全文获取类型
收费全文 | 40767篇 |
免费 | 3441篇 |
国内免费 | 2320篇 |
出版年
2023年 | 417篇 |
2022年 | 456篇 |
2021年 | 1817篇 |
2020年 | 1221篇 |
2019年 | 1505篇 |
2018年 | 1409篇 |
2017年 | 1084篇 |
2016年 | 1624篇 |
2015年 | 2427篇 |
2014年 | 2848篇 |
2013年 | 3089篇 |
2012年 | 3586篇 |
2011年 | 3398篇 |
2010年 | 1943篇 |
2009年 | 1794篇 |
2008年 | 2086篇 |
2007年 | 1867篇 |
2006年 | 1604篇 |
2005年 | 1420篇 |
2004年 | 1199篇 |
2003年 | 1053篇 |
2002年 | 905篇 |
2001年 | 851篇 |
2000年 | 736篇 |
1999年 | 710篇 |
1998年 | 416篇 |
1997年 | 452篇 |
1996年 | 429篇 |
1995年 | 389篇 |
1994年 | 378篇 |
1993年 | 308篇 |
1992年 | 441篇 |
1991年 | 383篇 |
1990年 | 331篇 |
1989年 | 246篇 |
1988年 | 236篇 |
1987年 | 198篇 |
1986年 | 141篇 |
1985年 | 185篇 |
1984年 | 121篇 |
1983年 | 104篇 |
1982年 | 80篇 |
1981年 | 60篇 |
1980年 | 55篇 |
1979年 | 72篇 |
1978年 | 66篇 |
1977年 | 46篇 |
1976年 | 48篇 |
1975年 | 40篇 |
1973年 | 48篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
In this study, replacement of dominant populations (Phragmites australis and Phalaris arundinacea) in the plant community succession process in the Zhenjiang Waterfront Wetland was approached from three aspects: growth,
photosynthesis, and specific competitive characteristics. The productivity of Phragmites, based on intrinsic rate of increase and environmental carrying capacity of the several chosen growth indices (plant length,
sheath height, and biomass), was significantly higher than that of Phalaris. Phragmites had a higher photosynthetic rate than Phalaris. However, Phalaris had a markedly lower light compensation point, which suggested that it was capable of better utilization of weak light. This
possibly might account for its survival beneath Phragmites. At three different coverage gradients, the relative yield total was greater than 1, indicating a certain degree of complementary
resource utilization via niche separation between both species. Significant differences in the competition ratio of both species
indicated a superiority of Phragmites over Phalaris in terms of competitive capability. Thus, the Phragmites population tended to exclude the Phalaris population and became the mono-dominant population in the community succession process. For Phalaris, traits such as its better utilization of weak light, its complementary resource utilization, and a partial separation of
growth period compared to Phragmites prevented complete replacement of its population to some degree. In this particular study area in the Zhenjiang Waterfront
Wetland, the hydrological conditions of the river beach determined by its elevation possibly acted as the dominant regulator
of the plant succession process. 相似文献
52.
Mischa R. Müller Kenneth Saunders Christopher Grace Macy Jin Nicole Piche-Nicholas John Steven Ronan O’Dwyer Leeying Wu Lam Khetemenee Yulia Vugmeyster Timothy P. Hickling Lioudmila Tchistiakova Stephane Olland Davinder Gill Allan Jensen Caroline J. Barelle 《MABS-AUSTIN》2012,4(6):673-685
Advances in recombinant antibody technology and protein engineering have provided the opportunity to reduce antibodies to their smallest binding domain components and have concomitantly driven the requirement for devising strategies to increase serum half-life to optimise drug exposure, thereby increasing therapeutic efficacy. In this study, we adopted an immunization route to raise picomolar affinity shark immunoglobulin new antigen receptors (IgNARs) to target human serum albumin (HSA). From our model shark species, Squalus acanthias, a phage display library encompassing the variable binding domain of IgNAR (VNAR) was constructed, screened against target, and positive clones were characterized for affinity and specificity. N-terminal and C-terminal molecular fusions of our lead hit in complex with a naïve VNAR domain were expressed, purified and exhibited the retention of high affinity binding to HSA, but also cross-selectivity to mouse, rat and monkey serum albumin both in vitro and in vivo. Furthermore, the naïve VNAR had enhanced pharmacokinetic (PK) characteristics in both N- and C-terminal orientations and when tested as a three domain construct with naïve VNAR flanking the HSA binding domain at both the N and C termini. Molecules derived from this platform technology also demonstrated the potential for clinical utility by being available via the subcutaneous route of delivery. This study thus demonstrates the first in vivo functional efficacy of a VNAR binding domain with the ability to enhance PK properties and support delivery of multifunctional therapies. 相似文献
53.
