全文获取类型
收费全文 | 394805篇 |
免费 | 45465篇 |
国内免费 | 360篇 |
专业分类
440630篇 |
出版年
2016年 | 3573篇 |
2015年 | 5354篇 |
2014年 | 6246篇 |
2013年 | 8965篇 |
2012年 | 9950篇 |
2011年 | 10021篇 |
2010年 | 6669篇 |
2009年 | 6297篇 |
2008年 | 8912篇 |
2007年 | 9397篇 |
2006年 | 8933篇 |
2005年 | 8702篇 |
2004年 | 8623篇 |
2003年 | 8218篇 |
2002年 | 8218篇 |
2001年 | 18207篇 |
2000年 | 18760篇 |
1999年 | 14899篇 |
1998年 | 4910篇 |
1997年 | 5162篇 |
1996年 | 4815篇 |
1995年 | 4617篇 |
1994年 | 4553篇 |
1993年 | 4554篇 |
1992年 | 12062篇 |
1991年 | 11652篇 |
1990年 | 11309篇 |
1989年 | 10959篇 |
1988年 | 10344篇 |
1987年 | 9870篇 |
1986年 | 9375篇 |
1985年 | 9461篇 |
1984年 | 7814篇 |
1983年 | 6724篇 |
1982年 | 5353篇 |
1981年 | 4986篇 |
1980年 | 4522篇 |
1979年 | 7629篇 |
1978年 | 6156篇 |
1977年 | 5657篇 |
1976年 | 5342篇 |
1975年 | 6003篇 |
1974年 | 6636篇 |
1973年 | 6570篇 |
1972年 | 6093篇 |
1971年 | 5511篇 |
1970年 | 4759篇 |
1969年 | 4721篇 |
1968年 | 4305篇 |
1967年 | 3620篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
331.
332.
J. Dierschke T. Krüger F. Hüttmann F. Bairlein Kerstin Müller G. Scheiffarth H. -W. Helb W. Irsch W. Lantermann B. Haubitz W. Winkel und J. Haffer 《Journal of Ornithology》2003,144(4):484-498
Ohne Zusammenfassung 相似文献
333.
Conventional amperometric alcohol electrodes were constructed with oxygen- and hydrogen peroxide-base sensors and a much improved electrode was designed by placing a hydrophobic, gas-permeable membrane over the conventional hydrogen peroxide-based alcohol electrode. The immobilization of alcohol oxidase with glutaraldehyde was also studied and optimized. The upper linear ranges of the conventional and newly designed alcohol electrodes were 0.02 and 0.5% ethanol, respectively. The hydrophobic membrane of the new design eliminated the classical electrochemical interferences of hydrogen peroxide-based electrodes and the typical pH dependence of enzymatic systems. 相似文献
334.
Feasible mechanisms for algal digestion in the king angelfish 总被引:1,自引:0,他引:1
To determine the ability of the king angelfish Holacanthus passer to digest algae, three algal species were immersed in acidic conditions similar to that found in the stomach of fish. Only one of them was not susceptible to acidic lysis; two were affected after 40 and 60 min at pH 2·0. King angelfish have an expanded region of the intestine called here the hindgut chamber (HC) containing populations of micro-organisms. Some of these micro-organisms have the capacity to grow in cellulose, agar, and alginic acid; the main components of algal cell walls. Micro-organisms grew in carboxymethylcellulose cultures under aerobic and micro-aerobic conditions. The HC is highly vascularized, which could increase absorptive efficiency of material digested in it. 相似文献
335.
One novel approach for the biological delivery of peptide drugs is to incorporate the sequence of the peptide into the structure of a natural transport protein such as human serum transferrin (HST). However, a potential drawback is that the HST may increase the immunoreactivity of the peptide, in the same way that carrier proteins can be used to generate highly immunogenic peptide hapten conjugates. In this study we have generated a recombinant HST carrier protein that contains a peptide substrate of HIV-1 protease (VSQNYPIVL). The protein retained native HST function, and the peptide was surface exposed since it was immunoreactive in native dot blots, and was cleaved by HIV-1 protease. Immunisation of rabbits with the recombinant protein elicited only a very poor anti-peptide immune response. In contrast, strong anti-peptide immune responses were raised against both the peptide alone, and a chemical conjugate of the peptide with HST. These data demonstrate that it is possible to attenuate the immune response normally directed against an immunogenic peptide sequence by engineering into a surface exposed loop of HST. These findings may have an important impact on the future design of peptide delivery systems. 相似文献
336.
337.
R. H. L. DISNEY 《Systematic Entomology》1986,11(4):413-422
ABSTRACT. Diplonevra mortimeri sp.nov. and D.watsoni. sp.nov. are described from specimens caught at Nasutitermitinae termite colonies in Sulawesi. The female of both species has a remarkable pre-oviposition behaviour in which she lures a worker termite into following her away from the colony. She then oviposits in the termite's abdomen. Pupation takes place within the remains of the host's abdomen. Both species only mature a single egg at a time. The female probably guards the comatose host termite during the period of larval development. The morphology of the male hypopygia of the new species allows reinterpretation of the peculiar anal tube in typical male Diplonevra. Furthermore the suggested homologies reinforce the view that the epandrium (tergite 9) has not been replaced by a periandrium (fused gonocoxites) in the Cyclorrhapha and consequently the latter cannot be derived from the Empidoidea. 相似文献
338.
Viscoelasticity of packed erythrocyte suspensions subjected to low amplitude oscillatory deformation. 下载免费PDF全文
Concentrated adult erythrocyte suspensions were subjected to low amplitude oscillatory shear in a Weissenberg rheogoniometer equipped with a cone-and-plate assembly. The dynamic viscoelastic properties of the suspension were measured over a broad range of frequency by a numerical solution that accounted for fluid inertia. Variation of shear amplitude and cell volume percent, and comparison of buffered saline, plasma, and dextran as suspending media showed that the cellular elements had undergone small bending and shearing deformations. Studies of normal adult erythrocytes, hypotonically swollen cells, temperature-altered cells, and erythrocyte ghosts suggested that the method was evaluating membrane material properties. The normal membrane was found to exhibit a shear rate dependent elastic modulus that increased by more than a factor of 20 over a frequency range from 0.0076 Hz to 60 Hz. The membrane viscosity showed a substantial drop with frequency indicative of a frequency thinning phenomenon. At high frequency of deformation the viscous response of normal erythrocytes was no longer indicative of a membrane property due to the dominant influence of the internal hemoglobin solution. The studies generally supported the ability of the method to quantify relative membrane material properties and detect changes in membrane structure. 相似文献
339.
G Ponsin A M Gotto G Utermann H J Pownall 《Biochemical and biophysical research communications》1985,133(3):856-862
Several isoforms of apoprotein A-I [apoA-I], the major apoprotein of high density lipoproteins [HDL], have been described. We compared the in vivo and in vitro properties of normal human apoA-I with those of apoA-I [Lys107----0]. Fluorescence and circular dichroic spectra showed that deletion of Lys107 decreases apoprotein self-association. In vivo metabolic studies in the rat indicated that the interaction of apoA-I [Lys107----0] with HDL was lower than normal. We conclude that deletion of Lys107 results in a reorganization of the apoprotein structure that decreases its potential to form hydrophobic associations. 相似文献
340.
J H Brock 《BMJ (Clinical research ed.)》1986,293(6546):518-520