for other prey to ripe off scales and skin. After finding a courting C. furcifer, they quietly waited on the substrate near the bower until it spawned. Immediately after spawning, the waiting P. straeleni dashed upon the female of C. furcifer and quickly collected the eggs. This egg-eating was achieved 5 times by 3 females who spent most of their time searching and waiting. 相似文献
58.
59.
The effect of fish predation on Cyclops life cycle 总被引:2,自引:2,他引:0
Two populations of Cyclops abyssorum tatricus studied in neighbouring alpine lakes in Tatra Mountains (southern Poland) differed in their life cycles. In the lake with planktivorous fishes, Cyclops was typically monocyclic, with highly synchronized reproduction during two winter months, while in the fishless lake its reproduction was asynchronous and continued for six months. Direct and indirect effects of fish predation on Cyclops life cycles are discussed. 相似文献
60.
I. M. Drobysheva 《Hydrobiologia》1986,132(1):189-193
Autoradiography has been applied to two acoel turbellarians, Convoluta convoluta and Oxyposthia praedator, to determine the distribution and fate of proliferative cells. In C. convoluta, mitotic figures and nuclei that labelled with [3H]thymidine could be observed in the peripheral parenchyma but not in the middle zone of the central parenchyma. The time required for regeneration of physiologically competent digestive cells was about 10–15 days. In O. praedator, mitotic figures (in metaphase and telophase) were observed in the peripheral parenchyma while none were found in the epidermis either in untreated animals or after treatment with colchicine. Mitotic figures were found only rarely in the central parenchyma and only in its marginal zone. Autoradiographs of O. praedator demonstrated [3H]thymidine incorporation into both the nuclei and the cytoplasm of peripheral parenchymal cells. In the central parenchyma, no nuclei with primary labelling were observed. The digestive parenchyma of the acoels is regarded as a unique histological system involving both specialized cells of the central parenchyma and stem cells located in the peripheral parenchyma. 相似文献