全文获取类型
收费全文 | 5821篇 |
免费 | 510篇 |
国内免费 | 3篇 |
出版年
2023年 | 37篇 |
2022年 | 102篇 |
2021年 | 168篇 |
2020年 | 120篇 |
2019年 | 128篇 |
2018年 | 155篇 |
2017年 | 142篇 |
2016年 | 170篇 |
2015年 | 286篇 |
2014年 | 292篇 |
2013年 | 393篇 |
2012年 | 445篇 |
2011年 | 403篇 |
2010年 | 296篇 |
2009年 | 249篇 |
2008年 | 263篇 |
2007年 | 256篇 |
2006年 | 224篇 |
2005年 | 199篇 |
2004年 | 182篇 |
2003年 | 175篇 |
2002年 | 159篇 |
2001年 | 82篇 |
2000年 | 84篇 |
1999年 | 57篇 |
1998年 | 42篇 |
1997年 | 55篇 |
1996年 | 53篇 |
1995年 | 34篇 |
1994年 | 42篇 |
1993年 | 41篇 |
1992年 | 61篇 |
1991年 | 42篇 |
1990年 | 47篇 |
1989年 | 40篇 |
1988年 | 36篇 |
1987年 | 48篇 |
1986年 | 44篇 |
1985年 | 56篇 |
1984年 | 33篇 |
1983年 | 29篇 |
1982年 | 35篇 |
1981年 | 39篇 |
1980年 | 24篇 |
1979年 | 37篇 |
1978年 | 30篇 |
1977年 | 38篇 |
1975年 | 31篇 |
1973年 | 26篇 |
1972年 | 27篇 |
排序方式: 共有6334条查询结果,搜索用时 15 毫秒
1.
Lucas Henriques Viscardi Danilo Oliveira Imparato Maria Ctira Bortolini Rodrigo Juliani Siqueira Dalmolin 《Molecular biology and evolution》2021,38(3):735
The origin of nervous systems is a main theme in biology and its mechanisms are largely underlied by synaptic neurotransmission. One problem to explain synapse establishment is that synaptic orthologs are present in multiple aneural organisms. We questioned how the interactions among these elements evolved and to what extent it relates to our understanding of the nervous systems complexity. We identified the human neurotransmission gene network based on genes present in GABAergic, glutamatergic, serotonergic, dopaminergic, and cholinergic systems. The network comprises 321 human genes, 83 of which act exclusively in the nervous system. We reconstructed the evolutionary scenario of synapse emergence by looking for synaptic orthologs in 476 eukaryotes. The Human–Cnidaria common ancestor displayed a massive emergence of neuroexclusive genes, mainly ionotropic receptors, which might have been crucial to the evolution of synapses. Very few synaptic genes had their origin after the Human–Cnidaria common ancestor. We also identified a higher abundance of synaptic proteins in vertebrates, which suggests an increase in the synaptic network complexity of those organisms. 相似文献
2.
3.
Spencer G. Lucas Bolat U. Bayshashov Lyubov A. Tyutkova Ayzhan K. Zhamangara Bolat Z. Aubekerov 《Pal?ontologische Zeitschrift》1997,71(3-4):305-314
At Aktau Mountain in the Ili depression of eastern Kazakstan, fossil mammals that encompass the Paleogene-Neogene boundary occur at three stratigraphic levels. The lowest level is in the lower Kyzylbulak Formation and produces Brontotheriidae and the hyracodontidArdynia and is tentatively assigned a late Eocene (Ergilian) age. The lower part of the overlying Aktau Formation produces fossils of the giant rhinocerosParaceratherium and is tentatively assigned a late Oligocene (Tabenbulukian) age. The upper part of the Aktau Formation yields a fossil mammal assemblage that includesGomphotherium,Stephanocemas, Brachypotherium andLagomeryx. It is clearly of Miocene age, probably late early Miocene (late Burdigalian), a correlative of European Reference Level MN 5 and the late Shanwangian of China. The Paleogene-Neogene boundary at Aktau Mountain thus is in the Aktau Formation. 相似文献
4.
