全文获取类型
收费全文 | 32506篇 |
免费 | 2607篇 |
国内免费 | 798篇 |
出版年
2023年 | 199篇 |
2022年 | 201篇 |
2021年 | 908篇 |
2020年 | 675篇 |
2019年 | 788篇 |
2018年 | 1011篇 |
2017年 | 741篇 |
2016年 | 1215篇 |
2015年 | 1858篇 |
2014年 | 2160篇 |
2013年 | 2296篇 |
2012年 | 2902篇 |
2011年 | 2643篇 |
2010年 | 1775篇 |
2009年 | 1456篇 |
2008年 | 1974篇 |
2007年 | 1801篇 |
2006年 | 1555篇 |
2005年 | 1402篇 |
2004年 | 1363篇 |
2003年 | 1096篇 |
2002年 | 1042篇 |
2001年 | 811篇 |
2000年 | 791篇 |
1999年 | 584篇 |
1998年 | 234篇 |
1997年 | 199篇 |
1996年 | 189篇 |
1995年 | 140篇 |
1994年 | 149篇 |
1993年 | 120篇 |
1992年 | 233篇 |
1991年 | 186篇 |
1990年 | 127篇 |
1989年 | 157篇 |
1988年 | 100篇 |
1987年 | 98篇 |
1986年 | 93篇 |
1985年 | 78篇 |
1984年 | 58篇 |
1983年 | 48篇 |
1982年 | 30篇 |
1981年 | 26篇 |
1979年 | 28篇 |
1978年 | 29篇 |
1977年 | 24篇 |
1976年 | 32篇 |
1975年 | 29篇 |
1973年 | 33篇 |
1969年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Travis Park Felix G. Marx Erich M. G. Fitzgerald Alistair R. Evans 《Journal of morphology》2017,278(6):801-809
The pygmy right whale, Caperea marginata , is the least understood extant baleen whale (Cetacea, Mysticeti). Knowledge on its basic anatomy, ecology, and fossil record is limited, even though its singular position outside both balaenids (right whales) and balaenopteroids (rorquals + grey whales) gives Caperea a pivotal role in mysticete evolution. Recent investigations of the cetacean cochlea have provided new insights into sensory capabilities and phylogeny. Here, we extend this advance to Caperea by describing, for the first time, the inner ear of this enigmatic species. The cochlea is large and appears to be sensitive to low‐frequency sounds, but its hearing limit is relatively high. The presence of a well‐developed tympanal recess links Caperea with cetotheriids and balaenopteroids, rather than balaenids, contrary to the traditional morphological view of a close Caperea‐balaenid relationship. Nevertheless, a broader sample of the cetotheriid Herpetocetus demonstrates that the presence of a tympanal recess can be variable at the specific and possibly even the intraspecific level. 相似文献
2.
Weilan Ye 《The EMBO journal》2014,33(8):786-787
Since metastatic lesions of solid tumors are the major cause of mortality in cancer patients, understanding the molecular mechanisms of metastasis is of paramount importance. Although extensive knowledge has been accumulated regarding the early steps in metastasis—starting with the departure of cancer cells from their primary sites, to their transit through the hematogenous and/or lymphatic systems, and ending with their entrance into the parenchyma of distant organs—it is difficult if not impossible to translate such knowledge into medicine due to the challenge of identifying patients with only primary tumors but otherwise pristine organs. In other words, autopsy studies indicate that a large proportion of patients already harbor dormant, undetectable micrometastases at the time of cancer diagnosis (Hensel et al, 2013 ). Accordingly, stopping tumor cell dissemination is too late for these patients. Therefore, understanding the survival and outgrowth of micrometastases may hold greater promise to combat metastatic disease. 相似文献
3.
4.
5.
6.
J.-Y. Roh H.-W. Park Y.-H. Je D.-W. Lee B.-R. Jin H.-W. Oh S. S. Gill & S.-K. Kang 《Letters in applied microbiology》1997,24(6):451-454
Bacillus thuringiensis NTB-1 isolated from soil samples in Korea produces ovoidal parasporal inclusions with proteins of approximately 24–40 kDa in size. Although serological study indicated that the isolate has a flagella (H) antigen identical with subsp. israelensis , it seemed to be non-insecticidal against Lepidoptera and Coleoptera as well as Diptera. To investigate the activity of non-insecticidal B. thuringiensis transformed with insecticidal crystal protein genes, cryIVD and cytA genes of B. thuringiensis subsp. morrisoni PG-14, highly toxic to mosquito larvae, were introduced into the isolate NTB-1. The expression of mosquitocidal crystal protein genes in NTB-1 was characterized by SDS–PAGE analysis and electron microscopy. The results showed that crystalline inclusions of host, CryIVD and CytA were stably expressed in the transformant. However, the mosquitocidal activity of transformant was similar to that of B. thuringiensis subsp. kurstaki Cry− B harbouring cryIVD and cytA genes, demonstrating that a synergistic effect by an interaction of both introduced insecticidal and resident non-insecticidal crystal proteins was not observed. 相似文献
7.
Bayesian nonparametric inference for panel count data with an informative observation process 下载免费PDF全文
In this paper, the panel count data analysis for recurrent events is considered. Such analysis is useful for studying tumor or infection recurrences in both clinical trial and observational studies. A bivariate Gaussian Cox process model is proposed to jointly model the observation process and the recurrent event process. Bayesian nonparametric inference is proposed for simultaneously estimating regression parameters, bivariate frailty effects, and baseline intensity functions. Inference is done through Markov chain Monte Carlo, with fully developed computational techniques. Predictive inference is also discussed under the Bayesian setting. The proposed method is shown to be efficient via simulation studies. A clinical trial dataset on skin cancer patients is analyzed to illustrate the proposed approach. 相似文献
8.
9.
Transient Receptor Potential, Melastatin-related, member 4 (TRPM4) channels are Ca2+-activated Ca2+-impermeable cation channels. These channels are expressed in various types of mammalian tissues including the brain and are implicated in many diverse physiological and pathophysiological conditions. In the past several years, the trafficking processes and regulatory mechanism of these channels and their interacting proteins have been uncovered. Here in this minireview, we summarize the current understanding of the trafficking mechanism of TRPM4 channels on the plasma membrane as well as heteromeric complex formation via protein interactions. We also describe physiological implications of protein-TRPM4 interactions and suggest TRPM4 channels as therapeutic targets in many related diseases. [BMB Reports 2015; 48(1): 1-5] 相似文献
10.
R. A. Ben-Ruwin S. Rogers K. Walter R. W. A. Park 《Letters in applied microbiology》1990,11(5):244-246
Aeromonas bacteria (110 strains) from a variety of clinical, food and environmental sources, were identified using routine biochemical tests. Concurrently they were tested aerobically and anaerobically for their ability to perform synergistic haemolysis with Staphylococcus aureus (the 'CAMP' reaction). Results did not support a reported observation that the 'CAMP' reaction can he used to facilitate speciation of Aeromonas bacteria. 相似文献