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911.
Arikawa K. 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2003,189(11):791-800
Journal of Comparative Physiology A - This review outlines our recent studies on the spectral organization of butterfly compound eyes, with emphasis on the Japanese yellow swallowtail butterfly,... 相似文献
912.
Spiral and translation stimuli were used to investigate the response properties of cat AMLS (anteromedial lateral suprasylvian area) neurons to optic flow. The overwhelming majority of cells could be significantly excited by the two modes of stimuli and most responsive cells displayed obvious direction selectivity. It is the first time to find a visual area in mammalian brain preferring rotation stimuli. Two representative hypotheses are discussed here on the neural mechanism of optic flow analysis in visual cortex, and some new viewpoints are proposed to explain the experimental results. 相似文献
913.
Rosane Ness-Abramof Dan Nabriski Caroline M. Apovian Mark Niven Eliahu Weiss Menachem S. Shapiro Louis Shenkman 《Obesity (Silver Spring, Md.)》2002,10(12):1217-1221
Objective: Reevaluation of the validity of the 1-mg overnight dexamethasone suppression test (ODST) as a screening test for Cushing's syndrome in obese patients. Research Methods and Procedures: Eighty-six obese patients (body mass index, 30 to 53 kg/m2) that were referred to a general endocrine outpatient clinic for evaluation of simple obesity, diabetes mellitus, hypertension, polycystic ovary disease, or pituitary tumor. One milligram dexamethasone was administered orally at 11:00 pm , and serum cortisol levels were measured the following morning between 8:00 am and 9:00 am . Suppression of serum cortisol to <80 nM (3 μg/dL) was chosen as the cut-off point for normal suppression. Patients with serum cortisol levels ≥80 nM were evaluated for Cushing's syndrome. Results: Suppression of morning cortisol levels to <80 nM occurred in 79 of the 86 obese patients. Seven patients had serum cortisol levels higher than 80 nM; five were eventually diagnosed with Cushing's syndrome and two were considered false positive results in view of normal 24-hour free urinary cortisol and normal suppression on a low dose dexamethasone suppression test (0.5 mg of dexamethasone every 6 hours for 2 days). We found a false positive rate of 2.3% for the ODST using a cut-off serum cortisol of 80 nM. Discussion: The ODST is a valid screening test for Cushing's syndrome in the obese population. The false positive rate was 2.3%, even when using a strict cut-off serum cortisol of 80 nM. Abnormal cortisol suppression in obese patients should be investigated and not be considered false positive results. 相似文献
914.
Objective: The aim of this study was to examine the association between the clinical and biochemical features of the metabolic syndrome and quantity and type of alcohol intake in the severely obese. Research Methods and Procedures: A cross‐sectional study was performed in 486 consecutive severely obese subjects. Data on alcohol consumption was collected by serial clinical interviews and a questionnaire. The relationship between alcohol intake and the clinical and serum chemistry features of the metabolic syndrome was analyzed by multiple statistical techniques. Laboratory measures included lipid profile, fasting blood glucose, hemoglobin A1c, and fasting serum insulin. An indirect index of insulin resistance was calculated using the log‐transformed fasting insulin and glucose product. Results: There were 486 subjects, 84% women, with a mean age of 40.6 ± 10 years (range, 16 to 71 years) and a body mass index of 45.3 ± 7 kg/m2 (range, 34 to 77 kg/m2). Alcohol consumers (N = 276) showed a marked reduction in the adjusted odds ratio of type 2 diabetes (odds ratio = 0.29; 95% confidence interval, 0.16 to 0.55) compared with rare or nonconsumers (N = 210). There was a U‐shaped relationship between the amount and frequency of alcohol consumption and fasting triglyceride, fasting glucose, hemoglobin A1c, and index of insulin resistance measurements. Consumers of <100 g/wk had more favorable measures. The effect was attenuated when diabetics were excluded from the analysis. Timing of alcohol consumption did not influence outcome measures. Discussion: Light‐to‐moderate alcohol consumption is associated with a lower prevalence of type 2 diabetes, reduced insulin resistance, and more favorable vascular risk profile in the severely obese. We would propose that light to moderate alcohol consumption should not be discouraged in the severely obese. 相似文献
915.
Honeybee‐assisted wind pollination in bamboo Phyllostachys nidularia (Bambusoideae: Poaceae)? 总被引:1,自引:0,他引:1
SHUANG-QUAN HUANG HUN-FENG YANG IN LU YOSHITAKA TAKAHASHI 《Botanical journal of the Linnean Society. Linnean Society of London》2002,138(1):1-7
Floral syndromes and pollination of three species of Phyllostachys bamboos were studied in Central China in 1999 and 2000. All were protogynous. Stigmas were receptive and had pollen deposited on them 2 days before anther dehiscence. The period of anthesis in the three bamboos was 3 days. Individual pollen grains of the three species were similar in size (30–40 μm in diameter) and had features typical of wind-pollinated plants. The ratios of pollen to ovules (p/o ratio) in P . nidularia , P . heteroclada and P . nuda were 6500, 12 700 and 33 000, respectively. Mean pollen loads on each flower (one ovule) of these three species were 7.3, 8.8 and 9.4 grains, respectively. Pollen transfer in P . heteroclada and P . nuda depended on wind, and no flower visitors were seen in the field. However, in P . nidularia , Apis cerana Fab. was a frequent pollen collector observed from 1200 to 1330 h. The visits undertaken by thousands of honeybees resulted in a large number of pollen grains being released from the anthers in a short time (10–15 min) in one day, which accelerated and synchronized the release of pollen from the anthers that seemed to enhance the chance of pollination. Given that honeybees played an indirect role in pollen transfer this could partly explain the low p/o ratio in P . nidularia . Reviewing the literature, we found insect visits to flowers of bamboos were not infrequent phenomena. We suggest pollination efficiency should be considered as one selective factor in attempts to understand mast flowering in bamboo. © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society , 2002, 138 , 1–7. 相似文献
916.
