全文获取类型
收费全文 | 244828篇 |
免费 | 22486篇 |
国内免费 | 254篇 |
专业分类
267568篇 |
出版年
2018年 | 2635篇 |
2017年 | 2578篇 |
2016年 | 3426篇 |
2015年 | 3659篇 |
2014年 | 4576篇 |
2013年 | 6550篇 |
2012年 | 7204篇 |
2011年 | 7899篇 |
2010年 | 5381篇 |
2009年 | 4787篇 |
2008年 | 6868篇 |
2007年 | 7081篇 |
2006年 | 6713篇 |
2005年 | 6410篇 |
2004年 | 6314篇 |
2003年 | 6150篇 |
2002年 | 6008篇 |
2001年 | 12005篇 |
2000年 | 11961篇 |
1999年 | 9143篇 |
1998年 | 2669篇 |
1997年 | 2743篇 |
1996年 | 2692篇 |
1995年 | 2476篇 |
1994年 | 2423篇 |
1993年 | 2316篇 |
1992年 | 7174篇 |
1991年 | 6978篇 |
1990年 | 7056篇 |
1989年 | 6841篇 |
1988年 | 6355篇 |
1987年 | 6009篇 |
1986年 | 5353篇 |
1985年 | 5661篇 |
1984年 | 4462篇 |
1983年 | 3861篇 |
1982年 | 2669篇 |
1981年 | 2493篇 |
1980年 | 2303篇 |
1979年 | 4107篇 |
1978年 | 3134篇 |
1977年 | 2881篇 |
1976年 | 2826篇 |
1975年 | 3268篇 |
1974年 | 3496篇 |
1973年 | 3524篇 |
1972年 | 3058篇 |
1971年 | 2842篇 |
1970年 | 2530篇 |
1969年 | 2299篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
331.
F. Marsolat D. Tromson N. Tranchant P. Bergonzo F. Moignau L. De Carlan D. Lazaro M. Agelou C. Bassinet C. Huet S. Derreumaux M. Chea G. Boisserie I. Buchheit V. Marchesi 《Physica medica : PM : an international journal devoted to the applications of physics to medicine and biology : official journal of the Italian Association of Biomedical Physics (AIFB)》2012
332.
333.
The effects of Heterosigma akashiwo on juvenile Oncorhynchus tshawytscha and its implications for fish culture 总被引:2,自引:0,他引:2
E. A. Black J.N. C. Whyth J. W. Bagshaw N. G. Ginther 《Zeitschrift fur angewandte Ichthyologie》1991,7(3):168-175
The effects of natural blooms of Heterosigma akashiwo on freshwater-and saltwater-acclimated juvenile chinook salmon were assessed. Rates of fish mortality in the blooms were independent of acclimation of fish to seawater and the ambient oxygen levels, but were dependent on concentration of algae and ambient water temperatures. No pathological abnormality to gills or other internal organs in the fish were evident. Aeration or oxygenation of fish cages did not enhance or inhibit fish survival in a H. akashiwo bloom. Cause of death was considered to be due to a labile ichthyotoxic agent. 相似文献
334.
N D Hopwood 《BioEssays : news and reviews in molecular, cellular and developmental biology》1990,12(10):465-471
Mesodermal cell differentiation begins in response to an inductive interaction early in frog development. In parallel with the recent finding that certain peptide growth factors can induce mesoderm, early cellular and genetic responses to the induction have been discovered. I review here recent work on these responses, work that aims to understand how cells respond to inducers to form the complex pattern of the vertebrate mesoderm. 相似文献
335.
