全文获取类型
收费全文 | 3955篇 |
免费 | 296篇 |
国内免费 | 211篇 |
专业分类
4462篇 |
出版年
2023年 | 25篇 |
2022年 | 55篇 |
2021年 | 112篇 |
2020年 | 108篇 |
2019年 | 134篇 |
2018年 | 184篇 |
2017年 | 174篇 |
2016年 | 207篇 |
2015年 | 156篇 |
2014年 | 213篇 |
2013年 | 242篇 |
2012年 | 227篇 |
2011年 | 231篇 |
2010年 | 221篇 |
2009年 | 192篇 |
2008年 | 204篇 |
2007年 | 189篇 |
2006年 | 160篇 |
2005年 | 154篇 |
2004年 | 158篇 |
2003年 | 175篇 |
2002年 | 160篇 |
2001年 | 141篇 |
2000年 | 99篇 |
1999年 | 47篇 |
1998年 | 29篇 |
1997年 | 46篇 |
1996年 | 19篇 |
1995年 | 29篇 |
1994年 | 18篇 |
1993年 | 16篇 |
1992年 | 22篇 |
1991年 | 16篇 |
1990年 | 27篇 |
1989年 | 22篇 |
1988年 | 13篇 |
1987年 | 10篇 |
1985年 | 17篇 |
1984年 | 20篇 |
1983年 | 15篇 |
1982年 | 13篇 |
1980年 | 12篇 |
1979年 | 12篇 |
1978年 | 17篇 |
1977年 | 14篇 |
1976年 | 10篇 |
1975年 | 13篇 |
1974年 | 16篇 |
1973年 | 12篇 |
1970年 | 10篇 |
排序方式: 共有4462条查询结果,搜索用时 15 毫秒
21.
D. S. Ryabukhin A. V. Vasilyev M. Ya. Zarubin 《Russian Journal of Bioorganic Chemistry》2012,38(7):717-719
The Bjorkman lignin from the European spruce (Picea abies) was destructed in trifluoromethane-sulfonic super acid (CF3SO3H) at 0°C for 2 h. Masses of the molecules in the starting Bjorkman lignin (600?C4400 Da) and masses of products of the lignin conversion in CF3SO3H (150?C1800 Da) were determined by the Matrix-Assisted Laser Desorption Ionization mass spectrometry (MALDI mass spectrometry). 相似文献
22.
Five new species of chalcidoid wasps of the family Eurytomidae are described: four from Israel and one from Kazakhstan. Tetramesa pavliceki Zerova, sp. n. (cylindrica species group) is closely related to T. scheppugi Schlecht., but differs in the more elongate flagellar segments, longer genae, and smooth metasomal tergites. Eurytoma nevoi Zerova, sp. n. is similar to E. sabulosa Erd. and E. bicolorata Zer. (phragmiticola species group), differs from these species in the longer marginal vein, punctate propodeum, and longer flagellar segments. E. oreni Zerova, sp. n. belongs to the fumipennis species group. It is closely related to E. monticola Zer., but differs in the more convex scape, longer postmarginal vein, and yellow legs. E. simutniki Zerova, sp. n. belongs to the robusta species-group. It resembles E. heriadi Zer., but differs in the longer flagellar segments of the female and in the shorter postmarginal vein. Nikanoria mamayevi Zerova, sp. n. is similar to N. stigma Zer., but differs in the more elongate metasoma, longer flagellar segments of both sexes, and larger yellow spots on the pronotum. 相似文献
23.
A. A. Galoyan B. Ya. Gurvits L. A. Shuvalova Michael T. Davis John E. Shively Terry D. Lee 《Neurochemical research》1992,17(8):773-777
A new class of stimulators of basal activity of a number of calmodulin-dependent enzymes have been previously isolated from bovine hypothalamus. One of these stimulators, denoted as C3, has been purified to homogeneity by reverse phase HPLC and tentatively identified as thymosin 4 (1–39) by mass spectrometry and Edman microsequence analysis. The stimulating effect of C3 on rabbit skeletal muscle MLCK basal activity was compared with that of thymosin 1 and thymosin 4 (16–38). Evidence is presented that all the indicated compounds are Ca2+-independent high-affinity MLCK stimulators. The potency of the stimulators in activating the enzyme was: C3>4>(CaM+Ca2+>1.This revised version was published online in June 2005 with corrections to the author name Gurvits. 相似文献
24.
Lijuan Chen Yi Zhang Lin Tang Danlian Huang Can Liu Ya Pang Jie Luo 《Analytical biochemistry》2010,407(2):172-179
Picloram, a herbicide widely used for broadleaf weed control, is persistent and mobile in soil and water with adverse health and environmental effects. It is important to develop a sensitive method for accurate detection of trace picloram in the environment. In this article, a type of ordered three-dimensional (3D) gold (Au) nanoclusters obtained by two-step electrodeposition using the spatial obstruction/direction of the polycarbonate membrane is reported. Bovine serum albumin (BSA)-picloram was immobilized on the 3D Au nanoclusters by self-assembly, and then competitive immunoreaction with picloram antibody and target picloram was executed. The horseradish peroxidase (HRP)-labeled secondary antibody was applied for enzyme-amplified amperometric measurement. The electrodeposited Au nanoclusters built direct electrical contact and immobilization interface with protein molecules without postmodification and positioning. Under the optimal conditions, the linear range for picloram determination was 0.001-10 μg/ml with a correlation coefficient of 0.996. The detection and quantification limits were 5.0 × 10−4 and 0.0021 μg/ml, respectively. Picloram concentrations in peach and excess sludge supernatant extracts were tested by the proposed immunosensor, which exhibited good precision, sensitivity, selectivity, and storage stability. 相似文献
25.
