全文获取类型
收费全文 | 18266篇 |
免费 | 1295篇 |
国内免费 | 5篇 |
专业分类
19566篇 |
出版年
2023年 | 61篇 |
2022年 | 83篇 |
2021年 | 191篇 |
2020年 | 131篇 |
2019年 | 152篇 |
2018年 | 299篇 |
2017年 | 266篇 |
2016年 | 393篇 |
2015年 | 700篇 |
2014年 | 781篇 |
2013年 | 971篇 |
2012年 | 1324篇 |
2011年 | 1865篇 |
2010年 | 1073篇 |
2009年 | 989篇 |
2008年 | 867篇 |
2007年 | 842篇 |
2006年 | 796篇 |
2005年 | 794篇 |
2004年 | 721篇 |
2003年 | 672篇 |
2002年 | 615篇 |
2001年 | 363篇 |
2000年 | 409篇 |
1999年 | 310篇 |
1998年 | 168篇 |
1997年 | 136篇 |
1996年 | 140篇 |
1995年 | 113篇 |
1994年 | 110篇 |
1993年 | 102篇 |
1992年 | 187篇 |
1991年 | 191篇 |
1990年 | 192篇 |
1989年 | 140篇 |
1988年 | 183篇 |
1987年 | 149篇 |
1986年 | 143篇 |
1985年 | 135篇 |
1984年 | 145篇 |
1983年 | 93篇 |
1982年 | 87篇 |
1981年 | 82篇 |
1980年 | 60篇 |
1979年 | 121篇 |
1978年 | 88篇 |
1977年 | 84篇 |
1975年 | 82篇 |
1974年 | 73篇 |
1973年 | 76篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
Hagemann Joh Buder Ramshorn I. Grebenščikov J. Schöneich Alfred Lein F. Fabig G. Tembrock A. J. Müller 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1964,34(5):229-232
Ohne Zusammenfassung 相似文献
43.
44.
Lubomír Scháněl 《Biologia Plantarum》1966,8(4):292-298
Mycelium of white-rot fungi secretes laccase into the medium. It was found by cultivation on malt-agar plates that the mycelium does not produce laccase equally in all its parts. The youngest hyphae at the margins of the colony represent usually the maximum producers, whereas older hyphae produce less or none at all. An exception here isCollybia velutipes which is the weakest producer of laccase of all the fungi studied and where only the older hyphae begin to secrete it. Manometric estimation of laccase showed that maximum specific activity of laccase is achieved at the boundary between the phases of initial and linear growth and i11 some cases during the first half of linear growth. Ageing of the mycelium characterized by certain changes in its metabolism is reflected in changes of enzyme production by fungal hypha of different age. 相似文献
45.
W. Kreil Unger Hans Rundfeldt P. Metzner G. Schönberg K. Naumann Nover R. Schiemann H. Grimm P. Heriwig 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1965,35(8):374-376
Ohne Zusammenfassung 相似文献
46.
Humoral anti-idiotypic and anti-anti-idiotypic immune response in cancer patients treated with monoclonal antibody 17-1A 总被引:4,自引:0,他引:4
Peter Ragnhammar Maria Liljefors Anna-Lena Hjelm Håkan Mellstedt Jan-Erik Frödin J. Fagersberg 《Cancer immunology, immunotherapy : CII》1996,42(2):81-87
A group of 96 patients with advanced colorectal carcinoma were treated with the mouse (m) or chimeric (c) (mouse variable
regions × human IgG1 constant regions) monoclonal antibody (mAb) 17-1A recognizing the tumour-associated antigen GA733-2.
Eighty-two of the 83 patients treated with mmAb17-1A and 69% of the patients given cmAb17-1A (n = 13) developed anti-idiotypic antibodies (ab2). Auto-antibodies binding to tumour cells expressing GA733-2 were found in 7% of the patients. In a further 38 patients (40%)
antitumour-cell antibodies, i.e. anti-anti-idiotypic antibodies (ab3), were induced by the mAb17-1A therapy. Patients with detectable ab3 after treatment had significantly higher ab2 levels than those not developing ab3. Addition of granulocyte/macrophage-colony-stimulating factor (GM-CSF) to mmAb17-1A significantly enhanced the induction
of ab2 as well as induction of anti-anti-idiotypic antibodies (ab3), compared to mmAb17-1A alone. Patients with a high increase in antitumour-cell antibodies (ab3) induced by the therapy lived significantly longer than patients with no or a low level of induction of ab3 (P = 0.016). The results indicate that induction of an idiotypic network response might be an important effector mechanism in
mAb therapy.
Received: 20 October 1995 / Accepted: 18 December 1995 相似文献
47.
Markus Kurz Karin Schütz Michael Göbel 《Origins of life and evolution of the biosphere》1996,26(3-5):263-264
48.
The 13 kDa acidic seminal fluid protein (aSFP) is a major component of bovine semen exerting growth factor-like activity. The influence of the pure protein on sperm viability was observed by evaluating sperm motility using computer-assisted semen analysis. Furthermore, mitochondrial dehydrogenase activity as a parameter of sperm metabolism and the integrity of sperm membranes using a metal catalyzed lipid peroxidation assay were measured. Over a wide physiological range (0.003 to 4 g/l) aSFP did not influence motility and average-path velocity of sperm, but at the highest concentration (6 g/l) a significant reduction in motility could be observed. Mitochondrial activity was significantly stimulated at medium concentrations (0.125 to 2 g/l), whereas a 40% suppression was observed at maximum levels (4 g/l). A dose-dependent inhibition of lipid peroxidation could be demonstrated for medium and high concentrations of aSFP (0.125 to 4 g/l). Compared with other reducing agents, aSFP showed the highest potency in preventing oxidative stress. Such effects might be explained by the remarkable redox behavior of the protein. We suggest that in the bull aSFP may play a role in the regulation of sperm metabolism and the protection of sperm membranes from oxidative damage. 相似文献
49.
Kinetics of excited states of pigment clusters in solubilized light-harvesting complex II: photon density-dependent fluorescence yield and transmittance. 下载免费PDF全文
R Sch?del F Hillmann T Schr?tter J Voigt K D Irrgang G Renger 《Biophysical journal》1996,71(6):3370-3380
Relative fluorescence yield, phi F, and transmittance, T, were measured in solubilized light-harvesting complex II (LHCII) as a function of photon density, Ip, of monochromatic 645-nm laser pulses (duration: approximately 2.5 ns). Special efforts were made in constructing an optical set-up that allows the accurate determination of the fluorescence from an area of constant Ip, phi F(Ip) starts to decline at approximately 10(14) and drops to values below 0.01% at maximum Ip (approximately 10(19) photons cm-2 pulse-1). T(Ip) decreases only slightly at photon densities of approximately 10(15) but increases steeply at values of > 10(17) photons cm-2 pulse-1. The interpretation of the phi F(Ip) data using the saturation limit of Mauzerall's multiple hit model leads to a unit size of about 10-15 chlorophyll molecules. One interpretation is to attribute this result to a very fast exciton-exciton annihilation of multiple excited states generated within this small domain. Alternatively, based on the assumption that delocalized cluster states within the monomeric/trimeric subunit of LHCII exist, the results can be consistently described by a kinetic model comprising ground, monoexcitonic, and biexcitonic states of clusters and a triplet state that is quenched by carotenoids in LHCII. Within the framework of this model the annihilation of multiple excitations is explained as ultrafast radiationless relaxation of higher excited cluster states. Comparative measurements in diluted acetonic Chl a solution are consistently described by the depletion of the ground state, taking the absorption cross section at the used wavelength. 相似文献
50.