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11.
The annual reproductive cycle of the freshwater mussel Dreissena polymorpha Pallas in lakes 总被引:5,自引:2,他引:3
Jost Borcherding 《Oecologia》1991,87(2):208-218
Summary The annual development of the gonads of Dreissena polymorpha was studied at three sampling sites in two lakes over 3 and 1 1/2 years, respectively. A resting stage occurred after the last spawning in summer/autumn. Oogenesis (accompanied by multiplying segmentation of the oogonia and early growth processes of its oocytes) restarted in specimens at least 1 year old at low temperatures (below 10° C) during winter and early spring. At one location (Fühlinger See) the onset of the spawning season was correlated with an increase of water temperatures above 12° C. At 2 m depth, two main spawning periods in May and August were normally recognized, the first at temperatures of 12–16° C, the second at 16–21° C. It was clearly demonstrated for the first time in Dreissena polymorpha that the oocytes became mature in successive cohorts within one gonad. A female mussel may spawn several times during the reproductive season. At 9 m depth, the onset of spawning also started at about 12° C; this occurred in late summer, with two spawning periods within 1 month at a temperature range of 12–16° C. At another location (Heider Bergsee) the size of the gonads and the oocytes was reduced during April of both years studied, when food supply was low simultaneously with rapidly rising water temperatures in this shallow lake. There was no spawning period during spring. The major spawning period was delayed until July (temperatures 19–22°C). This shows (1) the synchronizing influence of low winter temperatures on the annual reproductive cycle and (2) a temperature threshold of at least 12° C for the start of the spawning processes. The results are discussed with regard to the geographical limits of further spread of Dreissena polymorpha. 相似文献
12.
A. A. Serikov 《Journal of biological physics》1991,18(1):65-77
Model equations for the kinetics of the synthesis and decay of molecular aggregates are used to show the high sensitivity of equilibrium concentrations of high-molecular aggregates to external radiation. This phenomenon is used to explain the effects of low-intensity microwave fields on the functioning of biological systems. The experimental results on the influence of SHF-radiation on ferricyanide reduction by erythrocytes are interpreted in detail. 相似文献
13.
用相关和回归处理方法,研究了8条正常狗咽喉部高频喷射通气时,调节驱动压、呼吸比和频率对喷气量、吸入气氧浓度、动脉血气及气道内压的作用。结果显示,驱动压和呼吸此对各观察指标几乎有同等重要的作用,频率的影响很小,喷气量与吸入气氧浓度、动脉血气、气道内压间存在显著的正相关关系。说明调节参数的意义主要在于改变了喷气量。 相似文献
14.
Hanns-Christof Spatz 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1991,161(3):231-236
Summary This paper attempts to explain Kleiber's rule, which relates metabolic rate of mammals to their body mass, from the structure and function of the blood circulation system.Abbreviations
a
scaling factor
-
fractal dimension
-
hydrodynamic conductivity
-
l
n
length of an arterial blood vessel at bifurcation level n
-
M
body mass
-
N
maximal number of bifurcation levels
-
p
pressure
-
Q
flow
-
r
size of Bohr effect
-
r
n
radius of an arterial blood vessel at bifurcation level n
-
V
volume
-
VO
2
rate of oxygen unloading
-
Z
n
number of arterial blood vessels at bifurcation level n 相似文献
15.
To date, the sequences of 45 Bradyrhizobium japonicum genes are known. This provides sufficient information to determine their codon usage and G+C content. Surprisingly, B. japonicum nodulation and NifA-regulated genes were found to have a less biased codon usage and a lower G+C content than genes not belonging to these two groups. Thus, the coding regions of nodulation genes and NifA-regulated genes could hardly be identified in codon preference plots whereas this was not difficult with other genes. The codon frequency table of the highly biased genes was used in a codon preference plot to analyze the RSRj9 sequence which is an insertion sequence (IS)-like element. The plot helped identify a new open reading frame (ORF355) that escaped previous detection because of two sequencing errors. These were now corrected. The deduced gene product of ORF355 in RSRj9 showed extensive similarity to a putative protein encoded by an ORF in the T-DNA of Agrobacterium rhizogenes. The DNA sequences bordering both ORFs showed inverted repeats and potential target site duplications which supported the assumption that they were IS-like elements. 相似文献
16.
