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991.
浑太流域洪涝灾害及其治理方略 总被引:1,自引:0,他引:1
抚顺、鞍山、辽阳等在内的中部城市群提供年用水量7.0×109m3的70%[5],对辽宁经济发展与生态环境建设具有至关重要的作用.本文试图剖析浑河、太子河洪涝灾害问题,找出其成因与特点,从生态与工程结合角度提出治理方略,为防洪减灾,振兴经济服务.2 洪涝灾害成因分析2.1 洪涝灾害的一般分析 洪涝灾害是天降暴雨和下垫面综合作用的结果.它通常依赖气象、水文地理和生态环境三方面因素.气象因素主要指暴雨,包括雨量、雨强和降雨落区.暴雨主要受大气环境制约,目前人类难以左右.然而,通过人工控制增减局地降雨… 相似文献
992.
山岳型风景旅游区生态负荷与环境建设研究:泰山实证分析 总被引:13,自引:0,他引:13
运用旅游生态学原理和方法,提出了测算山岳型风景旅游区生态负荷综合分级指数的8项1级指标和6项2级指标及计算模式。以泰山风景旅游区为案例进行了应用研究,将13个地块单元(功能区)按生态负荷强度大小划分为3级,并依据可持续发展理论提出了强负荷区生态补偿的方案,为山岳型风景旅游区寻求环境与旅游经济活动的协调发展提供可借鉴的研究方案和具体措施. 相似文献
993.
杭州石荠苧(Mosla hangchowensis)的种子完全靠风传播,但由于种子大,传播距离不远;种子在冬季休眠,春天(2月末3月初)萌发,种子萌发率很低,尤其是水选上层种子,主要原因是质量差。杭州石荠苧的营养期从3月初到8月上旬,株高在8月中旬以前基本为匀速增加,早期生长极为缓慢。形态和生殖力的环境可塑性极强,自然生长的植株冠幅变动在4~5616cm2之间。杭州石荠苧在自然生境中有时形成单优群落,通常与其它植物伴生。由于早期生长慢,限制了其在群落中的竞争能力,在土壤条件好的地方绝大部分被排挤掉,只是由于其极强的耐旱能力才在高温、干旱、土少的生境中得以存活。 将同属不濒危的华荠苧与之比较,其种子小于杭州石荠苧,但萌发率却高于杭州石荠苧。华荠苧的植株较矮,花色不如杭州石荠苧鲜艳,同在路边生长,不像杭州石荠苧那样容易被人采摘;华荠苧的根较杭州石荠苧的根深,抗雨水冲刷能力较强。华荠苧在自然生境中植株投入生殖的比例大于杭州石荠苧。 相似文献
994.
Intraflock variation in the speed of escape-flight response on attack by an avian predator 总被引:7,自引:2,他引:5
The benefits of flocking to prey species, whether through collective
vigilance,dilution of risk, or predator confusion, depend on flock members
respondingin a coordinated way to attack. We videotaped sparrowhawks
attackingredshank flocks to determine if there were differences in thetiming
of escape flights between flock members and the factorsthat might affect any
differences. Sparrowhawks are surpriseshort-chase predators, so variation in
the time taken to takeflight on attack is likely to be a good index of
predation risk.Most birds in a flock flew within 0.25 s of the first bird
flying,and all birds were flying within 0.7 s. Redshanks that werevigilant,
that were closest to the approaching raptor, and thatwere close to their
neighbors took flight earliest within aflock. Birds in larger flocks took
longer, on average, to takeflight, measured from the time that the first bird
in the flockflew. Most birds took flight immediately after near neighbors
tookoff, but later flying birds were more likely to fly immediatelyafter
more distant neighbors took flight. This result, alongwith the result that
increased nearest neighbor distance increasedflight delay, suggests that most
redshanks flew in responseto conspecifics flying. The results strongly
suggest that thereis significant individual variation in predation risk
withinflocks so that individuals within a flock will vary in benefitsthat
they gain from flocking. 相似文献
995.
Larval damselflies frequently engage in aggressive interactions that may increase their risk of fish predation. To test this we analyzed the behavior of larval Ischnura verticalis exposed to both conspecifics and fish predators. Larvae in the presence of conspecifics oriented, struck, and swam more but crawled less compared to solitary larvae; the presence of fish reduced, or tended to reduce, all behaviors. Fish struck more at interacting larvae compared to noninteracting larvae. Increased attack rate by fish likely reflects the increase in the very active swimming behavior by larvae and suggests a conflict between antipredator behaviors. Swimming is an appropriate response to avoid predation by odonate larvae which normally ambush prey but is clearly dangerous when fast-swimming fish that cue in on movement are nearby. 相似文献
996.
This study shows that, as with its intertidal counterpart, Nassarius festivus, the rate at which subtidal Nassarius siquijorensis moves towards food bait is similar for starved and well-fed individuals. This study also investigates another facet of nassariid nutrition related to the degree of hunger, i.e. the effect of simulated predation upon a feeding assemblage. Individuals which fed within 7 days, cease feeding and depart palatable food if crushed conspecifics are added. Between 7 and 13 days since its last meal, however, N. siquijorensis will feed when food is available, despite the possibility of predation. For the intertidal N. festivus, the critical time for hunger to override the risk of predation is between 14 and 21 days. The difference between subtidal and intertidal species may be due to a difference, in terms of days, that a meal can provide for their energy expenditure, particularly with regard to respiration. The bigger, subtidal, N. siquijorensis needs to feed more frequently than the smaller, intertidal, N. festivus. 相似文献
997.
