全文获取类型
收费全文 | 19484篇 |
免费 | 1434篇 |
国内免费 | 1361篇 |
专业分类
22279篇 |
出版年
2024年 | 52篇 |
2023年 | 290篇 |
2022年 | 632篇 |
2021年 | 1063篇 |
2020年 | 713篇 |
2019年 | 892篇 |
2018年 | 803篇 |
2017年 | 618篇 |
2016年 | 882篇 |
2015年 | 1255篇 |
2014年 | 1475篇 |
2013年 | 1512篇 |
2012年 | 1768篇 |
2011年 | 1531篇 |
2010年 | 958篇 |
2009年 | 822篇 |
2008年 | 957篇 |
2007年 | 774篇 |
2006年 | 727篇 |
2005年 | 581篇 |
2004年 | 531篇 |
2003年 | 470篇 |
2002年 | 408篇 |
2001年 | 373篇 |
2000年 | 345篇 |
1999年 | 312篇 |
1998年 | 204篇 |
1997年 | 188篇 |
1996年 | 176篇 |
1995年 | 153篇 |
1994年 | 116篇 |
1993年 | 106篇 |
1992年 | 132篇 |
1991年 | 110篇 |
1990年 | 96篇 |
1989年 | 58篇 |
1988年 | 46篇 |
1987年 | 49篇 |
1986年 | 25篇 |
1985年 | 26篇 |
1984年 | 16篇 |
1983年 | 20篇 |
1982年 | 4篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
11.
郭新亮 《中国野生植物资源》2019,(2):29-35,47
通过施肥措施对鳄嘴花[Clinacanthus nutans(Burm. f.) Lindau]生物量分配的影响研究得到,鳄嘴花各构件生物量与各构件生物量的分配比例并不总是一致。N肥处理组根茎叶以及总生物量均较K低。P肥则为处理4根茎叶以及总生物量较大。而K肥根茎生物量较大的均为处理5,叶和总生物量较大的则为处理4。有机肥的施肥效果对鳄嘴花各构件生物量的促进效果均较差。施肥配比中,各个施肥配比对根、茎生物量的增加效果均较差。叶和总生物量中,则为N1∶P1∶K1效果较好。总体来看,合理施肥对鳄嘴花生物量的增加有促进作用,对生物量的分配产生一定的影响。 相似文献
12.
Jin Yan Dong Xing Ping Li Lei Li Guo Hong Li Ya Jun Liu Ke Qin Zhang 《Annals of microbiology》2006,56(2):163-166
One hundred and eighty one fungal species that were isolated from the fresh fruiting bodies collected in the Mountains of Pu Er County of Yunnan Province, China were tested on the pine wood nematode,Bursaphelenchus xylophilus in vitro. Each fungal species was grown in Czapek broth and potato dextrose broth (PDB). Fifteen filtrates fromAmauroderma austrosinense, Amauroderma macer, Filoboletus sp.,Laccaria tortilis, Lactarius gerardii, Lentinula edodes, Oudemansiella longipes, Oudemansiella mucida, Peziza sp.,Pleurotus sp.,Sinotermitomyces carnosus (two strains),Strobilomyces floccopus, Termitomyces albuminosus, Tylopilus striatulus grown on PDB were found to be pathogenic to the tested nematodes. Eleven filtrates fromAmanita junguillea, Amanita sp.,Daedalea sepiaria, Fistulina hepatica, Omphalotus olearius, Oudemansiella mucida, Peziza sp.,Pleurotus pulmatus, Ramaria sp.,Tricholoma conglobatum, Tylopilus striatulus grown on Czapek broth were also pathogenic to the nematodes. When screening for nematicidal potential of fungi, it is important to study the growth medium conditions necessary to obtain the optimal nematicidal effect as fungal filtrates growing on different liquid media showed a very inconsistent toxicity towards nematodes. 相似文献
13.
M. Kawasaki J. Prather Y. -X. Guo 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1996,178(4):453-462
The sensory cues for a less known form of frequency shifting behavior, gradual frequency falls, of electric organ discharges (EODs) in a pulse-type gymnotiform electric fish, Rhamphichthys rostratus, were identified. We found that the gradual frequency fall occurs independently of more commonly observed momentary phase shifting behavior, and is due to perturbation of sensory feedback of the fish's own EODs by EODs of neighboring fish. The following components were identified as essential features in the signal mixture of the fish's own and the neighbor's EOD pulses: (1) the neighbor's pulses must be placed within a few millisecond of the fish's own pulses, (2) the neighbor's pulses, presented singly at low frequencies (0.2–4 Hz), were sufficient, (3) the frequency of individual pulse presentation must be below 4 Hz, (4) amplitude modulation of the sensory feedback of the fish's own pulses induced by such insertions of the neighbor's pulses must contain a high frequency component: sinusoidal amplitude modulation of the fish's own EOD feedback at these low frequencies does not induce gradual frequency falls. Differential stimulation across body surfaces, which is required for the jamming avoidance response (JAR) of wave-type gymnotiform electric fish, was not necessary for this behavior. We propose a cascade of high-pass and low-pass frequency filters within the amplitude processing pathway in the central nervous system as the mechanism of the gradual frequency fall response.Abbreviations
EOD
electric organ discharge
-
f
frequency of EOD or pacemaker command signal
-
JAR
jamming avoidance response
-
S
1
stimulus mimicking fish's own EOD
-
f
1
frequency of S1
-
S
2
stimulus mimicking neighbor's EOD
-
f
2
frequency of S2 相似文献
14.