Olga N. Kulaeva Anastasiya B. Fedina Emiliya A. Burkhanova Natalya N. Karavaiko Marat Ya. Karpeisky Igor B. Kaplan Michael E. Taliansky Joseph G. Atabekov 《Plant molecular biology》1992,20(3):383-393
Exogenous human interferon 2 (IFN) and 2–5 oligoadenylates (2–5A) have been shown to cause at least a dual physiological effect in tobacco and wheat: (i) increased cytokinin activity and (ii) induced synthesis of numerous proteins, among which members of two groups of stress proteins have been identified, namely pathogenesis-related (PR) and heat shock (HS) proteins. These effects were observed only by low concentrations of these substances: IFN at 0.1–1 u/ml and 2–5A at 1–10 nM. 相似文献
26.
Fleur E van de Geijn Manfred Wuhrer Maurice HJ Selman Sten P Willemsen Ya?l A de Man André M Deelder Johanna MW Hazes Radboud JEM Dolhain 《Arthritis research & therapy》2009,11(6):R193
Introduction
Improvement of rheumatoid arthritis (RA) during pregnancy has been causatively associated with increased galactosylation of immunoglobulin G (IgG) N-glycans. Since previous studies were small, did not include the postpartum flare and did not study sialylation, these issues were addressed in the present study. 相似文献27.
Chiakang Ho Ya Gao Danning Zheng Yanjun Liu Shengzhou Shan Bin Fang Yixuan Zhao Dingzhong Song Yifan Zhang Qingfeng Li 《Journal of cellular and molecular medicine》2019,23(8):5108-5118
Obesity and its associated metabolic disorders such as diabetes, hepatic steatosis and chronic heart diseases are affecting billions of individuals. However there is no satisfactory drug to treat such diseases. In this study, we found that alisol A, a major active triterpene isolated from the Chinese traditional medicine Rhizoma Alismatis, could significantly attenuate high‐fat‐diet‐induced obesity. Our biochemical detection demonstrated that alisol A remarkably decreased lipid levels, alleviated glucose metabolism disorders and insulin resistance in high‐fat‐diet‐induced obese mice. We also found that alisol A reduced hepatic steatosis and improved liver function in the obese mice model.In addition, protein expression investigation revealed that alisol A had an active effect on AMPK/ACC/SREBP‐1c pathway. As suggested by the molecular docking study, such bioactivity of alisol A may result from its selective binding to the catalytic region of AMPK.Therefore, we believe that Alisol A could serve as a promising agent for treatment of obesity and its related metabolic diseases. 相似文献
28.
Estimation of root water uptake in crops is important for making many other agricultural predictions. This estimation often
involves two assumptions: (1) that a critical soil water potential exists which is constant for a given combination of soil
and crop and which does not depend on root length density, and (2) that the local root water uptake at given soil water potential
is proportional to root length density.
Recent results of both mathematical modeling and computer tomography show that these assumptions may not be valid when the
soil water potential is averaged over a volume of soil containing roots. We tested these assumptions for plants with distinctly
different root systems. Root water uptake rates and the critical soil water potential values were determined in several adjacent
soil layers for horse bean (Vicia faba) and oat (Avena sativa) grown in lysimeters, and for field-grown cotton (Gossypium L.), maize (Zea mays) and alfalfa (Medicago sativa L.) crops. Root water uptake was calculated from the water balance of each layer in lysimeters. Water uptake rate was proportional
to root length density at high soil water potentials, for both horse bean and oat plants, but root water uptake did not depend
on root density for horse bean at potentials lower than −25 kPa. We observed a linear dependency of a critical soil water
potential on the logarithm of root length density for all plants studied. Soil texture modified the critical water potential
values, but not the linearity of the relationship. B E Clothier Section editor 相似文献
29.
Ya. N. Shoikhet V. I. Kiselev E. V. Zaitsev I. B. Kolyado B. Yu. Konovalov S. Bauer B. Grosche W. Burkart 《Radiation and environmental biophysics》1999,38(3):207-210
A registry of the rural population in the Altai region exposed to fallout from nuclear tests at the Semipalatinsk test site
(STS) was established more than four decades after the first Soviet nuclear explosion on August 29, 1949. Information about
individuals living in an exposed and a control area was collected using all available local sources, such as kolkhoz documentation, school registries, medical treatment records and interviews with residents. As a result, a database comprising
an exposed group of 39 179 individuals from 53 Altai region villages, 6769 external and 3303 internal controls was compiled.
For several settlements, effective dose estimates reached the level of 1.5 Sv, while the average effective dose estimate in
the exposed group was 340 mSv. Dosimetric data, vital status information and health records gathered at rayon and village
medical facilities are held in the registry. Cause-of-death information for deceased residents is obtained from death registration
forms archived at the Altai region vital statistics office. At present, a follow-up of approximately 40% of the population
exposed in 1949 has been done. More will be added by searching for migrants to the larger towns of the Altai region, i.e.
Barnaul, Rubtsovsk and Biisk. In order to assess the influence of radiation exposure, analytical studies with a case-control
design for stomach and lung cancer are currently being prepared. The number of known cases is sufficient to detect an odds
ratio of 1.5 at the 95% confidence level. Epidemiological studies in populations affected by fallout from STS may be equally
important to the atomic bomb survivors’ study for the direct quantification of radiation effects. The range of exposure rates
experienced will extend the acute high-dose-rate findings from Hiroshima/Nagasaki towards acute and protracted lower exposures,
which are more relevant for radiation protection issues.
Received: 3 March 1999 / Accepted in revised form: 8 June 1999 相似文献