全文获取类型
收费全文 | 857篇 |
免费 | 40篇 |
国内免费 | 2篇 |
出版年
2023年 | 13篇 |
2022年 | 11篇 |
2021年 | 22篇 |
2020年 | 16篇 |
2019年 | 22篇 |
2018年 | 39篇 |
2017年 | 26篇 |
2016年 | 32篇 |
2015年 | 30篇 |
2014年 | 66篇 |
2013年 | 48篇 |
2012年 | 57篇 |
2011年 | 69篇 |
2010年 | 45篇 |
2009年 | 34篇 |
2008年 | 48篇 |
2007年 | 52篇 |
2006年 | 50篇 |
2005年 | 47篇 |
2004年 | 38篇 |
2003年 | 24篇 |
2002年 | 29篇 |
2001年 | 12篇 |
2000年 | 3篇 |
1999年 | 7篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 4篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 1篇 |
1979年 | 5篇 |
1978年 | 1篇 |
1977年 | 4篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1971年 | 1篇 |
1958年 | 1篇 |
1931年 | 1篇 |
排序方式: 共有899条查询结果,搜索用时 312 毫秒
51.
The superior performance of F1 hybrids has a significant impact on agricultural productivity. For commercial application, the availability of an efficient
system for obtaining male-sterile lines of crops is an essential prerequisite. Here we have investigated the use of RNA interference
(RNAi) technology to silence a male-specific gene in the model host tobacco. TA29 is expressed exclusively in anthers at the time of microspore development. About 10 out of 13 tobacco lines transformed with
a hairpin RNAi construct containing TA29 sequences were male sterile. Transgenic plants were phenotypically indistinguishable from non-transgenic plants. At the anthesis
stage, pollen grains from transgenic, male-sterile plants were aborted and lysed in comparison to the round and fully developed
pollen in non-transgenic plants. Microscopic analysis of anthers showed selective degradation of tapetum in transgenic plants
with no microspore development. One week after self-pollination, the ovules of non-transgenic plants were double the size
of those in transgenic plants, due to successful self-fertilization. Male sterile transgenic plants set seed normally, when
cross-pollinated with pollen from non-transgenic plants, confirming no adverse effect on the female parts of the flower. These
results show that silencing of male-specific genes by RNAi is potentially a useful tool for generating male-sterile lines
for producing hybrid seed. 相似文献
52.
Background
Molecular hydrogen is an environmentally-clean fuel and the reversible (bi-directional) hydrogenase of the cyanobacterium Synechocystis sp. PCC 6803 as well as the native Escherichia coli hydrogenase 3 hold great promise for hydrogen generation. These enzymes perform the simple reaction 2H+ + 2e- ↔ H2 (g). 相似文献53.
Farrokhzad Yusuf Babaei Alireza Yadollahi Abbas Kashkooli Arman Beyraghdar Mokhtassi-Bidgoli Ali Hesami Shahriar 《Plant Cell, Tissue and Organ Culture》2022,149(3):535-548
Plant Cell, Tissue and Organ Culture (PCTOC) - We tested the feasibility to promote growth and shoot proliferation of Phalaenopsis through different wavelengths of LED and fluorescent. Therefore,... 相似文献
54.
55.
56.
Zeynep E. Çakmak Tolga T. Ölmez Turgay Çakmak Yusuf Menemen Turgay Tekinay 《Phycological Research》2015,63(3):202-211
Nutrient stress is one of the most favorable ways of increasing neutral lipid and high value‐added output production by microalgae. However, little is known about the level of the oxidative damage caused by nutrient stress for obtaining an optimal stress level for maximum production of specific molecules. In this study, the antioxidant response of Chlamydomonas reinhardtii grown under element deprivation (nitrogen, sulfur, phosphorus and magnesium) and supplementation (nitrogen and zinc) was investigated. All element regimes caused a decrease in growth, which was most pronounced under N deprivation. Element deprivation and Zn supplementation caused significant increases in H2O2 and lipid peroxidation levels of C. reinhardtii. Decrease in total chlorophyll level was followed by an increase of total carotenoid levels in C. reinhardtii under N and S deprivation while both increased under N supplementation. Confocal imaging of live cells revealed dramatic changes of cell shape and production of neutral lipid bodies accompanied by a decrease of chlorophyll clusters. Antioxidant capacity of cells decreased under N, S and P deprivation while it increased under N and Zn supplementation. Fluctuation of antioxidant enzyme activities in C. reinhardtii grown under different element regimes refers to different metabolic sources of reactive oxygen species production triggered by a specific element absence or overabundance. 相似文献
57.
58.
Nurlisa Yusuf Ammar Zakaria Mohammad Iqbal Omar Ali Yeon Md Shakaff Maz Jamilah Masnan Latifah Munirah Kamarudin Norasmadi Abdul Rahim Nur Zawatil Isqi Zakaria Azian Azamimi Abdullah Amizah Othman Mohd Sadek Yasin 《BMC bioinformatics》2015,16(1)
Background
Effective management of patients with diabetic foot infection is a crucial concern. A delay in prescribing appropriate antimicrobial agent can lead to amputation or life threatening complications. Thus, this electronic nose (e-nose) technique will provide a diagnostic tool that will allow for rapid and accurate identification of a pathogen.Results
This study investigates the performance of e-nose technique performing direct measurement of static headspace with algorithm and data interpretations which was validated by Headspace SPME-GC-MS, to determine the causative bacteria responsible for diabetic foot infection. The study was proposed to complement the wound swabbing method for bacterial culture and to serve as a rapid screening tool for bacteria species identification. The investigation focused on both single and poly microbial subjected to different agar media cultures. A multi-class technique was applied including statistical approaches such as Support Vector Machine (SVM), K Nearest Neighbor (KNN), Linear Discriminant Analysis (LDA) as well as neural networks called Probability Neural Network (PNN). Most of classifiers successfully identified poly and single microbial species with up to 90% accuracy.Conclusions
The results obtained from this study showed that the e-nose was able to identify and differentiate between poly and single microbial species comparable to the conventional clinical technique. It also indicates that even though poly and single bacterial species in different agar solution emit different headspace volatiles, they can still be discriminated and identified using multivariate techniques. 相似文献59.
60.
Sirisansaneeyakul S Singhasuwan S Choorit W Phoopat N Garcia JL Chisti Y 《Marine biotechnology (New York, N.Y.)》2011,13(5):928-941
The microalgae Chlorella protothecoides UTEX 25, Chlorella sp. TISTR 8991, and Chlorella sp. TISTR 8990 were compared for use in the production of biomass and lipids under photoautotrophic conditions. Chlorella sp. TISTR 8990 was shown to be potentially suitable for lipid production at 30°C in a culture medium that contained only
inorganic salts. For Chlorella sp. TISTR 8990 in optimal conditions in a stirred tank photobioreactor, the lipid productivity was 2.3 mg L−1 h−1 and after 14 days the biomass contained more than 30% lipids by dry weight. To attain this, the nitrogen was provided as
KNO3 at an initial concentration of 2.05 g L−1 and chelated ferric iron was added at a concentration of 1.2 × 10−5 mol L−1 on the ninth day. Under the same conditions in culture tubes (36 mm outer diameter), the biomass productivity was 2.8-fold
greater than in the photobioreactor (0.125 m in diameter), but the lipid productivity was only 1.2-fold higher. Thus, the
average low-light level in the photobioreactor actually increased the biomass specific lipid production compared to the culture
tubes. A light-limited growth model closely agreed with the experimental profiles of biomass production, nitrogen consumption,
and lipid production in the photobioreactor. 相似文献