全文获取类型
收费全文 | 934篇 |
免费 | 54篇 |
国内免费 | 14篇 |
出版年
2021年 | 18篇 |
2020年 | 15篇 |
2019年 | 12篇 |
2018年 | 21篇 |
2017年 | 18篇 |
2016年 | 19篇 |
2015年 | 30篇 |
2014年 | 30篇 |
2013年 | 52篇 |
2012年 | 27篇 |
2011年 | 29篇 |
2010年 | 29篇 |
2009年 | 51篇 |
2008年 | 40篇 |
2007年 | 22篇 |
2006年 | 43篇 |
2005年 | 30篇 |
2004年 | 36篇 |
2003年 | 28篇 |
2002年 | 32篇 |
2001年 | 16篇 |
2000年 | 18篇 |
1999年 | 23篇 |
1998年 | 14篇 |
1997年 | 15篇 |
1996年 | 14篇 |
1995年 | 12篇 |
1994年 | 21篇 |
1993年 | 16篇 |
1992年 | 11篇 |
1991年 | 12篇 |
1990年 | 17篇 |
1989年 | 15篇 |
1988年 | 12篇 |
1987年 | 17篇 |
1986年 | 6篇 |
1985年 | 16篇 |
1984年 | 19篇 |
1983年 | 12篇 |
1982年 | 21篇 |
1981年 | 14篇 |
1980年 | 13篇 |
1979年 | 7篇 |
1978年 | 11篇 |
1977年 | 7篇 |
1976年 | 14篇 |
1974年 | 7篇 |
1973年 | 6篇 |
1972年 | 15篇 |
1970年 | 6篇 |
排序方式: 共有1002条查询结果,搜索用时 15 毫秒
151.
Fenoxycarb (FC) effects were studied on juvenile hormone (JH) titers and JH‐esterase activities in the silkworm, B. Mori. In the literature, FC was observed to induce high JH titers but also to act without corpora allata (CA). These contradictory results did not permit us to conclude whether FC was a potent JH mimic or it was acting through the enhancement of JH titers in the hemolymph. Analysis of hemolymph JH‐esterase activities during the last larval instar reveals that FC was not a JH‐esterase inhibitor. Considering JHs, only JH II was detected in the European hybrid 200×300. Furthermore, JH titer was exactly identical in control and FC‐treated larvae, i.e., it dropped during the first 2 days of the last larval instar and became undetectable after day 2. This result is important since it contradicts the generally admitted concept that FC was acting by increasing the titer of JH. On the contrary, it was found that, despite its non‐terpenoid chemical structure, FC might be a JH mimic. In addition, FC suspected contamination of mulberry leaves was analyzed from a physiological viewpoint. We observed that "contaminated" mulberry leaves‐fed larvae became permanent larvae through the inhibition of their prothoracic glands (PG) activity and without any modification of their JH titers, i.e., exactly as for FC‐treated larvae. This last point adds information concerning the suspected implication of FC in the induction of the non‐spinning syndrome. Arch. Insect Biochem. Physiol. 40:141–149, 1999. © 1999 Wiley‐Liss, Inc. 相似文献
152.
153.
Fast Sampling,Analyses and Chemometrics for Plant Breeding: Bitter Acids,Xanthohumol and Terpenes in Lupulin Glands of Hops (Humulus lupulus)
下载免费PDF全文
![点击此处可从《Phytochemical analysis : PCA》网站下载免费的PDF全文](/ch/ext_images/free.gif)
154.
Li GQ Xia HH Chen MH Tsukamoto T Tatematsu M Gu Q Qiao L Cho CH So WH Yuen MF Hu PJ Liang YJ Lin HL Chan AO Wong BC 《Helicobacter》2008,13(1):20-29
Background: Helicobacter pylori infection is a major cause of gastritis and gastric carcinoma. Aspirin has anti‐inflammatory and antineoplastic activity. The aim of the present study was to determine the effects of aspirin on H. pylori‐induced gastritis and the development of heterotopic proliferative glands. Methods: H. pylori strain SS1 was inoculated into the stomachs of Mongolian gerbils. Two weeks after inoculation, the animals were fed with the powder diets containing 0 p.p.m. (n = 10), 150 p.p.m. (n = 10), or 500 p.p.m. (n = 10) aspirin. Mongolian gerbils were killed after 36 weeks of infection. Uninfected Mongolian gerbils (n = 10) were used as controls. Histologic changes, epithelial cell proliferation and apoptosis, and prostaglandin E2 (PGE2) levels of gastric tissue were determined. Results: H. pylori infection induced gastric inflammation. Administration of aspirin did not change H. pylori‐induced gastritis, but alleviated H. pylori‐induced hyperplasia and the development of heterotopic proliferative glands. Administration of aspirin accelerated H. pylori‐associated apoptosis but decreased H. pylori‐associated cell proliferation. In addition, the increased gastric PGE2 levels due to H. pylori infection were suppressed by treatment with aspirin, especially at the dose of 500 p.p.m. Conclusions: Aspirin alleviates H. pylori‐induced hyperplasia and the development of heterotopic proliferative glands. Moreover, aspirin increases H. pylori‐induced apoptosis. We demonstrated the antineoplastic activities of aspirin in H. pylori‐related gastric carcinogenesis. 相似文献
155.