G. Akoev G. N. Andrianov T. Szabo B. Bromm 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1991,168(6):639-646
Summary Dissected ampullae of Lorenzini of the skate (Raja clavata) were studied with the aim of determining the synaptic transmitter between electroreceptor cell and afferent fibre. Resting activity and stimulus-evoked activity in response to electrical pulses were recorded in single afferent units at constant perfusion with normal and test solutions containing different putative neurotransmitters. Presynaptic transmitter release was blocked by Mg2+ (up to 50 mM) to investigate the effects of the test substances upon the postsynaptic membrane. l-Glutamate (l-GLU) and l-aspartate (l-ASP), both at concentrations between 10-7 and 10-3
M, enlarged strongly resting and stimulus-evoked discharge frequency in the afferent fibre. If transmission was blocked by high Mg2+, resting discharge frequency could be restored by l-GLU or l-ASP. The glutamate agonists quisqualate (10-8–105
M) and N-methyl-D-aspartate (10-5–10-3
M) enlarged spontaneous activity in the afferent fiber. The same was found for kainic acid (10-9–10-5
M). Taurine at concentrations between 10-5 and 10-3
M caused a concentration-dependent decrease in afferent activity. The same was found for gammaaminobutyric acid (GABA; 10-5–10-4
M), and for the catecholamines adrenaline and noradrenaline, both in concentrations between 10-5 and 10-3
M. Serotonine (10-5–10-3
M) and dopamine (10-5-10-3
M) had no effect on resting or evoked activity in the Lorenzinian ampulla afferents. Acetylcholine (ACh; 10-4
M) enlarged discharge frequency in those units with initial rates lower than 22–25 Hz, but diminished discharge frequency in fibres with initial activity higher than 25 Hz. When synaptic transmission was blocked by high Mg2+ solution, perfusion with additional ACh did not restore resting activity in the afferent fibre. The results suggest that the most probable transmitter in the afferent synapse of the ampullae of Lorenzini is l-GLU or l-ASP, or a substance of similar nature.Abbreviations
ACh
acetylcholine
-
GABA
gamma aminobutyric acid
-
KA
kainic acid
-
l-ASP
l-aspartate
-
l-GLU
l-glutamate
-
NMDA
N-methyl-D-aspartate
-
Q
quisqualate
-
n.s.
normal solution 相似文献
17.
Michael R. Ibbotson 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1991,168(1):91-102
This paper describes the morphology and response characteristics of two types of paired descending neurons (DNs) (classified as DNVII1 and DNIV1) and two lobula neurons (HR1 and HP1) in the honeybee, Apis mellifera.
相似文献
1. | The terminal arborizations of the lobula neurons are in juxtaposition with the dendritic branches of the DNs (Figs. 2, 3b, 5). Both of the DNs descend into the ipsilateral side of the thoracic ganglia via the dorsal intermediate tract (Fig. 6) and send out many blebbed terminal branches into the surrounding motor neuropil (Figs. 3c, 7). |
2. | Both the lobula and descending neurons respond in a directionally selective manner to the motion of widefield, periodic square-wave gratings. |
3. | The neurons have broad directional tuning curves (Figs. 10, 11). HR1 is maximally sensitive to regressive (back-to-front) motion and HP1 is maximally sensitive to progressive (front-to-back) motion over the ipsilateral eye (Fig. 11). DNVII1 is maximally sensitive when there is simultaneous regressive motion over the ipsilateral eye and progressive motion over the contralateral eye (Fig. 12a). Conversely, DNIV1 is optimally stimulated when there is simultaneous progressive motion over the ipsilateral eye and regressive motion over the contralateral eye (Fig. 12b). |
4. | The response of DNIV1 is shown to depend on the contrast frequency (CF) rather than the angular velocity of the periodic gratings used as stimuli. The peak responses of both regressive and progressive sensitive DNs are shown to occur at CFs of 8–10 Hz (Figs. 13, 14). |
18.
DAVID C. QUELLER 《Biological journal of the Linnean Society. Linnean Society of London》1984,23(2-3):133-143
Game theory models show that the evolution of interactions between relatives is determined by two kinds of fitness effects: Hamilton's inclusive fitness effect, and a frequency-dependent synergistic effect. The latter arises when an individual's behaviour has different effects on the fitness of interactants, depending on whether or not they perform the same behaviour. Knowing the sign of the synergistic effect is sufficient to understand most of the qualitative features of genetic models that show departures from Hamilton's rule. Since this synergistic effect does not depend on the interactants being related, it is best viewed as something distinct from kin selection. In this view, Hamilton's rule is basically correct for describing kin selection, and most deviations from it are due to the distinct process of synergistic selection. 相似文献
19.
用数学方法推导出了自交作物群体遗传组成的分析公式。根据所推出的公式,可以计算出任何自交世代群体的基因型频率和同一表现型中各基因型的频率。对自交群体遗传组成的分析可用于质量性状的选择,确定选择时需要的有效群体大小和选出有效群体的大小,亦有助于确定选择的最佳世代。 相似文献
20.
D. M. O'Malley R. P. Guries E. V. Nordheim 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1986,72(4):530-535
Summary Estimates of recombination frequency among enzyme loci of pitch pine revealed two new linkages, Mdh3:Pgm2 (=0.01) and Pep1:Mdh4 (=0.38), and confirmed two previously established linkages. Tighter linkage (=0.30) was ruled out for nearly all gene pairs examined. In general, the Bayesian approach used in this study to test for linkage performed better than alternative methods.This work was supported by the School of Natural Resources, College of Agricultural and Life Sciences, University of Wisconsin, Madison, WI, and by McIntyre-Stennis, project no. 142-C385 相似文献