鸟击防控是一个世界性难题。家鸽(Columba livia domestica)是机场生物多样性调查中最常见鸟类,也是历史上鸟击高危物种之一,还是唯一由于人工大量放飞导致严重鸟击事故的物种。2020年9月至2021年1月,在我国4个机场,针对机场周边23家鸽户,共149只家鸽开展卫星追踪放飞实验研究,获得了家鸽个体在机场周边的飞行时间、飞行距离、飞行高度等个体运动参数。研究发现,1)单次放飞时长多在1 ~ 4 h,单次平均放飞时长为(2.9 ± 1.6)h。在鸽户自主放飞家鸽和家鸽自由回笼的动态过程中,下午活动在外的家鸽数量较多,尤其15:00 ~ 17:59时段是活动在外家鸽数量最多的时段。2)飞行距离多在3.0 km范围内,最远可达8.9 km;存在家鸽飞行范围覆盖机场现象的鸽户占比45%。3)飞行高度主要在200 m及以下,平均飞行高度为(29 ± 28)m。本研究结果表明,下午,尤其是15:00 ~ 17:59时段应作为家鸽防控的重点时段,机场周边10 km以及高度0 ~ 200 m的范围应作为家鸽防控的重点空间范围。根据《中华人民共和国民用航空法(2021修正)》第五十八条明确规定“不得饲养、放飞影响飞行安全的鸟类动物和其他物体”,需要建立相应的问责机制、加强有效监管,以降低家鸽鸟击风险。 相似文献
998.
Selection due to cuckoo parasitism is responsible for the evolution of anti-parasitism defenses in hosts. Different host species breeding sympatrically with a single parasitic cuckoo may evolve different strategies to reduce the risk of counter cuckoo parasitism, resulting in different interactions between cuckoos and hosts in areas of sympatry. Here, we studied the coevolutionary interactions between Himalayan cuckoos Cuculus saturatus and 2 sympatric and closely related potential hosts belonging to the family Pycnonotidae, the brown-breasted bulbul Pycnonotus xanthorrhous and the collared finchbill Spizixos semitorques. We investigated parasitism rates and nest-site selection (nest height, nest cover, human disturbance, perch height, forest distance, and degree of concealment) related to parasitism risk, nest defense against a cuckoo dummy, and egg rejection against cuckoo model eggs. Bulbuls used specific nest sites that were further away from forests than those of finchbills, and they behaved more aggressively toward cuckoos than finchbills. In contrast, bulbuls possessed moderate egg rejection ability, whereas the finchbill rejected 100% of cuckoo model eggs. We suggest that selection of a nest site away from forests by the bulbul explains the absence of parasitism by Himalayan cuckoos. We suggest that these interspecific differences in nest-site selection and nest defense indicate alternative responses to selection due to cuckoos. 相似文献
999.
1000.
Jamil M Neto Marina GM Viturino Galina Ananina Flvia F Bajano Sueli M da S Costa Alicia B Roque Gessica FS Borges Raissa Franchi Priscila HH Rim Flvio M Medina Fernando F Costa Mnica B de Melo Jos PC de Vasconcellos 《Experimental biology and medicine (Maywood, N.J.)》2021,246(21):2290
This study aimed to investigate the association among genetic variants of the complement pathway CFB R32Q (rs641153), C3 R102G (rs2230199), and CFH (rs1410996) with age-related macular degeneration (AMD) in a sample of the Brazilian population. In a case-control study, 484 AMD patients were classified according to the clinical age-related maculopathy grading system (CARMS) and compared to 479 unrelated controls. The genetic variants rs1410996 of complement H (CFH), rs641153 of complement factor B (CFB), and rs2230199 of complement 3 (C3) were evaluated through polymerase chain reaction (PCR) and direct sequencing. The associations between single nucleotide polymorphisms (SNPs) and AMD, adjusted by age, were assessed by using logistic regression models. A statistically significant association was observed between AMD risk and rs2230199 variant with an OR of 2.01 (P = 0.0002) for CG individuals compared to CC individuals. Regarding the comparison of advanced AMD versus the control group, the OR was 2.12 (P = 0.0036) for GG versus AA genotypes for rs1410996 variant. Similarly, the OR for rs2230199 polymorphism was 2.3034 (P = 5.47e-05) when comparing CG individuals to CC carriers. In contrast, the rs641153 variant showed a significant protective effect against advanced AMD for GA versus GG genotype (OR = 0.4406; P = 0.0019). When comparing wet AMD versus controls, a significant association was detected for rs1410996 variant (OR = 2.16; P = 0.0039) comparing carriers of the homozygous GG versus AA genotype, as well as in the comparisons of GG (OR = 3.0713; P = 0.0046) and CG genotypes (OR = 2.2249; P = 0.0002) versus CC genotype for rs2230199 variant, respectively. The rs641153 variant granted a significant protective effect against wet AMD for GA versus GG genotypes (OR = 0.4601; P = 0.0044). Our study confirmed the risk association between rs2230199 and rs1410996 variants and AMD, and the protective role against AMD for rs641153 variant. 相似文献