Cefepime/amikacin in the empirical antibacterial therapy for patients with hemoblastosis of different forms] 总被引:1,自引:0,他引:1
The results of the use of cefepime (Maxipime) combination with amikacin vs ceftriaxon combination with amikacin in the treatment of 80 patients with different forms of hemoblastosis are presented. Severe infectious complications in the patients were associated with prolonged and deep neutropenia during inductive or antirelapsing chemotherapy. All the patients in the trial were from the group of high risk of infectious complications with the blood neutrophil count under 100 cells/microliter. The duration of neutropenia averaged 12 days (7 to 15). The average period of the treatment with cefepime and amikacin equaled to 13 days (8 to 16). The treatment with cefepime + amikacin was successful in 38 out of 40 patients (95%). The average period of the treatment with ceftriaxon and amikacin equaled to 14 days (7 to 18). The efficacy of the treatment with ceftriaxon + amikacin was 60% (24 patients out of 40). 相似文献
336.
The status of the reproductive system is investigated in five species of Teleostei from the Teterev River and the Kiev Reservoir
(Ukraine), descendants of F42–F7 generations of fish exposed to radiation from the accident at the Chernobyl nuclear power plant. Twenty years after the accident,
a wide range of morphofuinctional anomalies of this system is present in fish. The most significant of them are: asymmetry
and anomalous morphology of gonads, proliferation of connective tissue—sterilization, mass destruction of follicular and sex
cells of various developmental stages, and hermaphroditism. Among the investigated species, disturbances of reproductive glands
were preset to the highest extent in pike Esox lucius and crucian carp Carassius carassius. In the series of investigated generations the maximum frequency of occurrence of gonad anomalies was noted in F4 and F5, due to prolonged mutagenesis (Dubinin, 1986). 相似文献
337.
A method using liquid chromatography - atmospheric pressure chemical ionisation mass spectrometry was evaluated for determining the molecular species composition of phospholipids (phosphatidylcholines from soybean, egg yolk and bovine liver) after conversion to diacylglycerol nicotinate derivatives. The structures could be deduced from pseudo-molecular ions ([MH-123](+)) and three pairs of monoacyl containing fragment ions. All molecular species in mixed peaks were readily identified and many minor components, earlier not encountered in the samples under investigation, were identified. Acyl chain regioisomers were readily distinguished by the ratio of the [MH-RCHCO](+) ions. Molecular species differing only in the position of the double bonds in one polyunsaturated acyl chain were separated on the basis of retention times. A half quantitative estimation of the molecular species composition of complex samples was achieved by a combination of UV detection and, for mixed peaks, the areas of [MH-123](+) ions. 相似文献
338.
The Ca2+-stimulated, Mg2+-dependent ATPase from rat liver plasma membranes was solubilized using the detergent polyoxyethylene 9 lauryl ether and purified by column chromatography using Polybuffer Exchanger 94, concanavalin A-Sepharose 4B, and Sephadex G-200. The molecular weight of the enzyme, estimated by gel filtration in the presence of the detergent on a Sephadex G-200 column, was 200,000 +/- 15,000. The enzyme was purified at least 300-fold from rat liver plasma membranes and had a specific activity of 19.7 mumol/mg/min. Polyacrylamide gel electrophoresis under nondenaturing conditions of the purified enzyme indicated that the enzymatic activity correlated with the major protein band. In sodium dodecyl sulfate-polyacrylamide gel electrophoresis, one major band in the molecular weight range of 70,000 +/- 5,000 was seen. The isoelectric point of the purified enzyme was 6.9 +/- 0.2 as determined by analytical isoelectric focusing. The enzyme was activated by Ca2+ with an apparent half-saturation constant of 87 +/- 2 nM for Ca2+. Calmodulin and trifluoperazine at the concentration of 1 microgram/ml and 100 microM, respectively, had no effect on the enzymatic activity. 相似文献
339.
N Iu Belenkov E B Korolev M O Gromyko 《Zhurnal vysshe? nervno? deiatelnosti imeni I P Pavlova》1985,35(4):674-677
Reactivity of neurones in orbitofrontal cortex of the cat to the action of light or sound was studied in consecutive stages of alimentary behaviour conditioned by the smell and then the sight of food. Changes were found of the character of neuronal reactions to the light and sound stimuli at the change of smell to the sight of food. A conclusion is drown, that polysensory properties of the neurones of the orbitofrontal cortex provide integral organization of brain sensory function at separate stages of alimentary behaviour. 相似文献
340.