全文获取类型
收费全文 | 9430篇 |
免费 | 632篇 |
国内免费 | 6篇 |
出版年
2023年 | 99篇 |
2022年 | 199篇 |
2021年 | 325篇 |
2020年 | 260篇 |
2019年 | 300篇 |
2018年 | 419篇 |
2017年 | 346篇 |
2016年 | 472篇 |
2015年 | 526篇 |
2014年 | 599篇 |
2013年 | 697篇 |
2012年 | 725篇 |
2011年 | 706篇 |
2010年 | 438篇 |
2009年 | 374篇 |
2008年 | 378篇 |
2007年 | 382篇 |
2006年 | 350篇 |
2005年 | 288篇 |
2004年 | 263篇 |
2003年 | 222篇 |
2002年 | 201篇 |
2001年 | 125篇 |
2000年 | 123篇 |
1999年 | 93篇 |
1998年 | 56篇 |
1997年 | 45篇 |
1996年 | 60篇 |
1995年 | 56篇 |
1994年 | 56篇 |
1993年 | 37篇 |
1992年 | 64篇 |
1991年 | 57篇 |
1990年 | 32篇 |
1989年 | 42篇 |
1988年 | 42篇 |
1987年 | 53篇 |
1986年 | 45篇 |
1985年 | 33篇 |
1984年 | 34篇 |
1983年 | 34篇 |
1982年 | 28篇 |
1981年 | 27篇 |
1980年 | 23篇 |
1979年 | 25篇 |
1978年 | 30篇 |
1976年 | 22篇 |
1975年 | 22篇 |
1973年 | 22篇 |
1972年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
J. Bubeník J. Ježek M. Zaoral J. Hofmann Y. V. Gruntenko J. G. Osipov A. G. Zolotareva T. E. Vakhrusheva V. G. Budker 《Cancer immunology, immunotherapy : CII》1984,18(2):123-125
Summary Treatment with synthetic MDP inhibited growth of transplantable, chemically induced tumors in syngeneic mice. The tumor-inhibitory effect was dependent on the schedule of MDP administration.Growth of SC transplants of a nonmetastasizing, MC-induced fibrosarcoma, MC11, was inhibited by local treatment with 200 g and 1,000 g MDP given SC 5–7 weeks before challenge. Treatment with lower (10 g and 100 g) doses of MDP and shorter (1–4 weeks) time intervals was not effective. Single doses of MDP (10–1,000 g) 1–3 weeks after challenge had no effect.Growth of IV-inoculated, metastasizing AAT-induced hepatoma A was inhibited by IV injections of 20 g MDP given 1 and 2 days prior to the challenge. Significant increases in the survival of hepatoma-bearing mice were observed only after injections of MDP incorporated in multilamellar liposomes.Abbreviations MDP
n-acetylmuramyl-l-alanyl-d-isoglutamine
- B10
C57BL/10ScSnPh mice
- MC
3-methylcholanthrene
- ATT
o-amino-azotoluene
- PBS
phosphate-buffered saline 相似文献
122.
123.
A. van Rotterdam F. H. Lopes da Silva J. van den Ende M. A. Viergever A. J. Hermans 《Bulletin of mathematical biology》1982,44(2):283-305
A linear spatially distributed model of a chain of neurons and interneurons was investigated in relation to the generation
of propagated alpha rhythmic activity. It was assumed that the elements of the chain were interconnected by means of recurrent
collaterals and inhibitory fibres in such a way that the connectivity functions were assumed to be homogeneous and their strength
was an exponentially decreasing function of distance. It was found that such a neuronal chain shows propagation properties
for frequencies in the alpha band. The results obtained with the model are in agreement with the phase velocities encountered
experimentally. In this way, it was possible to estimate the length of the neural fibres responsible for the phenomenon of
propagated activity. The estimates obtained are in good agreement with recent quantitative neuroanatomical data on the circuitry
of the neocortex. 相似文献
124.
Summary Growth and glucose isomerase biosynthesis in Streptomyces bambergiensis ATCC 13879 have been studied under different conditions. Some data concerning correlation between cultivation conditions and elemental analysis of the cells are also presented. 相似文献
125.