Ralf Heinrich Peter Bräunig Ismeni Walter Henning Schneider Edward A. Kravitz 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2000,186(7-8):617-629
In the American lobster (Homarus americanus) the biogenic amines serotonin and octopamine appear to play important and opposite roles in the regulation of aggressive behavior, in the establishment and/or maintenance of dominant and subordinate behavioral states and in the modulation of the associated postural stances and escape responses. The octopamine-containing neurosecretory neurons in the thoracic regions of the lobster ventral nerve cord fall into two morphological subgroups, the root octopamine cells, a classical neurohemal group with release regions along second thoracic roots, and the claw octopamine cells, a group that selectively innervates the claws. Cells of both subgroups have additional sets of endings within neuropil regions of ganglia of the ventral nerve cord. Octopamine neurosecretory neurons generally are silent, but when spontaneously active or when activated, they show large overshooting action potentials with prominent after-hyperpolarizations. Autoinhibition after high-frequency firing, which is also seen in other crustacean neurosecretory cells, is readily apparent in these cells. The cells show no spontaneous synaptic activity, but appear to be excited by a unitary source. Stimulation of lateral or medial giant axons, which excite serotonergic cells yielded no response in octopaminergic neurosecretory cells and no evidence for direct interactions between pairs of octopamine neurons, or between the octopaminergic and the serotonergic sets of neurosecretory neurons was found. 相似文献
5.
6.
Alba Luengo Zhaoqi Li Dan Y. Gui Lucas B. Sullivan Maria Zagorulya Brian T. Do Raphael Ferreira Adi Naamati Ahmed Ali Caroline A. Lewis Craig J. Thomas Stefani Spranger Nicholas J. Matheson Matthew G. Vander Heiden 《Molecular cell》2021,81(4):691-707.e6
- Download : Download high-res image (172KB)
- Download : Download full-size image
7.
8.
G L Lucas 《Plastic and reconstructive surgery》1987,80(1):92-94
Fowler's central slip tenotomy for old mallet deformity is a well-known, but apparently seldom used procedure. Although the vast majority of patients with mallet finger can be successfully treated by well-known conservative techniques, occasional patients, such as the 11 reported here, will have enough difficulty with a chronic mallet finger to warrant rebalancing of the extensor apparatus by means of central slip tenotomy. 相似文献
9.
Blanco Pablo J. Müller Lucas O. Watanabe Sansuke M. Feijóo Raúl A. 《Biomechanics and modeling in mechanobiology》2020,19(5):1663-1678
Biomechanics and Modeling in Mechanobiology - The goal of this work is to assess the impact of vascular anatomy definition degree in the predictions of blood flow models of the arterial network. To... 相似文献
10.
The signal sequence suffices to direct export of outer membrane protein OmpA of Escherichia coli K-12. 总被引:8,自引:3,他引:5
下载免费PDF全文
![点击此处可从《Journal of bacteriology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
We studied whether information required for export is present within the mature form of the Escherichia coli 325-residue outer membrane protein OmpA. We had previously analyzed overlapping internal deletions in the ompA gene, and the results allowed us to conclude that if such information exists it must be present repeatedly within the membrane part of the protein encompassing amino acid residues 1 to 177 (R. Freudl, H. Schwarz, M. Klose, N. R. Movva, and U. Henning, EMBO J. 4:3593-3598, 1985). A deletion which removed the codons for amino acid residues 1 to 229 of the OmpA protein was constructed. In this construct the signal sequence was fused to the periplasmic part of the protein. The resulting protein, designated Pro-OmpA delta 1-229, was processed, and the mature 95-residue protein accumulated in the periplasm. Hence, information required for export does not exist within the OmpA protein. 相似文献