Liu Xia Ruan Zhi Shao Xing-cheng Feng Hong-xuan Wu Lei Wang Wei Wang Hong-min Mu Hong-yan Zhang Ru-jun Zhao Wei-min Zhang Hai-yan Zhang Nai-xia 《Neurochemical research》2021,46(3):699-700
Neurochemical Research - In the original version of this article, unfortunately the Fig. 3C and 3F were published with incorrect version. The correct version of the Fig. 3C and 3F... 相似文献
54.
55.
Yun Guo Yuejun He Pan Wu Bangli Wu Yan Lin Minhong He Xu Han Tingting Xia Kaiping Shen Liling Kang Qiyu Tan Wenda Ren Yan Sun Qing Li 《Journal of Plant Ecology》2022,15(2):399
AM 真菌和枯落物互作下两种喀斯特植物种间竞争较种内竞争更能促进植物养分利用
枯落物是植物养分获取和土壤养分转化的关键载体。丛枝菌根(Arbuscular mycorrhizae, AM)对植物养分摄取的影响已被广泛认知。然而,在养分亏缺的喀斯特生境中,不同竞争方式的植物如何通过AM真菌和枯落物利用养分尚不清楚。本研究对两种喀斯特适生植物构树(Broussonetia papyrifera)和云贵鹅耳枥(Carpinus pubescens)进行种内竞争和种 间竞争种植处理,并通过幼套球 囊霉(Glomus etunicatum)接种或不接种处理,以及土壤中添加或不添加两物种叶片混合枯落物处理,测定了植物生物量以及氮、磷、钾浓度等指标,研究植物的生长和养分利用。研究结果表明,AM真菌对两种植物养分摄取影响不同,AM真菌显著提高了种内和种间竞争下构树的养分摄取量,但降低了云贵鹅耳枥的养分摄取量。种间竞争下接种AM真菌,枯落物添加促进了云贵鹅耳枥对氮的摄取,抑制了构树对氮的摄取。接种AM真菌和添加枯落物条件下,种间竞争的构树对氮、磷和钾的摄取量及云贵鹅耳枥对氮的摄取量均高于种内竞争;种间竞争下两物种养分竞争力呈现明显差异,即构树对磷和钾养分竞争力显著提高,对氮则不显著;云贵鹅耳枥仅对钾的养分竞争力显著降低,对氮和磷则无显著影响。这些结果说明,在AM真菌与枯落物相互作用下,两种喀斯特植物种间竞争较种内竞争更能促进植物养分利用。 相似文献
56.
57.
58.
59.
60.
Spliceosome-targeted therapies trigger an antiviral immune response in triple-negative breast cancer
Elizabeth A. Bowling Jarey H. Wang Fade Gong William Wu Nicholas J. Neill Ik Sun Kim Siddhartha Tyagi Mayra Orellana Sarah J. Kurley Rocio Dominguez-Vidaña Hsiang-Ching Chung Tiffany Y.-T. Hsu Julien Dubrulle Alexander B. Saltzman Heyuan Li Jitendra K. Meena Gino M. Canlas Srinivas Chamakuri Thomas F. Westbrook 《Cell》2021,184(2):384-403.e21