Summary Using straw columns colonized by the lignocellulytic fungus Pleurotus cornucopiae, translocation of 109Cd and 203Hg in the substrate-mycelium complex and via the substrate-mycelium complex into the fruiting bodies was studied. The translocation patterns generated were metal specific and were influenced by the temperature and the physiological conditions of the mycelium (growing mycelium, established mycelium, reproductive stage).Under all conditions, generally more mercury than cadmium was translocated. In growing mycelia, for instance, an average of about seven times more mercury than cadmium was translocated. Translocation was greatly enhanced, when fruiting bodies were present. Up to 7% and 20% (average: 3.5% and 12%) of the applied cadmium and mercury, respectively, were found in the fruiting bodies. In old columns bearing fruiting bodies (colonized for more than 50 days by the fungus) considerably more heavy metal (up to 45% of the applied radioactivity) was released from the point of application than in younger columns.With one exception, no substantial differences in the translocation patterns of the label in relation to the direction of mycelial growth could be detected. 相似文献
126.
Low angle X-ray diffraction patterns were recorded from crab leg muscle in living resting state and in rigor (glycerol-extracted). Both resting and rigor patterns showed a series of layer-lines arising from a helical arrangement of actin subunits in the thin filaments. In the resting state, the crossover repeat of the long-pitch actin helices was 36.6 nm, and the symmetry of the genetic actin helix was an intermediate between and . When the muscle went into rigor, the crossover repeat changed to 38.3 nm and the helical symmetry to .In the living resting pattern, six other reflections were observed on the meridian and in the near-meridional region. These were indexed as orders of 2 × 38.2 nm and could be assigned to troponin molecules; the spacings and the intensity distributions of these reflections could be explained by the model proposed by Ohtsuki (1974) for the arrangement of troponin molecules in the thin filaments.The muscle in rigor gave meridional and near-meridional reflections at orders of 2 × 38.3 nm. These were identified as the same series of reflections as was assigned to troponin in the living resting pattern, but were more intense and could be seen up to higher orders. We consider that the myosin heads attached to the thin filament at regular intervals along its axis also contribute to these reflections in the rigor pattern. 相似文献
127.
The uptake of bloodstream forms of Trypanosoma cruzi, Y and CL stocks, by mouse peritoneal macrophages and their intracellular differentiation and multiplication has been compared in vitro. After 48 h the number of macrophages showing intracellular amastigote forms was higher when the Y stock was used. The number of parasitized cells increased with the time of contact between parasites and macrophages. Prior treatment of the parasites with anti-T. cruzi antibodies and/or complement increased the number of infected macrophages, but did not interfere with their subsequent differentiation within the macrophages. The number of parasitized cells was greater when macrophages were obtained from mice previously treated with lipopolysaccharide, peptone or thioglycollate. Uptake was not appreciably affected when macrophages were pre-treated with trypsin or anti-macrophage serum, or when the parasites and macrophages were incubated in the presence of cytochalasin B. In the same experimental conditions, epimastigotes of T. cruzi when not able to differentiate into amastigotes. Their uptake was potentiated by previous treatment with specific antibodies and/or complement and was blocked by cytochalasin B. These results confirm that epimastigotes derived from T. cruzi cultures are phagocytosed and suggest that bloodstream forms penetrate actively into macrophages. 相似文献
128.
Summary Linear measurement of blocks of constitutive heterochromatin and the euchromatin portion 1q-h in three members of a family was used to study the dependence of the size of C blocks on the degree of chromosomal contraction. The results demonstrate that the size of heterochromatin portions decrease regularly with an increases of the degree of euchromatin contraction. The dependence was found to be linear, except for mitoses with an extremely high or low degree of contraction. The finding was used for the development of a new method of evaluation of constitutive heterochromatin. 相似文献
129.
Adaptation of malate dehydrogenase to environmental temperature variability in two populations of Potentilla glandulosa Lindl. 总被引:1,自引:1,他引:0
Summary The responses of the kinetic properties of malate dehydrogenase to environmental temperature variability were compared for two populations of Potentilla glandulosa (Rosaceae). The two populations are native to regions of contrasting climates, with the inland population experiencing a high level of temperature variability during growth and the coastal populaton a low level of temperature variability. The substrate binding ability, as measured by apparent K
m
of both populations was relatively insensitive to assay temperature (Q
10<2.0) over the range of temperatures likely to be encountered during growth. The breadth of this thermal optimum was different for the two populations with the K
m
of the inland plants exhibiting relative temperature insensitivity over a much wider range of temperatures than the K
m
of the coastal plants. There was no difference between the two populations in the thermal stability of MDH activity. 相似文献
130.