In this study, we describe an experimental system based on intravital two-photon microscopy for studying endocytosis in live animals. The rodent submandibular glands were chosen as model organs because they can be exposed easily, imaged without compromising their function and, furthermore, they are amenable to pharmacological and genetic manipulations. We show that the fibroblasts within the stroma of the glands readily internalize systemically injected molecules such as fluorescently conjugated dextran and BSA, providing a robust model to study endocytosis. We dynamically image the trafficking of these probes from the early endosomes to the late endosomes and lysosomes while also visualizing homotypic fusion events between early endosomes. Finally, we demonstrate that pharmacological agents can be delivered specifically to the submandibular salivary glands, thus providing a powerful tool to study the molecular machinery regulating endocytosis in a physiological context. 相似文献
156.
Morphological and functional characterization of the thoracic portion of blowfly salivary glands 总被引:1,自引:0,他引:1
The abdominal portion of the salivary glands in the blowfly has been studied intensively. Here, we examine the thoracic part of the salivary glands, emphasizing structural and functional aspects. The initial segment downstream of the abdominal portion is secretory and resembles the latter in most structural and functional aspects: the apical membrane is enfolded, forms a canalicular system and contains V-H+-ATPase that assembles upon stimulation with the hormone serotonin (5-HT); Na,K-ATPase is localized in the basolateral membrane; septate junctions are not prominent, as deduced from immunofluorescence staining for the marker proteins discs large and fasciclin III. 5-HT elicits, at low concentrations, cytoplasmic [Ca2+] oscillations, and, at saturating concentrations, a tonic [Ca2+] rise. The following, so-called “re-absorptive” segment loops through the coiled secretory portion of the salivary gland. The apical membrane of the re-absorptive cells is not enfolded, and septate junctions are prominent. V-H+-ATPase and Na,K-ATPase reside on the apical and basolateral membranes, respectively. Finally, re-absorptive cells are also sensitive to 5-HT; however, whereas V-ATPase assembly has a 5-HT concentration dependence similar to other segments, the Ca2+ response occurs only at higher 5-HT concentrations, and displays a different kinetic pattern. 相似文献
157.
158.
This study examined p27 expression in a cohort of salivary malignancies (n = 74) for a prolonged period (20 years). Reduction of p27 expression was found to be a most powerful predictor for poor survival
and more so when the tumor concurrently expressed high levels of p53, TUNEL and heparanase markers, dramatically dropping
the patient survival probability to 0! While no patient whose tumor-staining profile included: p27 > 50%, p53 = 0, TUNEL = 0
and heparanase = 0, died of the disease during the 20-year follow up, the median of survival of the group with p27 ≤ 50%,
p53 > 0, TUNEL > 0 and heparanase > 0 was only 39 months. The survival probabilities of these two groups at 5 years were 100
and 50%, respectively, and at 20 years they were 100 and 0%, respectively (P = 0.05). Significant p27 reduction also resulted in significantly larger tumor size (T value), higher spread of neck metastasis and extra capsular spread and in more advanced disease (higher stage). Significant
correlation rates were found between age and poor survival, age and reduced p27 expression, and reduced p27 expression and
other general co-existing malignancies, indicating p27 reduction as part of a general phenomenon—age related mutagenesis.
Significantly more extensive therapy applied to patients with salivary reduced-p27 tumors could not prevent the rise in mortality
rate, questioning the justification for extensive therapy which is naturally accompanied by higher morbidity. Additional therapeutic
tools for fighting salivary cancer, possibly based on the new understanding of the p27, p53, TUNEL and heparanase carcinogenic
network, are necessary. 相似文献
159.
Attilio Pingitore Erika Cione Valentina Senatore Giuseppe Genchi 《Journal of bioenergetics and biomembranes》2009,41(3):215-221
This study was undertaken to better understand the physiological role of the retinoylation process in steroidogenic tissues.
In adrenal gland mitochondria, the retinoylation extent was found equal to that of testes mitochondria but without ATP in
the incubation buffer. We pointed out that the endogenous mitochondrial ATP in adrenal glands is much higher than in testes,
about 1.3 x 10−2 M and 5.2 x 10−8 M, respectively. In addition, less CoASH is required for the maximal acylation activity of the retinoyl moiety to protein(s)
compared to testes. The fatty acid analysis revealed a different composition of mitochondrial membranes of these two tissues.
Among the different values of fatty acids, it is important to note that adrenal glands contain a much higher amount of C18:0
and a much lower amount of C22:5 ω6 and C22:6 ω3 than testes in the mitochondrial membranes. In addition, there were also
differences in arachidonic acid (ARA, C20:4 ω6) content between adrenal glands and testes mitochondria. These different values
in the fatty acids composition should explain the different extent of the retinoylation process between the two organs. 相似文献
160.
Scent marking is widespread among individuals of Mammalia species, especially in resource defence social systems. Apart from
urine and faeces that are used for claiming resource ownership, specialised scent glands are the main source of secretions
in scent marking individuals. Most previous studies have described secretory epithelia macroscopically, since many glands
are conspicuous. But macroscopically inconspicuous scent glands or morphological structures might then be overlooked. In Saccopteryx bilineata (greater sac-winged bat), behavioural observations suggest that both sexes have, apart from the conspicuous gular glands
of males, specialised facial glands to display territorial marking. We investigated the facial glands of two males and one
female S. bilineata histologically and found, first, that both sexes possess a bilateral symmetrically intermandibular gland, which is composed
of a bed of modified apocrine sudoriferous cells. Second, we found lip glands consisting of modified apocrine sudoriferous
cell units with pigmented ducts around the upper and the lower lip. Both gland types are probably involved during territorial
marking. 相似文献