The Electrical Hypersensitivity Syndrome (EHS) is a condition where people suffer from various nonspecific health symptoms attributed to an assumed adverse effect of electric and magnetic fields (EMF). Many EHS patients report the ability to consciously perceive EMF at very low intensities. The existence of a direct EMF perception could be the key to explain at least partially the aetiology of EHS through stress mechanisms and allow the comparison with well known environmental stressors such as noise or odor. The double blind laboratory experiment tested the hypothesis that there are subjects with the ability to perceive 50 Hz EMF at 100 V/m and 6 microT (EMF sensitive) and to investigate the prevalence of EMF sensitivity in a group consisting of subjects with or without self-reported EHS. A total of 63 volunteers, 49 with EHS and 14 controls, took part in the EMF perception experiment, where 10 sham and 10 exposed 2 min blocks had to be judged in randomized sequence (field on/field off). Seven out of 63 subjects reached a statistically significant result which points to the existence of a small EMF sensitive subgroup within the study group. There was no relevant difference between the subjects with self reported EHS and those without in terms of the success rate in the field perception experiment, as well as the number and types of symptoms encountered during the test. The results of the EMF perception experiment suggest that EHS is not a prerequisite for the ability to consciously perceive weak EMF and vice versa. 相似文献
917.
918.
Sara Frias Sandra Ramos Bertha Molina Victoria del Castillo Dora Gilda Mayn 《Mutation Research - Genetic Toxicology and Environmental Mutagenesis》2002,520(1-2):25-37
Down syndrome (DS) resulting from free trisomy 21 (FT21) has been largely associated with advanced maternal age. However, approximately 60% of FT21 cases are born to young couples. Thus, the etiological factors responsible for these FT21 children must differ from those proposed for maternal age-related FT21. These factors have not been defined. In this study, we analyzed the chromosomes of peripheral blood lymphocytes from three groups of couples aged ≤35 years, to identify chromosomal trisomies: Group I included 5 couples with normal offspring; Group II included 22 couples with one FT21 child; and Group III consisted of 3 couples with recurrent FT21. A total of 13,809 metaphases were analyzed with G-banding and 60,205 metaphases were analyzed with FISH using a 13/21 centromeric probe. Aneuploidy was significantly more frequent in Groups II and III. The frequencies of hyperdiploid cells were 0.19, 0.49 and 0.96% in Groups I–III, respectively. FISH analysis showed that trisomy 21 cell percentages were 0.08, 0.21 and 0.76 for Groups I–III, respectively, and were very similar to those obtained with G-banding. Trisomy 21 mosaicism was found in 2/22 couples with one FT21 offspring, and in 2/3 couples with recurrent FT21. Our data suggest that mosaicism is an important cause of FT21 offspring in young couples, and that aneuploidy is more frequent among couples with FT21 offspring. This may be related with age and other undetermined intrinsic and extrinsic factors. 相似文献
919.
Effects of multiple mating and male eye span on female reproductive output in the stalk-eyed fly, Cyrtodiopsis dalmanni 总被引:1,自引:0,他引:1
Baker Richard H.; Ashwell Robert I. S.; Richards Thomas A.; Fowler Kevin; Chapman Tracey; Pomiankowski Andrew 《Behavioral ecology》2001,12(6):732-739
Females of the stalk-eyed fly, Cyrtodiopsis dalmanni, mate
repeatedly during their lifetime and exhibit mating preferencefor males with large eye span. How these mating decisions affectfemale fitness is not fully understood. In this study, we examinedthe effects of multiple mating and male eye span on short-termreproductive output in this species. Experiments that manipulatedthe number of copulations and partners a female received suggested
that obtaining a sufficient sperm supply is an important benefitassociated with multiple mating. The average percentage offertile eggs laid by females increased as a function of matingfrequency and ranged from 40% for females mated once, to 80%for females mated continuously. In addition, a high proportionof copulations in this species appeared to be unsuccessful.
One-third of all females mated once laid less than 10% fertileeggs. There was no significant difference in reproductive performancebetween females mated to multiple partners and females matedto a single partner. There was also no indication that femalesreceived any short-term reproductive benefits from mating withmales with large eye span. In fact, females mated to males with
short eye span laid a higher percentage of fertile eggs thanfemales mated to large eye span males. 相似文献
920.
Clotilde Lepers Mathilde Dufay Sylvain Billiard 《Evolution; international journal of organic evolution》2014,68(12):3581-3598
The mode of pollination is often neglected regarding the evolution of selfing. Yet the distribution of mating systems seems to depend on the mode of pollination, and pollinators are likely to interfere with selfing evolution, since they can cause strong selective pressures on floral traits. Most selfing species reduce their investment in reproduction, and display smaller flowers, with less nectar and scents (referred to as selfing syndrome). We model the evolution of prior selfing when it affects both the demography of plants and pollinators and the investment of plants in pollination. Including the selfing syndrome in the model allows to predict several outcomes: plants can evolve either toward complete outcrossing, complete selfing, or to a stable mixed‐mating system, even when inbreeding depression is high. We predict that the evolution to high prior selfing could lead to evolutionary suicides, highlighting the importance of merging demography and evolution in models. The consequence of the selfing syndrome on plant–pollinator interactions could be a widespread mechanism driving the evolution of selfing in animal‐pollinated taxa. 相似文献