15.
16.
The neurocognitive basis of memory retrieval is often examined by investigating brain potential old/new effects, which are differences in brain activity between successfully remembered repeated stimuli and correctly rejected new stimuli in a recognition test. In this study, we combined analyses of old/new effects for words with an item-method directed-forgetting manipulation in order to isolate differences between the retrieval processes elicited by words that participants were initially instructed to commit to memory and those that participants were initially instructed to forget. We compared old/new effects elicited by to-be-forgotten (TBF) words with those elicited by to-be-remembered (TBR) words in both an explicit-memory test (a recognition test) and an implicit-memory test (a lexical-decision test). Behavioral results showed clear directed forgetting effects in the recognition test, but not in the lexical decision test. Mirroring the behavioral findings, analyses of brain potentials showed evidence of directed forgetting only in the recognition test. In this test, potentials from 450–650 ms (P600 old/new effects) were more positive for TBR relative to TBF words. By contrast, P600 effects evident during the lexical-decision test did not differ in magnitude between TBR and TBF items. When taken in the context of prior studies that have linked similar parietal old/new effects to the recollection of episodic information, these data suggest that directed-forgetting effects manifest primarily in greater episodic retrieval by TBR than TBF items, and that retrieval intention may be important for these directed-forgetting effects to occur. 相似文献
17.
Li Guo Ziya Huang Xingyu Chen Min Yang Miaomiao Yang Ziwei Liu Xuejie Han Xiangjie Ma Xiaoli Wang Qiguo Gao 《植物学报(英文版)》2023,65(10):2395-2406
Pollen hydration on dry stigmas is strictly regulated by pollen–stigma interactions in Brassicaceae. Although several related molecular events have been described, the molecular mechanism underlying pollen hydration remains elusive. Multiple B-class pollen coat proteins(PCP-Bs) are involved in pollen hydration. Here, by analyzing the interactions of two PCP-Bs with three Arabidopsis thaliana stigmas strongly expressing S-domain receptor kinase(SD-RLK), we determined that SD-RLK28 directly intera... 相似文献
18.
19.
Zhongkai Hao Qi Chen Wenrui Dai Yinjuan Ren Yin Zhou Jinlin Yang Sijie Xie Yanbin Shen Jihong Wu Wei Chen Guo Qin Xu 《Liver Transplantation》2020,10(10)
Developing a titanium dioxide (TiO2)‐based anode with superior high‐rate capability and long‐term cycling stability is important for efficient energy storage. Herein, a simple one‐step approach for fabricating blue TiO2 nanoparticles with oxygen vacancies is reported. Oxygen vacancies can enlarge lattice spaces, lower charge transfer resistance, and provide more active sites in TiO2 lattices. As a result, this blue TiO2 electrode exhibits a highly reversible capacity of 50 mAh g?1 at 100 C (16 800 mA g?1) even after 10 000 cycles, which is attributable to the combination of surface capacitive process and remarkable diffusion‐controlled insertion revealed by the kinetic analysis. The strategy of employing oxygen‐deficient nanoparticles may be extended to the design of other robust semiconductor materials as electrodes for energy storage. 相似文献
20.
Bo Cao Yanfeng Qi Yan Yang Xichun Liu Duo Xu Wei Guo Yang Zhan Zhenggang Xiong Allen Zhang Alun R. Wang Xueqi Fu Haitao Zhang Lijing Zhao Jingkai Gu Yan Dong 《PloS one》2014,9(11)
Castration-resistant progression of prostate cancer after androgen deprivation therapies remains the most critical challenge in the clinical management of prostate cancer. Resurgent androgen receptor (AR) activity is an established driver of castration-resistant progression, and upregulation of the full-length AR (AR-FL) and constitutively-active AR splice variants (AR-Vs) has been implicated to contribute to the resurgent AR activity. We reported previously that ginsenoside 20(S)-protopanaxadiol-aglycone (PPD) can reduce the abundance of both AR-FL and AR-Vs. In the present study, we further showed that the effect of PPD on AR expression and target genes was independent of androgen. PPD treatment resulted in a suppression of ligand-independent AR transactivation. Moreover, PPD delayed castration-resistant regrowth of LNCaP xenograft tumors after androgen deprivation and inhibited the growth of castration-resistant 22Rv1 xenograft tumors with endogenous expression of AR-FL and AR-Vs. This was accompanied by a decline in serum prostate-specific antigen levels as well as a decrease in AR levels and mitoses in the tumors. Notably, the 22Rv1 xenograft tumors were resistant to growth inhibition by the next-generation anti-androgen enzalutamide. The present study represents the first to show the preclinical efficacy of PPD in inhibiting castration-resistant progression and growth of prostate cancer. The findings provide a rationale for further developing PPD or its analogues for prostate cancer therapy. 相似文献